A MODIFIED PROCEDURE TO EVALUATE EARTHQUAKE-INDUCED DISPLACEMENT OF SLOPES CONTAINING A WEAK LAYER

A procedure based on the Janbu method for slope stability analysis and Newmark's sliding block method for displacement calculation is proposed to evaluate rationally the earthquake-induced displacement of slopes containing a weak layer. In the procedure, the effects of the irregular geometry of the sliding plane and generation of excess pore water pressure in the weak layer which forms partly the sliding plane are considered. In the computation following the proposed procedure, a negative yield seismic coefficient to induce a safety factor of unity can be obtained because of the effect of excess pore water pressure, while the residual displacement can become a finite value because the sliding plane becomes flatter in general after the slope undergoes a large displacement.