考虑软基不排水强度循环弱化的格型钢板桩防波堤动力有限元分析
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摘要
波浪循环荷载通过堤身和砂质土置换层传递给软土地基,在软土地基中产生循环动应力,使软黏土发生不排水强度弱化现象,严重影响格型钢板桩防波堤承载性能。结合工程算例,基于动力有限元法建立考虑软土循环弱化效应的格型钢板桩防波堤三维弹塑性动力分析模型,对软土地基在循环荷载作用下最大孔压增长规律以及不排水强度弱化特性进行研究。建立格型钢板桩-软土地基系统动力稳定性分析方法,对格型钢板桩-软土地基系统的破坏模式、稳定性以及沉降变形特性进行分析。结果表明:最大孔隙水压力主要分布在格体周围软土层,主、副格仓底部及部分桩-土接触部位的不排水强度发生明显弱化。考虑软土地基循环弱化效应时,格型钢板桩-软土地基系统的稳定性安全系数显著降低。建议在实际工程中应考虑软土地基循环弱化效应对格型钢板桩防波堤稳定性的影响。
Cyclic stress generated in soft foundation after cyclic wave loading is transferred to the intercalated soft layer through embankment and the backfilled sand layer. The strength of saturated soft clay degrades and soil loses bearing capacity. A 3D elasto-plastic dynamic model of steel sheet pile considering post-cyclic undrained strength degradation is developed using the dynamic finite element method. The maximum excess pore pressure and post-cyclic strength degradation of the intercalated soft layer are investigated. A method for dynamic stability analysis of steel sheet pile-soft foundation system is proposed to investigate the failure mode, stability and settlement of steel sheet pile-soft foundation system. The results show that the maximum excess pore pressure is generated in soft clay around the cell. Post-cyclic strength degradation occurs at the bottom of the main cell, arc cell and some soil-pile interaction areas. Safety factors of stability of steel sheet pile-soft foundation system decrease significantly with considering post-cyclic strength degradation of soft foundation. It is suggested that the post-cyclic strength degradation should be considered in practical design.
Cyclic stress generated in soft foundation after cyclic wave loading is transferred to the intercalated soft layer through embankment and the backfilled sand layer. The strength of saturated soft clay degrades and soil loses bearing capacity. A 3D elasto-plastic dynamic model of steel sheet pile considering post-cyclic undrained strength degradation is developed using the dynamic finite element method. The maximum excess pore pressure and post-cyclic strength degradation of the intercalated soft layer are investigated. A method for dynamic stability analysis of steel sheet pile-soft foundation system is proposed to investigate the failure mode, stability and settlement of steel sheet pile-soft foundation system. The results show that the maximum excess pore pressure is generated in soft clay around the cell. Post-cyclic strength degradation occurs at the bottom of the main cell, arc cell and some soil-pile interaction areas. Safety factors of stability of steel sheet pile-soft foundation system decrease significantly with considering post-cyclic strength degradation of soft foundation. It is suggested that the post-cyclic strength degradation should be considered in practical design.
引文
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[15]焉振,王元战.循环荷载下软黏土不排水强度弱化分析的动力有限元ABAQUS实现》的方法[J].岩土力学,2016,37(增刊2):735-744.YAN Zhen,WANG Yuan-zhan.Dynamic finite element analyses for post-cyclic undrained strength degradation of soft clay in ABAQUS under cyclic loading[J].Rock and Soil Mechanics,2016,37(Supp.2):735-744.
[16]WANG Yuan-zhan,YAN Zhen,WANG Yu-chi.Numerical analysis of caisson breakwaters on soft foundations under wave cyclic loading[J].China Ocean Engineering,2016,30(1):1-18.
[17]邱驹.港工建筑物[M].天津:天津大学出版社,2002:274-279.QIU Ju.Port engineering structure[M].Tianjin:Tianjin University Press,2002:274-279.
[2]李德镍.格型钢板桩结构在港口工程中的应用[J].港工技术,1997,34(1):28-34.LI De-nie.Application of cellular sheet-pile structure in port engineering[J].Port Engineering Technology,1997,34(1):28-34.
[3]王元战,焉振,王禹迟.格型钢板桩结构有限元数值分析[J].岩土力学,2013,34(4):1163-1170.WANG Yuan-zhan,YAN Zhen,WANG Yu-chi.Finite element numerical analysis of cellular steel sheet pile structure[J].Rock and Soil Mechanics,2013,34(4):1163-1170.
[4]王元战,焉振.格型钢板桩结构数值建模方法研究[J].海洋工程,2014,32(5):1-8.WANG Yuan-zhan,YAN Zhen.Studies on numerical model building methods for cellular sheet pile structure[J].The Ocean Engineering,2014,32(5):1-8.
[5]肖忠.软土地基上新型防波堤结构的稳定性分析[D].天津:天津大学,2009.XIAO Zhong.Stability analysis of new breakwater on soft soil foundation[D].Tianjin:Tianjin University,2009.
[6]YAN Shu-wang.Stability of the guiding dike in Yangtze Estuary under the wave load[J].China Ocean Engineering,2005,19(4):659-670.
[7]MATSUI T,BAHR MA,ABE N.Estimation of shear characteristics degradation and stress-strain relationship of saturated days after cyclic loading[J].Soils and Foundations,1992,32(1):161-172.
[8]YASUHARA K.Postcyclic underained strength for cohesive soils[J].Journal of Geotechnical Engineering,1994,120(11):1961-1979.
[9]王元战,焉振.格型钢板桩防波堤动力有限元分析[C]//第十七届中国海洋(岸)工程学术讨论会论文集(上).南宁:海洋出版社,2015:473-478.WANG Yuan-zhan,YAN Zhen.Finite element analysis for dynamic stability of cellular steel sheet pile breakwater[C]//Academic Symposium Proceedings of the17th China Ocean(Offshore)Engineering.Nanning:Ocean Press,2015:473-478.
[10]WANG Yuan-zhan,ZHU Zhen-yu.Dynamic response analysis for embedded large-cylinder breakwaters under wave excitation[J].China Ocean Engineering,2004,18(4):585-594.
[11]SWAGATA BISOI,SUMANTA HALDAR.Dynamic analysis of offshore wind turbine in clay considering soil-monopile-tower interaction[J].Soil Dynamics and Earthquake Engineering,2014,63:19-35.
[12]范庆来,栾茂田,杨庆等.考虑循环软化效应的软基上深埋大圆筒结构承载力分析[J].大连理工大学学报,2006,46(5):702-706.FAN Qing-lai,LUAN Mao-tian,YANG qing,et al.Analyses of bearing capacity for deeply-buried largediameter cylindrical structure on soft clay considering cyclic-softening effect[J].Journal of Dalian University of Technology,2006,46(5):702-706.
[13]闫澍旺,封晓伟.天津港软黏土循环弱化实验研究及应用[J].天津大学学报,2010,43(11):943-948.YAN Shu-wang,FENG Xiao-wei.Test on strength cyclic softening of Tianjin harbor soft clay and its application[J].Journal of Tianjin University,2010,43(11):943-948.
[14]肖忠,王元战,及春宁.波浪作用下加固软基上大圆筒结构稳定性分析[J].岩土力学,2006,46(5):702-706.XIAO Zhong,WANG Yuan-zhan,JI Chun-ning.Stability analysis of large cylindrical structure for strengthening soft foundation under wave load[J].Rock and Soil Mechanics,2006,46(5):702-706.
[15]焉振,王元战.循环荷载下软黏土不排水强度弱化分析的动力有限元ABAQUS实现》的方法[J].岩土力学,2016,37(增刊2):735-744.YAN Zhen,WANG Yuan-zhan.Dynamic finite element analyses for post-cyclic undrained strength degradation of soft clay in ABAQUS under cyclic loading[J].Rock and Soil Mechanics,2016,37(Supp.2):735-744.
[16]WANG Yuan-zhan,YAN Zhen,WANG Yu-chi.Numerical analysis of caisson breakwaters on soft foundations under wave cyclic loading[J].China Ocean Engineering,2016,30(1):1-18.
[17]邱驹.港工建筑物[M].天津:天津大学出版社,2002:274-279.QIU Ju.Port engineering structure[M].Tianjin:Tianjin University Press,2002:274-279.