Research on Construction Technology of Drainage Hole Passing Under the Tunnel at Small Clear Distance in Karst Areas
Karst development occurs in the southwestern region,and surface water and groundwater are often connected by karst gaps.In order to effectively solve the problem of a large amount of water inflow in the Shiziyuan Tunnel during the rainy season,which affects the safety of subsequent railway operation,combined with the completion of the lining of the main tunnel on site,a drainage hole is added to concentrate the karst rich water and surface recharge water around the tunnel to the drainage hole and discharge it outside the tunnel.The newly added drainage hole needs to pass through the main tunnel.This article elaborates on the construction technology of the newly added drainage hole that passes under the main tunnel section at small clear distance in karst areas,including section optimization of the underpass section of drainage tunnel,advanced geological prediction,advanced support for large pipe sheds,non explosive excavation of small steps,surrounding rock grouting reinforcement,strengthening support and monitoring measurement,etc.Among them,two patented technologies(self advancing hollow anchor rod grouting head and locking foot anchor pipe angle control device)are used for strengthening support.By adopting these technical measures,the sinking of the lining structure of the main tunnel has been controlled,ensuring construction safety and achieving the functional use of newly added drainage tunnels and existing tunnel lining.The relevant experience is worth learning from.
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