Waveform effect on quasi-dynamic loading condition and the mechanical properties of brittle materials

Abstract

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 discussed 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.