New Ningde Baima port railway branch line tianchishan number 1 mountain tunnel and completed Hangzhou tianchishan tunnel belong to underpass existent passenger dedicated railway tunnel.New tianchi number 1 mountain tunnel(SDK2+373.06) and Hangzhou tianchishan tunnel(K765+0654.1)is 26.27 degree oblique.The distance between Shujiexian tianchishan number 1 mountain tunnel and existent tunnel inner rail top is 22.24m.The distance of turning arch lining between new tianchishan number 1 tunnel secondary lining vaults outer edge and the existent is 12.32m.When construct underpass tunnel,there is a security risk in the existent tunnel.

Commissioned by Project Manager of Ningde Baima porpot railway branch line of TieSanJu group second engineering Co., Ltd,we monitored existence Hangshenxian tianchishan tunnel K765+015-K765+085 on October 20, 2010 to January 28, 2011.The purpose of tunnel monitoring is to master formation stability rules according to the monitoring results,timely understanding of both the operation of the tunnel and the changing situation, predict accident and danger.New tunnel construction underpass in the subway tunnel and in the process of the highway engineering construction both had similar engineering examples,but the underpass in the existing high-speed railway construction monitoring in our country, the domestic first.In conjunction with the departments efforts,We overcome a lot of difficulties,through innovation in technology,completed the task of monitoring of the existence tunnel successfully.