Gwe paper material

BY: KEYUR J PANSARA
SUB: GROUND WATER ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING
(10-11-2017 Q-3 )c( , Q-4 (A)) (11-05-2015 orQ-4 (A))
Enlist methods of drilling tube well, explain any one
Drilling Methods for Tube Wells:
1. Percussion Boring Method: This method is suitable for the soft and fissured rock formations.
In purely soil formations this method gives very high working rate. This method consists in
breaking and pulverizing the subsoil material by series of repeated blows with a cutter made of
hard metal. The pulverized material mixes with water and it is then removed. Sometimes this
method is also called cable tool method. Boring can be done manually or mechanically. Bores as
big as 30 cm in diameter and over 200 to 300 m deep can be very conveniently drilled which
meet the normal requirement.
The blows are given by means of a plunger. The plunger consists of a hollow metal tube. A
cutter is fixed to the bottom end of the plunger by riveting or welding. A ball valve made of steel
is also provided at the bottom of the plunger. The valve is such that it allows slurry of pulverized
soil material in water to enter the plunger.
Once the slurry enters the plunger the valve closes and slurry is prevented from coming out.
Thus the valve has only one way action. Sometimes flap valve may also be provided in the
plunger. The purpose served is exactly the same as that of ball valve. The plunger can be
lowered and raised in two ways:
i. By rope system, and
ii. By rod system.
In rope system the upper end of the plunger is attached to a rope. The rope runs over a pulley.
The plunger is lifted up and released suddenly to give a blow. Rod system is similar in principle
to the rope system. Only difference is rod replaces the rope and consequently the rod operating
machinery is also changed. The disadvantage of rod system is, time is wasted in increasing or
decreasing the rod length. The rod length can be increased or decreased by screwing or
unscrewing small rod lengths.
The actual boring procedure by manual percussion method is as described below:
A pit is dug at the site where the tube well is to be sunk. The casing pipe with a cutter shoe is
inserted in the pit. A platform is clamped to the casing pipe. The platform is loaded by means of
locally available material filled in jute bags.
Over the casing pipe a tripod is erected and a pulley is fixed to it centrally. A rope runs over the
pulley. One end of the rope is attached to the plunger. The diameter of the plunger is slightly less
than the casing pipe (say by 6 cm). The arrangement is clear from Fig. 18.5.

BY: KEYUR J PANSARA
Before starting actual boring some
water is poured in the hole. As the
plunger gives blows during each blow
slurry gets into the plunger. Blows are
given repeatedly till the plunger is full
of slurry. The plunger is then taken out
and the slurry is removed by turning
plunger upside down. The plunger is
again lowered and the process repeated.
Thus the casing pipe goes on sinking.
When the length of casing pipe goes
below the ground level sufficiently,
additional pipe may be attached at the
top of the first pipe. In order to increase
working rate machine percussion, is
used.
The material coming out is inspected
carefully and a record is prepared, it is
called logging. From the well log
position of aquifers can be computed correctly. When the tube well casing pipe reaches a
predetermined depth the platform is removed and a pipe with strainers at the determined levels of
aquifers is lowered in the hole. After lowering it up to required depth the strainer pipe is
clamped. It gives support and prevents it from falling into the bottom of the hole. Then shrouding
is started. In the beginning about 60 cm length of shrouding is done. Then the pipe casing is
slowly removed by 30 cm.
Then again 30 cm of shrouding is done and again pipe casing is lifted by about 30 cm. Thus the
shrouding and pipe withdrawal is done slowly, successively and in small lifts of about 30 cm till
the whole pipe casing is withdrawn. The amount of material required for shrouding per 30 cm
length can be accurately calculated beforehand. It will depend naturally on the thickness of the
gravel pack. Normally thickness of the gravel pack varies between 7.5 cm to 25 cm. The
thickness of gravel pack should be such that it would not allow even finest particles to move.
Machine Percussion or Cable Tool Method: The machine used for tube well drilling is called a
drilling rig. The rig for cable tool method is a truck mounted assembly from consideration of
mobility and consists of a mast, a multiline hoist, a walking beam and an engine. Figure 18.6
shows the assembly. The string of tools includes drill bit, drill stem, drilling jars which serve as
connecting links and rope socket for connecting drill line. Figure 18.7 shows components of
drilling tool. Total weight of the tool varies from 100 to 2000 kg. because different types of bits
are required for different rock formations. Length of drill bit varies from 1 to 3 m whereas drill
stem is 2 to 10 m long.

BY: KEYUR J PANSARA
The operation in principle is similar
to manual method. The cable tool bit
acts as a crusher for drilling in
consolidated rocks. The drilling is
performed by repeated blows of the
drilling tool which makes about 40 to
60 strokes in one minute. The drill
line is rotated so that a round hole is
drilled. As in the manual method
water is added to the bore to form the
slurry if the same is not present in
the subsoil formation. After the bore
is drilled by 1.25 to 1.5 m the drilling
tool is removed and the slurry is
taken out of the hole by means of
sand pump or bailer.
The bailer has one way valve which permits slurry to enter
the bailer but does not allow to escape. After the bailer is
filled it is raised and emptied at surface. The length of the
bailer also ranges from 3 to 12 m. In unconsolidated
formations the well casing is inserted and simultaneously
sunk to full depth to avoid caving in of the material. The
rate of drilling depends on the type of sub-soil formation
met with, diameter of the well and the depth of hole
mainly. In solid crystalline rock formations the drilling rate
could be as low as 2 to 3 m per day.
Drilling rate in loose flowing fine sand formations is
equally low because it fills the hole as soon as material is
bailed out. To check the sand inflow the hole can be kept
filled with water. Drilling in unconsolidated formation with
bouldere is quite difficult because the boulders not only
deflect the hole but they are hard to drill and prevent sinking of well casing. In soft formations
like sand stone or sandy clay, the drilling rate could be as high as 20 to 30 m per day. The bore is
carefully logged to ascertain the position of various types of formations met with.

BY: KEYUR J PANSARA
2. Rotary Boring Method:
Hydraulic Rotary Boring Method:
This method is generally called rotary boring method. This method can be successfully used for
rock as well as unconsolidated formation. The method is therefore used for water well as well as
oil well drilling. Oil wells are generally very deep and this method is well suited for them
because unlike other methods the drilling rate is not dependent on the depth of the hole.
In this method drilling is done by means of rotating bits attached to lower end of hallow steel
pipe. The steel pipe is attached to a square section of a steel rod at the top which is called kelly.
Kelly fits in a rotating table at the surface. The rotating table is rotated by power. The powdered
rock and cuttings are removed by continuous circulation of drilling fluid.
The hydraulic rotary drilling rig consists of a derrick or mast, a rotating table, a pump for
injecting drilling mud, a hoist and an engine. The drill pipes are seamless steel tubings generally
available in 6 m lengths. The external diameter of the pipes ranges from 6 to 12 cm.
Generally adequate size of pipe is used because well drilling requires large quantity of drilling
fluid in circulation. The drilling bits attached to the lower end of the drill pipe is provided with
short nozzles to direct the jets of drilling fluid down the faces of the blades of drilling bit. Figure
18.8 shows schematic diagram of rotary boring method.
The rotating table in which the kelly fits in closely
turns the drill. The drilling bit cuts through the
formation and as the hole deepens the drill rod slides
down. At this stage the kelly is unfastened and pulled
up to attach new length of pipe. The drilling fluid or
bentonite (clay) slurry is pumped down through the
drill pipe and out through the nozzles in the bit. The
mud then rises to the surface through the annular
space between drill pipe and the bore and removes the
rock fragments and cuttings with it.

BY: KEYUR J PANSARA
The drilling fluid performs following functions:
(i) It supports the walls of the bore and prevents caving.
(ii) It removes cuttings from the bore hole.
(iii) It checks the inflow of groundwater into the well while drilling is in progress.
(iv) It cools the bit and lubricates the drill stem.
(v) It prevents the cuttings from settling down on the bottom of the bore.
(vi) It softens the underground formation and speeds up drilling.
Since there is likelihood that the drilling mud may seal low pressure water bearing formations it
is necessary to control quantity of mud in the water. Once the drilling fluid comes to the surface,
it is taken in a settling pit where rock fragments settle down. The cleaned fluid is re-circulated
through the hole.
As boring progresses detailed logging of the subsurface formations met with is done. After the
well is drilled to required depth a well pipe with strainer and blind lengths of determined sizes is
lowered. Since the bore walls are coated with colloidal mixture of bentonite it becomes
necessary to wash the walls.
It is called back-washing. For back-washing drill pipe with a collar of the size of the well pipe
attached above the drill bit is again inserted. The pump forces the water containing calgon
(sodium hexa-meta-phosphate) down the drill pipe.
The water rushes through the strainers and the calgon disperses the clay colloids deposited on the
bore walls. To increase efficiency of back-wash the drill pipe is moved up and down to create
surging action. The drilling rate by this method depends on type of subsurface formation
penetrated and type of rig equipment used. Contrary to the cable tool method the rate of drilling
by hydraulic rotary method does not depend upon the depth of the hole.
The rate of drilling in consolidated rock formations may vary from 10 to 15 m per day whereas
in un-consolidated formations it may reach 100 to 150 m per day.
The main advantages of hydraulic rotary method are the following:
(i) The drilling can go on continuously.
(ii) The drilling rates are quite high.

BY: KEYUR J PANSARA
(iii) Casing pipe is not required. The mud forms a clay lining on the bore wall and it prevents
caving.
(iv) When bore proves unsuccessful it can be abandoned right away as removal of casing pipe
etc., is not involved.
Reverse Rotary Boring Method:
This method is called reverse rotary method because the flow of drilling fluid is reversed as
compared to the (hydraulic) rotary boring method. The drilling rig used for reverse rotary
method is similar to that used for rotary boring. There are however, two variations. The first is
that the drill pipe is of larger diameter (say 15 cm) and second is that large capacity special pump
with open blade rotors is used. The pump allows large gravel to be discharged. The large
diameter drill pipe enables as big 12 cm diameter size stones to be lifted up to the surface.
As drilling fluid only water is generally used. It moves into the bore hole through the annular
space between the drill pipe and walls of the bore. The water picks up the cuttings and the
mixture is sucked upward by the pump through the drill pipe. Due to force of suction the rising
fluid has large velocity and it lifts with it big particles. Schematic diagram of the method is
shown in Fig. 18.9.
At the surface the mixture is discharged into a settling
pit. The water picks up fine particles from the
subsurface formations and it is not necessary to add
hentonite or any other mud to the water. The level of the
drilling fluid inside the annular space should be kept up
to the ground surface to prevent caving in of the hole.
By this method it is possible to drill wells of big
diameter say up to 150 cm. This is the cheapest method
of drilling large diameter wells in soft unconsolidated
formations made of sand, silt or soft clay.

BY: KEYUR J PANSARA
09-05-2017
Q-3 (C) with neat sketch explain slotted tube well.
Sometimes the nature of subsoil formation is not anticipated correctly. Obviously bore hole driven for
constructing strainer well will be a failure. If a mota formation is present cavity well may be resorted to.
But if neither of the conditions are existing the slotted tube well can be rightly constructed. There
should be of course an aquifer present at the bottom. In the bore hole (say 36 cm diameter) a 15 cm
diameter education pipe is lowered till it reaches the bottom. The bottom of the education pipe is
slotted as shown in Fig.
The size of the slots may be 25 mm x 3 mm with 12 mm spacing.
As the slots are quite wide, to avoid sand entry in the pipe a
filter of shingle is provided at bottom, surrounding the slotted
pipe portion. Finally before withdrawing the 36 cm diameter
pipe casing the shingle is poured in the annular space between
the education pipe and the casing pipe. The development of this
well is done gradually with the compressed air. Thus the slotted
tube well, unlike strainer well receives inflow only at bottom
09-05-2017
Q-2 (C) Explain ground water development.
A ground-water system consists of a mass of water flowing through the pores or cracks below
the Earth's surface. This mass of water is in motion. Water is constantly added to the system by
recharge from precipitation, and water is constantly leaving the system as discharge to surface
water and as evapotranspiration. Each ground-water system is unique in that the source and
amount of water flowing through the system is dependent upon external factors such as rate of
precipitation, location of streams and other surface-water bodies, and rate of evapotranspiration.
The one common factor for all ground-water systems, however, is that the total amount of water
entering, leaving, and being stored in the system must be conserved.
(09-05-2017Q-1(8)) ( 11-05-2015 orQ-1(8))
what is Well Completion Operation?
Completion is the process of making a well ready for production (or injection). This principally involves
preparing the bottom of the hole to the required specifications, running in the production tubing and its
associated down hole tools as well as perforating and stimulating as required.

BY: KEYUR J PANSARA
09-05-2017 Q-2 (C)
Explain ground water development.
A ground-water system consists of a mass of water flowing through the pores or cracks below
the Earth's surface. This mass of water is in motion. Water is constantly added to the system by
recharge from precipitation, and water is constantly leaving the system as discharge to surface
water and as evapotranspiration. Each ground-water system is unique in that the source and
amount of water flowing through the system is dependent upon external factors such as rate of
precipitation, location of streams and other surface-water bodies, and rate of evapotranspiration.
The one common factor for all ground-water systems, however, is that the total amount of water
entering, leaving, and being stored in the system must be conserved. An accounting of all the
inflows, outflows, and changes in storage is called a water budget.
Human activities, such as ground-water withdrawals and irrigation, change the natural flow
patterns, and these changes must be accounted for in the calculation of the water budget. Because
any water that is used must come from somewhere, human activities affect the amount and rate
of movement of water in the system, entering the system, and leaving the system.
(09-05-2017 Q-3 (D)) & (11-05-2015 orQ-3(D))
Q state information to be supplied to pump manufactures.
A Information to be supplied to pump manufactures are
1. Type of fluid: chemical and physical characteristics of the fluid to be pumped.
2. System-head curve: may be obtained from the manufacturer.
3. Potential system modifications
4. Operational mode: degree of flow, head fluctuation, and mode of operation (continuous or
intermittent)
5. Required margins: 15~20% over the design points
6. Pump selection: based on the fluid characteristics, turn-down ratio, discharge pressure and
system requirements, availability of space, lay-out, energy and pump costs, code requirements,
and the materials used in the construction.
 Reciprocating pumps (plunger or diaphragm type) for liquid chemical metering and
injection applications (small capacity)
 Centrifugal pumps - for wide variety of hydraulic head and over a wide range of
capacity requirements, for low to medium capacity with medium to high pressure.

BY: KEYUR J PANSARA
09-05-2017 Q-2 (D)
Explain the current ground water scenario in india.
It covers varying groundwater scenarios in the country including the highly developed metros,
the hilly region, the coastal cities, the cities tapping unconsolidated and hard rock aquifers. The
report briefly describes the administrative set up, status of water supply and demand,
groundwater scenario, feasibility of rainwater harvesting and groundwater development strategy.
It is an updated version of an earlier report on “Groundwater in urban environment in India”
(2000). Since then, groundwater regime, urban demography and water demand have changed
enormously. This report will form a scientific base for an in-depth understanding of urban
groundwater system including aquifer geometry, water level behavior and groundwater quality.
The possibility of artificial recharge to rejuvenate the urban aquifers has also been discussed.
Groundwater plays a very important role in meeting the water demand of Indian cities. There are
three types of situations (i) where the entire water supply is met from surface water (ii) where the
entire water supply is met from groundwater (iii) where there is a mixed supply, a combination
of both. The first option is no longer existent in absence of adequate and consistent supplies. The
option of own source is gaining ground and it invariably taps groundwater. Furthermore,
industries too have a network of their own wells.
Thus the groundwater regime beneath cities is being adversely affected. Where there is mixed
supply, generally the core part of the city may have surface water supply and the extension areas
depend on groundwater supply. This results in a groundwater mound in the central part and
declining trend in the peripheries. In the case of the third situation, extraction creates a
groundwater trough below the city. Besides this, the ever increasing sewerage and industrial
waste are polluting the fresh groundwater.
The report discusses the various options for sustainable water supply in urban India like
augmentation of water supply through rainwater harvesting, conservation and groundwater
recharge. This supported by groundwater regulation would enable overall improvement of water
resources in the cities. In addition there is need for demand management, which the urban policy
makers have to emphasize.
Though there are novel efforts of the government agencies, what are equally important are
innovative measures promoted by private and individuals in cities to augment water supply. The
urban centers have to learn from the successful experiences demonstrated by government and
NGOs to augment water supply. A decentralised approach, with coordination among the state,
private sector and civil society, is needed for evolving better water supply options in urban India.
There is also substantial potential for demand side management options. Unaccounted water in
urban areas exceeds fifty per cent which if saved can substantially meet the justified water
demand. Conservation, which is less expensive and more environmentally sound than new
investment, would minimize the future capital requirements. Water conservation can be achieved

BY: KEYUR J PANSARA
through more effective maintenance mechanisms, which can help to overcome the problems of
pilferage and leakage. Demand management can be achieved through financial incentives and
technological interventions.
The imperative need is to have sound planning strategies for managing, protecting and
conserving the urban aquifer systems for sustainable extraction of groundwater over a longer
period.
(09-05-2017 or Q-3 (D), 19-05-2016 Q-2(D), (10-11-2017 Q-3 )c( , Q-4 (A))
(11-05-2015 orQ-4 (A))
Enlist methods of drilling tube well, explain any one.
Techniques of drilling are:
- Hand-augur drilling
- Percussion drilling
- Water injection (jetting) drilling
- Sludge drilling.
- Rotary-percussion drilling
- Rotary drilling
Drilled wells can get water from a much deeper level than dug wells can—often up to several
hundred meters and smaller in diameter Drilled wells are typically created using either tophead
rotary style, table rotary, or cable tool drilling machines, all of which use drilling stems
that are turned to create a cutting action in the formation, hence the term drilling.
Drilled wells are usually cased with a factory-made pipe, typically steel (in air rotary or cable
tool drilling) or plastic/PVC (in mud rotary wells, also present in wells drilled into solid rock).
1.Hand-auger drilling :
The cutting tool (known as the auger head) is rotated to cut into the ground, and then withdrawn
to remove excavated material. The procedure is repeated until the required depth is reached.
Note: This method is only suitable for unconsolidated deposits.
Advantages of hand-auger drilling:
Inexpensive.
Simple to operate and maintain.
Disadvantages of hand-auger drilling:
Slow, compared with other methods.
Equipment can be heavy.
Problems can occur with unstable rock formations.
Water is needed for dry holes.

BY: KEYUR J PANSARA
2.Jetting:
Water is pumped down the center of the drill-rods, emerging as a jet. It then returns up the
borehole or drill-pipe bringing with it cuttings and debris. The washing and cutting of the
formation is helped by rotation, and by the up-anddown motion of the drill-string. A foot-
powered treadle pump or a small internalcombustion pump are equally suitable.
Advantages of jetting:
The equipment is simple to use.
Possible above and below the water-table.
Disadvantages of jetting:
Water is required for pumping.
Suitable for unconsolidated rocks only (e.g. sand, silt, clay)
Boulders can prevent further drilling
3.Sludging (reverse jetting)
Water flows down the borehole annulus (ring) and back up the drill pipe, bringing debris with it.
A small reservoir is needed at the top of the borehole for recirculation. Simple teeth at the
bottom of the drill-pipe, preferably made of metal, help cutting efficiency.
Advantages of sludging:
The equipment can be made from local,
low-cost materials, and is simple to use.
Disadvantages of sludging:
Water is required for pumping.
Suitable for unconsolidated rocks only.
Boulders can prevent further drilling
4.Percussion drilling
The lifting and dropping of a heavy (50kg+) cutting tool will chip and excavate material from a
hole. The tool can be fixed to rigid drillrods, or to a rope or cable. With a mechanical winch,
depths of hundreds of meters can be reached
Advantages of percussion drilling:
• Simple to operate and maintain.
• Suitable for a wide variety of rocks.
• Operation is possible above and below the water-table.
• It is possible to drill to considerable depths.
Disadvantages of percussion drilling:
• Slow, compared with other methods.
• Equipment can be heavy.
• Problems can occur with unstable rock formations.
• Water is needed for dry holes to help remove cuttings

BY: KEYUR J PANSARA
11-05-2015 Q-3(A), 09-05-2017 Q-4 (B)
State equipment required for conducting an yield test on well
1. Pumps
 Submersible
 Jet
2. Flow metering and control devices
 Gate valve
 Orifice or Rectangle weir
 Constant flow restrictor valve(Dole valve)
 Rotameter
 Calibrated bucket or barrel
 High capacity flow meter
 Manometer
3. Water level measuring devices:
 Electrical (e.g. water level meter, sonic meter)
 Air line
 Tape measure
19-05-2016 Q5-(B)
Describe how a discharge test is conducted on a well to determine its yield.
Discharge Test:
In this method water level in the well is depressed by pumping to any level below the normal
level. Then the pumping is stopped and time taken by the percolating water to fill the well to any
particular level is noted. Total quantity of water percolated into the well is calculated by knowing
cross-sectional area and rise in the water level after stoppage of pumping. The rate of percolation
or the yield of well can be arrived at by dividing the quantity of water by the time. This test is
carried out generally in a driest period to take worst condition into account.
Now it can be inferred that the actual pumping test of determining available yield is most reliable
but it is difficult to conduct the test accurately. Whereas recuperation test is very simple to
perform but it does not give the maximum safe yield. The reason is as the water level in the well
rises the safe maximum working head is not maintained throughout the period of observation.
19-05-2016Q-3(B)
Explain Advantages and disadvantages of ground water over other water resources.
ADVANTAGES
 Rocks act as a natural filter
 No loss of water through evaporation
 No requirement for expensive and environmentally damaging dams
 Pumping costs low

BY: KEYUR J PANSARA
DISADVANTAGES
 Sedimentary rocks and presence of aquifers
 surface subsidence
 pollutants have long residence time
 Groundwater not always suitable for drinking
11-05-2015
Q-1(2) Define term sea intrusion
Seawater intrusion is the movement of saline water into freshwater aquifers, which can lead to
contamination of drinking water sources and other consequences. Seawater intrusion occurs naturally
to some degree in most coastal aquifers, owing to the hydraulic connection between groundwater and
seawater.

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