SAFE BEARING CAPACITY VALUES OF DIFFERENT SOILS & ROCKS

The safe bearing capacity of the soil should be determined on the basis of soil test data or by performing some field tests like standard penetration test or plate load test etc.


However, in the absence of soil test data, the safe bearing capacity (SBC) values, given in the following table, can be used as a guide for preliminary analysis.


Recommended Values ​​of Safe Bearing Capacity for Preliminary Analysis

no serial number

rock or soil type

safe bearing capacity

(kN/m)2,

(kg/cm2,

rocks

1 Rocks (hard) without lamination and defects, for example granite, trap and diorite 3300 33
2 Laminate rocks, for example sandstone and limestone in sound conditions 1650 16.5
3 Scattered and broken bed rock and hard shale, remnant deposits of cemented material 900 9
4 soft stone 450 4.5

non-cohesive soil

5 Gravel, a sand and gravel mix, compacts and provides high resistance to penetration during excavation by tools. (see note 5) 450 4.5
6 Coarse sand, dense and dry (with groundwater level at a depth greater than the width of the foundation below the bottom) 450 4.5
7 medium sand, compact and dry 250 2.5
8 fine sand, silt (dry lumps that are easily crushed with fingers) 150 1.5
9 loose gravel or sand gravel mixture; loose coarse to medium sand, dry (see Note 5) 250 2.5
10 fine sand, loose and dry 100 1

cohesive soil

1 1 Deep bed soft shale, hard or hard soil, dry 450 4.5
12 Medium clay, easily indented with thumb nail 250 2.5
13 A mixture of moist clay and sand clay that can be indented with strong thumb pressure 150 1.5
14 Soft clay indented with moderate thumb pressure 100 1.0
15 very soft clay that can be rammed several centimeters with the thumb 50 0.5
16 Black cotton soil or other shrinkable or expansive soil (50 percent saturation) in dry conditions (see Note 2) Determination will be done after site investigation
17 Pete (see Notes 2 and 3)
18 Filled ground (see Notes 4 and 5)

notes

  1. The values ​​given in the above table can be adopted only for the design of insignificant and light loaded structures.
  2. No normalized value for safe bearing capacity can be given for this type of soil. In such area, adequate site investigation needs to be done and expert advice should be sought.
  3. Peat may be in a very soft spongy state or may be quite firm and compact. While the final bearing capacity can be high in compact cases, very large consolidation settlements also occur under small pressures and the movement continues for decades.
  4. The strength of the ground that remains depends on the nature of the material, its depth and age, and the methods used to strengthen it.
  5. The compactness or looseness of the non-cohesive material can be determined by driving a wooden picket of dimensions 5 cm x 5 cm x 70 cm with a pointed point. The picket is pushed vertically into the soil by a person’s entire weight and if the picket’s penetration exceeds 20 cm, it is considered to be in a loose state.
  6. The safe bearing capacity value may be increased by an amount equal to the weight of the material removed above the bearing level which is the base of the foundation.


Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.