Zhu Yanhui, Tian Ye, Gong Peilin, Wen Guang, Yi Kang
College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, China.
School of Mines, China University of Mining & Technology, Xuzhou, 221116, China.
Sci Rep. 2024 Sep 17;14(1):21684. doi: 10.1038/s41598-024-72883-1.
The secondary mining movement in non-pillar coal extraction causes significant overrun damage to flexible formwork concrete walls, leading to extensive deformation of roadway roof and bottom plates. This adversely affects working face efficiency and safety. The engineering context focuses on the non-pillar gob-side retaining walls in the 1315 working face of Zhaozhuang Coal Mine and the 23107 working face of Xiegou Coal Mine. Through on-site investigation, numerical simulation, theoretical analysis, and testing, we explore the stress migration law and destabilizing mechanism of the flexible formwork concrete wall influenced by the secondary mining movement of the coal-free pillar along the hollow wall. The research results showed that: (1) During the mining back process, the concrete wall formed with flexible formwork may experience stress concentration, leading to excessive damage and compromising mining safety. (2) Developing a predictive stress model for the concrete wall with flexible formwork is essential. If the stress surpasses the ultimate compressive strength during mining back, reinforcement becomes necessary.3) The length of damage overrun in the flexible formwork concrete wall exhibits two distinct stages as the distance back to mining increases. The first stage shows nearly linear growth, while the second stage indicates a decreasing growth rate, ultimately stabilizing. The application of Z6 concrete reinforcing agent effectively strengthens the flexible formwork concrete wall.
无煤柱开采中的二次采动对柔性模板混凝土墙体造成显著的超限破坏，导致巷道顶板和底板发生大面积变形。这对工作面的效率和安全产生了不利影响。工程背景聚焦于赵庄煤矿1315工作面和斜沟煤矿23107工作面的无煤柱沿空留巷墙体。通过现场调研、数值模拟、理论分析和试验，我们探究了沿空无煤柱二次采动影响下柔性模板混凝土墙体的应力迁移规律及失稳机理。研究结果表明：(1)在回采过程中，采用柔性模板形成的混凝土墙体可能会出现应力集中，导致过度破坏，危及回采安全。(2)建立柔性模板混凝土墙体的应力预测模型至关重要。若回采时应力超过极限抗压强度，则需进行加固。(3)随着回采距离增加，柔性模板混凝土墙体的破坏超限长度呈现两个不同阶段。第一阶段近似线性增长，第二阶段增长速率递减，最终趋于稳定。Z6混凝土增强剂的应用有效增强了柔性模板混凝土墙体。
