极近距离采空区下大断面开切眼支护工艺优化研究

Study on optimization of supporting technology for large cross-section open-off cut under contiguous gob

针对极近距离采空区下大断面开切眼及相关硐室围岩变形情况复杂,且该工况下支护结构可靠性验证及优化研究不足等问题,通过FLAC^(3D)与ANSYS数值模拟软件对采空区下开切眼掘进过程围岩及支护结构变形及受力进行模拟计算,并对支护工艺及相关参数进行优化,对比不同支护排距下巷道围岩变形及应力集中状态,并通过现场工程应用及围岩变形实测验证支护方案的合理性。研究表明:通过薄板理论计算得到开切眼顶板无支护条件下初次破断距为19.6 m,周期破断距为8 m,因此在进行架棚支护时最大滞后距离不应超过8 m;数值模拟计算表明当支护排距为1 m时,在锚杆+金属棚+单体支柱联合支护段,相比无支护条件顶板减沉率达到38.73%,支护排距加密为0.5 m后顶板减沉效果显著提高,开切眼中部顶板减沉率达到60%以上,加密支护后中部顶板下沉量降至20 mm以内,完全满足顶板支护要求;现场监测顶板最大下沉量12 mm,最大离层量6 mm,顶板控制效果良好。优化后方案在顶板下沉量控制与顶板垂直应力减压方面具有显著效果。

In view of the complex deformation of large-section open-off cuts and related chamber in surrounding rocks under contiguous mined-out area and the insufficient research on reliability verification and optimization of the supporting structure under this working condition, the deformation and stress of surrounding rock and support structure were simulated and calculated during open-off cut excavation under the mined-out area by FLAC^(3D) and ANSYS numerical simulation software, and the supporting technology and related parameters were optimized. The deformation and stress concentration state of surrounding rock under different support row spacings were compared, and the rationality of the support scheme was verified by field engineering application and actual measurement of surrounding rock deformation. The results show that the initial breaking distance of the open-cut roof without support is 19.6 m and the periodic fracture distance is 8 m under the condition of no support. Therefore, the maximum lag distance should not be more than 8 m when supporting the roof. Numerical simulation calculations show that when the supporting row spacing is 1 m, the roof subsidence reduction rate can reach 38.73% in the combined supporting section of bolt, metal shed, and hydraulic prop. When the row spacing is densified to 0.5 m, the effect of roof subsidence reduction is significantly improved, the roof subsidence reduction rate in the middle of the open-off cut is more than 60%,and the subsidence of the middle roof is reduced to less than 20 mm after the densification of support row spacing, which fully meets the requirements of roof support. The on-site monitoring results show that the maximum subsidence value of the roof is 12 mm and the maximum separation distance is 6 mm and the roof control effect is good. The optimized scheme has significant effects on roof subsidence control and stress reduction of the roof.