Experimental Study on the Effect of the Displacement Rate on the Shear Strength of Coastal Soft Soil

Dynamic consolidation is widely applied in the consolidation of soft soil foundation, though there is no in-depth subdivision research on the mechanism of dynamic consolidation of coastal soft soil foundation, and there is no independent, complete, theoretical system to support engineering practice. The effects of dynamic consolidation replacement rates on the shear strength of coastal soft soil were studied by the dynamic consolidation replacement undrained shear (CU) tests. CU tests were conducted for each set of samples under four confining pressures of 50 kPa, 100 kPa, 200 kPa, and 300 kPa, stress–strain curves and effective stress paths were obtained, and then shear strength parameters at different displacement rates were determined: effective cohesion and effective internal friction angle. The effective cohesion decreases, while the effective internal friction angle increases, with the increment of displacement rate. The shear strength of coastal composite soil is improved with the rising displacement rate, and the effects of multi-pile displacement on the shear strength of coastal soft soil are more significant at the same displacement rate. There is a quantitative power function relationship between the pile–soil interaction coefficient and displacement rate of coastal composite soil. Based on the test results, a modified formula for the shear strength parameters of dynamic tamper-replaced coastal soft soil is proposed.