The distribution of fractures has a crucial influence on the connectivity of fractures. The discrete fracture network (DFN) model integrating the spatial variability of fracture distribution is of great significance for describing flow and solute transport behaviors in fractures. This study proposes a framework for simulating discrete fracture networks considering the spatial pattern and variability of fracture distributions. Three main types of fracture distributions were summarized, including fracture distributions with spatial continuous variation characteristics, spatial trend variation characteristics, and spatial division characteristics. The kriging interpolation and spatial trend function or spatial distribution function were used to generate the spatial distribution of the facture quantity, and then the Monte Carlo method was employed to establish the DFN model based on the spatial distribution of the facture quantity. Two DFN cases with different fracture distribution types were designed to evaluate the rationality of the DFN model built with the proposed method. The results show that the root mean square error (RMSE) of the fracture quantification distribution of the DFN model is greatly reduced compared with that of the DFN model built with the traditional Monte Carlo method, and the RMSE of the hydraulic head distribution is also greatly reduced. The application of these cases illustrates that the proposed discrete fracture network stochastic simulation integrating the spatial variability of fracture distribution can better approximate the real distribution of fracture quantity.

Pore-fractured media is a ubiquitous phenomenon throughout the world and is a high degree of heterogeneity. The mechanism of water flow and solute transport in the media is still not fully clear. In this study, experiments were conducted in pore-fracture media with various hydraulic gradients to establish the relationship between the hydraulic gradient and specific discharge by using a side guide and to test the resistivity of tracer (sodium chloride) by using a high-density resistivity monitoring system. Quantifying models were, respectively, set up, and results were compared with the traditional methods. Main results are obtained that (1) the phenomenon from Darcian flow to non-Darcian flow was found in pore-fractured media. Both the Forchheimer and Izbash equations can well describe the flow process in the back part of the curve; (2) the phenomenon from non-Fickian to Fickian then to non-Fickian was found in fractured media; (3) good performance of CTRW-TPL has been obtained for both the larger R-2 and smaller RMSE values, their counterparts resulting from the ADE model.

The hydrodynamic dispersion is an important factor influencing the reactive solute transport in the porous media, and many previous studies assumed that it linearly varied with the average velocity of the groundwater flow. Actually, such linear relationship has been challenged by more and more experimental observations, even in homogeneous media. In this study, we aim to investigate the relationship between hydrodynamics dispersion and the flow velocity in different types of porous media through a laboratory-controlled experiment. The results indicate that (1) the dispersion coefficient should not be a linear function of the flow velocity when the relationship between the flow velocity and the hydraulic gradient can be described by Darcy’s law satisfactorily; (2) Power function works well in describing the dispersion coefficient changing with the flow velocity for different types of porous media, and the power value is between 1.0-2.0 for different particle sizes.

The determination of groundwater hydrochemical facies (GHF) is useful for analyzing the chemical composition of groundwater, tracking sources of groundwater recharge and assessing how its chemical composition changes along groundwater flowpaths due to water–rock interactions. This paper proposes a geographical information systems (GIS)-based method for identifying and mapping the spatial distribution of GHF categories in an aquifer. Several procedures including spatial interpolation, raster reclassification, raster-to-vector conversion, spatial union overlay, and generalization methods are coupled in GIS tools to determine the type and distribution of GHF categories. This method was implemented to distinguish shallow GHF categories for a shallow aquifer near Fuyang City in Anhui Province, China. The results obtained from the GIS assessment of water quality data from 30 wells show there were seven types of hydrochemical facies identified in the study area. The major GHFs categories are HCO3–Na + K + Ca + Mg, HCO3–Ca + Mg, HCO3–Na + K + Ca, and HCO3–Na + K, which cover 94% of the total area. The GIS method correctly identified the GHF categories determined in 80% of the wells in the area. The major GHFs categories progressively change in the direction of groundwater flow from HCO3–Ca + Mg to HCO3–Na + K+Ca + Mg, then to HCO3–Na + K + Ca, and then to HCO3–Na + K. The changes in the proportions of major ions in groundwater, coupled with salinity increases in the direction of groundwater flow are due to the combined effects of water–rock interactions in the aquifer and human activities. The method can relatively efficiently identify and map GHF zones for aquifers.

为了研究透镜体对污染物运移的影响,文章设计了二维承压含水层物理模型,以惰性溶质亮蓝为例,开展了不同流速下多孔介质溶质运移实验和模拟研究.研究结果表明:透镜体加入模型后,污染物会优先从透镜体周围流过,出现绕流现象,透镜体对溶质运移具有明显的阻碍作用;采用解析解模型和IGW(Interac-tive Groundwater)模型对溶质运移穿透曲线进行拟合,都出现早到和拖尾等非费克现象,IGW模型拟合精度明显好于解析解模型,能较好地拟合溶质运移中的非费克现象;透镜体的存在相当于增加了介质的非均质性,因此含有透镜体时弥散系数D增大;当仅考虑流速变化时,D随着流速的增加而变大.

为了对非干扰条件下二维多孔介质中溶质运移现象进行量化研究,进而探索介质条件、水动力条件对二维溶质运移的影响.文章设计了二维承压含水层物理模型,运用图像分析法监测示踪剂质量浓度,开展了不同流速、不同粒径条件下多孔介质溶质运移实验研究,使用交互式地下水(Interactive Groundwater,IGW)模型对溶质运移穿透曲线进行了模拟,研究结果表明:相同流速不同粒径条件下,介质粒径小,亮蓝溶液先穿透,对应的峰值质量浓度小,且弥散系数随着介质粒径的减小而增大;相同粒径不同流速条件下,流速越大,到达峰值质量浓度的时间越短且峰值质量浓度越大,弥散系数随着流速的增大而增大;IGW模型总体拟合精度较高,存在拖尾现象,且这种现象随着流速减小及粒径减小而更明显.

Accurate prediction of solute transport processes in a fracture aquifer is an important task not only for proper management of the groundwater but also for pollution control. A key issue of this task is how to accurately obtain the experimental data and to analyze the solute transport in fracture in subsurface hydrology, which would greatly help us to understand the releasing mechanism and transport of the solute in a fracture. In this study, a fracture experiment is conducted in a laboratory based on previous studies. The fracture used with a length of 60 cm and a width of 10 cm is sealed with glass glue to avoid leakage of tracer due to uneven fracture walls. The sodium chloride (NaCl) solute is injected from the left of the fracture. And an electrical conductivity monitoring system is installed on the right of the fracture. Then breakthrough curves (BTCs) of solute transport are fitted using the classical advection-dispersion equation (ADE) and the truncation power-law function (TPL) model in the package of the continuous time random walk (CTRW). The results show that the flow satisfies non-Darcian law in the experimental conditions, which can be better fitted using the Forchheimer equation and Izbash equation. The solute transport presents non-Fickian phenomena and shows a long tailing. The fitting results of the TPL model are far better than ADE in fitting the long tailing at three different flow velocities. Furthermore, electrical conductivity monitoring method not only is effective but also has an advantage of no disturbance to water and concentration fields in a fracture.

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.

Laboratory experiments are designed in this paper using single fractures made of cement and coarse sand for a series of hydraulic tests under the conditions of different fracture apertures, and for the simulation of the evolution of the flow pattern at places far from the outlet. The relationship between the hydraulic gradient and the flow velocity at different points, and the proportion evolution of the linear and nonlinear portions in the Forchheimer formula are then discussed. Three major conclusions are obtained. First, the non-Darcian flow exists in a single fracture in different laboratory tests. Better fitting accuracy is obtained by using the Forchheimer formula than by using the Darcy law. Second, the proportion of the Darcy flow increases with the increase of the observation scale. In places far enough, the Darcy flow prevails, and the critical velocity between the non-Darcian flow and the Darcy flow decreases as the fracture aperture increases. Third, when the fracture aperture increases, the critical Reynolds number between the non-Darcian flow and the Darcy flow decreases.

The transport mechanism of groundwater flow in fractured media has a significant impact on the remediation of bedrock fracture water disaster and pollution repair .This study designs a single fracture model made of a mixture of cement and coarse sands (diameters between 1 .0 mm and 2 .0 mm) ,conducts a series of hydraulic tests under the conditions of confined-unconfined flow .The relationship between hydraulic gradient and flow rate of different points and the proportion evolution of the linear and nonlinear portion in Forchheimer formula were discussed respectively .Main conclusions are drawn:(1) Non-darcian flow presents under this single fracture experiment condition .Better fitting accuracy is obtained by using Forchheimer formula than Darcy's law . (2) The transition from non-Darcian to Darcy flow has an increase trend with the observation scale enlargement .When the distance is far enough ,it can be seen as the Darcy flow .(3) During the transition from the non-Darcian to Darcy flow ,the critical Reynolds number decreases with the fracture aperture increasing .

为了揭示单个裂隙中水流和溶质运移的规律,该文选取大理石平板作为实验介质,开展了平板裂隙水运移实验,分析了水力梯度和水流速度之间的关系,研究了溶质运移规律;利用连续时间随机步长(CTRW)软件包中的截断幂函数(TPL)模型对溶质浓度穿透曲线进行了模拟,并与传统的对流-弥散方程(ADE)模拟结果进行了对比.结果表明:实验条件下,大理石平板裂隙水流为非达西流,利用Forchheimer方程可以更好地模拟;大理石平板裂隙内溶质运移为no-Fickian运移,表现出明显的拖尾现象;在不同流速条件下模拟溶质穿透曲线时,利用TPL模型拟合结果明显优于ADE模型.

Discriminating the water inrush source of coal mine quickly and correctly is the precondition of water control. This paper described the BP neural network model and its specific algorithm, then applied it to the Panyi mine, The discriminating model is established from the training samples using BP algorithm and the hydro-chemical characteristics of Panyi mine. Then comparison with the fuzzy discriminate model, experimental results showed that the applying of the BP neural network to distinguish the water inrush source in mine produced a better effective. The accuracy rate is higher than fuzzy discriminate model. The BP neural network is an effective way to distinguishing the water inrush source in mine. It provides an assistant means for decision-making to prevent water-inrush in mine.

The denitrifying strain Klebsiella sp.DB-1 is chosen as the tested strain and the corn straw,straw,Phragmites Australis and Typha angustifolia are used as solid carbon sources for bioremediating the nitrate-contaminated soil.The purpose of this study is to find out a simple and cut-price method for the bioremediation of nitrate-contaminated soil which integrates multipurpose use of crops straw and bioremediation,and provide an experimental basis for the remediation of nitrate-contaminated soil in large acreage.The experimental results show that the four carbon sources can be used by the denitrifying strain Klebsiella sp.DB-1 to bioremediate the nitrate-contaminated soil effectively.The best alternative source is Typha angustifolia,and its best dosage is 5 g in 100 g soil,and high nitrate concentration in soil(200-250 mg/kg) can be removed to below 20 mg/kg within 108 hours.Keeping soil litmusless can promote the nitrate removal by the denitrifying strain.