盾构隧道纵向等效抗扭刚度与抗扭性能研究

Longitudinal equivalent torsional stiffness and torsional performance of shield tunnel

盾构隧道因具有拼接特性,在非对称外荷载作用下易产生纵向不均匀扭转。过量的不均匀扭转将导致管片和螺栓产生较大应力和变形,并发生环缝错位和轨道倾斜,严重影响隧道安全,但目前工程界对隧道扭转问题的认识和关注仍不足。为研究盾构隧道纵向抗扭性能,首先,基于等效连续化模型和力平衡方程,推导不同受力组合状态下的盾构隧道纵向等效抗扭刚度计算方法;其次,将抗扭刚度的解析解与有限元模拟结果进行对比,验证提出的抗扭刚度解析方法的有效性。最后,分析管片厚径比、宽径比、螺栓剪切长度以及隧道纵向轴力和弯矩等对抗扭刚度的影响,并给出隧道自抗扭临界荷载(N0,M0)包络图。研究结果表明:隧道纵向抗扭刚度有效率随着管片厚度与直径之比增大而减小,而随着管片环宽与直径之比增大而增大;盾构隧道纵向抗扭刚度有效率随着螺栓的等效剪切长度增大而减小;螺栓等效剪切长度仅影响环缝的扭转变形,而对接缝中性轴、扭转中心位置等没有影响;盾构隧道纵向抗扭刚度有效率随着压扭比或弯扭比增大而增大。设计中控制合理的压扭比与弯扭比对隧道抗扭十分重要。建议将螺栓增大预紧力或采用预应力管片结构视为提升盾构隧道抗扭性能的有效措施。

Shield tunnel which is subjected to the asymmetric loading inevitably suffers from uneven longitudinal cross-section torsion due to its segmental nature.The uneven cross-section torsion causes additional stress and deformation in segment and bolts and further induces the misalignment of circumferential joints,which is harmful to the safety of tunnels.However,the effect of longitudinal cross-section torsion on segmental tunnel has not received enough attention.In order to study the longitudinal torsional performance of shield tunnel,firstly,the longitudinal torsional stiffness of the shield tunnel subjected to different stress combinations is deduced based on the equivalent continuous model and force balance equation.Secondly,the validity of the analytical solution was verified by comparing it with the finite element results.Finally,the effects of thickness to diameter ratio,width to diameter ratio,shear length of bolt,longitudinal axial force and bending moment of tunnel on torsional stiffness were investigated.Besides,the envelope curve of tunnel active-torsion-rejection critical load(N0,M0)was given.The results show that the longitudinal torsional stiffness efficiency(LTSE)of shield tunnel decreases with the increase of segment thickness to diameter ratio,but increases with the increase of segment ring width to diameter ratio.The LTSE decreases with the increase of the effective shear length of the bolt.Besides,the variation of the effective shear length of bolts leads to the change of torsional deformation of the circumferential joint,but it does not change the location of the neutral axis and torsional center.The LTSE increases with the increase of the ratio of compression-torsion or bending-torsion.Thus,it is vital to set reasonable compression-torsion and bending-torsion ratios in tunnel anti-torsion design.It is suggested that bolts with preload or prestressed segments should be regarded as effective measures to improve the torsional performance of shield tunnel.