隧道锚尺寸对其承载特性的影响及破坏机理

Influence of the Size of Tunnel Anchorage on Bearing Behavior and Its Failure Mechanism

锚碇作为跨江悬索大桥的重要组成部分,其变形位移和受力状态直接影响到悬索桥的安全和长期使用的可靠性,而锚碇体的埋深、大小和长度等因素都会对隧道锚的承载性能产生影响。本文以某长江大桥北岸拟建于泥岩上的隧道式锚碇为背景,在保证挖方量一定情况下,通过控制锚碇埋深、截面尺寸、扩展角及锚塞体长度4个参数,采用FLAC-3D有限差分研究了隧道锚各结构尺寸参数对其承载性能的多因素综合影响。结果表明,在承载力较低的软岩上修建浅埋隧道锚,锚碇体最大变形位移主要与后锚面的尺寸有关,后锚面尺寸越大,隧道锚承载特性越好。同时获得了优于原设计的锚碇结构各尺寸参数。对已建成的实桥锚固系统的破坏全过程进行了模拟分析,结果表明,其破坏模式为锚碇围岩受侧向挤压后产生破裂而导致的锚碇体被整体拔出,以供工程参考。

Being an important part of suspension bridge crossing river,the deformation and stress state of anchorage directly affects the safety and long-term reliability of suspension bridge. The buried depth,size and length of the anchor can influence the bearing capacity of tunnel anchorage. By controlling four parameters（ anchor depth,section size,expansion angle and anchor plug length）,FLAC-3 D（ a finite difference software） was used to studied the comprehensive influence of multi-factors of different parameters of the structure of the tunnel anchorage on the load bearing performance,with the certain amount of excavation,under the background of tunnel anchorage of a Yangtze River bridge building on mudstone. The results show that the maximum deformation displacement of the anchorage body is mainly related to the dimensions of the rear anchor,and the larger the size of the anchor,the better the bearing characteristics of the tunnel anchorage,when building shallow buried tunnel anchor on soft rock with low bearing capacity. Simultaneously,a group of anchor structure size parameters was obtained better than the original design. In addition,the simulation analysis of failure mode and process of built bridge anchorage system has been conducted,and the failure mode of anchor rock is that the anchor body be pulled out of the whole caused by surrounding rock rupture under lateral extrusion,to provide a reference for engineering.