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.

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.

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.

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.

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.

Mechanism of rock deformation and failure and monitoring analysis in water-rich soft rock roadway of western China

Aiming to get the strata behavior and stability rules of surrounding rock of the main return airway of Yushujing Coal Mine, convergence deformation of two sides and force of U-shaped steel yieldable support and bolt were monitored, and deformation of surrounding rock and mechanical characteristics of support structure were timely obtained to guide the informa- tion construction and optimize supporting parameters in water-rich soft rock roadway. The field monitoring results indicate the following. （1） Convergence displacement of rock surface increases with time continuity and shows surrounding rock＇s intense theological behavior. The original support scheme cannot control the large deformation and strongly theological behavior; （2） Without backfilling, the U-shaped steel support begins to bear load after erecting for 4-7 days and increases rapidly in the first 30 days. The U-shaped steel support at the right shoulder and top of roadway bears a larger force and the left side and shoulder bears a smaller force; （3） The stress of bolt increasing over time and at the right shoulder of roadway has larger growth and value. The mechanism of rock deformation and the failure and strata behavior in water-rich soft rock roadway are revealed based on the results of the measured relaxation zone of surrounding rock, measured stresses, and the rock mechanics tests.

Experimental study on stability control technology of surrounding rock of deep roadways in coal mine

In order to solve effectively the problems of deep mining with safety and high efficiency, the multi- pie factors influencing the stability of deep rock roadway and technical problems are analyzed in the light of the severe situation of effective mining for deep coal resource, and the stability control methods for deep rock road- way are provided, which are based on the idea of combined support with separated steps and integral control of surrounding rock of deep rock roadway. The suggested methods were applied to a deep rock roadway with -648 m depth in Gubei coal mine of Huainan area. The field test was carried out and the in-situ monitoring was imple- mented, and the support scheme was optimized and adjusted to improve the stability of the surrounding rock of the roadway based on the feedback analysis. The results showed that the stability can be improved greatly by the provided control methods tbr deep roadway. The present methods lbr stability control of deep rock roadway can be used to other deep rock roadways with the similar conditions.

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.

Geotechnical characterization of red shale and its indication for ground control in deep underground mining

Geotechnical properties of red shale encountered in deep underground mining were characterized on both laboratory and field scale to reveal its unfavorably in geoenvironment.Its constituents,microstructure,strength properties and water-weakening properties were investigated.In situ stress environment and mining-induced fractured damage zone after excavation were studied to reveal the instability mechanism.The results show that red shale contains swelling and loose clayey minerals as interstitial filling material,producing low shear strength of microstructure and making it vulnerable to water.Macroscopically,a U-shaped curve of uniaxial compressive strength(UCS)exists with the increase of the angle between macro weakness plane and the horizon.However,its tensile strength reduced monotonically with this angle.While immersed in water for72h,its UCS reduced by91.9%comparing to the natural state.Field sonic tests reveal that an asymmetrical geometrical profile of fractured damage zone of gateroad was identified due to geological bedding plane and detailed gateroad layout with regards to the direction of major principle stress.Therefore,red shale is a kind of engineering soft rock.For ground control in underground mining or similar applications,water inflow within several hours of excavation must strictly be prevented and energy adsorbing rock bolt is recommended,especially in large deformation part of gateroad.

深部采矿岩石力学进展

随着煤炭开采日益向深部发展,深部采矿引发的围岩大变形破坏和强冲击动力灾害日益严峻。在深部高地应力、高地温、高渗透压、强采动、强流变及多场耦合的复杂地质力学环境下,深部采场的应力场特征、煤岩体破碎性质、岩层移动及能量的积聚释放规律等均发生了显著变化。针对深部采矿中的岩石力学问题,论述了笔者及团队在深部采煤方法、深部巷道破坏机理与围岩控制、深井热害与地热利用三大方向取得的进展,主要包括:(1)提出了平衡开采理论和实现平衡开采的110/N00工法,进行了千米深井现场工程应用;(2)构建了深部“非均压建井”模式,研发了实现深井稳定提升的SAP系统,形成了可大幅简化井巷工程量和提高矿井采出率的建井方法;(3)研发了多套适用于研究深部岩体在水、高温、高压、结构效应及多场耦合作用下发生宏观破坏的实验系统和可进行微观层面演算的超算系统,揭示了深部软岩大变形破坏机理及多尺度力学特性;(4)研制了深部岩体冲击型和应变型岩爆实验系统,阐述了深部岩体冲击能量沿开挖临空面瞬间释放的非线性动力学行为;(5)提出了深部巷道开挖补偿支护理论,进一步发展了具有高恒阻、高延伸率、强吸能和耐冲击超常力学特性的NPR支护材料和技术;(6)研发了模拟深部高温、高湿和高压环境下的岩体热力学实验系统,提出了热害治理和热能资源化利用方法,建立了深部热害治理与热能综合利用系统(HEMS)。相关研究成果已在深部开采领域得以应用,可为深部采矿面临的复杂岩石力学问题提供借鉴。

深井松软围岩煤巷采动增跨效应及防控技术

针对深井松软煤巷围岩变形严重、巷道支护困难等问题,以城郊煤矿LW21106工作面沿空巷道为工程背景,建立了采动巷道增跨模型,揭示了采动增跨效应演化机理。通过构建巷道顶板横纵弯曲梁模型,指出顶板横向受力、巷道等效跨度、煤岩强度是巷道围岩损伤破坏的主控因素,提出了采动增跨效应防控对策并进行工业性试验。研究结果表明:受采动影响,巷道经历“初始围岩稳定—围岩裂隙发育扩展—围岩剪切破坏加剧—等效跨度增加”过程;巷道顶板最大正应力与应力集中系数、顶板等效跨度、巷道断面尺寸及埋深成正相关关系;巷道顶板在高应力环境下易发生拉剪破坏,增加顶板锚索数量以及锚索预紧力有利于增强顶板初期完整性。基于巷道变形破坏主控因素,提出“围岩加固–卸压–强化支护”协同防控策略;针对现场条件,采用煤柱侧向切顶+注浆加固并对破碎区域补充锚索强化支护的防控技术。现场监测结果表明,煤柱帮最大移近量为18.89cm,顶板下沉量为25.86cm,两帮移近量为29.65 cm,有效控制了煤巷围岩变形,为深井松软围岩巷道变形控制提供了参考。

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。

深部近距离煤层群下分层巷道分区支护技术

为实现深部近距离煤层群下分层巷道安全,以张双楼煤矿21916工作面为工程背景,分析了工作面冲击地压影响因素,划分了21916工作面掘进期间巷道冲击危险区域;建立了煤层合并区域下分层回采巷道数值模型,研究了9煤层21916工作面巷道内错7煤采空区不同距离时应力和位移分布规律,确定了下分层巷道合理位置;基于冲击危险区域划分结果,提出了分区支护技术,并设计了支护参数。现场实测表明,下分层巷道最大两帮移近量为164 mm,最大顶底板移近量为84 mm,顶板深部和浅部的离层量不大于3 mm,帮部锚杆和顶部的锚索受力变化较小,顶锚杆受力从8 kN增加到12 kN后趋于稳定,表明21916工作面巷道布置合理,分区防冲支护技术合理,支护质量与效果显著。研究结果可为类似条件工作面防冲支护提供借鉴。

深井高应力大巷煤柱释能改性防冲机理及应用

针对当前我国深井高应力大巷煤柱频繁发生冲击地压的现状,采用现场调查、理论分析、数值模拟和工程试验等方法,研究了我国大巷煤柱冲击地压发生类型与机理,提出了一种高应力大巷煤柱释能改性防治冲击地压的新方法,基于该方法开展了防冲原理研究、技术体系设计、井下工业试验等一系列研究工作,得到:基于大巷煤柱冲击地压的主导力源类型,结合多起冲击地压典型案例,将我国大巷煤柱冲击地压划分为基础应力叠加型、附加应力诱发型和自身蠕变失稳型3类,分别建立并推导了3类大巷煤柱冲击地压发生机理的力学模型与工程判据,揭示了3类大巷煤柱冲击地压的发生机制。提出一种深井高应力大巷煤柱压裂−注浆协同防治冲击地压的方法,其防冲原理体现在“释能”和“改性”2个方面,井下工业试验发现弹核煤体起裂压力约40 MPa,整体最大压裂宽度达19.5 m,现场监测验证该方法能够降低大巷煤柱能量积聚水平,提高大巷煤柱整体冲击阈值。设计了深井高应力大巷煤柱释能改性防冲成套技术体系,包括孤立煤体冲击危险“评估−检验−校核”方法、弹性核水力压裂增缝释能技术和整体注浆加固改性技术。研发了大巷煤柱弹性核压裂“震动−应力−位移”三场监测设备和PS-Z-A/B型无机双组份速凝整体注浆改性材料。

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。

深部巷帮煤体失稳机制及能量释放特征

冲击地压灾害已成为国内外煤矿井下开采的重大安全隐患。利用真三轴电液伺服加载试验系统,研究了巷帮煤岩组合体三向应力加载、煤体三向和两向应力加载下的应力-应变规律、破坏特征、声发射活动规律,建立了巷帮深、浅部煤体的强度准则关系,分析了深部巷帮煤体的能量释放特征,揭示了深部巷帮煤体失稳诱冲机理。结果表明:不同应力类型的煤体试样受应力环境及结构差异的影响,巷帮浅部煤体试样和高σ_(2)围压条件下的巷帮煤岩组合体试样在峰值应力后均产生应力快速跌落现象,脆性破坏与冲击性较强;在破坏机制上,巷帮浅部煤体试样主要受张拉−剪切耦合机制控制;巷帮深部煤体试样主要受剪切机制控制;巷帮煤岩组合体试样靠近约束面、自由面区域分别受剪切、张拉−剪切耦合机制控制。同围压条件下巷帮浅部煤体更容易破坏,进而基于巷道煤帮冲击能量释放的来源,建立了深部巷帮煤体失稳模型,揭示了深部巷帮煤体失稳机制。

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。

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。