Raj Ambasana K1120910
1 Omer, Joshua R
School of Science, Engineering and
Computing BEng Civil Engineering
Level 6
Research: Underground Box Structure
Supervisor: Dr. Joshua Omer
May 2014
Raj Ambasana
K1120910

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2 Omer, Joshua R
CONTENTS
ABSTRACT........................................................................................................................... 5
ACKNOWLEDGEMENT........................................................................................................ 5
BACKGROUND .................................................................................................................... 6
OBJECTIVES ....................................................................................................................... 6
METHODOLOGY.................................................................................................................. 6
DATA COLLECTION............................................................................................................. 8
DIAPHRAGM WALLS ....................................................................................................... 8
OTHER TYPES OF RETAINNING WALLS ....................................................................... 9
CONSTRUCTION OF THESE WALLS........................................................................ 10
CHALLENGES IN UNDERGROUND BOX STRUCTURE................................................... 12
GROUND WATER LEVELS............................................................................................ 12
OTHER CHALLANGES................................................................................................... 13
STRUCTURES AROUND THE SITE .............................................................................. 14
CATALOGUE...................................................................................................................... 15
SITE VISIT AT BOND STREET STATION.......................................................................... 17
PICTURES TAKEN AT THE SITE VISIT......................................................................... 19
METHODS OF CONSTRUCTING UNDERGROUND BOX STRUCTURE .......................... 20
BOTTOM-UP CONSTRUCTION..................................................................................... 20
TOP-DOWN CONSTRUCTION....................................................................................... 21
CONSTRUCTION METHOD USED BY PROJECTS OVERLOOKED ............................. 22
CONSTRAINS .................................................................................................................... 23
PROPOSAL TO BUILD AN UNDERGROUND BOX STRUCTURE BASEMENT ................ 24
LOCATION...................................................................................................................... 25
ABOUT THE PROPERTY ............................................................................................... 29
GEOLOGY..................................................................................................................... 29
PROPOSED DESIGN ..................................................................................................... 32
CHOOSING THE TYPE OF CONSTRUCTION METHOD............................................... 32
WALLING SYSTEM ........................................................................................................ 33
METHOD STATEMENT.................................................................................................. 34
ANALYSIS ...................................................................................................................... 34
RETAINING WALLS.................................................................................................... 35
VERIFY THE TOTAL STRESS ON THE RETAINING SIDE OF WALL ........................... 37

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BASEMENT UPLIFT ....................................................................................................... 42
PROBLEMS.................................................................................................................... 48
SOME REASONING OF THE APPLICATIONS............................................................... 48
DISCUSSION...................................................................................................................... 49
CONCLUSION.................................................................................................................... 50
REFERENCES ................................................................................................................... 51
APPENDIX.......................................................................................................................... 53
BOREHOLE LOG............................................................................................................ 54
POINT 1..................................................................................................................... 54
POINT 2...................................................................................................................... 56
EMBEDDED CANTILEVER WALL VERIFICATION OF STRENGTH .............................. 58
BASEMENT UPLIFT ....................................................................................................... 64
AUTOCAD DRAWING 1 ................................................................................................. 70
AUTOCAD DRAWING 2 ................................................................................................. 71

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TABLE OF FIGURES
Figure 1 Box structure of Paddington station (Crossrail, 2011).............................................. 7
Figure 2: The installation process of Diaphragm Walls (accessed 18/10/2013), Diaphragm
walls (technique), Bachy Soletanche) ................................................................................. 10
Figure 3: 3nr reverse-circulation hydraulic Bauer Hydromills used at Stratford CTRL Stratford
Box Contract 230, 2010) ..................................................................................................... 10
Figure 4 Hydraulic sheet piling machine (Dcpuk.com, 2014)............................................... 11
Figure 5: Steel stanchion reinforcement tendion pile (Drake and Jackson et al., 1999, p. 49)
........................................................................................................................................... 13
Figure 7: Cross section of Canary Wharf Station................................................................. 15
Figure 6: Stratford box half completed with diaphram walls................................................. 15
Figure 8: Paddington Station - architects impression........................................................... 15
Figure 9 Tottenham Court Road - architects impression of western ticket hall .................... 16
Figure 10: Diaphragm walling to the east of the site............................................................ 16
Figure 11 3D Architectural drawing ..................................................................................... 16
Figure 12 Locations of listed buildings from : (Sue McElroy (CEng), 2014, PowerPoint
slides) ................................................................................................................................. 18
Figure 13 Site visit .............................................................................................................. 19
Figure 14 Site visit .............................................................................................................. 19
Figure 15 Site visit .............................................................................................................. 19
Figure 16 Site visit .............................................................................................................. 19
Figure 17 Procedure of Bottom up construction (Transportation, 2009) ............................. 20
Figure 18 Procedure of Top down construction (Transportation, 2009) ............................... 21
Figure 19: Proposed property.............................................................................................. 24
Figure 20 Location of the site. Google maps (accessed 29/3/2014) .................................... 25
Figure 22 Mepham Crescent (taken by Raj Ambasana)...................................................... 26
Figure 21 Mepham Gardens (taken by Raj Ambasana)....................................................... 26
Figure 24 Langton Road (taken by Raj Ambasana)............................................................. 27
Figure 23 Langton Road (taken by Raj Ambasana)............................................................. 27
Figure 25 Mapped location of the site. Google maps (accessed 29/3/2014)........................ 28
Figure 26Photo of the metal vertical supporting for the column (Taken by Raj Ambasana) . 29
Figure 27Photo of the loft (Taken by Raj Ambasana).......................................................... 29
Figure 29 Borehole at point one.......................................................................................... 30
Figure 28 Borehole at point two .......................................................................................... 30
Figure 30 Sited of the borewhole (British Geological Survey (accessed 31/03/2014))......... 31
Figure 31 Cantilever embedded wall (hand drawn by Raj Ambasana) ................................ 36
Figure 32 Technical detail drawing of retainning wall .......................................................... 36
Figure 33 Soil Layout .......................................................................................................... 36
Figure 34 Limite state consiquences. (Bond and Harris, 2008, pg 401)............................... 48

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ABSTRACT
Underground box structures are now common solution used by engineers to build large
structures underground. However there is a small part of information which is published on
this area were certain projects that incorporate box structures in their design and structure
that have been built are mentioned, therefore making it very difficult to find out projects that
have implemented the use of this box structure construction method. This causes difficulty in
finding out the appropriate method of construction for any Civil Engineer that is willing to
design and construct an underground box structure. Furthermore there is lack of knowledge
on weaknesses and strengths that are involved in particular type of construction methods
used to construct these box structures.
From this research, catalogue of projects that have implemented box structures will be
constructed from which further work will be carried out on some of them. By doing this,
Engineers will be able to access information with ease as it will be available in a single
document, making it simpler for them to design these box structures and this will be a great
way for less experienced engineer to understand and work on project that implement box
structures as underground structures is the next big industry.
ACKNOWLEDGEMENT
I would like to thank my supervisor, Dr. Joshua Omer who has helped understand and guide
me through the research of underground box structures, and has given me with different
ideas and information source that has provided me with sufficient and relevant information.
Special thanks to Professor Mike Hope for arranging the visit to Bond Street station. From
this visit, better insight to the topic was gained and also gave me the opportunity to talk with
qualified engineers who reinforce and proved points stated in this report. Additionally show
gratitude to Kingston University for all the services provided and information they have
available for me such as Learning Resource Centres (LRC) and electronic catalogues. Last
but not the least would like to thank Bhavesh Pisawadia for briefly talking to me about some
projects he has worked on from which inspiration of the proposed project came from.

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BACKGROUND
The earth seems smaller in highly developed areas and city centres, making it difficult to
build on and expand oncoming infrastructures. The ongoing growth of infrastructures like
train stations, city centres, multi-level car parks, road junctions and many more, a quick
solution had to be identified. The next best place is to build these structures is underground.
By using this box structure method, Engineers are now able to accommodate the growth of
the infrastructure and are able to construct underground.
Based on this report, heavy emphasis on transportation sector is given were extensive
research has been undertaken on underground box stations that have and are been
constructed at the moment.
The objectives below will be met through my research.
OBJECTIVES
1. To catalogue the various design methods in use for box structure.
2. To compare the merits / demerits of each method for given ground condition.
3. To evaluate a case study “Stratford international Station” in terms of technical,
economical, safety design features.
4. To select a typical documented case record and soil data and apply analysis to Euro
code 7 and compare with specifications of the actual case record.
METHODOLOGY
To achieve the objectives, the following means of information will be used:
 Newspaper articles
 Journals
 Case studies
 Site visits
 Geotechnical books

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This method of underground structure construction is commonly employed and preferred in
transportation projects as identified from research. The data looked at mostly are the train
station in London. As seen from the research, these box structures are normally chosen to
provide large amounts of space in the ground. As architecture, they normally prefer these
box structure constructions, as they are able to get maximum space which creates an open
plan view when they are designing the internal fittings and also helps in managing flow of
people. One example is the box structure construction for Westminster station on the
London jubilee line extension. It states “the deep box solution provided the architect with the
opportunity for a more satisfactory and spacious design for passenger movement” (Bailey
and Harris et al., 1999, pp. 37).
Hashash, (2010) refers this box structure as ‘cut-and-cover box structure’. However they are
also known as basements, caissons, retaining wall structure, sunken box (structures where
the precast box is hammered into the soil) and many more. In the research authors have
referred these box structures as station box. These box structures vary in type such as:
 Fully enclosed in the ground which can acts as a basement or car park.
 Two sided opened structure which is commonly used in the transportation industry
e.g. train station
This variation of design depends on the purpose of the structural box required for the job.
These boxes can also be staked on each other creating multi floor.
Diaphragm walls internal structure
Base slab
Deep
Soil pilling
Figure 1 Box structure of Paddington station (Crossrail, 2011)

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DATA COLLECTION
DIAPHRAGM WALLS
The walls of the structural box are often diaphragm walls. Engineers could also use bored
pile walls, sheet pile and many more which may act as permanent or temporary walls.
Diaphragm walls are commonly chosen by engineers as seen throughout the projects that
have come across in the research. Diaphragm walls can be used in most ground conditions
as they act as water barriers. Skanska is one of the well recognized companies involved in
many transportation projects where they have built these box structures such as: CTRL
Stratford box station, Crossrail Paddington station and many more. They stated that “they
are typically constructed in reinforced concrete to provide the required structural capacity,
but they may also be designed as unreinforced. Its role is to stop water flow through porous
strata. Diaphragm walls are typically 20m to 50m deep, but may extend to considerably
greater depth” (Diaphragm Walls, 2009). From projects that have been reviewed, the depth
of these box structures are between 12m to 27m. All depths stated in the case study vary
upon the length of the structure.
Bachy Soletanche Limited is one of the UK's leading geotechnical specialists within the field
of foundation and underground engineering who has also carried project work that includes
diaphragm walls. They stated that “Diaphragm walls provide rigid, cost effective solutions for
permanent retaining walls and shafts, with less construction joints than bored pile walls.
They are particularly suitable for large, more open sites where structures greater than 25m
deep are required.”(Diaphragm walls (technique), 2013). Further on Skanska states that
“Diaphragm walls are often located in confined inner- city areas where space is at a
premium.” (Diaphragm Walls, 2009) which explains why engineers prefer diaphragm walls
especially when they are in the inner city centres such as Westminster Jubilee extension.
Through these resources it can be seen that the diaphragm walls play a great role in parts of
providing structural capacity and has desirable properties and method to build the walls. The
box structure provides support with the temporary work when constructing this underground
structure as a whole as seen in the construction of Westminster station(Glass and Stones,
2001, pp. 242-243) which means there will be reduction in temporary works required.
Diaphragm walls are constructed as permanent walls as seen in some of the projects, which
reduces the width of construction and working space required when compared to a solution
that has both a temporary ground support and permanent works within the work area. The

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ability to alteration the stiffness of the walls, giving a better resistant to deflection from the
ground and structural forces from above. It also explains why engineers prefer using
diaphragm walls as they are cost effective and faster to build reducing the overall cost of the
project, which is the first priority for the client, which is to complete the project at the lowest
cost.
On the other hand, depths more than 25m have not been exceeded in the projects been
seen, but yet engineers choose to use diaphragm walls which creates another major
question, why choose diaphragm walls instead of the other types of construction?
OTHER TYPES OF RETAINNING WALLS
These walls also can be constructed from sheet pilling which act as temporary support wall
that can be left when the construction is completes as done at Westminster station. On the
other hand, contiguous bored pile was used at St Pancras Thameslink station. The reason
was not stated in the report however through the assumption and information given by
companies who specialise in contiguous bored piles, prediction of choice can be assumed.
Skanska stated in its report on bored pile retaining walls (2008) “can be installed in restricted
work place, helps in controling of ground movements and groundwater, adoptable to
complex wall layout.” Some of this quoted advantages suit the reason of use of contiguous
bored pile for the project as the ground water stated at the site of St Pancras Thameslink
station was close to the existing ground level with a hydrostatic ground water profile to about
12m (Gates-Sumner and Chodorowski, 2007, pp. 41). The site also was in a well developed
area with restricted work place where special arrangements on the road layout had to be
made to accommodate construction vehicles coming in and out of the site work (Gates-
Sumner and Chodorowski, 2007, pp. 41).
In Skanska’s information report of bored pile retaining walls (2008) they state different types
of bored piles. The contiguous piles is said to be suitable for area where retaining soil is
usually firm to stiff and where ground water table is below the level of maximum excavation
(Bored pile retaining walls, 2008). This raised question on why engineers used contiguous
bored pile retaining wall. However the report by Gates-Sumner, M. and Chodorowski, A.
(2007) states that beneath 12m AOD the level of ground water had been reduced due to
historical groundwater abstraction in the underlying chalk aquifer. That was a great judgment
carried out by engineers as stated by Skanska (2008) the most economic option and
normally the fastest method to construct.

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CONSTRUCTION OF THESE WALLS
To construct these walls the main
element is the technique and use of
machineries.
Normally in diaphragm wall
construction, the diaphragms walls
thickness sized excavation takes place
were bentonite powder mixed with
water suspension (slurry) is added to
support and stabilise the trench walls
during excavation (Diaphragm walls
(technique), 2013). This technique was
adopted by Bachy Soletanche from the drilling techniques employed by oil well engineers
and also is been widely used in most of the projects by other companies during the
excavation. Reinforced steel cages are lowered into this excavation and then filled with
concrete mix. These steps are shown as diagram in figure 2.
During the construction of the Stratford box station, Skanska used bentonite mud to support
the trench and an approximate of 12,500 tonne of reinforced steel cages supplied by
Express Reinforcement was used. (CTRL Stratford
Box Contract 230, 2010). The machineries used to
create the excavation also varied as the type of soil
changed e.g. at Stratford box station construction, for
the upper soft strata, Cementation Skanska opted for
the use of rope suspended and hydraulic grabs
mounted on modern hydraulic Liebherr bass units,
and for the Thanet sands which is difficult to
penetrate, therefore Cementation Skanska opted to mobilise 3nr reverse-circulation
hydraulic Bauer Hydromills as shown in figure 3 (CTRL Stratford Box Contract 230, 2010).
As for St Pancras Thameslink station, the use of contiguous bored piles leads to use of
different type of machinery to install them. The metal piles are normally hammered into the
ground. However on the site, being directly adjacent to residential housing and with the
condition to continue for 24 hours for 26 week so that the project could be completed on
Figure 2: The installation process of Diaphragm Walls (accessed
18/10/2013), Diaphragm walls (technique), Bachy Soletanche)
Figure 3: 3nr reverse-circulation hydraulic
Bauer Hydromills used at Stratford CTRL
Stratford Box Contract 230, 2010)

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time. No noise was to be created, therefore engineers had to have the roof of the box formed
first and also had hydraulic machineries to put the circular piles into the ground.
Sheet piles are also hammered into the ground
section by section with its ends interlocking to the
previous sheet pile. When considering
hammering the retaining wall into the ground, the
type of soil that the retaining wall is being
hammered into has to be considered. It would be
very hard to drive a pile into a hard soil and may
cause damage to the sheet pile itself or the
equipment which will increase the expenses.
Figure 4 Hydraulic sheet piling machine
(Dcpuk.com, 2014)

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CHALLENGES IN UNDERGROUND BOX STRUCTURE
It has always been a great challenge for engineers and contractors to construct these box
structures. Bailey and Harris (1999) state in the jubilee extension report “presents greater
challenge to the civil designers and contractors.” He also talks about the criteria’s bases on
accepting tender where they were looking for companies that would recognise the
complexity of construction and the severe constrains on sites. From this it shows that a lot
research has to be undertaken when taking up the task of constructing these box structures.
These challenges faced by engineers are mainly concerning the geology of the site and
structures that are present in the surrounding site area. However through the research, the
techniques proposed used by the engineers to overcome these problems were seen and it
was notice that the proposals were similar.
GROUND WATER LEVELS
The water level present at the site causes great concern on the amount of hydrostatic lift the
station box would experience. At the Stratford CTRL station box at Stratford, the engineers
faced the problems of rise in water level where the groundwater level was rising steadily
since 1959. The rate of water level increased but could not give a reliable forecast and until
1996 when the design of the CTRL began the water table of Stratford was close to the top of
the Thanet Sand which was approximately 35.7m below ground level (Whitaker, 2004, pp.
183-184). On the other hand when looking at the Canary wharf station on the jubilee line
extension, the hydrostatic uplift on the station can be as much as 200,000t depending on the
ground water levels (Drake and Jackson et al., 1999, p. 49).
The solutions proposed to overcome this problem were:
1. Fill (weighting the box down)
2. Tension piles (holding it down)
3. Dewatering (lowering the water table)
The engineers choose different Solution for the projects due to its situation. Engineers for
the Stratford box structure took the solution of dewatering were a couple of pumping wells
were incorporated into the design with it complying with the design standards followed in the
UK. The pumps and well was drilled and penetrated 30m into the chalk layer so that it could
dewater by pumping only as much water as necessary to under-drain the Thanet sand
(Whitaker, 2004, pp. 187). On the other hand at Canary Wharf, tension piles and weighing
the box down with its self weight and the mass on it was used as a solution. This is shown

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when Drake and Jackson et al (1999) state “The
hydrostatic uplift of the station box was resisted by the
mass of the structure with some soil overburden on top
and 163 steel stanchion reinforced concrete piles cast
into socket bored 9 to 10m into the chalk.” One of the
steel stanchion reinforcement is shown in figure 4.
Dewatering was also required in the Westminster
station, where the excavation laid fully within the water-
bearing Thames Gravel layer. In this case dewatering measures were necessary to be
undertaken. A series of dewatering wells had previously been installed across the site
together with large-capacity wells in the 3 m dia. pile bores. But the efficiency deteriorated as
excavation proceeded. However, additional well points were added to dewater below the
soffit level (Glass, P. and Stones, C. 2001).
OTHER CHALLANGES
When excavating at the site, items found in the ground could be surprising. One of the
examples is at the St Pancras Thameslink Station site were several stages of development
during the last 200 years was found where left behind buried foundations, backfilled brick
viaducts and deep redundant gas holder tanks were found on the east side of the site. The
old St Pancras Church graveyard containing many remains lies at the northern end of the
site. Natural buried features at the site include the course of the original Fleet River. (Gates-
Sumner and Chodorowski, 2007, pp.41). From this engineers would have been cautious
when designing as the soil may have lost its strength or items found similar to the above
mentioned case study could significantly alter the strength of the soil.
Before constructing detailed site investigation and history of site has to be taken in place so
that structure within the site are not affected. Also find out if these structures are relying on
the existing foundations and structures underneath. As seen in one of the case studies at the
Westminster station, an eight-storey building occupied three of the four faces of the site. In
northeast and southwest of the site, buildings were supported across the underground tracks
by fabricated plate girders which had deteriorated badly over the years. The Palace
Chambers offices on Bridge Street had already had the top three storeys removed for this
reason. The building on the west face had been dismantled in the 1970s, leaving only the
basements behind. (Glass and Stones, 2001, pp. 239). If this investigation wasn’t carried out
Figure 5: Steel stanchion reinforcement tendion
pile (Drake and Jackson et al., 1999, p. 49)

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it would turn into a catastrophic accident were exciting structures may fall down killing
hundreds.
Plenty of work has to be carried out before the actual construction of the box structure could
begin. Some of these are to diverting gas mains, sewage pipe, water mains and also existing
train tracks.
STRUCTURES AROUND THE SITE
There is great concern when there are structures around the existing site especially if they
are of high value like the situation faced by the engineers during the construction of
Westminster station. As stated by Glass and Stones (2001) ‘the major challenge to the
construction team included movement control of adjacent structures such as St Stephaen’s
Clock Tower (Big Ben).” Further on Bailey and Harris et al, (1999) state that the predicted
total movement of big bang clock tower was a tilt to the north of approximately 1:2000. To
avoid this, the contractors included limited movement criteria on the deflection profile of the
diaphragm walls, settlement of piles and tilt and damage limits on existing buildings, utilities
and railway track (Glass and Stones, 2001, pp. 239). The tilt in tower was monitored by an
optical plumb which is shown in graph 1.
From the graph maximum
movement was during the
initial excavation but by
placing grouting the
movement was reduced. A
total of 24 separate
episodes of grouting were
undertaken specially to
control the tilt of the clock
tower between February
1996 and the end of deep
level excavation in September 1997.
Some of the projects included listed structure which means that the building has been placed
on the Statutory List of Buildings of Special Architectural or Historic Interest (Anon, 2013).
Canary Wharf had the North wall oh Heron Quays which caused problems for the onsite
facilities which were placed on barges and further work had to be carried out like placing a
Graph 1: Measured tilt of the Big Ben clock (Bailey and Harris et al,
(1999))

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protection pile as shown in figure 6 so that the structure cannot be damaged. (Drake and
Jackson et al., 1999, p. 47 –55)
CATALOGUE
These are some of the projects that have implemented the use of box structure
 Stratford Box station
Stratford box when the project was half
completed where the diaphragm walls are
visible. (CTRL Stratford Box Contract 230,
2010).
 St Pancras Thameslink Station
 Canary Wharf Station
Figure 7: Cross section of Canary Wharf Station
Cross section showing dimensions in mm
(Drake and Jackson et al., 1999, p. 49)
 Paddington Station
Architects impression of Crossrail
Paddington Station, sitting beneath
Eastbourne Terrace (cross rail
(accessed 16/12/2013).
Figure 8: Paddington Station - architects impression
Figure 6: Stratford box half completed with
diaphragm walls

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 Tottenham Court Road Crossrail Station
Figure 9 Tottenham Court Road -
architects impression of western ticket
hall
Architects impression image
showing cross-section view of
Crossrail Tottenham Court Road
Western ticket hall station at Dean
Street (cross rail (accessed
16/12/2013).
 Westminster station
Extremely old picture of work on site
(Glass and Stones, 2001, pp. 242)
 Woolwich Station
 Whitechapel Station
 Liverpool Street Station
 Bond Street Station
(Sue McElroy (CEng), 2014,
PowerPoint slides)
Figure 10: Diaphragm walling to the east of the site
Figure 11 3D Architectural drawing

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SITE VISIT AT BOND STREET STATION
A visit on 5th
march 2014 to one of ongoing projects by Cross rail at Bond Street revealed
more information about the projects, method of construction and constrains been faced. The
team of engineer present at the time were:
Sue McElroy CEng, Deputy Engineering Manager - Bond St Station.
Hugo Axel-Berg – Engineering Manager
Juliet Abbah – Asset Protection Engineer
Hannah Stotter – Assistant Engineering Manager
Sandy Webster – Eastern Ticket Hall (ETH) Site Manager
Will Sharp – Assistant ETH Site Manager
Sue McElroy – Host and Project Manager
Due to health and safety, the site was viewed from a viewing platform. Unable to go into the
site and having completed forty percentage of the construction work, the diaphragm wall
were unable to be seen as slabs for the floors were already been casted covering most of
the surface. Only part of the site was seen as shown in figures 13-16. At the time of visit the
TBM tunnel boring machine were already been lowered into the box station and already had
started tunnelling through. During the presentation Sue McElroy (CEng) and her team gave
out informed and brief walk through of the project. This project consisted of pile walling and
majority was diaphragm walls. It was a top down method of construction as this was a more
cost effective solution as stated by Hugo Axel-Berg – Engineering Manager. Some of the
major problems tackled during the construction were:
 Existing services: services like electric, water mains and much more. Relocation
and diverting these services was required while planning of the excavation of the box
station and the route of the TBM borehole machine was carried out. During the TBM
rout planning; the presents of exciting underground service tunnels were come
across. Taking in advantage of this, the horizontal gradients was taken to advantage
and by considering a more efficient run for the trains could be provided. For
example, the tunnel was brought more towards the ground level allowing the train to
stop when approaching the station and as the train exited the station, the tunnel
seemed to go away from the surface helping the train gain momentum due to gravity
therefore using less energy to get it moving.

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 Settlement of exciting structures: constant monitoring was required on exciting
structure were by around 4 total station constantly monitored structures that were
present around the site. Over 300 reflectors were been pinned onto the existing
structures walls, from which the total stations took readings on vertical and horizontal
deflections. Juliet Abbah and Hannah Stotter – Asset Protection Engineer who were
in charge of predicting the settlement said that there was a large amount of
settlement than usually expected from London clay soil. These movements would
cause problem to structure around the site. Problems like doors to move out of
alignment which make it hard or impossible to shut, cracking of parts of the structures
and much more.
 In addition there were listed building
around the site as shown in figure
11, therefore extreme precaution had
to be taken. To compensate the
movement of these structures.
Shafts were constructed at particular
locations around the box structure.
From these shafts, tubes were been
drilled under these affected
structures and grout was pumped into
these pipes with would lift and provide
support to the soil around it, therefore it will stop the structure from settling and
deflecting further more. These methods would encourage more settlement; however
it would stop further settlement from occurring as stated by Juliet Abbah. This
method was used in the Westminster jubilee extension when regarding the deflection
of the clock tower (Big Bang).
However the team presenting we're part of the project management team and therefore
during the personal interview they were unable to give out relevant information regarding the
project as there were subcontracts given out to different companies in regard of the
structural design, constructions and tunnelling.
However during the visit when having a discussion about publishing of journals on this
subject area with Sue McElroy, she stated that these journals take time to publish as great
reviewing is required before any information is put out. This was the same reasoning stated
Figure 12 Locations of listed buildings from : (Sue
McElroy (CEng), 2014, PowerPoint slides)

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by J.R.Omer. She also stated that projects of great important like project related to the
Olympic were published more quickly. This means that there may be many projects that
have implemented the box structure construction method but they being of less importance
they are not been published.
PICTURES TAKEN AT THE SITE VISIT
Figure 15 Site visit
Figure 14 Site visit
Figure 16 Site visit
Figure 13 Site visit

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METHODS OF CONSTRUCTING UNDERGROUND BOX STRUCTURE
There are two main types of methods that are used when constructing underground box
structure. From these there are few braches which go into a more detailed method. The two
main methods are:
BOTTOM-UP CONSTRUCTION
Figure 17 Procedure of Bottom up construction (Transportation, 2009)
In this method, chosen type of retailing walls are put into place. This help support the
excavation. From this the soil is excavated from the surface to the depth at which the
bottom of the structure would be placed. The structure is then completely constructed to the
surface and back filled is put at the top of the structure. The initial retaining walls can be
used as the final walls of a separate wall could be constructed.
Bottom-up construction offers several advantages:
 It is a conventional construction method well understood by contractors.
 Waterproofing can be applied to the outside surface of the structure prior to
construction.
 The inside of the excavation is easily accessible for the construction equipment and
the delivery, storage and placement of materials.
 Drainage systems can be installed outside the structure to channel water or divert it
away from the structure prior to the construction of the main build.
Disadvantages of bottom-up construction include:
 Somewhat larger footprint required for construction than for top-down construction.
 The ground surface cannot be restored to its final condition until construction is
complete.
 Requires temporary support or relocation of utilities.
 May require dewatering that could have adverse effects on surrounding
infrastructure.

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TOP-DOWN CONSTRUCTION
Figure 18 Procedure of Top down construction (Transportation, 2009)
With top-down construction the chosen type of structural walls are constructed first, usually
using slurry walls if diaphragm walls are chosen or secant pile walls can also used. In this
method the walls help support of excavation, and often is the final structural walls. Next the
roof is constructed and tied into the support of excavation walls. The surface is then
reinstated before the completion of the construction. The remainder of the excavation is
completed under the protection of the top slab. Upon the completion of the excavation, the
floor is completed and tied into the walls.
Top-down construction offers several advantages in comparison to bottom-up construction:
 It allows early restoration of the ground surface above the tunnel
 The temporary support of excavation walls are used as the permanent structural
walls
 The structural slabs will act as internal bracing for the support of excavation thus
reducing the amount of tie backs required
 It requires somewhat less width for the construction area
 Easier construction of roof since it can be cast on prepared grade rather than using
bottom forms
 It may result in lower cost for the structure by the elimination of the separate, cast-in-
place concrete walls within the excavation and reducing the need for tie backs and
internal bracing
 It may result in shorter construction duration by overlapping construction activities

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Disadvantages of top-down construction include:
 Inability to install external waterproofing outside the structures walls.
 More complicated connections for the roof, floor and base slabs.
 Potential water leakage at the joints between the slabs and the walls
 Risks that the exterior walls (or centre columns) will exceed specified installation
tolerances and extend within the neat line of the interior space.
 Access to the excavation is limited to the portals or through shafts through the roof.
 Limited spaces for excavation and construction of the bottom slab
CONSTRUCTION METHOD USED BY PROJECTS OVERLOOKED
All of the projects in the case study have used the top down construction method. One of the
major reasons of this choice is because the excavation is very deep. Furthermore Hugo
Axel-Berg – Engineering Manager at Bond Street stated that “this is the cheapest method.”
Other engineers from the articles also have stated similar views but haven’t gone into detail
in this subject area.

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CONSTRAINS
When carrying out this project, there were many factors that restricted in expanding on
report. Some of these were:
Companies: Companies that were part of the projects that have been overlooked are not
willing to provide information. Companies like Arup were contacted through telephones and
emails, requesting them to send structural and geotechnical calculations carried out by the
engineers prior to the construction of the box structure. Some of the companies replied with
a denial to provide this information and some of these companies did not reply back at all. It
was mentioned that the information was only going to be used in comparing calculations that
were going to be carried out in the project.
Journals and news articles: there are not many journals that are published in this subject
area. Some reports found were not highly informative and were mainly based towards a
common man’s reading. It is very important in choosing the right journal for the report as
assumption would have to be made based on the finding and information within these
journals.
Engineers: engineers met during the site visits were specialised in particular sectors of the
project were by the information provided was not relevant for the project or was very basic
knowledge. One of the examples was the interview with Sue McElroy (CEng) who was part
of the organisation team. She had basic knowledge of the procedure of construction but she
did not have in depth and precise knowledge on this subject area.
Objective: Unable to retain any information from the companies regarding the projects they
have carried out, the objective number four had to be altered.
To select a typical documented case record and soil data and apply analysis to Euro
code 7 and compare with specifications of the actual case record.
To
To carry out an underground box structure calculation based around Eurocode 7

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PROPOSAL TO BUILD AN UNDERGROUND BOX STRUCTURE
BASEMENT
Figure 19: Proposed property
This property is located in borough of Harrow. It is a semidetached two floor house located in
a residential area consisting of the same type of houses. These houses were constructed in
the 1950 for the army and their families during the war period. It is a steel framed building
which is a quick and easy method of construction. This was one of the best ways to
construct homes in that period as houses used to get bombed and destroyed due to the war.
Even after explosions, parts of the building used to stay up from which they used to be
reconstructed again. In the later period, after the war was over these properties belonged to
the council and later in the stage they had been sold to the public.
Inspiration to propose an underground box structure for a property came from a project
heard from Bhavesh Pisawadia. He was part of the electrical installation team for the project.
This project had constructed an underground basement that ran under the entire property
boundary. To add, Palace of Westminster, adjacent to the Westminster station, new build of

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underground car park was carried out where the underground box structure method was
used, however that was a multi-storey car park. (Bailey and Harris et al., 1999, pp. 37).
LOCATION
The site is located in a residential area with it coming of an ‘A’ class road onto a two way
system road.
As entering into the residential area at Langton Road, the road becomes narrower with two
way road, but does not have any central dividing line. However cars of homeowners on that
street are parked on the roadside. Figures 23, 24 show this. As you go into Mepham
Gardens or Mepham Crescent, the roads are even narrower with cars parked on one side of
the road and just one lane for access. Usually garbage truck access this route therefore
trucks will be able to access at any time but causing blockages.
Excess to cars, LGVs, Rigid HGVs are easily accessible. Artic HGVs and PSV s are able to
access the site through the road but high skilled drivers and a separate route has to be
planned out. Mobile cranes would be able to access the sites but depending on the skills of
the drivers. Figure
SITE
Figure 20 Location of the site. Google maps (accessed 29/3/2014)

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Figure 22 Mepham Crescent (taken by Raj Ambasana)Figure 21 Mepham Gardens (taken by Raj Ambasana)

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Figure 24 Langton Road (taken by Raj Ambasana)Figure 23 Langton Road (taken by Raj Ambasana)

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SITE
Figure 25 Mapped location of the site. Google maps (accessed 29/3/2014)

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ABOUT THE PROPERTY
The foundation for this structure is a flat slab foundation with its entire structure been built
around a steel frame. Constructed in 1950, it has a 7 cm block outer wall, internal insulation
with timber stud work and finally plaster board. The entire structure is been supported by
steel columns running on the outer side of the structure and steel beams supporting the first
floor and the loft and roof. There are no internal supports with none of the internal wall being
load bearing.
To construct a basement for this structure, supporting the external walls is highly important
as live loads and dead loads within the structure are transferred to the foundation through
the columns within the outer walls as shown in figure 27.
Metal
columns
Metal
Beams
Figure 27Photo of the loft (Taken by Raj Ambasana)
Figure 26Photo of the metal vertical supporting for the column
(Taken by Raj Ambasana)

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GEOLOGY
Borehole logs of the site were obtained from the British Geological Survey website (11
March 2014). The points where boreholes were made are shown in the map image on figure
23. These were the only available public data for the site. Copy of the borehole records are
available in the appendix, however these reading were taken in 1994, therefore there may
be changes in the soil layout as there is a difference of ten years.
However when analysing the borehole logs, the soil type found is similar but the names
appearing in the reports are different. This difference may be due to the naming system used
during those days may be different, the procedure to test and identify may be different and
procedures may be less strict compared to the procedure used these days. Due to time
constrains we were unable to carry out boreholes at the site, assumption based on these
finding would me made
Figure 29 Borehole at point one
For figure 28 the middle layer of soil is not indefinable due to the handwriting on the borehole
log that has been handed in
For this case ground water level will be assumed lower than the excavation area as it hasn’t
been mentioned in the borehole logs. Therefore the entire soil sample is at undrained
condition
Figure 28 Borehole at point two

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Figure 30 Sited of the borehole (British Geological Survey (accessed 31/03/2014))

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PROPOSED DESIGN
AutoCAD drawing attached in the appendix show the proposed designs.
Seen from the designs of other project mentioned in the catalogue, it can be said that no
internal wall may be required to support the roof slab of the basement. However being a
residential property, dividers for different section would be required by the client. Walls would
be constructed which will act as supporting walls.
Sustainable idea can be implemented into the build. Ventilation system has to be place to
make the area liveable, special lighting system like solar tubes or skylights can be used to
redirect the light into the structure. Furthermore less heat may be requires as the structure
could use the ground heat to heat up.
CHOOSING THE TYPE OF CONSTRUCTION METHOD
After looking at the advantages and disadvantages mention in the report above on method
of construction the following conclusion on the method of construction has been concluded.
For this construction a top down construction method is going to be chosen as there is an
existing structure on the site. Bottom up construction method is not possible as the site
cannot be excavated to the depth before placing the underground box structure as there is
an existing building.
For the top down method, during construction, temporary support of excavation walls are
used as the permanent structural walls therefore reducing the cost and time required to
construct the actual wall. Further on cost is reduced as less bracing and ties would be
required to support the structure as the top slab will act as an internal bracing to support the
wall from falling into the excavation.
However excess to the excavation is going to be very difficult in the top down construction
method but the choice is mainly taken due to the presents of a structure on the site. In this
case a lot of manual, hand hell tools and small machineries to excavate will be required.
While carrying out the project, site location and surroundings should be considered as it is a
residential area so noise pollution had to be kept at a minimal. When looking back to the
report by Gates-Sumner and Chodorowski (2007) on the St Pancras Thameslink station,
they face a similar type of problem where the site was next to a residential area. They opted
to place the roof first which acted as a noise shield. For the proposed project, top down

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construction in ideal in this situation were a roof slab of the underground box structure has to
be casted first. This therefore acts as a noise shield.
WALLING SYSTEM
For this project Bore pile retaining wall would be used as there is restricted space as there
are properties on both side of the proposed property. This choice was assumed based on
the advice given by Skanska which stated “These techniques are suitable for the provision of
deep basements, underground structures and motorway cuttings where working space is
limited or adjacent existing structures require restraint. They avoid excessive bulk excavation
and help to control ground movements.” From this, there will be limited ground movement
and less monitoring of the structure next to the site will be requires. However they also state
“Diaphragm walls are often located in confined inner-city areas where space is at a premium
(Anon, 07/10/09).” But being able to reduce ground movement is a great bonus for the bore
piles.
This question raise is “Why not use diaphragm wall for the build?” Although this construction
method may be very popular, diaphragm walls require a separate site to hold its slurry and
reprocess before it is used again. It is not practical at this situation as this proposal is a small
build compared to the large underground box structure seen in the case studies, diaphragm
wall cannot be used as space is unavailable at the site also to store the excavated material
and the slurry tanks. Further on Secant Wall–bore pile retaining wall system will be used
where Skanska (2008) stated that this method is an alternative to diaphragm wall
construction. Bore pile retaining wall construction method is also ideal as the depth of the
basement that is proposed is not too deep therefore a great amount of depth is not required.
If costing is considered bore pilling is cheaper as bored pile retaining wall require metal or in-
situ / precast concrete circular piles were drilling and hammering is used to place the piles.
For the diaphragm walls, separate site for the slurry processors are required and large
cranes and rigs are required to dig out the trench and lower the heavy reinforcing cages.
Additionally having a lot of plant in this confined space would be very difficult and hard to
manage.

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METHOD STATEMENT
 Ground investigation.
 Mark the area of the basement being constructed.
 Choose the type of retaining wall and construct them into their place creating a box
structure (take care of the existing foundations).
 Underpin exciting foundations.
 Start excavating the new basement.
 Construct the roof slab underneath the existing foundation.
 Start putting up temporary supports if required.
 Put in place the base slab.
 Construct internal permanent support walls.
This method statement was based around the guidance to convert a basement found in the
HOMEBUILDING & RENOVATING magazine. It also includes the general sequence of
construction stated by Glass, P. and Stones, C. (2001) in their report on construction of
Westminster station.
ANALYSIS
The analysis was based upon work done by Bond and Harris, (2008) in their book ‘Decoding
Eurocode 7’ which some of the working carried out by them is being followed and used to
carry out analysis of the proposed box structure. The calculations were calibrated based on
the answers and working out done in the examples making the outputs more reliable and
safe to consider when designing.
An excel program based on this has been created to help engineer carry out their calculation
by inputting the characteristics of the soil and dimensions of the proposed structure. This
makes it easier for the less experienced engineers to carry out analysis and is quicker in
getting results. This may help engineers to provide estimate cost of the project or also can
check if the proposed structure would be able to be constructed.
Furthermore, additional work such as constructing a program with the aid of visual basic
was going to be carried out however due to time constrain, and time required in inputting the
date to construct this program and testing it to real situations was not available therefore it
was not possible to build this program up. This program would make the inputting and
displaying of the results easier and simpler to visualise. The downside of programming in

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visual basics is that the equations used by the programmer are not seen making it hard for
the less experience engineers to figure out how values are inputted and analysed making
them rely on the answers given by the program. All programs have the same disadvantage,
they only show the input buttons and analysis buttons from which the answers are given out.
To help improve the efficiency of the program, highly skilled and well experienced computer,
geotechnical, structures and civil engineer have to be involved while testing the program as
they are able to estimate and find out if the answers are all right.
The calibration calculations are shown in the appendix.
RETAINING WALLS
Based on EN 1997-1 9.1.2.2 retaining walls is relatively thin structure whose bending
capacity plays significant role in the support of the retained material. From the Anex B.3 of
Eurocode 7 part 2 the depth of investigation points for retaining structures is given. The
recommended minimum depth of investigation= za > 0.4h and za > (t + 2m)
Za > 0.4 (4.3) = 1.72 m
Za > (t + 2m)
Bond and Harris (2008) state that ‘great depth of investigation may be needed for very large
or high complex projects or where unfavourable geological conditions are encountered.’ This
may be one of the major work taken under when planning and designing projects stated in
the catalogue. However in this case, the proposal is a very small project when comparing to
the projects seen in the catalogue. It can be said when referencing the Geology section of
this project that the depths already obtained from other companies show very deep depths
and seem to be relevant.
The following design analysis of the retaining wall was considered. This calculation is carried
out as the retaining wall will look like the drawing in figure 27 before the roof slab of the box
structure is laid down and the box shape constructed around. This calculation is to verify the
total stress on the retaining side of wall.
Some of the angles of friction used in the calculations were got off from Angle of Friction -
Geotechdata.info (2014). The maximum angle of friction was considered in this case.

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Figure 31 Cantilever embedded wall (hand drawn by Raj Ambasana)
For this proposal we are unable to get borehole logs of the particular site. However two
borehole logs were found that are fairly close to the site. Both were compared and an
average layout of the soil layers was assumed as shown in figure 27.
For the proposed deign the whole basement will be sitting on London clay layer with the bore
pile retaining wall being constructed in the London clay region only. Therefore calculation
based on this was carried out in the following page. This analysis is the verification of
strength on an embedded cantilever wall.
Figure 33 Soil Layout
Figure 32 Technical detail drawing of retaining wall

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VERIFY THE TOTAL STRESS ON THE
RETAINING SIDE OF WALL
Hnom = 4.5 m
characteristic variable surcharge qQK = 10 Kpa
dnom = 8 m
soil characteristics
soil notation
ϕk
(ᵒ)
c'k
(KPa)
ϕcv,k
(ᵒ)
cu
,k
clay (undrainned) ϒk2
2
0 KN/m^3 40
K
pa
unplanned over dig
∆H=min(10% x Hnom,0.5m) ∆H = 0.45 m
unplanned height of excavation
Hd=Hnom+∆H Hd = 4.95 m
Reduced depth of embedment
dd=dnom-∆H dd = 7.55 m
design embedded depth
dO,d= dd/1.2 dO,d = 6.29 m
embedment depth
dO,nom=dO,d + ∆H dO,nom = 6.74 m

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Vertical total stresses on retained side of wall
at top of sand σv,k1 σv,k1 0 KPa
at bottom of Sand σv,k2 ϒk1 x Hnom = σv,k2 = 90 KPa
at point O σv,k3 σv,k3+(ϒk2xdO,nom) = σv,k4 = 224.8 KPa
Vertical total stress on resistance side
at formation level σv,k4 σv,k5 = σv,k5 = 0 Kpa
at point 'O' σv,k5 σv,k5+((ϒk2xdO,d) = σv,k6 = 125.8 Kpa
Material Properties
partial factors from sets M1 = ϒϕ = 1
M2 1.25
ϒc = 1
1.4
desighn undrained strength cu,d cu,d=cu,k/ϒcu = cu,d = 40 Kpa
clay (undrainned) 28.6
Effects of actions
partial factors from sets A1 = ϒG = 1.35
A2 1
ϒQ = 1.5
1.3
Horizontal stress on retaining wall
at top σa,d1 σa,d1=(ϒG x (σv,k1 -2 x = σa,d1 = -93.0 Kpa

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cu,d) + ϒQ x qQK)
-44.1
at bottom σa,d2
σa,d2=(ϒG x (σv,k2 -2 x
cu,d) + ϒQ x qQK) = σa,d2 = 29 Kpa
45.9
at point 'O' σa,d3
σa,d3=(ϒG x (σv,k3 -2 x
cu,d) + ϒQ x qQK) = σa,d3 = 211 Kpa
180.7
Horizontal stress on resistance side of the wall
at formation level σp,d4
σp,d4= (ϒG x (σv,k4 +2 x
cu,d) = σp,d5 = 108 Kpa
57.1
at point 'O' σp,d5
σp,d5= (ϒG x (σv,k5 +2 x
cu,d) = σp,d6 =
277.8
75 KPa
183.0
Horizontal thrust
from
top
HEd1=(σa,d1 + σa,d2/2) x
Hnom = HEd1 =
-
144.0
KN/
m
3.9
bottom HEd1=(σa,d3) x dO,nom = HEd2 = 711.2
KN/
m
609.1
Total HEd sum HEdi = sum HEdi = 567.2
612.9
Overturning Moments about 'O'
MEd1=(σa,d1/2 x Hnom x ( 2/3 Hnom + dO,nom) MEd1 =
σa,d1/2 x Hnom x (2/3
Hnom + dO,nom) =
-
2038.
4
KNm
/m
-

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967.6
MEd2=(σa,d2/2 x Hnom x ( 1/3 Hnom + dO,nom) MEd2 =
σa,d2/2 x Hnom x (1/3
Hnom + dO,nom) = 537.8
KNm
/m
850.4
MEd3=(σa,d3/2 x dO,nom 1/3 dO,nom) MEd3 =
σa,d3/2 x dO,nom x
1/3dO,nom = 1598
KNm
/m
1368.
7
total MEd sum MEdi = 98
KNm
/m
1252
Resistance
Partial Factor from sets R1 : ϒRe = 1
R2 1
Horizontal Resistance HRd
((σp,d4 +σp,d5/2) x dO,d) /
ϒRe) HRd = 1214
KN/
m
755
restoring moment about point 'O'
MRd4=(σp,d4/2)xdO,dx(2/3dO,d)/ϒRe) MRd4 =
(σp,d4/2)xdO,dx(2/3dO,d)
/ϒRe) =
1425.
1
KNm
/m
754
MRd5=(σp,d5/2)xdO,d x (1/3dO,d)/ϒRe) MRd5 =
(σp,d5/2)xdO,dx(2/3dO,d
)/ϒRe) = 1833
KNm
/m
1207
total MRd sum MRd = 3258
KNm
/m
1961
Verification

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Rotational equilibrium MEd = 98
KN
m/m
1252
MRd = 3258
KN
m/m
1961
Degree of utilization ˄GEO,1=Med/MRd = 0.03 = 3.0 %
0.64 63.9
Design is unacceptable if the degree of utilization
is ˃ 100%
reaction near wall toe FEd HRd - Hed = 646.7
KN/
m
142.4
wall section must be designed for
Maximum bending moment =
Maximum shear force = 42.7
From the calculation the degree of utilization is >100% which is allowable, however when attempted to get closer to the 100% one or both the
values go out of the allowable range. Therefore the dimensions stated in the above working out are going to be used for the proposal. However
the negative stress and negative horizontal thrust will be countered by placing more reinforcement and when attached to the roof slab of the
box structure.

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BASEMENT UPLIFT
Verification of the uplift has to be considered as this may lead to damaging the entire structure. This is one of the major problems that
engineers faced in the projects stated in the catalogue.
one storey building
building weights
permanent wGk 30 kN/m2
variable qQk 15 kN/m2
basement spec
width B 6800 mm 680 cm 6.8 m
depth D 4500 mm 450 cm 4.5 m
walls tw 400 mm 40 cm 0.4 m
floors tf 250 mm
base slab tb 500 mm
weight density of concrete ϒck 25 KN/m3 (EN 1991-1-1)
ground profile
depth weight density
shear
resistance
(ϕK)
Superior angle of
share resistance:
(ϕK,sup)
Clay 20 m 19 KN/m3 15 22
ground water 9.81 KN/m3

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Actions
characteristic water pressure acting
underside of the basement
uk = ϒck x D
uk = 44.145 Kpa
destabilise action underneath the
basement
Ugk= uk x B
Ugk= 300186 KN/mm Ugk= 300.19 KN/m
characteristic action from the super
structure
Wgk,sup=Wgk x B]
Wgk ,sup (permanent) = 204000 KN/mm
Wgk ,sup
(perma
nent) = 204.00 KN/m
QQk,sup= qQk x B
QQk,sup (variable) = 102000 KN/mm
QQk,sup
(variabl
e) = 102.00 KN/m
characteristic self weight of the sub
structure (basement) is
from the wall WGk,w= 2 x tw x D x ϒck
WGk,w 90000000 N/mm = WGk,w 90.00 KN/m
from the floor WGk,f = tf x (B-2tf) x ϒck

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WGk,f = 39375000 N/mm = WGk,f = 39.38 KN/m
from the base slab WGk,b=tb x (B-2tf) x ϒck
WGk,b = 78750000 N/mm = WGk,b = 78.75 KN/m
from the weight WGk,sub=WGk,w + WGk,f +
WGk,b =
WGk,sub = 208125000
WGk,sub
= 208.13 KN/m
total self weight of the building is WGk =
WGk,sup+WGk,sub =
WGk, WGk, 412.13 KN/m
Effects of action
permanent partial factor on destabilizing
(ϒG,dst) 1.1
variable partial factor on destabilizing
(ϒQ,dst) 1.5
stabilized permanent action (ϒG,stb) 0.9
destabilizing vertical action
Vd,dst = ϒG,dst x Ugk Vd,dst = 330.2046 KN/m
Vd,stb = ϒG,stb x WGk Vd,stb = 370.9125 KN/m

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Material Properties
sand
Ka,k = 1-sin(ϕK)/1+sin(ϕK) 1-sin(ϕK) 0.74
1+sin(ϕK) 1.26
Ka,k Ka,k= 0.589
angle of wall friction δk = 2/3 x ϕk δk = 10.0 ᵒ
βk = Ka.k tan( δk) βk = 0.104
the partial factor of coefficient of shear
resistance ϒϕ 1.25
desighn angle of shear resistance ϕd= tan-
1(tan(ϕk)/ϒϕ) tan(ϕk) 0.27
(tan(ϕk)/ϒϕ) 0.21
ϕd ϕd= 12 ᵒ
active earth pressure coefficient Ka,d= 1-
sin(ϕd)/1+sin(ϕd) 1-sin(ϕd) 0.79
1+sin(ϕd) 1.21
Ka,d Ka,d= 0.653
angle of wall friction reduction δd = 2/3 x ϕd δd = 8.1 ᵒ
βd.inf = Ka.d tan( δd) βd.inf = 0.09
lower β should not be attended lower than
ϕK,sup 22
ϒϕ,sup = 1/ϒϕ 0.8
ϕd,sup = tan-1
(tan(ϕK,sup)/ϒK,sup tan(ϕK,sup) 0.40
(tan(ϕK,sup)/ϒK,s 0.51

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up
ϕd,sup ϕd,sup = 26.8 ᵒ
ka,d,sup=1-sin(ϕd,sup)/1+sin(ϕd,sup)
1-sin(ϕd,sup)
0.55
1+sin(ϕd,sup) 1.45
ka,d,sup ka,d,sup = 0.379
δd,sup = 2/3 x ϕd,sup δd,sup = 17.9 ᵒ
βd.sup = Ka.d.sub x (tan( δd.sub)) tan( δd.sub) 0.32
βd.sup βd.sup = 0.122
βd=min(βd.inf,βd.sup) βd= 0.093
Resistance
average vertical effective stress down the
basement wall
σ'v=(ϒk -ϒw)xD/2 σ'v= 20.7 kPa
characteristic resistance along the
basement wall
Rk=βk x (ϒk -ϒw)xD2
/2 Rk= 9.7 KN/m
desighn resistance along the basement wall
Rd=βd x (ϒk -ϒw)xD2
/2 Rd= 8.6 KN/m

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Verification of stability against uplift
Degree of utilization ᴧUPL =
Vd,dst/Vd,stb+Rd=100% 97.46 < 100%
The degree of utilization is close to 100% and less than 100% therefore the perimeters for the box structure are all right and no extra precaution
has to be taken toward the uplift of the building.

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PROBLEMS
The property is a semidetached property consequently the foundation will be shared
between the two properties, therefore consent from the neighbours would be required.
Further on limited underpinning of the neighbours properties foundation also would be
required as the foundation is shared and one of the internal walls also is shared.
There may be facilities that are passing under the properties like electric wired service lines
such as sewer. There defiantly is a waste pipe under the property this was known during the
removal of the sewage pipe that was inside the property, which running through the internal
walls.
Settlement of structures can be possible even though the method of construction chosen
limits the movement. Also this being a very small build would not cause a lot of movements
but monitoring is vital. As seen from the Bond street station, sometimes soils acts in a very
different and unpredictable way.
For the verification of strength on an embedded cantilever wall calculation, alteration to the
calibration calculation was carried out. This is when problem towards developing the
program came up. The change in the sequences of the soil causes a problem to the way the
equations are placed. This then changes the entire calculations an it’s structure. To
overcome this high skilled computer software engineers would be required.
SOME REASONING OF THE APPLICATIONS
Deep retaining walls were required in this case
as its limit states shown in figure 29 would be
avoided. However it would cost more but it is
important that the structure itself doesn’t have
any damages.
Furthermore this has to be considered as there
is a structure on top of the proposed design.
Thick walling is considered to avoid water
seepage into the structure as well. Water
proofing would also be carried out just in case
there is change in the water table.
Figure 34 Limit state consequences. (Bond and Harris,
2008, pg. 401)

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DISCUSSION
From the research, underground box structure is a fast and upcoming method of
construction that engineers are considering these days. This can be seen through the
projects listed in the catalogue were most of the projects that are mentioned are part of
ongoing projects or proposed designs. From the catalogue, Westminster station is the oldest
project that could be found. This means that it is a method of construction that was known
but wasn’t considered due to certain factors discuss later on. The theory behind the
designing and construction is constant however factors like the soil type, uplift condition,
surrounding environment and the water table vary the procedure to tackle the problem as
seen in the report above.
After working on the proposal, a lot of factor had to be considered before and during the
project planning period. The entire construction method has to be considered which was
gained from the Westminster station. Westminster station was the only project where the
journal gave an in depth fully expanded time to time event of the entire project. Based on this
research basic knowledge and procedures were gained from which parts of the method
statement on the proposal could be prepared.
When looking at projects that have constructed basements, there are many methods that
companies use to construct these basements such as extending the footing and then start to
excavate. This is the method used in the project which Bhavesh Pisawadia talked about. In
this case specialist licence people are required to carry out the construction. Based on the
discussion, this method takes a long time and a lot of supporting equipment’s were required.
Most of the work was carried out manually as the digging starts from inside the building with
no retaining walls placed from the beginning as done in the proposal.
When comparing to the procedures stated in the proposal, the proposal method statement
seem to be straight forward and simple with access to machinery. However the equipment
that will be used in this proposed project compare to what had been used in the previous
projects may make a difference in the time period, construction method and its procedure.
This was seen in the Westminster station project where special equipment was specially
built for a certain part of the construction. It was the 85 tonne diaphragm walling crane which
was built for the low head room conditions (Bailey and Harris et al, (1999)). When comparing
it to the recent technology were 3nr reverse-circulation hydraulic Bauer Hydromills were
used at Stratford CTRL Stratford Box Contract 230, 2010) and bentonite powder mixed with
water suspension (slurry) is added to support and stabilise the trench walls during

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excavation (Diaphragm walls (technique), 2013). This is one of the fastest construction
method used to construct the walling for the box structure.
CONCLUSION
Based on the research, the catalogue, methods of construction and visits shown, box
structures seem to be an easy method of construction and analyse from which engineers are
now able to access information at great ease with most of the information available in one
document. By achieving the objectives set at the beginning, it can be said that less
experienced engineer will now be able to understand and confidentially work on project that
implement box structures. Through the excel program, less experience engineer are able to
verify proposed dimensions instantly. However further work on inputting these equations into
a sophisticated program have to be done which would require high computing skill.
Further on, this method is definitely not a new method but engineers both experienced and
less experienced have less information, methodology and idea based on this subject area
from which they are unable and not confident to carry out the project. Through this research
they now are able to understand the procedures, the weaknesses and strengths of
construction method, factors affecting the build and engineers involved in the project. This
research has helped understand and has helped a little towards tackling the problem.
Through this document through the referencing, other documents stating experiences of
engineers could be found which could help understand this subject area. Box structures are
not only used for large scaled builds but can be used domestically as seen in the proposed
design.

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REFERENCES
 Angle of Friction - Geotechdata.info. 2014. [online] Geotechdata.info. Available at:
http://www.geotechdata.info/parameter/angle-of-friction.html [Accessed 6 Apr. 2014].
 Anon, (accessed 18/10/2013), Diaphragm walls (technique), Bachy Soletanche
 Anon, 14/05/2010, CTRL Stratford Box Contract 230, Skanska, Rev 4. Accessed
(25/09/2013).
 Anon. Available at : http://www.english-heritage.org.uk (accessed 16/12/2013)
 Anon (08/07/08), Bored Pile Retaining Walls, Skanska, Rev 1. Accessed (11/12/13).
 Architectsjournal.co.uk, (2011). The Regs: Foundations. [online] Available at:
http://www.architectsjournal.co.uk/specification/the-regs/the-regs-
foundations/8621391 .article [Accessed 11 Apr. 2014].
 Bailey, R., Harris, D. and Jenkins, M. 1999. Design and construction of Westminster
station on the Jubilee Line Extension. 132 (2), pp. 36--46.
 Bond, A. and Harris, A. 2008. Decoding Eurocode 7. London: Taylor & Francis.
 Crossrail, 2011, Paddington Station- Design, Available at:
http://www.crossrail.co.uk/route/stations/paddington/design (Accessed:
24/October/2013).
 Dcpuk.com, (2014). Silent Piling - Dawson Construction Plant Ltd. [online] Available
at: http://www.dcpuk.com/products-list-pushpullsheet.asp [Accessed 25 Apr. 2014].
 Drake, D., Jackson, M. and Doubell, C. 1999. Desighn and construction of Canary
Wharf station on the Jubilee Line Extension. Proceedings of the ICE - Civil
Engineering, Volume 132 (Issue 6), p. 47 –55.
 Diaphragm Walls (2009), Skanska Cementation, 07 October 2009, Rev 6, Pub No
1223248.
 Gates-Sumner, M. and Chodorowski, A. 2007. Channel Tunnel Rail Link section 2: St
Pancras Thameslink station. 160 (2), pp. 39--42.
 Glass, P. and Stones, C. 2001. Construction of Westminster Station, London.
Proceedings of the Institution of Civil Engineers-Structures and Buildings, 146 (3),
pp. 237--252.
 Geotechdata.info, (2014). Angle of Friction - Geotechdata.info. [online] Available at:
http://www.geotechdata.info/parameter/angle-of-friction.html [Accessed 17 Apr.
2014].
 Guidance to converting a basement, (issue: January 2008), HOMEBUILDING &
RENOVATING. Available at: http://www.homebuilding.co.uk/advice/existing-
homes/converting-basement/guide (accessed on 21/03/2014)

Raj Ambasana k1120910
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 nCE (New Civil Engineer) (2001). Flying start for Stratford box. 1 March.
 Sue McElroy (CEng), (2014, March 5th
), Welcome to bond street. [PowerPoint slides].
Presented at a cross Rail offices in Bond street, London
 The Regs: Foundations. 2011. [online] Architectsjournal.co.uk. Available at:
http://www.architectsjournal.co.uk/specification/the-regs/the-regs-
foundations/8621391.article [Accessed Apr. 2014].
 Transportation, U. S. D. O. 2009. Technical manual for design and construction of
road tunnels - civil. [S.l.]: Www Militarybookshop Co U.
 Whitaker, D. 2004. Groundwater control for the Stratford CTRL station box.
Proceedings of the ICE-Geotechnical Engineering, 157 (4), pp. 183--191.
 Y. M. A. Hashash, Karina Karina, Demetrious Koutsoftas and Nick O'Riordan (2010) '
Seismic Design Considerations for Underground Box Structures' Earth Retention
Conference 3, Proceedings of the 2010 Earth Retention. , August 1-4, 2010.
Bellevue, Washington, United States: American Society of Civil Engineers, pg. 620-
637.

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APPENDIX

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BOREHOLE LOG
POINT 1

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POINT 2

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EMBEDDED CANTILEVER WALL VERIFICATION OF STRENGTH
Hnom = 4 m
characteristic variable surcharge qQK = 10 kPa
dnom = 9.8 m
soil characteristics
soil notation
ϕk
(ᵒ)
c'k
(KPa)
ϕcv,k
(ᵒ)
cu,
k
sand ϒk1
1
8 KN/m3
36 0 32
clay (undrainned) ϒk2
2
0 KN/m3
40
kP
a
unplanned ‘over dig’
∆H=min(10% x Hnom,0.5m) ∆H = 0.4 m
unplanned height of excavation
Hd=Hnom+∆H Hd = 4.4 m
Reduced depth of embedment
dd=dnom-∆H dd = 9.4 m
design embedded depth
dO,d= dd/1.2 dO,d = 7.83 m
embedment depth
dO.nom=dO,d + ∆H do,nom = 8.23 m

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Actions
Vertical total stresses on retained side of
wall
at top of sand σv,k1 σv,k1 0 kPa
at bottom of Sand σv,k2 ϒk1 x Hnom = σv,k2 = 72 kPa
at top of clay σv,k3 σv,k2 = σv,k3 = 72 kPa
at point O σv,k4 σv,k3+(ϒk2xdO,nom) = σv,k4 = 236.7 kPa
Vertical total stress on resistance side
at formation level σv,k5 σv,k5 = σv,k5 = 0 kpa
at point 'O' σv,k6 σv,k5+((ϒk2xdO,d) = σv,k6 = 156.7 kpa
Material Properties
partial factors from sets M1 = ϒϕ = 1
M2 1.25
ϒcu = 1
1.4
Design angle of shearing resistance of ϕd=tan-1
(tan(ϕk)/ϒϕ) = ϕd = 36 ᵒ
sand 30.2
Design constant volume angle of shearing
resistance of sand ϕcv,d=tan-1(tan(ϕcv,k)/ϒϕ) = ϕcv,d = 32 ᵒ
26.6
for soil/steel interface k = 0.67
design angle of wall friction δd=k x ϕcv,d = δd = 21.3 deg
17.7

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design undrained strength cu,d cu,d=cu,k/ϒcu = cu,d = 40 kPa
clay (undrainned) 28.6
Effects of actions
partial factors from sets A1 = ϒG = 1.35
A2 1
ϒQ = 1.5
1.3
Active Earth pressure coeffs for Kaϒ = 0.22
sand 0.287
annex c of EN
1997-1
Kaq = 0.22
0.287
Horizontal stress on retaining wall
sand
at top σa,d1
σa,d1=(ϒG x Kaϒ x σv,k1 +
ϒQ x Kaq x qQK) = σa,d1 = 3.3 Kpa
3.7
at bottom σa,d2
σa,d2=(ϒG x Kaϒ x σv,k2 +
ϒQ x Kaq x qQK) = σa,d2 = 25 Kpa
24.4
clay (undrainned)
at top σa,d3
σa,d3=(ϒG x (σv,k3 -2 x cu,d) +
ϒQ x qQK) = σa,d3 = 4.2 KPa
27.9
at point 'O' σa,d4
σa,d4=(ϒG x (σv,k4 -2 x cu,d) +
ϒQ x qQK) = σa,d4 = 226.5 Kpa
192.5

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Horizontal stress on resistance side of the
wall
at formation level σp,d5 σp,d5= (ϒG x (σv,k5 +2 x cu,d) = σp,d5 = 108 Kpa
57.1
at point 'O' σp,d6 σp,d6= (ϒG x (σv,k6 +2 x cu,d) = σp,d6 = 319.5 KPa
213.8
Horizontal thrust
from
sand HEd1=(σa,d1 + σa,d2/2) x Hnom = HEd1 = 56.6 KN/m
56.3
clay (undrainned) HEd1=(σa,d3 + σa,d4/2) x dO,nom = HEd2 = 949.7 KN/m
907.2
Total HEd sum HEdi = sum HEdi = 1006.3
963.5
Overturning Moments about 'O'
MEd1=(σa,d1/2 x Hnom x ( 2/3 Hnom + dO,nom) MEd1 =
σa,d1/2 x Hnom x (2/3
Hnom + dO,nom) = 71.9
KNm/
m
81.3
MEd2=(σa,d2/2 x Hnom x ( 1/3 Hnom + dO,nom) MEd2 =
σa,d2/2 x Hnom x (1/3
Hnom + dO,nom) = 478.3
KNm/
m
466.8
MEd3=(σa,d3/2 x dO,nom x 2/3 dO,nom) MEd3 =
σa,d3/2 x dO,nom x 2/3
dO,nom = 94.9
KNm/
m
629.5
MEd4=(σa,d4/2 x dO,nom 1/3 dO,nom) MEd4 =
σa,d4/2 x dO,nom x 1/3
dO,nom = 2559
KNm/
m
2175.1

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total MEd sum MEdi = 3204
KNm/
m
3353
Resistance
Partial Factor from sets R1 : ϒRe = 1
R2 1
Horizontal Resistance HRd
((σp,d5 +σp,d6/2) x dO,d) /
ϒRe) HRd = 1674 KN/m
1061
restoring moment about point 'O'
MRd5=(σp,d5/2)xdO,d x (2/3 dO,d)/ϒre) MRd5 =
(σp,d5/2) x dO,d x (2/3
dO,d) / ϒRe) = 2209
KNm/
m
1169
MRd6=(σp,d6/2) x dO,d x (1/3 dO,d)/ϒRe) MRd6 =
(σp,d6/2) x dO,d x (1/3
dO,d) / ϒRe) = 3267
KNm/
m
2187
total MRd sum MRd = 5476
KNm/
m
3355
Verification
Rotational equilibrium MEd = 3204
KNm
/m
3353
MRd = 5476
KNm
/m
3355
Degree of utilization ˄GEO,1=Med/MRd = 0.59 = 58.6 %
1.00 100.0

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Design is unacceptable if the degree of
utilization is ˃ 100%
reaction near wall toe FEd HRd - Hed = 668.1
KN/
m
97.7
wall section must be designed for
Maximum bending moment =
Maximum shear force = 42.7

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BASEMENT UPLIFT
One storey building
building weights
permanent wGk 30
kN/m
2
variable qQk 15
kN/m
2
basement spec
width B 18000 mm 18 m
depth D 4500 mm 4.5 m
walls tw 400 mm
floors tf 250 mm
base slab tb 500 mm
weight density of concrete ϒck 25
KN/m
3
(EN
1991-1-1)
ground profile
depth
weight
density
shear resistance
(ϕK)
Superior angle
of share
resistance:
(ϕK,sup)
sand 20 m 19 KN/m3 38 45
ground water 9.81 KN/m3

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Actions
characteristic water pressure acting
underside of the basement
uk = ϒck x D
uk = 44.145 kPa
destabilise action underneath the
basement
Ugk= uk x B
Ugk= 794610
KN/m
m Ugk= 794.61 KN/m
characteristic action from the super
structure
Wgk,sup=Wgk x B
Wgk ,sup (permanent) = 540000
KN/m
m
Wgk ,sup (permanent)
= 540.00 KN/m
QQk,sup= qQk x B
QQk,sup (variable) = 270000
KN/m
m QQk,sup (variable) = 270.00 KN/m
characteristic self weight of the sub
structure (basement) is
from the wall WGk,w= 2 x tw x D x ϒck
WGk,w 90000000 N/mm = WGk,w 90.00 KN/m

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from the floor WGk,f = tf x (B-2tf) x ϒck
WGk,f = 109375000 N/mm = WGk,f = 109.38 KN/m
from the base slab WGk,b=tb x (B-2tf) x
ϒck
WGk,b = 218750000 N/mm = WGk,b = 218.75 KN/m
from the weight WGk,sub=WGk,w + WGk,f +
WGk,b =
WGk,sub = 418125000 WGk,sub = 418.13 KN/m
total self weight of the building is WGk =
WGk,sup+WGk,sub =
WGk WGk 958.13 KN/m
Effects of action
permanent partial factor on
destabilizing (ϒG,dst) 1.1
variable partial factor on destabilizing
(ϒQ,dst) 1.5
stabilized permanent action (ϒG,stb) 0.9
destabilizing vertical action
Vd,dst = ϒG,dst x Ugk Vd,dst = 874.071 KN/m
Vd,stb = ϒG,stb x WGk Vd,stb = 862.3125 KN/m

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Material Properties
sand
Ka,k = 1-sin(ϕK)/1+sin(ϕK) 1-sin(ϕK) 0.38
1+sin(ϕK) 1.62
Ka,k Ka,k= 0.238
angle of wall friction δk = 2/3 x ϕk δk = 25.3 ᵒ
βk = Ka.k tan( δk) βk = 0.113
the partial factor of coefficient of shear
resistance ϒϕ 1.25
desighn angle of shear resistance ϕd=
tan-1(tan(ϕk)/ϒϕ) tan(ϕk) 0.78
(tan(ϕk)/ϒϕ) 0.63
ϕd ϕd= 32 ᵒ
active earth pressure coefficient Ka,d=
1-sin(ϕd)/1+sin(ϕd) 1-sin(ϕd) 0.47
1+sin(ϕd) 1.53
Ka,d Ka,d= 0.307
angle of wall friction reduction δd = 2/3
x ϕd δd = 21.3 ᵒ
βd.inf = Ka.d tan( δd) βd.inf = 0.12
lower β should not be attended lower
than ϕK,sup 45
ϒϕ,sup = 1/ϒϕ 0.8

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ϕd,sup = tan-1(tan(ϕK,sup)/ϒK,sup tan(ϕK,sup) 1.00
(tan(ϕK,sup)/ϒK,sup 1.25
ϕd,sup ϕd,sup = 51.3 ᵒ
ka,d,sup=1-sin(ϕd,sup)/1+sin(ϕd,sup) 1-sin(ϕd,sup) 0.22
1+sin(ϕd,sup) 1.78
ka,d,sup ka,d,sup = 0.123
δd,sup = 2/3 x ϕd,sup δd,sup = 34.2 ᵒ
βd.sup = Ka.d.sub x (tan( δd.sub)) tan( δd.sub) 0.68
βd.sup βd.sup = 0.084
βd=min(βd.inf,βd.sup) βd= 0.084
Resistance
average vertical effective stress down
the basement wall
σ'v=(ϒk - ϒw) x D/2 σ'v= 20.7 kPa
characteristic resistance along the
basement wall
Rk=βk x (ϒk -ϒw)xD2
/2 Rk= 10.5 KN/m
desighn resistance along the basement
wall
Rd=βd x (ϒk -ϒw)xD2
/2 Rd= 7.8 KN/m

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Verification of stability against uplift
Degree of utilization ᴧUPL =
Vd,dst/Vd,stb+Rd=100% 99.12 < 100%
the desighn is unacceptable if the
degree of utilisation in >100%

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AUTOCAD DRAWING 1

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AUTOCAD DRAWING 2