Stability Analysis Of Mined-out Area In Hongling Lead-zinc Mine

Mining is bound to form a large number of gobs which are one of the major mining disasters in China. The instability of rock will lead to the collapse and caving of the roof, deformation and destruction of the roadway, with impactive waves which may cause damage to both personnel and equipment. And it can even cause the collapse and crack of the surface. This paper takes Hongling lead-zinc mine as the object of study. After the on-site geological investigations and laboratory testing of rock mechanics, this paper analyzes and evaluates the stability of gobs through numerical simulation, Mathews stability graph and other valuation methodologies. The main work includes the following aspects.(1) Three-dimensional geological models of the mine are created based on the geological data, including the ground surface, surface constructions, orebody, tunnels and shafts, gobs, mining process models and so on. And true three-dimensional mining technology animations are produced including stope preparation, cutting, mining, loading and transporting.(2) Based on the existing rock hardness test experiments, we went to the mine and took the ore, slate, skarn rock and the white marble specimens, with which we conducted the rock mechanics test to obtain the basic mechanical parameters of the rock. The underground wall rock’s structural surface information was acquired by the 3GSM surface measurement system.(3) According to the rock mass quality indicators BQ and RMR, the quality of the wall rock is graded and evaluated. To get the realistic rock mechanics parameters which can provide a theoretical basis for the stability calculating of mined-out area group, the rock mass strength parameters should be reduced based on the generalized modified Hoek-Brown strength criterion.(4) Through the proper simplification of the established geologic models, the simulated grid models are set up with CAD and ANSYS software. Simulating the process of room excavation with FLAC3D and analyzing the rule of pressure changes in the process of mining, the paper analyzes and evaluates the stability of wall rock in mined-out area.(5) After the rock mechanics tests, structural surface surveys and the simulated stress field results, this article analyzes the wall rock stability of the third-stage and the fourth-stage mined-out area by the Mathews stability graph method, and proposes the maximum critical failure hydraulic radius.(6) The preliminary schemes of processing methods of the mined-out area and the recycle of ore pillar are proposed on the basis of the analysis results and field tests.