Research On Formation Mechanism And Technique Of Prevention And Treatment For The Mined-out Area Of Steep Coal Under Highway

With the increase development of highway system in China, the road networks are improving constantly. Therefore, it is unavoidable to go over the mine-out areas. We have accumulated much valuable experience of mine-out area treatment under highways such as exploration design, stability evaluation and treatment techniques etc. However, the development of technology of highway construction in mine-out areas, generally speaking, is still on the stage of immaturity. Numerous difficulties do exist in new project practices because of the big difference in project conditions in mine-out area under highway. Especially, there are no systematic theories and techniques in stability evaluation methods, evaluation basis, treatment standards and techvaluable experience of mine-out area treatment under highways such as exploration design, stability evaluation and treatment techniques etc. However, the development of technology of highway construction in mine-out areas, generally speaking, is still on the stage of immaturity. Numerous difficulties do exist in new project practices because of the big difference in project conditions in mine-out area under highway. Especially, there are no systematic theories and techniques in stability evaluation methods, evaluation basis, treatment standards and techniques etc. we have no rule to follow and we have to mature design system to learn from. Most importantly, we have no successful case that has dealt with the problems in steep coal mine-out areas.Based on the orbital highway of mine-out area project in Urumchi, Xin Jiang Uygur Autonomous Region, the dissertation aims at disaster-causing mechanism and prevention and treatment issues. The writer applies the methods of fields’ exploration, theoretical analysis and numerical simulation analysis to do researches on the subsidence trend, prevention measures, effect evaluation and treatment proposals etc. in steep-seam mine-out areas after highway has been built.⑴This thesis analyzes that the prime factors to Affect the stability of the steep coal minded-out area are mining and adverse geology. And it includes the circumstance of the bad diseases of roadbed, bridge, tunnel and culvert occurring in the steep coal of minded-out area under highway.⑵This thesis analyzes the impacts the cavity has on the stability of highway roadbed based on the datum of mind-out area of small coal pits in this project and on those of other geological explorations. In this project the influence depth of the base additional stress can reach the range of water flowing fracture. Thus, it is prerequisite to take measure for the cavity in minded-out area to meet the demand of the specification for design of highway subgrades⑶Using FLAC software, the contrast models of the upper covering thickness and security coal pillars top width in mined-out area are established. By comparing and analyzing, the impacts of different upper covering thickness and security coal pillar’s top width on the stability of the ground when build a road above security coal pillar in mined-out area are obtained. The simulation results show that the upper covering has self-stability within a certain thickness, the maximum value of surface subsidence first increases then decreases with the increase of strata thickness. After the excavation of coal seam, security coal pillar plays an important part in remaining the stability of strata, and there also produces the deformation displacement zone and deformation failure zone at the edge of security coal pillar. At the same time, the wider the reserved top width of security coal pillar is, the smaller the surface subsidence value above the security coal pillar after the excavation of coal seam is.⑷Through numerical analysis for this project, we found that when building highway above the mined-out region of Tiechanggou mining area, the highway has great effect on the surface stability of the mined-out area It requires for reinforcement measure first and foremost to meet the demand of the specification for design of highway subgrades.