Fundamental Research On Localization Hazard Monitoring Due To Three-underground Trip Mining

The deformation localization of the coal/rock is both an important characteristics of coal and destabilization precursor, which directly leads to reduce in its overall strength in the loading process and so as to deteriorate bearing-capacity of the project. It is one of a vital technology for safe mining to accurately predict localization destabilization of coal/rock. Essentially, in order to solve the technical difficulty, the localization destruction regularity of both coal pillars and the mining-induced localization destabilization would have been researched inevitably and development process of the excavation disturbance zone(EDZ) using trip mining in three underground. With the use of advanced monitoring methods, the multi-indicator information about localization destabilization had been reasonably determine and ultimately formed a valid method for localization hazard prediction and control in strip mining. This is a fundamental scientific problem in coal safe mining. Applied to theoretical analysis, characteristics upon acoustic emission(AE) testing of the physical and mechanical properties for coal/rock, AE-base physical simulation experiment, numerical simulation and field monitoring, the systematically analysis localization disasters caused due to the change of localization natural and disturbance conditions. Finally, a system of monitoring had been constructed and applied. Those will guide the practical production and ensures the safety in mining.(1) By investigation in field engineering, it indicates that both coal strip mining region and roof structure space variability exists in special coal region coal region. Certain natural or engineering conditions would lead to localization changes in the protective project and strength deterioration in localization areas, thus the evolution of project disaster induced by the project destabilization.(2) Applied acoustic emission experiment on localization damage and fracture in coal/rock, statistical analysis regularity of acoustic emission characteristics were finished at different stages of loading and breakdown in coal samples. At the same time, the loess's physical indicators and collapsibility characteristic parameters experiments as well as the tri-axial test under the condition of consolidated/un-drained have been accomplished and obtained the loess's statistical law of physical indicators, so as to further revealed the possibilities of localization instability and leading to localization disasters of rock mass and soil.(3) According to physical simulation and numerical calculation, the localization deformation process and evolution process induced by localization deformation in coal pillars in-depth were analyzed. Experimental result have shown that the process of the localization disaster caused by the destruction of individual coal pillars with defects mainly include three stages, i.e., the destruction stage of the coal pillar with defects., the stage of development of destruction in coal pillars, the stage of the sudden collapse. With the development of destruction in coal pillars, in case bedrock thickness is insufficient to support loose overburden weight, the roof fall or mine flood disaster may happen under the action of loose overburden. In addition, physical simulation experimental result shown that the strain soften process would reduce localization hazard due to individual disfigurement pillar. The principal assignment of prevention localization hazard is early discrimination to individual disfigurement pillar. Characterization of sandwich rock-mass is foundation to judge the pillar damage and development and caving height. The aquifer and its position in roof overburden is a evidence to estimate water hazard prone or not in the process of pillar damage.The one of the technical foundation is to optimize trip mining design so as to control localization hazard. The thickness of loose overburden rock-mass is crucial factor of sudden localization hazard.(4) Analysis of the content and the possibility of hazard induced by localization in strip mining at various depth, the methods of monitoring and acquisition information about various indicators have systematically formulated and built a local hazard monitoring system in strip mining.(5) Based on the physical simulation and numerical calculation according to three-dimensional finite-difference equation with the use of the law of localization deformation in coal pillars by strip mining, comprehensive contrast and analysis of the deformation laws of surrounding rock, strength deterioration characteristics in overburden and coal pillar, the reasonable program by strip-mining and its related parameters have been determined.(6) The utilization of acoustic detection method on localization loosen deformation and destabilization scope in coal pillars, the scale of stability parameters in coal pillars were defined quantitatively. At the same time, surface deformation monitoring and analysis on-site provided a valid basis for identifying the early warning information in project so as to ensure the safety mining ultimately.The research provides some attestation and reference to other safe mining.