Numerical analysis of application for induction caving roof

New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the stress is released with the mining process. And applying the catastrophe theory, the influencing factors of induction caving roof are studied in the emptied areas, such as the mechanical property of the surrounding rock, the area of the gob,the scope and dimension of tensile stress. The results show that the key factor is the area of the gob to the method of the induction caving roof. Then according to the geology and the ore characteristic, the three dimension FEM mechanical model is built in Tongkeng Mine, the laws of the tensile stress are analyzed to the space and the time in the roof with the mining, then it is rational design to the mine step and time of the handing the roof.     

Top coal flows in an excavation disturbed zone of high section top coal caving of an extremely steep and thick seam

Compared with gentle dip long-wall caving, the length of a working face in fully-mechanized top-coal caving for extremely steep and thick seams is short, while its horizontal section is high with increasing production. But the caving ratio is low, which might result in some disasters, such as roof falls, induced by local and large area collapse of the top coal in a working face and dangers induced by gas accumulation. After the development of cracks and weakening of the coal body, the tall, broken section of the top coal (a granular medium) of an extremely steep seam (over 60°) shows clear characteristics of nonlinear movement, We have thoroughly analyzed the geological environment and mining conditions of an excavation disturbed zone. Based on the results from a physical experiment of large-scale 3D modeling and coupling simulation of top coal-water-gas, we conclude that the weakened top coal can be regarded as a non-continuous medium. We used a particle flow code program to compare and analyze migration processes and the movements of a 30 m high section top coal over time before and after weakening of an extremely steep seam in the Weihuliang coal mine. The results of our simulation,experiment and monitoring show that pre-injection of water and pre-splitting blasting improve caving ability and symmetrical caving, relieve space for large area dynamic collapse of top coal, prolong migration time of noxious gases and release them from the mined out area and so achieve safety in mining.     

回采工作面放顶煤数学模型的建立

通过相似模拟实验研究,本文针对煤矿放顶煤回采工作面特点,提出了对放煤效果影响最大的三个主要因素:煤层垮落角(α)、放煤高度(h)及放煤口到煤断线水平距离(l_0)。并发现,在放煤过程中,由于受α、h、l_0值影响,放出体非但不是一个完整椭球体,而且放出体轴线也要发生偏转。在此基础上建立了煤矿放顶煤的数学模型,为放顶煤回采工艺建立了必要的理论基础。     

Numerical analysis of application for induction caving roof

New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the stress is released with the mining process. And applying the catastrophe theory, the influencing factors of induction caving roof are studied in the emptied areas, such as the mechanical property of the surrounding rock, the area of the gob, the scope and dimension of tensile stress. The results show that the key factor is the area of the gob to the method of the induction caving roof. Then according to the geology and the ore characteristic, the three dimension FEM mechanical model is built in Tongkeng Mine, the laws of the tensile stress are analyzed to the space and the time in the roof with the mining, then it is rational design to the mine step and time of the handing the roof. Foundation item: Project(50490274) supported by the National Nature Science Foundation of China     

康家湾永久防水矿柱安全开采可行性

康家湾矿是典型的大型水体下矿床,开采技术条件极其复杂,而留设大量永久防水矿柱,造成资源积压．分析了矿区内主要构造对顶板围岩及含水层影响、顶板与隔水层和相对隔水层位置关系、含水层及勘探钻孔对矿柱回收的影响;计算了冒落带和导水裂隙高度及安全开采深度;用ANSYS有限元软件模拟了空区上覆岩层稳定性及最大允许暴露面积．结果表明,断层不会连通空区与水体,矿柱顶板围岩稳固,与含水层的隔水层和相对隔水层厚度在190m以上;充填未接顶高度应控制在2．0m内,采动后的安全厚度应大于65m;对空区及时、高质量充填有利于永久防水矿柱的回收;理论的采空区极限暴露面积可达3360—4000m^2．因此,在满足以上研究参数条件下,采用充填法对康家湾永久防水矿柱进行回收是完全可行的．     

Strata behavior investigation for high-intensity mining in the water-rich coal seam

This paper describes a specific case of mining in a water-rich coal seam in western China. Water inrushes, roof caving and other disasters induced by intensive mining operation could pose great threats to the safety of coal mines. The strata behavior during the high-intensity extraction in the water-rich coal seam is analyzed by employing the numerical simulation method and in situ monitoring. The results show that about 10 m ahead of the workface, the front abutment pressure peaks is at 34.13 MPa, while the peak of the side abutment pressure is located about 8 m away from the gateway with the value of 12.41 MPa; the height of the fracture zone, the first weighting step and the cycle weighting step are calculated to be 45, 50 and 20.8 m, respectively; pressure distribution in the workface is characterized by that the vertical pressure in the center occurs earlier and is stronger than those on both ends. Then, the results above are verified by in situ measurement, which may provide a basis for safe mining under similar conditions.     

分段落矿阶段矿房采矿法在黄崖洞铁矿应用的可行性

针对黄崖洞铁矿现用采矿法-浅孔留矿法使用过程中存在的问题,提出了改变采矿方法的必要性：着重从安全、技术方面分析了分段落矿阶段矿房采矿法对本矿区矿床开采的适应性和可行性．同时也能满足提高矿山生产能力的要求：从作出的标准矿块单体设计方案中可以看出,与浅孔留矿法相比分段落矿阶段矿房采矿法有许多优越之处。     

两硬综放面矿压显现规律研究

根据忻州窑矿８９１６综放面的矿压观测，系统地分析了两硬条件下综放开采的矿压显现规律。文章的结论是：两硬条件下的综放面既具有坚硬顶板带冲击载荷的悬梁式破断规律，又具有综放开采的动载系数小，支架载荷低的显现特征，采场控制仍要有高强度的支撑和必要的顶板预处理措施。     

Research into stope roof control of compound roof by solid backfilling mining

Based on the analysis of the failure characteristics and backfilling effect of the compound roof at 1801 backfilling workface in Taiyuan coal mine,China,we propose a method of controlling the presubsidence of a compound roof by using pre-stressed bolts to improve the backfilling ratio of the workface so as to maintain the global stability of the stope roof.In addition,PHASE simulation software was employed to analyze the influence law of pre-stressing force,length,and interval on roof subsidence at the workface.On the basis of the numerical simulation results,a model for calculating the pre-stressing force and length of the bolts,the interval between the bolts,as well as roof subsidence at the workface,was established by using SPSS regression analysis software.Moreover,the research results were applied successfully to the 1801 filling workface.According to the monitoring data of roof closure,it was found that the final subsidence value for the goaf roof was 350 mm and the filling ratio at the workface was 86%,which could fully meet the demand for safety production at the workface.The safe and effective control of the stope roof was therefore realized,which achieves the goal of safe and efficient backfilling mining under a compound roof.     

工作面不同推进方向条件下顶煤移动规律的研究

本文通过实验室相似模拟试验对在缓倾斜或近水平厚煤层综采放顶煤开采时，工作面不同推进方向条件下的顶煤移动规律进行研究，得出了不同条件下的顶煤移动规律，并从力学角度对顶煤块体的移动进行了分析，从而给出了顶煤移动规律的力学解释。     

用瞬变电磁法探查综放工作面顶板水体的研究

随着机械化综采设备在煤炭开采中的普及,对煤层顶板管理要求愈来愈高,其中煤层顶板水害体的发育将影响综采设备充分发挥效能,甚至会威胁工作面安全回采．提前查明煤层顶板水害体发育位置,为在井下布置探放水钻孔提供依据,是目前矿井地球物理勘探亟待解决的问题．基于地面瞬变电磁法理论及应用技术,根据井下实际应用环境,研究出采用非接触式、多匝数的正方形重叠回线（边长2m左右）装置探测工作面顶板水害体发育位置．依据瞬变电磁场”烟圈效应”理论和物理模拟相似准则,推导出全空间瞬变电磁法视电阻率计算数学模型,并对矿井瞬变电磁探测综放工作面顶板水害技术进行了研究．采用矿井瞬变电磁技术查明综放工作面顶板水害体发育位置,通过井下疏放水钻孔和工作面回采资料验证,该方法探测综放工作面顶板水害体发育的空间位置不仅行之有效,而且明显优越于其它矿井物探方法．     

大型采空区下持续开采空区稳定性研究

31-1#矿体采空区暴露面积为6000 m2,空区高度为60 m。随着空区下部矿体开采的持续进行,空区暴露高度将达100 m左右;在巨大的采空区下进行采矿作业,一旦发生空区围岩失稳,将对作业中的人员和设备带来巨大灾难。采用有限元对空区下部矿体开采过程中空区顶板围岩的应力、安全率、垂直最大位移、塑性区分布进行了模拟分析,根据模拟结果可知:随着矿房、矿柱、下部矿体开采完成后,顶板的位移和应力有所增加,安全率有所下降,塑性区进一步扩大,地压活动有进一步恶化的趋势,但空区围岩总体上趋于稳定。在空区顶板和两腰安装监测仪器对空区围岩的稳定性进行监测,监测结果和数值模拟结果具有良好的一致性。     

Systematic principles of surrounding rock control in longwall mining within thick coal seams

Effective surrounding rock control is a prerequisite for realizing safe mining in underground coal mines.In the past three decades, longwall top-coal caving mining(LTCC) and single pass large height longwall mining(SPLL) found expanded usage in extracting thick coal seams in China. The two mining methods lead to large void space left behind the working face, which increases the difficulty in ground control.Longwall face failure is a common problem in both LTCC and SPLL mining. Such failure is conventionally attributed to low strength and high fracture intensity of the coal seam. However, the stiffness of main components included in the surrounding rock system also greatly influences longwall face stability.Correspondingly, surrounding rock system is developed for LTCC and SPLL faces in this paper. The conditions for simultaneous balance of roof structure and longwall face are put forward by taking the stiffness of coal seam, roof strata and hydraulic support into account. The safety factor of the longwall face is defined as the ratio between the ultimate bearing capacity and actual load imposed on the coal wall.The influences provided by coal strength, coal stiffness, roof stiffness, and hydraulic support stiffness,as well as the movement of roof structure are analyzed. Finally, the key elements dominating longwall face stability are identified for improving surrounding rock control effectiveness in LTCC and SPLL faces.     

宜昌磷矿地压显现规律及数值模拟

在调查宜昌神农、樟村坪、桃坪河等磷矿的地压显现情况的基础上,总结了宜昌磷矿地压显现规律,主要表现为:顶板易发生不规则块体冒落、板状冒落、窝状冒落、顶板下沉等破坏现象;矿柱易发生片落(或剥落)式破坏、劈裂破坏、剪切破坏,以及这些破坏形式的组合;底板易发生鼓胀及开裂变形.利用离散元软件3DEC,结合研究区工程地质条件,分析了宜昌磷矿地压显现机理,认为引起地压活动的原因可归纳为内因和外因两个方面.其中,矿山岩体赋存的地应力条件、地质构造及岩体结构是决定地压活动规律的内因,矿山开采活动、地下水是控制地压活动形式及剧烈程度的外因.建议因地制宜,选择合理的开采方式,并加强地压及变形监测.     

综采放顶煤地表移动规律特殊性

调查分析了兖州矿区鲍店矿综采放顶煤工作面和普通综采工作面地表移动观测站实测资料．研究结果表明：综放开采时地表移动更加剧烈,地表危险移动范围增大,超前影响范围超过常规分层开采约４０％,下沉活跃期占总移动时间的７１．４％,活跃期下沉量约占总下沉量的９５％．研究还表明,采厚是控制超前影响角和最大下沉速度滞后角的重要因素之一,地表充分采动区存在的残余变形现象更加明显     

控顶切底房柱采矿法

控顶切底房柱采矿法采用浅孔切顶、切底、上向平行孔回采中层矿石,改进切顶房柱法的部分工艺,省去下盘脉外底部结构,回采作业在中层矿石“悬臂梁”的保护下进行,适合于矿石稳固但下盘围岩松散破碎的缓倾斜矿体的开采。     

Simulation Analysis of Coal Mining with Top-Coal Caving Under Hard-and-Thick Strata

1 Introduction A large amount of coal seam with hard coal and hard roof exists in the east mining area of China, such as in the representative mining area of Xuzhou, where the hardness is relatively large (f >2); the roof is hard and the thickness is relatively large (about 20 m). Two key problems must be solved for the suc- cessful application of fully-mechanized coal face with top-coal caving technology: the first is the top-coal falling ability and the second is the control of the hard-and-…     

急倾斜放顶煤矿压显现规律的观测与研究

通过对宜洛煤矿李沟井伪俯料放顶煤回采工作面的矿压观测,从4个方面研究了急倾斜伪俯斜放顶煤工作面矿压显现规律;（1）工作面的初次来压、周期来压步距和来压强度;（2）沿工作面走向控制区内的顶板压力状况,以及生产工序对控制区内支柱载荷的影响;（3）研究了沿倾斜方向矿压显现特点,分析了与近水平煤层矿压显现不同的原因;（4）观测了上下巷矿压显现规律,并分析了上下巷压力不同的原因．用统计法对伪俯斜放顶煤采煤法和分层开采上下巷矿压显现作了对比。     

大姚崩落采矿法借计算机模拟优选采场参数

目前大姚铜矿氧化矿采用的是底盘漏斗崩落采矿法。可是矿石损失值很高,虽然矿山做了大量工作,但是仍然不能将其降至设计的指标。鉴于目前的状况,为了掌握在矿山具体条件下崩落矿岩的流动规律;矿体产状、采场结构参数以及回采工艺与回贫指标之间的关系;以便为改进采矿方法、结构参数和回采工艺提供具有说服力的依据。展开了计算机模拟的最优化研究。论文说明了计算机模拟的试验方法并且分析了所获得的结果,提出了对实际生产具有指导意义的选择与建议。     

Simulation of recovery of upper remnant coal pillar while mining the ultra-close lower panel using longwall top coal caving

With the depletion of easily minable coal seams, less favorable reserves under adverse conditions have to be mined out to meet the market demand. Due to some historical reasons, large amount of remnant coal was left unrecovered. One such case history occurred with the remnant rectangular stripe coal pillars using partial extraction method at Guandi Mine, Shanxi Province, China. The challenge that the coal mine was facing was that there is an ultra-close coal seam right under it with an only 0.8–1.5 m sandstone dirt band in between. The simulation study was carried out to investigate the simultaneous recovery of upper remnant coal pillars while mining the ultra-close lower panel using longwall top coal caving(LTCC). The remnant coal pillar was induced to cave in as top coal in LTCC system. Physical modelling shows that the coal pillars are the abutments of the stress arch structure formed within the overburden strata. The stability of overhanging roof strata highly depends on the stability of the remnant coal pillars. And the gob development(roof strata cave-in) is intermittent with the cave-in of these coal pillars and the sandstone dirt band. FLAC3 D numerical modelling shows that the multi-seam interaction has a significant influence on mining-induced stress environment for mining of lower panels. The pattern of the stress evolution on the coal pillars with the advance of the lower working face was found. It is demonstrated that the stress relief of a remnant coal pillar enhances the caveability of the pillars and sandstone dirt band below.