A site is underlain by a soil that has a unit weight of 118 lb/ft3. From laboratory shear strength tests that closely simulated the field conditions, the total stress parameters were measured to be C total = 250 lb/ft2 and φ total = 29°. Estimate the shear strength on a horizontal plane at a depth of 12 ft below the ground surface at this site in lbs/ sq ft

the shear strength at a depth of 12 ft is 1034.9015 lb/ft²

Explanation:

Given that;

Weight of soil r = 118 lb/ft³

stress parameter C = 250 lb/ft²

φ total = 29°

depth Z = 12 ft

The shear strength on a horizontal plane at a depth of 12ft

ζ = C + δtanφ

where δ = normal stress

normal stress δ = r × z = 118 × 12 = 1416

so

ζ = C + δtanφ

ζ = 250 + 1416(tan29°)

ζ = 250 + 1416(tan29°)

ζ = 250 + 784.9016

ζ = 1034.9015 lb/ft²

Therefore the shear strength at a depth of 12 ft is 1034.9015 lb/ft²