Stability behavior of the Lanxi ancient flood control levee after reinforcement with upside-down hanging wells and grouting curtain

The stability of the ancient flood control levees is mainly influenced by water level fluctuations, groundwater concentration and rainfalls. This paper takes the Lanxi ancient levee as a research object to study the evolution laws of its seepage, displacement and stability before and after reinforcement with the upside-down hanging wells and grouting curtain through numerical simulation methods combined with experiments and observations. The study results indicate that the filled soil is less affected by water level fluctuations and groundwater concentration after reinforcement. A high groundwater level is detrimental to the levee's long-term stability, and the drainage issues need to be fully considered. The deformation of the reinforced levee is effectively controlled since the fill deformation is mainly borne by the upside-down hanging wells. The safety factors of the levee before reinforcement vary significantly with the water level. The minimum value of the safety factors is 0.886 during the water level decreasing period, indicating a very high risk of the instability. While it reached 1.478 after reinforcement, the stability of the ancient levee is improved by a large margin.

Removal of Pb^(2+) and Cd^(2+) by adsorption on clay-solidified grouting curtain for waste landfills

Pb2+ and Cd2+ in leachate were adsorbed on clay-solidified grouting curtain for waste landfills with equilibrium experiment. The cation exchange capacity was determined with ammonium acetate. And the concentration of heavy metal cations in leachate was determined with atomic absorption spectrophotometer. Their equilibrium isotherms were measured, and the experimental isotherm data were analyzed by using Freundlich and Langmuir models. The results show that the adsorption capacities of the heavy metal cations are closely related to the compositions of clay-solidified grouting curtain, and the maximum adsorption appears at the ratio of cement to clay of 2∶4 in the experimental conditions. At their maximum adsorption and pH 5.0, the adsorption capacities of Pb 2+ and Cd 2+ are 16.19mg/g and 1.21mg/g. The competitive adsorption coefficients indicate that the adsorption of clay-solidified grouting curtain for Pb2+ is stronger than that for Cd 2+ . The adsorption process conforms to Freundlich’s model with related coefficient higher than 0.996.

Retention of clay-solidified grouting curtain to Cd^(2+), Pb^(2+) and Hg^(2+) in landfill of municipal solid waste

The effects of components and their ratio of grouts on anti-seepage capability of clay-solidified grouting curtain and its permeability of heavy metal cations were investigated by permeating experiments, using reactive solute transport model to study the permeation of heavy metals (Cd2+, Pb2+ and Hg2+). The study of permeating for different mixture ratios of cement and clay indicates that hydraulic conductivity of clay-solidified grouting curtain with different ratios of solid to liquid or with the same ratio of solid to liquid but with different ratios of cement to clay is changed. The laboratory simulation test results also show that precipitates produced in heavy metal cation migration process in curtain block up water flowing passage which makes the hydraulic conductivity of the solution-permeated curtain decrease with the leakage time. The permeation velocities for different heavy metal cations vary with ionic concentration, exchange capacity and ion radius etc. The test results indicate that the permeation rapidity order of heavy metals cations in clay-solidified grouting curtain is Hg2+>Pb2+ in the same experimental circumstance. In addition, permeability for different mixture ratios and antisepsis capabilities of clay-solidified grouting curtain were studied in tests.

Factors affecting phenol adsorption on clay-solidified grouting curtain

Batch experiments were conducted to study the adsorption of phenol on clay-solidified grouting curtain (CSGC) and the effects of contact time,pH and adsorbent concentration on the adsorption were investigated.Under the experimental conditions used,2 d was adequate to determine the equilibrium of phenol adsorption onto CSGC.The amount of phenol adsorbed by CSGC from an initial concentration of 100mg/L was found to be 8.4mg/g.The adsorption process includes particle diffusion and liquid film diffusion,and the latter is the predominating step of the adsorption process.The adsorption ability of CSGC decreased with pH but it increased non-linearly with the CSGC concentration.The optimized concentration for CSGC was found to be 20g/L for the adsorption of 100mg/L phenol.

Analysis on contaminants transport process through clay-solidified grouting curtain in MSW landfills

Clay-solidified grouting curtains are commonly used for remediation by containment or pollution prevention, in addition to their use as a barrier to water flow in municipal solid waste(MSW) landfills. A hydrological model.of water flow and a hydrodynamic model of contaminant are presented to simulate the migration of leachate through clay-solidified grouting curtain in MSW landfills, with particular attention paid to the role of diffusive and adsorptive fluxes in contaminant transport. The models were applied to simulate the sensitivity of the curtain's behavior to changes in parameters, such as thickness, depth, permeability coefficient, diffusion coefficient,resistance coefficient and concentration, and also to demonstrate the contaminant distribution on the evolution of travel time and offset distance of clay-solidified grouting curtain in landfills. It is found that a part of leachate components stays or is retarded in clay-solidified grouting curtain by precipitate or exchange, the retention rate is closely related to composition of clay-solidified grouting curtain, more than 800%, and the maximum occurs at the cementclay ratio of 2: 4 under experimental conditions. Contamination distribution is variable on travel time and offset distance, the highest concentration takes place where the contamination intensity is nearest to the pollution resource or takes place at early middle period of transport, and the pollutant attenuates gradually. The results indicate that claysolidified grouting curtain with a proper thickness, a low permeability coefficient and a high resistance coefficient might serve as a sufficiently effective vertical barrier against leachate seepage and contamination migration in MSWlandfills.

Real-Time Grouting Monitoring and Visualization Analysis System for Dam Foundation Curtain Grouting

A real-time monitoring and 3D visualization analysis system is proposed for dam foundation curtain grouting. Based on the real-time control technology, the optimization method and the set theory, a mathematical model of the system is established. The real-time collection and transmission technology of the grouting data provides a data foundation for the system. The real-time grouting monitoring and dynamic alarming method helps the system control the grouting quality during the grouting process, thus, the abnormalities of grouting, such as jacking and hydraulic uplift, can be effectively controlled. In addition, the 3D grouting visualization analysis technology is proposed to establish the grouting information model(GIM). The GIM provides a platform to visualize and analyze the grouting process and results. The system has been applied to a hydraulic project of China as a case study, and the application results indicate that the real-time grouting monitoring and 3D visualization analysis for the grouting process can help engineers control the grouting quality more efficiently.

Permeability in Flysch-Distribution Decrease with Depth and Grout Curtains Under Dams

A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation, their comparison and their decrease with depth is discussed. The depth where a permeability of 3 to 5×10-7m/sec can be retained (the limit of a reasonable grouting under a high dam) may be twofold if the geological history of the formation could not contain a compressional tectonic process. This depth may reach 100m in some cases. The differences in the mean values of permeability among the various litho-types are minor, while the presence of siltstones, always present although with varied participation, dramatically controls the global permeability.

贵州裸露型岩溶地下河系统污染防治技术——以遵义坪桥地下河系统污染防治工程为例

裸露型岩溶区岩溶强发育、水文地质条件复杂,受污染的地下河系统通道隐蔽性强、污染防治难度大。本文以坪桥地下河系统污染防治工程为例,在近污染源的主径流通道实施“地下水防渗帷幕+污水抽排”工程措施实现近源截排。施工面临岩溶破碎地层易掉块卡埋钻、钻效低及岩溶强发育段浆液扩散距离远等难题。通过配备适宜的钻进工艺,采取纯压式灌浆、水泥砂浆灌填溶洞、低压限量及速凝浆液灌注等灌浆控制措施,保证了工程进度质量,实现了源头治理污染地下水的目的。“近源截排”对类似水文地质条件下地下水污染防治提供可借鉴的地学治理模式。

基于流固耦合的高承压水岩溶隧道加固措施研究

我国西南地区多山岭且地下水丰富,公路隧道在修建过程中面临的水文地质条件复杂多变,国内外大量工程实践表明,隧道在穿越高承压水岩溶地质时,由于围岩岩溶发育、自稳能力差、岩溶水丰富且水压力较高等特点常易发生突泥、涌水甚至塌方等工程灾害,为此开展基于流固耦合的高承压水岩溶隧道加固措施研究,并以巫溪隧道为依托工程,通过对采用不同加固措施包括帷幕注浆、超前小导管及径向注浆系统锚杆的隧道施工进行数值模拟,对比分析不同加固措施的效果。结果表明:1)隧道仅施作初期支护时,高承压水岩溶隧道易发生整体失稳破坏;2)采用帷幕注浆加固措施后,围岩变形及塑性区得到有效控制;3)采用帷幕注浆+超前小导管+径向注浆系统锚杆控制围岩变形效果更加显著,可进一步为隧道提供安全储备;4)根据加固效果及经济成本控制,推荐方案为帷幕注浆+径向注浆系统锚杆。

地铁暗挖竖井深孔注浆止水施工技术研究

针对承压水粉细砂地层竖井施工发生流水涌砂及坍塌的难题,采用深孔注浆止水帷幕代替人工降水。通过对注浆帷幕的设计以及增加预防竖井侧壁滑塌的棚盖措施,有效阻隔了竖井开挖过程中的地下水,满足暗挖施工无水作业的条件。

柠条塔煤矿水文地质结构特征与水害治理模式研究

随着西部煤炭资源的持续高强度开采,矿山所面临的工程与水文地质条件越来越复杂,极易诱发采掘突水溃砂事故,而水文地质结构特征的研究是水害评价和治理的重要基础性工作。本文以陕北榆神府矿区的柠条塔煤矿为例,在对其地质条件和构造发育情况进行系统分析的基础上,从矿区的补给、径流、排泄条件,主要充水水源,矿体与含水层的空间结构关系三个方面对矿山的水文地质结构特征进行了研究。研究发现,地表浅部松散层主要接受大气降水补给,基岩风化带含水层主要接受侧向径流补给。矿井充水水源包括大气降水、地表水、含水层水、老空水和烧变岩水五种,不同煤层根据其埋深、开采厚度、冒裂带发育高度等的不同具有不同的充水水源。基于对矿山水文地质结构特征的分析,认为火烧区下部2-2煤层回采工作面可能存在突水溃砂风险,并设计了两排帷幕注浆孔。注浆治理工程完成后的放水试验结果表明,烧变岩含水层补给量大幅度减小,治理效果显著,可以保障煤层的安全开采,研究成果对榆神府矿区的矿井水害防治及水资源保护具有一定的理论意义和实践意义。

土石坝灌浆设计与施工关键技术探讨

心墙堆石坝和面板堆石坝等土石坝坝基灌浆受盖重薄、爆破卸荷、岩体软弱等因素影响,灌浆过程中抬动、劈裂和外漏严重,导致升压灌注和质量保证困难,甚至影响水库正常蓄水。针对建基岩体选择、基础灌浆廊道布置、灌浆孔布置、灌浆与检查压力等关键设计问题进行分析,并结合规范规定和工程实践对灌浆方法、外漏处理、阻塞器选择、抬动控制与升压方式等关键施工工艺和参数进行探讨,提出的帷幕灌浆压力与检查压力确定方法、外漏系统封堵+随机封堵、阻塞器选择原则、基于P与Q关系的“固步升压”灌浆控制等,可供同类工程坝基灌浆参考。

西南地区急倾斜薄煤层充水采空区地面注浆堵水工艺研究及应用

针对金沙水电站蓄水区南岸的相关煤矿采空区的治理,选择帷幕注浆堵水为治理方案。通过钻孔将水泥浆充填采空区及其上部裂隙,切断金沙江与矿井之间的径流通道,其中帷幕孔注浆采用水泥-水玻璃双液浆注浆工艺,一般注浆孔采用水泥浆单液注浆工艺。室内凝结时间检测试验的结果中,水泥浆的终凝时间随着水灰比的增大而逐渐从500 s以上下降到20 s左右,根据试验结果确定了合适的水泥浆配比。注浆堵水质量检测得到4组水泥芯体的采空区无侧限抗压强度均值分别为1.21、1.21、1.36、1.29 MPa,注浆段波速值为365~384m/s。抗压强度大于1 MPa,横波波速大于350 m/s,表明注浆堵水工艺实施后的质量评价结果整体满足要求,具有可行性与实用性。

岩溶地区某尾矿库尾砂渗漏探查与治理

某尾矿库位于岩溶地区,雨季库区出现塌陷,且下游溶洞口尾砂泄漏,造成当地水土体污染。经现场调查及库区水文地质条件初步分析,认为库区岩溶塌陷导通岩溶管道是尾砂泄漏的主要原因。采用EH4连续电导率剖面仪与五极纵轴测深相结合的综合物探方法,先进行EH4探测,再在EH4圈定的异常部位进行五极纵轴测深,发现在库区岩溶洼地中间发育一条北东向断层及其次生构造,且沿构造附近地表以下80m范围内有大量低阻区,推测为库区的主要过水通道。采用地面帷幕注浆方法,利用钻探查清了尾砂渗漏的主要岩溶通道;利用理论公式计算确定了骨料投入量,并采用“投骨料-注双液浆-注水泥单液浆”的动水注浆技术对大型溶洞或岩溶管道进行了有效封堵。经帷幕注浆治理后,库区内未再出现塌陷情况,下游也未见尾砂泄漏。实践表明,综合物探探测技术与地面帷幕注浆方法能有效解决尾砂渗漏通道探查与治理问题,可为今后类似尾矿库渗漏治理提供借鉴。

富水岩溶隧道注浆处理及工艺优化

为了提高隧道富水岩溶区的注浆加固效果,依托某隧道工程,采用多种超前探测手段对隧道富水岩溶区进行全面探测。在此基础上,采用数值模拟方法,分析不同注浆厚度下隧道位移变化和涌水的变化规律,并采用3种注浆技术相结合的方法对隧道富水岩溶区进行了注浆加固。研究结果表明:帷幕注浆厚度主要体现在减少涌水量上,当注浆厚度超过5 m以后,隧道的止水效果几乎不再增长;选择5 m的注浆厚度和25 m的注浆长度作为工程的注浆范围。在注浆过程中,3种注浆技术相结合,可以有效解决高水位涌动和成孔困难的问题。勘探和注浆结合的方法,可为后续注浆方案提供动态反馈和优化。注浆结束后,现场施工情况表明,注浆效果良好。

竖井地面预注浆帷幕安全厚度研究及其在隧道通风井中应用——以天山胜利隧道4号通风竖井为例

针对天山胜利隧道4号通风竖井穿越富水地层施工难、风险高的问题,采用地面预注浆技术构筑注浆帷幕。首先,考虑竖井开挖过程中的爆破扰动效应,将地面预注浆帷幕体安全厚度划分为无效厚度与有效厚度,并构建水平地层压力和孔隙水压共同作用下的注浆帷幕体力学分析模型。然后,基于弹塑性力学理论,分析有效注浆帷幕体的径向位移;同时,通过预测竖井开挖爆破后围岩粉碎区范围,确定注浆帷幕体的无效厚度。最后,运用厚壁圆筒理论,结合有效注浆帷幕体在弹塑性交界面处的位移协调条件,确定注浆帷幕体的有效厚度,并验算注浆帷幕体强度及稳定性。将上述理论应用到天山胜利隧道4号通风竖井,确定其注浆帷幕体安全厚度为6.5 m。现场监测结果表明,该厚度满足工程要求,堵水效果良好。

巴东组泥岩大断面隧道开挖面大变形滑塌失稳机制与防治措施研究

隧道穿越富水软弱地层时易发生开挖面滑塌失稳破坏,为此,本文以郑万高铁巴东隧道为工程依托、以巴东组紫红泥岩为研究对象,开展系列室内试验,揭示泥岩遇水软化的力学特征。综合考虑围岩节理发育及施工扰动等因素的影响,基于Hoek-Brown强度准则将室内试验获取的完整岩体的强度参数转化为现场岩体参数,并采用两相单质点流固耦合物质点法(MPM)对隧道开挖面滑塌失稳大变形全过程进行模拟,并结合现场评价超前帷幕注浆预加固措施的有效性。研究结果表明:开挖面滑塌失稳过程可大致分为开挖面隆起变形、开挖面局部失稳及滑塌体加速运动、滑塌体稳定这3个主要阶段。随着开挖面前方滑塌体的加速运动,围岩的渗流场发生明显的变化,渗水形态呈“漏斗状”,水流向开挖面“缺口”汇集;滑塌体稳定后呈锥体状堆积,滑塌体坡脚与开挖面的距离约25 m,与现场滑塌体最终形态较吻合。采取超前帷幕注浆预加固措施后围岩稳定性较好,确保了隧道施工安全顺利推进。流固耦合物质点法可动态再现地下水渗流作用下软弱地层隧道滑塌失稳破坏全过程,可为类似工程研究提供参考。

帷幕注浆封堵寒武系灰岩导水通道效果定量判识

注浆堵水是煤矿水害防治常用的技术手段之一,而注浆效果定量判识是注浆工程中的关键环节。以平顶山煤田七矿寒武灰岩导水通道帷幕注浆封堵工程为研究对象,遴选注浆量、单位时间注浆量、延米注浆量、终孔压力、终孔层位及岩石力学强度变化为帷幕注浆堵水效果评价的指标体系。采用层次分析法、熵权法、组合赋权法确定指标因子的主观、客观及综合权重,应用模糊可变集模型定量判识了帷幕注浆堵水效果并进行了排序。研究表明,通道治理效果的综合排名为:6号通道最佳,依次是3号、2号、1号、5号和4号通道,所有钻孔和通道的注浆效果均达到合格或以上,总体表现良好。导水通道注浆封堵后,由于七矿与五矿之间水力联系较为紧密,导致两矿的水文情况显著变化。七矿动水补给量和五矿排水量在枯水期合计减少435.74 m^(3)/h,在丰水期合计降低809.98 m^(3)/h,帷幕注浆堵水效果显著。

复杂富水地层地铁深大基坑渗漏治理技术研究

由于青岛地区濒临海岸线,地下水丰富,地铁深大基坑开挖遇到软硬复合地层、构造破碎带的复杂地层时,易发生地下水渗漏。依托青岛地铁7号线周村站基坑工程,基于工程调研、现场试验和现场监测,研究了穿越不良地质段深大基坑开挖渗漏特点,提出了CSM止水帷幕下坑外注浆+坑内注浆的系统注浆工艺。研究结果表明:构造破碎带是地下水的良好通道,基坑开挖侧壁易发生渗漏。分段注浆、地表与坑内注浆结合的注浆工艺可有效处理地下水大范围渗漏的问题,弥补CSM止水帷幕的工艺缺点。注浆全过程地表最大注浆量为410.5m^(3),桩体水平位移最大值为26.4mm,发生在断层破碎带与基坑围护桩相接的位置。基坑再次开挖,基坑侧壁无渗水点,实际注浆止水效果良好。

煤矿斜井过动水砂层帷幕注浆扩散封堵机理及应用

我国西部煤矿斜井井筒在富水松散层段大多发生渗漏水现象,有时甚至存在涌水溃砂风险,影响煤矿安全生产。为科学指导斜井过动水砂层防治水工作,以曹家滩煤矿主副斜井过动水砂层帷幕注浆为工程背景,借助有限元数值模拟软件建立了动水砂层帷幕注浆扩散封堵模型,探究了煤矿斜井过动水砂层帷幕注浆扩散封堵机理,结合具体治理区域,优化了动水砂层帷幕注浆参数及工艺,并进行了现场效果检验。研究结果表明:随着动水流速和注浆压力的增大,浆液顺水流方向扩散特征明显;注浆压力0.5MPa,动水流速0.3m/s时,顺水流方向浆液扩散半径增至1.83m;随着帷幕内壁与井筒外壁间距的增大,井筒围岩变形破坏范围逐渐远离井筒外壁,治理区域间距设置应不小于12.5m;注浆参数及工艺优化后,主副斜井治理段水量分别衰减85.6%和82.7%,治理效果显著。本文研究成果有助于解决动水砂层斜井井筒渗漏水问题,保障斜井井筒安全运营,保护矿山地下水资源。