既有隧道下的隧道施工引起的沉降评价

既有隧道下的隧道施工引起的沉降日益受到比以往更多的关注。由于在这些基础设施（建筑地面,砌体地下隧道,管道和其他设施）下的隧道施工在过去几十年隧道施工对现有基础设施建设的损害已经产生。基于Mair的理论分析和确定在既有隧道下新隧道施工引起的地面沉降和地面体积损失之间关系。由方程和三维有限元数值模拟确定地面沉降。计算现有隧道因新隧道施工引起的最大沉降。通过使用三维有限元分析,提出因隧道施工导致现有隧道的沉降和地面体积损失的控制方法。在新隧道施工之前使用大管棚（LPS）增强技术,通过与不使用LPS增强技术的情况进行比较,从而对使用LPS增强技术对地面体积损失控制的效果进行评价。结果表明LPS增强技术可以显著减少新隧道施工导致现有隧道的沉降,地面损失方法被证明是估计LPS增强效应的有效途径。

Tunneling-Induced Settlement Evaluationfor Underneath Existing Tunnel

Tunneling-induced settlement underneath existing tunnels has attracted more attention than ever before. Damages have been produced with existing infrastructure construction（buildings above ground, masonry tunnel underground,pipelines and other facilities）due to the construction of tunnels un- derneath these infrastructures during past decades. The relationship between subsurface settlement and ground volume loss caused by the excavation of a new tunnel underneath the existing tunnel was analyzed and identified based on Mair＇ s theory. The subsurface settlements are determined by equations and 3-D finite element numerical modeling. The maximum settlement of the existing tunnel caused by the construc- tion of the new tunnel was calculated. The settlement and ground volume loss control measurements for the tunneling-induced settlements in the existing tunnel were proposed and demonstrated by using 3-D finite element analysis. The large pipe-shed （LPS） enhancement was used prior to the excavation of new tun- nel. The effects of using LPS enhancement on ground volume loss control were evaluated by comparing withnon-LPS enhancement tunneling situations. The results indicate that the LPS enhancement can signifi- cantly reduce the settlement of an existing tunnel caused by the excavation of a new tunnel, and the ground volume loss method has proven to be an effective approach to estimate the effects of LPS enhance- ment.