公路隧道预设计中系统锚杆配置范围的研究

目前工程类比法被广泛的应用于公路隧道工程设计中,然而部分工程类比的系统锚杆设计与人们在不断的探索与大量的实践中认识到的规律存在较大的分歧与矛盾。分别对公路隧道系统锚杆在硬岩、软岩以及松散土砂中的作用机理和主要作用效果进行研究,并以此为依据,得出不同的研究结论:①在块状硬岩与水平走向的层状硬岩中,锚杆主要为悬吊和缝合固定的作用,分别以提高围岩的内摩擦角和组合梁效应为作用机理,并提出在硬岩中系统锚杆采用局部设置和拱部设置的设计方案;②软岩中系统锚杆以注浆加固、形成承载拱为主要目的,以提高围岩的内聚力,降低承载拱高度为作用机理,并提出在软岩中系统锚杆应在除仰拱外的全断面设置的设计方案;③土砂围岩中,拱部覆土多为不稳定土体,且塌落高度较大,锚杆应以锁脚和稳定掌子面为主要目的,设计方案应以加强支护结构为主,取消或减少拱部系统锚杆,以降低工程造价和尽早地闭合支护结构。

A study of the distribution range of system anchors in highway tunnel pre-design

At present,engineering analogy is widely used in highway tunnel design.With the development of understanding of system anchors,some analogy designs are found incorrect.Based on a study of the working mechanism of system anchors,conclusions are as follows.Anchors in blocked hard rock are usually for supporting those unstable rock blocks with an increase of the internal friction angle of the rock.Anchors in horizontal stratified hard rock are employed mainly to fix the lining and the rock,and they will work together as a composite beam.It is proposed that system anchors should be installed considering the joints and cracks of the blocked hard rock mass or installed on the tunnel vault when the joints are not clear in stratified hard rock.System anchors in soft rock can increase the cohesion by grouting,promote the formation of bearing arch,and thus should be installed in the entire section except the bottom.Anchors in loose sand are studied,which can strengthen the invert of the tunnel lining and the work face.A reinforced lining should be adopted and system anchors in the tunnel vault should be cancelled or reduced to reduce cost and make the lining closed as soon as possible.