基于FLAC3D的不同断层倾角对采空区顶板塑性区演化影响的数值模拟研究

Numerical Simulation Study on the Influence of Different Fault Dip Angles on the Evolution of the Plastic Zone in the Goaf Roof Based on FLAC3D

摘要: 断层作为煤系地层中常见的地质构造，其倾角大小对采动覆岩的应力传递与塑性破坏演化具有决定性影响。文章以某矿某工作面过断层安全开采为工程背景，基于FLAC3D有限差分数值模拟软件，建立了等效埋深200 m (上覆载荷5 MPa)的三维力学模型。通过设置断层与煤层底板交点固定，系统探讨了30˚、45˚、60˚及75˚四种断层倾角工况下，采空区顶板塑性区的空间贯通机制与主应力偏转规律。研究表明：断层倾角与塑性区的发育程度呈显著的非线性负相关；在低、中倾角(30˚, 45˚)断层中，采动附加应力极易诱发断层面产生剪切滑移，导致工作面顶板塑性区与断层破碎带发生宏观贯通，极易引发顶板台阶下沉；而在高倾角(60˚, 75˚)断层中，断层面的法向“夹持”效应增强，滑移失稳受到抑制，顶板塑性区范围相对收缩，但断层底板端部的应力集中系数显著升高。研究结果为邻近断层工作面的合理保安煤柱留设及顶板差异化支护提供了理论依据。

Abstract: Faults are common geological structures in coal-bearing strata, and their dip angles critically influence stress transfer and plastic failure evolution in overburden strata induced by mining. Taking the safe mining through a fault in a certain working face of a coal mine as the engineering background, this study established a three-dimensional mechanical model with an equivalent burial depth of 200 m (overburden load of 5 MPa) using the FLAC3D finite‑difference numerical simulation software. By fixing the intersection point of the fault and the coal seam floor, the spatial coalescence mechanism of the plastic zone in the goaf roof and the deflection pattern of principal stresses were systematically investigated under four fault dip angles of 30˚, 45˚, 60˚, and 75˚. The results indicate that the fault dip angle exhibits a significant nonlinear negative correlation with the development of the plastic zone. For low‑ to moderate‑angle faults (30˚ and 45˚), mining‑induced additional stresses readily trigger shear slip along the fault plane, leading to macroscopic coalescence between the plastic zone in the working face roof and the fault fracture zone, which easily induces step subsidence of the roof. In contrast, for high‑angle faults (60˚ and 75˚), the normal “clamping” effect on the fault plane is enhanced, restraining slip instability and relatively shrinking the extent of the roof plastic zone, while the stress concentration coefficient at the fault floor end increases significantly. The findings provide a theoretical basis for the rational design of safety coal pillars and differentiated roof support in working faces adjacent to faults.