LATERAL DISPLACEMENTS OF COMMONLY FOUND GRAVITY RETAINING WALLS IN SRI LANKA DUE TO SEISMIC ACTION

Gravity type retaining walls have been widely used to retain soil in Sri Lanka. However, it was reported that the performance of gravity type retaining walls during earthquake is poor. In view of the above, it was attempted in this study to develop a methodology to estimate the possible displacements of commonly found gravity retaining walls in Sri Lanka due to expected earthquakes. In addition, it was attempted to recommend an optimum shape for gravity retaining walls to minimize the possible displacements. This work was backed by Mononobe-Okabe theory and Newmark‟s sliding wedge analysis. Using Mononobe-Okabe analysis, threshold acceleration that would cause a relative displacement between retaining wall and soil, was found for different types of retaining walls. Using Newmark‟s method, an analytical model was developed to predict lateral displacements during seismic loadings. Then different acceleration-time histories of earthquakes, which are similar to those observed near Sri Lanka recently, were fed to the developed analytical model and the lateral displacements were found. Gravity retaining walls with a sloping back is found to give the least displacements, compared to the other types such as vertical and battered type gravity retaining walls for same acceleration-time history and to the same ground slope behind the retaining wall