Mechanism And Engineering Practice On Mutual Response Between Underground Mining Of Shallow Coal Seam And Protection Of Fragile Ecological Environment

Based on the typical conditions of western coalfield characterized by the shallow coal seam, the developed gully and the extremely fragile ecological environment, the mechanisms of the mutual response between protective underground mining and sur-face environment protection were present to reconcile the contradictions between the large-scale underground mining and the fragile environment protection. Physical simulation, numerical simulation, theoretical analysis and field observation were conducted to analyze the laws of overburden movement and fracture development, the mechanisms and the technologies of aquifer-protection mining, the applicability of surface ecological environment to underground mining and the construction of ecolo-gic functional circles. And the engineering practice was proved to be successful. The major research achievements are as follows.(1) The mechanisms of the mutual response between underground mining and fragile environment protection was proposed and successfully put into the engineering practice.The concept of city ecologic functional circle was introduced into the protection of desert coalfield. Based on the surface environment applicability to underground mining and the mechanism of aquifer-protection mining, a technology system for achieving the mutual response between underground mining and surface protection, including the construction of a peripheral guard circle which majors in the botanic measures, the safeguard of a perimeter evergreen circle by the means of pre-mining functional circle construction, in-mining aquifer protection and post-mining ecologi-cal restoration, and the afforestation of the centre beautification circle, was con-structed through the basic technologies of artificial regulation and oriented succession, the optimization of forest structure, etc.(2) A system for predicting the overburden movement pattern in response to un-derground mining of shallow coal seams in western coalfield was devised.Based on the characteristics that the overlying strata subsides synchronously with the key strata and the fracture development is controlled by the subsidence of the key strata, the structural mechanical models for the first breakage and the periodical breakage of key strata were constructed to analyze the stability of key strata. Derived from the stability analysis, four models for predicting the overburden movement in response to underground mining were developed and the predictive system was then devised. (3) The mechanisms of aquifer-protection mining of general shallow coal seam were revealed and an applicability classification system was constructed. The mechanism of the mining-induced seepage in the aquiclude was identified and evaluated on the basis of the key index, say the thickness ratio of aquifer to aqui-clude. The intact fractured zone was divided into the following three parts, the upper, the middle and the lower, contributing to indicating the possibility of fracture closure. Based on the analysis of aquifer-protection ability evolution of aquiclude associated with underground mining, aquifer-protection mechanisms and a technology design system were present. The position ratio of aquiclude to fractured zone was selected as a comprehensive index to classify the applicability of aquifer-protection mining tech-nology.(4) The structural mechanical model of the slope involved in the mining under gully was built and the applicability classification for the related aquifer-protection mining technology was conducted on basis of the aquifer protection mechanisms.The support capacity was formulated based on the stability analysis of slope in-volved in the gully-ward mining or gully-away mining. The aquifer-protection mechanisms related to shallow coal seam mining under gully were present according to the water loss mechanisms of running downward and bedding flow in gully-ward mining and of updip transmission in gully-away mining. The sensibility of gully slope to underground mining was developed to classify the applicability of aqui-fer-protection mining technology under gully.145 figures, 31 tables and 221 references are imbedded in this dissertation.