| Xin'an Coalfield which spans Xin'an county and Mengjin county is one of Henan's main large coal fields, and is one of the four major coal fields Yima Coal Industry Group Co. Ltd., the area under -1000m is about 600 sq km, its coal resources is about 2.6 billion tons. The main commercial seam of the coalfield is No.â…¡1 coal, the part commercial seam is No.â…¡2 coal and No.â…§1 coal, etc. The coal ranks are salable high grade lean coal and blind coal, etc. Xin'an Coal Mine completed and put to production in 1998 which is one of large-sized key mines of Yima Coal Industry Group Co. Ltd. locates in the superficial part of Xin'an Coalfield, its area is 54 sq km, industrial reserves is 0.24 billion tons, designed annual production capacity is 1.5 million tons, the capital construction investment is close to 0.4 billion yuan. The designed storage capacity of the Xiaolangdi reservoir is 12.65 billion cubic meter, the effective storage capacity is 5.1 cubic meter, its area is 272 sq km. When the water level of the Xiaolangdi reservoir reach the highest impounded level (+275m), more than 50 sq km of the Xin'an Coalfield will be submerged, the capacity of coal under water is 0.25 billion tons, thereinto, the submerged area is 21.7 sq km, and the capacity of coal under water is 0.12 billion tons at the east wing of the Xin'an Coal Mine. After the Xiaolangdi reservoir is impounded, the local hydrogeologic condition and the filling water condition will gravely change, which gradually leads to water trouble of the mine and increase the difficulty of waterproofing, in the end, the mine hydrogeologic condition change to more complexity.Marine mining has a long history at home and abroad. Based on the safety, the foreign related provision for marine mining is too conservative, the study is lack for the growth laws of water conducted zone following mining, which resulted in the waste of lots of resources, such as: which the safe mining depth under the large water body of the earth's surface is 60 times of the working thickness is prescribed in USA. China's marine mining technology is leading the world. Since the liberation, China can widely exploit coal resources under various types of water bodies, and coal science and technology workers achieve a lot of results after lots of researches. As early as the 1980s, there are specific provisions for marine mining at "Mine Hydrogeologic Rule" and "Rules for Building, water body, railway, coal pillar design and mining pressed coal", based on the different rock characters and stratigraphic dip,etc., the empirical formulas for the maximum development height of the water conducted zone resulted from mining are put forward, these results have an important role in safe marine mining. But with the extensive application for the full-seam mining technology of the top-coal caving and the high yield and high efficient working face of large reserves, the mining technology significantly changed, the former empirical formulas for the maximum development height of the water conducted zone resulted is no longer applicable. And the application scope of the given empirical formulas is too broad, the rock characters combination and the stratigraphic dip of mine carried out marine mining differ in thousands ways, using the same formulas results in lack of accuracy. There will be relative deviations if mechanically using the empirical formulas in Xin'an Coalfield.By use of the theory of hydrogeology, the dissertation researches the local hydrogeologic condition. The region's main aquifer is the Ordovician and the Cambrian karst fissures confined aquifer. The aquifer has large thickness and strong water abundance, it exposes in northwest coalfield on a large scale. Before the Xiaolangdi reservoir impounds, limestone aquifer receives precipitation supply in the exposed area, then, groundwater runs off from the northwest to the southeast, when encounters stagnation flow zone in the deep coalfield, then, groundwater immigrates to north-east, in the end, groundwater discharges at the Yellow River. When the reservoir water level rising, the drain outlet of groundwater will be feeder channel, the reservoir will also be supply source of groundwater, on the other end, when the reservoir water level descending, the drain outlet resume its original features. Because of the intermittent supply source of the reservoir, the underground water level raise to a certain extent, however, it cyclically moves with the Xiaolangdi reservoir impoundment and discharge.The dissertation researched the factors of the mine water trouble. There are only a few of seasonal rivers on the surface of Xin'an Coalfield, such as Zhen River, Shisi River and Beiye River, these rivers play a limited role in water filling mine. After impoundment, surface water will be one of a important water filling factors. There ever exists hundreds of small mines varying in scale in the shallow part of the Xin'an Coalfield, among dozens of small mine lie in the inundated region, in addition, small coal mined-out areas connect with each other, resulting in water inrush from the small coal mines and surface water together, which has a major flood threat against Xin'an coal mine and other big mines. Because of the aquifer of attaining adequate water supply from surface water and water inrush from the small coal mines, reduced runoff and other reasons, the water filling function is reinforced. So, during the course of exploitation, the upper part of Xin'an Coalfield is threatened by water reservoir, the lower by a threat of Ordovician limestone water, the limestone by a threat of water inrush from the small coal mines.The dissertation studied the growth laws of water conducted zone following mining. By use of three groups drilling (the ground drilling K3, the upholes Y1 and Y2 on 11201 working face; the ground drilling K7, the upholes Y5 and Y6 on 14141 working face on three working faces; the ground drillings K5 and K6, the uphole Y3 on 14191 working face) at Xin'an coal mine, the overburden rock on No.â…¡1 coal is wholly sampled, and then the physical and mechanical properties of the rock is tested for receiving rock strength and other basic parameters in laboratory. The probable horizon of water conducted zone is determined through the amount of leakage of drilling fluid. According to the advancing situation of working face, virgin fracture is tested by ultrasonic imaging technique before exploitation, after exploiting a half month to three months, the working face is conducted the second test for exploitation fractures, six months later, the third test for closure fractures. By comparing the fore-and-aft test results, the growth rules of exploitation fractures are more intuitively reflected. The production of working face is tracked by parallel electrical network CT technology, the dynamic growth course of exploitation fractures with advancing working face is described at last. Combined with the results of physical simulation, numerical simulation and site test, according to the rock signatures and mining ways and other actual situations and features at the top of coal vein, the calculation methods of the water conducted zone height suited to the Xin'an coal mine are summarized.The dissertation appraises the security for marine mining in Xin'an Coalfield by the analysis of the rock signatures and combinations of the rock stratum on No.â…¡1, coal thickness and its varying, depth of coal seam, the maximum growth height of water conducted zone, the Quaternary system loose aquifer status and the depth of surface water, drillings and its closure status, water barrier and other factors.The dissertation put forward the marine mining technologies of surface water proofing in Xin'an Coalfield, such as the treatment to close the bad drillings in inundated land, geologic structure exploration by three dimensional seismic prospecting in inundated land, the dynamic real time supervision for the reservoir water level, the water proofing technologies for mining well, mining district and working face, the examination by physical prospection and verification by drilling, the design of water barrier and cutoff wall, delaying mining and the parameters choice of marine mining working face, and so on.After study, it is found that, if the related surface water proofing measures can be ensured, it is safe to carry out marine mining in the most region of the Xin'an Coalfield. The surface water proofing research of marine mining under the Xiaolangdi Reservoir can liberate the underwater coal about 0.1 billion tons, on the other hand can be used for references for other coal mines, so as to ease China and the world current tense supply of resources at a certain extent, it is evident that there is a significant social and economic benefits. |
PDF Full Text Request