Microscopic deformation and fragmentation energy consumption characteristics of soils with various moisture contents using discrete element method

Abstract

Increased soil moisture content commonly leads to higher resistance and energy consumption during agricultural operations. However, the impact of moisture content on soil microscopic deformation and fragmentation energy consumption characteristics remains unclear. In this study, discrete element models of sandy clay loam with different gravimetric water contents (15.0%, 18.8%, 21.6%, 24.1%, and 27.3%) were constructed for simulation experiments using coupled contact method (Hertz-Mindlin with bonding and Hertz-Mindlin with JKR). The degree of soil fragmentation and the rate of crack propagation were investigated. The results indicated that at fixed gravimetric water content, fissure rate exhibited a pattern of slow increase, rapid increase, and eventual stabilization with increasing compression displacement, while the fissure transfer coefficient showed a pattern of first increase and then decrease. At a fixed compression displacement, the increase in moisture content led to a decrease in both fissure rate and fissure transfer coefficient. The analysis of soil stress-strain characteristics and energy dissipation patterns found that soil with a gravimetric water content of 27.3% (close to soil liquid limit) exhibited no compression yield point; at a soil gravimetric water content of 15.0%, the minimum crushing energy (Udmin) was achieved (1.32 J), with a maximum elastic strain energy (Uemax) of 1.83 J. Similarly, at a soil gravimetric water content of 24.1%, the minimum crushing energy (Udmin) was reached (2.17 J), with a maximum elastic strain energy (Uemax) of 2.25 J. The comparison between actual and simulated results revealed low relative errors (<6%) in Udmin for all the above soil gravimetric water contents, suggesting the feasibility of our coupled discrete element model for assessing soil crushing energy consumption. This study revealed microscopic deformation and instability fragmentation mechanisms of soils with various moisture contents under vertical axial loads. Our findings provide novel method and strategy for developing the high-efficiency low-consumption soil fragmentation model.