Study On Formation Mechanism-Prediction Analysis Of Geologic Hazards In Fushun Coalfield

Geologic hazards are formed by a variety of natural geologic actions and human activities in the development and evolution of earth, more and more people start putting the emphasis on them especially in any mining area. Landslides, debris flows, rock bursts, etc. have been the cause of tragedies in most (if not all) ore-producing regions. If nature and society were to achieve harmony at the same time of economic development, people have to do their best to study formation mechanisms and space-time distribution of disasters, so as to do a good job in prevention and treatment of disasters.Fushun coalfield known as "coal city" in a history of beyond one hundred made an outstanding contribution to new China’s economic take-off and was built successively five coal mines-west and east open pits and Shengli, Longfeng, laohutai mines under ground. They triggered landslide, ground deformation, surface subsidence and collapse, ground fissures and rock burst during coal mining. These disasters gave rise to casualties, property losses, interruption of coal mining, and then have a profound influence on Fushun’s urban construction and people’s lives. Fushun coalfield now is in old age, also meaning in deep mining. It is clear that geological structure、lithology and stress banlance on geologic hazards’ development should be intensive research so as to definition of direction and depth of extraction with theoretical and practical significance.In this paper, we carried out the research of fault reactivation、 rock properties and hydromatics on hazard-forming mechamism and analog simulation, discussed hazard-type features and evolving rules on the base of geological background arising disasters against the characteristics of geological disasters-large depth、 wide range、 various types and strong influence. Thus we make a conclusion as follows:(1) Various-type campanied hazards arise densely, alternately. The appearance of ground fissures in west open pit indicate landslide formation and slope deformation. Ground fissures in Laohutai mine scatter around subsidence area. Fushun coalfield and surrounding regions are divided to13danger areas,3sensitive areas and2stable areas according to some hazard features-type、 distribution、 development danger and trend.(2) The main fault strike is NE, F1and F1A are the most important faults acting on geologic hazards in Fushun coalfield. Fault reactivation in direct relation to deep mining is local, partial and shallow. Apart from faults, incomplete reversed syncline, soft rocks and structure rocks also are critical factors to geologic hazards.(3) Water may reduce shear resistance on slope and increase down-sliding force due to gathering water in rock fissures.in addition, infiltration flowing in slope also increases down-sliding force. Hydration in clay minerals weakens bonding force between grains, lowers cohesive strength and destroys stable rocks. Coupling of hydration and infiltration lead to formation of sliding bodies and ground fissures under geological conditions of inhomogenous rocks and gathering fissures. Deep waste has an influence on ground deformation, ground fissures, ground subsidence and collapse(4) Local shallow fault reactivation and waste effect are the grounds for all kinds of hazards formation mechanism in Fushun coalfield.By way of Fast Lagrangian Analysis of Continua(FLAC) analysis of west open-pit north slope, deformation is considered to be difficult to enter granite gneiss region, mining depth avoid more than850m as much as possible. Surface subsidence trend is predicted by means of mathematics statistics. Prediction result shows future subsidence is centred in east and north areas, east subsidence is2000m added length and north subsidence is300m added length.(5) Measures including rational avoidance and valid prevention should be taken to tackle landslides, ground fissures and slope deformation of west open pit in order to lessen loss as possible on basis of reinforcing monitoring of fault reactivation and controlling mining depth.Measures governing ground deformation,ground fissures and ground subsidence in mining subsidence areas include monitoring, filling and grouting so as to lessen and relieve subsidence on basis of strictly controlling mining depth and range.