Skin Friction Integration in Subgrade Reaction Models for Diaphragm Walls

A formulation is presented to incorporate the friction stresses exerted by the soil on diaphragm walls modeled using the subgrade reaction method (SRM). The wall structure is discretized with beam finite elements, and the soil–structure friction is represented by equivalent distributed moments and axial forces. The coupling between axial and lateral displacements is introduced at the soil–structure interaction level through the constitutive law for tangential stresses. The resulting nonlinear problem is solved using the Newton–Raphson method, and the adopted iteration strategies are discussed. A benchmark case of an embedded cantilever wall is analyzed. The SRM predictions are compared with results from the FEM, reduced-scale laboratory experiments, and field measurements of a monitored wall. A sensitivity analysis highlights the influence of interface parameters on the mechanical response of the embedded wall. A large data set is generated to quantify the impact of including or neglecting skin friction along the wall. Neglecting these effects leads to conservative (safer) designs but also to significant oversizing of diaphragm walls.