Seepage field distribution and water inflow laws of tunnels in water-rich regions

Currently,the water inrush hazards during tunnel construction,the water leakage during tunnel operation,and the accompanying disturbances to the ecological environment have become the main problems that affect the structural safety of tunnels in water-rich regions.In this paper,a tunnel seepage model testing system was used to conduct experiments of the grouting circle and primary support with different permeability coefficients.The influences of the supporting structures on the water inflow laws and the distribution of the water pressure in the tunnel were analyzed.With the decrease in the permeability coefficient of the grouting circle or the primary support,the inflow rate of water into the tunnel showed a non-linear decreasing trend.In comparison,the water inflow reduction effect of grouting circle was much better than that of primary support.With the increase of the permeability coefficient of the grouting ring,the water pressure behind the primary lining increases gradually,while the water pressure behind the grouting ring decreases.Thus,the grouting of surrounding rock during the construction of water-rich tunnel can effectively weaken the hydraulic connection,reduce the influence range of seepage,and significantly reduce the decline of groundwater.Meanwhile,the seepage tests at different hydrostatic heads and hydrodynamic heads during tunnel operation period were also conducted.As the hydrostatic head decreased,the water pressure at each characteristic point decreased approximately linearly,and the water inflow rate also had a gradual downward trend.Under the action of hydrodynamic head,the water pressure had an obvious lagging effect,which was not conducive to the stability of the supporting structures,and it could be mitigated by actively regulating the drainage rate.Compared with the hydrostatic head,the hydrodynamic head could change the real-time rate of water inflow to the tunnel and broke the dynamic balance between the water pressure and water inflow rate,thereby affecting the stress state on the supporting structures.

Detection and treatment of water inflow in karst tunnel：A case study in Daba tunnel

In a karst tunnel, fissures or cracks that are filled with weathered materials are a type of potential water outlet as they are easily triggered and converted into groundwater outlets under the influence of high groundwater pressure. A terrible water inrush caused by potential water outlets can seriously hinder the project construction. Potential water outlets and water sources that surrounding the tunnel must be detected before water inflow can be treated. This paper provides a successful case of the detection and treatment of water inflow in a karst tunnel and proposes a potential water outlet detection(PWOD) method in which heavy rainfall(>50 mm/d) is considered a trigger for a potential water outlet. The Daba tunnel located in Hunan province, China, has been constructed in a karst stratum where the rock mass has been weathered intensely by the influence of two faults. Heavy rain triggered some potential water outlets, causing a serious water inrush. The PWOD method was applied in this project for the treatment of water inflow, and six potential water outlets in total were identified through three heavy rains. Meanwhile, a geophysical prospecting technique was also used to detect water sources. The connections between water outlets and water sources were identified with a 3-D graphic that included all of them. According to the distribution of water outlets and water sources, the detection area was divided into three sections and separately treated by curtain grouting.

Support Vector Machines(SVM)-Markov Chain Prediction Model of Mining Water Inflow

This study was conducted to establish a Support Vector Machines(SVM)-Markov Chain prediction model for prediction of mining water inflow. According to the raw data sequence, the Support Vector Machines(SVM) model was built, and then revised by means of a Markov state change probability matrix. Through dividing the state and analyzing absolute errors and relative errors and other indexes of the measured value and the fitted value of SVM, the prediction results were improved. Finally,the model was used to calculate relative errors. Through predicting and analyzing mining water inflow, the prediction results of the model were satisfactory. The results of this study enlarge the application scope of the Support Vector Machines(SVM) prediction model and provide a new method for scientific forecasting water inflow in coal mining.

Prediction of the maximum water inflow in Pingdingshan No.8 mine based on grey system theory

In order to prevent and control the water inflow of mines, this paper built a new initial GM（1, 1） model to torecast the maximum water inflow according to the principle of new information. The effect of the new initial GM（1, 1） model is not ideal by the concrete example. Then according to the principle of making the sum of the squares of the difference between the calculated sequences and the original sequences, an optimized GM（1, I） model was established. The result shows that this method is a new prediction method which can predict the maximum water inflow accurately. It not only conforms to the guide- line of prevention primarily, but also provides reference standards to managers on making prevention measures.

Grey forewarning and prediction for mine water inflowing catastrophe periods

Based on the theory of grey system, established GM （1, 1） grey catastrophe predict model for the first time in order to forecast the catastrophe periods of mine water inflowing （not the volume of water inflowing）. After establishing the grey predict system of the catastrophe regularity of 10 month-average volume of water inflowing, the grey forewarning for mine water inflowing catastrophe periods was established which was used to analyze water disaster in 400 meter level of Wennan Colliery. Based on residual analysis, it shows that the result of grey predict system is almost close to the actual value. And the scene actual result also shows the reliability of prediction. Both the theoretical analysis and the scene actual result indicate feasibility and reliability of the method of grey catastrophe predict system.

Key issues in water sealing performance of underground oil storage caverns: Advances and perspectives

Water sealing performance is important for underground water-sealed oil storage(UWSOS).The key issues concerning water sealing performance mainly include the permeability of fractured rock mass(FRM),water-sealed safety(WSS),water curtain performance,and prediction and control of water inflow.This paper reviews the progress of above four key issues on water sealing performances.First,the permeability of an FRM is the basis of water sealing performance,and several commonly used permeability test methods and spatial variation characteristics of permeability are outlined.Second,the current water sealing criteria are compared,and the evaluation methods of WSS are summarized.Third,the design parameters and efficiency evaluation of water curtain systems(WCSs)are introduced.The water inflow of oil storage caverns(OSCs)can reflect the water sealing effect,and the prediction methods and control measures of water inflow are also summarized.Finally,the advantages and disadvantages of the current research are discussed,and the potential research directions are pointed out,such as optimization of water sealing criteria and FRM model,quantitative evaluation of WCS efficiency,accurate prediction of water inflow,and improvement of grouting technology.

Influence of asymmetric blockage of the drainage system of a deep-buried tunnel on water gushing

Asymmetric blockage of drainage systems occasionally occurs,which seriously threatens the safety of tunnel operation.Based on theoretical analysis,a calculation expression of tunnel water inflow involving clogging parameters was derived.Degradation of the analytical solution was analysed with the Taylor equation and series expansion theorem,and a tunnel under construction was considered to conduct field tests to verify the rationality of the established model and correctness of the derived expression.Studies have demonstrated that with increasing drainage system blockage degree,the amount of water inflow in the nonblocked area slowly increases,and the total amount of water in the tunnel gradually decreases.The hydrodynamic pressure in the blocked area non-linearly decreased,and the water inrush velocity and hydraulic gradient in the non-blocked area gradually increased.When the drainage system was not blocked,the result of tunnel water inflow calculated by the formula derived in this paper was 8.3% higher than the measured value.When the drainage system was blocked,the theoretical water inflow was 10.5% higher than the measured value.The difference between the measured value and the theoretical value is small,which verifies the effectiveness of the calculation formula of water inflow deduced in this paper.

Assessment of Water Losses from Badovc Lake, Kosovo： Hydrochemical Implications

This paper aims to quantitatively assess water losses of Badovc Lake-Kosovo based on both water balance of the lake and water hydrochemistry. This attempt was strongly prompt by both the importance of this lake for water supply of Prishtina city and the lack of water. According to lake water balance, a water loss of 3,738,905 m^3 and 1,722,552 m^3 for the hydrologic year 2014 and the period January-May （2015） was evaluated. These consistent data favour the opinion that a continuous groundwater outflow from the lake is present and it is conditioned by the intensively developed fracture system in the lake basement formations. This was also supported by the chemical data （chloride, sulphate, hardness and electric conductivity etc.） of the water. Water from the leakages on the right side of the dam shows the same chemical signature as the water from the lake. Whereas, water from the piezometer, monitoring well and the gallery of Hajvalia mine show similar values with those of the water from the lake. The calculations of the chloride mass balance showed that the fractions of lake and rainfall waters in the water mixture of Hajvalia mine were 67% and 33% respectively.

隧道渗涌水量的随机模型预测

渗涌水问题是常见的隧道病害 ,是影响隧道正常使用 ,危及行车安全的重要因素。因此 ,科学地预测隧道涌水量大小 ,是制定最优防治水方案 ,确保安全通车的关键。笔者以大瑶山隧道渗涌水量的实测数据为基础 ,应用随机过程的理论和方法 ,建立了隧道渗涌水量的平稳序列预测模型 ,并将预测值与实测结果进行了对比 ,比较吻合。

黄石互通浅埋隧道涌水量预测分析

福建海西天然气二期管网工程黄石互通隧道主要位于缓丘地段,底板标高-15 m,埋深浅,通过分析评价其地层岩性、地质构造及水文地质特征,针对该浅埋隧道的特点,采用大气降水入渗法预测了隧道的涌水量,并用地下水动力学法进行验证计算,通过两种方法预测结果的相互验证,进而提出了隧道涌水量施工设计预测数据,且在工程实践中得到了验证,保证了隧道安全施工。

南水北调崇青隧洞施工涌水条件及涌水量研究

基于前期勘察成果、施工地质资料,对南水北调中线北京段崇青隧洞的工程地质条件进行了详细介绍,并对隧洞施工涌水地质条件进行了分析,在此基础上采用大井法和集水廊道法分别对隧洞涌水量进行计算,并与实测涌水量进行对比研究。结果表明:大井法估算涌水量为433 L/min,总体比实测值偏大;而集水廊道法估算涌水量为288 L/min,总体接近实测值;隧洞工程涌水量计算应有可靠的地质资料作为支撑,以避免计算失真,保证计算结果的可靠性。

巨厚充水含水层疏放水层位优化研究

东胜煤田纳林河矿区营盘壕煤矿煤层埋深大、含水层厚,以往均是将直接充水含水层直罗组含水层视为一完整的统一含水层。矿井在工作面回采前对上覆直罗组含水层进行疏水降压,疏放水量衰减较快、水压降幅大,但采空区涌水量依然较大,疏放水效果与采空区涌水量较大相矛盾。对直罗组含水层垂向岩性特征及富水性特征进行了分析,揭示出直罗组含水层之间存在泥岩及砂质泥岩互层,含水层间呈非连续状态;采用分层抽水试验及井下放水试验、含水层水文动态观测可知,直罗组含水层具有明显的分层性,上下端含水层水位有区别,不同层段含水层之间水力联系微弱,直罗组含水层并非一完整的统一含水层。研究结果可为巨厚砂岩深埋矿区优化疏放水层位、提高疏放水效果提供依据。

区域污染负荷特征与控制分析:以宁夏沿黄经济带为例

2017年以来宁夏13条主要入黄排水沟水质基本为劣Ⅴ类,迫切需要推进宁夏沿黄经济带污染防控,保障沿黄城市群高质量绿色发展乃至黄河流域生态安全。针对宁夏沿黄经济带现状污染分析中未考虑污染物入河过程中的减少和点面源污染总体分析不足的问题,以TN、TP、COD、氨氮为污染负荷指标,采用统计数据和考虑入河系数的输出系数法,分析区域污染负荷特征,诊断主要污染源,计算分析点面源污染物排放量和入河量,进行污染物入河量控制分析,提出污染防控的重点和策略。研究表明:2017年研究区TN、TP、COD、氨氮排放量分别为2.23万t、0.15万t、6.16万t、1.00万t,入河量分别为1.03万t、0.03万t、3.31万t、0.44万t,城镇生活污水、农田化肥污染、工业污染物入河量分别占入河总量的55.9%、26.6%和14.7%。污染防控主要策略是城镇污水处理厂出水水质提标至准Ⅳ类,可削减污染物至现状的60.8%;农田亩均化肥折纯量控制在15kg以下,可削减污染物入河量至现状的32%;宁东能源化工基地和工业园区实行近零排放。研究结果为宁夏沿黄经济带生态保护和污染防控治理提供技术支持。

Grouting techniques for the unfavorable geological conditions of Xiang'an subsea tunnel in China

One of the major challenges during subsea tunnel construction is to seal the potential water inflow. Thepaper presents a case study of Xiang＇an subsea tunnel in Xiamen, the first subsea tunnel in China. Duringits construction, different grades of weathered geomaterials were encountered, which was the challengingissue for this project. To deal with these unfavorable geological conditions, grouting was adoptedas an important measure for ground treatment. The grouting mechanism is first illustrated by introducinga typical grouting process. Then the site-specific grouting techniques employed in the Xiang＇ansubsea tunnel are elaborated. By using this ground reinforcement technique, the tunneling safety of theXiang＇an subsea tunnel was guaranteed. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Approximate analytical solution for seepage field of drained tunnel in vertically stratified phreatic aquifer

To explore the water table and water inflow after tunnel excavation in a vertically stratified phreatic aquifer,approximate analytical solutions for the steady-state water table and water inflow of a drained tunnel in a vertically stratified phreatic aquifer were obtained based on the Dupuit assumptions and the integral method.By comparing the approximate analytical solutions with numerical solutions,it was found that the relative error of the approximate analytical solution for the water table elevation is less than 10%,and the relative error of the approximate analytical solution for the water inflow is approximately 25%.The sources of the above errors are as follows:(1)At the lateral boundary of water replenishment,the water surface should be tangent to the horizontal line,but the water surface for the approximate analytical solutions has a gradient.(2)At the vertical boundaries near the tunnel,the total head is variable,but the total head for the approximate analytical solutions is assumed to be constant.(3)The Dupuit assumptions are applied in the flow domain near the tunnel.Although the relative errors of the approximate analytical solutions for the water table elevation and water inflow are evident,the lowered water table is reflected in the approximate analytical solutions.

安太堡露天矿芦子沟背斜区防排水方式选择

为了确保人员和设备的作业安全,提高设备的作业效率,确保正常的延深进度,结合矿坑的地质条件和现状、采排规划、涌水和降雨情况等,分析选择了合理的排水方式,为确保矿坑安全正常延深创造条件。

Variation of upper-ocean heat content in the Canada Basin in summers of 2003 and 2008

Conductivity, temperature, and depth data collected during the summers of 2003 and 2008 were used to study upper-ocean （top 200 m） heat content in the Canada Basin. The variation of heat content with depth, heat content differences between the summers, principal driving factors, and horizontal spatial scale differences were analyzed. A catastrophic reduction of sea ice cover in the Canada Basin was evident in 2008 by comparison with 2003, suggesting that more solar radiation was absorbed in the upper ocean during the summer of 2008. The sea ice reduction produced more freshwater in the upper ocean. Thus, seawater properties changed. The study shows that the huge reduction of sea ice would result in two changes-widespread warming of the upper ocean, and the depth of Pacific inflow water in the basin increased substantially. Near-surface temperature maximum （NSTM） water was also analyzed as an indicator of Arctic Ocean warming.

宁夏东部灵盐含煤区地层水量分析及疏降排协同技术研究

综合比对鸳鸯湖、马家滩、积家井矿区的水文地质条件,分析了红柳、双马、麦垛、金家渠矿区内顶板含水层特性,通过对侏罗系主要含水层之间的水力联系分析,说明延安组含水层与直罗组下段含水层之间水力联系密切,在回采过程中需重点控制。提出了工作面涌水量是由静态水量和动态水量构成,并确定静态水量、动态水量的评估方法。指出静态水量是工作面水害形成的直接原因,动态水量造成的水害不确定性极强,是工作面控制灾害的重点;通过采取束状钻孔、靶向疏水、群孔疏放水等技术有效降低工作面静态水量及水压,减小工作面水害威胁,依据对地下水动态补给量的理论分析,得出工作面最大涌水量是正常涌水量的1.38倍;针对不同含水层的富含水条件及含水层之间的水力联系、涌水量大小构建不同的排水系统,有效提高矿井抗灾能力。

长榆河煤业充水因素分析及涌水量预测

矿井涌水量是评价矿井水文地质条件复杂程度的重要指标,同时充水因素的确定对于水害防治措施的实施有着目标导向的作用,因此,分析充水因素和正确预测矿井涌水量对于指导矿井排水设施建设、消除水害威胁、保障煤矿安全生产具有重要意义。对长榆河煤业开采15#煤层、15下#煤层时的充水因素进行了分析,并选用大井法和富水系数比拟法对矿井涌水量进行了预测,最终结合实际,得出了矿井涌水量,为水害防治提供基础数据支撑。

Theoretical and experimental study on the rheological properties of WIS grout and the dispersion and sealing mechanism

Recently a new grout material called water inflow sealing(WIS) was invented for sealing water inflow in tunneling and underground constructions. In this study, a special experimental method called intubated counter grouting(ICG) was proposed to investigate the influence of water dispersion on the rheological properties of the grout during the grouting process, and to testify the sealing performance of the grout,such as instant gelling ability(IGA) and anti-dispersion ability(ADA). In the experiment, dispersion was restricted in the downstream of the channel with a high turbulence intensity. The influences of ADA and IGA were therefore decoupled and evaluated separately. Experimental results revealed two distinctive sealing mechanisms of WIS. For a low initial velocity of water, WIS turned the shear flow of water into an overall movement of a plug by absorbing water into the particles. For a high initial velocity and the situation that the particles reached the outlet before sufficiently expanding, WIS modified the rheology of the water in the channel and reduced its velocity till the static state. The distinctive feature of WIS brings a reformation on the sealing mechanism and provides an effective way to control water inflow with high pressure and velocity.