综放巷内充填沿空留巷工业试验

针对常村煤矿S2-6综放工作面采用传统技术沿空留巷的难点，进行了巷内充填沿空留巷工业试验．试验分三步进行：第一步，对原巷采用锚梁网索联合支护实施加固，撤掉梯形架棚；第二步，在已加固巷道下一工作面侧煤壁，实施扩帮锚网支护；第三步，在原巷位置实施巷内充填，并加固充填体．结合高水速凝充填材料的性能，通过建立合理的综放沿空留巷的围岩结构力学模型和充填工艺设计，井下工业试验达到了预期效果，留巷断面稳定后超过10m^2．证明了在巷内基本支护为梯形金属支架的巷道中进行综放沿空留巷的可行性，并作了经济效益评价．在此基础上提出了综放巷内充填沿空留巷新技术．     

放顶煤开采沿空留巷围岩移动规律及变形特征

运用适于分析岩层断裂和垮落的数值模拟软件UDEC建立了相应的模型，分析了综放沿空留巷围岩应力和位移的演变过程、围岩移动的特征，阐述了巷道和充填体上方顶煤的位移及其与上覆岩层破断之间的关系，为沿空留巷充填体参数选择提供科学依据．     

窄煤柱工作面沿空留巷围岩大变形控制技术及应用

针对窄煤柱工作面沿空留巷巷旁支护体参数不合理和围岩严重变形等问题,研究了不同巷旁支护体宽度、强度和充填率对窄煤柱工作面沿空留巷围岩变形破坏的影响。研究结果表明:充填体宽度、强度和充填率不同,对窄煤柱工作面沿空留巷围岩应力分布及变形有很大影响;充填体宽度、强度和充填率过低时充填体承载能力较小,沿空留巷围岩变形量较大;过高时顶板下沉量减小不明显,使成本增加;充填体宽度2 m,强度为30 MPa,充填率95%以上,可保证沿空留巷围岩稳定;提出的"巷内锚网索+巷旁充填柔模混凝土墙+单体柱+基本底注浆"联合支护技术,控制了沿空留巷围岩的大变形。工业性试验结果表明:沿空留巷顶底板移近量最大值600 mm,两帮移近量最大值为435 mm,分别是原方案变形量的55. 5%和51. 6%,沿空留巷围岩变形得到有效控制,能满足通风和安全生产的要求。     

综放沿空留巷充填体稳定性控制

基于综放沿空留巷的矿压模型,计算出充填体稳定所需的强度和能适应的变形量,并以此选出充填材料及其水灰比．为提高充填体的整体支护强度和抗变形能力,重点阐述了空间锚栓加固网技术及其对充填体稳定性的控制效果,为缩放大断面沿空留巷技术的成功试验莫定了坚实基础。     

综放沿空小断面留巷技术研究

随着开采强度的增加，综放工作面的瓦斯超限问题日益突出．以王庄煤矿5201综放面为例，提出采用综放沿空小断面留巷技术，布置J型通风系统，治理综放工作面瓦斯超限．由关键块的分析和数值模拟结果，确定了综放沿空小断面留巷的断面形状，给出了斜梁的合理支护设计．矿压观测结果表明，留巷小断面变形以及留巷煤帮深部位移有较好的收敛性，能够满足工作面抽放瓦斯的需要．     

“三软”煤层综放开采避开动压沿空留巷方法及应用

为实施"三软"煤层综放面沿空留巷,掌握留巷围岩结构和矿压变化规律,以新登煤矿31061综放面为研究对象,研究采空区侧向覆岩结构和应力分布,综放面后方沿空留巷变形和顶板压力分阶段变化规律,提出了避开动压沿空留巷方法,并在现场进行了工业试验。研究表明:(1)31061采空区侧向煤壁变形量大,应力降低区范围大,应力集中影响范围达到煤体内部30 m。(2)留巷矿压显现分为3个阶段。工作面后方30~40 m为巷道加速变形阶段,从工作面后方5 m留巷变形速度持续增加,但顶板压力升高较慢;工作面后方40~70 m为变形持续阶段,此阶段巷道变形速度保持稳定,顶板压力快速升高,临时支架产生变形破坏;工作面后方70 m以后为变形稳定阶段,此阶段变形速度明显降低,顶板压力趋于稳定。(3)避开动压沿空留巷方法是利用临时支护使留巷度过动压影响阶段,允许巷道有较大变形量,在工作面后方一定距离处对留巷进行扩修和加固。实践表明,该方法具有成本低、工艺简单、留巷后期稳定性好、留巷施工与采面生产互不干扰等优点,在条件适合的矿区值得推广。     

晋城矿区9号煤沿空留巷试验研究

结合具体条件进行了巷旁充填支护参数设计 ,在矿压观测基础上 ,分析了留巷围岩变形及充填体载荷特征 ,把高水速凝充填材料沿空留巷与炮掘及综掘成巷方法进行经济对比 ,结果表明 ,该留巷方法有明显技术和经济优势 ,在晋城矿区 9号煤中有很好推广应用价值 .     

晋城矿区9号煤沿空留巷试验研究

结合具体条件进行了巷旁充填支护参数设计 ,在矿压观测基础上,分析了留巷围岩变形及充填体载荷特征,把高水速凝充填材料沿空留巷与炮掘及综掘成巷方法进行经济对比,结果表明,该留巷方法有明显技术和经济优势, 在晋城矿区9号煤中有很好推广应用价值.     

高应力综放工作面切顶卸压沿空留巷开采技术研究

为了研究大埋深、高应力、坚硬顶板等特殊地质条件下的综放工作面切顶卸压沿空留巷开采技术,以河南焦煤能源有限公司古汉山矿1604综放工作面为工程地质背景,采用理论分析和数值模拟相结合的方法,对巷道顶板运动规律进行研究,确定沿空留巷关键参数,并在现场进行工程试验.结果表明:采用定向预裂爆破技术能够阻断巷道上方与采空区上方基本岩层中的应力传递,达到卸压和预裂目的;切顶高度为12.3 m时,可切断下位关键岩层;沿空留巷巷道顶板平均下沉256 mm,采空区帮平均移近214 mm,留巷滞后工作面110 m后围岩开始趋于稳定,能够满足安全生产要求.研究结果可为类似地质条件下的沿空留巷开采提供参考.     

沿空留巷巷旁充填体宽度计算与分析

采用沿空留巷技术是目前解决高瓦斯深井开采难题的关键技术,而充填体是沿空留巷围岩结构的一个重要组成部分,其稳定特性直接影响着巷道整体的稳定性,关系高瓦斯深井开采的成功与否。因此,确定合理的巷旁充填体宽度也成为沿空留巷成功的关键因素之一。本文以谢桥煤矿11426工作面沿空留巷为工程背景,采用理论计算和数值模拟相结合的方法分析了巷旁充填体宽度对巷道围岩受力规律的影响,为今后类似工程提供技术依据。     

上层煤柱下综放沿空回采巷道矿压规律研究

为揭示上层残留煤柱下综放沿空回采巷道矿压显现规律,有效控制围岩变形,根据阳泉一矿8902综放面地质与开采条件,结合现场沿空回采巷道矿压观测结果,应用FLAC3D数值模拟计算分析回采巷道塑性区发育及应力分布情况.研究表明,综放回采巷道在上层残留煤柱影响与本层煤回采引起的应力重新分布耦合作用下,回风巷两帮及顶底移近量高达1985,1877mm,局部断面不足2m2,严重制约了工作面安全高效生产,采取合理布置回采巷道及减小区段煤柱宽度等措施可有效维护巷道.     

A roof model and its application in solid backfilling mining

Through changing the axial load on backfilling material compaction test to reflect different overlying strata pressure on backfilling material, the stress-strain relations in the compaction process of backfilling material under the geological condition can be obtained. Based on the characteristic of overlying strata movement in backfill mining, a model of roof thin plate is established. By introducing the stress-strain relation in compaction process into the model and using RIZT method to analyze the bending deformation of roof, the bending deflection and stress distribution can be obtained. The results show that the maximum roof subsidence and maximum tensile stress occurring at the center are 255 mm and5 MPa, respectively. Tensile fracture of roof under the geological condition of Dongping Mine did not occur. The dynamic measurement results of roof in Dongping Mine verify the theoretical result from the aforementioned model, thereby suggesting the roof mechanical model is reliable. The roof thin plate model based on the compaction characteristic of backfilling material in this study is of importance to research on backfill mining theories and application of backfilling material characteristics.     

长壁工作面顶底板稳定性数值模拟

通过对淮南潘三井田１２２１工作面１３－１煤层顶底板沉积岩体结构的综合分析,同时考虑了沉积岩体在垂向和侧向上不连续的地质特征,概化为３种地质力学模型,应用弹塑性力学有限元方法进行了工作面周围应力分布计算．结果表明：在采动影响下,煤层顶底板岩体中明显地存在着一种对称的双应力拱,由于介质的不连续性导致采动应力场的挠动,局部产生附加应力,在回采过程中将对煤层顶底板的稳定性产生不利的影响．     

骑跨采动压巷道围岩稳定性数值模拟

针对巷道围岩遇水膨胀软化、岩石流变特性显著及长期受采动支撑压力作用的特点,应用FLAC数值软件分析骑跨采动压巷道在不同垂距及水平距离下巷道围岩的稳定性,并研究巷道围岩应力场、变形场及塑性区的变化特征.研究结果表明：巷道围岩变形表现为以底鼓变形最大,两帮变形次之,顶板变形量相对较小的特点;受支撑压力的影响,巷道围岩的应力、变形及塑性区分布呈现明显的不对称性;随着垂距及水平距离的增加,巷道围岩应力及变形呈现出不同程度的减小趋势.     

A coal rib monitoring study in a room-and-pillar retreat mine

The National Institute for Occupational Safety and Health(NIOSH) conducted a comprehensive monitoring program in a room-and-pillar mine located in Southern Virginia. The deformation and the stress change in an instrumented pillar were monitored during the progress of pillar retreat mining at two sites of different geological conditions and depths of cover. The main objectives of the monitoring program were to better understand the stress transfer and load shedding on coal pillars and to quantify the rib deformation due to pillar retreat mining; and to examine the effect of rib geology and overburden depth on coal rib performance. The instrumentation at both sites included pull-out tests to measure the anchorage capacity of rib bolts, load cells mounted on rib bolts to monitor the induced loads in the bolts, borehole pressure cells(BPCs) installed at various depths in the study pillar to measure the change in vertical pressure within the pillar, and roof and rib extensometers installed to quantify the vertical displacement of the roof and the horizontal displacement of the rib that would occur during the retreat mining process.The outcome from the monitoring program provides insight into coal pillar rib support optimization at various depths and geological conditions. Also, this study contributes to the NIOSH rib support database in U.S coal mines and provides essential data for rib support design.     

Effect of faulting on coal burst——A numerical modelling study

Coal burst occurrence on roadways has always been a major concern in deep underground coal mines,especially under complex geological conditions. To evaluate the effect of faulting on coal burst, the stress concentration in the vicinity a reverse fault was analysed considering the geological history of the fault formation where high horizontal stresses led to the initiation and propagation of the reverse fault.Various in situ stresses and mechanical parameters of the fault, including the ratio of horizontal stress to vertical stress were used to analyse the state of fault. Numerical modelling was conducted using two and three dimensional distinct element models(UDEC and 3 DEC) based on a geotechnical conditions of an Australian underground coal mine. The formation process of reverse fault was simulated to evaluate the stress characteristics in the coal seam and the immediate roof and floor near the fault. The results show that, both the horizontal and vertical stress in footwall were higher than those in hanging wall after the formation of the reverse fault. The stress condition near fault was complicated due to complex geology in the coal measures, and the vertical stress peaked in the footwall at a distance of about 160 m from the fault. When a roadway was excavated, stress concentration occurred at both the roadway face and ribs, which reached as high as 38 MPa in the ribs at a depth of 500 m. This will significantly elevate the risk of dynamic instability of the roadway such as coal burst. The stress concentration zone in the footwall can be considered as a hazardous zone near the reverse fault. This study provides a general reference for analysis of roadway stability affected by faults.     

Fixed-length roof cutting with vertical hydraulic fracture based on the stress shadow effect: A case study

Pre-driven longwall retracement roadway (PLRR) is commonly used in large mine shaft. The support crushing disasters occur frequently during the retracement, and roof management is necessary. Taking the 31107 panel as research background, the roof breaking structure of PLRR is analyzed. It is concluded that the roof cutting with vertical hydraulic fracture (HF) at a specified position, that is, fixed-length roof cutting, can reduce support load and keep immediate roof intact. The extended finite element method (XFEM) is applied to simulate hydraulic fracturing. The results show that both the axial and transverse hydraulic fracturing cannot effectively create vertical HFs. Therefore, a novel construction method of vertical HF based on the stress shadow effect (SSE) is proposed. The stress reversal region and HF orientation caused by the prefabricated hydraulic fracture (PF) are verified in simulation. The sub-vertical HFs are obtained between two PFs, the vertical extension range of which is much larger than that of directional hydraulic fracturing. The new construction method was used to determine the field plan for fixed-length roof cutting. The roof formed a stable suspended structure and deformation of the main PLRR was improved after hydraulic fracturing.     

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.     

Assessing support alternatives for longwall gateroads subject to changing stress

Longwall gateroad entries are subject to changing horizontal and vertical stress induced by redistribution of loads around the extracted panel. The stress changes can result in significant deformation of the entries that may include roof sag, rib dilation, and floor heave. Mine operators install different types of supports to control the ground response and maintain safe access and ventilation of the longwall face. This paper describes recent research aimed at quantifying the effect of longwall-induced stress changes on ground stability and using the information to assess support alternatives. The research included monitoring of ground and support interaction at several operating longwall mines in the U.S., analysis and calibration of numerical models that adequately represent the bedded rock mass, and observation of the support systems and their response to changes in stress. The models were then used to investigate the impact of geology and stress conditions on ground deformation and support response for various depths of cover and geologic scenarios. The research results were summarized in two regression equations that can be used to estimate the likely roof deformation and height of roof yield due to longwall-induced stress changes. This information is then used to assess the ability of support systems to maintain the stability of the roof. The application of the method is demonstrated with a retrospective analysis of the support performance at an operating longwall mine that experienced a headgate roof fall. The method is shown to produce realistic estimates of gateroad entry stability and support performance, allowing alternative support systems to be assessed during the design and planning stage of longwall operations.     

Analysis of monitored ground support and rock mass response in a longwall tailgate entry

A comprehensive monitoring program was conducted to measure the rock mass displacements, support response, and stress changes at a longwall tailgate entry in West Virginia.Monitoring was initiated a few days after development of the gateroad entries and continued during passage of the longwall panels on both sides of the entry.Monitoring included overcore stress measurements of the initial stress within the rock mass, changes in cable bolt loading, standing support pressure, roof deformation, rib deformation,stress changes in the coal pillar, and changes in the full three-dimensional stress tensor within the rock mass at six locations around the monitoring site.During the passage of the first longwall, stress measurements in the rock and coal detected minor changes in loading while minor changes were detected in roof deformation.As a result of the relatively favorable stress and geological conditions, the support systems did not experience severe loading or rock deformation until the second panel approached within 10–15 m of the instrumented locations.After reaching the peak loading at about 50–75 mm of roof sag, the cable bolts started to unload, and load was transferred to the standing supports.The standing support system was able to maintain an adequate opening inby the shields to provide ventilation to the first crosscut inby the face, as designed.The results were used to calibrate modeled cable bolt response to field data, and to validate numerical modeling procedures that have been developed to evaluate entry support systems.It is concluded that the support system was more than adequate to control the roof of the tailgate up to the longwall face location.The monitoring results have provided valuable data for the development and validation of support design strategies for longwall tailgate entries.