Explain the factors effecting bearing capacity of soil

1. Soil Strength:

The bearing capacity of cohesionless soil and mixed soil increases disproportionately with the increase of the effective friction angle.

2. Foundation Width:

Foundation width affects the bearing capacity of cohesionless soil.

3. Foundation Depth:

The greater the bearing capacity the deeper the foundation.

4. Soil Weight and Surcharge:

The contribution of subsurface and surcharge soil, which are influenced by the water table, to the bearing capacity cannot be ignored.

5. Spacing Between Foundations:

It is recommended to consider minimum spacing between footings, which 1.5 times foundation width, during the design of the foundation in order to avoid a reduction in bearing capacity.

6. Earthquake and Dynamic Motion:

Repeated movements could increase pore pressure in foundation soil and consequently bearing capacity is decreased.

7. Frost Action:

Frost heave in certain soils in contact with water and subject to freezing temperatures or loss of strength of frozen soil upon thawing can alter bearing capacity over time.

8. Subsurface Voids:

The bearing capacity of soil decreases due to subsurface voids that are within a critical depth beneath the foundation.

9. Expansive and Collapsible Soils:

Collapsible and expansive soil can have large strength and bearing capacity when they are fairly dry.

10. Potential Heave:

The potential heave can be determined from the results of consolidometer test which can be performed in accordance with ASTM D 4546. The results of this test are considered in determining the preparation of foundation soils to reduce destructive differential movements and to provide a foundation of sufficient capacity to withstand or isolate the expected soil heave.

11. Soil Reinforcement:

The bearing capacity of soft or weak soil can be increased greatly by installing various forms of reinforcement in the soil like metal ties, strips, or grids, geotextile fabrics, or granular materials.

12. Soil Erosion and Seepage:

Erosion of soil can reduce bearing capacity and can cause foundation failure.