Theory,technology and application of grouted bolting in soft rock roadways of deep coal mines

The grouted bolt,combining rock bolting with grouting techniques,provides an effective solution for controlling the surrounding rock in deep soft rock and fractured roadways.It has been extensively applied in numerous deep mining areas characterized by soft rock roadways,where it has demonstrated remarkable control results.This article systematically explores the evolution of grouted bolting,covering its theoretical foundations,design methods,materials,construction processes,monitoring measures,and methods for assessing its effectiveness.The overview encompassed several key elements,delving into anchoring theory and grouting reinforcement theory.The new principle of high pretensioned high-pressure splitting grouted bolting collaborative active control is introduced.A fresh method for dynamic information design is also highlighted.The discussion touches on both conventional grouting rock bolts and cable bolts,as well as innovative grouted rock bolts and cables characterized by their high pretension,strength,and sealing hole pressure.An examination of the merits and demerits of standard inorganic and organic grouting materials versus the new inorganic–organic composite materials,including their specific application conditions,was conducted.Additionally,the article presents various methods and instruments to assess the support effect of grouting rock bolts,cable bolts,and grouting reinforcement.Furthermore,it provides a foundation for understanding the factors influencing decisions on grouted bolting timing,the sequence of grouting,the pressure applied,the volume of grout used,and the strategic arrangement of grouted rock bolts and cable bolts.The application of the high pretensioned high-pressure splitting grouted bolting collaborative control technology in a typical kilometer-deep soft rock mine in China—the soft coal seam and soft rock roadway in the Kouzidong coal mine,Huainan coal mining area,was introduced.Finally,the existing problems in grouted bolting control technology for deep soft rock roadways are analyzed,and the future development trend of grouted bolting control technology is anticipated.

Surrounding Rock Control Technology of Strong Dynamic Pressure Roadway in Hudi Coal Industry

Aiming at the problems of large deformation and difficult maintenance of deep soft rock roadway under the influence of high ground stress and strong dynamic pressure, taking the surrounding rock control of 1105 lane in Hudi Coal Industry as an example, the deformation characteristics and surrounding rock control measures of deep soft rock roadway are analyzed and discussed by means of geological data analysis, roadway deformation monitoring, rock crack drilling and field test. The results show that the main causes of roadway deformation are high ground stress, synclinal tectonic stress, advance mining stress, roadway penetration and surrounding rock fissure development. Based on the deformation characteristics and mechanism of lane 1105, the supporting countermeasures of “roof synergic support, layered grouting, anchor cable beam support, closed hardening of roadway surface” are proposed, which can provide reference for the control of deep roadway surrounding rock under similar conditions.

Deformation characteristics and damage ontologies of soft and hard composite rock masses under impact loading

As one of the most common occurring geological landforms in deep rock formations, the dynamic mechanical properties of layered composite rock bodies under impact loading have been widely studied by scholars. To study the dynamic properties of soft and hard composite rocks with different thickness ratios, this paper utilizes cement, quartz sand and gypsum powder to construct soft and hard composite rock specimens and utilizes a combination of indoor tests, numerical calculations, and theoretical analyses to investigate the mechanical properties of soft and hard composite rock bodies. The test results reveal that:(1) When the proportion of hard rock increases from 20% to 50%, the strength of the combined rock body increases by 69.14 MPa and 87 MPa when the hard rock face and soft rock face are loaded, respectively;however, when the proportion of hard rock is the same, the compressive strength of the hard rock face impact is 9%-17% greater than that of the soft rock face impact;(2) When a specimen of soft and hard combined rock body is subjected to impact loading, the damage mode involves mixed tension and shear damage, and the cracks generally first appear at the ends of the specimen, then develop on the laminar surface from the impact surface, and finally end in the overall damage of the soft rock part. The development rate and the total number of cracks in the same specimen when the hard rock face is impacted are significantly greater than those when the soft rock face is impacted;(3) By introducing Weibull’s statistical strength theory to establish the damage variables of soft-hard combined rock bodies, combined with the DP strength criterion, the damage model and the Kelvin body are concatenated to obtain a statistical damage constitutive model, which can better fit the full stress-strain curve of soft-hard combined rock body specimens under a single impact load.

Influence of dynamic pressure on deep underground soft rock roadway support and its application

Due to high ground stress and mining disturbance, the deformation and failure of deep soft rock roadway is serious, and invalidation of the anchor net-anchor cable supporting structure occurs. The failure characteristics of roadways revealed with the help of the ground pressure monitoring. Theoretical analysis was adopted to analyze the influence of mining disturbance on stress distribution in surrounding rock,and the change of stress was also calculated. Considering the change of stress in surrounding rock of bottom extraction roadway, the displacement, plastic zone and distribution law of principal stress difference under different support schemes were studied by means of FLAC3D. The supporting scheme of U-shaped steel was proposed for bottom extraction roadway that underwent mining disturbance. We carried out a similarity model test to verify the effect of support in dynamic pressure. Monitoring results demonstrated the change rules of deformation and stress of surrounding rock in different supporting schemes. The supporting scheme of U-shaped steel had an effective control on deformation of surrounding rock. The scheme was successfully applied in underground engineering practice, and achieved good technical and economic benefits.

Failure analysis and control technology of intersections of large‑scale variable cross‑section roadways in deep soft rock

In deep underground mining,achieving stable support for roadways along with long service life is critical and the complex geological environment at such depths frequently presents a major challenge.Owing to the coupling action of multiple factors such as deep high stress,adjacent faults,cross-layer design,weak lithology,broken surrounding rock,variable cross-sections,wide sections up to 9.9 m,and clusters of nearby chambers,there was severe deformation and breakdown in the No.10 intersection of the roadway of large-scale variable cross-section at the−760 m level in a coal mine.As there are insufcient examples in engineering methods pertaining to the geological environment described above,the numerical calculation model was oversimplifed and support theory underdeveloped;therefore,it is imperative to develop an efective support system for the stability and sustenance of deep roadways.In this study,a quantitative analysis of the geological environment of the roadway through feld observations,borehole-scoping,and ground stress testing is carried out to establish the FLAC 3D variable cross-section crossing roadway model.This model is combined with the strain softening constitutive(surrounding rock)and Mohr–Coulomb constitutive(other deep rock formations)models to construct a compression arch mechanical model for deep soft rock,based on the quadratic parabolic Mohr criterion.An integrated control technology of bolting and grouting that is mainly composed of a high-strength hollow grouting cable bolt equipped with modifed cement grouting materials and a high-elongation cable bolt is developed by analyzing the strengthening properties of the surrounding rock before and after bolting,based on the Heok-Brown criterion.As a result of on-site practice,the following conclusions are drawn:(1)The plastic zone of the roof of the cross roadway is approximately 6 m deep in this environment,the tectonic stress is nearly 30 MPa,and the surrounding rock is severely fractured.(2)The deformation of the roadway progressively increases from small to large cross-sections,almost doubling at the largest cross-section.The plastic zone is concentrated at the top plate and shoulder and decreases progressively from the two sides to the bottom corner.The range of stress concentration at the sides of the intersection roadway close to the passageway is wider and higher.(3)The 7 m-thick reinforced compression arch constructed under the strengthening support scheme has a bearing capacity enhanced by 1.8 to 2.3 times and increase in thickness of the bearing structure by 1.76 times as compared to the original scheme.(4)The increase in the mechanical parameters c andφof the surrounding rock after anchoring causes a signifcant increase inσt;the pulling force of the cable bolt beneath the new grouting material is more than twice that of ordinary cement grout,and according to the test,the supporting stress feld shows that the 7.24 m surrounding rock is compacted and strengthened in addition to providing a strong foundation for the bolt(cable).On-site monitoring shows that the 60-days convergence is less than 30 mm,indicating that the stability control of the roadway is successful.

Numerical simulation study of the failure evolution process and failure mode of surrounding rock in deep soft rock roadways

Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured zone in the roadway.This will provide the basis numerical simulation to calculate the surrounding rock fractured zone in a roadway.Using the single factor and multi-factor orthogonal test method,the evolution law of roadway surrounding rock displacements,plastic zone and stress distribution under different conditions is studied.It reveals the roadway surrounding rock burst evolution process,and obtains five kinds of failure modes in deep soft rock roadway.Using the fuzzy mathematics clustering analysis method,the deep soft surrounding rock failure model in Zhujixi mine can be classified and patterns recognized.Compared to the identification results and the results detected by geological radar of surrounding rock loose circle,the reliability of the results of the pattern recognition is verified and lays the foundations for the support design of deep soft rock roadways.

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.

Response models of weakly consolidated soft rock roadway under different interior pressures considering dilatancy effect

Surrounding rocks of weakly consolidated soft rock roadway show obvious strain softening and dilatancy effects after excavation. A damage coefficient concerning modulus attenuation was defined. Response models of stress and displacement of surrounding rock of soft rock roadway and analytical expressions to calculate plastic zones under different interior pressures and non-uniform original rock stresses were derived based on damage theories and a triple linear elastic-plastic strain softening model. Influence laws of dilatancy gradient on damage development, distributions of stresses and displacement in plastic region were analyzed. Interior pressure conditions to develop plastic region under different origin rock stresses were established and their influences on plastic region distribution were also discussed. The results show that the order of maximum principle stress is exchanged between ~0 and trr with the increase of interior pressure P0, which causes distributions of plastic zone and stress shift. Dilatancy effect which has great influences on the damage propagation and displacements in plastic region has little effect on the size of plastic region and stress responses. The conclusions provide a theoretical basis for a reasonable evaluation of stability and effective supporting of weakly consolidated soft rock roadway.

Study of dynamic pressure roadway supporting scheme under condi- tion of thick composite roof

This paper analyzed the strata behaviors of solid-coal roadway, gob-side entry driving and deformation law of surrounding rock in depth under high stress and thick composite roof based on the dynamic pressure roadway as engineering background in Fengcheng mining area, Jiangxi province. The results, both field measurement and numerical simulation show that gob-side entry driving results the deformation of coal roadway main wall, however, entity-coal roadway driving results deformation of main roof and floor. The maintenance state of gob-side entry driving is better than entity-coal roadway, this situation is relevant to thick composite roof layered and easy collapse characteristics. At the same time, this paper put fox＇ward and proved proper dynamic pressure roadway supporting scheme under the surrounding rock condition and stress environment.

特厚煤层大巷变形破坏特征及控制技术研究

针对特厚煤层大巷变形破坏特征分析及控制技术难题,以砚北煤矿二水平回风大巷为研究背景,在分析巷道围岩地质力学测试及围岩变形破坏特征与机理的基础上,提出了全断面注浆加固与高预应力支护综合围岩控制技术,制定了煤层大巷修复加固具体实施方案,并确定了相应的技术参数,开展了井下工业试验,试验结果表明:修复加固后35 d左右巷道变形趋于稳定,两帮最大位移量63.5 mm,顶底板最大移近量79.8 mm;注浆后水泥浆液与巷帮煤体裂隙及破碎区充分胶结,围岩裂隙明显减少,钻孔成型效果显著提高。研究表明采用高预应力锚杆支护及全断面注浆加固后,在巷道围岩内形成锚注加固体,提高了巷道围岩稳定性与抗变形能力以及浅部锚杆(索)锚固基础力学性能,巷道围岩变形得到有效控制。

深部极松软围岩沿空巷道稳定性控制及应用

针对深部高应力作用下极松软围岩变形量大、破碎程度高、巷道难支护等问题,以丁集煤矿1232(3)沿空巷道为工程背景,采用数值模拟、现场监测和井下试验相结合的方法,对深部高应力极松软围岩沿空巷道破坏特征及阶段性控制原理和技术进行研究。结果表明:随着距巷道迎头距离的不断增大,巷道两帮应力的不对称性逐渐增大,实体煤侧应力峰值为37.18 MPa大于煤柱侧35.21 MPa,1242(3)终采线50 m范围内存在应力集中,最大达33 MPa,巷道围岩塑性区发育程度为煤柱帮大于实体煤帮大于顶底板;从巷道掘进过程中所经历的复杂围岩变化过程,将全巷道划分为5种典型的围岩变化阶段来分析围岩变形破坏特征和破坏机理,揭示了在高应力作用下深部软岩沿空巷道围岩变形量大,在空间上呈现出明显的区域性和非对称性的特征;基于巷道初步设计方案和围岩变形破坏特征,及时有效的调整支护方案,对巷道进行分段式、非对称、区域化综合治理,形成深部软岩巷道围岩控制长效机制,为同类型深部软岩巷道地压治理提供了理论和技术支撑。

采动应力作用巷道交岔点稳定性分析及支护优化

深部软岩巷道交岔点稳定性控制是地下开采的难题,采区内巷道交岔点受采动应力作用更易发生变形破坏。针对该问题,依托805工作面下伏西二回风巷道交岔点工程背景进行研究,建立考虑工作面采动集中应力影响的巷道交岔点垂直应力计算式,采用数值计算方法分析不同采动应力集中系数、不同交岔角度下交岔点围岩应力及塑性区分布规律。得知随着采动应力集中系数增大,交岔点岩柱应力集中现象加剧、围岩塑性区发育范围增大、交岔点变形破坏加剧。基于上述分析,提出以全长预应力锚杆+锚索+围岩注浆的综合化主动支护方法。结合矿压监测,优化后支护效果良好。研究结果为类似采动应力影响下的巷道交岔点围岩稳定性控制提供技术参考。

新上海一号煤矿软岩回采巷道预裂卸压技术研究

基于新上海一号煤矿软岩巷道支护薄弱的特点,提出了一种新的预裂卸压技术,旨在解决软岩巷道围岩大变形控制难题。该技术主要采用超前预裂卸压为主、NPR锚索协同支护为辅的方式,通过预裂卸压切断采空区顶板与巷道顶板之间的联系,加速顶板垮断,减小悬臂长度及传递至临空巷道顶板的覆岩荷载。同时,采用NPR锚索提前对巷道进行补强加固,确保了沿空巷道在超前应力影响下的稳定性。实地应用表明,采用预裂卸压技术回采巷道围岩变形量得到有效控制,验证了预裂卸压技术的有效性。为软岩巷道稳定性控制提供了一种新的解决方案。

动压影响孤岛工作面巷道围岩“卸-支平衡”协同控制技术

煤矿深部工作面回采过程中,经常受到强开采动压作用影响,矿压显现强烈,巷道围岩变形破坏程度大,尤其对于孤岛工作面,动压影响更加显著,围岩控制难度成倍增加。为了解决深部孤岛工作面强动压影响回采巷道围岩控制问题,以2308工作面为研究背景,采用理论分析、数值模拟、现场验证等方法,首先对巷道围岩结构模型进行分析,确定影响工作面围岩稳定的主要因素;进一步对煤柱宽度和钻孔卸压2种方案进行研究,并根据巷道围岩的实际变形情况,确定巷道围岩的非对称支护参数,实现受强动压影响回采巷道的“卸-支平衡”协同控制方案。经过现场实践验证,2308工作面巷道顶底板移近量为260 mm,两帮移近量为471 mm,巷道围岩的整体性得到增强,变形得到有效控制;采用“卸-支平衡”方案对受动压影响巷道围岩的控制效果显著。

强采动巷道断顶卸压稳定性控制机理及应用

为解决强采动条件下巷道大变形难题,以新上海一号矿1806N工作面辅运顺槽为工程背景,采用实地勘探、理论分析、数值模拟的方法分析强采动巷道变形破坏原因及围岩大变形机理,提出相应的控制对策进行现场工业性试验。研究发现:1806N工作面辅运顺槽大变形主要影响因素为岩石强度低、节理裂隙发育、完整性差、顶板富水严重、围岩遇水泥化,强采动高集中应力。基于围岩大变形断顶控制机理,形成辅运顺槽深部爆破定向预裂断顶结合补强加固的设计方案。借助数值模拟对断顶及未断顶巷道应力变化规律进行对比分析,断顶巷道端头最大垂直应力14.6 MPa,断顶后巷道端头最大垂直应力12.5 MPa,断顶后端头处垂直应力减小14%,断顶具有一定切断应力传递及减小巷道收缩的效果。开展现场工业性试验,断顶后端头顶底板位移减小37%,两帮变形减小19%,底臌发育长度减小92%,结果表明断顶可有效减少端头巷道变形以及超前底臌发育长度和高度,可为相似工程地质条件巷道建设提供参考。

软岩大巷围岩裂隙演化机制与控制研究

本文以南岭煤业52采区进风大巷为研究对象,剖析了软岩大巷变形破坏特点及裂隙演化机制,以期有效解决软岩大巷面临的剧烈变形、失稳等工程难题。首先,根据软弱岩体应力-应变关系,及其与围岩强度变化之间的相互作用关系,构建了能够描述圆形巷道破坏分区现象的力学模型,明晰了软岩大巷围岩弹塑性变形分区破坏特征,揭示了深井软岩大巷围岩的变形破坏机理。其次,基于UDEC-Trigon方法,构建了符合工程尺度的离散元数值计算模型,并提出了针对该模型的参数校正方法。通过模拟研究,探讨了软岩大巷围岩的裂隙扩展特征、应力分布规律、巷道变形规律。最后,提出了深浅部注浆与高强高预紧力锚杆索支护的软岩大巷控制技术及相应参数,并在南岭煤业52采区进风大巷成功应用。应用结果表明:锚杆索+注浆联合控制技术有效控制了52采区进风大巷的变形量,提高了巷道稳定性。本文研究成果为软岩大巷围岩变形稳定控制提供了理论依据和技术支撑。

大变形巷道限阻耗能型支护结构研究

为了解决深部煤矿开采过程中所遇到的“高地应力、大变形、支护结构破坏”等问题,以朱集东矿东部辅助轨道大巷为工程背景,采用变形监测与数值模拟的方法研究深井软岩巷道围岩变形特征规律;依据围岩耗能支护理念,设计出控制巷道围岩能量释放与变形的“限制支护阻力阻尼器”(简称“限阻器”);通过数值分析与室内静压试验相结合的方式得到限阻器试件的性能指标与设计参数之间的关系,并验证限阻器的工作性能;最后通过数值模拟对比巷道常规支护与限阻耗能支护形式的变形与受力情况,验证巷道限阻耗能型支护方案的可行性。结果表明:限阻器的试验压缩量均达到了80%以上,具有较大的变形行程,在保证初期支护发生较大变形的前提下,达到降低围岩压力、耗散围岩能量的目的。限阻耗能支护较巷道常规支护最大主应力值分别降低51.2%、89.8%,提高了结构的安全性。

静动载条件下深部破碎巷道支护设计及稳定性分析

深部破碎围岩稳定性控制是制约深部金属矿安全高效开采的难题之一。以金川二矿区深部某中段破碎围岩条件下的采准巷道稳定性控制为工程背景,应用Q、RMR、GSI进行岩体质量分级与岩体力学参数估算,分别应用经验法和工程类比法进行采准巷道支护设计,并依据收敛约束法确定合理的释能支护时机。在此基础上,应用UNWEDGE软件对释能支护设计进行安全性评价,并通过RS2数值方法分析支护效果。研究结果表明:对于深部破碎采准巷道一次支护采用锚网喷支护,二次支护采用混凝土衬砌,最佳衬砌支护时机应满足巷道帮位移小于38 mm且顶板位移小于15 mm;静动载下有无支护数值分析结果表明,锚网喷支护满足巷道安全要求,同时对采准巷道围岩结构控制型、应力控制型破坏以及动力失稳破坏等起到良好的控制效果。研究结果为金川二矿区深部破碎采准巷道围岩稳定性控制提供了理论依据与技术支撑。

某煤矿深部软岩巷道围岩破坏特征及控制技术研究

深部矿产资源开发面临地应力大、巷道支护困难等问题。山西某煤矿−590 m水平运输平巷支护结构失效,巷道变形量大,对井下安全生产造成了较大的影响。针对原支护方案存在的问题,提出“锚网索一体化”支护思路,综合采用现场测试、数值模拟、工业实验等手段研究了巷道围岩破坏特征及控制技术。研究表明:(1)巷道围岩水平主应力较高,达到了39.08 MPa,是影响围岩稳定性的主要原因;(2)对不同支护方案巷道周边围岩应力场与塑性区分析表明,优化后支护方案垂直应力较原方案降低了14%,塑性区范围缩小了20%,“一体化”方案支护效果较好;(3)工业应用和锚杆(索)应力测试表明,当锚杆、锚索应力分别达到53.9 kN、389.12 kN时,较原方案提高了14.6%和15.4%,受力效果较好,巷道变形在30 d内控制在200 mm内,较原方案下降了约57%,实现了良好的支护效果。“一体化”支护形式可有效控制围岩变形,为类似地质条件的巷道支护提供参考。

泥岩巷道跨越大巷立交段围岩变形影响因素与控制对策

立交巷道由于掘进扰动相互叠加影响,岩柱承受应力复杂,立交巷道围岩维护困难。为解决巷道立交段围岩控制难题,以里必煤矿岩石底板抽放巷跨越中央辅助运输大巷立交段为工程背景,基于现场试验与矿压监测分析,明确了立交段矿压显现异常的主要影响因素,提出了立交围岩加强支护与施工优化方案,两巷立交段掘进过程中频繁爆破施工,原支护方案难以维持巷道围岩稳定,采用加强支护方案后,锚杆(索)压力趋于稳定,顶板离层量较小,有效控制巷道围岩变形,维护效果良好。