隧道式锚碇系统的承载特性及破坏机理研究

Tunnel anchor is more economical and environmentally friendly than gravity anchor. It will have wide range of applications in the building of suspension bridge in the west canyon area of the country. Experimental studies have shown that tunnel anchor has a strong ability of pullout because of the clamping effect that caused by the wall rock, but bearing capacity characteristics and failure mechanisms of tunnel anchor system is unclear. So instead of tunnel anchor, gravity anchor often used to resist the load of suspension bridge as a conservative design. In the project, gemechanical model test, numerical simulation and mechanics analytical method are used to explore the bearing capacity characteristics and failure mechanisms of tunnel anchor. Deformations and failure modes of anchor system are monitored in the model test, the whole failure process of anchor system which is including elastic deformation, plastic deformation, and limit instability is studied by analyzing the results of model test. In addition, based on the results of model test, back analysis method is used to determine the suitable numerical simulation model for tunnel anchor system. The clamping effect of wall rock and the load transfer of anchor are discussed by gemechanical model test and numerical simulation in order to get the bearing capacity characteristics of tunnel anchor system. The failure mechanisms are researched on the basis of failure process and failure surface morphology. According to the bearing capacity characteristics and failure mechanisms, the calculation methods and design guidelines of tunnel anchor system are proposed, which will provide theoretical and technical support for the wide range of applications of tunnel anchor system.

与重力式锚碇相比，隧道式锚碇更为经济、环保，在西部峡谷地区悬索桥建设中具有广阔的应用前景。已有试验研究经验表明，隧道式锚碇系统因围岩的“夹持效应”而具有强大的抗拔能力，但承载特性及破坏机理不甚清楚，工程设计上可能保守地舍弃隧道式锚碇结构而采用重力式锚碇。本项目拟利用地质力学模型试验、数值仿真模拟试验、力学解析方法开展研究。通过模型试验，监测隧道式锚碇和围岩的变形及破坏形态，分析锚碇及围岩弹性变形-塑性变形-极限失稳的变形破坏全过程。采用数值仿真模拟，对地质力学模型试验结果进行反分析，结合模型试验成果研究隧道式锚碇围岩结构的“夹持效应”，分析隧道式锚碇系统的荷载传递规律，研究其承载特性。根据隧道式锚碇系统的破坏过程和破坏形态揭示隧道式锚碇系统的破坏机理。根据隧道式锚碇系统的受力特性及破坏机理，提出隧道式锚碇抗拔稳定计算方法和设计准则，为隧道式锚碇的广泛应用提供理论和技术支持。

“隧道式锚碇系统的承载特性及破坏机理研究”（项目批准号：51409013）的执行时间为2015年1月~2017年12月。项目自2015年启动以来，紧密围绕研究目标和研究内容，开展研究工作，取得的研究成果包括：. （1）完成了圆柱、圆台隧道式锚碇系统的模型试验，获得了隧道式锚碇系统各区域的荷载-变形过程曲线及破坏特征。圆柱锚碇系统的破坏特征为锚碇体与围岩胶结面破坏；圆台锚碇系统的破坏特征为锚碇体周边围岩的破坏。两者破坏特征差异主要是因为圆台隧道式锚碇系统在拉拔荷载作用下表现出的“夹持效应”，实现了抗拔荷载向围岩的传递，提升了该系统的承载能力。. （2）根据隧道式锚碇系统模型试验成果完成了该系统的数值模拟反分析，建立了合理反应隧道式锚碇系统变形破坏的数值仿真模型。数值模型计算获得的荷载位移规律与模型试验结果相似，隧道式锚碇系统在荷载作用下，荷载通过锚碇体向围岩传递，带动一定范围内的围岩体发生变形。. （3）利用数值仿真模拟方法开展隧道式锚碇系统的承载特性研究，通过位移云图获得了该结构的变形特征，通过塑性区图表征该结构在极限荷载作用下的破坏形态特征，通过等效塑性应变增量云图表征该结构系统渐进破坏过程，根据该系统破坏面上的应力分布分析了该系统的承载特征。揭示了隧道式锚碇系统的承载特性及破坏机理，拉拔荷载在锚体后部通过倒楔形的锚碇体向围岩扩散，使得较大范围的围岩参与抗拔作用，在较大荷载作用下，围岩发生拉剪破坏，拉剪破坏面从锚碇后端面与围岩接触处开始发生，呈圆台面状向前部渐进扩展，直至围岩破坏。. （4）采用力系平衡原理，通过解析法建立了破坏面上的力平衡关系，建立了隧道式锚碇系统抗拔力计算模式和设计模式。隧道式锚碇系统的设计应以围岩地质条件为基础，以模型试验、数值模拟方法为手段，充分论证考虑隧道式锚碇系统的“夹持效应”，分析围岩破坏面形态及破坏面上的剪应力和正应力的分布特征，开展隧道式锚碇系统稳定性计算和设计。