Current Issue

INFLUENCE OF SHEAR BANDING ON THE ACTIVE EARTH PRESSURE OF RETAINING WALLS

Tse-Shan Hsu

Founding President, Institute of Mitigation for Earthquake Shear Banding Disasters

Professor, Department of Civil Engineering, Feng-Chia University, Taiwan R.O.C.

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Hung-Chia Chang

Manager, Civil Engineering Maintenance Section, Maintenance Management Division, 

Port of Taichung, Taiwan Internation Port Corp. LTD., Taiwan, R.O.C.

Abstract

Engineers commonly rely on the Rankine active earth pressure formula, as prescribed in design codes, when designing retaining walls. However, research has demonstrated that retaining walls designed using this approach may be prone to failure under conditions such as heavy rainfall, earthquakes, or even under normal scenarios without wind, rain, or seismic activity. To address this issue, the present study uses the pier caisson-type retaining wall at the Taichung Port in Taiwan, as a case study to investigate the influence of shear banding on the active earth pressure exerted on retaining walls. The key findings are as follows: (1) During significant lateral displacement of the retaining wall toward the seaward side, the soil behind the wall undergoes lateral unloading; as the Mohr circle expands and tangentially intersects the yield envelope, the soil reaches its yield point and enters the plastic range. (2) In a plastic strain-softening model, shear band failure planes develop in the soil behind the wall. In contrast, no such failure planes are observed in a perfectly plastic model. This suggests that soil yielding does not always lead to the formation of shear band failure planes. (3) Significant lateral movement of the retaining wall is required to induce active earth pressure, it is crucial to account for the residual shear strength parameters of the soil, which are determined once strain has sufficiently penetrated the plastic range. Based on these findings, the authors recommend integrating shear banding theory and the corresponding active earth pressure calculation formulas into future design codes to enhance the stability of retaining walls.

Keywords: caisson, retaining wall, shear band, soil liquefaction, strain softening.