爆破作用下隧道壁后空洞对衬砌的影响计算分析

Computation and Analysis of the Effects Induced by Voids behind the Tunnel Lining in Blasting Condition

随着我国工程建设活动逐渐增多,越来越多的岩土工程遇到了邻近既有隧道施工的情况。工程爆破产生的浅源地震波对既有隧道结构有着不利的影响,而在既有隧道存在壁后空洞的情况下,爆破振动造成的影响更加复杂且难以预估。通过开展邻近爆破条件下隧道衬砌结构的现场监测,文章基于现场监测数据建立了相应的数值计算模型,计算了掌子面爆破时初期支护与二次衬砌壁后空洞对衬砌振动速度的影响。通过对比有空洞和无空洞的初期支护振动速度计算结果,分析了爆源距离、壁后空洞位置以及壁后空洞尺寸等因素对壁后空洞爆破动载效应的影响,认为决定该效应的主要因素是爆源距离和壁后空洞高度;通过对比有空洞和无空洞的隧道二次衬砌振动响应,分析了壁后空洞对二次衬砌的影响,认为二次衬砌的振动响应受壁后空洞宽度影响较大。文章的分析结果可为邻近既有隧道爆破施工的影响控制和隧道壁后空洞风险分析提供有益的依据。

With the increase of transportation projects in China,more and more geotechnical engineering will encounter complicate situation,in which existing tunnel is near around.Shallow earthquake wave induced by engineering blasting would bring adverse effect to existing tunnel lining,and complicate and unpredictable consequences may be caused when voids behind tunnel lining are existed.In this paper,based on the in-situ test of tunnel lining in adjacent blasting condition,numerical models are established to acquire the vibration responses of tunnel initial support and secondary lining.Several factors,including the blasting distance,the location and the size of voids behind tunnel initial support layer,are analyzed by comparing the vibration velocities of tunnel initial support layer in normal condition and in void condition.The result shows that initial support layer’s void effect is mainly influenced by blasting distance and void height.Similar process is conducted on the void effect of secondary lining by comparing the vibration velocities of secondary lining in normal condition and in void condition,and it shows that lining vibration response is mainly influenced by void width.These conclusions can be helpful in vibration control and risk analysis of voids behind lining in the situation of blasting construction nearby the existing tunnel.