A Comprehensive Study on Subsidence Control Using COSFLOW

Increasingly, mine subsidence is becoming a major issue of community concern. Among the measures of subsidence control, a more effective and economical technology, namely Overburden Grout Injection Technology (OGIT), is recently developed in China and Australia by injecting waste material into the bed separations during longwall mining to achieve subsidence control. The OGIT is proposed for the subsidence control in West Cliff Colliery located at the Southern Coalfield of the Sydney Basin, Australia. The three-dimensional finite element code COSFLOW is applied to investigate in a detail the bed separation developing with longwall mining and the effect of grout injecting into the separations in order to guide the subsidence control design when using the OGIT in West Cliff Colliery longwall mining practice.     

Study on the Development Laws of Bed-Separation Under the Hard-Thick Magmatic Rock and its Fracture Disaster-Causing Mechanism

Based on the analysis of dynamic phenomena under the condition of high-located hard-thick (HLHT) stratum of one coal mine, along with the similar material simulation and theoretical analysis, the characteristics of bed separation development and cracks distribution under the HLHT stratum are studied. This paper proposes a discriminating method for overlying strata Three Zones considering the influence of HLHT stratum. The development laws of cracks and disaster-causing mechanism of hard-thick magmatic rock in different strata are respectively analyzed. The studies show that in line with the working face advancing direction, the height of bed separation under the magmatic rock increases in the trend of “Increase–Stability–Decrease”, and the width of bed separation increases linearly. The width of bed separation reaches the maximum before the first breaking of magmatic rock, the bed separation completely closes after the breaking. There are no obvious bed separations during the period migration of magmatic rock. Along the direction of the height of roof, the development of bed separation is characterized by bottom-up jump based on the key strata. The analyzed results of “Three zone” height obtained by the discriminate method of overlying strata Three Zones which is based on the key strata theory and the S–R instability theory are in line with the actual facts. When the hard-thick magmatic rock is in the fractured zone, large amounts of gas and water are easy to accumulate in the bed separation space and “O” ring space around the gob. The first breaking of magmatic rock may induce bed separation gas outburst and water inrush. When the hard-thick magmatic rock is in the sagging zone, the long-term stability of magmatic rock will not cause serious disasters. But with the adjacent working face mining, bed separation gas and water often become a safety hazard.     

我国煤矿离层涌突水致灾机理及其防控关键技术研究进展

离层水害严重影响煤矿安全,明确其突水致灾机理及防控技术的研究现状对促进煤矿安全生产具有重要作用。本文系统地总结论述了离层动态发育机制、突水致灾机理和突水预测预控技术3个方面的研究进展。离层随工作面推进过程呈现动态发育的特征,当某一层位离层具备密闭可持续的离层空间、补水通道、稳定的补给水源、突水通道这4个条件后即存在突水致灾的可能。进而,当离层存在上位高强度岩层破断产生的强冲击、离层积水产生的静水压、采场持续性回采活动的强扰动3个动力源中的一个(及以上)时,离层即发生涌突水。对离层水害的治理可从预防和预控两个角度入手,预防手段包括基于实用矿山压力理论、关键层理论构建离层发育层位预判模型及通过调整工作面推进速度和采高、运用绿色开采技术等减缓覆岩的运移和沉降,预控手段包括超前疏放水、钻孔截流、地面排水等。最后,指出了当前离层水害的研究过程中亟待攻克的难题,如积水探测技术不够精准、超前疏放水技术体系不够完善等,并展望了光纤探测技术、“地面+井下”抽疏(截)联动预控方法、一种无损采矿方法等防治离层水害的新方向。     

Tracing the interaction of acid mine drainage with coal utilization byproducts in a grouted mine: Strontium isotope study of the inactive Omega Coal Mine,West Virginia (USA)

In order to ameliorate acidic discharge, the inactive Omega Coal Mine, West Virginia was partially filled by injection of a grout consisting of 98% coal utilization byproducts (CUB), including fluidized bed combustion ash and fly ash, and 2% Portland cement. In this study, discharge chemistry and Sr isotope ratios were determined to identify and quantify the extent of interaction between mine waters and the CUB–cement grout. Eight sampling sites were monitored around the downdip perimeter of the mine. The major and trace element chemistry of the discharges was generally not sufficient to distinguish between discharges that interacted with grout and those that did not. Elements that showed the most separation include K and As, which were elevated in some waters that interacted with CUB–cement grout. In contrast, the Sr isotope ratios clearly distinguished discharges from grouted and non-grouted areas. Discharges that bypassed the grouted portions had ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.71510 to 0.71594, while two discharges that interacted with grout had ratios in the range of 0.71401–0.71456. The Treatment Inlet, which includes both grouted and ungrouted discharges, yielded intermediate isotopic ratios. Leaching experiments on CUB–cement grout, coal and surrounding rocks are consistent with the isotopic trends observed in the discharges. Based on these results, waters that interacted with grout received 30–40% of their Sr from the CUB–cement grout material. These results suggest that the grout material is chemically eroding at a rate of approximately 0.04% per year. This novel application of the Sr isotope system illustrates its ability to sensitively track and quantify fluid interaction with coal and CUB-based grout.     

Assessment of Relationship Between Grouted Values and Calculated Values in the Bazoft Dam Site

Seepage through foundation and abutments of a dam can potentially result in a waste of the water stored in dam reservoir, erosion of foundation materials, and development of uplift pressure in dam foundation which, consequently, threatens the long-term stability of the dam. In this study, the grout volume is estimated based on parameters such as joint aperture, the maximum penetration length of the grout, and calculated grout take in Bazoft dam site. Bazoft Dam is a hydroelectric supply and double-curvature arch dam with a height of 211 m located in Chaharmahal and Bakhtiari Province of Iran. The bedrock of Bazoft dam site consists of Asemari Formation (limy marl and marly lime), in the middle and upper parts of left abutment, and Jahrom Formation (limestone and dolomite) in the right abutment, river bed, and lower part of left abutment. The joint apertures were calculated based on the permeability and the joint spacing. Next, the maximum penetration length of the grout and grout volume were calculated. Using a statistical analysis, the relationship of the joint aperture, maximum penetration length, and the calculated grout volume with real grout take was also investigated. The results show that the grout take can be predicted with appropriate accuracy based on the calculated grout volume.     

顶板离层水突涌模式及预防技术模拟研究

为预防顶板离层水突涌产生的安全事故,提出了部分充填方案进行模拟研究。首先通过现有资料总结分析全国发生的多种离层水害事故,深入研究离层积水致灾模式;然后以陕西某矿首采区1307工作面的离层水害事故为例,分析其水文地质条件、上部含水层和离层水突涌的关系,利用3DEC数值软件模拟工作面顶板离层空间发育特征;最后根据该矿的实际情况,提出部分充填开采方式预防离层水突涌的技术措施,并对该矿的部分充填方案进行优化模拟研究。研究结果表明:根据发生条件的不同将离层水突涌划分为5种模式,离层积水过程分为初始积水期、积水至满期和裂隙扩展期;在保持充填率不变的情况下,随着走向采宽和充填宽度的同时同量增加,充填体对上覆岩层支撑作用逐渐增强,离层下部隔水层出现两侧应力增大现象,最佳部分充填方案为采宽80 m,充填宽度80 m,为顶板离层水害的预防提供新的思路。      

Grout injection into bed separation to control surface subsidence during longwall mining under villages: case study of Liudian coal mine,China

Surface subsidence can cause many environmental problems and hazards (including loss of land area and damage to buildings), and such hazards are particularly serious in coal mining districts. Injecting grout into the bed separation in the overburden has been proposed as an effective control measure against surface subsidence during longwall mining. However, no field trials of this technique have been implemented in mines under villages in China, and thus, its ability to control subsidence in such areas has yet to be demonstrated. In this study, field trials using this technique were carried out during longwall mining under villages in the Liudian coal mine, China. The maximum surface subsidence observed after the extraction was only 0.298 m, which accounts for 10 % of the mining height and is 79 % less than the predicted subsidence. Moreover, no damage occurred to the village buildings either during or after extraction and these buildings remain stable. Thus, this study represents the first successful attempt to control surface subsidence under villages in China using grout injection during longwall mining.     

岩体离层对锚固体荷载影响的弹塑性分析

巷道围岩由于变形不协调而产生离层,离层对锚杆产生附加应力。在已有弹性分析的基础上,根据岩层相对移动时拉拔载荷对锚杆的作用机制,建立了离层进一步扩展、锚固体界面进入弹塑性阶段的锚杆受力模型。通过选取二阶段线性函数剪切滑移模型,确定了离层左右两侧的滑移范围,并得出锚固体的应力分布形式。总结出离层作用下锚固体的受力过程一般分为4个阶段：弹性阶段、单侧进入弹塑性阶段、离层两侧均进入弹塑性阶段和一侧全部滑移、另一侧滑移范围增大阶段。通过对不同离层值和离层位置的参数分析得出：在相同离层位置条件下,离层值越大,离层对锚杆产生的附加应力就越大;在相同离层值条件下,弹塑性阶段基本趋势和弹性阶段相同,表现为锚杆中心处应力最小,越靠近边缘离层产生的附加应力越大。     

考虑时变性影响的盾构壁后注浆浆液固结及消散机制研究

在盾构管片壁后注浆时,由于浆液渗透压的存在,浆液会向外渗透,浆体本身逐渐固结,作用在管片上的注浆压力逐渐消散。考虑到浆液往周边地层渗透过程中由于黏度的变化会引起地层渗透系数的变化,推导了基于浆液黏度时变性的浆体固结变形方程和浆液压力消散方程,分析了浆液固结、消散及浆液压力沿管片外壁分布规律,为精细化分析施工阶段管片受力提供了计算依据。计算结果表明：浆液从注浆口喷出后,浆液黏性的增大使浆液流动性减小,注浆压力消散幅度减小,浆液消散持续时间变短。浆液配比与围岩渗透系数变化对注浆压力消散幅度及消散持续时间存在一定影响。现场实测结果与理论计算结果较为一致。在进行壁后注浆时,应充分考虑时变作用下浆液消散作用的影响。     

裂隙动水注浆渗流压力与注浆堵水效果的相关分析

采用裂隙动水注浆设备结合正交试验设计进行了裂隙动水注浆模型试验,获得了渗流压力场与注浆效果和注浆工艺之间的相关关系。结果表明,裂隙动水注浆的渗流压力场包括单峰型、平台型、多峰型、阶梯型4种类型;出现平台型和多峰型渗流压力场时的注浆堵水效果好,而出现阶梯型渗流压力场时的注浆堵水效果差;为了获得好的注浆效果且节约浆液,在渗流压力场为单峰型时应该适量增加注浆量;而在渗流压力场为平台型或多峰型时应该适量减小注浆量;渗流压力场为阶梯型时应该调节浆液配比,缩短凝胶时间。研究结果对应用压力监测及时控制施工质量和调整注浆工艺有指导作用。     

深水注浆锚设计原理及其承载特性试验研究

海洋能源开发不断向深海迈进,大型深水海上平台对锚泊结构的承载力提出了更高的要求。针对传统鱼雷锚承载比不足的问题,提出了一种新型深水注浆锚。锚体带动连接其尾部的注浆管贯入海床,然后在外部注浆设备驱动下向海床注浆,浆液挤压土体并在锚体周围形成注浆固结块,从而大幅增加锚体抗拔力。采用自主设计的海洋锚注浆和拉拔试验系统进行了模型试验,研究了不同注浆量对浆液扩散特性以及锚体承载特性的影响规律。结果表明：浆液可以较好地包裹锚体,浆块呈倒锥形与锚体紧密黏结为一体,共同承受上部荷载,浆块承载比可达 24.6,远高于传统鱼雷锚的 2.4～4.1,从而验证了深水注浆锚的可行性。随注浆量的增加,浆块端部截面积和整体高度增加,注浆锚整体承载力也不断增大。     

An investigation of the effects of important grouting and rock parameters on the grouting process

Today, grouting is used as an aid in ground improvement in most civil and mining engineering projects. Groutability and grout penetration depth are among the most important issues that are considered in grouting operation. Various parameters such as in-situ stress, pore water pressure, joint geometric and geomechanical characteristics, grout properties (viscosity and yield stress) and technical factors such as grouting pressure and flow rate affect the groutability and grout penetration depth in a jointed rock mass. Knowledge of the effect of these parameters has advantages in the prediction of grouting results. Typically, cement-based grout is used in jointed rock masses. Unlike water, stable cement-based grout usually acts as a Bingham fluid. In this study the effect of important parameters on grouting process in a jointed rock mass was investigated numerically using the DEM method. In the conducted study, the problem geometry represents a horizontal section in a regularly jointed rock mass with two joint sets. The analyses results show that the grout penetration depth and intake increase as joint aperture, normal stiffness and grouting pressure increase and in-situ stress and pore water pressure decrease. Increase in joint spacing does not have any effect on the grout penetration depth but decreases the grout intake. The effect of joint orientation on grouting process is strongly dependent on in-situ stress state. On the other hand, increase in grout yield stress decreases the grout penetration depth and intake, while grout viscosity does not have any effect on maximum grout penetration depth and intake. To further investigate the above mechanisms, the grouting process conducted in Gotvand dam-Iran was simulated numerically.     

正循环机械回转钻孔灌注桩在卵石层中的应用

在粒径、密实度较大的卵石层采用正循环机械回转钻进行灌注桩施工,存在钻具类型、合理的泥浆比例和钻探工艺等问题。以西安绕城高速公路谢王立交桥桥桩基工程实践为例,探讨正循环机械回转钻孔灌注桩在卵石层施工工艺等问题。     

单/多离层作用下锚杆受力特性分析

巷道围岩由于变形的不协调常常会产生单个或多个离层。根据岩层相对移动时拉拔载荷对锚杆的作用机制,对单个离层产生的锚杆附加应力建立弹塑性力学模型,讨论了弹性状态下离层对锚固体荷载的影响,随着离层进一步扩展,锚固体界面进入弹塑性阶段,基于剪切滑移模型,确定出离层左右两侧的滑移范围。总结出离层作用下锚杆受力全过程分为5个阶段：全弹性、单侧弹塑性、两侧弹塑性、一侧全滑移而另一侧滑移范围增大、全塑性直至锚杆承受极限拉拔荷载而破坏。采用模型试验数据对岩体离层-锚杆轴力曲线特性进行对比验证,结果表明,计算值与实测值吻合较好。根据应力叠加原理,推导出多离层情况下锚杆的应力求解公式,得出应力分布为多峰曲线。通过实例对离层值、离层位置做了参数分析,离层对锚杆的荷载影响应在今后的锚固设计中予以考虑。     

掺复合浆液堆石料压缩特性试验研究

针对高堆石坝坝体变形大且持续时间长的问题,提出了一种提高堆石体压缩模量、减缓流变变形的方法,即利用易流动、后期硬化的高掺粉煤灰水泥砂浆（简称复合浆液）在堆石体摊铺过程中充填堆石体孔隙,在施工碾压的基础上进一步减小堆石体孔隙率。首先,通过观测复合浆液在透明玻璃球中的流动性态,研究不同配比与掺量对复合浆液流动特性的影响;然后,通过侧限压缩和流变试验,研究掺复合浆液堆石料的压缩模量、流变变形的变化规律。试验结果表明：复合浆液在颗粒体孔隙中的流动性能与粉煤灰掺比、水胶比、砂粒最大粒径以及掺量有关;复合浆液的掺入能有效提高堆石料压缩模量,减少流变变形,且对于软岩料、级配不良料效果更为明显;复合浆液在堆石料中主要起到了充填、胶结与润滑作用。     

基于黏度时变性的桩端压力浆液上返高度模型及工程应用

桩端后压浆浆液上返高度对后压浆桩承载力的计算影响较大。基于幂律型流体的黏度时变性特征,推导了考虑黏度时变性的桩端压力浆液上返的理论计算公式,并给出了参数的确定方法及成层土中浆液上返高度的迭代算法;结合台州湾大桥的接线工程,利用电磁波CT对桩基后压浆的加固效果进行了探测分析。结果表明,采用浆液沿压浆管道阻力损失的拟合值并考虑黏度时变性得到的浆液上返高度的计算结果与实测结果基本吻合且偏于安全,而忽略黏度时变性得到的计算结果偏大,会对后压浆桩的承载力设计造成不利影响。此外,电磁波CT能观测到桩体、水泥浆加固体及土体的分布情况,且能推测出水泥浆液在桩端的扩散范围和沿桩身的上返高度,可用于评价后压浆桩的压浆效果。研究成果可为后压浆桩的设计和效果检测提供参考和指导。     

煤岩单组分分离及其影响因素

采用密度分离技术成功地对3个系列不同煤化程度的19个煤层煤样进行了单组分分离。通过实验认为,煤岩单组分在煤中的赋存特征和煤的煤化程度是影响单组分分离效果的主要因素      

铁路岩溶路基注浆材料试验研究

探讨了水泥、水玻璃及固化剂对粘土固化浆液性能的影响,提出了粘土固化浆液的最佳配比,通过试验分析了浆液在注浆过程中的扩散规律及防渗堵水效果。     

覆岩离层形成的力学判据研究

采区上覆岩层离层注浆是控制开采沉陷的重要技术,离层的形成和位置判别对正确实施离层注浆具有重要意义。分析认为,可注浆离层的产生需满足3个条件：弱面剪切破坏、岩层完整性和岩层组的岩性差异性条件。利用这3个条件和莫尔-库仑破坏准则,建立了完整的采区上覆岩层离层形成的力学判据。结合采区上方应力计算的解析解或数值方法可以准确地、方便地确定离层是否产生及产生位置。     

油页岩原位开采区注浆封闭浆液优化及其防渗效果实验

为提高油页岩原位转化加热效率、减少油气污染,采用注浆技术对油页岩开采区进行封闭止水。基于扶余油页岩开采区地质条件,对优化封闭浆液配方与封闭效果进行实验研究。首先基于正交试验,获得了不同指标下的优化配方,进而通过综合分析法,选出符合此封闭区要求的优化配方;为了验证优化浆液的封闭效果,对比分析了浆液充填前后油页岩试样渗透率的变化。结果表明：浆液优化配方为水灰质量比0.85,w（钠基膨润土）4.0%、w（微硅粉）6.0%、w（聚羧酸减水剂）0.5%;当围压为扶余油页岩开采区地应力时,充填浆液试样的渗透率均约为0.1×10^-3 μm²,远低于未充填的试样,优化浆液封堵试样裂缝效果较好。