As coal mining deepens, complex geological structures and mining disturbances increasingly compromise groundwater stability; however, the associated groundwater heterogeneity and vulnerability remain insufficiently investigated in the deep mine groundwater. To address this issue, this study integrated hydrochemical parameters with mining and natural factors to evaluate the Carboniferous Limestone Aquifer (CLA) at the Xieqiao Coal Mine. Hierarchical cluster analysis, principal component analysis, Factor Analysis-CRITIC-Game Theory, and spatial autocorrelation were employed to reveal the intrinsic coupling between groundwater heterogeneity and vulnerability, thereby elucidating the driving mechanisms. Subsequently, the model's reliability was further validated through correlation analysis with three groundwater quality parameters: Total Dissolved Solids (TDS), Cl-, and the Sodium Adsorption Ratio (SAR). The results revealed significant differences in groundwater heterogeneity and vulnerability among groundwater clusters, primarily governed by geological structures and mining disturbances. Influenced by mining disturbances or faults, the aggregation patterns of multiple water-rock interactions in high-vulnerability and low-vulnerability areas of the CLA groundwater are negatively correlated, spatially manifesting as low-high or high-low aggregation. Influenced by karst collapse columns, the aggregation patterns of multiple water-rock interactions in high-vulnerability areas of the CLA groundwater exhibit a positive correlation and spatially manifest as high-high aggregation. The Factor Analysis-CRITIC-Game Theory model demonstrated stronger correlations with groundwater quality parameters than the GOD model, with the coefficients of determination increasing by 0.2718, 0.3016, and 0.0495 for TDS, Cl-, and SAR, respectively. This study offers novel insights into the evolution of deep groundwater heterogeneity and vulnerability in coal mines, providing a scientific basis for resource management.

ObjectiveCurtain walls, recognized as a primary project for the prevention and control of water disasters in coal mines, will change the dynamic field of groundwater. Furthermore, their dissolution will affect the chemical field of groundwater, leading to variations in its hydrochemical composition. MethodsThis study investigated the Jurassic conglomerate aquifers in the Zhuxianzhuang Coal Mine, Huaibei coal field. Based on the statistics of conventional hydrochemical composition, Piper diagrams, ion combination proportions, and principal component analysis (PCA), this study explored the impacts of curtain walls on the hydrochemistry of the aquifers and determined the spatiotemporal hydrochemical evolutionary patterns under the influence of the curtain walls. Results and Conclusions The results indicate that the hydrochemical characteristics differ greatly between inside and outside the curtain walls, with the groundwater inside the curtain walls exhibiting elevated Ca2+ and Mg2+ concentrations compared to that outside the curtain walls. After the construction of the curtain walls, the hydrochemical processes are dominated by the dissolution of the curtain walls based on the leaching and dissolution of calcite (CaCO3) and dolomite (CaMg(CO3)2), accompanied by varying degrees of pyrite oxidation, alternating adsorption of cations, and desulfurization. Influenced by mining, the dissolution of the curtain walls produces significantly enhanced impacts on groundwater within them, with the dissolution of the northern curtain wall relatively weaker than that of the eastern counterpart. The results of this study will provide theoretical support for the monitoring and protection of curtain walls and the environmental protection of groundwater.

Hierarchical cluster analysis, principal component analysis, hydrochemical illustration, and objective weighting were used to study the hydrochemical characteristics and types of water–rock interaction of the groundwater in a typical North China Coalfield mine. The geological conditions and the mining disturbance were quantitatively evaluated, and mechanisms by which they affected hydrochemical evolution were elucidated. The results show that there are three types of groundwater in the coal measures: one with high Ca2+, Mg2+, and SO42−, which is oxidized disturbed water; another featuring high Na+ and HCO3−, which is reduced disturbed water; and one with low ionic content, making it undisturbed water. The coefficients of geological complexity and mining disturbance intensity exhibited spatial variability, with maximum values of 0.46 and 0.8, respectively. Less oxidation of pyrite and less dissolution of carbonate and sulphate was correlated with increased geological complexity, while enhanced cation exchange and sulphate reduction correlated with decreased geological complexity.

Systematically studying the hydrochemical evolution of bedrock groundwater in mining areas during mining process is crucial for effective groundwater resource management and coal mine production. The spatiotemporal characteristics and hydrochemical evolution patterns of the Permian fractured sandstone aquifer (PA) and the Carboniferous Taiyuan Formation limestone aquifer (CTA), both of which are directly associated with coal mining in the northern Linhuan mining area, China, were investigated using multivariate statistical analyses, hydrochemical graphical methods, ion ratio analysis, and a conceptual model. 72 groundwater samples, collected before and after mining, were classified into four groups by hierarchical cluster analysis (HCA). Principal component analysis (PCA) and ion ratio analysis indicated that water-rock interactions involve mineral dissolution (carbonates, gypsum, dolomite, silicates), cation exchange, and common ion effects. Hydrochemical evolution is influenced by bedrock paleotopography, aquifer hydraulic conductivity, and mining drainage. Paletopographic differences significantly influence water-rock interactions and spatial variability in hydrochemistry, with ion concentrations in groundwater increasing as paleotopographic elevation decreases. The pattern of hydraulic conductivity reflects the control exerted by variations in aquifer characteristics on mineral dissolution, leading to minor changes in hydrochemical characteristics. Mining activities disrupt the aquifer's reducing environment, resulting in a significant increase in groundwater SO42- concentration. These findings provide insights and a solid theoretical foundation for studying the hydrochemical variations patterns of groundwater and these control mechanisms in the hidden coal fields of North China.

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.

Taking the first stage project of Yan'an new district as research area ,three different numerical mod-els under the conditions of no-hardening and no-drainage ,hardening and no-drainage ,hardening and drainage are established by FEFLOW .After 50 years of long-term numerical simulation ,the distribution of groundwa-ter level ,burial depth ,amplitude of variation and dynamic change of groundwater level under the three condi-tions are analyzed .Meanwhile ,the spatio-temporal distribution of groundwater level and the evolution mecha-nism of groundwater flow field under the influence of excavating and filling engineering are investigated .The results show that the original landform would control the groundwater flow field after implementing excava-ting and filling engineering ,and the artificial gravel drain plays an auxiliary role in accelerating groundwater draw dow n .T he rainfall infiltration and the area of the loess collapsibility w ould be reduced by the hardening measure ,the groundwater level in the upstream and excavation area would be accelerated to steady state by artificial gravel drain .Hardening measure and artificial gravel drain make the groundwater level rise about 4~8 m in the filling area and decrease about 4~10 m in the excavation area and in the upstream .In the early simulation period ,the dewatering efficiency of the secondary artificial gravel drain is higher than that of the main artificial gravel drain ,and the main artificial gravel drain has a great effect on groundwater collection . However ,the main artificial gravel drain will act the main function for water drainage in the 40-year simula-tion period .T he results can provide theoretical basis for preventing the geological disaster in excavating and filling engineering in the loess hilly and gully area .

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.

Conventional ions (K++Na+、Ca2+、Mg2+、Cl-、SO2-4、HCO-3、CO2-3), pH value and TDS of main inrush aquifers including the fourth aquifer of unconsolidated formation,the fissured aquifer of coal measure and the karst aquifer of Taiyuan formation in the Suxian mining area were collected to choose the appropriate ground-water flow path and mineral phase. Based on the groundwater flow path and the mineral phase, the hydrogeo-chemical model was established to quantitatively simulate the hydrogeochemical evolution in the mining area. From the simulation, the fourth aquifer of unconsolidated formation had a close hydraulic connection and was characterized by the pyrite oxidation and the cation exchange and adsorption in the water-rock interaction. The fissured aquifer of coal measure had poor groundwater runoff condition so that the pyrite oxidation and the cation exchange and adsorption tended to be stable. The east-middle of karst aquifer of Taiyuan formation with good hydrodynamic condition was characterized by the carbonate dissolution-precipitation while the western with bad hydrodynamic condition was characterized by the pyrite oxidation and the cation exchange and adsorption. The research hopefully provides a theoretical support for the prevention and treatment of mine water hazard and also for the exploitation and utilization of groundwater in the concealed coal mining area in North China.

In order to give prominence to fundamental significance of rare earth elements in application of tracing ground water circulation in deep aquifers,the main inrush aquifers of deep mining such as the fourth aquifer of unconsolidated formation,the coal sandstone fissure aquifer,the Carboniferous karst aquifer of Taiyuan formation and the Ordovician karst aquifer in Suxian-linhuan mining area were taken for example,and geochemistry parameters of rare earth elements(LREE/HREE,(La/Yb) N,δEu,δCe,(La/Sm) N,(Gd/Yb) N and Eu/Sm) and conventional ions (K + + Na +,Ca2 +,Mg2 +,SO42-,Cl-,HCO3-and CO32-) of ground water samples from the main inrush aquifers were selected as analyzing variables of principal component analysis.Through the comparative study of principal component analysis,the controlling elements of geochemistry parameters of rare earth elements and hydrogeochemical principle of fractionation of rare earth elements in deep ground water were illuminated.Moreover,based on the conceptualization of geological and hydrogeological conditions and the study of distribution and fractionation of rare earth elements in the mining area,the deep groundwater circulation pattern was put forward that the water source recharges the main inrush aquifers through three paths of nearly horizontal seepage,nearly vertical seepage and mixed seepage.The results provided theoretical basis for prevention and control of deep groundwater disasters,protection and utilization of deep groundwater resources in mining areas.

In order to study the degree of influence and control mechanism to groundwater flow field caused by land creation engineering in the hilly and gully area of the Loess Plateau, based on the geological and engineering conditions of the first stage project of Yan’an new district in China, numerical simulation of groundwater flow is carried out by the Feflow and GIS technologies. From the simulation, punning measure relatively reduces infiltration recharge and artificial gravel drain increases groundwater seepage. The basic characteristics of groundwater flow field is controlled by the old and new topographies in the whole study area, and artificial gravel drain plays an auxiliary role in accelerating groundwater drawdown upstream and promotes groundwater rise downstream. According to differences of groundwater level and declining percentages of hydraulic gradient in the main and secondary gullies, dewatering of artificial gravel drain in the secondary gully is more effective than that in the main gully, which will yet play an important role in the future. The study results will make contributions to understand groundwater response to land creation engineering and will be beneficial to take necessary measures to prevent collapse of loess and failure of building foundation in the hilly and gully area of the Loess Plateau.

From November 2015 to February 2016, five short-term tracer injections were performed with a conservative tracer (NaCl) in an agricultural headwater stream, Lake Chaohu basin. Thus the data sets of tracer experiments were finally employed for calculating the physical characteristics and transient storage metrics. Through the comparisons between the artificial pool reach and straight reach, characteristics of transient storage for the artificial pool geomorphic structure were interpreted and explored. Study results showed that: ① The ratio of As/A in artificial pool was larger than that in straight reach, whereas its value of exchange coefficient α was lower by an order of magnitude than that of straight reach. ② Artificial pool geomorphic structure had greater influence of transient storage on solute retention than that in straight reach, but its solute retention capacity of flowing water was weaker than that of straight reach. ③ It had a large ratio of As/A for the pool geomorphic structure, whereas its impact on the migration and transformation of solutes was less than that of straight reach. ④ Based on the Fmed200 metric, the transient storage accounted for 18.86% to 26.05% of travel time in artificial pool. For the straight reach, the Fmed200 metric had a range of 5.28% to 33.87%. In most cases, the values of Fmed200 metric in straight reach were higher than those in artificial pool. ⑤ Significant differences existed between artificial pool geomorphic structure and straight reach in the values of φw, φA and Ts, however, the differences were not significant in other indicators.

为解析大型水生植物大量生长情形的源头溪流营养盐滞留的水文、生物作用贡献,于2014年9月-2015年6月在南淝河流域某一芦苇占显著优势的农田源头溪流段,开展8次野外示踪实验,计算渠段雷诺数Re、弗劳德数Fr、曼宁糙率系数n等水动力学参数,估算NH4+、PO43-的总滞留率以及水文、生物过程的实际滞留贡献率和相对滞留贡献率.结果表明,整个研究期间溪流水体表现出显著的紊流特征,水流流态属于缓流类型,渠道曼宁糙率系数n变化范围为0.066～0.112,平均值为0.089;NH4+总滞留损失率变化范围为9.17％～ 28.27％,平均值为14.68％,水文作用和生物过程对NH4+实际滞留贡献率平均值分别为10.12％和4.57％,相对贡献率平均值分别为72.51％和27.49％,表明NH4+滞留损失主要来自水文过程的影响;PO43-总滞留损失率变化范围为5.75％～17.79％,平均值为12.53％,水文作用和生物过程对pO43-实际滞留贡献率平均值分别为10.12％和2.41％,相对贡献率平均值分别为81.42％和18.58％,表明PO43-滞留损失也主要来自水文因素的影响;n与Re、Fr和Q均呈显著的幂函数关系,而实际滞留率ηNH4、ηPO4与n、Re之间均没有表现出明显的相关关系.

To analyze the dynamic failure process around a circular cavern in hard and brittle rock under high and increasing natural stress conditions, an 800x800x800-mm physical model with a phi 160-mm circular cavern in the center was produced by using the self-developed physical model material and tested in the self-developed model test machine under plane-strain conditions. From the physical simulation, when Px=Pz=600kN (sigma X=sigma Z=3.75MPa), shallow skinlike flakes appeared on the cavern wall, and large-scale abrupt failure occurred during a limited loading-zone for a short time until Px=Pz=630kN (sigma X=sigma Z3.94MPa). Then, a relatively steady state was followed by a long period with the load increasing. To understand the mechanical behavior around the circular cavern better, in the light of the physical simulation, a numerical simulation was also applied for comparative analysis. Both the numerical simulation and the physical simulation were consistent with each other, and they presented the same failure mechanism. (C) 2014 American Society of Civil Engineers.

Conventional hydrogeochemical data and environmental stable isotopes are used to identify the recharge sources and the water–rock interactions in the groundwater-flowing direction within the multilayer groundwater system of the Sulin coal-mining district in the north Anhui province in China. δD and δ 18O of groundwater in the mining district decrease along the groundwater-flowing direction in the recharge areas, yet in the runoff or discharge areas, they rise and fall along average δ values (δ 18O = −8.68 ‰, δD = −67.4 ‰), which are lower than average δ values of local atmospheric precipitation (δ 18O = −7.80 ‰, δD = −52.4 ‰). Principal component analysis is used to analyze the conventional hydrogeochemical data (K+ + Na+, Mg2+, Ca2+, Cl−, SO4 2−, HCO3 −, CO3 2−) in the groundwater. The first and second principal components have large variance contributions, and represent “pyrite oxidation or groundwater hardening” and “desulfurization or cation exchange and adsorption,” respectively. From conventional hydrogeochemical data and environmental stable isotopes, it is demonstrated that groundwater of the Sulin coal-mining district is characterized by a mixing type, which is confirmed by three recharge end-members: fresh groundwater, leaching groundwater, and retained groundwater. By means of a sample dot-encompassed triangle in the scatter diagram of load scores for Component 1–Component 2, whose vertexes stand for the three end-members, a model for calculating groundwater mixing ratio is established and applied successfully to the evaluation and management of groundwater hazards in the coal-mining districts.

In order to illuminate the mechanism of water-rock interaction indeep aquifers in the concealed coal mining area in North China , this study took the Suxian-linhuan Mining Area in Huaibei coalfield for example , and 166 groundwater samples in 1985 to 2011 were collected or gathered ,which belonged to the fourth aquifer of unconsolidated formation , the coal sandstone fissure aquifer , the Carboniferous karst aquifer of Taiyuan formation and the ordovician karst aquifer. 87 Sr / 86 Sr ,34 S and 13 C of these groundwater sampleswere tested , as well as conventional components such as Na + +K + , Ca2+ , Mg2+ , HCO-3 , Cl- , SO2-4 , CO2-3 .Moreover , tracing and analysis of the water-rock interaction indeep aquifers were carried out based on isotopes and hydrochemistry.The results suggest that , among the maindischarge aquifers in the mining area , the coal sandstone fissure aquifer is predominantly characterized bydesulfurizing or cation exchange absorption ,whereas , the fourth aquifer of unconsolidated formation , the Carboniferous karst aquifer of Taiyuan formation and the ordovician karst aquifer are predominantly characterized by pyrite oxidation or hardening.The results also suggest that , under mining-induced disturbance , the primary water-rock interaction tends toweaken for the coal sandstone fissure aquifer and the ordovician karst aquifer , yet , the primarywater-rock interaction tends toweaken or strengthen for the fourth aquifer of unconsolidated formation and the Carboniferous karst aquifer of Taiyuan formation ,which is controlled by the bedrock level , the fault location and itswater-resisting property , the extent of mining-induced disturbance in the mine.

In order to reveal the circulation mechanism of deep groundwater under mining-induced disturbance,thus accurately predict the type of water inrush,hydrogen and oxygen stable isotope tracing technique is adopted in this study in Su-Lin Mining District in Huaibei coalfield,to analyze the circulation process and recharge sources of groundwater in mining area,and to determine the groundwater mixing linear endmembers and calculate its mixing ratio.The research results show that:the value of δ decreases along the groundwater flow direction in the aquifer recharge area,yet it is constant in runoff or discharge areas;the mixing linear endmembers in mining area are direct infiltration water of precipitation,retained infiltration water or palaeo-water;the mixing ratio of linear endmembers is quite different because of mining-induced disturbance and water inrush.Therefore,only when the dynamic change trend has been determined,the water inrush source during mining can be well speculated.Finally,the theoretical basis for the prediction of mine water inrush and the protection of groundwater resource can be provided.

In order to reproduce influence degree and control mechanism of mining disturbance to main discharge aquifers,numerical simulation of recent seepage field characteristics of the fourth aquifer of the Quaternary,the coal measures aquifer,the Taiyuan formation limestone aquifer and the Ordovician limestone aquifer is carried out with the help of FEFLOW software after establishing conceptual model,mathematical model and corresponding numerical model in the groundwater system based on the systematic analysis of Renlou Mine's geological and hydrogeological conditions.By plane analysis,the fourth aquifer of the Quaternary shows a low water level distribution zone in the eastern part of the mine and the seepage is unconventional near typical faults in mining disturbance area in the coal measures aquifer.By space analysis,vertical water level isolines in mining disturbance area in the coal measures aquifer show deflexion and nearly parallel to roof and floor of the aquifer,and the water level isolines in the aquifuge between the fourth aquifer of the Quaternary and the coal measures aquifer are also nearly parallel,but those parallel isolines become dense in mining disturbance area.The groundwater flow of the Taiyuan formation limestone aquifer and the Ordovician limestone aquifer is in a former way by plane and space analysis.Therefore,the fourth aquifer of the Quaternary and the coal measures aquifer in Renlou Mine are observably influenced by mining disturbance recently.

In order to illustrate the hydrochemical evolution law of groundwater in the concealed coal mines in North China, taking the Renlou mine in Huaibei coal field for example, hierarchical cluster analysis and principal component analysis are used to analyze the conventional hydrochemical data(K++Na+, Mg2+, Ca2+, Cl, SO42,HCO3 and CO32) of the fourth aquifer of the Quaternary, the coal measures, Taiyuan Formation limestone and Ordovician limestone. Based on these analysis, different hydrochemical types are partitioned and hydrochemical formation conditions are clarified accordingly. Research results show that "desulfurizing" suggests increasing closeness in the groundwater system and decreasing mining disturbance while "hardening" suggests decreasing closeness in the groundwater system and increasing mining disturbance, and "salinizing" lies in "desulfurizing" and"hardening" process. Because of mining disturbance and "salinizing", "desulfurizing" and "hardening" show almost opposite trends in the groundwater system.

In order to find out the recharge condition in deep aquifers in the concealed type colliery in the north of China,taking Renlou colliery and the local Linhuan coal-mining district for example,hydrochemical systemic cluster analysis and hydrogen and oxygen isotopes tracing were carried out to discuss and analyze the recharge sources and its changing mechanism in the deep aquifers under the influence of mining activities.The deep groundwater of the coal-mining district was composed of direct but nonuniform infiltration and retention infiltration of precipitation and ancient underground water.In the case of TDS of deep groundwater at less than 1 000 mg/L,the δ values of stable hydrogen(D) and oxygen isotopes(18O) decreased with the increase of TDS in the coal-mining district.However,in the case of TDS of deep groundwater at higher than 1 000 mg/L,the δ values were around the average ones.In addition,the average δ values of D and 18O were-67.4‰ and-8.68‰ respectively,being relatively small compared with that of precipitation in the coal-mining district.Without the influence of mining activities,the deep groundwater of the coal-mining district was formed by the direct but nonuniform infiltration of precipitation.However,under the influence of mining activities,the deep groundwater of the coal-mining district was formed by the retention infiltration of precipitation,because mining activities had broken the original circulation condition of deep groundwater and the hydraulic alternate had been accelerated in the recharge area.