Analysis For Earthquakeinduced Cumulative Displacement Of Gravity Retaining Structures

Gravity retaining structures are widely used in engineering practice. Investigations of earthquake damage cases show that along with failure of retaining walls there is large displacement. The aseismic research about gravity retaining structures deals with seismic soil pressure, seismic wall strength checking and seismic stability. Displacement-based stability design and checking of retaining structures urgently need a convenient method for seismic displacement estimation. Based on the researches about dynamic soil-wall interaction, dynamic nonlinearity of soil and seismic soil pressure considering cohesive backfill, the cumulation of displacement and final permanent displacement of gravity retaining structures are investigated, and a method for estimating seismic displacement of gravity retaining structures is developed. The main progress is involved in 5 aspects, as follows.1. Simultaneously considering sliding and rocking modesRetaining walls experience coupling movements of sliding and rocking modes during earthquakes. Two DOF of rigid wall, including horizontal sliding and rocking about projection of wall mass center on base edge, are involved in the equation of motion. The cumulative time histories of sliding and rocking are then obtained by integrating the equation of motion in time domain. Therefore, the disadvantage as in Newmark block method, by which only sliding displacement can be computed, is improved.2. Considering nonlinearity of foundation soilThe displacement of gravity retaining structures is large, and the average dynamic shear strain level in foundation soil is high under strong ground motion. With the growth of shear strain, soil moduli decline and damping ratios mount up. When the equation of motion is numerically integrated, the nonlinearity of the soil-wall system is expressed by iterative technique during each time step.