开挖卸荷岩质坡体的断裂破坏机理

岩质坡体在开挖过程中的失稳破坏已成为道路工程领域日益严重的问题,目前有关卸荷坡体的断裂破坏机理还不清晰。为此,基于自然坡体实际结构特征,并结合岩石力学知识,首先分析了岩体原生裂纹在坡体开挖前后的应力状态。继而,借助断裂力学理论,解析了不同荷载模式下岩体裂纹失稳扩展的力学条件,探讨了求解裂纹扩展方向和规模的计算方法,构建结构面扩展贯通力学模型;最后,通过具体算例验证了模型的合理性。研究表明开挖岩质坡体的失稳是岩体内特定方向的原生裂纹萌生启裂并扩展贯通的结果,其本质是岩体应变能释放耗散与应力的调整过程。

Fracture Failure Mechanism of Rock Slope Under Excavation

As one of the most serious hazards in slope engineering, the collapse is very hard to control safely because the fracture failure mechanism of rock slope with excavation is not clearly. Here based on the structural character of natural rock slope and by the aid of Rock Mechanism, the stress states of crack initiation before and after the excavation are studied firstly. Then from the view of Fracture Mechanics, the stress condition of crack under two stress modes of tension-shear and compression-shear are analyzed respectively. Meanwhile, take energy method as main way, by studying the mechanism of input-dissipation of deformation strain energy during unloading, the way how to calculate the crack growth amount is proposed. Furthermore, the propagation direction is also given and the slope failure mechanism is researched clearly. Finally, an example is given to prove the theory. The result shows the failure of rock slope under excavation is mainly the result of the discontinuous propagation and continuous accumulation of cracks with special direction under different unloading stress environment, which essence is a process of energy input-dissipation and stress adjustment.