考虑卸荷扰动的黏土蠕变特性试验研究

盾构施工过程中，由于盾尾建筑空隙的存在，土体会受到较大的卸荷扰动，尤其是对于结构性较强的黏土。通过卸荷拉力来模拟土体受到的卸荷扰动，进行排水剪切蠕变试验。试验结果表明：卸荷拉力越大，土体的扰动程度增大，同级荷载作用下土样的变形越大，且加载压力较小时土样的变形属于稳定型蠕变，蠕变速率随着卸荷拉力的增大而增大，加载压力较大时土样的变形属于衰减型蠕变；与Singh-Mitchell蠕变模型进行比较，发现卸荷拉力较小土样Singh-Mitchell蠕变模型的计算值与试验值相比吻合较好，但当卸荷拉力较大时，模型计算值与实验值相比有较大的误差；修正了Singh-Mitchell蠕变模型的参数，提出考虑卸荷扰动的修正Singh-Mitchell蠕变模型，计算结果与试验数据在加载压力和卸荷拉力较大时吻合较好，对工程实际有一定的指导意义。

A MODIFIED CREEP MODEL FOR CLAY WITH UNLOADING DISTURBANCE

During the shield construction, the surrounding soil would be disturbed for unloading due to shield-end structural spacing. The soil disturbance is especially for clay with strong structure. This paper is to simulate the unloading disturbance of shield soils. The drained shear creep tests are conducted. The results indicate that the deformation under the same load increases with unload increasing. The deformation is steady creep when loading stress is small. Creep rate becomes greater with unloads increasing. The deformation is attenuation creep when loading stress is large. The results are compared with Singh-Mitchell creep model. It is found that the calculated value coincides well with the test data under small loading stress. But, it has large deviation under big loading stress. Therefore we revise the parameters of Singh-Mitchell creep model. A revised Singh-Mitchell creep model considering unloading disturbance is put forward. The calculated value coincides well with the test data under big loading stress and unloading stress.