浅埋暗挖大跨风道临时支撑拆除技术

西南风道具有地质条件及周围环境复杂、开挖跨度大(开挖跨度9.9 m)、埋深浅(结构上覆土厚度约10 m)、覆跨比较小(约为1)、路面外荷载作用频繁、穿过地下管线等显著特点。风道采用CRD法开挖支护,其中,临时支撑拆除是CRD法的关键技术,若施工不当易引起大的地表沉降,影响地下管线和地面交通运行安全,为了保证施工安全及周围环境的安全,采取分段、逐层拆除的方法,主要介绍CRD法临时支撑拆除施工,并通过对地层变位的监控量测,对临时支撑拆除施工效应进行分析。研究表明:1)临时支撑拆除范围原则上取隧道跨度,当环境要求严格时,应减小拆撑的范围;2)拆撑施工引起的地表沉降值比较小,占地表总沉降值的5.86%～18.49%;3)制定和完善了临时支撑拆除控制标准,包括临时支撑拆除时机的确定、位移的控制基准等。

Dismantling Technology for Temporary Support of Large-span Ventilation Tunnel under Shallow Cover

There are lots of difficulties in the construction of southwest ventilation tunnel. The ventilation tunnel is con- strueted by CRD method. The dismantling of the temporary support is the key point in the control of the ground surface settlement and the security of the underground pipelines and the surface traffics. The temporary support is dismantled section by section and level by level, so as to guarantee the safety of the construction and the surrounding environment. The dismantling technology of the temporary support is presented in the paper. The dismantling effect is analyzed on ba- sis of the monitoring of the ground displacement. The study shows that ： 1 ） In principle, the range of the temporary sup- port dismantling is up to the span of the tunnel. Sometimes it should be narrowed when it is necessary. 2） The ground surface settlement induced by the temporary support dismantling is small, ranging from 5.86% to 18.49% of the total settlement. 3 ） The standard for the temporary support dismantling is established and improved.