Question

Can the effective friction angle (ϕ’) be used to determine the active thrust from a saturated clay? describe the calculation procedure if possible. unless, state a suitable method.

Answer 1

Yes, friction angle can be used to determine the active thrust from a saturated clay using Rankine's method.

= effective friction angle

Active earth pressure coefficient KA =   

For purely cohesive clay, =0

KA = 1

Critical height of clay layer H0 = 2c / (KA)1/2

Upto this height pressure is zero. So base pressure should be calculated from H0 to the required depth.

Base pressure at a depth h from the top surface of soi can be calculated as:

Area of the pressure distribution diagram gives the total thrust acting on the clay layer.