Research On The Qiantang River Embankment Settlement Caused By The Large-Diameter Shield Construction

In the river-crossing tunnel construction,shield because of its unique characteristics of high quality,fast,safe and economic,become the first choice for the river-crossing tunnel construction.However shield inevitably will cause grout loss in the construction process,vary soil stress states,cause the ground movement and embankment settlement,threaten the safety and stability of embankment,cause great economic loss and social influence.Therefore,on the basis of previous studies,based on Hangzhou Wangjiang Road river-crossing tunnel shield construction,the paper conducts the research on the laws of embankment settlement caused by the shield under-passing The Qiantang River embankment.The main research content and conclusion of this paper include:(1)During the shield under-passing the Qiantang river embankment,it has four stages:preliminary settlement,shield through embankment,shield leave embankment,late period settlement.The stages of shield through and leave embankment account 80% percent of the total settlement.They're main stages.(2)Jiangnan embankment transverse settlement groove almost match normal distribution.The settlement of tunnel axis is biggest,and the settlement gradually decreases when it away from tunnel axis.And the settlement distribution shows symmetrical distribution along the tunnel axis,accord with the normal distribution curve by peck's theory.The distribution range of embankment transverse settlement groove is large,as large as 2 or 3 times shield diameter.The closer the embankment distance to the shield axis,the greater impact of the embankment settlement.The tunnel axis on both sides of the range of 6m and the range of the shield through embankment and the shield leave embankment 3D is main effect region caused by shield under-passing embankment.(3)By building 3D model of shield under-passing Qiantang river embankment,considering soil and shield construction,shield structure,numerical simulation of the shield under-passing the Qiantang river embankment.Comparing the measured results with the simulation's results,the results are almost same.And forecasting the settlement of Jiangbei embankment,verify the security and feasibility of the shield under-passing Jiangbei embankment.(4)Research on the influence of shield construction parameter to embankment settlement.We discover that with the excavation surface slurry pressure,grouting pressure,thickness of grout increasing and cutter torque,shield forces decreasing,the embankment settlement is decreasing.The excavation surface slurry pressure and grouting pressure impact to embankment obviously.On the basis of embankment settlement,it need change the shield construction parameter in time during the shield construction.Guaranteed the embankment is safe and stable.(5)Research on the influence of shield structure parameter to embankment settlement.We discover that with the thickness of covering soil increasing,shield diameter decreasing,thickness of segment increasing,the embankment settlement is decreasing.In particular,the thickness of covering soil and shield diameter are linearly related to the embankment settlement.(6)Research on the influence of soil parameter to embankment settlement.We discover that with the soil's modulus of elasticity,internal friction angle and cohesion increasing,the embankment settlement is decreasing.soil's modulus of elasticity is main parameter.When design the shield passing line,we should choose soft soil layer as less as possible.