three-arm drilling rig

As a new type of tunnel construction tool，the three-arm drilling rig is widely used in excavation，anchor construction and auxiliary operation of highway，railway tunnel，underground cavern excavation and other large section construction projects. This paper mainly combines the engineering practice

In the past days，while encountering bad geological conditions such as fault fracture zone or karst in rock class Ⅳ and Ⅴ sections，the traditional treatment method for tunnel is applying pipe roof and forepoling ducts first，then grouting those pipes and ducts to improve the tunnel stability