震动荷载作用下地铁隧道长期沉降机制试验研究

Experimental study on the long-term settlement mechanism of subway tunnel under vibration loads

通过循环三轴试验,对地铁行车振动荷载作用下武汉地区盾构隧道周围软粘土及砂土的变形特性作出分析,并对隧道运营期的沉降进行了预测。试验结果表明:在长期循环荷载作用下,粘土试样累积塑性变形及其孔隙水压的变化均经历了快速增长—匀速增长—衰减稳定3个阶段;砂土在循环荷载下跟粘土类似,同样经历快速增长—匀速增长—衰减稳定3个阶段,只是砂土的应变量较粘土相比要小很多。地铁荷载作用下引起的长期沉降分为不排水循环荷载作用下土体中的累积变形引起的沉降和土体中由于动荷载引起的孔压消散产生的固结沉降两部分;通过室内试验得到的拟合模型和分层总和法计算结果,发现地铁列车运行期间的振动荷载对于运营期内土层的沉降影响主要集中在运营初期3年左右,此后沉降值基本趋于稳定。

Through the cyclic triaxial tests,the deformation characteristics of the soft clay around the shield tunnel in Wuhan under the subway vibration loads are analyzed,and the settlement during the tunnel operation period is predicted. The test results show that,the cumulative plastic deformation of the clay samples and the change of the pore water pressure experience three stages under the long-term cyclic loading,i. e.,the rapid growth-the uniform growth-the attenuation stabilization. The situation of the sand is similar to that of the clay under cyclic loading,which also experiences rapid growth-uniform growth-attenuation stabilization,but the sand strain is much smaller than that of clay. The long-term settlements caused by subway loads are divided into two parts： the settlement caused by soil cumulative deformation under undrained cyclic loads and the consolidation settlement with the pore pressure dissipation caused by dynamic loads. Through the fitting model obtained from the indoor tests and the layered summation method to calculate the results,it is found that settlement influence of the vibration loads during the subway operation is concentrated in the early period of the operation for about three years,and then the settlement value tends to be stable.