Gently Inclined Hard Rock Deposits Goaf Roof Falling Regulation

The collapse of roof in the gob area makes big difference on the underground mining and pressure management. To ensure safety and orderly recovery, meanwhile to explore the new ways of the predicted forms collapse of roof in the gob area and the taking down process, this paper centers around the collapse of roof, takes the Longqiao gob area as the research object, combines with its mine geology mining conditions, field investigation and status of mined areas, uses the computer numerical simulation, calculates and analyzes the gob roof law of mass destruction and falling, and the inclined hard rock caving form and process of the deposits of the gob roof, and makes further research combining with the live drilling monitoring. The main contents and conclusions are as follows:(1) Based on previous research results, the paper proposes the criterions of the hard rock roof falling out area. Drawing on the basis of previous studies, the use of arch theory Protodyakonov come falling gob caving the roof arched form, on the basis of the roof falling gob criteria proposed in the weight under the falling roof rock mass conditions for free surface conditions, failure conditions, equilibrium conditions, three conditions are indispensable.(2) Advanced development of simulation programs, the research achieves an empty area of the hard rock deposits in the law of simulated roof fall. Finite difference method based on the principle of numerical simulation software FLAC3D mined area on the three-dimensional simulation program by FLAC3D secondary development, has formed a certain function of roof fall gob simulation program, the realization of gob Roof collapse patterns and processes visual images, analyzes the sequence of the different mining gob roof under the stress, strain and displacement distribution. The results show that: the role of roof rock and the tensile stress free surface conditions, and as gob area exposed to gradually increasing tensile stress in the roof is also increasing, and approaching the rock tensile strength, and ultimately lead to roof damage, and then falling.(3) With the multi-program comparison, mining sequence optimization scheme is proposed. In the detailed analysis of the Longqiao iron mining sequence used in the present numerical simulation results based on the exploitation by the other two different ways of simulation analysis, the different mining methods on the roof rock displacement, tensile stress and falling rocks volume significantly affected the conclusions. Sublevel caving method requires a certain amount of buffer in the cushion, we adopted the program two of the mining sequence is superior to the other two programs, namely mining methods from the middle to both sides of the mining method is more ideal.(4) Combining with the drilling monitoring, the research verifies the reliability of simulation. Borehole camera observations obtained by means of the use of the mine roof rock caving height data, the data show that the process of experienced a falling rock "falling - and stability - and then falling - and then stabilize". Above conclusions are in good agreement with the numerical results, to verify the simulation method is feasible, but also explored for predicting the roof falling off the form and provide a new way to process.This research not only explored the forms of the collapse of roof in the gob area and its predicted taking down process, but also combined with the practical engineering, so it is doomed to have some certain practical value.