美国快速推进长壁工作面开采设备发展现状

介绍了美国现代快速推进长壁工作面与设备发展现状,尤其是进入21世纪的发展情况。美国现代快速推进工作面与设备全国平均发展水平较高,各矿井差距较小;而我国工作面生产与技术装备水平表现为在地质条件优越的矿区达到甚至超过世界先进水平,无论是设备装备还是安全工效方面均取得较高的成就,但是在地质条件较差的矿区或是老矿区,煤矿装备与安全效能与美国还有较大差距。工作面发展水平严重不平衡是我国煤矿与美国煤矿的重要差距,进一步提高工作面装配水平与安全管理水平是我国煤矿发展的重要方向。

Automation in U.S. longwall coal mining: A state-of-the-art review

This paper reviews the development of U.S. longwall mining from an unknown to became the world standard in the past five decades with emphasis on automation. Large scale longwall face equipment were imported from Germany and United Kingdom to increase production in the 1970 s and great effort was made to improve them to suit U.S. conditions, rather than domestic market. Automation began with the development of electrohydraulic shields in 1984 and continue to present. Introduction of first generation semi-automated longwall system occurred in 1995 and step-to-step improvement continues to present following the development of sensor technology and internet of things(IOT). Since then, emphasis on new development has been concentrated on the improvement of equipment reliability, miner's health and safety as well as production, including dust control techniques, proximity sensor, anti-collision and remote control. Automation is classified into two categories: automation of individual face equipment and automation of longwall system. The automation development of longwall system is divided into three stages: shearer-initiated-shield-advance(SISA), semi-automated longwall system, and remote control shearer.

Underground ground control monitoring and interpretation,and numerical modeling, and shield capacity design

Mine or longwall panel layout is a 3D structure with highly non-uniform stress distribution. Recognition of such fact will facilitate underground problem identification/investigation and solving by numerical modeling through proper model construction. Due to its versatility, numerical modeling is the most popular method for ground control design and problem solving. However numerical modeling results require highly experienced professionals to interpret its validity/applicability to actual mining operations due to complicated mining and geological conditions. Underground ground control monitoring is routinely performed to predict roof behavior such as weighting and weighting interval without matching observation of face mining condition while the mining pressures are being monitored, resulting in unrealistic interpretation of the obtained data on mining pressure. The importance of ground control pressure monitoring and simultaneous observation of mining and geological conditions is illustrated by an example of shield leg pressure monitoring and interpretation in an U.S. longwall coal mine: it was found that the roof strata act like a plate, not an individual block of the size of a shield dimension, as commonly assumed by all researchers and shield capacity is not a fixed property for a longwall panel or a mine or a coal seam. A new mechanism on the interaction between shield's hydraulic leg pressure and roof strata for shield loading is proposed.

Measurement of overburden failure zones in close-multiple coal seams mining

In the Kaiping Coal field,mining of five coal seams,located within 80 m in the Kailuan Group,#5,#7,#8,#9 and#12 coal seam,is difficult due to small interburden thickness,concentrated stress distributions,high coal seam metamorphism,and complex geological conditions.By using the ZTR12 geological penetration radar(GPR)survey combined with borehole observations,the overburden caving due to mining of the five coals seams was measured.The development characteristics of full-cover rock fractures after mining were obtained from the GPR scan,which provides a measurement basis for the control of rock strata in close multiple coal seam mining.For the first time,it was found that the overburden caving pattern shows a periodic triangular caved characteristic.Furthermore,it is proposed that an upright triangular collapsed pile masonry and an inverted triangular with larger fragments piled up alternately appear in the lower gob.The research results show that the roof structure formed in the gob area can support the key overlying strata,which is beneficial to ensure the integrity and stability of the upper coal seams in multiple-seam mining of close coal seams.

Guest Editorial–Special issue on Ground Control in Mining

Ground control is the science of studying and controlling the behavior of rock strata in response to mining operations.Ground control related research has made significant advancements over the last 35 years and these accomplishments are well documented in the proceedings of the annual International Conference

Topical areas of research needs in ground control – A state of the art review on coal mine ground control

Ground control is one of the four subsystems of underground mining. It covers not only roof control, but also rib control, floor control, pillar design, shield design, overburden failures and subsidence. In the past three decades, ground control has made a tremendous advancement and many case studies have demonstrated its important role in the daily mining operations. However, there are plenty of room for improvements. This paper discusses the research needs in 12 subject areas including research approach, rock property, geology, computer modeling, in-situ stresses, roof bolting, coal pillars, field instrumentation,failures, surface subsidence, shield supports and coal bumps.

Guest editorial–Special issue on ground control in mining in 2016

In 1981 a Professor at West Virginia University recognized the need to establish a program for bringing together members of the mining community to share and discuss methods,technology and experiences related to ground control in mining operations[1].From this initial idea the International Conference on

Impact of longwall mining on groundwater above the longwall panel in shallow coal seams

Since longwall mining causes subsidence through the overlying strata to the ground surface, the surface water and groundwater above the longwall panels may be affected and drained into the lower levels.Therefore, loss or interruption of streams and overburden aquifers is a common concern in coal industry.This paper analyzed the potential effects of longwall mining on subsurface water system in shallow coal seam. In order to monitor different water level fluctuations throughout the mining period, three water wells were drilled down to the proposed deformation zone above the longwall panel. A GGU-SS-FLOW3 D model was used to predict water table contours for the periods of pre- and post-mining conditions. The field data from the three water wells were utilized to calibrate the model. The field test and numerical model can help to better understand the dewatering of shallow aquifers and surface waters related to ground subsidence from longwall mining in shallow coal seam.

Change of the mode of failure by interface friction and width-to-height ratio of coal specimens

Bumps in coal mines have been recognized as a major hazard for many years. These sudden and violent failures around mine openings have compromised safety, ventilation and access to mine workings.Previous studies showed that the violence of coal specimen failure depends on both the interface friction and width-to-height（W/H） ratio of coal specimen. The mode of failure for a uniaxially loaded coal specimen or a coal pillar is a combination of both shear failure along the interface and compressive failure in the coal. The shear failure along the interface triggered the compressive failure in coal. The compressive failure of a coal specimen or a coal pillar can be controlled by changing its W/H ratio. As the W/H ratio increases, the ultimate strength increases. Hence, with a proper combination of interface friction and the W/H ratio of pillar or coal specimen, the mode of failure will change from sudden violent failure which is brittle failure to non-violent failure which is ductile failure. The main objective of this paper is to determine at what W/H ratio and interface friction the mode of failure changes from violent to non-violent. In this research, coal specimens of W/H ratio ranging from 1 to 10 were uniaxially tested under two interface frictions of 0.1 and 0.25, and the results are presented and discussed.

煤矿巷道底臌的模拟研究

本论文采用边界元——有限元耦合应力分析方法,对美国King No.4煤矿中第四采区巷道底臌与采空区和水平地质构造应力之间的关系进存了探讨。基于计算结果,本文发现较大的采空区范围以及较大的水平地质构造应力是导致该区域巷道底臌的重要原因等结论。图4,表2,参4。

煤矿开采集中应力和构造应力对巷道底鼓的影响

本论文采用边界元——有限元耦合应力分析方法,对美国King No.4煤矿中第四采区巷道底鼓与采空区和水平地质构造应力之间的关系进行了探讨。基于计算结果,本文发现较大的采空区范围以及较大的水平地质构造应力是导致该区域巷道底鼓的重要原因等结论。