采动应力作用下煤-岩界面拉伸断裂特性及裂纹扩展机制

The failure of coal-rock interface caused by mining-induced stress in underground coal mine is the one of the main reasons of coal wall rib fall and rock burst disasters. In view of the insufficiency of the research on the formation and propagation mechanism of coal-rock interface crack under mining-induced stress, the coal-rock interface is taken as the research object and the research method of experimental research and theoretical analysis is adopted. The formation mechanism of tensile fracture cracks at coal-rock interface under mining-induced stress condition will be revealed, and the difference between interfacial fracture characteristics and fracture of single coal and rock will be clarified. The influence of loading rate and interfacial roughness on interfacial fracture characteristics will be analyzed. We will study the energy transfer mechanism of interface fracture and based on energy release characteristics we will establish the tensile fracture criterion of coal-rock interface. Through the study of the propagation law of coal-rock interface, the influence of three-dimensional morphology parameters on interface strength will be revealed. And we will establish the relation model between interface roughness and interface strength. The calculation method of interfacial crack strain will be investigated and the relationship between interfacial crack strain and mining stress will be determined. Based on the evolution characteristics of interface crack strain, a model of interface crack propagation will be established to reveal the mechanism of interface crack propagation under mining-induced stress. The project research will provide evaluation model and theoretical reference for the study of coal wall rib fall and rock burst mechanism in underground coal mine working face.

地下煤炭开采中，采动应力作用下工作面前方煤-岩界面破坏是引发煤壁片帮和冲击地压灾害发生的主要原因之一。针对煤-岩界面裂纹形成及扩展机制研究的不足，以煤-岩界面为研究对象，采用试验研究与理论分析的研究方法，揭示采动应力条件下煤-岩界面拉伸断裂裂纹形成机制，阐明界面断裂特性与煤、岩单体断裂的差异，分析加载速率及界面粗糙度对界面断裂特性的影响，探索界面断裂的能量转移机制，基于能量释放特征建立界面拉伸断裂准则；研究采动应力作用下界面裂纹的扩展规律，揭示界面三维形貌参数对界面强度的影响，建立界面粗糙度与界面强度的关系模型，研究界面裂纹应变的计算方法，确定其与采动应力的关系；基于界面裂纹应变的演化特征，建立界面裂纹扩展模型，揭示采动应力下界面裂纹扩展机制。项目研究为工作面煤壁片帮和冲击地压形成机理提供评价模型及理论参考。

作为地下煤炭开采中的弱面，工作面前方煤岩界面的破坏会造成煤壁片帮或诱发冲击地压灾害。相关基础研究工作得到了国内外关注，其中煤岩界面断裂特性、准则及界面裂纹扩展模型是难点问题，须重点研究。申请人在本项目资助下对采动煤岩界面拉伸断裂特性及裂纹扩展机制进行了大量的实验研究，主要取得了以下研究成果。分析了煤岩组合体加载变形破坏过程中的裂纹演化规律，建立了基于裂纹演化的煤岩组合体峰前裂纹闭合模型、裂纹张开模型、裂纹扩展模型应力-应变关系模型；通过对煤岩体开展不同卸围压速率及不同开采方式条件下的试验研究，揭示了较大的卸荷速率导致较大的裂纹扩展速度，且增大了煤岩体的冲击倾向性，进而极易诱发岩爆或冲击地压；提出了一个新的基于裂纹体积应变的损伤变量，获得了以下四个阶段的破坏过程：初始损伤阶段；弹性阶段；线性损伤阶段；加速损伤阶段；提出了在莫尔应力空间中，将失效包络线拟合到相邻两个莫尔圆的所有公共切点上的方法，为煤岩体破坏强度准则研究提供了理论参考；建立了基于裂纹闭合的煤岩体能量耗散模型，能较好地描述煤岩体在压缩下的能量耗散特征。研究结果为地下煤炭开采工作面煤壁片帮及冲击地压形成机理提供理论参考和科学决策依据。