Tracking of horizontal alignment of the long and large diameter uncharged hole in NATM tunnel  

作　　者：Min-Seong Kim Sean Seungwon Lee 

机构地区：[1]Department of Energy and Resources Engineering,Chonnam National University,Gwangju 61186,Republic of Korea [2]Department of Earth Resources and Environmental Engineering,Hanyang University,Seoul 04763,Republic of Korea

出　　处：《Underground Space》2024年第3期18-28,共11页地下空间（英文）

基　　金：supported by the Korea Agency for Infrastructure Technology Advancement(KAIA)grant funded by the Ministry of Land,Infrastructure,and Transport,South Korea(Grant No.22UUTI-C157786-03).

摘　　要：The long and large diameter uncharged hole boring(LLB)method is a cut blasting method that minimizes blast-induced vibrations by creating long and large diameter uncharged holes at the excavation face of tunnels prior to tunnel excavation.Drilling in this method typically uses a 50 m long with a 382 mm diameter hammer bit in the horizontal direction at the tunnel face.However,the significant weight and uni-directional rotation of the rod head,as well as variables such as geological characteristics,machine conditions,and inexperienced operators result in significant deviation from the target borehole alignment that hinders the vibration-dampening effect of the uncharged holes.Furthermore,since there is no method to verify the alignment of the boreholes until main tunnel construction,borehole misalignment is often not discovered until weeks after construction,which requires tunnel construction to cease until the equipment can be remobilized and an additional borehole be created,causing significant delays and increased costs for the entire tunnel project.In this study,the borehole alignment tracking and ground exploration system(BGS)is developed to predict and monitor the quality and alignment of boreholes for cut blasting methods such as the LLB methods immediately after boring.The BGS was subsequently tested at a subway construction site to evaluate its performance in the field.The measurements yielded by the BGS were compared with manually measured boring positions at every 5 m along the borehole.Although the BGS showed a maximum deviation of approximately 12%at a local point where the hole surface was relatively rough,the accuracy for the final boring position was approximately 97%,demonstrating excellent precision of the alignment tracking system.The BGS demonstrates excellent performance in predicting ground conditions and the boring quality of a cut hole immediately after drilling,and shows promise in various other applications for monitoring borehole alignment.

关 键 词：Tunnel blasting LLB method Drilling deviation Vertical sagging Horizontal alignment tracking BGS 

分 类 号：U45[建筑科学—桥梁与隧道工程]