Klemetti T M, Van Dyke M A, Tulu I B, Tuncay D
NIOSH Pittsburgh Mining Research Division, Pittsburgh 15236, USA.
Department of Mining Engineering, West Virginia University, Morgantown 26505, USA.
Int J Min Sci Technol. 2020 Jan;30(1):25-31. doi: 10.1016/j.ijmst.2019.12.002.
Longwall abutment loads are influenced by several factors, including depth of cover, pillar sizes, panel dimensions, geological setting, mining height, proximity to gob, intersection type, and size of the gob. How does proximity to the gob affect pillar loading and entry condition? Does the gob influence depend on whether the abutment load is a forward, side, or rear loading? Do non-typical bleeder entry systems follow the traditional front and side abutment loading and extent concepts? If not, will an improved understanding of the combined abutment extent warrant a change in pillar design or standing support in bleeder entries? This paper details observations made in the non-typical bleeder entries of a moderate depth longwall panel-specifically, data collected from borehole pressure cells and roof extensometers, observations of the conditions of the entries, and numerical modeling of the bleeder entries during longwall extraction. The primary focus was on the extent and magnitude of the abutment loading experienced due to the extraction of the longwall panels. Due to the layout of the longwall panels and bleeder entries, the borehole pressure cells (BPCs) and roof extensometers did not show much change due to the advancing of the first longwall. However, they did show a noticeable increase due to the second longwall advancement, with a maximum of about 4 MPa of pressure increase and 5 mm of roof deformation. The observations of the conditions showed little to no change from before the first longwall panel extraction began to when the second longwall panel had been advanced more than 915 m. Localized pillar spalling was observed on the corners of the pillars closest to the longwall gob as well as an increase in water in the entries. In addition to the observations and instrumentation, numerical modeling was performed to validate modeling procedures against the monitoring results and evaluate the bleeder design. ITASCA Consulting Group's FLAC3D numerical modeling software was used to evaluate the bleeder entries. The results of the models indicated only a minor increase in load during the extraction of the longwall panels. These models showed a much greater increase in stress due to the development of the gateroad and bleeder entries--about 80% development and 20% longwall extraction. The FLAC3D model showed very good correlation between modeled and expected gateroad loading during panel extraction. The front and side abutment extent modeled was very similar to observations from this and previous panels.
长壁工作面支承压力受多种因素影响，包括覆岩深度、煤柱尺寸、采区尺寸、地质条件、采高、与采空区的距离、交岔点类型以及采空区尺寸。与采空区的距离如何影响煤柱载荷和巷道状况？采空区的影响是否取决于支承压力是前方、侧面还是后方载荷？非典型的泄风巷道系统是否遵循传统的前方和侧面支承压力范围概念？如果不遵循，对组合支承压力范围的深入理解是否会促使改变泄风巷道中的煤柱设计或支护方式？本文详细介绍了在一个中等深度长壁采区的非典型泄风巷道中的观测结果——具体来说，包括从钻孔压力传感器和顶板伸长仪收集的数据、巷道状况观测以及长壁开采期间泄风巷道的数值模拟。主要重点是长壁采区开采引起的支承压力范围和大小。由于长壁采区和泄风巷道的布局，钻孔压力传感器（BPC）和顶板伸长仪在第一个长壁推进时变化不大。然而，在第二个长壁推进时它们显示出明显增加，压力最大增加约4MPa，顶板变形5mm。巷道状况观测表明，从第一个长壁采区开采开始到第二个长壁采区推进超过915m时，几乎没有变化。在最靠近长壁采空区的煤柱角部观察到局部煤柱剥落，巷道中的水量也有所增加。除了观测和仪器测量外，还进行了数值模拟，以根据监测结果验证模拟程序并评估泄风巷道设计。使用ITASCA咨询集团的FLAC3D数值模拟软件评估泄风巷道。模型结果表明，长壁采区开采期间载荷仅略有增加。这些模型显示，由于联络巷和泄风巷道的形成，应力增加幅度更大——约80%是由于巷道形成，20%是由于长壁开采。FLAC3D模型显示，在采区开采期间，模拟的联络巷载荷与预期载荷之间具有很好的相关性。模拟的前方和侧面支承压力范围与本次及以前采区的观测结果非常相似。
