SOIL EXPLORATION AND GEOTECHNICAL DESIGN OF A FOUNDATION

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 724
SOIL EXPLORATION AND GEOTECHNICAL DESIGN OF A FOUNDATION
Bhagyashri Batwalkar1, Ishika Sonawane2, John Livinston3, Tejaswini Narayane4,
Dr. Prasenkumar Saklecha5
1-4B. E. Student, Department of Civil Engineering, New Horizon Institute of Technology and Management Thane,
Maharashtra, India
5 Professor Department of Civil Engineering, New Horizon Institute of Technology and Management
Thane, Maharashtra, India.
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Abstract - Before the actual construction process starts, it
is important to conduct a site investigation and soil
exploration to acquire vital information about the soil and
site conditions. In a construction site investigation is the first
and crucial step. These are outlined in the project to ensure
that the site is appropriate for the proposed construction and
to offer recommendations on the design and construction
processes.
Following soil investigation based on the soil report, further
geotechnical design of a shallow foundation was performed;
however, the results indicated that the load coming from the
structure was less than the results of the shallow foundation,
so we opted for the geotechnical design of a pile foundation,
which resulted at an end bearing capacity greater than the
load coming from the structure. The geotechnical design of
the pile consists of recommending the size of the pile and
calculating the safe working load of each pile.
Key Words: Deep Foundation, Pile Foundation, Shallow
Foundation, Bore-hole, Site Investigation, Soil
Exploration.
1. INTRODUCTION
The geotechnical design of a multi-story commercial
building includes a thorough site investigation and soil
report analysis. After studying the soil report, the
appropriate type of foundation was chosen using
calculations and information from the site report such as
type of soil, depth of bore hole etc.
This involves a detail site investigation study and analysis of
soil report our site. After studying the soil report, selected
foundation type and site report including site condition,
type of soil, and depth of bore-hole and basically, there are
two types of foundation: 1. Shallow 2. Deep foundation. For
selecting the type of foundation following detailed design
steps were involved:
– Study of soil report
– Calculation structural load
– Bearing capacity calculation of shallow foundation.
i. As per IS 6403, 1981 and IRC 78, 2014 - 1: If the soil
type is suitable (hard strata) to carry the load and the
bearing capacity exceeds the load resulting from the
construction, we may use a shallow foundation.
ii. If the foundation's bearing capacity is less than the
load from the building, we must use a raft or pile
foundation.
For condition 2: Further we have to calculate load carrying
capacity of pile foundation.
There are different design methods to calculate bearing
capacity and End bearing capacity of soil/ Rock based on
site condition.
1.1 Site investigation
The process of acquiring and analyzing information on a
site's surrounds, including the geology, topography,
hydrology, and environmental conditions, is known as site
investigation. The main objective of a site investigation is to
find any potential issues or hazards that might impact the
construction process or the final structure's stability and
safety.
Site investigation is the process of studying about a site's
physical and environmental characteristics in order to
determine whether it is suitable for a particular civil
engineering project. It entails a careful analysis of the
geology, hydrology, topography, soil properties, and other
elements that potentially influence the site's development
or usage.
Drilling, sampling, and geophysical surveys are just a few of
the field and lab tasks that site investigations normally
involve. The investigation's findings are summarized in a
report that offers recommendations for the project's design
and construction as well as any possible mitigation
strategies to address safety or environmental issues.
1.2 Soil Exploration
A phase of site research called soil exploration focuses
primarily on the soil characteristics of the location. In order

to assist the design and construction process, soil
exploration aims to give thorough information about the
soil conditions.
The following steps are commonly included in the soil
exploration process:
A) Borehole drilling
Borehole drilling is the process of making holes in the earth
to gather soil samples for analysis.
B) Sampling
To ascertain the kind, consistency, and strength of the soil, soil
samples are gathered from boreholes at various depths.
C) Testing in the lab
The physical and chemical characteristics of the soil
samples, such as density, permeability, shear strength, and
compressibility, are examined in the lab.
D) Analysis
The design and construction processes are made more
effective by using the information gathered during the soil
exploration phase. For instance, it may be used to decide on
the necessary kind and depth of foundations, the site's slope
stability, and the best building methods.
In conclusion, site investigation and soil exploration are
crucial steps in the building process that provide important
details about the site conditions and soil characteristics. The
stability and safety of the completed structure are ensured
using this information, which is also utilized to guide the
design and construction process.
1.3 Foundation:
The lowest portion of a building or structure, known as the
foundation, is where the weight of the structure is
transferred to the ground or rock below. The performance
and safety of the entire structure can be greatly impacted by
the design and construction of the foundations, which are
essential parts of any building or structure.
The several types of foundations frequently used in building
construction are as follows:
Shallow Foundation:
When the earth is sturdy enough to sustain the weight of
the structure close to the surface, shallow foundations are
employed.
Deep Foundation:
When the soil at the surface is unstable or weak and unable
to sustain the weight of the structure, deep foundations are
employed.
The following category was explored for deep foundation
for this project:
• Pile Foundation:
Pile foundations are employed when a structure has to be
sustained at a deeper level and the soil close to the surface
is unstable. They have a long, lean form that might be
cylindrical or rectangular.
1.4 Site Details:
NHES Educational Complex near Village Kavesar, Anand
Nagar Crossing of Ghodbunder Road in Thane, Maharashtra,
to establish a teaching hospital and medical college building.
The geotechnical investigation report for all nine completed
boreholes at the Thane site is included in this report.
The investigation site is a region of the area known as the
"Deccan Traps," a term used in Indian geology. The present
researches reveal that the geologic occurrences of various
rock types, including the deposits of mafic rocks, are
separate from those in the remainder of the Deccan Trap-
covered area. Amygdaloidal Basalt, Compact Porphyritic
Basalt, etc. In boreholes around Thane regions, a few
marker horizons (trachytic, Tachylite beds) have been
found. The levels of these, however, do not relate. They have
been described in the core logs that are included. According
to recent studies, it is not possible to completely rule out the
possibility of sub-aqueous volcanic eruptions.
The geologic environment of this area corresponds to the
literature review conducted for the Geology of Mumbai
region; it shows that the volcanic activity in this area differs
from that of the rest of Maharashtra's volcanic province in
various ways, which include their association with several
evolved rock types like Rhyolites and Trachytes with
significant amounts of felsic and basic tuffs, and their being
partially or entirely sub-aqueous eruptions as indicated by
pillow structures and spilitic compositions
According to the literature research, there are not many
defects in the Mumbai region. The area has active
earthquake activity.
The document contained includes sections on the lithologic
descriptions, as well as their geotechnical relevance. These
sections are further supported by microscopic data, which
are attached.
Foundation
Shallow
foundation
Deep foundation

2. DESCRIPTION OF PROJECT
2.1 Shallow Foundation:
Bearing capacity & settlement pressure of soil at 3m depth
for Shallow foundation area as follow,
i. Bearing Capacity – Using Standard Penetration Test
– N Value
For Square and Circular Footing:
qnu= 1/3.0 ( N2 BWγ + 3(100 + N2) Df Wq
qnu= 0.33 N2 BWγ + 1 (100 + N2) Df Wq
Where,
N = Standard Penetration test value
qnu = Bearing capacity
Table -1: Bearing Capacity values using N- value
BH Qnu Kn/m2
BH2 827.04
BH3 1017.36
BH4 1123.5
BH5 1017.36
BH6 1485.84
BH7 1017.36
BH8 918.54
BH9 1017.36
ii. Settlement Analysis- using Teng’s Equation
Qnp = 35 (N – 3) × (B + 0.3 / 2B)2 × Wγ × Rd
Where, Rd = (1 + Df/ B ≤ 2.0) …...Depth Correction Factor
Table -2: Settlement Analysis using Teng’s Equation
BH Qnp
BH2 181.125
BH3 221.37
BH4 231.5
BH5 221.37
BH6 301.87
BH7 221.37
BH8 201.25
BH9 221.37
2.2 Pile Foundation
i. Load Carrying Capacity of Pile foundation
= ultimate capacity of pile
= ultimate end bearing
f = ultimate side socket shear
Kₛₛ = Empirical co-efficient (value ranges from 0.3-1.2)
Qc = avg unconfined compressive strength of rock
f = depth factor
= 1+ 0.4 x length of socket / dia of socket
Ab =c/s of base pile
Aₛ =surface area of socket
Cus = Ultimate shear strength of rock along socket length
K = 1.03
qc = 6118.29 t/m2
d = 1+0.4x3x1(3d)/1
=2.2 = 1.2
Ab = π/4x1²
= 0.785 m2
Aₛ = πd = π x1x3
=9.42 m2
Cus =0.225x√ 9c
= 17.59
 For Diameter = 1m
Qallow = (Re/3 ) + (Raf/6)
= 5763.42/3 + 165.69/6
= 1948.75 ton
Foundation Analysis and
Design
Shallow
Foundation
Deep
Foundation
Pile Foundation
c
×df ×Ab + Aₛ×Cus
𝑸𝒖 = 𝑹 + 𝑹 f
𝑸𝒖 = Kₛₛ ×q
Capacity of Piles in Intermediate Geo-Material and
Rock
 Formula
𝑸𝒖 = 1 x 6118.29 x 1.2 x 0.785 + 9.42 x
17.59 = 5929.12 ton

 For Diameter = 1.2m
= 8296.40/3 + 198.76/6
= 2798.59 ton
 For Diameter = 0.9m
= 4698.84/3 + 134.21/6
= 1588.64 ton
2.3 Load coming from Structure:
Height of building – 75m
No. of floors – 20 floors
Each floor ht. – 75m
Size of each room – 8.25 X 9.25m
Corridor size – 8.25 X 4m
Live Load – 5 kN/
Thickness of Slab - 150mm = .15m
Size of beam – 400 X 450mm
Load Calculation
1. Wall Load:
Wall Load = 0.23 x 3.15 x 2.5
= 1.81 t/m
Total Load = Load per m x Total length
= 1.81 x ( 9.25+5)
Wall load = 25.75 ton
2. From column:
Volume of col. = π4 x 12 x 3.75
= 2.94 m3
Volume of steel = 1% of concrete
= 0.029m3
Load on Column = 2.94 x 2.5 + 0.029 x 7.8
Column Load = 7.576 ton
Volume of col. = 0.4 x 0.45 x 1
= 0.18 m3
= 0.0036 m3
Load on Beam = 0.18 x 2.5 + 0.0036 x 7.8
= 0.48 t/m
Total Load on
beam = 0.48 x (8.25 x 2 + 9.25 x 2)
Load on Beam = 16.8 ton
4. From Slab:
Slab load S1 = 0.15 x 8.25 x 9.25
= 11.44 m3
= 0.22 m3
Total Load on
Slab S1 = ( 11.44 x 2.5) + ( 0.22 x 7.8)
= 30.31 ton
Slab load S2 = 0.15 x 8.25 x 5
= 6.18 ton
Total Load on
Slab S2 = ( 6.18 X 2.5) + ( 0.12 X 7.8)
= (16.38 + 30.31)/2
Total Slab Load = 23.34 ton
Total Load on Column = 73.45 × 21
= 1542.45 ton
3. OBSERVATIONS
3.1 For Shallow Foundation:
• Based on the subsurface conditions met, competent
stratum is not available at shallower depth.
• Silty sand is observed from ground level to the depth
varying from 6.5 m to 13.5 m in all boreholes.
• Underlying this layer, completely weathered Basalt is
encountered at depth from 6.6 m to 24.0 m.
• Topography of the terrain is seen nearly flat. The site is
Deccan trap basically consisting of Basaltic rock.
• Basalt here is not of good quality.
3.2 For Pile Foundation:
• Pile diameter considered in analysis is 1 m and 1.2 m.
• The strata consist of overburden soil followed by
weathered rock and at further depths. The relative
depths vary from bore to bore.
Total Load on Column =
1800t
𝑸𝒖 = 1 x 6118.29 x 1.2 x 1.13 + 11.30 x 17.59
= 8495.16 ton
𝑸𝒖 = 1 x 6118.29 x 1.2 x 0.64 + 7.63 x 17.59
= 4833.05 ton
3. Beam Load:

• For the purpose of assessment of pile capacity, the
contribution from weathered rock and overburden is
not considered.
• All Borehole samples show veins and abnormally low
UCS in some rock samples. Hence it is not considered as
representative.
• As the overburden is observed from ground level to the
depth varying from 3.00 m to 9.00 m it is not advised to
go for shallow foundation. The heterogeneous nature of
the strata leads to settlement of unpredictable nature.
Instead we recommend to adopt pile foundation to
transfer the load to firm strata. With this, settlement
will be considerably low
3.1. Results:
I. Shallow Foundation
The results after calculating the Bearing capacity &
settlement pressure of soil at 3m depth for Shallow
foundation area as follow,
Table -3: Results of shallow foundation
Where,
N = Standard Penetration test value
Qnu = Bearing capacity
qns = Safe Bearing Capacity
II. Pile Foundation
Table -2: Results of Pile foundation
Sr.
No.
Diameter of
pile m
End Bearing
Capacity
Qu ton
Allowable
Bearing Capacity
Q allow
1 0.9 4833.0.5 1588.64 ton
2 1 5929.12 1948.75 ton
3 1.2 8495.16 2798.59 ton
III. Load from Structure on Foundation
Manual calculation for structure
• Total wall load = 25.75 t
• Load on beam = 16.8 t
• Load on column from slab = 7.576 t
• Total load on slab 1 = 30.31 t
• Total load on slab 2= 6.18 t
• Total load on column= 1800t
Total Load = 1800t (17651.97 kN)
4. CONCLUSION
At the NHES Educational Complex near the village of
Kavesar, Anand Nagar Crossing of Ghodbunder Road in
Thane, Maharashtra.
Soil Investigation: The geotechnical investigation reports
for all nine completed boreholes were studied and we
conclude that,
• Silty sand is visible from the surface to a depth ranging
from 6.5 m to 13.5 m.
• Fully weathered basalt is found at a depth of 6.6 meters
and 24.0 meters under this layer.
• From the ground, up to a depth ranging from 6.5 m to
13.5 m, overburden is visible.
• The land appears to have a relatively level topography.
• The location is essentially a basaltic rock Deccan trap.
• Here, the basalt is of poor grade.
Pile and shallow foundation were considered for the design
of foundation
Shallow Foundation
After calculating the bearing capacity of the shallow
foundation, it was found to be less than the load coming
from the structure, which is 1800 tonnes (17651.97 kN)
Furthermore, based on the subsurface conditions
encountered, a competent stratum is not available at a
shallower depth. In all boreholes, silty sand was observed
from ground level to a depth ranging from 6.5 m to 13.5 m,
with completely weathered basalt found underlying this
layer at a depth ranging from 6.6 m to 24.0 m. The
topography of the terrain is nearly flat, and the site consists
of basaltic rock from the Deccan trap, but the quality of the
basalt is not good. Considering the overburden and soil
condition, it is not recommended to proceed with a shallow
foundation.
Pile foundation:
Based on soil report and calculation, A pile foundation is
advised since excellent grade rock is not present at shallow
depths, according to field and laboratory research. A pile
foundation can transfer the load of the structure to a deeper
BH N qnu kN/m2
qns kN/m2
= qnu/3
BH1 - - -
BH2 12 827.04 275.68
BH3 14 1017.36 339.12
BH4 15 1123.5 374.5
BH5 14 1017.36 339.12
BH6 18 1485.84 495.28
BH7 14 1017.36 339.12
BH8 13 918.54 306.18
BH9 14 1017.36 339.12

and more competent stratum, thus ensuring the stability
and safety of the structure.
The pile diameters were selected as 0.9m, 1.0 m and 1.2 m.,
as per IRC 78, the allowable pile capacity were observed to
be 1588 tonnes (158822 KN), 1948 tonnes (19409 kN)
2798 tonnes (27879 kN) respectively.
Finally, a single pile with diameter 1m having load caring
capacity of 1948 ton was suggested for the proposed
structure
As per IRC 78, the material to be used for the construction
of pile foundation shall be M30 grade Reinforce cement
concrete
5. REFERENCES
Indian Standard, IS: 2720 Part 4 (1995, Reaffirmed
2015). “Grain size analysis of soil” BIS, New Delhi.
[1] Indian Standard, IS: 2720 Part 3 (1980, Reaffirmed
2016). “Determination of specific gravity” BIS, New
Delhi
[2] Indian Standard, IS 2720 Part 5 (1985, Ref. 2015)).
“Liquid Limit and Plastic Limit Test” BIS, New Delhi
[3] Indian Standard, IS 2720 Part 6 (1972, Ref. 2016).
“Shrinkage Limit Test” BIS, New Delhi
[4] Indian Standard, IS: 12070-1987, code of practice for
design and construction of shallow foundations on
rocks
[5] Indian Standard, IS: 13365 (Part 1): 1988, Quantitative
classification system of rock mass-Guidelines.
[6] Indian Standard, IS: 6403: 1981, Code of practice for
determination of bearing capacity shallow foundations.
[7] Indian Road Congress, IRC 78: 2014, Standard
Specifications and coder of practice for road bridges.
[8] Dr.s.k.tiwari, m.k.kumawat, (2020) “Guidelines for
Planning Soil Investigation of Building Project”
[9] Harry G. Poulos, (2018) “Tall building foundation design
method and application”
[10] Vedprakash Maralapalle, Analysis and Design of
foundation for G+5 residential building”
[11] A.R.Arora, “Soil Mechanics and Foundation Design”
[12] MJ Tomlinson, “Foundation Design and
Construction”
[13] H.g. Poulos, E.H. Davis “Pile Foundation Analysis
and Design”

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