Research Of Deformation Feature On Soil Considering Shield Tunnel Construction Disturbance

Soil around lining would be disturbed during shield tunneling construction,especially for soft clay, whose structure would be destroyed badly, and soft clay isdisturbed seriously, the soil after disturbed would cause large deformation,particularly for the long-term deformation and deformation under cyclic load after themetro is in motion. So it’s necessary to do research on secondary consolidationcharacteristic, creep and cyclic creep characteristics of disturbed soil.The problems mentioned above are researched by indoor tests, at the base ofunderstanding the disturbance mechanism of soil around lining because of shieldtunneling construction, the change of stress states are simulated by different methods,and secondary consolidation, triaxial shear creep and cyclic creep tests are conducted.The compression index keeps steady when preload is less than structure yieldstress with squeezing disturbance increased,, the compression index decreases rapidlywhen the preload is greater than structure yield stress, and tends to a steady value. Therelationship between secondary consolidation coefficient and load is createdsectionally, and the squeezing disturbance degree is created according to the change ofstructure yield stress.The structure of soil is damaged for shearing disturbance, compression indexincreases with the structure of soil, during the creation of secondary consolidationcoefficient model, the disturbance degree is created at the base of compression index.The deformation under each load increases with unload increased, at the base oftesting data, an amendatory Singh-Mitchell creep model considering unloadingdisturbance is proposed.Considering the effect of shield tunneling construction disturbance on the longcyclic deformation, Unloading stress has large effect on the first cyclic deformation,and the deformation increases with unloading stress, then unloading stress has littleeffect on the second cyclic deformation; and the undrained shear strength after cyclicload decreases when disturbance degree increases because of unloading stressincreased.