盾构千斤顶不良顶推作用下地铁管片衬砌开裂特性

Cracking Behavior of Segmental Lining in Subways Under Adverse Jacking Force During Shield Tunneling

为指导地铁区间隧道施工盾构掘进控制和管片衬砌防裂设计,建立考虑接头-管片的盾构隧道装配式衬砌结构数值模型,基于混凝土弥散开裂本构模型,研究直线段管片衬砌在千斤顶轴向倾斜以及千斤顶端面侧移两种不良顶推作用下管片衬砌的开裂特性.研究结果表明:在上述2种不良顶推力下,顶推导致的管片衬砌裂缝主要分为封顶块螺栓孔裂缝、手孔纵向裂缝和管片环面纵向裂缝3类;当千斤顶出现轴向倾斜致裂时,拱顶封顶块环向螺栓孔处的裂缝宽度最大,且当轴向倾斜角度达到3°时,3类裂缝宽度均已超过施工的允许值;当千斤顶端面侧移致裂时,衬砌环面及封顶块环向螺栓孔位置处的宽度最大,其中端面整体向下侧移是最为不利的情况;管片衬砌开裂将导致裂缝位置处钢筋应力增大,相同开裂位置处的钢筋应力-裂缝宽度关系基本不受顶推力倾斜角度变化的影响,裂缝的宽度与钢筋的应力呈正相关关系.盾构施工时,应严格控制盾构掘进不良顶推作用,对容易产生裂缝的位置建议加强配筋以控制裂缝的发生.

In order to guide the shield tunneling control and crack prevention design of segmental lining during the construction of subway section tunnels,a numerical model of the fabricated lining structure of shield tunnels considering joints and segments was established.Based on the constitutive model of concrete smeared cracking,the cracking behavior of linear segmental lining under the adverse jacking force caused by axial tilt and end face lateral displacement of the jack was studied.The research results show that under the above two kinds of adverse jacking force,the segmental lining cracks caused by the jacking force can be divided into bolt hole cracks in the key block,longitudinal cracks in hand holes,and longitudinal cracks in the annular surface of the segment.The crack width is the largest at the ring-direction bolt hole in the key block when the jack axis is tilted axially,and the width of the three types of cracks exceeds the construction limit when the axial inclination angle reaches 3°.The width is the largest at the annular surface of the lining and the ring-direction bolt hole in the key block when the end face of the jack laterally shifts.Specifically,the overall downward lateral displacement of the end face is the most unfavorable situation.The cracking of segmental lining will increase steel reinforcement stress at the crack location,and the relationship between steel reinforcement stress and crack width is not affected by the change of inclination angle of the jacking force.Furthermore,the crack width is positively correlated with the steel reinforcement stress.During shield construction,the adverse jacking force of shield tunneling should be strictly controlled.In order to control the occurrence of cracks,it is suggested to strengthen the reinforcement in the position where cracks are easy to occur.