Monitoring Analysis Of Retaining Structure Of Qingchunlu River-crossing Tunnel & Analysis Of Additional Stress Of Surrounding Soil Caused By Propelling Of Shield Tunneling

The Hangzhou Qingchun Road river-crossing tunnel is the first one that crosses beneath the famous Qiantang River, with the maximum digging depth of about 30 m as the deepest pit in Hangzhou. The successful construction of the Qiantang River tunnel project will have great radiation effects, which will greatly promote the design theory for underground engineering and construction technology in Hangzhou as well as the whole province.Based on the Hangzhou Qingchun Road river-crossing tunnel, in this paper, comprehensive analysis and research are conducted, from the investigation, design, monitoring and other aspects of the retaining structures for this deep foundation pit. The main work includes:(1) Introduce the design of retaining structure and the dewatering plan. The south work well is the deepest pit in Hangzhou, with the maximum digging depth of about 30 m. In this project, retaining structures of open cut plus underground diaphragm wall, open cut plus SMW method and steel support, open cut plus foundation reinforcement and open cut plus anchors-gunite-web shoring were adopted. In the pit at the north side, the retaining structures of SMW method plus steel support are mainly applied. The potential hazards posed by high-pressure water was successfully resolved by using the precipitation of bottom-sealing plus anti-seepage curtain and tube well supported by light well.(2) Monitor the horizontal displacements, axial forces, surface settlements and water levels. According to the analysis of monitoring data, some useful variations of the parameters are obtained, and they can be used as references for the design and construction of similar projects. For silt-based pit within excavation depth, it is significant to maintain the pit safety by effectively control the changes of water around the pit. The measured values of steel support axial force are much smaller than the design values, so it is necessary to optimize the preliminary design.(3) Deduce the formula and obtain the distribution rules of additional stress of surrounding soil versus angle, which is induced by bulkhead pressure and friction force during the propelling of shield tunneling.