围压对错缝拼装管片衬砌结构力学性能的影响

Study on Influence of Confining Pressure on Mechanical Properties of Staggered Assembly Segment Lining Structure

为了探明围压对盾构隧道错缝拼装管片衬砌结构力学性能的影响,以苏通GIL电力管廊隧道为工程背景,采用"多功能盾构隧道结构体试验系统"对3种不同围压下的错缝拼装的管片衬砌结构进行了原型加载试验,从管片衬砌结构的内力、变形、纵缝张开、螺栓应变和主筋应变等方面研究了围压对管片衬砌结构的影响。研究结果表明:①围压变化对管片衬砌结构弯矩的大小和分布影响较小,而对轴力大小和分布影响较大,围压增大,管片衬砌结构的轴力分布更为均匀;②管片衬砌结构的形变呈现不规则的"椭圆形",围压增大可显著降低管片衬砌结构的整体形变,提高管片衬砌结构的稳定性;③围压增大有利于控制管片纵缝张开量,减小螺栓的应变;④围压的增大能够降低管片内侧主筋拉应变,但管片外侧主筋的压应力会随围压的增大而增大,使得正常使用阶段管片外侧主筋应力由压应力控制;⑤围压增大能够有效延长管片衬砌结构单点位移、纵缝张开、螺栓应变线性变化过程,延缓了管片衬砌结构进入塑性变形的时间;⑥高围压条件下管片结构处于高轴压受力状态,使得管片结构外侧受压钢筋应力增大,易造成钢筋屈服先于混凝土压溃发生,使管片结构抗压强度降低。在进行工程设计时,建议对高围压下管片结构的外侧受压钢筋进行加强设计。

To determine the influence of the confining pressure on the mechanical properties of the shield tunnel segment structure with staggered assembly,based on the engineering background of the Sutong GIL power gallery tunnel,the"multi-function shield tunnel structure test system"was used to carry out a prototype loading test on the segment lining structure with staggered assembly under three different confining pressures.Moreover,the influence of the confining pressure on the segment structure was studied according to the internal force,deformation,longitudinal joint opening,bolt strain,and main reinforcement strain of the segment structure.The results demonstrate the following:①The change in the confining pressure has little effect on the magnitude and distribution of the bending moment of the segment structure,but it has a greater influence on the magnitude and distribution of the axial force.As the confining pressure increases,the axial force distribution of the segment structure becomes more uniform.②The deformation of the segment structure exhibits an irregular"ellipse."The increase in the confining pressure can significantly reduce the overall deformation of the segment structure and improve its stability.③The increase in the confining pressure is conducive to controlling the opening amount of the longitudinal joint of the segment and reducing the bolt strain.④The increase in the confining pressure can reduce the tensile strain of the main reinforcement inside the segment.However,the compressive stress of the main reinforcement outside the segment will increase with an increase in the confining pressure,which means that the stress of the main reinforcement outside the segment is controlled by the compressive stress in the normal use stage.⑤The increase in the confining pressure can effectively extend the linear change process of the single-point displacement,longitudinal joint opening,and bolt strain of the segment structure,thereby delaying the time for the segment structure to enter plastic deformation.The research results have guiding and reference significance for the design of high water pressure shield tunnels.⑥Under the condition of a high confining pressure,the segment structure is in the state of high axial compression,which causes the stress of the reinforcement outside the segment structure to increase.This can easily result in the yield of the reinforcement prior to the collapse of the concrete and may reduce the compressive strength of the segment structure.The design of external compression reinforcement of the segment structure under high confining pressure in engineering design is suggested.