# Calibration of Model Parameters for Soda Saline Soil-Subsoiling Component Interaction Based on DEM
## 1 Introduction  
The Songpan Plain in Northeastern China, is home to one of the world's three major concentrations of soda saline-alkali soil. Recently, soil saline-alkali desertification is on the rise. Subsoiling technology is widely recognized as an effective engineering solution for improving saline lands. To develop an optimal subsoiling component for soda-saline land improvement, we utilized DEM for simulation. Given the inherent contact between subsoiling components and soil particles during the subsoiling process, it is crucial to establish a more accurate model of soda saline-alkali soil particles when using the DEM [1; 2; 3; 4] to analyze these contact effects and optimize the design of related mechanical components [5; 6]. Soil exhibits pronounced anisotropic and nonlinear behavior, characterized by a complex constitutive relationship. Its properties are profoundly influenced by factors such as water and organic matter content, porosity, and texture. A comprehensive review of the literature underscores the abundance of research dedicated to the physicochemical properties of soda saline-alkali soils [7; 8; 9; 10; 11; 12], yet investigations into their physical and mechanical properties are notably scarce. Given the unique physicochemical attributes of soda saline-alkali soil, distinct from those of typical soil, further exploration into how these properties influence physical and mechanical characteristics is imperative. The discrete element method (DEM) is a numerical method for analyzing and solving the dynamic problems of complex discrete systems. It is widely used in the simulation of particle structures [13]. The discrete element method can integrate the contact mechanics model of soil particles to simulate the microscopic and macroscopic deformation of particles and the interaction between soil particles and machinery [14]. Because the micro-contact parameters between soil particles cannot be directly measured by experiments, they need to be obtained through repeated simulation experiments. When utilizing the Discrete Element Method (DEM) to simulate and analyze the movement of soil particle assemblies, it is necessary to calibrate the contact parameters of soil particles such as restitution coefficient, static friction coefficient, and rolling friction coefficient [15]. Many scholars have studied the calibration of soil particle contact parameters using different contact models. The JKR model is suitable for the simulation between wet materials and easily bonded particles, and the cohesion in the model can better characterize the bonding characteristics of soil particles. [PERSON], [PERSON], [PERSON], [PERSON], et al. used a JKR contact model to calibrate the contact parameters between soil particles with the angle of repose as the response value [16; 17; 18; 19]. The Hertz-Mindlin with Bonding (HMB) model binds two particles together by \"bond\", which can characterize the cohesion between soils. [PERSON] et al. used HMB and JKR contact models to conduct comparative tests, combined with soil bin test results, to study the mixing performance of rotary fillers and spiral horizontal blade rotary fillers in silly clay loam [20]. [PERSON] et al. used the HMB contact model to establish a layered soil model to study the soil disturbance during the subsoiling process [21]. Within DEM analyses, soil particles are conventionally defined as spheres due to the computational simplicity of calculating contacts between spherical particles, as it enhances the simulation efficiency [22]. [PERSON], [PERSON], et al. defined soil particles using a single-sphere model and established a soil bin model to analyze soil disturbance during tillage [23]. However, the real-world size and shape of soil particles are inherently more intricate; the relationship between the macroscopic and microscopic characteristics of soil particle groups has yet to be fully understood [24; 25].