Simulation and analysis of soil homogenization drills based on discrete element method and response surface methodology

Abstract

Currently, rotary drilling is one of the main pieces of equipment used for in-situ remediation of contaminated soil. However, this equipment has problems such as uneven mixing and low utilization efficiency, which affect the efficiency of in-situ soil remediation. To improve the efficiency of in-situ soil remediation, this paper takes contaminated black soil as the research object, and the structural design of the new three-stage soil remediation auger is carried out based on SolidWorks. The mixing process of soil and heavy metal passivator under different motion and structural parameters was investigated by the discrete element method (DEM) and response surface methodology. The experimental design was based on rotational speed, homogenizing mixing time, crushing section pitch, and homogenizing section pitch as factors, and soil fragmentation ratio, the coefficient of dispersion, and torque as optimization indices. The kinematic and structural parameters of the three-stage auger drill bit were then optimized using the one-factor method, the orthogonal test, and the response surface methodology, respectively. The test method uses a one-way test to determine the central level value of the orthogonal test and a comprehensive balance method to determine the best combination of parameters for the orthogonal test, which is then used as the central value of the response surface test for parameter optimization. The optimal combinations of kinematic and structural parameters of the three-stage auger drill bit are determined and validated using response surface methodology. The optimum combination of parameters was found to be a speed of 129 rpm, a homogenizing mixing time of 24 s, a pitch of 165 mm in the crushing section, and a pitch of 132 mm in the homogenizing section. The error between the optimal value of the predicted model using the response surface method and the actual simulated value under the optimal parameters is 4.2%, 4.9%, and 5.3%, respectively. The optimized factor parameters provide a reference for the design of the structural and kinematic parameters of the in-situ homogenization equipment.