Study on rational procedures to evaluate seismic stability of retaining walls

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In order to establish rational procedures to evaluate seismic stability of retaining walls, back analyzes of retaining walls for railway embankments damaged by the 1995 Hyogoken-nanbu earthquake, shaking and tilt table model tests on a variety of retaining walls, and investigations to evaluate active earth pressures at high seismic load levels were conducted.The back analyzes revealed that there exists a big gap between the design horizontal coefficients used in the current pseudo-static seismic design approaches for retaining walls and the peak ground acceleration divided by the gravitational acceleration experienced by a number of RWs during the 1995 Hyogo-ken-nambu Earthquake. In the tilt table tests, irrespective of wall type, a failure plane or a set of failure planes developed in the backfill associated with the active failure in the backfill, followed by the ultimate failure or collapse of wall only at a slightly larger tilting angle. On the other hand, in the shaking table tests, the ultimate failure or collapse of wall occurred at a much later stage associated with relative large deformation and displacement of wall occurring after the first active failure plane developed in the backfill.Based on the above results, a modified pseudo-static and limit-equilibrium approach to evaluate active earth pressure at high seismic load levels is proposed. Although it is similar to the Mononobe-Okabe method, the proposed method considers the effects of strain localization in the backfill soil and associated post-peak reduction in the shear resistance from peak to residual values along a previously formed failure plane.