海洋软黏土不排水循环强度的触变性试验研究  

Experimental study on undrained thixotropic cyclic resistance characteristics of marine soft clay

作　　者：吴琪[1] 吉东伟 肖兴 朱升冬 陈国兴[1] WU Qi;JI Dongwei;XIAO Xing;ZHU Shengdong;CHEN Guoxing(Institute of Geotechnical Engineering,Nanjing Tech University,Nanjing 210009,China;Fujian Yongfu Power Engineering Co.,Ltd.,Fuzhou 350108,China)

机构地区：[1]南京工业大学岩土工程研究所,江苏南京210009 [2]福建永福电力设计股份有限公司,福建福州350108

出　　处：《岩土工程学报》2024年第12期2513-2520,共8页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(52378346,51978334)。

摘　　要：以长江入海口海域软黏土为研究对象,开展了系列不固结不排水循环三轴试验,研究了静置时间T、含水率w及塑性指数IP对重塑海洋软黏土不排水触变循环强度的影响。试验结果表明:以双幅轴向应变εad=5%为重塑海洋软黏土试样的失效判据,破坏振次为15的循环强度CRR15随T的增加而增大,T=14 d,CRR15的增长速度最快,T>28 d时CRR15增加略有上升或趋于稳定。前期扰动或循环荷载的施加会导致软黏土触变性减弱,软黏土的触变循环强度比Ad明显小于静剪强度比As。Ad随IP的增加先增大后降低,随w的增加而增大,随归一化含水率w/wL的增加先增大后减小,当w/wL=0.76时,Ad达到最大值。开展平行工况的无侧限抗压强度试验,提出以循环轴应力幅值σd与2倍无侧限抗压强度qu之比σd/2qu表征循环应力水平,发现σd/2qu与不同w及T的试样达到εad=5%所需的破坏振次N_f存在唯一性关系,且σd/2qu随N_f的增大呈幂函数减小。A series of unconsolidated undrained cyclic triaxial tests are carried out on the marine soft clay in the estuary of Yangtze River.The effects of age T,water content w and plasticity index IP on the thixotropic cyclic resistance of the remolded marine soft clay are investigated.The test results show that the cyclic resistance CRR15 for 15 cycles of the remodeled marine soft clay increases with T when the failure criterion is defined as the double-amplitude axial strainεad=5%,and the fastest growth rate of CRR15 is observed when T=14 d,and the CRR15 increases slightly ortends to be stable when T>28 d.The thixotropy of soft clay is weakened by early disturbance or cyclic loading,and the thixotropy cyclic resistance ratio Ad is obviously smaller than the static shear strength ratio As.Ad first increases and then decreases with the increasing IP,but increases with the increase of w.Ad first increases and then decreases with the increase of the normalized water content w/wL,an increase in the normalized water content w/wL causes Ad to first increase and then decrease,and it reaches the maximum value when w/wL=0.76.The unconfined compressive strength tests under parallel test conditions are carried out,and the cyclic stress level is characterized by the ratio of the cyclic axial stress amplitudeσd to 2 times the unconfined compressive strength qu,σd/2qu,and it is found thatσd/2qu is uniquely related to the failure cycle Nf required for the specimen to reachεad=5%,andσd/2qu decreases as a power function with the increase of Nf.

关 键 词：重塑海洋软黏土 循环强度 含水率 塑性指数 触变循环强度比 

分 类 号：TU447[建筑科学—岩土工程]