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.