Experimental and 2D DEM simulation on the triaxial compression characteristics of Xuzhou silt

Abstract

[Objective] Silt from Xuzhou is widely dispersed. In order to comprehend its triaxial compression characteristics and offer a parameter foundation for engineering buildings, [Methods] the silt from Xuzhou Metro Line 1 was subjected to the standard triaxial compression test, in which the axial pressure was applied constantly until the soil was destroyed. The entire test procedure can be thought of as the applied load on the soil's work process. On this premise, the numerical simulation approach is applied to simulate the triaxial test process of Xuzhou silt. [Results] The results show that: With the increase of confining pressure, the peak strength and residual strength of silt increase linearly, and the deformation modulus shows a positive correlation trend; it shows shear failure under different confining pressures, and the rubber membrane distortion is more obvious under low confining pressure. All kinds of cracks gradually increase, the microcracks of the sample begin to increase sharply when the stress reaches the peak value, and the proportion of shear cracks gradually increases; at the initial stage of loading, the load work is almost completely converted into strain energy; during the whole process, the strain energy increases first and then decreases, while the friction energy and damping energy increase until the model is destroyed; the sum of strain energy, friction energy, and damping energy accounts for about 60% of the boundary energy, and the change with the axial strain growth rate is closely related to the stress-strain curve of silt. [Conclusion] The numerical simulation results are in excellent agreement with the laboratory test result. Shear cracks dominate the final failure of silt. According to the energy change, the failure mechanism of the triaxial compression process of silt is separated into three stages: pore compaction, elastic deformation, and plastic deformation before the peak value, and two stages: accelerated failure and strength residual after the peak value. However, with the increase of confining pressure, the post-peak accelerated failure and strength residual stage may disappear.

Keywords

silt / triaxial compression / discrete element approach / microcrack evolution / energy evolution / failure stages / numerical simulation / influencing factors