Deformation mechanism of surrounding rocks and key control technology for a roadway driven along goaf in fully mechanized top-coal caving face

The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward.

Study of mechanical principle of floor heave of roadway driving along next goaf in fully mechanized sub-level caving face

Abstract On the basis of analyzing floor strata mechanical circumstance of the roadway, the mechanical model was established. The relative displacement of roadway floor, narrow pillar floor coal mass and floor strata was calculated, the results showed that the high abutment pressure on coal mass beside the roadway was the main reason to lead to relative displacement of floor strata. And the roadway floor heave come mainly from three aspects. Firstly, the roadway floor strata is easily fractured by the stretch stress. Secondly, because the high abutment pressure is greater than the uniaxial compressive strength of floor strata, when the roadway floor strata are fractured, the coal mass floor strata at the same depth will be fractured, and broken rock will fluid into the open roadway. Thirdly, comparing with the coal mass floor, the roadway floor is relative ascending.

Stability Control of Gob-Side Entry Retaining in Fully Mechanized Caving Face Based on a Compatible Deformation Model

The stability control of gob-side entry retaining in fully mechanized caving face is a typical challenge in many coal mines in China.The rotation and subsidence of the lateral cantilever play a critical role in a coal mine,possibly leading to instability in a coal seam wall or a gob-side wall due to its excessive rotation subsidence.Hence,the presplitting blasting measures in the roof was implemented to cut down the lower main roof and convert it to caved immediate roof strata,which can significantly reduce the rotation space for the lateral cantilever and effectively control its rotation.Firstly,the compatible deformation model was established to investigate the quantitative relationship between the deformation of the coal seam wall and the gob-side wall and the subsidence of the lateral cantilever.Then,the instability judgments for the coal seam wall and gob-side wall were revealed,and the determination method for the optimal roof cutting height were obtained.Furthermore,The Universal Distinct Element Code numerical simulation was adopted to investigate the effect of roof-cutting height on the stability of the retained entry.The numerical simulation results indicated that the deformation of the roadway could be effectively controlled when the roofcutting height reached to 18 m,which verified the theoretical deduction well.Finally,a field application was performed at the No.3307 haulage gateway in the Tangan coal mine,Ltd.,Shanxi Province,China.The field monitoring results showed that the blasting roof cutting method could effectively control the large deformation of surrounding rocks,which provided helpful references for coal mine safety production under similar conditions.

Statistic constitutive equation of top-coal damage for fully mechanized coal face with sublevel caving

Under the action of abutment pressure in front of fully mechanized coal face with sublevel caving(CFSC),top-coal over CFSC deformed.In the process of whole de- formation of top-coal,it changed from continuum elastic mass to non-continuum plastic mass contained fissures,become a loose body.According to its bearing characteristics and mechanical properties,top-coal mass can be divided into four deformation zones along the winning direction of CFSC,i.e.initial stress zone,elastic zone,plastic zone and loose zone.Top-coal in plastic zone located in the post-peak zone of the stress-strain curve for top-coal.With equivalent strain principle of damage mechanics and mathemati- cal theory of statistic,combining the movement law of top-coal,set up a constitutive equa- tion with damage statistics for top-coal in different position in CFSC.The equation illus- trated the mathematical relationship among top-coal bearing capacity,horizontal confining pressure along the winning direction of CFSC and mechanical properties of top-coal mate- rial.The conclusions not only provide a basis for numerical computer simulations on damage deformation and failure mechanism for top-coal,but also further promote the ap- plication of damage mechanics in CFSC.

Similar material simulation research on movement law of roof over-lying strata in stope of fully mechanized caving face with large mining height

Similar material simulation test W9-15 101 fully mechanized caving face with was carried out in a geological model of large mining height in the Liuhuanggou Colliery, in Xinjiang Uigur Autonomous Region. The roof overlying strata movement law in the stope of a fully mechanized caving face with large mining height was studied and show that the roof overlying strata in the stope of a fully mechanized caving face with large mining height can be formed into a stable arch structure; the fracture rock beam is formed resembling a ＂bond beam＂, but it has essentially the structure of ＂multi-span beams＂ under the big structure of the stable arch. The roof overlying strata movement law in the stope of a fully mechanized caving face with large mining height is similar to that of the common, fully mechanized caving stope, which is determined by the deformation and instability of the structure of ＂multi-span beams＂. But because of the differences between the mining heights, the peak pressure in the stope of a fully mechanized caving face with large mining height is smaller while the affected area of abutment pressure is wider in the front of the working face; this is the obvious difference in abutment pressure between the stope of a fully mechanized caving face with large mining height and that of the common.

Distribution laws of abutment pressure around fully mechanized top-coal caving face by in-situ measurement

In order to obtain the distribution rules of abutment pressure around the 1151 （3） fully mechanized top-coal caving （FMTC） face of Xieqiao Colliery, the KSE-II-1 type bore-hole stress gauges were installed in the tailentry and headentry to measure the mining-induced stress. The distribution rules of the front and side abutment pressure were demonstrated. The results show that distribution rules of stress are obviously different in the vicinity of the face and entries. The peak value of abutment pressure in the protective coal pillar and face are located commonly in front of the working face along the strike, and they are located at the stress-decreased zone near the face. There is no stress peak value in the lateral coal mass beside the headentry in front of the face on the strike, and the peak value of abutment pressure appears at the rear area of the face. There are stress peak values both in the protective coal pillar and in the lateral coal mass beside the headentry to the dip.

Reliability analysis of the velocity matching of coal cutting and caving in fully mechanized top-coal caving face

The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.

Back-and-forth mining for hard and thick coal seams—research about the mining technology for fully mechanized caving working face of Datong Mine

The article introduced the key technology, mining process, and back-and-forth mining method for the caving working face of hard-thick coal seams in Datong mine, and researched this innovations process, optimized the systemic design and working face out-play, tried to perfect the caving mining technology of hard-thick coal seams further.

Analysis and key control technologies to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines

In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China, we have analyzed the characteristics of spontaneous coal combustion and explain theoretically the factors affecting spontaneous coal combustion, such as rock bursts, high temperatures, high ventilation resistance, slow advancing speed and large obliquity mining. Key technologies to prevent spontaneous combustion occurring in sharply inclined seams in deep mines are pro- posed; these include pouring water, stopping leakage in upper and lower comers of the working face, choking off the goaf and cov- eting the coal. CO concentrations were controlled within two years to less than 15×10^-6 at the upper comer by applying these tech- nologies at the 1410 working face of the Huafeng coal mine. Our method has significant theoretical value and is of practical impor- tance in controlling spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines.

Technological optimization of fully mechanized caving mining face with large mining heights

Fully mechanized cave mining with large mining height is a new mining method, due to its large mining thickness and lower roadway excavation, the technology has been widely used in China＇s thick seam mining. In order to improve the top-coal recovery ratio of fully mechanized cave mining with large mining height, a study was conducted on optimizing the caving process, based on the mechanized caving face 1302N in Longgu Coal Mine. This was achieved by improving the PFC numerical calculation methods, and establishing a more accurate model system. On this basis, the recovery ratio of the top coal in different drawing intervals and technologies was investigated in order to achieve a reasonable caving process. The top-coal tracking system was used for practical surveying of the recovery ratio of top coal.

Numerical simulation on the delivery law of gob gas of fully mechanized caving face

According to the cover rock caving features,the gob of fully mechanized caving face was divided into 3 zones: natural collected zone,pressure effecting zone and press stable zone.Based on these and the gob gas flow control equation,and considered the in- fluence to the mining fissured zone of gas drainage,also made use of CFD software,we found an not uniform 3D numerical model of gob gas seepage and got the gas emission law in gob of fully mechanized caving face (with or without discharge measures),and this can guide the engineering practice in some aspects.

STUDY ON PRODUCTION SYSTEM OPERATION REGULARITY OF FULLY MECHANIZED SUBLEVEL CAVING MINING AND SEQUENTIAL OPERATION

According to a lot of practical data in Liujialiang Mine and reliability theory and result of computer simulation, operation regularity of fully mechanized sublevel caving mining production system in the condition of gently inclined complicated geological structure and production shortcomings are found out and reliability of system and output of the working face are predicted finally.

Investigation on the stress field characteristic of top coal at FMTC faces under the influence of caving thickness

In the background of the technology condition and the geological condition of the 1151（3） fully mechanized top-coal caving face （FMTC face）, and by means of taking nonlinear 3D numerical simulation, the stress redistribution rules of top coal with different thick coal seam were obtained by investigation on the numerical simulation of the redistributions of the stress with different coal seam＇s thickness. The research showes that there exists a certain difference on the stress distributions of the top coal at face, the maximum principal stress is located near to the tailentry＇s corner. The vertical stress＇s peak of the top coal decreases and the distance ahead of face position increases as the once mining thickness of the coal seam increases. At the same coal seam, the vertical stresses＇ peak of top coal gradually decreases from the top to the bottom, the peak＇s position is basically the same and its changes are gradually obvious with the thickness of coal seam increas- ing. The vertical stress of top coal places in a low stress state at a certain range ahead of face and over the face, which reveals the essence that the support loads are generally low under the condition of FMTC. The study supplies the theoretical foundation for the support design and selection, the theory of top coal＇s fragmentation, the movement rules of top coal and improving the recovery of top coal.

综放工作面过空巷时支架-围岩稳定性控制

通过分析综放工作面过空巷时支架-围岩稳定性控制的技术难点,提出在过空巷合理的时空节点上实施停采等压、强力锚杆索支护、注浆固结修复和支架支撑力保障的综合控制技术,并阐述了相应的控制机理。建立了综放工作面过空巷时基本顶破断的结构模型,分析得出过空巷时长关键块条件下的支架临界工作阻力;采用数值模拟方法分析综放工作面过空巷时采动影响下围岩应力分布、变形与破坏特征,确定综合控制技术实施的时空节点与相关参数,进而结合现场地质生产条件与矿压规律确定相应技术方案,并进行现场应用。现场实践表明,采用综合控制技术后,未发生大范围冒顶、支架压架等恶性支架-围岩事故,解决了9102综放工作面过空巷的相关技术难题。

“高位-低位”厚硬岩层综放面特厚煤层矿压显现特征研究

基于大同煤田马道头矿井为工程背景,建立了“高位-低位”厚硬岩层综放面物理相似模型,分析了特厚煤层综放面覆岩移动特征,监测了8404工作面矿压显现特征。研究结果表明:工作面推进80、110、155 m时,基本顶、上方中砂岩(低位岩层)、上方粗砂岩(高位岩层)依次发生初次垮落;工作面平均周期来压步距为14.11~16.19 m;支架最大工作阻力基本上低于额定工作阻力的55%;工作面第1次大周期来压步距为140 m,来压可持续10~20 m,动载系数为2.24~2.38;工作面ZF17000/27.5/42D型液压支架未出现压架、立柱收缩等现象,支架选型适用性良好。

综放工作面顶板运动规律及支架-围岩关系研究

布尔台煤矿42103综放工作面回采过程中,经常出现台阶下沉甚至支架压死等现象,在对42103综放工作面支架合理工作阻力进行分析的基础上,采用理论推导和现场实测相结合的研究方法对工作面顶板运动规律进行计算,建立了42103综放工作面顶板结构模型,并分析支架-围岩的相互关系,利用顶板结构模型法和动载系数法综合计算确定了42103综放工作面支架合理工作阻力。研究结果表明:42103综放工作面顶板压力为1.63 MPa,支架合理工作阻力为18 709 k N,支架合理支护强度为1.71 MPa。

综采工作面上覆岩层垮落高度T-S模糊预测模型研究

通过分析影响综采工作面上覆岩层垮落高度的主要因素,借助层次分析法确定垮落高度"低、中、高"3种典型情况的因素权重,结合各种因素论域的模糊划分得到T-S模糊系统,建立了一种新的综采工作面上覆岩层垮落高度T-S模糊预测模型。利用该模型分别对镇城底矿、王庄矿、杜儿坪矿综采工作面上覆岩层垮落高度进行了计算,结果为16.463 3、18.688 7、16.463 7 m,相对误差分别为0.88%、3.42%、8.31%,表明该预测模型具有较高的精度。

大采高坚硬顶板综放面“注-爆”一体卸压防冲技术

针对千米深井综放工作面采场应力大、地质力学环境复杂、受开采扰动作用强、易诱发冲击地压等问题,分析了工作面冲击地压诱发及控制机理,提出了煤层注水+基本顶预裂爆破的“注-爆”一体化卸压防冲技术。通过对比不同注水孔及爆破孔布置间距条件下,采场超前支承压力分布特征、弹性应变能释放规律等,确定了大采高综放工作面注水及爆破钻孔的最优布置间距,在有效降低工作面冲击倾向的同时实现了较好的经济效益。

泉店煤矿二_1-12050综放工作面延面技术及实践

泉店煤矿二1-12050综放工作面地质条件复杂,回采过程中,随着工作面的推进,工作面长度逐渐增加,由设计时的153 m延长至159 m,增加了机尾空顶面积。为保证正常推进,工作面机尾处需延设输送机和支架。通过现场研究与分析,确定了待安装支架的数量与位置,达到了科学、快速、合理延长工作面的效果,提高了综放工作面的机械化生产能力和煤炭资源采出率。

FR-1阻化泡沫防灭火技术研究

针对综放孤岛工作面采空区漏风引起浮煤自燃的问题,以天池矿102综放孤岛工作面的应用为例,采用热重实验和热解动力学分析法进行FR-1阻化泡沫防灭火技术研究。对102工作面的煤样在阻化前后进行热重实验,通过热解动力学分析发现,阻化后进、回风巷煤样失水阶段的活化能分别增加了1.63倍和3.21倍;氧化增重阶段活化能分别增加了1.53倍和1.43倍,燃烧阶段活化能降低。现场应用发现,FR-1阻化泡沫具有良好的渗透性和堆积性,采空区的CO浓度不断下降并最终降到0ppm。研究结果表明,FR-1阻化泡沫能有效提高煤的失水活化能,具有良好的阻燃作用,能有效防止综放孤岛工作面的采空区自燃。