Extraction of coal mine methane is widely used in complex geological conditions. It does not only effectively prevent potential gas disasters, but it also alleviates energy crisis of the world. However, the high-efficiency extraction of coal mine methane is positively correlated with accurate positioning of mining-induced fracture-rich areas (relatively intensive fracture areas), which is yet to be fully understood (in particular on a 3D scale). In this paper, a simple fracture constitutive model was incorporated within a continuum code, and an innovative approach to fracture generation was proposed to get the fracture morphology. First, the code was tested against the uniaxial compression and true 3D experiments and it was shown to be capable of simulating fracture initiation and propagation on either 2D or 3D scale. This code then was used successfully to 3D longwall mining, and the numerical results were well in keeping with the field monitoring and physical modeling. The numerical results revealed that the fractured zones exhibit a 3D elliptic paraboloid shape, and mining-induced shear fractures, which dominated over the tensile fractures, had a 3D annular shape above the overlying strata, whereas a ribbon shape was observed for tensile fractures. A fracture-rich area was formed gradually at the center (exactly closer to the cut) above the gob, implying that the collapse mainly occurred in the gob roof rather than in the gob sidewall. The strengthening effect of mining-induced fractures on the permeability in longitudinal direction was markedly stronger than in transverse directions. The obtained results also suggest that the mining direction should be parallel to the maximum horizontal stress. Overall, the proposed model provides a promising tool for solving 3D complex engineering issues.

煤矿瓦斯的提取广泛用于复杂的地质条件。它不仅有效地防止了潜在的天然气灾害，而且还缓解了世界能源危机。但是，煤矿瓦斯的高效开采与采矿引起的富裂缝区域（相对密集的裂缝区域）的精确定位正相关，这尚待充分了解（特别是在3D尺度上）。在本文中，一个简单的裂缝本构模型被纳入到一个连续的代码中，并提出了一种创新的裂缝生成方法来获得裂缝的形态。首先，针对单轴压缩和真实的3D实验对代码进行了测试，结果表明该代码能够模拟2D或3D规模的裂缝萌生和扩展。该代码随后成功用于3D长壁开采，数值结果与现场监测和物理建模完全吻合。数值结果表明，断裂带呈3D椭圆抛物面形状，采矿引起的剪切断裂占主导地位，拉伸断裂上覆岩层上方具有3D环形形状，而拉伸断裂则呈带状。采空区上方的中心（恰好靠近切口）逐渐形成了一个富含裂缝的区域，这意味着塌陷主要发生在采空区顶部而不是采空区侧壁。采矿引起的裂缝对纵向渗透率的增强作用明显强于横向方向。所得结果还表明，开采方向应平行于最大水平应力。总体而言，所提出的模型为解决3D复杂工程问题提供了有希望的工具。