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在普立特大桥隧道锚现场模型试验的基础上,采用数值模拟技术揭示了隧道锚围岩变形破坏过程:围岩破坏面从锚体底部与围岩接触面附近启裂,并逐渐向外呈圆台状扩散,破坏形式为拉剪破坏。并且,锚体前部临空岩体被拱出而发生拉破坏。破坏面上的应力分布随着拉拔荷载增大而发生复杂变化。基于此,通过在破坏面上建立力的平衡关系,提出了隧道锚围岩抗拔力计算模式。该计算模式与现有文献不同,体现了夹持效应以及破坏面上的复杂应力变化。破坏面上的应力分布需要通过模型试验和数值模拟论证得到。今后,在针对不同强度、不同结构特征的岩体进行全面试验分析的基础上,可以对破坏面形态和应力大小进行取值建议。采用该模式验证了试验结果,估算得到大桥原型锚碇的极限抗拔力非常大。目前隧道锚设计普遍偏于保守,隧道锚在中、软岩中仍然可以使用。讨论了破坏面形态特征可能的变化、岩体结构特征对抗拔力的影响等问题。
On the basis of the anchor model experiment of Pulit Bridge, the deformation and failure process of surrounding rock of tunnel anchor is revealed by numerical simulation: the failure surface of the surrounding rock detonates near the contact surface between the bottom of anchor body and the surrounding rock, Round table-shaped proliferation, destruction of the form of tensile shear damage. In addition, the front of the anchor body is emptied and the rock mass is pulled out. The stress distribution on the failure surface varies with the increase of drawing load. Based on this, by calculating the equilibrium relationship of forces on the failure surface, the calculation model of the anti-pullout force of the tunnel anchor is proposed. This calculation mode is different from the existing literature, which shows the clamping effect and the complicated stress changes on the failure plane. The stress distribution on the failure surface needs to be verified through model tests and numerical simulation. In the future, based on the comprehensive experimental analysis of rock mass with different strength and different structural features, the shape and the size of the damaged surface can be taken as suggestions. The model is used to verify the test results. It is estimated that the ultimate pullout resistance of the bridge prototype anchor 非 is very large. At present, the design of tunnel anchors is generally conservative. Tunnel anchors are still in use in soft rock. The possible changes of morphological characteristics of failure surface and the influence of structural features of rock mass on the anti-pull-out force are discussed.