5.
1 PROJECT NO P01
5.1.1 Soil Investigation Report
1 Introduction
There is a proposal for the construction of the building (G+2) at Cochin. To
determine the type of foundation and the bearing capacity of the subsoil, it was decided to
conduct soil investigation. It was decided to conduct Standard penetration test for 1 bore hole
by Rotary drilling method.
2 Scope of Works
a. Mobilization of boring machinery including all accessories, tools and plants and
skilled/unskilled personal necessary for field work.
b. Drilling 1 bore hole /standard penetration test /Rotary drilling Method.
c. Collection of disturbed samples.
d. preparation of soil report based on laboratory experiments and bore log sheet
3 Field Investigations
Table 5.1(i) Bore holes
Number Depth(m) Water Table Level(m from
Ground level)
BH 01 60.00 -0.300
_ _ _
_ _ _
4 Laboratory Investigations
To evaluate the properties of soil following lab tests were conducted
Determination of Density
Determination of Water content of soil
Determination of Specific gravity of soil
Grain size analysis
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Determination of Atterberg’sLimit
Determination of Shear strength parameters using Direct shear test and Triaxial
Apparatus
All Laboratory tests were conducted as per relevant IS Specifications
5 Discussion and Recommendations
Recommendations are based on the assumption that the soil profile found in the
borehole tested is indicative of the entire plot area. Any deviation in soil profile other than
those observed in the borehole tested should immediately be referred to the consultant and
proper modification should be implemented.
Soil Profile
As per instruction of Engineer, it was decided to take one borehole at the site.
In BH-01, the top 0.40m comprise of filled soling. Below this medium to fine sand was
having SPT value of 36, 38, 31, 27&15was noted for every 1.50m depth extending up to a
depth of 8.80m.This was followed by clay with sand and sheldust having SPT value of 0 to 1
was noted extending up to a depth of 17.90m.Below this loose clay having SPT value of 0 to
1 was noted extending up to a depth of 25.80m.
Below this Laterite clay having SPT value of 24, 21, 20&17 15 was noted for every
3m depth extending up to a depth of 38.90m.Below this found Stiff clay with decayed wood
having SPT value of 16, 17&19 for every 3m depth extending up to a depth of 48.10m.Below
this clay sand having SPT value of 50 was noted extending up to a depth of 53.2m.Below this
decayed wood having SPT value of 46 was noted extending up to a depth of 55.1m. Below
this charconic clay with sand (2.7m thick), medium sand (2.2m thick) was noted extending
up to a depth of 60m.Borehole terminated at 60m depth. Water Table was noted at a depth of
0.30m from ground level during the time of investigation. From the study of borehole for
structure following recommendation are made.
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6 Calculations
6.1 Shallow Foundation
6.1.1 Bearing Capacity from Shear Criteria
As per IS 6403-1981 clause 5.1.2, the ultimate net bearing capacity is can be
calculated from equation,
qu =CNcsc dc ic +q(Nq-1)sqdq iq+0.50B g Ng sg dg ig w’
Table 5.1(ii): Bearing Capacity Parameters
Type of Soil cohesion less soil
Type of failure general shear failure
B= 2 L = 2 C=0 phi(ф) 35
Nc= 46.13 sc = 1.3 dc= 1.05 ic= 1
Nq= 33.3 sq= 1.2 dq= 1.02 iq= 1
Ng= 48.03 sg= 0.8 dg = 1.02 ig = 1
w'= 0.5 F.S= 2.5 Df= 1.5 g= 21
qu works out to be 166 T/m2 and qsafe 66 T/m2 for shearcriteria
6.1.2 Shallow Foundation- Bearing Capacity From Settlement Criteria
As per IS 8009(PART1)-1976, the ultimate net bearing capacity was calculated.
Average SPT value of 30 is noted in the zone of influence of pressure (considering a footing
of width 2 m) for settlement of 40mm, qsafe works out to be 29 T/m2 for settlement criteria.
7 Result
Safe bearing capacity of soil = 29 T/m2
Type of Foundation =square footing
Width of foundation =2m
Depth of foundation =1.5m
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