GEOTECHNICAL INVESTIGATION REPORT for the Proposed

Institutional Buildings at Plot No. 5, Sector - Techzone, Greater Noida

EXECUTIVE SUMMARY

Yatha Infratech Private Limited, A76, Sector -5, Noida Uttar Pradesh are in the process of constructing Institutional Buildings at Plot No. 5, Sector-Techzone, Greater Noida.

The proposed structures consists of a basement, stilt and ten upper floors.

The Geotechnical investigation programme has been undertaken at the site, as per the scope of investigation, stipulated by the client. The scope of work consisted of conducting boreholes in soil strata down to 30m depth at six locations.

The results of the field investigations indicate that the subsoil strata consists of sandy soils down to about 4m depth below which the subsoil strata predominantly consists of clayey sandy silt down to the maximum depth investigated i.e. 30m below the existing ground level except for occasional layers of sandy soils in between.

The N-values (N-values 5 -31) indicate that the subsoil is loose to medium dense down to about 8m depth below which the subsoils is medium dense (N-values 8 - 69) down to the depth investigated.

Ground water table had been encountered at a depth varying between 7.3m and 8.7m below the existing ground level in the boreholes, during the period of field investigations, i.e October 2022.

Considering the type of structures involved and the subsoil characteristics as determined from the geotechnical investigations, Raft Foundations have been recommended at a depth between 5m and 6m below the existing ground level.

For Raft Foundations, net allowable bearing pressure of 18 t/m2 and gross allowable bearing pressure of 26 t/m2 have been recommended for an allowable settlement of 75mm.

However, For minor structures at ground level, Isolated/ Strip Footings, have also been recommended at a depth of 1.5m below the existing ground level, net allowable bearing pressures varying between 8- 12 t/m2 have been recommended for various widths of foundations for an allowable settlement of 50mm.

Precaution : - Foundation surface must be compacted heavily. If any loose pockets are observed, the same shall be filled with brickbats/gravel and compacted. Foundations can subsequently be placed over such a prepared surface.

1.0	INTRODUCTION

1.1	Yatha Infratech Private Limited, A76, Sector -5, Noida Uttar Pradesh are in the process of constructing Institutional Buildings at Plot No. 5, Sector-Techzone, Greater Noida.

1.2	To design the substructures for the proposed structures, adequate information regarding the subsoil conditions is required. For this purpose, detailed geotechnical investigations have been undertaken at the site of the proposed structures.

1.3	This report contains the details of the geotechnical investigations conducted along with the results and analysis of the investigations and the recommendations thereof.

1.4	The geotechnical investigation has been carried out as per the verbal / email authorization from Mr. Bharat Khetan of Yatha Infratech Private Limited. This authorization has been given in response to our offer no. NCD/Q/YIPL/100A/2022 dated 12th October 2022.

2.0	PROJECT DETAILS

2.1	Site Location

2.1.1	The site for the proposed project is located at Plot No. 6, Near Bennett University, Techzone-2, Greater Noida and is situated at a distance of about 14 km from Pari Chowk towards Bennett University.

2.2	Site Layout and Topography

2.2.1	A schematic site plan showing the dimensions and other details of the site is enclosed in this report (fig. 1a).

2.2.2	Maximum level differences of about 4m had been observed at the site during the period of field investigations. However the general level of the site had been observed to be almost same as that of near by road level.

2.2.3	A large portion of the site had been observed to be excavated down to a maximum depth of about 4m below the existing ground level.

2.2.4	The site had been observed to be almost levelled in its topography. However, the general level of the site had been observed to be about 0.5m below the adjacent Sector main road.

2.2.5	Vegetation in the form of grass, bushes and occasional trees had been observed at the site, during the period of field investigations.

2.2.6	The colour of the surface earth had been observed to be Yellowish brown.

2.3	Seismic Zone

2.3.1	The present site is located in the Seismic Zone - IV which is an area of high seismic activity and earthquake intensity, as per the seismic zoning map of India given in BIS code IS:1893 (Part1) - 2016.

2.4	The Structure/s

2.4.1	The proposed structures are Institutional buildings consisting of one basement, ground floor and about ten upper floors.

2.4.2	The structures are understood to be framed ones and the construction is proposed to be of Reinforced Cement Concrete.

3.0	OBJECT OF INVESTIGATIONS

3.1	For designing the foundation system of the proposed structures, the following data are required :

a)	Type of foundation

b)	Depth below the ground level at which the foundation system is to be laid

c)	Allowable bearing pressure at the foundation level

3.2	To determine the above factors, the following information would be required:

a)	The subsoil profile indicating thickness of the various soil strata, to a depth within the influence zone below the foundations

b)	Engineering properties of the soil strata at various levels

c)	Physical characteristics of the soil strata

d)	Variation of strength of soil strata with depth

3.3	For evaluating the above parameters, field investigations and laboratory investigations on the soil samples collected during the field investigations, have been carried out.

3.4	The results from these investigations have been analysed to provide the recommendations for the design of foundations.

4.0	SCOPE OF INVESTIGATIONS

4.1	The scope of investigations as stipulated by the client consists of :

a)	Conducting boreholes in soil strata down to 30m depth at six locations.

b)	Conducting relevant laboratory tests on soil samples recovered.

c)	Preparation and submission of a technical report in three copies containing the details of the tests carried out, their analysis and recommendations regarding the foundation system to be adopted.

4.2	The following operations were to be undertaken while progressing the boreholes:

a)	Conducting standard penetration tests at 1.5/3m intervals.

b)	Recovering undisturbed soil samples from various levels of the subsoil strata.

c)	Recording ground water table levels, if met with.

5.0	FIELD INVESTIGATIONS

5.1	Preliminary Details

5.1.1	Field investigations had been carried out between 15th October 2022 and 23rd October 2022.

5.1.2	A schematic site plan showing the test locations are given in fig. 1a.

5.1.3	Photographs showing view of the site and work under progress are given in fig. 1b.

5.2	Boreholes

5.2.1	All the boreholes were progressed by shell and auger method. Casing pipe were used to stabilize the sides of the boreholes below water table.

5.2.2	All the boreholes BH1 to BH6 had been progressed down to stipulated depth of 30m below the existing ground level.

5.2.3	Boreholes BH1 to BH4 had been conducted on existing ground level whereas boreholes BH5 and BH6 had been conducted in the excavated area which was about 2.5m below the existing ground level.

5.2.4	The diameter of the boreholes was 150/100mm.

5.2.5	Standard penetration tests were conducted at 1.5/3m intervals. Disturbed soil samples recovered from split spoon samplers were retained for identification purposes.

5.2.6	Undisturbed soil samples were recovered by thin walled tubes conforming to IS : 2132. These tubes had an area ratio of less then 10%.

5.2.7	The ends of sample tubes were sealed by wax to prevent loss/ ingress of moisture. Disturbed soil samples were enclosed in polythene bags.

5.2.8	The samples thus recovered were transported to the laboratory for testing purposes.

5.2.9	Ground water table had been encountered at a depth varying between 7.3m and 8.7m below the existing ground level in the boreholes, during the period of field investigations, i.e October 2022.

6.0	LABORATORY INVESTIGATIONS

6.1	Tests on Soil Samples from Boreholes

6.2	The soil samples brought to the laboratory were subjected to various tests to determine the following properties :

a)	Type of soil and its gradation

b)	Consistency limits

c)	Natural Bulk Density & Water Content

d)	Strength parameters like cohesion, angle of shearing resistance

6.3	In order to determine the above properties, the following tests have been conducted :

a)	Sieve analysis on coarse grained soil fraction

b)	Hydrometer analysis on fine grained soil fraction

c)	Atterberg Limits namely Liquid and Plastic Limits

d)	Natural Density and Water Content

e)	Triaxial compression tests

6.4	Chemical Analysis

6.4.1	Chemical analysis has been conducted on water samples collected from the boreholes to determine the pH-value and the presence of salts harmful to reinforced cement concrete construction namely Chloride and Sulphate contents.

7.0	RESULTS & ANALYSIS

7.1	Presentation of Results

7.1.1	The results of the boreholes investigations have been presented in the form of soil profile tables.

7.1.2	The soil profile tables indicate the following:

a)	Standard penetration test values at various depths

b)	Soil description identifying the type of soil

c)	Grain size analysis indicating composition of subsoil

d)	Atterberg limits

e)	Natural density and water content

f)	Triaxial test results

7.2	Soil Profile

7.2.1	A perusal of the data presented in the soil profile tables indicates that the subsoil mainly consists of the following three strata in the six boreholes:

a)	Stratum - I :	Clayey sandy silt / sandy clayey silt with occasional gravel

b)	Stratum - II :	Silty sand with occasional clay and gravel

c)	Stratum - III :	Sand with silt and occasional gravel / sand with traces of silt

7.2.2	The thickness of the three strata in the six boreholes are as follows :

BH. No.	Strata (depth in m : from : to)
Stratum - I	Stratum - II	Stratum - III
1
2
3
4
5
6

7.2.3	The above results show that :

a)	Stratum - I consisting predominantly of silty soils with varying percentages of clay and sand, is predominant beyond a depth of about 4m down to the maximum depth investigated i.e 30m below the existing ground level except for random layers of Stratum - II in between.

b)	Stratum - II consisting predominantly of sandy soils with significant percentages of silt and occasional clay and gravel, has been encountered in layers down to a maximum depth of about 5m below the existing ground level.

c)	Stratum - III consisting of predominantly of sandy soils has been encountered down to a maximum depth of about 4.5m below the existing ground level.

7.3	Soil Composition

7.3.1	The grain size distributions of the soil samples in the six boreholes have been presented in the form of grain size analysis curves in figs. 5a to 5m.

7.3.2	The variations in the grain size distributions in each of the three strata in the six boreholes are as follows:

a)	Stratum - I: Clayey sandy silt / sandy clayey silt with occasional gravel

BH. No.	Gravel (%)	Sand (%)	Silt (%)	Clay (%)
b)	Stratum - II: Silty sand with occasional clay and gravel

BH. No.	Gravel (%)	Sand (%)	Silt (%)	Clay (%)
1
2
3
4
5
6

c)	Stratum - III: Clayey sandy silt with occasional gravel/ gravelly sandy silt

BH. No.	Gravel (%)	Sand (%)	Silt (%)	Clay (%)
1
2
3
4
5
6
7.3.3	The above results indicate that :

a)	Stratum - I consists of about ......% to .......% silt, ......% to .........% of sand with rest of the soil matrix consisting of clay and gravel.

b)	Stratum - II consists of about .....% to ......% of sand, .......% to ........% of silt with occasional clay and gravel.

c)	Stratum - III consists of an average of about ........% sand and .........% of silt with occasional gravel.

7.4	Natural Density and Water Content

7.4.1	The natural bulk densities, water contents and dry densities in the six boreholes vary as follows :

BH. No.	Bulk Density

(g/cm3)	Water Content

(%)	Dry Density

(g/cm3)
1
2
3
4
5
6

7.4.2	The dry densities of the soil have also been presented in the form of plots of dry density vs depth for the seventeen boreholes conducted, in figs. 3a to 3d.

7.4.3	The above results indicate that the subsoil is in a loose to medium dense state down to about 8m depth below which the subsoils is in a medium dense state down to the depth investigated.

7.5	Atterberg Limits

7.5.1	The Atterberg limits indicate that the subsoil is generally non-plastic down to about 4m depth below which the subsoil is low plastic down to the maximum depth investigated except for occasional thin layers of non-plastic soils in between. The variation in the Atterberg limits in the Stratum -III are as follows:

a)	Liquid limit (LL) %	:	23 - 32

b)	Plastic limit (PL) %	:	10 - 20

7.6	Standard Penetration Test Values (N-values)

7.6.1	The observed Standard Penetration Test values (N-values) vary between 5 and 69 as indicated in the soil profile tables and as also shown in the figs. 4a & 4b wherein the observed N-values have been plotted with respect to depths.

7.6.2	The above results indicate that the subsoil is in a loose to medium dense state down to about 8m depth below which the subsoils is in a medium dense state down to the depth investigated.

7.7	Triaxial Test Results

7.7.1	The results of triaxial tests are indicated in the respective soil profile tables. These results have been considered in providing the recommendations. The results of the triaxial tests in the form of shear strength parameters i.e. angle of internal resistance ( ) and cohesion (c) varies as follows :

a)	Angle of internal resistance	:	23° - 31°

b)	Cohesion (kg/cm2)	:	0.02 - 0.13

7.8	Compiled Soil Profile

7.8.1	An overview of the results and their analysis has been presented in the form of a compiled soil profile (figs. 2a & 2b).

7.8.2	The above figure shows the various strata encountered and their thicknesses in each of the boreholes and also gives the soil composition and the observed N - values at various depths.

7.9	Chemical Analysis

7.9.1	The results of the chemical analysis conducted on soil samples collected from the boreholes, for determining the presence of any harmful salts which can have adverse effects on concrete construction works, are as follows :

Borehole	pH value	Chloride Content (ppm)	Sulphate Content (ppm)
BH1	7.5	54	62
BH6	7.5	93	82
IS LIMITS
pH value	Not less than 6
Chloride content (ppm)	Maximum 500 ppm
Sulphate content (ppm)	Maximum 400 ppm
7.9.2	The above results indicate that the soil encountered in the boreholes shall not have any aggressive effect on normal concrete construction works.

8.0	DESIGN CRITERIA

8.1	Design Parameters

8.1.1	The parameters required for the design of the foundation system for the proposed structures are:

a)	Type of foundation to be adopted

b)	Depth at which the foundations have to be laid

c)	Allowable bearing pressure on the soil/rock at the foundation level

8.1.2	On the basis of the analysis of the results of the investigations, the required design parameters have been arrived at as given in the following sections.

8.2	Type of Foundation

8.2.1	The type of foundation depends upon the following :

a)	Subsoil/rock conditions

b)	Type of structures

c)	Configuration of loading points

d)	Loading intensity on each column at the foundation level

8.2.2	The proposed structures are Institutional buildings consisting of one basements, stilt and ten upper floors. Considering this, heavy loads can be anticipated on the foundations.

8.2.3	The results of the investigations have indicated that the subsoil is in a loose to medium dense state down to about 8m depth below which the subsoils is in a medium dense state down to the depth investigated.

8.2.4	In view of the above, the proposed structures can be supported over Raft Foundations.

8.3	Depth of Foundations

8.3.1	The minimum depth of foundation depends upon the following factors :

a)	Top filled-up strata / loose soil, if any

b)	Adequate depth of soil above founding level, to ensure mobilization of full safe bearing capacity

c)	Adequate depth of soil strata below founding level of requisite strength to mobilize the safe bearing capacity

8.3.2	The results of the investigations have shown that the subsoil, below the likely founding level is in a loose to medium dense state down to deeper depths.

8.3.3	Considering the above, and also that the proposed structures have one basement with floor level of the lower basement resting at a depth of about 4m below the existing ground level, the foundations of the proposed structures can be placed at a depth between 5m and 6m below the existing ground level.

8.3.4	However for minor structures at ground level, the foundations can be placed at a depth of 1.5m below the existing ground level.

8.3.5	The soil available at the founding level will either be Yellowish brown clayey sandy silt or sandy soils.

8.4	Allowable Bearing Pressures

8.4.1	Allowable bearing pressure depends upon the allowable settlements. Allowable settlements of 75mm and 50mm have been considered to evaluate the allowable bearing pressures for Raft Foundations and Isolated/Strip Footings, respectively.

8.4.2	Allowable bearing pressure has been evaluated by :

a)	Shear failure criterion using average soil data

b)	Settlement criterion taking SPT values

8.4.3	On the basis of the above analysis, the following recommendations regarding the net allowable bearing pressure are being made :

a)	Raft Foundation (for Institutional Buildings)

Net allowable bearing pressure of 18 t/m2 and gross allowable bearing pressure of 26t/m2 can be adopted for an allowable settlement of 75mm at above recommended depths.

b)	Isolated/ Strip Footings (for Minor Structures at Ground Level)

Net allowable bearing pressure (A.B.P.) for various widths of Isolated/Strip Footings for an allowable settlement of 50mm

Width of foundation (m)	1.5	3	>4.5
Net Allowable Bearing Pressure (t/m2)

RECOMMENDATION

9.1	Type of Foundations

a)	Raft Foundations (for Institutional Buildings)

b)	Isolated/ Strip Footings (for Minor Structures at Ground Level only)

a)	For Raft Foundations (for Institutional Buildings)

between 5m and 6m below the existing ground level (considering the floor level of the lower basement resting at a depth of 4m below the existing ground level)

b)	For Isolated/ Strip Footings (for Minor Structures at Ground Level)

1.5m below the existing ground level

9.3	Allowable Bearing pressure

a)	For Raft Foundation (for Commercial Buildings)

Net allowable bearing pressure of 18 t/m2 and gross allowable bearing pressure of 26t/m2 can be adopted for an allowable settlement of 75mm at above recommended depths.

b)	Isolated / Strip Footings (for Minor Structures at Ground Level)

Net allowable bearing pressure (A.B.P.) for various widths of Isolated/Strip Footings for an allowable settlement of 50mm

Width of foundation (m)	1.5	3	>4.5
Net Allowable Bearing Pressure (t/m2)

9.4	Modulus of Subgrade Reaction (k-value)

9.4.1	Modulus of sub-grade reaction (k-value) for a 30 x 30cm plate size or 30cm wide beam, of 1.5 kg/cm³ can be adopted for design of Raft Foundations laid at a depth between 5m and 6m below the existing ground level.

9.4.2	The modulus of sub-grade reaction (k-value) given above is based on Standard Penetration Test values (N-values) as per the guidelines of article B-1.1 , clause 3.1(F) of appendix B, IS: 2950(part I) -1981.

9.5	Excavations

9.5.1	The excavations down to above mentioned depths can be carried out by ordinary methods by providing the necessary side slopes.

9.5.2	However, if sufficient space for providing the necessary side slope for deep excavations will not be available, adequate measures in the form of providing properly designed shoring system, have to be taken to ensure safety against failure of the sides of the excavations. The soil parameters may required for the design of shoring system are given below :

Soil Layer thickness below EGL

(m)	Bulk Density

' ' (g/cm3)	Cohesion,
'c'

(kg/cm2)	Angle of Shearing Resistance

' ' (degree)