盾构隧道壁后空洞注浆对管片受力特性的影响

Mechanics effects of backing void grouting on shield tunnel segment

为研究盾构隧道壁后空洞注浆浆液的扩散机理及其对管片受力的影响规律,基于修正达西定律对黏性土中浆液的扩散半径和管片产生的压力计算公式进行了推导,并以西安地铁某区间隧道涌水事故为依托,利用推导的注浆压力公式,采用地层-结构模型得到了管片壁后空洞注浆部位及注浆压力对管片受力的影响规律。结果表明：同一注浆位置,当注浆压力不断降低时,管片的轴力值、弯矩值以及管片上浮呈不断降低的趋势;除了控制截面有稍微旋转之外,设计工况下的管片轴力值、弯矩值与模拟过程中注浆压力为0.3 MPa时的情况相近,注浆压力超过0.9MPa时,结构产生明显的偏压,甚至出现管片裂缝以及结构破损;不同注浆部位施加相同注浆压力时,当注浆位置为隧道顶部和底部时,管片的力学形态发生了较大的变化,特别是弯矩值,增加幅度可达1.5-2倍,隧道侧面注浆使弯矩分布发生一定程度的旋转,甚至反转。

To study diffusion mechanisms and effects of the backing void grouting during shield tunneling in cohesive soil stratum, computational formulas for the diffusion radius of grout and pressure on the segment were derived from the corrected Dacy＇s Law. Based on a shield tunnel of Xi＇an metro, the mechanics effects of the grouting location of void behind the liner and the grouting pressure on the segment were ob tained using the computational formulas of grouting pressure and the layer-structure model. The research results show that the axial force, moment and segment floating displacement in the same position of void decrease with the grouting pressure decreasing. The axial force and moment in the design condition are similar to that under the grouting pressure 0.3 MPa, except that the control section produces small angle of rotation. The bias-pressure phenomenon and crack appear when the grouting pressure is over 0.9 MPa. Grouting on the top and bottom of the tunnel has a big impact on the segment mechanical form when the same grouting pressure is applied in different parts of the void. The value of the moment of the cross section increases approximately 1.5-2 times. And the section controlled by the moment is inclined to spin or even reverse because of the grouting beside the tunnel.