Indirect Methods

Electrical Resistivity Methods

Seismic Refraction Methods

Standard Penetration Test

Bore Hole

Split Spoon Sampler

Tripod

65 kg Hammer

750mm

Cone Penetration Test

Bearing capacity of soil

• Bearing capacity is the power of foundation soil to hold the forces from the superstructure without undergoing shear failure or excessive settlement.

Super Structure

Foundation

Foundation Soil

Ground Level

• Ultimate Bearing Capacity (qf) : It is the maximum pressure that a foundation soil can withstand without undergoing shear failure.

• Net ultimate Bearing Capacity (qn) : It is the maximum extra pressure (in addition to initial overburden pressure) that a foundation soil can withstand without undergoing shear failure.

qn = qf – qo

Here, qo represents the overburden pressure at foundation level and is equal to үD for level ground without surcharge where ү is the unit weight of soil and D is the depth to foundation bottom from Ground Level.

• Safe Bearing Capacity (qs) : It is the safe extra load the foundation soil is subjected to in addition to initial overburden pressure.

• Here F represents the factor of safety.

on

s qF

qq

• Allowable Bearing Pressure (qa) : It is the maximum pressure the foundation soil is subjected to considering both shear failure and settlement.

Method of determining of SBC of soil

• Plate load test: it is a field test for determining the ultimate bearing capacity of soil and the likely settlement under a given load.

• The Plate Load Test basically consists of loading a steel plate placed at the foundation level and recording the settlements corresponding to each load increment.

• The test load is gradually increased till the plate starts to sink at a rapid rate. The total value of load on the plate in such a stage divided by the area of the steel plate gives the value of the ultimate bearing capacity of soil.

Gravity loading method

Reaction Truss Method