不同粒径分布影响下煤粉界面力链构型演化及接触刚度研究OA

In this study,the effects of wet coal seams with different particle size distributions on the contact stiffness of joint surfaces are systematically explored through comprehensive experiments and numerical methods.Firstly,the contact parameters between particles and particles and between particles and contact surfaces are determined by stacking angle and inclined plate slip experiments under controlled humidity.Then,the crushing parameters of a Tavares UFRJ crushing model are calibrated by comparing the simulated and experimental stress-displacement responses through confined compression experiments.Based on these calibration parameters,a three-body contact model is established by the finite element-discrete element coupling method.The upper plate is a rigid body model subject to normal pressure.The wet pulverized coal layer is simulated by the discrete element method and periodic boundary conditions are applied.For the lower plate,the finite element method is applied to establish and fix the bottom boundary.At the same time,a special data mapping algorithm is developed to transfer the particle contact force to the finite element nodes.The simulation results fully reveal the mechanical behavior of the particle system.The analysis of the evolution of fragmentation rate and coordination number shows that under the load of 0.03 Mpa,the fragmentation rate of the wide particle size distribution jumps nonlinearly from 8%to 14%in 3.3-3.6 ms,and the coordination number decreases sharply,indicating the occurrence of chain fragmentation and network collapse.The medium particle size distribution maintains a stable coordination number,which can effectively transfer stress and avoid large-scale crushing.Under the load of 0.05 Mpa,the initial crushing of all distribution models increases rapidly,among which the crushing rate of 20-80 μm model is the highest,while the growth rate of 20-100 μm model is the slowest due to the buffering effect of fine particles.From the evolution process of pulverized coal particle breakage,it can be seen that there is a significant stress concentration effect in the asperity area due to the small contact area,which leads to the preferential breakage of the large particles in the area.The sub-particles produced by crushing gradually penetrate into the concave area on the surface of the guide rail,and fill the gap with small particles to form a covering layer effect,so as to optimize the force chain network structure of the pulverized coal layer,enhance its continuity and directivity,and improve the compactness and local stress dispersion ability of the contact interface.Then,the rose diagram and force chain visualization of the pulverized coal layer particles further show that the fine particle system forms a dense and isotropic force chain network,which promotes the uniform distribution of stress on the contact surface.The wide particle size distribution is significantly broken under the condition of high pre-tightening force dominated by large particles,which is reorganized into a dual-mode force chain structure,resulting in multiple high stress areas on the contact surface.Finally,the normal stiffness change of the pulverized coal layer and the stress distribution mode of the contact surface are systematically evaluated,and then the overall three-body contact stiffness is calculated.The quantitative results show that the contact stiffness of 20-40 μm and 20-100 μm models reaches 3.536×108 Pa/m and 3.956×108 Pa/m,respectively,under the compressive load of 0.05 Mpa.Finally,the numerical prediction results are verified by the hammer excitation and the pulse excitation test carried out by the acceleration sensor,which shows that the experimental and simulated three-body contact stiffness values are highly consistent.This study provides new insights into the micromechanical behavior of granular media in humid environments and establishes a reliable modeling framework for analyzing contact characteristics in engineering applications involving particle-filled interfaces.