Panos Kloukinas

Simple wave solution for seismic earth pressures on nonyielding walls

AbstractDesign of retaining walls for earthquake action is traditionally performed by limit analysis procedures—notably the classical solution of Mononobe-Okabe and its variants. Fundamental assumptions of these methods are (1) the static nature of seismic excitation, (2) the compliance in sliding and/or rocking of the base of the wall, (3) the shear failure of the backfill and the soil-wall interface, and (4) the prespecified point of application of soil thrust. Given the restrictive nature of these assumptions, alternative solutions based on wave-propagation theory have been developed that do not require failure of the backfill and thereby are applicable to nonyielding walls. Because of the complex mathematics involved, the use of these solutions in practice appears to be limited. A special integration technique inspired from the seminal work of Vlasov and Leontiev is presented, which simplifies the analysis by providing closed-form solutions suitable for practical use.

Experimental Investigation of Dynamic Behavior of Cantilever Retaining Walls

The dynamic behaviour of cantilever retaining walls under earthquake action is explored by means of 1-g shaking table testing, carried out on scaled models at the Bristol Laboratory for Advanced Dynamics Engineering (BLADE), University of Bristol, UK. The experimental program encompasses different combinations of retaining wall geometries, soil configurations and input ground motions. The response analysis of the systems at hand aimed at shedding light onto the salient features of the problem, such as: (1) the magnitude of the soil thrust and its point of application; (2) the relative sliding as opposed to rocking of the wall base and the corresponding failure mode; (3) the importance/interplay between soil stiffness, wall dimensions, and excitation characteristics, as affecting the above. The results of the experimental investigations were in good agreement with the theoretical models used for the analysis and are expected to be useful for the better understanding and the optimization of earthquake design of this particular type of retaining structure.

Distribution of Seismic Earth Pressures on Gravity Walls by Wave-Based Stress Limit Analysis

A closed-form stress plasticity solution is presented for earthquake-induced earth pressures and distribution of these pressures on inflexible retaining walls. The solution is essentially an approximate yield line approach that over- and under-estimates active and passive pressures, respectively. Results are presented in the form of dimensionless graphs and charts that elucidate the salient features of the problem. Compared to Mononobe-Okabe equations, the proposed solution is simpler, more accurate and safe. In addition, it provides a rational means for determining the distribution of limit thrusts on the wall. It is shown that the pseudo-dynamic seismic problem does not differ fundamentally from the gravitational one, as the former can be derived from the latter by means of a revolution of the reference axes. In the second part of the paper, the solution is extended to determine the distribution of limit pressures on a gravity wall by means of simple wave equations. The proposed approach has advantages over earlier efforts by Steedman and Zeng, as it satisfies the stress boundary conditions of the problem.

EXPERIMENTAL INVESTIGATION OF DYNAMIC BEHAVIOUR OF CANTILEVER RETAINING WALLS

The dynamic behaviour of cantilever retaining walls under earthquake action is explored by means of 1-g shaking table testing, carried out on scaled models at the Bristol Laboratory for Advanced Dynamics Engineering (BLADE), University of Bristol, UK. The experimental program encompasses different combinations of retaining wall geometries, soil configurations and input ground motions. The response analysis of the systems at hand aimed at shedding light onto the salient features of the problem, such as: (1) the magnitude of the soil thrust and its point of application; (2) the relative sliding as opposed to rocking of the wal land the corresponding failure mode; (3) the importance/interplay between soil stiffness, wall dimensions, and excitation characteristics, as affecting the above. The results of the experimental investigations are in good agreement with the theoretical models used for the analysis and are expected to be useful for the better understanding and the optimization of earthquake design of this type of retaining structure.