地铁振动荷载作用下隧道周围加固软黏土动弹性模量试验

对地铁隧道周围软黏土进行加固，已应用于地铁隧道沉降的治理，但是对软黏土加固后的动力特性研究还不够深入。通过对上海地铁隧道周围加固软黏土进行GDS试验，系统探讨循环荷载振动频率、循环动应力幅值、初始偏应力及围压对动弹性模量的影响。试验结果表明:随着循环振动次数的增加，动弹性模量的衰减过程可分为急剧衰减阶段和缓慢衰减阶段，且缓慢衰减阶段的时间要明显长于急剧衰减阶段；循环荷载振动频率对动弹性模量有显著影响；随着循环应力幅值、初始偏应力、围压的增大，动弹性模量都有了很大的提高，但其变化对动弹性模量的衰减速率并无显著影响。采用对数函数对试验数据进行回归分析，建立了加固软黏土在循环荷载作用下动弹性模量衰减模型，较好的反映了动弹性模量的衰减规律。

EXPERIMENTAL STUDY ON DYNAMIC ELASTIC MODULUS OF REINFORCED SOFT CLAY AROUND SUBWAY TUNNEL UNDER VIBRATION LOADING

Although reinforcing soft clay around subway,as a technique,has been used in settlement treatment,some issues on dynamic characteristics of reinforced soft clay remain unaddressed.Based on a series of dynamic triaxial tests of reinforced soft clay around Helen Subway station of Shanghai metro line No.4 with laboratory GDS test apparatus,the effects of cyclic loading frequency,stress amplitude,initial deviator stress and confining pressure on dynamic elastic modulus were studied.The results show that(i) the degradation process of dynamic elastic modulus can be divided into rapid stage and slow stage with the increase of cycle vibration number,and the period of the slow stage is longer than that of the rapid stage(ii) cyclic loading frequency has a significant effect on dynamic elastic modulus;(iii) with the increase of cyclic stress amplitude,initial deviator stress and confining pressure,the dynamic elastic modulus increases greatly,however,its velocity is not notably influenced by the change of the three factors.Finally,a degradation model of dynamic-elastic modulus was built with the logarithmic function and the model parameters being determined by regression analysis method.