Macro-mesoscopic Dynamic Responses of Turfy Soil under Multilevel Cyclic Loading with Different Waveforms Based on the Discrete Element Method

Turfy soil is a special soil with numerous undecomposed plant fibers and humus, which can be considered a soil-fiber mixture. In this paper, the macro-mesoscopic dynamic responses of turfy soil subjected to multilevel cyclic loading with different waveforms (triangular, square, sinusoidal) were investigated employing the discrete element method (DEM). The microscopic parameters of the DEM model were confirmed by laboratory tests and calibration procedures. The hysteresis between the applied and measured stress on the loading plates was dis-cussed to determine the appropriate frequency before simulation. Macroscopically, the discrepancies, including the velocity of the loading plates, the deformation of the specimen, and sample size effect were investigated under these three waveform loadings. Microscopically, the differences in energy, coordination number, average normal contact force between pure and turfy soil, internal force alternation and bending degree of fibers in turfy soil were studied to disclose the discrepancies in macroscopic behaviors with different waveforms. Simulation results illustrate that square waveforms can excite the support of the soil matrix by plant fibers in turfy soil to a greater extent. This study is beneficial for further understanding the mechanical behaviors of soil-fiber mixtures under the action of different forms of cyclic loads in safety engineering.

Automated summary

This study investigates the macro-mesoscopic dynamic responses of turfy soil under different waveform cyclic loading using the discrete element method. The discrepancies in macroscopic behaviors, including the velocity of loading plates, deformation of the specimen, and sample size effect, are analyzed. The differences in energy, coordination number, average normal contact force, internal force alternation, and bending degree of fibers between pure and turfy soil are studied to reveal the discrepancies in macroscopic behaviors with different waveforms.