Numerical Modelling of Seismic Behaviour of Earth-Retaining Walls

Student: Pathmanathan Rajeev
Supervisors: Prof Paolo Pinto, Dr Carlo Lai

ABSTRACT

In current engineering practice the design methods for earth retaining walls under seismic conditions are mostly empirical. Dynamic earth pressures are calculated assuming prescribed seismic coefficient acting in the horizontal and vertical directions using the concept of limit equilibrium Mononobe- Okabe method. A research investigation has been undertaken to determine the dynamically-induced lateral earth pressures on a flexible diaphragm wall, a flexible cantilever wall, and a gravity retaining wall with cohesionless and cohesive backfills. Additionally, this report gives information about the point of application of total and incremental dynamic forces, the deformation or displacement of the wall and also the bending moment and shear force envelops for structural design of the wall. A series of non-linear dynamic finite element numerical analyses have been performed using DIANA (DIsplacement ANAlyzer). The analyses consisted of the incremental construction of the wall and placement or excavation of the backfill, followed by dynamic response analyses, wherein the soil was modelled as elasto-plastic. Particular attention has been devoted to ground excitation and determination of the wall and soil model parameters. The results obtained with DIANA have been compared through a series of benchmark tests with those determined using simplified techniques for computing dynamic earth pressure, co-seismic and post-seismic wall displacements.

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