A Computational Method for Residual Excess Pore Pressure Response in Sand Under Cyclic Loading

Abstract

本研究は, 砂質土の繰り返し載荷時に発生する残留過剰間隙水圧を数値的に予測する手法に関するものである。リングせん断試験機による砂の非排水繰り返し載荷試験と排水・低速度せん断試験結果を検討したところ, 非排水せん断時の残留過剰間隙水圧は排水・低速度せん断時の供試体高さの変化に関係することがわかった。したがって，せん断とともに発生する残留過剰間隙水圧の計算式を提案し, 実験結果と比較して検証した。その結果, 垂直応力とせん断応力ともに繰り返し載荷下条件下の試験では上記計算式は妥当であることが証明された。提案した予測法は基本的な砂の物性値を用いて残留過剰間隙水圧の理論的な数値予測を行うものであり, 動的応答解析における間隙水圧上昇予測も可能となる。

This study is concerned with the formulation of a numerical procedure to evaluate the residual excess pore water pressure generated in sandy soils during cyclic loading.Undrained cyclic loading and drained monotonic ring shear tests on sand were examined and it was revealed that the residual excess pore pressure response during undrained loading conditions could be related to sample height changes in drained monotonic shearing. Consequently, an incremental calculation method for the residual excess pore water pressure changes under undrained conditions is proposed and calibrated against experimental results. Finally, the procedure was validated through comparison with results of an undrained cyclic loading ring shear test performed under both cyclic total normal stress and cyclic shear stress. The proposed method allows for theoretical computation of progressive increase of the residual excess pore water pressure during undrained cyclic loading using basic sand properties, and thus, it also provides the opportunity to couple such pore water pressure increases with the dynamic response analyses.