STATIC AND SEISMIC LATERAL EARTH PRESSURES ON RIGID RETAINING STRUCTURES
Abstract
In this study, the applicability of the upper bound technique of limit analysis based on perfect plasticity to the analysis of soil stability problems is evaluated. The study shows that the application of the limit analysis method to soil stability problems in both purely cohesive and cohesionless soils is highly justified. Comparison of results on static active and passive earth pressures based on the limit analysis method with other well-known solutions shows very good agreement between them. However, the limit analysis method is capable of solving more general problems than the others. More importantly, it ensures that the solution is an upper bound to the "exact" solution, which is of practical interest to the designers. Some practical aspects in application of the limit analysis to stability problems in soil mechanics are discussed. The limit analysis method developed for static loads is extended to determining the active and passive earth pressures due to seismic loadings. The cohesion and surcharge effects are also included in the formulation. Comparison of results based on the limit analysis method with those obtained by the well-known Mononobe-Okabe analysis shows very good agreement between them for the active pressure case. For the passive pressure case, the limit analysis gives much lower values of seismic earth pressure than the Mononobe-Okabe analysis does. Extensive parametric studies reflecting the effects of soil parameters, geometry of soil-wall system, and the magnitude and direction of seismic acceleration on the calculated seismic lateral earth pressures are included. Effects of surcharges and cohesion on seismic lateral earth pressures are discussed. Effect of seismic forces on the potential sliding surface and its consequences are also critically reviewed. For convenience in applying the results of this study, earth pressure tables listing the coefficients of active and passive pressure are generated based on the proposed limit analysis method. Charts required for application of the earth pressure tables are also developed. To consider the problem of assessing the point of action of the resultant lateral forces, a modification of the so-called Dubrova method is developed. Results obtained show that the method can be adapted to give reasonable estimates of the point of action for many modes of wall movement, with the exception of the case of rotation about the toe, if the form of the relation between mobilized friction and wall displacement is appropriately formulated. The effect of wall movement on the resultant lateral forces is also investigated. Comparison of results obtained based on the proposed modified Dubrova and limit analysis methods with some other published solutions shows that the agreement between them is acceptable for the cases of translation and rotation about the top. Some well-known earth pressure theories suitable for the determination of seismic lateral earth pressures are compared with the proposed limit analysis and modified Dubrova method both qualitatively and numerically. Finally, recommendations for the selection of earth pressure theories in the design of rigid retaining structures in seismic environments are given.
Degree
Ph.D.
Subject Area
Civil engineering|Geographic information science
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