NUMERICAL ANALYSIS OF SMALL-SCALE EARTH RETAINING STRUCTURES DURING LIQUEFACTION

Abstract

In repair works for underground pipelines, lightweight sheet piles are frequently used for excavations with depths of approximately 1–2 m. Because these structures are temporary and small in scale, the embedment length is generally short to facilitate rapid and easy construction. This study performs numerical analyses of small-scale earth-retaining structures under seismic conditions. The target ground is assumed to be sandy and saturated soil in a coastal area, and soil liquefaction is considered in the analysis. The target structure is assumed to have an excavation depth of 2.0 m and an embedment depth of 0.5 m. Based on this reference model, additional simulations were conducted to investigate the effects of four factors: (1) the presence or absence of liquefaction, (2) variations in strut spacing, (3) the application of surcharge loads, and (4) differences in input seismic motions. The results indicate that liquefaction causes uplift of the entire structure and increases the stresses acting on structural components such as struts and walers. The stresses induced in the structural members increase with both increasing strut spacing and higher peak accelerations of the input seismic motion. Furthermore, when a surcharge load is applied only to one side of the ground surface, asymmetric ground deformation occurs, resulting in deformation of the excavation space. Doubling the strut spacing, applying a surcharge load on the ground surface, and the occurrence of an L2-class earthquake all resulted in axial forces in the strut exceeding the allowable values.