含壁后空洞盾构隧道管片安全分析

为探究空洞对盾构隧道的影响机理，通过建立考虑环、纵向接头的盾构隧道精细化数值模型，研究不同空洞深度、面积、位置等多种情况下管片内力、变形及截面安全系数的变化规律，并探讨管片不同拼装点位对含壁后空洞隧道的影响。研究结果表明：隧道壁后不同位置空洞对结构安全不利影响的排序为：隧腰>隧底>隧顶；空洞面积为5.0 m²时，随空洞深度增加，隧顶或隧底空洞中心处隧道截面弯矩及安全系数呈先减小后反向增大的趋势，且管片椭变先减小至0后反向增大，弯矩分别在空洞深0.3、0.2 m时反弯，左隧腰空洞中心处截面安全系数不断降低，管片椭变及弯矩大幅提升；空洞深度为0.5 m时，隧顶或隧底空洞中心处隧道截面弯矩均在空洞面积3.75 m²时反弯；空洞范围内存在纵缝会降低空洞中心处隧道截面内力并提升其安全系数，但其最大张开为空洞内无接缝时的2.0～3.5倍。研究成果可为盾构隧道壁后空洞安全评价、拼装点位选取提供参考。

Safety Analysis of a Shield Tunnel Segment with a Cavity behind Lining,Considering the Influence of the Joints

To explore the influence of a cavity on a shield tunnel, a refined numerical model of a shield tunnel, considering ringand longitudinal joints, is established. The variation law of the internal force, deformation, and section safety factor of the segmentare investigated under various conditions, such as the depth, area, and location of the cavity. Additionally, the influence ofdifferent assembly points of the segment on a tunnel with a cavity behind it is discussed. The results indicate that the order ofthe adverse effects of cavities at different positions behind the tunnel on structural safety is tunnel waist > tunnel bottom > tunneltop. When the cavity area is 5.0 m2, with an increase in the cavity depth, the bending moment and safety factor of the tunnel sectionat the center of the tunnel top or bottom cavity first decrease and then increase in the opposite direction, and the ellipticity ofthe segment first decreases to 0 and then increases in the opposite direction. The bending moment is reversed when the cavity depthwas 0.3 m or 0.2 m. The safety factor of the section at the center of the left tunnel waist cavity decreases continuously, and theellipticity of the duct piece and the bending moment increase significantly. When the cavity depth is 0.5 m, the bending momentof the tunnel section at the center of the cavity at the top or bottom of the tunnel is reversed when the cavity area is 3.75 m2.The existence of circumferential joints within the cavity reduces the internal force of the tunnel section at the center of the cavity and improves its safety factor. However, its maximum joint opening is 2.0–3.5 times that of a cavity without a joint. The resultsprovide a reference for the safety evaluation of the cavity behind the lining of a shield tunnel and the selection of assembly points.