宁波软土地区地铁联络通道冻结法工后长期运营沉降预测研究

Study on the Long-term Operation Settlement Prediction of Subway Connection Channel in Soft Soil Area of Ningbo after Freezing Construction

宁波地区主要以海相淤泥质黏土或淤泥等软土为主,此类土具有含水量大、压缩性高、承载力低的特性,地铁围岩开挖施工面临垮塌、变形问题,冻结法施工往往是处理上述问题的有效方法。然而,地层解冻后注浆作业不及时、注浆效果差极易导致地层沉降,所以需要对地基沉降进行长期监测。为更好考虑软土地基下的隧道安全,以宁波句章路站-鄞州客运总站站-南部商务区站区间盾构隧道为例,采用冻结法对宁波句章路站-鄞州客运总站站区间1#联络通道进行施工,开展冻融工后联络通道长期运营沉降预测研究,并通过三维有限软件MIDAS/GTS建模,对其冻融沉降进行计算分析。根据布点及实时观测,对隧道及句鄞区间盾构隧道及1#联络通道开挖施工期间的结构沉降变形及长期运营沉降变形进行预测,预测结果与监测数据基本一致,对于软土地基冻融处理具有重要工程意义,同时也可为相关工程提供借鉴。

Ningbo area is mainly composed of marine silty clay or silt and other soft soil,which has the characteristics of large water content,high compressibility,low bearing capacity.Surrounding rock excavation during subway con-struction is usually faced with collapse,deformation problems,the freezing method is often an effective way to deal with the above problems.Therefore,freezing method is widely used in the construction of urban subway projects in such silty strata.However,after thawing the ground,the grouting operation is not timely and the grouting effect is poor,which is easy to lead to the formation settlement,so it is necessary to carry out long-term monitoring of the foundation settlement.In order to better consider the tunnel safety under soft soil foundation,taking the shield tunnel between Ningbo Guzhanglu Station-Yinzhou Terminal Station-Southern Business District station as an example,a-dopts freezing method to construct the No.1 contact channel between Ningbo Guzhanglu Station and Yinzhou Termi-nal Station,and carries out the research on the long-term operating settlement prediction of the contact channel after freezing-thawing construction.The settlement was calculated and analyzed by MIDAS/GTS modeling.Based on the distribution and real-time observation,the structure settlement deformation and long-term operation settlement de-formation during the excavation of the tunnel and the Yingrong section of shield tunnel and the 1#contact channel are predicted.The predicted results are basically consistent with the monitoring data,which has important engineer-ing significance for freeze-thaw treatment of soft soil foundation,and can also provide reference for related projects.