A Study on Dual-Load-Zone Model of Overlying Strata and Evolution Law of Mining Stress

The changeable structure and movement law of overlying strata are the main contributor to the change of mining stress. Starting from the relevant theory of key stratum and particularly based on the theory of mine ground pressure and strata control, this research proposed a new solution to mining stress problems by establishing a dual-load-zone stratum structural model. Elastic foundation beam theory was used to solve the stress of overlying strata of the dual-load-zones with superposition method, which revised the traditional calculation method of mining stress. The abnormal increase of lead abutment pressure in the mining area was explained effectively, through which the evolution law of mining stress in the case of hard rock was obtained. The results indicate that mining stress experiences a drastic change within the range of 50 m ahead of the coal wall due to the collapse of main roof; under the influence of main key stratum and inferior key strata, the influence range of lead abutment pressure is extended up to approximately 120 m in the working face; this remarkable increase can be attributed to the excessive length of sagging zone. Results from both the dual-load-zone model experiment and field measurement demonstrate high consistency. The model can predict the influence range of abutment pressure effectively and thus guide the safety production of mining.     

Fracture failure analysis of hard–thick sandstone roof and its controlling effect on gas emission in underground ultra-thick coal extraction

In underground coal extraction of fully mechanized caving, the overlying hard–thick sandstone main roof could control the failure extent and the movement evolution of the entire overburden strata. The instantaneous failure of the hard–thick sandstone main roof possibly causes strata pressure behaviors, rock-bursts and abnormal gas emissions, which may result in equipment damages and casualties. Tashan coalmine was chosen as a field case study base because of its super great mining height (SGMH) and the overlying hard–thick sandstone roof (HTSR). This mine has experienced a great deal of damaging hydraulic support and abnormal gas emission accidents caused by strata pressure behavior. The fracture failure analysis was analyzed based on “Key Strata Theory” and numerical simulation results. The hard–thick sandstone main roof could perform as a very large double-sided embedded rock beam in the primary fracture and as a cantilever-articulated rock beam in periodic fracture, simultaneously generates a huge hanging space in the gob. The fracture failure of the hard–thick sandstone main roof causes a permeability enhancement in the adjacent rock-coal strata and near face coal seam. The substantial amounts of gas stored in the remaining coal, surrounding rock strata and adjacent coal seams rush out and aggregate in the caved and fissure zone of the gob, thereby forming a huge gas cloud. The disasters due to coupled strata pressure behavior and abnormal gas emissions, which primarily occurred after primary and periodic fracture failure, are predominantly caused by the instantly fracture of main roof. When the main roof reached the ultimate broken span and underwent, rotation and collapse, substantial amounts of gas accumulating in the gob escaped to the working face under the extrusion and impaction of the caving rock strata, which easily produced abnormal gas emissions, some of which exceeded the statutory limit. Shortening the length of the HTSR failure span using hydraulic presplitting and decreasing the gas content of the coal seam using gas drainage technology are recognized as two effective approaches to solve this issue.     

Analysis of gas-dynamic phenomenon in underground coal mines in the central basin of Asturias (Spain)

This paper aims to analyse and understand the origin and development of gas-dynamic phenomenon (GDP) that take place with certain regularity in underground coal mining. It provides a detailed analysis of how they are influenced by changes and increases in ground stresses (vertical and horizontal stresses) and variations in the pressure of methane gas contained in underground coal seams used for mining operations.Phenomenon of this nature have occurred in recent years in certain seams at the Sotón, Montsacro and San Nicolás pits in the central coal basin of Asturias (Spain). Describing and analysing them reveals the influence of the proximity of other operations at different levels of the same seam or located in different seams. Similarly, it indicates the influence of unmined zones and brusque changes in the thickness of the seam. The values of the concentration of gas at the coal face of the mined seam and its rate of desorption complement and justify all the previous explanations. The measurements taken were periodically obtained by means of boreholes in coal faces for coal seams mined using the sub-level method.     

低透气性煤层松动爆破增透效应研究

松动爆破是防治瓦斯突出的有效措施。针对煤层透气性差,突出危险预测指标高的问题,采用松动爆破技术对煤层进行卸压增透。结合某矿工作面煤体和爆破参数,理论计算了爆破后裂隙圈范围,主要包括应力波作用和静压破坏作用两部分,分别为0.41 m和1.47 m;通过布置钻孔并观测瓦斯流量变化,裂隙圈范围与理论计算较为接近,略小于应力波和静压破坏两部分理论计算之和;在理论计算和现场观测的基础上,确定合理的钻孔间距为3 m。采煤工作面经卸压爆破后,突出预测指标S(钻屑量)和q(瓦斯涌出初速度)分别下降了16.7%和57.1%,有效降低了工作面突出危险性。     

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.     

Demonstration Project of Safe and Efficient Mining Operations in Extra-thick Coal Seam

Mineable coal reserves in thick and extra-thick seams account for 44% of the total deposit in China. Fully-mechanized top-coal caving technology is a new mining method of safe and efficient underground operations in extra-thick seams in China. The development of fully-mechanized top-coal caving technology in China, which was successfully applied in Face 8105 in Tashan Coal Mine, Datong, Shanxi, China, is analyzed in this paper. Studies on movement pattern of top-coal and roof from fully-mechanized top caving face in 14–20 m extra-thick seams have been carried out. A series of key technologies were successfully developed, including strata control technology, equipment for high-efficient and high-recovery top caving operations, and safety guarantee technology for low gas occurrence and high gas emission. As a result, the fully-mechanized top-coal caving Face 8105, with large mining height in Tashan Coal Mine, has achieved a recovery rate of 88.9% and an average equipment operation rate of 92.1%. With coal production of 10.84 Mt in 2011, the demonstration project is a technology and equipment breakthrough for fully-mechanized top-coal caving face in extra-thick coal seams with large mining height.     

The mechanism of bedding separation in roof strata overlying a roadway within a thick coal seam: A case study from the Pingshuo Coalfield,China

Bedding separation in roof strata (BSRS) overlying roadways within thick coal seams (RTCS) is an important factor leading to surrounding instability in underground coal mines, and especially to roof failures such as convergence, and even caving-in. To prevent reason, and to protect the working miners, it is essential to understand the mechanism of underpinning BSRS overlying RTCS. In this research, combined with the theoretical analysis and test results of continuous, and discontinuous, beams and stratified rock strata load, a new approach to predict the locations at which BSRS occurred was proposed; additionally, the calculation equation for BSRS was deduced. Based on standard monitoring methods widely used in exploring roof behaviour in underground coal roadways, a typical roadway excavated within 12.87 m, in an average thickness coal seam, in Jinggonger coal mine, Pingshuo Coalfield, Shanxi Province, China, that was chosen to explore the mechanism underpinning BSRS, and a set of monitoring designs, mainly including five groups of stations and 16 instruments, is determined and applied to this research. Results showed that the predicted locations of BSRS overlying RTCS were in accordance with field monitoring results. This proved the validity of the theoretical model. Besides, the working face played an important role in BSRS and 75% of the BSRS events were generated within the 50 m between the monitoring station and the working face. When the distance was decreased to 5 m, the BSRS was up to 90.9 mm and 86 mm at depths of 6.8 m and 3.8 m, respectively. Meanwhile, three stages were considered, step-by-step, as opposed to mining activity dependent upon the extent of its influence on BSRS: a pink value (indicative of an alarm status) prevailed during the third stage.     

煤矿深孔预裂爆破技术应用研究

为解决较厚坚硬煤层的瓦斯突出和回采率低的问题,采用深孔预裂爆破的方法增加其透气性,并利用煤层松动产生的局部应力突变增加落煤量。根据爆破理论计算了爆破参数,确定了爆炸作用的裂隙范围。实践表明,煤层瓦斯含量降低,提高了回采率,试验与理论基本一致。     

Research on damage distribution and permeability distribution of coal seam with slotted borehole

In order to study the effect of high pressure water jet cutting technology on the permeability of single coal seam, we use the damage variable to describe the fracture distribution of coal seam, develop the 3-D finite element program based on the damage theory, and then analyze the damage distribution of coal seam after drilling and slotting. Using MTS815 rock mechanics testing system and the permeability test system, we conduct the permeability test and get the relationship between permeability and damage. Based on the damage distribution of coal seam after drilling and slotting and the permeability change law, we analyze the permeability distribution of coal seam after drilling and slotting. The results show that: after slotting high damage appears in the coal seam around the slot, which is advantageous for gas flow and expands the effect range of the drill. The slot width has little effect on the permeability of coal seam while the slot height has the obvious effect on permeability of coal seam. It is necessary to expand the slot height for increasing the effect range of the drill.     

基于Winkler地基理论的横向受荷长桩非线性动力响应模型试验

基于Winkler模型,将弹性地基离散化为线性弹簧,建立长桩-弹簧动力相互作用模型试验系统,研究了桩顶横向简谐激励下桩基的非线性动力响应.通过两组共12种工况模型试验,分析了桩身参数、地基约束、桩顶配重和激励特征等对桩基动力响应幅值、共振和空间运动的影响.试验结果表明:随激励幅值增大,桩基动力响应的非线性特征显著;在特...     

软土深基坑围护结构变形的三维有限元分析

本文基于考虑横向剪切变形的Ｍｉｎｄｌｉｎ厚板理论,建立了深基坑围护结构变形的三维 有限元分析模型,并编制了相应的计算程序。该模型能模拟地基的流变性态、支撑方式的变 化、板－土之间的接触摩擦以及基坑分步开挖过程,可按墙体位移的变化自动修正土压力。 计算实例表明,本文建立的三维有限元分析模型可考虑围护墙体位移因基坑开挖而引起的空 间效应以及由地基流变而引起的时间效应,可以计算墙体任意时刻任意位置的变形,是一种 简便而又实用的三维分析方法。     

“三硬”煤层冲击矿压的微震信号特征分析

为研究顶板、底板和煤层相对较硬的"三硬"煤层工作面微震活动规律,以忻州窑煤矿微震监测系统为工程背景,针对震源分布特征、微震能量及频次与采动的关系、典型冲击矿压微震信号特性分析等方面进行研究,揭示工作面微震活动总体规律,特别是冲击矿压前兆的微震效应,为建立"三硬"冲击矿压微震预测技术、评价矿井冲击矿压提供依据,具有一定理论意义与实用价值。     

Experimental study on spontaneous imbibition characteristics of coal based on fractal theory

Coal seam water injection is a widely used dust reduction technology in Chinese coal mines. During the process of coal seam water injection, a large amount of broken coal particles will accumulate in the pore, which will affect the flow characteristics of water. It's very important for improving the on-site coal seam water injection and dust reduction technology to study the influence of coal particles on the water migration law. In this paper, a spontaneous upward imbibition experiment was used to study the effect of coal particles stacked in front fractures on water migration in coal seam water infusion. Then, a mathematical model was established to express imbibition speed and stable imbibition height. The results show when the largest particle size is selected, theoretical calculation results of stable imbibition height is closest to the experimental data; coal particles with a size of 564–1589 μm have the greatest influence on the wetting phase of coal seam water infusion; the metamorphic grade and particle size of the samples mainly affect the initial stage of water migration, and the initial imbibition speed of each coal sample is quite different. However, with increasing imbibition height, the imbibition speed difference of each coal sample gradually decreases.     

水力割缝本煤层抽采煤层气应力场数值模拟

我国浅部煤炭资源逐渐开采枯竭，很多煤矿相继进入深部开采作业阶段。针对平顶山十矿深部煤层处在高地应力和高孔隙压力下实际情况，基于ANSYS有限元分析软件对水力割缝技术本煤层卸压抽采煤层气进行了数值模拟研究。分析了水力割缝技术与破煤机理，建立了水力割缝开采深部煤层气平面应变有限元模型，得到了钻井前后、水力割缝前后有限元模型的地应力场变化规律及其影响范围。数值模拟结果表明，水力割缝技术可达到使近井地带充分卸压的目的，应用水力割缝在深部煤层气开采中卸压效果明显。     

巷道爆破掘进中侧压系数对薄层复合顶板影响的数值分析

为分析侧压系数在巷道爆破掘进时对薄层复合顶板的影响,针对东荣二矿17#煤顶底板地质条件建立相应数值计算模型,采用非线性有限元动力分析软件ANSYS/LS-DYNA分析了巷道爆破掘进中在不同侧压系数条件下对薄层复合顶板的影响。分析结果表明:不同侧压系数对薄层复合顶板不同区域影响效果不同,爆炸对顶板的冲击压力影响较大,而对顶板的振速影响较小。随着侧压系数的增大,在掘进工作面后方,爆炸初期顶板压力减小,而中、后期压力逐渐增大;在掘进工作面的前方,爆炸初期、后期顶板压力逐渐增大,而中期压力逐渐减小。因此,巷道爆破掘进时,在工作面后方应及时支护,提高顶板的强度,以减小爆破对后方顶板离层的加速作用;同时应优化爆破参数,以降低爆破对前方顶板的损伤作用,以防掘进过程中发生冒顶事故。     

巷道爆破掘进中侧压系数对薄层复合顶板影响的数值分析

为分析侧压系数在巷道爆破掘进时对薄层复合顶板的影响,针对东荣二矿17#煤顶底板地质条件建立相应数值计算模型,采用非线性有限元动力分析软件ANSYS/LS-DYNA分析了巷道爆破掘进中在不同侧压系数条件下对薄层复合顶板的影响.分析结果表明:不同侧压系数对薄层复合顶板不同区域影响效果不同,爆炸对顶板的冲击压力影响较大,而对...     

通过预涂覆SiC优化AZ31B镁合金DE-GMAW焊缝的显微组织及提升力学性能

研究了碳化硅(SiC)颗粒涂覆量对2mm厚AZ31B镁合金双电极气体保护焊DE-GMAW焊缝的宏观形貌、显微组织和力学性能的影响。利用光学显微镜、扫描电镜和X射线衍射分析技术(XRD)对接头的显微组织、相及相的成分进行分析。同时采用维氏硬度试验计和万能试验机对焊接接头的显微硬度和抗拉强度分别进行测量。结果表明,随着SiC涂覆量的增加,焊接接头熔深和深宽比先增大后减小。XRD测试结果显示,SiC的添加并不改变焊缝中相的组成,焊缝由α-Mg和β-Mg_(17)Al_(12)组成。SiC可以细化α-Mg晶粒,打断焊缝中β-Mg_(17)Al_(12)相,起到弥散强化的效果。但SiC涂覆量达到一定值后,随着SiC涂覆量的继续增加,α-Mg晶粒粗化,β-Mg_(17)Al_(12)相的弥散强化作用不再增加。焊接接头的显微硬度和抗拉强度随着SiC涂覆量的增加先增大后减小。     

山西沁水盆地柿庄北区块3#煤层注入埋藏CO2提高煤层气采收率试验和评价

对沁水盆地南部柿庄北区块进行了深煤层注入地质和工程评价,认为柿庄北区块适合进行深煤层注入CO2开采煤层气技术的应用;通过SX-001井的微型先导性试验,对SX-001井的注入前后产气量与产水量、气体成分变化和井底压力变化规律进行了总结。通过现场试验,注入CO2后SX-001井的产气量是注入前的2.45倍;在小于煤岩破裂压力的条件下,每天注入20 t的CO2能够实现顺利注入,并且压力上升速度较慢;注入CO2后,煤岩发生膨胀,局部煤层的渗透率降低,排采一段时间后恢复;在目的煤层中注入的CO2的影响范围内,烃类气体总的置换效率达到14.18 cm3/g。该试验成果证明柿庄北区块通过注入CO2开采煤层气实现了CO2的埋藏,提高了煤层气井的采收率。     

The Recent Technological Development of Intelligent Mining in China

In the last five years, China has seen the technological development of intelligent mining and the application of the longwall automation technology developed by the Longwall Automation Steering Committee. This paper summarizes this great achievement, which occurred during the 12th Five-Year Plan (2011–2015), and which included the development of a set of intelligent equipment for hydraulic-powered supports, information transfers, dynamic decision-making, performance coordination, and the achievement of a high level of reliability despite difficult conditions. Within China, the intelligent system of a set of hydraulic-powered supports was completed, with our own intellectual property rights. An intelligent mining model was developed that permitted unmanned operation and single-person inspection on the work face. With these technologies, the number of miners on the work face can now be significantly reduced. Miners are only required to monitor mining machines on the roadway or at the surface control center, since intelligent mining can be applied to extract middle-thick or thick coal seams. As a result, miners’ safety has been improved. Finally, this paper discusses the prospects and challenges of intelligent mining over the next ten years.     

薄煤层采煤机振动特性研究

为研究复杂煤层赋存条件下薄煤层采煤机的振动特性,根据多体拓扑结构建立采煤机刚柔耦合模型,通过仿真得到采煤机在截割含夹矸韧性煤工况下前后滚筒受到冲击载荷作用时的动态特性。基于子结构模态综合方式(CMS)的振动疲劳分析方法,进行危险点动应力与模态振动的相关性分析,发现牵引部壳体在实际工作过程中产生具有3阶垂向弯曲模态特征的弹性振动;以不同测试点加速度频域响应为依据,分析采煤机振动对其电控系统以及液压系统的影响,判断测试点加速度与模态振动的相关性,同时确定出牵引部柔性壳体的高动应力区域及其结构疲劳性质。分析结果为薄煤层采煤机的优化设计、后续测试、安全性评价提供了重要的参考。