地铁盾构隧道近距离上穿既有线路纵向变形计算方法

Calculation method of longitudinal deformation of metro shield tunnel overpassing existing line at short distance

针对新建地铁盾构隧道近距离上穿施工引发运营地铁线路不均匀变形问题,将既有线盾构管片视为一系列位于Pasternak基础上由拉伸弹簧、压缩弹簧和剪切弹簧连接的弹性地基短梁,考虑了管片间转动效应和剪切效应以及管片与土体相互作用,建立了基于Mindlin理论的新建盾构隧道施工引起的附加应力以及基于最小势能原理的既有隧道纵向变形的计算方法。结合实测数据与已有方法对比,验证了方法的适用性,并根据工程实例,采用该方法对影响纵向变形的管片连接、土体力学参数、新线与既有线相对位置参数及加固效果进行了分析。结果表明:新建隧道施工至上穿部位时摩擦力f和注浆压力p对既有隧道变形影响较大,穿越既有隧道后纵向变形主要受卸荷附加应力F影响;随着管片间剪切刚度ks、抗拉刚度k T增大,既有线路隆起变形减小,其中ks影响相对较大,工程中可从增强ks和kT的角度控制隧道变形;环形支撑加固措施能有效控制既有线纵向变形,且环间距1.5 m、交叉点左右各3~5环可取得良好效果。

In view of the uneven deformation of the operating subway line caused by the short-distance upward crossing construction of the new subway shield tunnel, the shield segments of the existing line are regarded as a series of short elastic beams connected by the tension spring, compression spring, and shear spring on the Pasternak foundation. The rotation effect and shear effect between segments and the interaction between segments and soil are considered, and a method is developed for calculating the additional stress caused by the construction of new shield tunnel based on Mindlin theory, and the longitudinal deformation of the existing tunnel based on the principle of minimum potential energy. The applicability of this method is verified by comparing with the measured data and the existing methods. According to the engineering example, the proposed method is used to analyze the influence of the segment connection, soil mechanical parameters, relative position parameters between the new line and the existing line and the reinforcement effect on the longitudinal deformation of metro shield tunnel. The results show that the friction force f and grouting pressure p heavily affect the deformation of the existing tunnel when a new tunnel is constructed to the upper crossing part, and that the longitudinal deformation is mainly affected by the unloading additional stress F when the new tunnel passes through the existing tunnel. With increasing shear stiffness ks and tensile stiffness k T, the uplift deformation of the existing line decreases, and ks has a relatively greater influence. The tunnel deformation can be controlled by enhancing the values of ks and k T, and the ring support reinforcement measures can effectively control the longitudinal deformation of the existing line, and the ring spacing of 1.5 m and 3-5 rings around the intersection point can achieve good results.