1. Proceedings of Indian Geotechnical Conference
December 15-17, 2011, Kochi (Paper No. M-253)
DEVELOPMENT OF SOIL SUITABILITY MAP FOR GEOTECHNICAL APPLICATIONS
USING GIS APPROACH
S.Sakunthala Devi, ME Student, Anna university- Chennai, sakugopiram@gmail.com
V.K Stalin, Professor of Civil Engineering, Anna University-Chennai, staliniisc@yahoo.co.in.
ABSTRACT: The preliminary geotechnical site investigation aims to develop a working site model that is used to analyze
the site and to plan site activities.GIS is a versatile tool that can be used to aid preliminary geotechnical site evaluations and
it is time saving.The use of the GIS database allows the engineers to easily and rapidly manage large volumes of data while
also being able to examine it in detail .Hence in this study the geotechnical database and soil suitability map were created
for South Chennai.Various interpolation technique were used to create the spatial continuity and variability of the important
geotechnical parameters and the database was created from available bore log data.These database and the thematic map
serves as a basic tool in effective planning and execution of the site investigation work by providing guidance on spatial
continuity of geotechnical properties in the south Chennai.
INTRODUCTION statistical techniques, geotechnical engineers can quantify
With the introduction of GIS, missing spatial data & the degree of spatial variation of soil properties and obtain
corresponding attribute information could be generated. more meaningful estimates at unsampled locations and
GIS systems are time saving, cost economical, useful for provide input to reliability analyses.Regression analysis is a
Structural Engineers, Geotechnical Engineers, urban statistical tool for the investigation of relationships
Planners and even the local inhabitant for any future between variables. The uncertainty in the estimation of soil
developmental activities in the area concerned. Many properties are described in terms of standard deviation,
geotechnical database and suitability maps were created all coefficient of variation and confidence interval. From
over the world. In model study [1] Geotechnical database statistical results, the mean, median and ranges of 95%
for Bangkok city (GeSEP) was created to manage and confidence intervals for each property are established.
interpret the soil data’s obtained from more than 20000 Those ranges can help structural and foundation engineers
boreholes and GIS software GRASS 5.0 was used to during the process of foundation analysis.
visualize soil profiles. The model study [2] involves
multiple regression equation, chi-square test and k-nearest
neighbour classification to create, Soil Characteristics
Prediction Model (SCPM) for Coimbatore city and GIS was
used to manage the database and to develop thematic maps.
In model study [3] by using the GIS tools in conjunction
with the ACCESS database, GeoCovilha XXI database was
created and the data of different tests were visualised.
Model study [4] deals with the generation of the
geotechnical database using the program ArcView/GIS 9.0.
for city of Mayagüez and this was used to identify areas of
liquefaction potential or seismic hazards..North Sea
geotechnical database was created from collected
geotechnical reports in quadrant K and L North Sea using
GIS and statistical approach in model study [5]. In this
work geotechnical database and various geotechnical maps
were created for South Chennai.
METHODOLOGY
The flowchart used to create the database and themetic map
was shown in Fig. 1.GIS is a specific information system Fig. 1 Flow chart for creating map and database
applied to geographical data and is mainly referred to as
system of hardware, software and procedures designed to Geotechnical Database
support the capture, management, manipulation, analysis, Paper maps are used traditionally as both storage and
modeling and displaying of spatially referenced data for display medium. They work well when the amount of data
solving complex planning and management problems.Using is small, the rate of data changing is slow but when the data
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2. S.Sakunthala Devi & V.K.Stalin
set becomes larger, it is necessary to prepare several special maps to avoid confusion and to facilitate reading. In that
situation, the traditional maps or plans show some
shortcomings. Those problems can be avoided by GIS
which can handle essentially unlimited data and provide a
secure and easily updated database to generate maps for any
specialist use to extract useful information hidden inside a
large data collection, the data should be well organised..
Meanwhile, databases show their flexibility. To manage
subsurface data collected from borings, the geotechnical
database management system was designed. The
geotechnical information in this database is classified into
several tables. The database is implemented using a
Microsoft Access software package. The advantages of
organising geotechnical data into a relational database are
to handle an enormous amount of data, to share
information, to update data quickly, to derive thematic
maps easily. Furthermore, incorporating geotechnical
database with GIS and geostatistics packages can enable to
predict the spatial variation of variables, to visualise
geological features or to locate the potentially hazardous
areas. Those advantages help the engineers, designers and
the authorities to make the decisions effectively.
Study Area Fig. 2 N-value map @ 8.5m depth
The study area was divided into two zones and the details
are shown in Table 1. Ground Water Table Map for Various Zones of Study
Area
Table 1 Study area details containing various zones The GWT map for the zone I and zone II were created by
Topo to Raster interpolation technique. The GWT map for
Zone Village the zone I & II were shown in Fig. 3.From the map it is
I Kotturpuram,Adyar,Besant Nagar,Perungudi inferred that, for Zone I the GWT varies 0.6m to 4.4m and
in Zone II the GWT varies 1 to 3.1m.
II Egatur, Navalur, Keelambakam,Siruseri,
Padur,Thoraipakkam
RESULTS AND DISCUSSION
Ground Water Table, Bearing Capacity of soil (Computed
from ‘N’ value) maps were developed for the study area
and these maps are used in the design of geotechnical
structures.Further the consideration were also given with
respect to statistical analysis of various geotechnical
parameter and the regression equation for various
dependent geotechnical parameter were developed from the
bore log data. The geotechnical database was created using
access. The above sequence of work was discussed
elaborately in the following sub section.
Geotechnical Map for Various Zones in the Study Area
on Various Depths Using GIS
The variations of geotechnical parameters (N-value, -
value, WT, QU) with respect to depth for two different
zones were analyzed.
N-value map for various zones of study area
The N-value map for Zone I & Zone II were created by
Kriging and IDW method .The N-value maps at 8.5m depth
Fig. 3 Ground Water Table map for zone I and Zone II
was shown in Fig. 2.
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3. Development Of soil Suitability Map for Geotechnical Application Using GIS Approach
Angle of Internal Friction ( ) Map for Various Zones of primary key (project ID of project table) to foreign key
Study Area (project ID of other table).Once database was organized,
The value was computed from the N value using the necessary information can be derived in the form of reports,
Teng’s relationship.By using IDW interpolation method, forms (shown in Fig. 6)
the variation in at various depth were obtained. The
value map was given in Fig. 4.
Fig. 5 Qu map for zone I and Zone II @ 10 m depth
Fig. 4 map @ 0.75 and 1.5 m depth
Qu map for various zones of study area
The bearing capacity of the pile was calculated from the
Meyerhof equation from the SPT N value. The dia of pile
( ) was 0.6m , length was 10m and the embedded length
was 8.5m. The ultimate bearing capacity (Qu) was
calculated for Zone I and Zone II .The Qu maps for zone I
& II were created by IDW interpolation technique and were
shown in Fig. 5. In zone I, the mean value of Qu was
3420KN .In zone II, mean value of Qu was 3953KN.
Geotechnical database using ACCESS
From the available bore log data the geotechnical database
was created for Chennai with the help of application called
MS access. The set of data were stored inside the database
named as Chennai database. This database consists of
various tables which contains information such as ground
water levels, SPT results, borelogs and laboratory test
results and this table were interconnected by linking Fig. 6 Form 1(area wise project work)
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4. S.Sakunthala Devi & V.K.Stalin
Statistical Analysis of Various Geotechnical Properties CONCLUSIONS
Statistical techniques were used to quantify the degree of The study area composed of two different zones and the
spatial variation. The statistical approach for N-value and base map was created. The best interpolation technique
value was discussed. Descriptive statistics include the available for creating N value map was Kriging which was
mean, median, standard deviation, maximum, minimum validated based on cross interpolation technique .From SPT
value i.e.) the statistical parameters. N values, the angle of internal friction of a zone at different
Relationship between N and Other Geotechnical depths were computed based on correlation between N-
Parameters value and for granular soil(After Peck , Hanson and
The SPT N of soil is one of the most important parameter Thomburn).The allowable bearing capacity map at 10m for
used for geotechnical analysis .It can be obtained from the two zones were computed based on the Meyerhof
standard penetration test.SPT test were quite expensive and equation for the developed N-value map. Using the
on the other hand grain size distribution test, water content computed average SPT N-values, bearing capacity for 0.6m
were obtained at low cost. The relationship is established dia pile of 10m length was found out. The geotechnical
between SPT N and grain size distribution .Firstly the linear database named Chennai Database was created to manage
equation was examined large quantity of available data .The statistical analysis of
The linear relationship was given by SPT N and was developed to quantify the degree of
SPT N =constant+c1gravel+c2CS+ c3 MS+c4 FS + c5 silt spatial variation of these soil properties. There statistics
Where C1, C2, C3, C4 and C5 were coefficient of the were made. The uncertainties present were represented in
independent variables and statics were given in Table 2. terms of SD, coefficient of variance ant the coincidence
interval of 95%.The relation between SPT N and other
Table 2 Regression statistics for linear relationship geotechnical parameters were developed with help of the
Regression Statistics regression analysis .Both linear and quadratic relationship
were established . The developed graphs and the database
Multiple R 0.627765
can be used by civil engineers, geotechnical engineers and
R Square 0.394089 geologists for planning, designing, investigation, analysis
Adjusted R Square 0.361791 and design of structures.
Standard Error 28.52346
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Observations 111
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Observations 111
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