1、翻译部分英文原文Investigations of water inrushes from aquifers under coal seams（Jincai Zhang）Abstract：In many coal mines, limestone-confined aquifers underlie coal seams. During coal extraction from these mines, water inrushes occur frequently with disastrous consequences. This paper introduces the hydrogeo
2、logical conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams. It then presents the water inrush mechanism. The main factorswhich control water inrushes include strata pressure, mining size, geologic structures and the water pressure in the underlying a
3、quifer. Analysis shows that reduction of confinement due to mining is the major cause of the water-conducting failure in the floor strata. The depth of the failure zone is strongly dependent on the mining width. This paper also presents field observation results of the water-conducting failure in th
4、e floor strata, and applies the finite element method coupled with stress-dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction. Finally, theoretical and empirical methods to predict water inrushes are given, and technical measures for improving mine design and
5、safety for coal extraction over aquifers are presented. These measures include fault and fracture grouting and mining method modification such as changing long-wall to short-wall Mining.Keywords: Water inrush; Coal mining; Confined aquifer; Strata failure; Stress and displacement; Hydraulic conducti
6、vity; Permeability1 Introduction China continues to rely on coal for about 75 percent of its energy. Therefore, coal production is of crucial importance for Chinas economy and development. However, mining operations in China are threatened by various kinds of groundwater during coal extractions. The
7、 most serious of the three main types of possible water disasters affecting the safe operation of coal mines 1 is water inrushes from the Ordovician limestone under the permo-Carboniferous coal seams in Northern China. The Ordovician limestone is a confined karst aquifer containing an abundant suppl
8、y of water and with a very high water pressure. Furthermore, the strata between coal seams and the aquifer are relatively thin, varying in thickness from 30 to 60 m. Due to these characteristics of the aquifer, plus mining-induced strata failure and inherent geological structures (such as water-cond
9、ucting faults, fractures) high-pressure groundwater can break through seam floors and burst into mining workings. Therefore, water inrushes from the aquifer occur frequently, and coal mines often suffer from serious water disasters during coal extractions. Water inrush incidents have shown that the
10、maximum water inflow in a coal mine has reached as much as 2053 m3/min 2, which submerged the mine in a very short time. According to incomplete official statistics, about 285 of 600 key coal mines in China are threatened by water inrushes during coal mining 2. The total coal reserves threatened by
11、bodies of water are estimated at 25 billion tons. For example, in Northern China, the yearly coal production from the Permo-Carboniferous coal-bearing formations is more than 200 million tons. However, the coal extraction has been threatened by frequent water inrushes from the Ordovician aquifer. In
12、 this region, the lower level seams which have more than half of the total coal reserves are much more difficult to mine due to this threat of water inrushes (Table 1).From 1950 to 1990, a total of 222 serious water inrush incidents took place in China causing collieries to be submerged by water int
13、rusions from the confined karst aquifers. More recently, total water inrushes at nationalized key coal mines occur about 125 times annually resulting in an economic loss of 1.5 billion Yuan (about 180 million US dollars). In addition, local coal mines run by provinces, counties, and private business
14、 have a larger annual economic loss induced by water inrushes.The main coalfields threatened by the Ordovician aquifer are Jiaozhuo in Henan Province, Fengfeng,Handan and Xingtai in Hebei Province, Zibo and Feicheng in Shandong Province, and Hancheng and Chenghe in Shaanxi Province. If the problems
15、of safe mining over the aquifer cannot be solved efficiently,some coal mines in the mentioned coalfields will be faced with gradual reduction of production or even abandonment of the mines. In general, there are two different ways of solving the problems of mining over confined aquifers. One is to d
16、rain the aquifer before mining operation, and the other is to mine without drainage. Geological investigation and mining practice have unveiled that there are many environmental problems induced by water drainage from limestone aquifers, such as the Ordovician limestone aquifer in Northern China and the Maokuo limestone aquifer in Southern China. Fissures in these karstified limestones are well developed and interconnected within the aquifer such that when wate
