Research On Force Change Law Of Bottom Structure Based On PFC2D Natural Caving Method

The bottom structure of the natural caving method is the "heart" of mining.The destruction of the bottom structure will have an immeasurable impact on the operation of the mine as well as the safety of human beings.This thesis is based on "The Study on the Stability of Bottom Structure of Pulang Copper Mine of Yunnan Diqing Nonferrous Metal Co.,Ltd".With the geological data offered by Pulang Copper Mine of Yunnan Diqing Nonferrous Metal Co.,Ltd,adopt Rockmass Mechanics Theory and Silo Theory to analyze the stress variation law during the process of mining in the first mining area.In the meantime,PFC2D,the numerical simulation software,is used to stimulate and analyze the stress variation law in front of the advance line during the process of undercutting and caving of the ore body,as well as the variation law of secondary pillar and funnel part during the process of caving of the ore body.What’s more,the practicable order of ore drawing is proposed.The main search did for this thesis is as follows:1.Based on Rock Mechanics and Materials Mechanics Theory,analyze the stress of rocks around the stope when undercut zone is formed,and when the stress of rocks around the stope is in the state of elasticity or plasticity,the stress variation law in front of the advance line.2.According to the ore body caving process in the natural caving method,summarize the evolution law in the course of pressure arch’s caving and the stope advancing for the analysis of the pressure arch theory.Analyze the force characteristic of the bottom structure respectively in the way of retreating undercut,pre undercut and advancing undercut.PFC2D software is used to stimulate the process of undercutting and caving so that the stress variation laws in front of the advance line and the stress concentration zone can be analyzed and summarized.3.The theoretical calculation of the overburden pressure is carried out by using the JANSSEN Formula and the Silo Theory Formula,and compared with the simulated data.Establish five types of overburden thickness ore drawing models,analyze the stress of bottom structure in multi or single funnel condition,and the practicable order of ore drawing is proposed.Analyze high-dynamic stress in the ore drawing funnel during the ore drawing process,and analyze where the maximum effect occur by high-dynamic stress.The data used in this thesis are from the actual condition,and closely connected with the operation.The results of the study provide theoretical basis for mine production and the construction,particularly for mine support.