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为了定量评价主应力轴旋转对地铁荷载作用下隧道下卧软黏土累积变形的影响,通过有限元方法并结合实测数据的验证对地铁荷载下地基土的应力路径进行分析;在此基础上,借助空心圆柱仪对这一复杂应力路径进行室内模拟和对比试验研究。结果表明:主应力轴旋转增大了软黏土的累积变形,且最大有效主应力比(有效最大主应力与有效最小主应力之比)越大、或加载频率越高增大更明显。在实际地铁荷载和通常隧道埋深条件下,考虑主应力轴旋转使软黏土的累积变形增加9%~23%(加载频率越高,增加越大)。可用常规循环三轴的累积变形试验结果乘以土体分别在有、无主应力轴旋转下变形的比值,来预估实际地铁荷载下软黏土的累积变形,初步研究得到该比值与土体的最大有效主应力比之间存在幂函数关系。
In order to quantitatively evaluate the influence of main stress axis rotation on the cumulative deformation of soft clay under the subway load, the stress path of subsoil under subway load is verified by the finite element method combined with the measured data. On this basis, Hollow cylindrical instrument for this complex stress path for indoor simulation and comparative experimental study. The results show that the rotation of the principal stress axis increases the cumulative deformation of soft clay, and the greater the ratio of the maximum effective principal stress (ratio of effective maximum principal stress to effective minimum principal stress), or the higher the loading frequency, the more obvious the increase. Under the conditions of actual subway load and usual tunnel depth, the cumulative deformation of soft clay is increased by 9% ~ 23% considering the rotation of the principal stress axis (the higher the loading frequency, the larger the increase). Cumulative deformation test results of conventional cyclic triaxial can be multiplied by the ratio of soil deformation under rotation with and without primary stress axis to predict the cumulative deformation of soft clay under actual subway load. There exists a power function relationship between the maximum effective principal stress ratio.