Experimental Research on Dynamic Parameters of Unit Cell of Deep Mixed Column-Reinforced Soft Clay at Different Stress Levels

Composite soil with deep mixed column is widely used in strengthening soft soil subgrade. This paper carries out the multistage and cyclical loading-unloading dynamic triaxial tests, with the large static and dynamic triaxial equipment (GCTS-STX600), on composite soil with deep mixed column under different confining pressures. The results show that: During the loading stage process of composite soil with deep mixed column, the difference of dynamic elastic modulus under different confining pressures does not change much. The dynamic elastic modulus increases and the damping ratio decreases slightly with increasing the confining pressure. In the process of unloading staged, the difference of dynamic elastic modulus under different confining pressure is more obvious. The dynamic elastic modulus increases and the damping ratio decreases slightly with increasing the confining pressure; the gradual unloading causes the degradation of the dynamic parameters of composite soil with deep mixed column. In the process of grading loading and unloading, the difference of dynamic parameters decreases as the confining pressure increases. Under the same confining pressure, as the dynamic stress ratio CSR increases, the difference of dynamic parameters gradually decreases, and the standard deviation of the corresponding dynamic parameters also decrease. The coefficient of variation of dynamic elastic modulus of Composite soil with deep mixed column is 0.51%~4.89%, the coefficient of variation of damping ratio is 3.55%~13.9%, and the coefficient of variation of damping ratio is larger than that of the corresponding dynamic elastic modulus, that is, damping is more obvious than volatility.

Keywords: Composite soil with deep mixed column, cyclic loading-unloading, large-scale triaxial test, dynamic elastic modulus, damping ratio