薄基岩顶板隧道爆破施工围岩稳定性分析

Analysis of Surrounding Rock Stability during Blasting Construction of Tunnel with Thin Bedrock Roof

为更有效地进行薄基岩顶板条件下隧道施工安全控制,以某高速公路隧道为工程背景,运用数值模拟的方法,分别研究不同顶板厚度下隧道爆破施工引起的围岩振速分布特征及其对围岩的损伤情况,并进行围岩稳定性分析。结果表明:1)当顶板厚度在5 m及以上时,围岩是稳定的;2)当顶板厚度为3 m时,最危险横断面上基岩顶板内开始产生严重的拉伸裂缝及一些径向裂缝,将形成超挖;3)当顶板厚度≤2 m时,径向裂缝贯穿顶板岩体,围岩稳定性较差,在掌子面后1 m内可能发生塌落、掉块等事故。

In order to effectively control the safety of tunnel construction under the condition of thin bedrock roof,the vibration velocity distribution characteristics and damage of surrounding rock induced by blasting construction of a expressway tunnel are studied; and then the stability of surrounding rock is analyzed by numerical simulation method.The results show that: 1) When the thickness of tunnel roof is over 5 m,the surrounding rock is stable. 2) When the thickness of tunnel roof is 3 m,serious tensile cracks and some radial cracks would occur at the bedrock roof of the most dangerous cross-section,and which would lead to overbreak. 3) When the thickness of tunnel roof is less than 2 m,radial cracks would penetrate the roof rock,the stability of surrounding rock is poor,and collapse would occur to 1 m behind the tunneling face.