1、英文原文Stability control of water-enriched roofs of coal driftsLI Xue-hua1,2, YAO Qiang-ling1,2, DING Xiao-lei1,2, WANG Yi-pin1,2, ZHANG Lei1,21 State Key Laboratory for Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou,Jiangsu 221008, China2 School of Mines, China Univers
2、ity of Mining & Technology, Xuzhou, Jiangsu 221116, ChinaAbstract: Excavation-and-support induced disturbances are likely to make water-enriched roofs to become weathered and fractured. The development and connection of cracks provide new water channels which may result in water loss, seriously affe
3、cting the integrity and stability of roofs, leading to incidents of roof fall. Control of water-enriched rocks surrounding coal drifts is quite difficult in China. Based on the practical situation of a water-enriched roof of a coal drift in working face 112201 of the Meihuajing coal mine, we studied
4、 the deformation features of surrounding rocks and the development of fractured areas and analyzed the major reasons for the decrease in load-carrying capacity, indicating that the key to maintain roof stability of this kind of coal drift is water retention. In addition, we proposed a staged control
5、 technology consisting of: 1) surface grouting; 2) cable anchor strengthening and 3) roof grouting, which has proven to be successful in this practical application. Our study indicates that, after the problem of water loss from the water-enriched roof had been effectively solved, a combined support
6、system with high performance bolts can maintain the stability of the bearing structure, resulting in the control of roof stability in this kind of coal drift.Keywords: aquifer; roof stability; water retention; staged control1 IntroductionThe problem of control of surrounding rock is very much a curr
7、ent topic in mining engineering projects. Since the Ninth Five-Year plan, China has made great progress in control technology of surrounding rock in coal roadway support. However, the problem of support technology under difficult conditions has not been completely resolved. With the aim of targeting
8、 this problem, we investigated more than 30 roof fall accidents in more than 50 coal mines near the eastern Ningxia, and near cities of Huaibei, Huainan, Xuzhou and Zibo. The results of the investigation are as follows: 50% of roof fall incidents are caused by water loss from or water seepage into t
9、he surrounding rock. A water-enriched roof is one of the major obstacles and threats in construction of coal roadways. In recent years, scientists at home and abroad have carried out extensive research on rock expansion, rheology, slumps and ion exchange caused by water-rock interaction and studied
10、abrupt changes in rock bearing capacity and deformation of surrounding rocks in the areas of mechanics and chemistry12. Water loss from rocks can result in slow but long lasting deterioration and may have a wide range of consequences37. Relative to the area, far less research has been directed to th
11、e chemical aspect of the problem. There is less knowledge of this field and a decisive lack of connection with engineering problems, both organically and systematically. As a result, we have blindly adopted various combinations of control technology in the past but have not been able to translate th
12、is into expected practical results. Therefore, in this study, we use stability control of the surrounding rock in a water-enriched roof in the Yanan formation of the Jurassic system, in eastern Ningxia as an example, to study certain engineering problems.2 Engineering situation of the Meihuajing coa
13、l mine2.1 Geological conditionsThe main coal seam to be mined in the 112101 working face of the Meihuajing coal mine is coal seam No.2-1 with a recoverable range thickness of 1.5 to 2.7 m, averaging about 1.88 m. The dip angle varies greatly from about 10 to 25. The roadways are 150 m underground.Ro
14、of: the immediate roof of seam 2-1 coal consists of siltstone silty mudstone and shale cementation. Its compressive strength is very low in a water-saturated state. Only 1%2% is dry. As well, its capacity for anti water immersion is poor, so that the roof becomes quite easily soft, which causes roof
15、 falls. Since its origin is Jurassic sandstone, the main roof is stable but its aquosity poor to moderate and yet, it is the most direct water filling aquifer. The average thickness of the sandstone is 42.94 m with a range of 17.59 to 82.50 m. Locally, there is a false roof, of mudstone lithology an
16、d a 0.5 m layer of carbon mudstone.Floor: the main rock of the floor is siltstone, with a certain amount of fine sandstone, gritstone and mudstone. It is about 2 to 4 m thick.The general characteristics of the roof and floor lithology are described in the following paragraphs.Because maturity remained low during their coal-forming stage, rocks are generally soft and loose. This is particularly true for mudstone and sandstone which are cemented by bauxite a
