基于能量法的双线下穿既有隧道沉降研究

Analysis on Settlement of Existing Tunnel Induced by Twin Tunneling Underneath Based on Energy Method

针对双线隧道穿越施工造成的复杂影响问题,基于能量方法,提出了考虑地层损失率差异的双线下穿开挖作用下既有隧道沉降的计算方法。基于经典的Peck和Mair理论,在计算新建隧道开挖引起的地层位移时,引入Hunt双线开挖沉降修正系数,考虑双线隧道先后穿越引起的地层损失率差异性所造成的影响;基于Rayleigh-Ritz法和弹性地基梁理论,写出系统各部分功能关系式,建立系统总势能方程;利用变分法求解总控制方程,得到考虑地层损失率差异的双线隧道下穿引起既有隧道沉降的理论解析,并将理论计算结果与已有文献报道的工程实测沉降数据进行对比验证;以双线隧道下穿既有隧道为例,对双线中心间距、新建隧道直径以及新旧隧道净距展开参数分析。结果表明:理论计算结果与实测数据整体趋势一致,二者吻合较好,验证了所提方法的可行性;新建隧道先后下穿引起的地层损失率差异对既有隧道的沉降有显著影响;随着新建双线中心间距和新旧隧道净距的增大,既有隧道的沉降量随之减小;随着新建隧道直径的增大,既有隧道的沉降量随之增加,且第二次下穿施工产生的沉降影响会越发明显。研究成果可快速且合理评估既有隧道受新建隧道穿越施工影响时的纵向变形响应,对类似的双线隧道工程起到一定的理论支持和指导意义。

A study is conducted on the complex impact of twin tunneling.Utilizing the energy method,a calculation method is developed to assess the settlement of an existing tunnel induced by the excavation of twin tunnels below,considering variations in ground loss.This method integrates the modification factor for soil displacement above the twin tunnel construction,as proposed by Hunt,to account for the influence of ground loss differences based on the classical theories of Peck and Mair.The method combined the Rayleigh-Ritz method and elastic foundation beam theory to derive several expressions for energy and work within the entire system,and these are employed to establish the total potential energy equation.The method for calculating the settlement of the existing tunnel due to the twin tunneling underneath is obtained by solving the total governing equation using the variational method.The results are then compared to the measured data from an engineering case published in the literature.In an example where twin tunnels undercross existing tunnels,a parameter analysis is conducted,including the center-to-center distance between the twin tunnels,the diameter of the new tunnels,and the apparent distance between the new and existing tunnels.The research results showed that the calculated values generally align with the measured data in terms of overall trends,confirming the validity of the proposed method.The asynchronous construction of twin tunnels significantly impacts the settlement of the existing tunnel.As the center-to-center distance between the twin tunnels and the apparent distance between the new and existing tunnels increases,the settlement of the existing tunnel decreases.In contrast,as the diameter of the new tunnel increases,the settlement rises,and the impact of the subsequent undercrossing construction becomes more pronounced.The proposed method provides a quick and accurate evaluation of the longitudinal response of existing tunnels to new tunnel crossings,offering a theoretical foundation and practical guidance for related twin tunnel construction projects.