Effect of surface retaining elements on rock stability:laboratory investigation with sand powder 3D printing

This study aims to investigate the benefcial efects of surface retaining elements (SREs) on the mechanical behaviors of bolted rock and roadway stability. 3D printing (3DP) technology is utilized to create rock analogue prismatic specimens for conducting this investigation. Uniaxial compression tests with acoustic emission (AE) and digital image correlation techniques have been conducted on 3DP specimens bolted with diferent SREs. The results demonstrate that the strength and modulus of elasticity of the bolted specimens show a positive correlation with the area of the SRE;the AE characteristics of the bolted specimens are higher than those of the unbolted specimen, but they decrease with an increase in SRE area, thus further improving the integrity of the bolted specimens. The reinforcement efect of SREs on the surrounding rock of roadways is further analyzed using numerical modelling and feld test. The results provide a better understanding of the role of SREs in rock bolting and the optimization of rock bolting design. Furthermore, they verify the feasibility of 3DP for rock analogues in rock mechanics tests.

Stability analysis and control technology of gob‑side entry retaining with double roadways by flling with high‑water material in gently inclined coal seam

To ameliorate the defects of insufcient support resistance of traditional roadside flling bodies for gob-side entry retaining(GER),overcome the inability to adapt to the deformation of surrounding rock,and isolate the goaf efectively,a new type of high-water material as a roadside flling body for GER technology with double roadways was proposed.The instability analysis and control technology of GER with double roadways by flling high-water material into a gently inclined coal seam were studied.The basic mechanical properties of the new high-water material were investigated through laboratory experiments,and their main advantages were identifed.The reasonable width of the roadside flling wall of a high-water material was obtained by combining ground pressure observation and theoretical calculations.The distribution characteristics of the stress and plastic zone of surrounding rock of GER after being stabilized by the disturbance of the working face were studied using numerical simulations,and the failure range of GER by flling with high-water material was revealed.Based on this,a coupling control technology of anchor cables and bolts+single props+metal mesh+anchor bolts is proposed.Through the coupling methods of arranging borehole peeping and observing the convergences of surrounding rock,the results demonstrate that GER with double roadways by flling with a 1.8-m-wide high-water material has a good control efect.The above research will play an active role in promoting the application of high-water materials in GER roadside flling.

Effects of in-situ stress on the stability of a roadway excavated through a coal seam

Roadways excavated through a coal seam can exert an adverse effect on roadway stability. To investigate the effects of in-situ stress on roadway stability, numerical models were built and high horizontal stresses at varying orientations were applied. The results indicate that stress concentrations, roadway deformation and failure increase in magnitude and extent as the excavation angle with respect to the maximum horizontal stress increases. In addition, the stress adjacent to the coal-rock interface sharply varies in space and evolves with time; coal is much more vulnerable to deformation and failure than rock.The results provide insights into the layout of roadways excavated through a coal seam. Roadways should be designed parallel or at a narrow angle to the maximum horizontal stress. The concentrated stress at the top corner of the face-end should be reduced in advance, and the coal seam should be reinforced immediately after excavation.

Research on the width of filling body in gob-side entry retaining with high-water materials

To determine the filling body's width along the gob-side remained roadway which is underneath the gob,the authors analyzed the interaction mechanism between the roof and the supporting body along the remained roadway, based on the elastic thin plate theory of the stope roof. The stress state and mechanical response of the filling body along the remained roadway were studied. Specifically, firstly, the supporting pressure of the coal pillar which is on one side of the gob-side remained roadway was deduced.Also, an equation that is used to calculate the width of the balance area in the stress limit state was acquired. Then, an equation that is used to calculate the roof cutting force on one side of the supporting body was obtained. By using FLAC3D, the authors investigated the displacement field and stress field response laws of rock masses around the roadway with different filling body's widths. The results show that with the filling body's width increasing, the supporting ability of the filling body increases.Meanwhile, the rock mass displacement around the roadway and the filling body deformation decrease.The better the filling body's supporting effect is, the higher the roof cutting force will be. When the filling body's width is larger than 3.0 m, its internal bearing ability becomes stable and the filling body's deformation became non-apparent. Finally, analysis shows that the filling body's width should be 2.5 m.Furthermore, the authors conducted field tests in the supply roadway 1204, using high-water materials and acquired expected outcomes.

Deformation failure mechanism and application of the backfill along the goaf-side retained roadway

In order to determine the rational width of backfill in the goaf-side retained roadway, the deformation failure mechanism of surrounding rock in retained roadway is studied in the use of theoretical analysis, numerical simulation, etc., when the width of backfill is different. The results show that: with the increase of backfill width, the roof deformation above the backfill decreases; the outside of backfill obviously suffers from greater stress compared to the inner side of backfill; the damage firstly appears in the intersection of top backfill and roof; the plastic failure area is mainly distributed in the roof and floor of inside the roadway; 2 m wide backfill in the goaf-side retained roadway can meet the requirements of roadway deformation. Based on the original combination support of "anchor-mesh-belt-lock" in the haulage-track roadway, the study also considers the reinforced support of "anchor-mesh-belt" above the backfill, and 50 m ahead of working face, and 200 m behind the working face. This kind of support achieves a good result. The roadway deformation of field measurement shows that it can satisfy the need of the next working face.

Wide pillar roadway retained in the deep high gas coal seam

According to the geological and mining conditions of deep high gas coal seam,this paper established the mechanical model of stope surrounding rock,and analyzed the stress distribution and deformation failure mechanism of working face and coal pillar.The research determined the arrangement mode that adjacent working faces retain wide pillar,and the reasonable support method of roadway that the combined support of roof and grouting combined together.The reasonable time of reinforced roadway was determined.Through analyzing the mechanical model of the ways of roadway supporting,this research drew the conclusions as follows:the combined support of roof and working slope improved the support strength and range of surrounding rock,optimized the support by adjusting the angle of anchor,and reached the support requirements by using cement grouting in working slope and chemical grout in roof.The technology was applied in 15104 working face of Baoan Mine,and obtained good results.

Analysis on distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face

The three-dimensional damage constitutive relationship of coal is established and distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face under the effect of given deformation of the main roof is analyzed by the damage mechanics theory. And the relationship between distribution of the abutment pressure and thickness of coal seam is explored. The presented result is of great theoretical significance and practical value to the study on stability control of the surrounding rock of road-in packing for gob-side entry retaining in fully-mechanized caving face.

大倾角走向长壁工作面局部充填无煤柱开采理论与技术

大倾角煤层走向长壁采场围岩结构及应力环境异化,工作面不同位置“支架-围岩”系统的构成因素及灾变模式不同,导致工作面安全事故频发、煤炭采出率较低、巷道掘进率高。通过对大倾角采场围岩采动力学行为的分析,提出了大倾角走向长壁工作面局部充填无煤柱开采技术构想,工作面走向推进过程中沿倾向对采空区下部进行局部充填,充填体既与巷旁支护作用形成沿空巷道,取消区段保护煤柱,实现大倾角煤层无煤柱开采,又增大了工作面倾向下部充填压实区长度,加强了工作面“支架-围岩”系统稳定性。根据大倾角走向长壁采场特点,优选确定了大倾角膏体局部充填工艺,设计了大倾角局部充填回采系统、采充工艺。并采用理论分析、模拟实验、数值计算等相结合的方法,分析了局部充填对大倾角走向长壁采场围岩采动力学行为的调节机制。结果表明:充填体影响基本顶岩梁的变形破坏及采场倾向下侧煤岩体承载特征,基本顶、运输巷顶板变形量及运输巷倾向下侧煤岩体所受约束均随充填长度的增大而减小;为防止采空区未充填区悬顶灾害,充填长度不应超过工作面长度的1/3。局部充填体限制了工作面下部区域顶板破断,降低覆岩关键域形成层位,形成稳定的巷帮,减小沿空留巷围岩变形量;同时工作面倾向下部充填区长度增大,中、上部围岩结构不稳定区域的长度缩小,“支架-围岩”系统稳定性提升。充填体改变了采场围岩应力传递路径,承担了部分覆岩载荷,工作面下侧支承压力及超前支承压力均随充填长度的增大而减小,工作面倾向下部充填区域的超前支承压力降幅最大,沿空巷道及工作面应力状态得到改善。大倾角走向长壁工作面局部充填无煤柱开采技术具有提高资源采出率、降低掘进率、缓解采掘接替紧张、加强工作面“支架-围岩”系统稳定性等优势。

大采高综采工作面切顶留巷矸石帮变形控制技术研究

为解决厚煤层大采高综采工作面切顶留巷矸石帮围岩控制难题,首先利用理论分析建立了不同挡矸支护条件下矸石帮位移变化的力学公式,以此为基础提出矸石帮变形控制双策略,减弱矸石帮变形压力和增强矸石帮的抗变形能力;其次利用现场实验设计两种类别共4组挡矸支护方案,探讨不同支护方案的矸石帮控制效果,验证理论研究成果。结果表明:①增强矸石帮侧顶板支护强度,能减弱矸石帮变形压力;②增架卡兰个数、增加卡兰预紧力、增加卡兰个数、增强U型钢之间的摩擦力等能增加U型钢滑移初始滑移应力,增强矸石帮的抗变形能力;③挡矸支护控制效果为:2副卡兰+单体支柱<2副卡兰+单元支架<2副卡兰+单元支架+呛柱<3副卡兰+单元支架。该研究可为同类条件下切顶留巷矸石帮变形控制提供参考。

砂质泥岩巷道顶板定向爆破不耦合装药系数优化与应用

聚能爆破技术在沿空留巷工程项目中有着重要的作用,装药结构问题一直是目前讨论的热点及难点。对于目前沿空留巷顶板超前预裂装药长度尚没有明确的指标情况下,以孟津煤矿二_2-11031工作面轨道顺槽为研究背景,提出了等长装药顶板预裂技术,为明确最优装药结构,本文通过LS-DYNA数值模拟软件建立了三维定向聚能爆破模型,改变轴向药柱的长度,以裂纹扩展长度和应力衰减速率为分析指标,通过数值模拟可知,轴向不耦合系数在1.25~1.7之间径向切缝距离约为40 cm,轴向切缝距离约为80 cm,相比轴向不耦合系数在2~3之间,切缝距离分别提高了25%和12.5%;轴向不耦合系数在1.25~3之间,应力衰减速度均小于1,能量利用最为合理;将轴向不耦合系数α=1.25~2的装药结构在孟津煤矿二_2-11031工作面轨道顺槽进行顶板定向爆破实验,对预裂爆破后的两炮孔中线进行钻孔窥视,观察到4种爆破方案,两炮孔之间沿切缝方向裂纹均已经完全贯通,裂纹光滑平整,现场应用效果良好,结合经济性、安全性两方面考虑,不耦合系数α=1.7为最优;研究结果表明等长装药结构可以代替传统的三段式装药结构。研究结果可以为今后类似的项目提供参考。

厚煤层柔模混凝土墙沿空巷道支护技术研究

柔模混凝土墙沿空留巷技术作为无煤柱开采的一种,现已被应用于我国神东矿区多个煤矿。为解决在留巷复用过程中沿空巷道围岩结构稳定性差、变形剧烈、支护难度大的难题,以大柳塔煤矿52605柔模混凝土墙沿空留巷工作面为工程背景,采用理论分析、数值模拟和现场实测相结合的研究方法,研究了柔模混凝土墙沿空巷道的围岩变形特征,建立柔模混凝土墙沿空巷道围岩结构力学模型,得到从巷道掘进阶段至巷道复用阶段沿空巷道全生命使用周期的应力演化规律,并根据巷道不同的使用阶段提出了对应的支护方案。研究结果表明:上覆岩层作用力直接作用在直接顶与混凝土墙岩层接触位置,有利于侧向支承压力传递,巷道围岩变形较大;二次采动超前支承压力导致留巷段前方顶板发生塑性破坏,塑性破坏与底板塑性区联通,将加剧煤壁侧的破坏;现场工程实践表明对沿空巷道进行合理分时分区支护,可改善应力环境,有效控制围岩变形。

托顶煤切顶留巷围岩控制技术研究

为了解决托顶煤巷道围岩变形难以控制的问题,运用理论分析、离散元数值模拟及现场工业试验相结合的方法对义棠煤业100602工作面切顶成巷围岩控制技术进行研究,分析了不同切顶高度、采高对留巷围岩变形影响规律。研究发现,适当增加切顶高度并降低采高有利于巷道围岩稳定,并确定开采技术参数为切顶高度24 m、采高6 m。现场监测结果显示,在合理的支护策略及开采工艺参数下,托顶煤切顶留巷围岩变形控制效果良好。

急倾斜中厚煤层单一巷道放顶煤采煤方法研究与应用

为解决某矿急倾斜中厚煤层倾角及厚度变化大的开采问题,提出了“急倾斜中厚煤层单一巷道放顶煤采煤方法”。该采煤方法是沿急倾斜煤层倾斜方向划分为若干区段,每个区段沿急倾斜煤层走向仅布置1条巷道。此巷道服务于1个采煤区段,担负工作面通风、运输和行人等任务。对单一巷道放顶煤采煤方法的巷道布置、综放工艺和沿空留巷方法进行了探讨。实践表明,该采煤方法使采煤工作面形成全负压通风,避免了巷道与采空区窜风,杜绝了采空区瓦斯积聚和遗煤自燃,实现了采煤机械化,提高了急倾斜中厚煤层的开采效率和煤炭回收率。单一巷道放顶煤采煤法为类似急倾斜煤层安全、高效开采提供了技术支撑。

长城六矿中硬顶板倾斜工作面切顶留巷关键参数研究

针对长城六矿1301S工作面沿空巷道围岩破坏失稳控制难题,首先,采用UDEC数值模拟方法揭示了1301S工作面侧向覆岩破断运动规律,发现侧向覆岩破断位置均位于巷道上方,且直接顶悬臂结构长度约为1.8m;其次,通过构建侧向覆岩结构力学模型,获得了切顶前后实体煤和矸石支撑体支承应力解析表达式,根据表达式进行算例分析得到切顶前后实体煤支承应力保持不变,均为1.27MPa,靠近巷道左侧矸石支撑体支承应力降低了56.89%;再次,通过理论计算确定了巷旁切顶参数,即切顶高度11m、切顶角度20°、切缝孔间距500mm;最后,设计了1301S工作面运输顺槽切顶留巷技术方案并开展了工业性试验。研究结果表明:切顶后巷道顶底板移近量和两帮移近量分别为1240mm和265mm,与未切顶相比分别降低了12.68%和70.22%,围岩整体稳定性较好。该研究可为相同或相似条件下切顶留巷技术应用及关键参数设计提供参考和借鉴。

沿空留巷工艺配套成套支护装备技术

介绍了沿空留巷工艺行业发展现状和趋势,根据现有沿空留巷配套支护装备存在支护效果不理想、效率低、安全性差的问题,研制了采空区挡矸支架组、后伸缩端头支架、循环交替支护成套装备。阐述了成套支护装备的总体结构、主要特点、运行方式、巷道中的布置方式以及使用效果。

深部大采高工作面沿空留巷围岩控制技术

综采工作面沿空留巷经历多次采动影响,矿压显现较为强烈,围岩变形量大,极易造成巷道围岩失稳。为了研究大采高工作面沿空留巷围岩控制问题,以某矿1313工作面留巷为研究背景,通过理论分析、数值模拟、现场实践等方法,分析沿空留巷围岩运动特征,提出“支-卸平衡”巷道围岩协同控制技术;加强了巷道围岩支护强度,改善了巷道围岩的应力环境。通过现场工程实践验证,1313工作面留巷的巷道顶底板变形量为246 mm,两帮变形量为442 mm,巷道表面没有明显的鼓出现象,巷道围岩变形量满足作业规程的相关规定。

Z形工作面切顶留巷端头液压支架的研制

针对董东煤矿TC10工作面Z形条带开采工作面切顶留巷,研发了一种具有端头支护、巷道支护、切顶留巷、自移功能的端头支架,可布置在机尾处用于巷道支护和切顶留巷,可实现在工作面设备连续推进5个步距时架后巷道棚顶1次,减轻了劳动强度,提高了工作面采煤效率。

采煤弓形柔性掩护支架沿空留巷技术分析

以山西A矿3062工作面大倾角煤层为例,设计了弓形柔性掩护支架沿空留巷技术方案。首先,介绍了大倾角煤层的基本情况,以此为基础,分析了弓形柔性掩护支架结构设计的内容与安装流程,并根据大倾角煤层特点,探讨了弓形柔性掩护支架的受力情况;其次,通过案例分析的方式验证了该技术的应用效果;最后,确定了利用弓形柔性掩护支架沿空留巷技术后,可以提高煤层顶底板的稳定性,减小变形量,有利于煤矿开采工作的开展。

综采工作面沿空留巷支护技术应用

随着煤矿开采深度的加大,以往可获得良好支护效果的传统支护方法,在诸多条件下已出现显著的支护不协调、支护强度低等问题。在进行沿空留巷支护时,出现了与上述类似的问题,给整个综采工作面的正常开采带来了很大的困难。主要介绍了当前综采工作面沿空留巷支护技术应用存在的问题及原因,重点分析了综采工作面沿空留巷的巷旁支护技术和巷内支护技术。

厚煤层沿空留巷“煤-支护体”组合承载结构力学特性分析

针对厚煤层沿空留巷围岩控制难题,以王庄煤矿为工程背景,通过理论分析、数值模拟的研究手段,阐述了厚煤层沿空留巷巷旁支护体的失稳机理,提出了“切顶卸压改善留巷围岩应力环境+调节巷旁支护体高度以协调组合承载结构承压—让压能力”的围岩控制对策。研究表明,“煤—支护体”组合承载结构中,随支护体占比的减少,组合体抗压强度呈现出“急降—缓降—急降”的趋势,峰值应变呈现出“平稳—线性增长—平稳”的趋势。结合王庄煤矿数值模拟结果可得,支护体占比为80%时,“煤—支护体”组合承载结构兼具有较好的承压能力与让压能力,避免了基本顶沿留巷煤帮切顶下沉,优化了留巷围岩的应力环境。研究成果可为厚煤层沿空留巷技术提供理论参考。