Cable-truss supporting system for gob-side entry driving in deep mine and its application

In order to solve the large deformation controlling problem for surrounding rock of gob-side entry driving under common cable anchor support in deep mine, site survey, physical modeling experiment, numerical simulation and field measurement were synthetically used to analyze the deformation and failure characteristics of surrounding rock. Besides, applicability analysis, prestress field distribution characteristics of surrounding rock and the control effect on large deformation of surrounding rock were also further studied for the gob-side entry driving in deep mine using the cable-truss supporting system. The results show that, first, compared with no support and traditional bolt anchor support, roof cable-truss system can effectively restrain the initiation and propagation of tensile cracks in the roof surrounding rock and arc shear cracks in the two sides, moreover, the broken development of surrounding rock, roof separation and extrusion deformation between the two sides of the roadway are all controlled; second, a prestressed belt of trapezoidal shape is generated in the surrounding rock by the cable-truss supporting system, and the prestress field range is wide. Especially, the prestress concentration belt in the shallow surrounding rock can greatly improve the anchoring strength and deformation resisting capability of the rock stratum;third, an optimized support system of ‘‘roof and side anchor net beam, roof cable-truss supporting system and anchor cable of the narrow coal pillar" was put forward, and the support optimization design and field industrial test were conducted for the gob-side entry driving of the working face 5302 in Tangkou Mine, from which a good supporting effect was obtained.     

Stability assessment of rock surrounding an I-beam supported retreating roadway

The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.     

构造应力区巷道变形破坏特征及控制技术研究

水平构造应力对巷道围岩稳定有重要的影响,针对鹤壁九矿东总回风巷在锚网索喷＋u型钢支护难以保证巷道稳定的情况,通过相似材料模拟试验研究不同水平应力作用下锚注支护巷道围岩变形破坏和位移变化特征．试验表明,随着水平应力的增大,底板加强后,水平应力对顶板的作用明显,当水平载荷达到49MPa时有少量浆皮脱落,左肩部出现块状冒落,底板比较稳定,没有发生明显臌起,只出现少量横向裂隙,锚注支护结构能控制围岩变形．将试验结果在现场应用后,通过矿压观测,两帮的最大移近量为144mm,顶底板最大移近量为105mm,锚注支护提高了围岩的自承能力,能够维持巷道稳定,为类似地质条件下的巷道支护提供借鉴．     

深部复合顶板巷道变形破坏机理研究

高应力下软弱复合顶板的持续塑性变形破坏,是深矿井巷道支护与维护的难点之一.分析了车集煤矿2405工作面区段运输平巷和区段回风平巷的围岩结构和岩性特征,构建了该类巷道复合顶板的力学模型,导出了该模型的力学变形方程.对巷道顶板变形破坏机理进行了深入分析,认为当巷道顶板岩层所受轴向压力大于岩梁达到屈服时的临界压力0.8倍时,巷道变形(下沉)明显增大,严重时产生冒顶.提出了同类巷道掘进过程中围岩控制的关键措施.     

Support technology for mine roadways in extreme weakly cemented strata and its application简

For the engineering geology conditions of bad mine roadway roof and floor lithology in extremely weak cemented strata, the best section shape of the roadway is determined from the study of tunnel surrounding rock displacement, plastic zone and stress distribution in rectangular, circle arch and arch wall sections, respectively. Based on the mining depth and thickness of the coal seam, roadway support technology solutions with different buried depth and thickness of coal seam are proposed. Support schemes are amended and optimized in time through monitoring data of the deformation of roadway, roof separation, I-beam bracket, bolt and anchor cable force to ensure the long-term stability and security of the roadway surrounding rock and support structure. The monitoring results show that mine roadway support schemes for different buried depth and section can be adapted to the characteristics of ground pressure and deformation of the surrounding rock in different depth well, effectively control the roadway surrounding rock deformation and the floor heave and guarantee the safety of construction and basic stability of surrounding rock and support structure.     

大断面厚顶煤巷道围岩控制与支护参数优化

以山西大同同忻矿8104综放工作面回风巷(断面尺寸5.2 m×3.5 m)为工程研究背景,阐述了厚顶煤大断面巷道的围岩控制难题:顶煤裂隙发育、变形强烈、破坏范围大、易发生离层和冒顶等事故.结合现场地质生产条件,采用桁架锚索加强支护,并分析此支护系统的优越性:提供水平和竖直方向预紧力、变形闭锁、协同承载控制区域、锚固点稳.采用FLAC3D数值模拟计算了桁架锚索倾斜角度从10~40°变化过程中围岩变形规律:随着桁架锚索倾斜角度的增大,巷道围岩变形量先减小后增大,锚索倾斜20°时,巷道围岩变形量最小.表明回风巷受到采动影响后,顶底板最大移近量为395 mm,两帮最大移近量为263 mm.     

深部沿空切顶成巷围岩稳定性控制对策

基于沿空切顶成巷技术原理,以城郊煤矿深部工作面无煤柱开采为背景,综合运用力学分析﹑模拟计算和现场试验等方法,对深部切顶成巷围岩控制关键对策进行深入研究。结果显示：切顶留巷顶板在侧向形成短臂梁结构,降低了巷旁支护体所受压力,切缝范围内岩层垮落后碎胀充填采空区,使留巷顶板下沉量降低了约50%。采空区侧顶板为切顶巷道围岩变形的关键部位,需进行加强支护;深部切顶巷道实体煤帮塑性区范围大,通过煤帮锚索支护技术可将浅部锚杆承载层锚固在弹性区稳定煤体中;深部切顶成巷来压速度快、强度大,巷内单体支柱易造成冲击破断,采用高阻力液压支架巷内临时支护时可较好地抵抗深部强动压;巷旁刚性挡矸装置因无法适应深部围岩大变形而受压弯曲破坏,深部切顶巷道巷旁挡矸结构需实现一定的竖向让位卸压方可与顶底板协调变形。在研究的基础上提出恒阻锚索关键部位支护+可缩性U型钢柔性让位挡矸+巷内液压支架临时支护+实体煤帮锚索补强的深部切顶成巷联合支护技术,并进行现场工业性试验。现场监测结果表明：留巷围岩在滞后工作面约290 m时基本稳定,且稳定后各项指标满足下一工作面使用要求。     

突出矿井深部新水平开采瓦斯综合治理模式研究

针对矿井浅部瓦斯治理模式已不能保障深部采区安全高效生产的现状,提出一种适宜矿井深部新水平开采的瓦斯综合治理模式.工作面消突采用底板岩巷穿层钻孔预抽煤巷条带瓦斯;底板岩巷布置“一巷多用”,在工作面回采工程中可兼做回风巷、尾抽巷、措施巷;回采工作面采用沿空留巷Y型通风综合治理瓦斯.其中,顺层钻孔预抽本煤层瓦斯,高位钻场顶板走向钻孔抽采裂隙带瓦斯,上隅角、尾巷埋管抽采采空区瓦斯,形成矿井三维立体瓦斯抽采体系.     

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.     

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.     

Deformation and failure characteristics of anchorage structure of surrounding rock in deep roadway

This paper investigated the stress evolution, displacement field, local deformation and its overall distribution, and failure characteristics of the anchorage structure of surrounding rock with different rockbolt spacing through the model experiments. The influences of the pre-tightening force and spacing of rockbolt on the support strength of the anchorage structure of surrounding rock were analyzed by the simulation using FLAC3D numerical software. The support scheme of the excavated roadway was then designed, and the effectiveness of this support scheme was further verified by the displacement measurement of the roadway. The results showed that the maximum displacement between the roof and floor of the west wing track roadway in Kouzidong coal mine, China is about 42 mm, and the maximum displacement between its both sides is about 72 mm, indicating that the support scheme proposed in this study can ensure the stability and safety of the excavated roadway.     

Numerical research on stability control of roofs of water-rich roadway

In order to study the strength-weakening law of roofs of water-rich roadway, this study used FLAC software, and simulated and analyzed the failure characteristics of the surrounding rock of water-rich roadway under the condition of different cross sections and support parameters, finally obtained the stress distribution of the principle stress of the roadway as well as the displacement variation of its surrounding rock. Results indicate that the roof stability of roadway with semicircular cross section is better than the roadway with inclined rectangular cross section under water-rich condition. Besides, the surrounding rock deformation of roadway under the action of water shows a pronounced increase compared to the roadway without the action of water due to the fact that water will obviously weaken the surrounding rock of roadway, especially its roof. It is very beneficial to control roof stability of water-rich roadway and guarantee the roadway stability during its service life by improving the pretension of bolt and cable as well as decreasing inter-row spacing of the bolt.     

Failure mechanism and control technology of water-immersed roadway in high-stress and soft rock in a deep mine

Aiming at soft rock ground support issues under conditions of high stress and long-term water immersion, the ground failure mechanism is revealed by taking the deep-water sumps of Jiulong Mine as the engineering background and employing field investigation, tests of rock structure, mechanical properties and mineral composition. The main factors leading to the surrounding rock failure include the high and complex stress state of the water sumps, high-clay content and water-weakened rock, and the unreasonable support design. In this paper, the broken and fractured rock mass near roadway opening is considered as ground small-structure, and deep stable rock mass as ground large-structure. A support technology focusing on cutting off the water, strengthening the small structure of the rock and transferring the large structure of the rock is proposed. The proposed support technology of interconnecting the large and small structures, based on high-strength bolts, high-stiffness shotcrete layer plugging water,strengthening the small structure with deep-hole grouting and shallow-hole grouting, highpretensioned cables tensioned twice to make the large and small structures bearing the pressure evenly,channel-steel and high-pretensioned cables are used to control floor heave. The numerical simulation and field test show that this support system can control the rock deformation of the water sumps and provide technical support to similar roadway support designs.     

深部巷道围岩控制原理与应用研究

采用理论分析、数值模拟和现场试验的方法，研究深部巷道围岩稳定问题，认为深部巷道围岩控制的基本方法是提高围岩强度、转移围岩高应力以及采用合理的支护技术．提出了深部巷道围岩控制的基本技术和控制过程：1）应力转移降低巷道浅部围岩应力；2）采用高预紧力、大延伸量的高强度锚杆、锚索支护系统，强化锚固区围岩强度，提高巷道围岩自身稳定性；3）加强巷道两帮、底角支护，提高巷道最薄弱部位（两帮、底角）残余强度、提高巷道围岩的整体稳定性；4）应用高水速凝材料注浆加固破碎区，提高破碎围岩的完整性和力学参数．该研究成果已成功应用于工程实践．     

Failure laws of narrow pillar and asymmetric control technique of gob-side entry driving in island coal face

In allusion to the problems of complex stress distribution in the surrounding rock and deformation failure laws, as well as the difficulty in roadway supporting of the gob-side entry driving in the island coal face, 2107 face in Chengjiao Colliery is researched as an engineering case. Through physical mechanical test of rock, theoretical and numerical simulation analyses of rock, the analysis model of the roadway overlying strata structure was established, and its parameters quantified. To reveal the deformation law of the surrounding rock, the stability of the overlying strata structure was studied before, during and after the roadway driving. According to the field conditions, the stress distribution in coal pillar was quantified, and the surrounding rock deformation feature studied with different widths of the pillars in gob-side entry driving. Finally, the pillar width of 4 m was considered as the most reasonable. The research results show that there is great difference in support conditions among roadway roof, entity coal side and narrow pillar side. Besides, the asymmetric control technique for support of the surrounding rock was proposed. The asymmetric control technique was proved to be reasonable by field monitoring, support by bolt-net, steel ladder and steel wire truss used in narrow pillar side.     

Numerical simulation study on hard-thick roof inducing rock burst in coal mine

In order to reveal the dynamic process of hard-thick roof inducing rock burst, one of the most common and strongest dynamic disasters in coal mine, the numerical simulation is conducted to study the dynamic loading effect of roof vibration on roadway surrounding rocks as well as the impact on stability. The results show that, on one hand, hard-thick roof will result in high stress concentration on mining surrounding rocks; on the other hand, the breaking of hard-thick roof will lead to mining seismicity, causing dynamic loading effect on coal and rock mass. High stress concentration and dynamic loading combination reaches to the mechanical conditions for the occurrence of rock burst, which will induce rock burst. The mining induced seismic events occurring in the roof breaking act on the mining surrounding rocks in the form of stress wave. The stress wave then has a reflection on the free surface of roadway and the tensile stress will be generated around the free surface. Horizontal vibration of roadway surrounding particles will cause instant changes of horizontal stress of roadway surrounding rocks; the horizontal displacement is directly related to the horizontal stress but is not significantly correlated with the vertical stress; the increase of horizontal stress of roadway near surface surrounding rocks and the release of elastic deformation energy of deep surrounding coal and rock mass are immanent causes that lead to the impact instability of roadway surrounding rocks. The most significant measures for rock burst prevention are controlling of horizontal stress and vibration strength.     

深埋巷道破裂围岩位移分析

针对深埋巷道围岩普遍处于破裂状态的特点，采用非连续变形分析（DDA）软件对巷道围岩松动圈非连续体位移影响因素的变化规律进行了模拟研究．分析了用锚杆、锚索和注浆加固以增加围岩破裂面的黏结力、抗拉强度和内摩擦角的数值朱减少位移量的机理，提出了非连续体巷道失稳破坏的判断标准，并对埋深1159m的大松动圈围岩巷道的非连续体位移进行了定量计算和实地观测．实测结果与DDA软件计算值比较吻合，说明对于深埋巷道破裂围岩采用DDA方法进行位移计算和支护参数设计是可行的．     

Stress distribution and surrounding rock control of mining near to the overlying coal pillar in the working face

The occurrence of overlying coal pillar (OCP) exerts a strong effect on the stress and strain distribution of the surrounding rock in the stope. In this paper, the stress distribution characteristics are analyzed via the numerical calculation with the account of OCP presence or absence. In addition, this study revealed the joint effect of side pressure relief area of the goaf and stress concentration in OCP on the final stress distribution. Furthermore, the rules of abutment stress distribution affected by three influencing factors, namely horizontal-vertical distances between OCP and working face and buried depth of OCP, are analyzed. The functional model linking the peak stress of surrounding rock with the above influencing factors is developed. The field application of the above results proved that the rib spalling and deformation of a 2.95 m-high and 5.66 m-wide roadway could be efficiently controlled by rationally adjusting working states of the support, and adopting the hydraulic prop coordinated with the π type metal beam and anchor cable to strengthen the surrounding rock of working face and roadway, respectively. The proposed measures are considered appropriate to satisfy the safe operation requirements.     

Effect of a single weak lithological structure on the height of a collapsing roof in a deep soft rock roadway

Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding rocks. This thesis analyzes the effect of two single and weak lithological structures of both sides and the roof on the height of a collapsing roof in a deep soft rock road-way. Using the two-dimensional UDEC3.1 software, a numerical simulation was carried out on the models of weak lithological structures of both sides of a roadway and of two weak lithological structures of roof of different depths. We reconstruct the overall processes from a break-away layer, bending, subsidence and the cracking of a collapsing roof. We also illustrate the distribution characteristics of displacement fields in the surrounding rock after the roof collapse in a deep soft rock roadway. The results of our numerical simulations indicate that the form of a roof collapse is side-expanding when the roadway is a weak structure at both sides. The height of the roof collapse is related to the lithological combination of the roof when the roadway is a weak structure of the roof.     

Characteristics of stress distribution in floor strata and control of roadway stability under coal pillars

Given the difficulties encountered in roadway support under coal pillars, we studied the characteristics of stress distribution and their effect on roadway stability, using theoretical analysis and numerical simulation. The results show that, under a coal pillar, vertical stress in a floor stratum increases while horizontal stress decreases. We conclude that the increased difference between vertical and horizontal stress is an important reason for deformation of the surrounding rock and failures of roadways under coal pillars. Based on this, we propose control technologies of the surrounding rock of a roadway under a coal pillar, such as high strength and high pre-stressed bolt support, cable reinforcement support,single hydraulic prop with beam support and reinforcement by grouting of the surrounding rock, which have been successfully applied in a stability control project of a roadway under a coal pillar.