A research study submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M. Eng.) - Asian Institute of Technology, 1986

The permanent displacement of ground due to liquefaction during earthquakes poses problems to lifeline systems such as water, gas and electricity supplies, sewerage lines, roads and bridges. Many important constructions, particularly port facilities are build on horizontal backfill grounds of retaining structures. Large permanent displacements of this type of ground can occur due to the forward movement of the retaining structures during earthquakes. In this study, the seismic displacement behaviour of sheet-pile bulkheads, which are widely used as waterfront retaining structures, is examined in detail. A parametric study, i.e. the effects of factor of safety used in the static design, angle of friction of the backfill soil, water table etc. on the the seismic resistance of the bulkheads, is reported. The most important factor appears to be the factor of safety used in the static design. A general computer program is developed using the principle proposed by Newmark to estimate the permanent displacement of earth and earth retaining structures, once the dynamic resistance to movement is known. A simplified procedure to predict the permanent displacement of the liquefied backfill ground induced by the forward movement of the retaining structure is presented. The proposed method gives reasonable estimation of permanent displacements, uses simple numerical procedure and is very economical for analysis of large areas as compared to existing analysis.