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软弱破碎围岩隧道开挖后,在初始应力作用下,围岩松动变形、掌子面失稳,易产生较大内空位移,导致拱顶坍塌、地表下沉等病害。针对软弱破碎围岩的力学特性,提出预留核心土环向刻槽开挖法,并结合工程实例,以数值分析的方法研究核心土对软岩隧道开挖的稳定性影响。利用FLAC3D软件模拟隧道在不同长度及半径核心土条件下的开挖过程,分析掌子面附件围岩的位移、应力及塑性区变化情况。研究表明,预留核心土能减少隧道开挖对软弱破碎围岩的扰动,极大改善掌子面的受力情况,约束掌子面及附件围岩位移,控制塑性变形;核心土的长度及半径影响其对围岩稳定性的作用效果,它们存在一个最合理值。
After the excavation of the soft and fragmented surrounding rock tunnel, under the initial stress, the surrounding rock loosens and the face becomes unstable. As a result, large internal displacement is likely to occur, resulting in collapse of the dome, surface subsidence and other diseases. According to the mechanics characteristics of weak broken rock, the paper puts forward the method of reserving the core earth ring to the groove excavation. Combined with engineering examples, the numerical analysis method is used to study the influence of core soil on the stability of soft rock tunnel excavation. FLAC3D software is used to simulate the tunneling process under different length and radius core soil conditions, and the displacement, stress and plastic zone of the surrounding rock of attachment attachment are analyzed. The results show that reserving the core soil can reduce the disturbance of tunneling on the soft and fragmented surrounding rock, greatly improve the stress on the face, restrict the displacement of the face and appendage and control the plastic deformation. The length of the core and Radius of the impact on the stability of the surrounding rock effect, they exist a most reasonable value.