Coal mining is bound to destroy natural hydrochemical environment. However, in the concealed coal field in North China, the hydrogeochemical characteristics of discharge aquifers under mining-induced disturbance has not been researched from view of space and time, and the true hydrochemical feature and spatio-temporal evolution mechanism could not be well revealed. For this reason, taking the Linhuan coal-mining district as study area, conventional ions and trace elements are studied by principal component analysis (PCA). The results show that main formations of hydrochemical composition are lixiviation and dissolution for the first principal component and cation exchange and absorption for the second principal component, respectively. In general, the main formation of hydrochemical composition in the unconsolidated pore aquifer is lixiviation and dissolution. The main formation in the coal and sandstone cranny aquifer is cation exchange and absorption, which are gradually weakened with lixiviation and dissolution. The main formation in the karst aquifer is lixiviation and dissolution, which are gradually strengthened with cation exchange and absorption. The research provides theoretical foundation for the water-inrush precaution and the protection and utilization of water resources in concealed coal field in North China.

Coal mining is bound to destroy the natural hydrochemical environment.However,hydrochemical studies of a groundwater system of multi-aquifer in the mining district rarely focus on the essence of hydrochemical evolution under the mining-induced disturbance in view of space and time.The Linhuan coalmining district is taken as an example to reveal the mechanism of water-rock interactions under the mininginduced disturbance by using the principal component analysis based on conventional ions over the years.The result shows that the first principal component represents the dissolution of carbonate and sulfate and oxidation of pyrite and the second principal component represents the exchange and adsorption of cation and desulphidation.Under the mining-induced disturbance,dissolution of carbonate and sulfate and oxidation of pyrite wear off in the main inrush-water aquifers in the mining district,but the change characteristics of exchange and adsorption of cation and desulphidation are insignificant.The research will provide a theoretical support for the identification of water-inrush source and also for the protection and utilization of groundwater in mining districts.

预应力混凝土竹节桩(简称“竹节桩”)是在普通预应力混凝土管桩(简称“管桩”)基础上改良而来的新桩型.文章介绍了竹节桩的构造和接桩技术,并通过现场静载试验,对竹节桩在软土地基中的承载性能进行了对比研究.试验表明:竹节桩的单桩竖向抗压极限承载力与管桩和预应力混凝土空心方桩(简称“方桩”)相比,均能提高20％左右,单桩竖向抗拔极限承载力比管桩提高60％以上.竹节桩由于设置了环向、纵向凸肋,改变了桩-土接触方式和桩身粗糙度,有利于桩侧摩阻力的充分发挥.在荷载水平较低时,桩顶位移曲线近似为直线,当荷载增加到一定程度时,会在土体中形成一个直径与环向凸肋大小相当的圆筒形剪切滑动面.

Barrier pillars are an effective and fundamental measure to prevent water inrush when mining shallow coal seams under an unconsolidated, confined aquifer. Based on the complex geological and hydrogeological conditions in the southern area of the Qidong coal mine, the no. 61 coal seam there was selected for a research demonstration. A fluid–solid coupled numerical simulation was carried out using the universal distinct element code. The hydraulic pressures and seepage rates in overlying strata were analyzed for two mining cases, near the aquifer and near the fault. The results showed that the degree of interconnection between the bed-separated and vertical fractures, and increases in hydraulic pressures and seepage rates in overlying strata were key factors in predicting potential water inrush when mining shallow coal seams under an unconsolidated, confined aquifer. Combining the numerical simulation results with China’s coal mining requirements, the no. 61 coal seam can be mined up to 90 m beneath the unconsolidated, confined aquifer, which limits mining to an altitude of −509.36 m. The width of the barrier pillar should be 30.7 m near the fault.

The unconsolidated Cenozoic formation is well developed in the Qidong coal mine. Water-inrushes from the bottom unconsolidated Cenozoic aquifer, which is the confined aquifer, have happened several times during mining in the north mining area of the Qidong coal mine. To predict the water-inrush risk areas in the south mining area of the Qidong coal mine where some working faces have just begun to mine, the engineering analogy method is used on basis of the Fisher's discriminant model from the actual mining situation in the north mining area. Six main influence factors including the effective thickness, the specific yield, and the load transfer coefficient of the aquifer, the effective thickness of the protective bedrock layer, the fractal dimensional value of bedrock faults and the distance between the key hard stratum and the primary mineable coal seam are selected as discriminant indexes, and their corresponding data in the north mining area of the Qidong coal mine are served as training samples. On this basis, the Fisher's discriminant model for water-inrush is established and water-inrush risk areas including the safety, the medium risk and the risk areas of no. 61, 82 and 9 primary mineable coal seams in the south mining area of the Qidong coal mine are predicted by the model. The model's accuracy is 90.4 %, the scatter diagram of training samples shows obviously classified effect and the field verification indicates that the predicted type is consistent with the actual type. Results show that the discriminant model is well applied in the engineering analogy method and the water-inrush risk areas predicted by the discriminant model contribute to the subsequent mining in the south mining area in the Qidong coal mine.

矿井突水是煤矿开采中经常遇到的地质灾害,严重威胁着煤矿的安全生产.为了快速判别突水水源,利用皖北宿(县)—临(涣)矿区生产矿井地面水位长期观测孔、井下放水孔以及井下出水点等处分别取新生界第四含水层、煤系砂岩裂隙含水层、石炭系太原组岩溶含水层及奥陶系岩溶含水层的42个稀土元素水样.采用现代统计学中的因子分析方法对矿区稀土元素的水文地球化学特征进行研究.提取了两个特征值大于1的公因子,两个因子的累计方差贡献率达到了93.055％,能够较全面的解释宿-临矿区大部分含水层的水化学信息;建立了用稀土元素作为分析变量判别突水含水层水源的Bayes模型,判别率高达93％,判别结果与因子分析结果相符.研究成果为煤矿开采中的突水水源判别提供了新的科学依据.

In order to study hydrogeological parameters of unconsolidated confined aquifer of North China type coal field and its significance to groundwater numerical simulation,the fourth aquifer of the Quarternary (4th aquifer)in Qidong coal mine,Sunan mining area,Huaibei coal field,Anhui Province,is studied as an exam-ple.Based on the hierarchical analysis-fuzzy comprehensive analysis method,the study area is divided into ten divisions under hydrogeological parameters of 4th aquifer.The hydrogeological parameters of each division are properly determined,which are used for dynamic numerical simulation of groundwater flow under mining cir-cumstances.The results of numerical simulation show that the variation of groundwater flow field is unconspicu-ous in the process of mining of shallow coal seam from 2008 to 2012 in Qidong coal mine,but the differences of groundwater level between the north and the south increases year by year;therefore,groundwater always flows from the south to the north,which hydraulic gradient decreases in the north and increases in the south gradual-ly.The results also show that the decrease zone and the increase zone of hydraulic gradients are separated by the Weimao fault with a dip of 60-70 degree and a slip of 10-320 meters.It is concluded that a fault with great dip and slip in the bedrock are keys to hydraulic gradient anomaly in the overlying unconsolidated confined aqui-fer.