Stress evolution and support mechanism of a bolt anchored in a rock mass with a weak interlayer

By applying experimental method, the bolt stress and supporting mechanism is studied during the deformation process of a rock mass containing a weak interlayer. The force measuring bolt is installed manually and instrumented five pairs of symmetrical strain gauges. The experimental results show that the fully grouted bolt suffers tensile, compressive, bending and shear stress at the same time. The bolt stress evolution is closely related to the deformation stages of the rock mass which are very gradually varying stage, gradually varying stage at the pre-peak and suddenly varying stage at the post peak stage.The axial compressive stress in the bolt is mainly induced by the moment. Thus, in most cases the axial compressive stress is distributed on one side of the bolt. For axial stresses, induced by the axial force and the bending moment at the post-peak stage, three types of changing are observed, viz. increasingincreasing type, decreasing-increasing type and increasing-decreasing type. The stress characteristics of the bolt section in the weak interlayer are significantly different from those in the hard rock. The failure models of the anchored bolt are tensile failure and shear failure, respectively. The bolt not only provides constraints on the free surface of the rock mass, but also resists the axial and lateral loading by the bending moment. This study provides valuable guidelines for bolting support design and its safety assessment.

Bolt-grouting combined support technology in deep soft rock roadway

Analyzing the mineral composition, mechanical properties and ground stress testing in surrounding rock,the study investigated the failure mechanism of deep soft rock roadway with high stress. The boltgrouting combined support system was proposed to prevent such failures. By means of FLAC3D numerical simulation and similar material simulation, the feasibility of the support design and the effectiveness of support parameters were discussed. According to the monitoring the surface and deep displacement in surrounding rock as well as bolt axial load, this paper analyzed the deformation of surrounding rock and the stress condition of the support structure. The monitor results were used to optimize the proposed support scheme. The results of field monitors demonstrate that the bolt-grouting combined support technology could improve the surround rock strength and bearing capacity of support structure, which controlled the great deformation failure and rheological property effectively in deep soft rock roadway with high stress. As a result, the long term stability and safety are guaranteed.

Numerical simulation of creep characteristics of soft roadway with bolt-grouting support

Based on the engineering background of a soft rock roadway in Qinan Coal Mine 82 Area,Huaibei Mining Group,three creep models with different support patterns in soft rock roadway were established by using geotechnical software of FLAC2D.According to the calculation results of different models,the change law of mechanical properties with the time of bolt-grouting support structure was obtained.Furthermore,for the test bolt-grouting support roadway,the deformation law of surrounding rock got by underground industrial experiment and field observation accords with the creep law got by numerical calculation.The results of numerical calculation and field observation show that,compared with other supports,the creep of bolt-grouting support roadway enters the steady-state creep stage from tertiary creep stage ahead,the deformations of roof,floor and two sides are decreased greatly,the plastically deforming area in surrounding rock is reduced obviously,and the distribution ranges of maximum and minimum principal stress are shrank obviously.All those fully show that the bolt-grouting support has its remarkable advantages in controlling surrounding rock creep and improving the whole strength of surrounding rock and self-bearing capacity.

Plastic zone analysis and support optimization of shallow roadway with weakly cemented soft strata

Based on a shallow roadway with weakly cemented soft strata in western China, this paper studies the range and degree of plastic zones in soft strata roadways with weak cementation. Geological radars were used to monitor the loose range and level of surrounding rocks. A mechanical model of weakly cemented roadway was established, including granular material based on the measured results. The model was then used to determine the plastic zone radium. The predicted results agree well with measured results which provide valuable theoretical references for the analysis of surrounding rock stability and support reinforcing design of weakly cemented roadways. Finally, a combined supporting scheme of whole section bolting and grouting was proposed based on the original supporting scheme. It is proved that this support plan can effectively control the deformation and plastic zone expansion of the roadway surrounding rock and thus ensure the long-term stable and safe mining.

Support technologies for deep and complex roadways in underground coal mines:a review

Based on geological and mining characteristics,coal mine roadways under complex conditions were divided into five types,for each type the deformation and damage characteristics of rocks surrounding roadways were analyzed.The recent developments of roadway support technologies were introduced abroad,based on the experiences of supports for deep and complex roadways from Germany,the United States and Australia.The history and achievements of roadway support technologies in China were detailed,including rock bolting,steel supports,grouting reinforcement and combined supports.Four typical support and reinforcement case studies were analyzed,including a high stressed roadway 1,000 m below the surface,a roadway surrounded by severely weak and broken rocks,a chamber surrounded by weak and broken rocks,and a roadway with very soft and swelling rocks.Based on studies and practices in many years,rock bolting has become the mainstream roadway support form in China coal mines,and steel supports,grouting reinforcement and combined supports have also been applied at proper occasions,which have provided reliable technical measures for the safe and high effective construction and mining of underground coal mines.

破碎围岩巷道变形失稳特征及控制技术

针对破碎围岩巷道变形量大、围岩整体性差和支护困难等问题,以昌兴煤矿1460运输石门为试验地点,通过数值模拟与现场考察,研究原支护技术下巷道围岩变形失稳特征及机制,拟采用联合支护技术并对比分析围岩变形特征。研究表明:由于围岩强度低、支护方式单一、受开采动压影响和围岩中含软弱夹层,造成围岩松散破碎,稳定性差,顶板最大破坏深度达到4.80 m;提出了“锚网喷+U型棚拱形支架+注浆”联合支护技术,采用预应力锚索、高刚度U型钢棚、浅孔注浆及深孔锚注等支护方式强化围岩特性,形成多层复合加固拱承载结构,实现支护结构与围岩的相互耦合作用;数值模拟分析得出,修复后围岩塑性屈服区最大深度由5.56 m减小到1.07 m,降低了80.76%,围岩塑性区大幅度减小,围岩应力总体趋于均匀分布;现场试验表明,修复后顶底板位移量仅113 mm,两帮位移量78 mm,说明该联合支护技术方案可有效控制围岩变形失稳,维持巷道整体稳定。

深部巷道大断面交叉点联合支护技术研究

针对深部大断面巷道支护易发生失稳的难题,以唐山矿-1100中央轨道山下车场大断面交叉点为工程背景,开展工程地质调查及巷道变形情况分析,提出锚喷+锚注联合支护方案,并运用FLAC3D数值模拟分析支护方案改进前、后巷道变形情况。结果表明,常规锚网喷支护下大断面巷道顶板下沉和帮部位移量较大,巷道不能实现自稳;锚喷+锚注联合支护下巷道变形量大幅降低,巷道基本实现自稳。将该方案应用于工程实践,锚喷+锚注联合支护技术能够有效控制深部大断面巷道变形,顶板下沉量较原支护降低了78.8%,帮部位移量降低了54.8%,为同类工程背景提供可靠的技术参考。

构造应力影响下巷道支护技术研究

针对下峪口煤矿2-2采区辅助运输巷受高水平构造应力影响难维护的状况,对巷道原支护和不同角度下施加的水平构造应力进行了数值模拟,分析了巷道失稳原因以及变形特征,提出了巷道支护的对策,确定了高强稳定性锚杆索联合支护方式,并对现场锚杆、锚索受力和巷道围岩位移进行了监测分析,实践表明巷道围岩变形得到了有效控制。

特大断面导流隧洞施工技术在水利枢纽工程中的应用

该文以某水利枢纽工程为例,探究特大断面导流隧洞施工中爆破开挖与锚喷挂网联合支护技术的应用。经前期地质勘察可知,隧洞围岩为Ⅱ~Ⅲ级,围岩稳定性较好,采取先进行光面爆破再进行洞身开挖的作业方案。在清运碴石、清除危石后,在开挖面上初喷混凝土形成稳定工作面。然后打入锚杆、挂钢筋网并进行二次衬砌,对导流隧洞支护,营造安全的施工环境。拱顶沉降监测数据表明,在导流隧洞开挖后的30 d内,每日平均沉降速率为2.09 mm,在允许范围之内,本次特大断面导流隧洞施工效果符合预期。

巷道中锚网索联合支护方案的应用分析

锚网索联合支护作为1种新型支护技术,具有支撑力度大、可防止巷道变形等优点,被广泛应用于煤矿巷道支护中。首先介绍了锚网索联合支护技术的基本原理和适用范围;然后,针对具体工程情况,在巷道形态、围岩情况和上覆厚度等因素影响下设计了1套支护方案,并进行了实践;最后,对施工过程和支护效果展开了详细分析,针对存在的问题提出了解决措施。

豫西“三软”煤层软岩巷道锚注支护技术应用

针对白坪煤矿13111上底抽软岩巷道底鼓、顶板破碎、围岩变形量大等问题,采用水理性试验和电镜扫描的方法对巷道围岩变形特征进行分析,得出巷道底板和帮部泥岩层中伊蒙混层含量较大,岩层遇水容易发生膨胀和泥化现象,导致巷道围岩产生破坏变形,据此建立数值模型,给出3种支护方案,并进行数值模拟分析,得出采用“锚网+喷浆+锚索+锚注”支护方式控制巷道围岩变形效果最好。应用效果表明,巷道在采用新设计的支护方案后,巷道两帮移近量最大为95 mm,顶底板移近量最大为118 mm。巷道围岩变形能够得到有效控制,达到预期效果。

煤柱回收工作面巷道围岩控制技术

为提高煤炭资源回收率、减少煤炭资源的损失浪费、延长煤矿的生产服务年限,南庄公司采取了大巷煤柱回收技术实践,通过高强度高预紧力锚杆支护技术实现了对破碎巷道的有效支护,围岩层次注浆技术实现了对巷道围岩的整体性加固,以上两项技术的应用使得煤柱工作面巷道得到有效控制,保障了煤柱的安全回采。

回风巷过断层破碎带围岩控制技术研究

为解决伊田煤业21510回风巷过断层破碎带可能发生的片帮、冒顶和巷道涌水等问题,分析巷道掘进地质条件,采用FLAC3D软件对巷道正常掘进和过断层期间垂直应力分布和塑性区发育进行数值模拟。结果显示,与正常区段相比,过断层掘进期间围岩应力和塑性区发育范围均明显增加,断层活化,掘进破坏影响范围扩大。采用循环注浆和“锚网索梁联合支护”方法进行围岩稳定性综合控制,并对控制效果进行观测,观测期内巷道左、右帮最大位移分别为7.22 mm和10.68 mm,顶底板移近量最大为21.9 mm,围岩控制效果良好。

煤柱下方巷道变形失稳规律分析及控制

为解决煤柱下方回采巷道在实际开采中变形严重以及围岩破坏的问题,在对现场条件及支护现状分析的基础上,对当前支护状态下回采巷道的失稳特征进行综合;提出了对回采巷道补强加固支护的方案,并对方案进行详细设计;最后,通过实践生产验证了补强加固卸压方案应用后对围岩的控制效果。

高应力软岩巷道注浆及锚喷支护的研究

通过分析湘永矿区煤系地层力学性质与围岩裂隙发育深度,在对原有锚网喷支护主要材料技术参数进行优化的基础上,提出“注浆+锚网喷”、“锚索+锚网喷”支护新理念,并通过工程试验,确定“注浆+锚网喷”支护为湘永矿区高应力软岩巷道首选支护形式。“注浆+锚网喷”支护在湘永矿区实施后,矿井巷道支护质量有了根本性提高,为高应力软岩巷道锚网喷支护的优化提供了可资借鉴的经验。

采动影响巷道支护方案设计及效果

为减少松软煤层围岩巷道受采动影响的破坏,提高煤层开采的安全性,以某矿为对象,分析该矿松软煤层在采动影响下围岩的变化规律,设计巷道联合支护技术为“锚网喷+锚索梁+注浆”。与无支护技术相比,经联合支护优化后,该矿巷道顶底板及两帮变形量分别降低68.5%、50%、61%,降幅明显,表明该联合支护技术能有效控制围岩变形,支护效果好。

浅谈微型钢管桩与锚杆联合支护技术的应用

微型钢管桩与锚杆联合支护技术是一种在高层建筑地下室施工中广泛应用的基坑支护手段。本文通过对该技术在施工中的应用特点进行分析,总结其在工程施工领域应用的现状,提出了加强该技术应用的有效策略,并通过案例分析,验证微型钢管桩与锚杆联合支护技术在不同工程中的可行性与优越性,进一步探索该技术的优化应用与推广,以满足不同工程需求,为高层建筑施工提供更加可靠、经济、实用的支护解决方案。

三软厚煤层锚杆索联合支护技术实践

三软煤层的围岩强度较低,巷道围岩变形较大,易导致安全隐患。为解决三软厚煤层的巷道失稳难题,以魏家地煤矿东1100回风顺槽为研究对象,采用理论分析法对巷道支护参数进行计算分析,并结合数值模拟及现场实测结果对三软煤层巷道围岩变形及控制展开研究,提出了针对性的锚杆索联合支护的设计方案。研究结果表明,三软厚煤层巷道不稳定围岩范围较大,锚杆支护范围无法有效控制围岩结构,需采用锚杆索联合支护方案。数值模拟及现场应用结果显示,锚杆索联合支护方案控制巷道围岩变形效果明显,围岩变形及巷道稳定性能够满足安全生产的要求。

厚煤层小煤柱护巷耦合支护技术的优化与应用

长平矿原采用25~30m大尺寸煤柱护巷,为提高煤炭资源回收率,以4309工作面小煤柱沿空掘巷为工程背景,综合运用理论分析与工程类比等方法,确定小煤柱最佳尺寸为6m。沿空巷道采用综掘工艺,浅掘进、轻扰动的掘进方式,配合邻近巷道爆破切顶卸压工艺,选用锚网索耦合支护方式,及时对裸露围岩进行喷浆封闭,滞后注浆加固,有效提高煤柱抗压强度。现场矿压监测表明,巷道变形均在可控范围内,满足4309工作面安全生产需求。

基于“加固拱”理论对煤巷支护技术的研究

针对余吾煤业大断面煤巷支护困难的问题,以N3102工作面运输顺槽为工程背景,在加固拱理论的基础上,采用锚网索联合支护,形成较大范围的“双重组合加固拱”,结合现场地质情况,确定支护方案,选择合理的支护参数。实践表明:支护效果良好,达到了预期的支护目标,显著地提高了支护强度,能够满足矿井安全生产的需求,可为该矿其他类似巷道的支护提供借鉴。