The document summarizes testing conducted to determine the bearing capacity of soil for silo foundations at different depth levels. Rock mass rating (RMR) was calculated using parameters like rock quality, discontinuity spacing and conditions, water conditions, and orientation. RMR values between 27-44 were obtained at different levels, corresponding to safe bearing capacities of 78.21-171.37 tonnes/square meter. Uniaxial compressive strength testing of rock cores yielded average strengths of 49.06, 51.48, and 52.09 N/square mm at different levels.

1. SSTPP – Malwa- II
Bearing Capacity of Soil with
RMR Method
By: Amardeep Singh

2. Team Person Responsible: Larsen & Toubro Ltd
Package : Silo Foundation
Description :
• The test was conducted to confirm the bearing capacity of soil for Silo Foundations.
• The testing was conducted as per IS: 13365(PART-1), IS: 12070-1987, IS: 516.
• In house calculation was done with client consents which was later verified by third party.
• The basic aim of sharing the methodology is to circulate information amongst the L&T
Power-QMCC & other departments for reference purpose.

3. Scope
 Determining of the Class of Rock mass
based on the geo-mechanics
classification system
 Also known as the Rock Mass
Rating(RMR).
 Cohesion, angle of internal friction
and elastic modulus can be
determined.
Field Data Required
 Uniaxial Compressive Strength of
Intact Rock Material
 Rock Quality Designation
 Spacing of Discontinuities
 Condition of Discontinuities
 Ground Water Condition
 Orientation of Discontinuities

4. Uniaxial Compressive Strength of Intact Rock Material
Rock Quality Designation(RQD)

5. Spacing of Discontinuities
Condition of Discontinuities

6. Ground Water Condition
Orientation of Discontinuities

7. Boring at Silo Foundation for Rock Sample

8. Sample of the Rock Layer by Layer

9. Rock Mass Rating
Location Ash Silo N-2267.686
Level -4 m to -7 m E-1057.873
s.
no.
description condition
rating as per IS 13365 (part
-1) ANNEX B
1 Strength Average 4
2 Rock Quality Description(RQD) 66.67 (fair) 13
3 Spacing of discontinuities close 8
4 condition of discontinuities 5 mm thick soft gauge 0
5 Groundwater condition dripping 4
6 Orientation of discontinuities favorable -2
RMR 27
RMR value is 27 therefore as per IS 12070-1987 Table no. 3 SBC is 78.210 t/sqm at -4 m
to -7 m level
Rock Mass Rating
Location Ash Silo N-2267.686
Level -7 m to -10 m E-1057.873
s.
no.
description condition
rating as per IS 13365 (part
-1) ANNEX B
1 Strength Average 4
2 Rock Quality Description(RQD)
75.33 (good) 17
3 Spacing of discontinuities close 8
4 condition of discontinuities
5 mm thick soft gauge 0
5 Groundwater condition dripping 4
6 Orientation of discontinuities favourable -2
RMR 31
RMR value is 31 therefore as per IS 12070-1987 Table no. 3 SBC is 92.89 t/sqm at -7 m to
-10 m level
Rock Mass Rating
Location Ash Silo N-2267.686
Level -10 m to -13 m E-1057.873
s. no. description condition
rating as per IS 13365 (part -
1) ANNEX B
1 Strength Average 4
2 Rock Quality Description(RQD) 91.5 (excellent) 20
3 Spacing of discontinuities close 8
4 condition of discontinuities
slickensides wall rock
surface of 1-5 mm thick
10
5 Groundwater condition dripping 4
6 Orientation of discontinuities favourable -2
RMR 44
RMR value is 44 therefore as per IS 12070-1987 Table no. 3 SBC is 171.37 t/sqm at -10 m to -
13 m level

10. Core Strength
As per IS 516
H/D 2 1
Corr.
Factor
1 0.89
Location: Ash Silo N-2267.686
E-
1057.873 Date:
24-08-
2016
S.
no.
Core
height (H)
Core Dia
(D)
H/D
ratio
Load Strength
Correction
factor as
per IS
516
corrected
strength
mm mm KN N/sqmm N/sqmm
level = -4 m to -7 m
1 95 50 1.90 95 48.36 0.989 47.83
2 86 50 1.72 100 50.91 0.969 49.34
3 92 50 1.84 100 50.91 0.982 50.01
Avg. 49.06
level = -7 m to -10 m
1 97 50 1.94 105 53.45 0.993 53.10
2 78 50 1.56 105 53.45 0.952 50.87
3 96 50 1.92 100 50.91 0.991 50.46
Avg. 51.48
level = -10 m to -13 m
1 96 50 1.92 110 56.00 0.991 55.51
2 75 50 1.50 105 53.45 0.945 50.51
3 94 50 1.88 100 50.91 0.987 50.24
Avg. 52.09

11. Rock Mass Rating
Location Ash Silo N-2303.370
Level -4 m to -7 m E-1063.143
s.
no.
description condition
rating as per IS 13365
(part -1) ANNEX B
1Strength Weak 2
2
Rock Quality
Description(RQD)
6.33 (very poor) 3
3Spacing of discontinuities very close 5
4condition of discontinuities
5 mm thick soft
gauge
0
5Groundwater condition dripping 4
6
Orientation of
discontinuities
fair -7
RMR 7
RMR value is 7 therefore as per IS 12070-1987 Table no. 3 SBC is 45.25
t/sqm at -4 m to -7 m level
Rock Mass Rating
Location Ash Silo N-2303.370
Level -7 m to -10 m E-1063.143
s.
no.
Description Condition
Rating as per IS 1336
(part -1) ANNEX B
1Strength Weak 2
2
Rock Quality
Description(RQD)
52 (fair) 13
3Spacing of discontinuities close 8
4condition of discontinuities
5 mm thick soft
gauge
0
5Groundwater condition dripping 4
6Orientation of discontinuities favourable -2
RMR 25
RMR value is 25 therefore as per IS 12070-1987 Table no. 3 SBC is 71.47 t/sqm
at -7 m to -10 m level
Rock Mass Rating
Loacation Ash Silo N-2303.370
Level -10 m to -14 m E-1063.143
s.
no.
description condition
rating as per IS 13365
(part -1) ANNEX B
1Strength Strong 7
2Rock Quality Description(RQD) 87.5 (good) 17
3Spacing of discontinuities close 8
4condition of discontinuities
slickensided wall rock
surface of 1-5 mm
thick
10
5Groundwater condition dripping 4
6Orientation of discontinuities favourable -2
RMR 44
RMR value is 44 therefore as per IS 12070-1987 Table no. 3 SBC is 171.37 t/sqm
at -10 m to -13 m level

12. Core Strength
As per IS 516
H/D 2 1
Corr.
Factor
1 0.89
Location: Ash Silo
N-
2303.370
E-
1063.143 Date:
26-08-
2016
S.
no.
Core
height
(H)
Core Dia
(D)
H/D
ratio
Load Strength
Correctio
n factor
as per IS
516
corrected
strength
mm mm KN N/sqmm N/sqmm
level = -4 m to -7 m
1 94 50 1.88 35 17.82 0.987 17.58
2 93 50 1.86 30 15.27 0.985 15.04
3 88 50 1.76 35 17.82 0.974 17.35
Avg. 16.66
level = -7 m to -10 m
1 96 50 1.92 35 17.82 0.991 17.66
2 88 50 1.76 35 17.82 0.974 17.35
3 86 50 1.72 40 20.36 0.969 19.74
Avg. 18.25
level = -10 m to -14 m
1 92 50 1.84 145 73.82 0.982 72.52
2 90 50 1.80 155 78.91 0.978 77.17
3 89 50 1.78 160 81.45 0.976 79.48
Avg. 76.39

13. THANK YOU