Instability mechanism of mining roadway passing through fault at different angles in kilometre-deep mine and control measures of roof cutting and NPR cables

The angle α between the fault strike and the axial direction of the roadway produces different damage characteristics. In this paper, the research methodology includes theoretical analyses, numerical simulations and field experiments in the context of the Daqiang coal mine located in Shenyang, China. The stability control countermeasure of "pre-splitting cutting roof + NPR anchor cable"(PSCR-NPR) is simultaneously proposed. According to the different deformation characteristics of the roadway, the faults are innovatively classified into three types, with α of type I being 0°-30°, α of type II being 30°-60°, and α of type III being 60°-90°. The full-cycle stress evolution paths during mining roadway traverses across different types of faults are investigated by numerical simulation. Different pinch angles α lead to high stress concentration areas at different locations in the surrounding rock. The non-uniform stress field formed in the shallow surrounding rock is an important reason for the instability of the roadway. The pre-cracked cut top shifted the high stress region to the deep rock mass and formed a low stress region in the shallow rock mass. The high prestressing NPR anchor cable transforms the non-uniform stress field of the shallow surrounding rock into a uniform stress field. PSCR-NPR is applied in the fault-through roadway of Daqiang mine. The low stress area of the surrounding rock was enlarged by 3-7 times, and the cumulative convergence was reduced by 45%-50%. It provides a reference for the stability control of the deep fault-through mining roadway.

Triaxial mechanical properties and precursors of instability damage in rocks with different laminar dip angles

To investigate the mechanical failure characteristics of volcanic breccia with different bedding dip angles in deep layers,triaxial compression experiments were conducted on specimens taken from volcanic rock layers in the Junggar Basin,Xinjiang.By changing the confining pressure,we compared the mechanical properties,acoustic emission characteristics,and fractal features of the acoustic emission sequence for volcanic breccia with different bedding dip angles.The research results indicate that as the bedding dip angle increases,peak strength,internal friction angle,and cohesion exhibit a“U-shaped”variation pattern.The correlation dimension of the acoustic emission amplitude was calculated using the G-P algorithm,revealing that volcanic breccia exhibits fractal characteristics.Furthermore,a positive correlation between the correlation dimension and the bedding dip angle was observed.When the stress of the test specimen reaches 0.8σ_(c),there is a significant decrease in the fractal dimension,serving as a criterion for predicting the failure of the specimen.By analyzing the changes in fractal dimension at different stress levels,the slope of the fractal dimension△D<-0.5 can be used as a precursor to failure for test specimens with a bedding dip angle of 15°≤β≤45°.Similarly,when the bedding dip angle of the specimen is 0°≤β<15°or 45°<β≤90°,△D<0 can be considered as a precursor to specimen failure.This study provides theoretical references for understanding the failure patterns of volcanic rock.

Failure mechanism and safety control technology of a composite strata roadway in deep and soft rock masses:a case study

The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.

深埋软岩巷道高预应力恒阻耦合支护技术及其应用

针对深埋软岩巷道揭煤段掘进过程中围岩变形控制的问题,以石垭口煤矿1790回风石门为背景开展研究。首先,依据现场工程地质调查与实测结果分析了巷道揭煤段变形破坏特征;其次,采用理论分析与数值模拟等综合研究手段,揭示了深埋软岩巷道揭煤段大变形破坏机理;第三,基于开挖补偿力学效应和NPR(negative Poisson's ratio)长、短锚索耦合控制机理,提出了以NPR长、短锚索为核心的高预应力恒阻耦合控制技术;最后,通过数值模拟的手段验证了该方案的合理性。研究结果表明:巷道存在围岩变形严重、支护结构破断失效和巷道维护成本高等特征;巷道失稳破坏的根源在于围岩强度低且破碎严重、原支护结构不耦合以及支护强度不足;本文提出全断面“NPR长、短锚索+底角注浆锚杆+反底拱”的控制方案与参数。现场工业性试验中,NPR支护段较普通支护段围岩变形减小300~500 mm,NPR锚索受力最终稳定为340 kN左右。高预应力恒阻耦合支护方案可有效控制深埋软岩巷道揭煤段围岩大变形,为揭煤段围岩安全稳定控制提供了新支护手段。

深部泵房吸水井硐室群稳定性控制对策及应用

为解决深部泵房硐室群失稳现象突出的问题,以大强煤矿-890水平泵房吸水井硐室群为工程背景,通过理论分析和数值模拟,分析硐室群的破坏原因,对比集约化设计和传统设计对围岩稳定性控制的效果.基于恒阻大变形(NPR)锚索高恒阻、高延伸率和吸能的特性,建立NPR锚索支护下硐室交岔口围岩能量失稳判据,提出以高预应力NPR锚索+立体桁架为核心的泵房吸水井集约化控制对策,并进行现场应用.结果表明:相比传统设计,集约化设计简化了硐室布局和施工程序,同时能够减小巷道位移、应力,使塑性区范围减小并趋于均匀化,消除了空间效应;通过NPR锚索的高恒阻大变形和在桁架与围岩间预留的间隙释放围岩变形能,通过NPR锚索的高预应力和立体桁架的强度限制围岩变形,能有效保证巷道稳定;现场应用表明,该对策将围岩变形控制在70 mm以内,应用效果良好,可为类似工程提供参考.

一种机器视觉距离补偿路面破损位置定位方法

实时准确的路面破损自动检测技术对于公路管理养护有重要的意义。结合基于FPGA的路面破损识别检测系统进行定位精度的研究。由于该系统设备安装视角和载体运动速度等因素的影响,会造成路面定位精度的下降。提出了一种机器视觉距离补偿的路面破损定位算法,实验结果表明,当车的行驶速度在72 km/h以下时,定位误差从5 m减少到2 m,满足了系统设计的要求。

一种实时在线的公路路面破损及位置检测装置

提出一种实时在线的公路路面破损及位置检测装置,该装置采用图像处理识别技术判定采集的路面图像是否存在破损,应用北斗导航系统进行破损定位,并通过移动通信系统实现破损图片和位置信息的实时传输,整个装置采用FPGA加以实现。在路面破损识别中,改进了Sobel算法,进一步提高了检测的准确性和抗干扰能力。以裂缝识别为例,将裂缝分为横向、纵向、块状和龟裂四类,该装置在车速70 km/h下,识别准确性可达到88.75%。此外,整个系统管理后台显示破损图片、破损类型、位置和地图标注等信息。

基于改进西原模型的不同含水率砂岩蠕变实验及理论研究

为研究深部巷道围岩在地下水作用下的长时强度变化对围岩稳定性的影响,以万福煤矿深部巷道围岩为主要研究对象,对不同含水率状态下的砂岩样品进行单轴压缩实验及单轴蠕变实验。发现含水率对岩石强度及蠕变长时强度存在明显的软化效应;根据等时蠕变曲线黏弹性应变规律,提出黏性模量E_(v),获得其与弹性模量均随含水率的增加呈非线性软化的规律;此外,基于一种新的能够描述加速蠕变行为的黏壶元件,结合实验结果运用损伤理论提出改进的西原模型。运用该模型对蠕变实验结果进行参数辨识并与实验曲线进行对比分析,获得较好的结果,表明此模型能够较好地描述蠕变各阶段的力学行为;同时发现损伤蠕变模型参数E_(0)′,E_(1)′,η_(1)′在相同应力条件下差距不大,且各参数受蠕变应力σ影响存在一定规律,E0′与σ成线性关系,E_(1)′,η_(1)′与σ成负指数关系。因此可以根据现场含水率及不同应力水平对岩石所处蠕变状态进行合理分析,结合新的蠕变长时强度判别方法,对巷道长期稳定使用及巷道蠕变破坏的提前预报提供依据,具有重要的现实意义。

基于核磁共振监测的砂岩强度软化实验及微观机制研究

随着煤炭开采向深部不断发展,岩石所处地质条件愈发复杂,地下水作用使得围岩强度明显降低,严重影响现场人员及生产安全。为研究巷道开挖后水岩相互作用对围岩性质的影响,以万福煤矿深部巷道砂岩为研究对象,通过X射线衍射(XRD)、扫描电镜(SEM)、压汞(MIP)及核磁共振实验(NMR),对砂岩样品矿物成分、孔隙尺寸及微观结构进行监测,研究孔隙结构随含水率的动态变化规律。结合关键含水率(0%,0.8%,1.6%,2.4%,3.3%)的室内力学实验结果,探讨砂岩强度软化机制。研究表明:(1)本次砂岩核磁共振T2谱曲线呈现单峰特征,随着含水率增加,总谱面积不断增加,峰值对应弛豫时间不断右移。根据实验过程中谱面积占比出现稳定阶段及相互转化阶段,将传统吸水三阶段过程进一步分为急速吸水、均匀吸水、孔隙转化及稳定吸水4个阶段,其中,孔隙转化过程主要发生在第Ⅲ阶段(31~113 h);(2)砂岩强度随含水率增加呈非线性衰减,衰减程度受围压影响,随围压增大强度软化程度越低,其中,单轴抗压强度软化系数为0.372;(3)实验过程中黏土矿物的膨胀及石英骨架的约束是小孔闭合的原因,而石英颗粒的错动、孔隙水的流动及可溶性矿物的溶解,会导致吸水过程中孔隙变大;(4)对不同吸水阶段的软化机制进行探讨,除了结合水膜的润滑作用、黏土矿物胶结能力下降外,孔隙的扩张、连通也是导致砂岩软化的重要原因,且影响砂岩最终的破坏形态。