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[subha_mukherjee]

First soil layer is of thickness of 6m having C=1.5t/m2,phi=28 degree, desiity=1.88t/m2,N=15-27,e0=0.538. Second soil layer is of thickness 3m having phi=34 degree,density=1.9t/m2,Ncorr=46-58.A 3mx3m foundation is placed 1.5m below GL. Will the foundation undergo General shear failure or local  shear failure?

[vikram.jeet]

STRUCTURE AND GEOTECHNICAL COMBINE

ULTIMATE BC OF SHALLOW FOUNDATIONS ON SOILS
FOR COHESION LESS SOILS C=0
This needs to be calculated based on Relative density (RD)index of cohesion soil

If RD > 70% , Void ratio less than 0.55 , Dense Condition - GENERAL SHEAR FAILURE EQUATION TO BE USED

IF RD < 20% , VOID RATIO >0.75 , CONDITION-  LOOSE -- USE LOCAL SHEAR FAILURE EQUATION

FOR INTERMEDIATE VALUE OF RELATIVE DENSITY , WORK OUT FROM BOTH EQUATIONS AND INTERPOLATE BASED ON RD.

[vikram.jeet]

Idea is :-

Loose,, Soft soils -- More prone to LSF

Dense Soils  - Less prone to LSF