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.

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.

Water inflow forecasting for tunnel considering nonlinear variation of permeability coefficient

To assess the water inflow which is more suitable to the actual conditions of tunnel,an empirical correlation about the permeability coefficient changing with depth is introduced.Supposing that the surrounding rock is heterogeneous isotropy,the formula for calculating water inflow of tunnel with the nonlinear variation of permeability coefficient is deduced.By the contrast analysis with the existing formulas,the presented method has the similar value to them;moreover,the presented method has more simple form and easy to use.Due to parameter analysis,the water inflow decreases after considering the nonlinear variation of permeability coefficient.When the attenuation coefficient a>0,the water inflow increases first till reaches the maximum at a certain depth,then decreases and is close to 0 finally if deep enough.Thus,it is better to keep away from the certain depth where it is with the maximum water inflow for safe operation and economical construction,and reduce the water damage.Based on the analysis,the radius of tunnel has less impact on the amount of water inflow,and the water inflow just increases by 6.7% when the radius of tunnel increases by 1 m.

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.

Application of Integrated Geological Prediction Technologies in Sub-river Tunnel of Liuyang

Because of the frequent serious geo-hazards met in constructing sub-river tunnels,the application of geological prediction is necessary to reduce the risk. Taking the Liuyang River Tunnel(10.1 km,with 362 m of the sub-river part) which is one of the key projects of the dedicated-passenger railway from Wuhan to Guangzhou as an example,the application of integrated geological prediction technologies is expounded in detail.The effects of TSP(tunnel seismic prediction) and infrared water detectors are analyzed as key points in order to summarize the advantages and disadvantages of these devices.The results of this research which can be adopted to improve the effects of the

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.

Predictive analysis of stress regime and possible squeezing deformation for super-long water conveyance tunnels in Pakistan

The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hock-Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey＇s model can subsequently be employed to predict the areas＇ stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai-Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH - Sh 〉 Sv or SH 〉Sv 〉 Sh. The measured orientation of Sn is NEE （N70.3°-89°E）, and the regional orientation of SH from WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stres- ses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.

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.

相空间重构后矿井涌水量序列地质学含义及其应用研究

目的为了确定相空间重构矿井涌水量序列的地质学含义并提高涌水量预测精度,方法以王行庄矿为例,在涌水量序列相空间重构后,对重构后相空间列向量与涌水量主控因素进行相关性分析,并在此基础上建立混沌理论与人工神经网络耦合(Chaos-ENN)的涌水量预测模型。结果结果表明:相空间的嵌入维数等于矿井涌水量主控因素个数;相空间的第1,2,4,5,6列向量分别与C_(2)tL_(7-8)含水层水位埋深、O_(2)m+Є_(3)ch含水层水位埋深、采空区面积、C_(2)tL_(1-4)含水层水位埋深、开拓长度具有较高的相关性,第3列与不易量化的其他综合因素有关;构建的Chaos-ENN涌水量预测模型在王兴庄矿的预测精度达到97.91%。结论涌水量序列重构后相空间的列向量具有明确的地质学含义。利用混沌理论可以量化涌水量预测模型中ENN输入层的个数及取值,所以仅需涌水量序列值就可以建立矿井涌水量预测的Chaos-ENN模型,该模型解决了涌水量预测中存在的主控因素难以确定和不易量化的难题,且预测精度高,具有较高的推广价值。

富水岩溶地区隧道涌水预测与施工处置技术研究

针对贵州某隧道施工过程中遭遇一处连通地下暗河的大型溶洞引起隧道内大规模涌水的灾害进行研究,结合水文地质情况对涌水量进行预测和分析后,现场先对岩溶水进行初步释压,后采用水泥砂浆分步回填隧道上伏溶腔以封堵岩溶出水口;进一步采用集水管引排岩溶水的方式对剩余地下水进行二次加强处理,同时将集水管与隧道外侧的泄水洞相连,二者构成一套完整的引排水系统的处治手段。采用堵排相结合的原则有效地达到涌水处置目的,确保了隧道的安全施工,可为类似地层的隧道施工提供有益的借鉴。

隧道富水断层破碎带突涌预报与工程对策研究

为解决高原隧道断层破碎带易发突泥冒顶灾害的问题,采用现场调查、地面物探、洞内地震波反射法、瞬变电磁法、超前钻孔等超前地质预报方法,推广洞内物探三维分析,对富水断层破碎带突泥灾害特征、超前地质预报综合成果和工程应对加固措施进行研究。结果表明:三维物探成果能快速精准查明富水破碎带空间形态,成果直观,有效指导风险判识和工程处置措施;对富水断层带预报应充分结合勘察期成果,宏观初判断层分布特性,洞内采用物钻结合、长短结合的方法;首次提出按照“探明破碎带规模形态,查明破碎带物质组分性状,观测地下水特征变化情况”的思路,研判突泥涌水风险;施工处置应按照“探泄结合,先固后进,回堵再泄”的总体原则有序开展。研究成果和手段可为类似突涌灾害超前地质预报和工程应对措施提供参考。

彬长大佛寺矿井涌水量时序预测

为提高矿井涌水量预测精度,解决矿井涌水量预测无法及时响应动态变化的问题,构建一种基于模态分解和深度学习的矿井涌水量多因素时间序列组合预测模型。使用变分模态分解和灰色关联分析筛选主控因素,通过双向长短期记忆网络和卷积长短期记忆网络对高、低频模态分量进行预测。结果表明:对比不同时序预测模型,变分模态分解可以有效捕捉时序数据中的长期依赖关系,提供了更加准确的长期时序数据预测能力;经过鲸鱼优化、贝叶斯优化算法对不同频率模态分量的处理,有效降低了高频部分的无序性、复杂性并优化了较为线性、缓慢的低频部分;验证了矿井涌水量时序预测中的变分模态深度学习组合模型的有效性和适用性,预测精度满足生产需求。该理论丰富了矿井涌水量时序预测方法,对煤矿水害预防具有一定的理论意义。

内蒙古母杜柴登煤矿3^(-1)煤充水条件及矿井涌水量预测

母杜柴登煤矿矿井涌水量大,且属于高矿化度水,面临着大量疏排矿井涌水和矿井水地面处理的压力。在分析矿区地质及水文地质条件的基础上,认为开采3^(-1)煤层时,矿井水来源于3^(-1)煤顶板─直罗组底界砂岩含水层,包括直罗组底部中、粗粒砂岩含水层和3^(-1)煤顶板延安组三段砂岩含水层。运用大井法和达西定律计算的30209工作面涌水量分别为931m^(3)/h、919m^(3)/h,与实际接近。研究可为工作面侧向注浆封堵(含水层改造)、帷幕截流减量的可行性和减量程度提供依据。

煤矿充水因素评价及涌水量预测

含水层、老窖水以及采空区积水等水源对煤矿安全生产带来威胁。以山西省某煤矿为例,分析充水因素,并对采用富水系数比拟法对涌水量进行预测,有利于煤矿防治水工作开展,对井下安全生产具有重要意义。

基于SSA-CG-Attention模型的多因素采煤工作面涌水量预测

矿井工作面涌水量预测对确保矿山安全、优化资源配置、提高工作效率等都具有重要作用。为提高预测结果的准确性和稳定性,基于钻孔水位和微震能量数据与涌水量的强关联性,选择其作为多因素特征变量,提出SSA-CG-Attention多因素矿井工作面涌水量预测模型。该模型在门控循环单元(GatedRecurrentUnit,GRU)提取时序特征的基础上,与卷积神经网络(ConvolutionalNeuralNet-work,CNN)融合形成新的网络结构提取数据的有效非线性局部特征,并且加入注意力机制(Atten-tion),在预测过程中将注意力集中在输入元素上,提高模型的准确性。最后通过麻雀搜索算法(Spar-row Search Algorithm,SSA)优化模型参数,避免局部最优解的问题。将提出的模型分别与传统的BP神经网络、LSTM、GRU单因素涌水量预测模型以及MLP、SLP、SVR、LSTM、GRU、SSA-LSTM、SSA-GRU多因素涌水量预测模型的预测结果进行对比分析,结果表明:SSA算法以最少迭代次数快速寻优,避免了局部最优解的缺陷;SSA-CG-Attention多因素涌水量预测模型整体预测指标绝对误差(E_(MA))、均方根误差(E_(RMS))以及平均绝对百分比误差(E_(MAP))分别为5.24 m^(3)/h、7.25 m^(3)/h、6%,指标方差和为8.90。相较于其他预测模型预测精度更高,相较于单因素涌水量预测模型,多因素涌水量预测模型预测结果更加稳定。研究结果为矿井工作面涌水量预测提供了新的思路与方法,对矿井工作面涌水量预测及防控有着借鉴与指导作用,具有一定的理论价值和现实意义。

基于CEEMDAN和改进的混合时间序列模型工作面涌水量预测研究

为提高采煤工作面涌水量预测准确度,收集大量工作面涌水量观测数据进行整理、统计、分析,将涌水量稳定性、周期性和季节性特征考虑在内,提出1种基于数据驱动的完全自适应模态分解算法(CEEMDAN)和改进的混合时间序列模型工作面涌水量预测方法。该方法利用CEEMDAN处理涌水量数据,构建麻雀搜索算法(SSA)优化的长短期记忆网络(LSTM)和自回归移动平均模型(ARIMA)并行级联而成的混合时间序列模型对工作面涌水量进行预测。研究结果表明:该模型预测结果与真实数据相差更小,平均绝对误差为6.36 m 3/h,均方根误差为10.6 m 3/h,模型拟合系数为0.95,更适用于工作面涌水量预测。研究结果可为矿井工作面涌水量预测及防控提供参考。

煤矿充水因素评价及涌水量预测

为真实掌握煤矿的涌水量和充水条件,在对煤矿水文地质分析的基础上,首先对充水条件和充水因素进行评价,得出煤矿的充水通道主要为导水裂隙带,基于层次分析得出通道条件的权重因子为0.2667最大,为该煤矿的充水的首要条件;在对煤矿历年涌水量观测结果分析的基础上,采用大井法对涌水量进行预测,综合分析最终得出该煤矿正常涌水量为462 m^(3)/h,最大涌水量为693 m^(3)/h。

隧道涌水量预测计算方法综述

预测隧道涌水量对于保障隧道施工安全、进度、洞室稳定和人身安全问题至关重要。国内外学者已提出多种预测方法,但是存在不同适用条件,根据隧道的水文地质条件选取恰当的方法能有效提高预测精度。对解析公式法、经验公式法、数值法、随机性数学模型预测法等多种涌水量预测方法进行了系统梳理和分析,通过对这些方法的基本原理及适用条件进行综合分析,讨论了当前涌水量预测方法存在的不足之处,并提出改进方向。结果表明:解析公式法应用简单,但结果偏差较大;经验公式法源于工程案例总结,适用于相似条件下隧道涌水量预测;数值法通过数学模型模拟,可以解决复杂水文地质条件下的涌水量预测,但对勘察设计阶段获取的水文地质参数提出更高的要求;随机性数学模型方法需要大量数据来保证结果的准确性;其他方法主要依赖于地理信息系统(GIS)技术、同位素分析法等手段,通过科学分析来识别并判断地下水量及其流动通道的地质特征,需要充分的数据支持和详尽的地下勘探结果作为依据。研究成果可为实际工程中选择合适的涌水量预测方法提供参考。

基于降雨量数据的程潮铁矿涌水量时序性预测模型

无底柱分段崩落法开采必然形成大范围的地表塌陷区,所分布的导水裂隙将导致大量的地表降水向下渗透,引起巷道涌水量骤增,程潮铁矿现已进入-500 m开采水平,大气降雨与崩落法开采所引发的裂隙持续动态发展之间的相互作用机制十分复杂。因此,为科学准确地预测井下涌水量,本研究提出了一种以降雨量为输入数据的涌水量灰色GM(1,2)时序性预测模型。以程潮铁矿2019—2021年的降雨量、涌水量实际数据为训练样本,充分考虑崩落法开采对上覆岩体的持续影响,引入时序性系数K对模型进行优化,最终建立的灰色GM(1,2)时序性预测模型与传统的GM(1,2)预测模型相比,预测精度平均提高了7.79%。运用该模型对2022年的涌水量进行预测检验结果表明,其旱、雨两季的预测精度分别为93.51%、93.58%,预测效果较好。研究成果是通过地表降雨量数据直接预测矿山井下涌水量数据的一种有效方法。