Parameters Optimization Of The Boundary Of Open-Underground Combined Mining Mine And Analysis Of Fracture Characteristics Of The Roof Key Strata

China is always a big coal consumer, and this situation will last a long time in the future. With the rapid development of the economic construction, the energy consumption and the requirements for high efficiency and safety in coal production are bound to increase. In the construction of high production and high efficiency coal mine, the model of open-underground combined mining has been adopted more and more, but there is no mature engineering experience in open-underground combined mining of shallow horizontal thick coal at home and abroad. On the basis of intensive study on existing research results, parameters optimization of the boundary of open-underground combined mining mine and fracture characteristics of the roof key strata have been studied by using two methods of similar simulation and numerical simulation in the paper.(1) Bases on the similarity theory and actual engineering, the similar simulation experiment is designed and carried out. The research in this part focuses on deformation characteristics of the steps and overburden rock due to underground mining, and involves the influence the direction of underground mining brings to slope stability. The monitoring and simulation results are in good agreement.(2) In order to obtain reasonable physico-mechanical parameters, a numerical model in FLAC3D is established which uses the geologic section in similar simulation experiment, the mining in the experiment is simulated and the results of numerical simulation are made in agreement with similar simulation. Three numerical models are established according to three mining schemes designed for shallow horizontal thick coal. In the mining simulation, specific criterions are applied to detect failure in the model, and then, boundary parameters of the mine are optimized through contrastive analysis of the simulation results.(3) The key strata theory in ground control is applied in open-underground combined mining slope engineering, the engineering model is generalized as two different mechanical models. And during the process of advance of the face, fracture characteristics of the key strata are studied in terms of deformation and internal force. The rationality of two mechanical models is assessed according to the contrastive analysis of calculation results along with consideration of engineering practice.Through the above research, some deformation-failure rules of open-underground combined mining slope are obtained which can provide useful theory reference for future open-underground combined mining project.