In Rankine's Theory, what are the values of Ka and Kp in pure clay?

In Rankine's Theory, the values of the lateral earth pressure coefficients Ka (active earth pressure coefficient) and Kp (passive earth pressure coefficient) for purely cohesive soils, such as clay, are derived based on the assumptions of limit equilibrium and horizontal backfill conditions. For pure clay, which is characterized by cohesive strength, the values of Ka and Kp can be evaluated based on the equation:

Ka = tan²(45° - φ/2) and Kp = tan²(45° + φ/2)

When considering pure clay where the angle of internal friction φ is considered to be zero (which is valid for undrained conditions in saturated clay), these equations simplify. Thus:

Ka = tan²(45°) = 1.0 Kp = tan²(45°) = 1.0

This means that for pure clay, both the active and passive lateral earth pressure coefficients are equal to 1.0, confirming the values for Ka and Kp in this context.

Understanding these principles is crucial in earth pressure calculations, ensuring that structures retain their stability against soil loads in the field of civil engineering and foundation design.