地铁列车荷载下冻融土刚度软化试验研究  

Experimental study on stiffness softening of frozen-thawed soil under subway loading

作　　者：丁智[1] 魏新江[1] 庄家煌 蔡知进 DING Zhi;WEI Xinjiang;ZHUANG Jiahuang;CAI Zhijin(Department of Civil Engineering, Zhejiang University City College, Hangzhou, Zhejiang 310015, China)

机构地区：[1]浙江大学城市学院土木工程系,浙江杭州310015

出　　处：《岩石力学与工程学报》2018年第4期987-995,共9页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(51508506);浙江省自然基金项目(LQ16E080008);杭州市科技计划项目(20172016A06)~~

摘　　要：冻结法在地铁联络通道和进出洞施工中被广泛应用,但冻融作用会对土体刚度产生影响,列车运营期循环荷载作用下,会对地铁运营安全造成隐患。基于动三轴试验,模拟地铁循环荷载作用下冻融土的动应力,得到地铁列车荷载作用下土体刚度软化曲线,并建立刚度软化数学模型。研究结果表明:冻融土体在循环荷载作用下的刚度软化可以用分段函数描述,在循环加载初期,刚度G与循环次数N之间存在半对数关系,当lnN达到8.25~9.5时软化曲线出现拐点,此后继续加载循环应力土体刚度不再有明显的下降;随着冻结温度的降低,循环加载前的初始刚度G_1以及循环后的残余刚度G_w均有所减小,刚度损失比w逐渐增加;同时,冻融还对刚度软化具有明显的加速作用;土体固结对整体刚度有加强效应,提高冻融土体固结度能够使土体刚度显著增大,刚度损失比w有所减小,并降低了土体软化速度。研究结果可为控制地铁冻结法施工区域的工后沉降、保证地铁安全运行提供有益指导。Freezing technology is frequently used in the construction of connection tunnel between metro tunnels and in the operation of shield break-in and break-out. The freezing-thawing action has the negative effect on the stiffness of soil. When the subway comes into service,its safety could be undermined under metro loading. In this paper,the undrained dynamic triaxial test was conducted in laboratory to simulate the dynamic stress state of frozen-thawed soil under metro loading. The variation of soil stiffness was obtained and a stiffness softening model was established. A piecewise function was found to describe the stiffness softening of frozen-thawed soil under cyclic loading. When the metro loading is firstly loaded on the sample,there is a semi logarithmic correlation between the stiffness G and the loading times N. When the value of ln N reaches to 8.25 to 9.5,a turning point of the softening curve appears,and the stiffness declines little after this turning point. The freezing-thawing operation also accelerates the stiffness softening process under the metro loading. The stiffness can be increased by raising the consolidation degree. The higher the consolidation degree of the frozen-thawed soil is,the lower the stiffness loss ratio and softening speed are.

关 键 词：土力学 冻融土 循环荷载 刚度 固结度 冻结温度 

分 类 号：TU43[建筑科学—岩土工程]