盾构隧道管片施工阶段力学行为的三维有限元分析

管片是盾构隧道最基本的结构单元,与正常使用阶段相比,管片在施工阶段承受的荷载及相应的力学行为均有较大差异。从工程经验可知,管片开裂多发生在施工阶段,因此对管片在施工阶段力学行为的研究尤为重要。采用三维有限元法,利用通用有限元软件ADINA,建立一段具有9环管片的盾构隧道数值模型。通过加入与施工阶段相对应的注浆压力、千斤顶顶力及初步引入盾尾刷的挤压作用,分析盾构隧道的变形特点及应力分布。分析结果表明,在施工阶段,管片外荷载沿隧道纵向的差异使管片环的位移及应力沿隧道纵向产生变化,各环变形的特征也不相同。由于楔形块构造的原因,使得在均匀的注浆压力下,管片环仍然出现平面外的位移,并造成一定的错台量。若注浆压力不均匀,错台量将增大,甚至能造成管片开裂。千斤顶顶力对施工阶段管片的位移、应力有明显的影响,千斤顶顶力作用是管片在施工状态下最不利的工况。

THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF MECHANICAL BEHAVIORS OF SHIELD TUNNEL SEGMENT DURING CONSTRUCTION

Segments are the basic structure units in shield tunnel.The loads and relative mechanical behaviors of segments are different between construction stage and regular service stage.The cracks usually appear in construction stage,which hit the research on mechanical behavior of segments in construction stage more important.Three-dimensional finite element method is used to analyze a tunnel with 9 segment rings.The loads include injected pressure,jacking force and squeezing action of tail of shield machine.The analytical results indicate that,during construction stage,the difference of loads along longitudinal direction causes various displacements and stress distributions in different segment rings;and the displacements of different rings show discrepant.The constitutions of wedge-shaped segments make the out-of-plane displacement happen in segment rings even in uniformly injected pressure.The out-of-plane displacement causes the dislocation of segments.When the injected pressure is nonuniform,the dislocation will be enlarged,and it will finally cause cracks in segments.The jacking force has apparent effects on displacement and stress distribution of segments,and it is the most adverse load case during construction stage.