Strength weakening of soft clay under cyclic loading and its dynamic calculation
WANG Yuan-zhan1, YANG Pan-bo1, 2, SUN Xi-pin3, LIU Han-qi1, HU Shen-rong1
1. National Key Laboratory of Water Conservancy Engineering Simulation and Security, Coll Aborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Tianjin University, Tianjin 300072, China; 2. CCCC First Harbor Engineering Design Institute Co., Ltd., Tianjin 300222, China; 3. Tianjin Research Institute for Transport Engineering, Tianjin 300456, China
Abstract：Strength reduction may take place for the littoral soft clay under the action of wave loading. As a result, the bearing capability of soft clay foundation will become significantly lower, and the stabilization of the structures will be affected. By performing cyclic triaxial tests on muddy-silty clay taken from Yantai littoral zone, variation of pore water pressure and weakening of undrained shear strength of clay subjected to different confining pressures, deviator stresses, dynamic stresses and cycle numbers are studied. According to the laws of the development of pore pressure, a model for calculating pore pressure is proposed. In addition, by using the theory of quasi-overconsolidation and combining the pore pressure model and the laws of undrained shear strength, a formula for strength weakening which contains confining pressures, deviator stresses, dynamic stresses and cycle numbers is put forward. The relevant experiment is done to verify the formula. Then it is applied to the dynamic numerical model of a breakwater in Yantai Port. From the experiment to the numerical model, a dynamic calculation method considering the effect of strength weakening which is convenient to be used in engineering is proposed completely.
王元战, 杨攀博, 孙熙平, 刘翰琪, 胡珅榕. 循环荷载下软黏土强度弱化研究及其动力计算应用[J]. 岩土工程学报, 2015, 37(5): 821-828.
WANG Yuan-zhan, YANG Pan-bo, SUN Xi-pin, LIU Han-qi, HU Shen-rong. Strength weakening of soft clay under cyclic loading and its dynamic calculation. Chinese J. Geot. Eng., 2015, 37(5): 821-828.
[1] 闫玥. 长江口导堤软黏土地基在波浪荷载作用下强度软化的特性研究[D]. 天津: 天津大学, 2007. (YAN Yue. Research on strength weakening character of soft clay foundation in Yangtze Estuary leading jetty under cyclic loading[D]. Tianjin: Tianjin University, 2007. (in Chinese)) [2] HYDE A F L, WARD S J. A pore pressure and stability model for a silty clay under repeated loading[J]. Géotechnique, 1985, 35(2): 113-125. [3] KOUTSOFTAS D C. Effects of cyclic loads on undrained strength of two marine clays[J]. Journal of the Geotechnical Engineering Division, ASCE, 1978, 104(5): 609-620. [4] MATASOVIC N, VUCETIC M. Generalized cyclic degradation-pore pressure model for clays[J]. Journal of the Geotechnical Engineering Division, ASCE, 1995, 121(1): 33-41. [5] 吴明战, 周洪, 陈竹昌. 循环加载后饱和软黏土退化性状的试验研究[J]. 同济大学学报, 1998, 26(3): 274-278. (WU Ming-zhan, ZHOU Hong, CHEN Zhu-chang. Experimental research on softening character of saturated soft clay under cyclic loading [J]. Journal of Tongji University, 1998, 26(3): 274-278. (in Chinese)) [6] 周建. 循环荷载作用下饱和软黏土特性研究[D]. 杭州:浙江大学, 1998. (ZHOU Jian. Research on character of saturated soft clay under cyclic loading[D]. Hangzhou: Zhejiang University, 1998. (in Chinese)) [7] 章克凌, 陶振宇. 饱和黏土在循环荷载作用下的孔压预测 [J]. 岩土力学, 1994, 15(3): 9-17. (ZHANG Ke-ling, TAO Zhen-yu. Pore pressure prediction of saturated soft clay under cyclic loading[J]. Rock and Soil Mechanics, 1994, 15(3): 9-17. (in Chinese)) [8] ANDERSEN K H, ROSENBRAND W F, BEOWN S F, et al. Cyclic and static laboratory tests on Drammen clay[J]. Journal of the Geotechnical Engineering Division, ASCE, 1980, 106(5): 499-529. [9] YASUHARA K, HIRAO K, HYDE A F L. Effects of cyclic loading on undrained strength and compressibility of clay[J]. Soils and Foundations, 1992, 32(1): 100-116. [10] 王淑云, 楼志刚. 原状和重塑海洋黏土经历动载后的静强度衰减[J]. 岩土力学, 2000, 21(1): 20-24. (WANG Shu-yun, LOU Zhi-gang. The degradation of undrained shear strength of undisturbed and remolded marine clay after cyclic loading[J]. Rock and Soil Mechanics, 2000, 21(1): 20-24. (in Chinese)) [11] 高广运, 顾中华, 杨宏明. 循环荷载下饱和黏土不排水强度计算方法[J]. 岩土力学, 2004, 25(增刊): 379-382. (GAO Guang-yun, GU Zhong-hua, YANG Hong-ming. A calculation method for undrained strength of saturated clay under cyclic loads[J]. Rock and Soil Mechanics, 2004, 25(S0): 379-382. (in Chinese)) [12] 胡伟, 黄义, 刘增荣. 循环荷载下饱和黄土不排水强度退化规律试验与理论研究[J]. 岩土力学, 2009, 30(10): 2996-3000. (HU Wei, HUANG Yi, LIU Zeng-rong. Testing and theoretical study of undrained shearing strength of saturated loess under cyclic loading[J]. Rock and Soil Mechanics, 2009, 30(10): 2996-3000. (in Chinese)) [13] 霍海峰. 循环荷载作用下饱和黏土的力学性质研究[D]. 天津: 天津大学, 2012. (HUO Hai-feng. Research on mechanical character of saturated soft clay[D]. Tianjin: Tianjin University, 2012. (in Chinese))
