水工隧洞Ⅳ类围岩拱架段爆破开挖超挖控制

Overbreak Control During Blasting Excavation of Class Ⅳ Surrounding Rock Arch Section of Hydraulic Tunnel

爆破开挖是水工隧洞开挖中最常见的开挖方法之一,由于隧洞开挖围岩岩性的不确定性,通常围岩岩性较差时,需要采用钢拱架、锚网喷联合支护。为确保施工安全,钢拱架支护要求紧跟掌子面,由于钢拱架的影响,隧洞开挖时,周边孔钻孔角度与隧洞轴线形成夹角,隧洞成型开挖超挖控制难度增大,易造成孔底部位超挖增大。控制隧洞开挖成型质量、减少超挖对工程成本控制有着重要意义。如何减少孔底超挖,成为工程亟待解决的问题。

Blasting excavation is one of the most common excavation methods in hydraulic tunnel excavation.Due to the uncertainty of the lithology of the surrounding rock during tunnel excavation,it is usually necessary to use a combination of steel arch and anchor mesh spray support when the lithology of the surrounding rock is poor.To ensure construction safety,steel arch support is required to closely follow the working face.Due to the influence of steel arches,during tunnel excavation,the drilling angle of the surrounding holes forms an angle with the tunnel axis,making it more difficult to control the overbreak during tunnel formation and excavation,which can easily lead to an increase in overbreak at the bottom of the hole.Controlling the quality of tunnel excavation and reducing overbreak is of great significance for engineering cost control.How to reduce overbreak at the bottom of the hole has become an urgent problem to be solved in engineering.