开挖加卸荷诱发深部巷道岩爆机理研究

Rock burst is a dynamic phenomenon caused by excavation unloading of underground engineering in high geostress areas. The mechanical mechanism is extremely complex. At present, the mechanism that unloading induces rockburst isn't clear yet. .In view of essence that stress disturbance induces the roadway rockburst occur, this project presents taking non-axial loading and unloading as the mechanical model. Using the methods of loading-unloading rock mass mechanical characteristic experiments, similar material simulation, in-situ microseismic monitoring and ground stress analysis, the mechanical mechanism and precursory pattern of rockburst preparation in deep roadway will be investigated. The constitutive model and failure criterion of non-axial loading-unloading will be established..Identifying the evolution process of micro-fracture initiation, development and connection, the deformation and failure characteristics under rock mass non-axial loading-unloading and mechanical mechanism to trigger rockburst will be investigated. Determining the relationship between microstructure characteristic, mineral composition of rockmass and rock burst, the microcosmic mechanical mechanism of rockburst preparation is to be revealed. Reversing the law of mocroseismic activity from the view point of background stress field, the inherent relation between stress field evolution of rock mass excavation loading-unloading and microseismicity in rock burst preparation process will be explored. Seeking the relation between background stress field evolvement, microseismicity and loading-unloading, a new precursory theoretical model of rockburst predicition will be established..This research can reveal the mechanical mechanism of rockburst, and recognize the mechanism that excavation loading-unloading causes rockburst. Moreover, the occurrence condition and physical process of rock burst can be revealed. The results can provide a scientific basis for mine rockburst prediction.

岩爆是高地应力区地下工程开挖卸荷产生的动力现象，其力学机制极其复杂，目前，对卸荷诱发岩爆机理还不清楚。本项目提出从应力扰动诱发微破裂导致巷道岩爆发生的本质出发，以异轴加、卸荷为力学模型，采用加卸荷岩体力学特性实验、相似材料模拟、现场微震监测和背景应力场分析等手段，研究深部巷道岩爆孕育的力学机制和前兆模式，建立异轴加卸荷本构模型和破坏准则。查明微破裂萌生、发展、连通的演化过程，探求岩体加卸荷变形破坏特征及触发岩爆的力学机制；明确岩体微观结构特征、矿物组分与岩爆的关系，揭示岩爆孕育的微观力学机理；从背景应力场的角度反演微震活动规律，探索岩体开挖加卸荷应力场演化与岩爆孕育过程中微震活动性的内在联系，寻求背景应力场演化、微震活动性与加卸荷之间的联系，建立新的岩爆预测前兆理论模型。本研究可揭示岩爆的力学机制，认清开挖加卸荷引发岩爆的机理，弄清岩爆发生条件和物理过程，为矿山岩爆的预测提供科学依据。

本项目提出从加、卸荷诱发岩爆发生的本质出发，研究深部巷道岩爆孕育的力学机制和前兆模式。基于矿山深部微震监测结果，提取微震时空分布信息数字化信息。采用数值分析软件，构建矿山三维模型，开挖与实际工程相似的巷道、硐室模型，模拟分析应力、位移、微破裂的形成和扩展过程，从应力场演变的角度分析岩爆的孕育过程，建立新的岩爆预测前兆理论模型。微震监测与数值模拟结果对比表明：微震事件大多分布在矿体下盘，即应力场变化较为剧烈的区域，而应力场变化较小的区域微震事件也少。.进行增轴压同时卸围压实验，研究岩体异轴加卸荷条件下的变形、破坏和强度特征及其破坏机制。试验结果表明：（1）快速卸荷下呈现劈裂破坏，而较慢速卸荷下呈现张剪性破坏。卸载速率越快，岩石脆性破坏越强，发生岩爆的可能性越大；（2）岩石加卸荷破坏与中间主应力有密切关系，建立了能较好地描述高应力条件下岩石卸荷破坏特征的强度准则；（3）基于室内试验结果，建立了加卸荷条件下岩体的弹脆塑性本构模型。.利用TRW-3000岩石真三轴试验系统，对岩石和相似模拟材料进行真三轴加卸载下的岩爆试验。试验结果表明：（1）试样破坏形态呈现复合破坏模式，初始应力水平越高，岩爆也越强烈；（2）位移控制加轴压、卸围压试验条件下，岩样破坏模式主要为劈裂加剪切、主剪切破坏，其破坏特征在卸围压速率相同的情况下主要与卸荷初始围压有关。当卸荷速率较小时，随着初始围压值的增大，加卸荷破坏由拉剪破坏形式向压剪破坏形式转变，以压剪破坏形式为主；当卸荷速率较大时主要表现为拉剪破坏。.利用SEM、XRD等仪器，分析岩样典型破裂断口细观形貌特征，观察岩体的显微结构特征。研究表明：（1）岩体的微观破裂表现为沿晶张拉和穿晶剪切断裂的复合形态。岩石内部微裂纹以沿晶张拉型为主，随卸载速率增大，破裂面的张性特性明显。（2）有机显微组分的力学性质以及含量决定了岩体的物理力学性质。显微硬度和显微脆度均较大的岩体较易发生岩爆。