Engineering Geological Studies On The Geodisaster Caused By Coal Mining In Xiangyuan County

According to the formation and the harming objects, the Geological Disaster caused by coal mining in Xiangyuan county can be divided into two sorts, namely direct and derivative geodisaster. The direct geodisaster includes water irruption, coal spontaneous combustion, caving, coal grime etc. For example, water irruption at Wuyang Mine in 1988 and coal spontaneous combustion at Beimahan Mine in 1999. The second one includes subsidence, rupture, pit, landslide, mud-rock flow etc. In this paper, the derivative geodisaster is the main discussing object.Each kind of the geological disasters has its particular formation mechanism and distribution pattern in Xiangyuan county, which can be divided three parts, the east, the middle and the west according to the influencing factors and occurring frequency of geodisasters in the space. The middle part is the alluvium plain of Zhanghe River and the main mining area, being the most serious development area of the geological disasters, containing the subsidence, the rupture, the pit, the landslide and the mud-rock flow. The geodisaster in the east is fewer than in the middle, containing landslide, landslip and rupture, which were caused by road digging. In the west, there is scarcely any geodisaster. Based on the study, the occurrence of the geodisaster in Xiangyuan county is concerned with the geological background and 'human beings' engineering actions. Terrain and physiognomy is an influence factor to the distributing of the geodisasters. There are different kinds of geodisasters in the Thick soil area and fault belt area. The large subsidence caused by large mine is main at the area of integrate base rock coverd thick soil (in the middle and the north), and the pit and rupture are main at the area of faulted and fragmentary base rock(in the south).There is a sequence at the occurrence of the geodisaters, namely there are some evolution chains, which is closely connected with the development course of the subsidence. On the other hand, there is a delay time between the occurrence of the geodisater and the mining time and a successive phenomenon..There are a lot of influencing factors for the forming mechanism and the development rule, which can be divided into two kinds, natural and man-made. Embedding depth, water (precipitation and groundwater) and quality of the covered rock belong to the first, and mine technology, such as the size of mined-out area, the method of mining and roof rock managing etc are the second.Corresponding harnessing measures are studied for different geodisasters. According to "defend is main and combines with harnessing", the restricting to human engineering action, the city projecting reasonably, engineering harnessing, biological harnessing, avoiding and forecasting should be adopted.