大直径盾构隧道管片纵缝三斜螺栓接头力学特性研究

Mechanical Properties of Three-inclined Bolts in Longitudinal Joint of Large-diameter Shield Tunnel Segment

基于精细化数值模型研究大直径盾构隧道管片纵缝三斜螺栓接头在不同轴压下的力学特性,揭示了接头裂缝分布情况、接头竖向位移、张开量、转角和抗弯刚度等参数随接头弯矩的变化规律。结果表明:在正弯矩的作用下,管片裂缝分布有受压裂缝、内缘手孔处沿宽度贯通拉裂缝、接缝面螺栓孔的拉裂缝以及侧边的斜裂缝,而受压裂缝和接缝面螺栓孔处的拉裂缝也存在于负弯矩作用下的模型;管片出现两条沿宽度方向贯通裂缝的现象,对应接头竖向位移、混凝土压应变和接头张开量3个力学特性曲线的拐点,曲线随弯矩增加由近似线性变化转为非线性剧变,混凝土出现压溃时接头转角变为非线性变化,轴力的增加会延迟裂缝贯通现象的出现;螺栓应力随接头弯矩呈线性增长阶段、非线性增长阶段和屈服阶段;螺栓应力增长速率受弯矩和轴力的影响,接头抗弯刚度初始无明显变化,随后呈非线性下降,轴力越大接头抗弯刚度越大。

A three-dimensional refined finite element model was established,which was used to investigate the mechanical properties of three-inclined bolts in longitudinal joint of large diameter shield tunnel segment under the effect of different axial pressures.The changes of the distribution of cracks,vertical displacement,joint opening,joint′s rotation angle,and bending stiffness were revealed.The results show that the cracks including the compressive cracks,through tensile cracks at the inner edge of the hand hole and the bolt hole on the joint surface,and oblique cracks at the side appeared in the segment under the action of positive bending moment.Whereas the cracks including compressive micro cracks and tensile cracks appeared at the bolt hole of the joint surface under the action of negative bending moment.The appearance of two cracks running through the width direction corresponds to the inflection point of the three mechanical characteristics curves,which includes the vertical displacement of joint,the compressive strain of concrete,joint opening,and rotation angle.The curve changed from approximately linear to nonlinear with the increase of bending moment.The joint′s rotation angle changed to a nonlinear change when the concrete was crushed.The increase of axial force could delay the occurrence of crack penetration.The change of bolt stress could be divided into three stages under the action of the bending moment of joint,i.e.,linear growth stage,nonlinear growth stage,and yield stage.The rapid growth rate of bolt stress was affected by the bending moment and axial force.The bending stiffness of joint had no obvious change at first,and then decreased.The increasing axial force made the bending stiffness of joint larger.