软土区轨道交通盾构隧道扩大内径的结构安全性研究

Safety Research on Shield Tunnel with the Extended Diameter in Soft Soil Area

随着运营期结构变形处治频繁及通行列车的大型化,软土区轨道交通盾构隧道现有设计内径难以满足界限需求。针对扩大内径后的管片环,复核其常规工况下的结构安全,认为:扩大内径后,管片环结构在常规工况条件下能够满足安全性要求。通过对其在多种特定工况条件下的结构状态进行计算和对比后建议:①施工方案的制定及实际操作中应采取措施避免和减少对隧道周边土层的扰动;②结构设计及运营期监护标准的制定须考虑特定工况,并严格限制隧道周边相关工程活动的间距及规模;③设计方案中,将接头尽量布设在45°区域、增大环间搭接量、接头螺栓加强及采用双排螺栓等措施可有效地减小管片环的收敛变形量;④增大管片厚度可在一定程度上减小管片环收敛变形,经济技术比选后,可适当增大管片厚度。

Because of the increasing treatment for segment ring and the maximization of train,current dimension of shield tunnel for rail transit in soft soil area is hard to meet the boundary demand of service space.For the segment ring with the extended diameter,the structural safety recheck shows that the segment ring would safe in conventional conditions.With the comparison of structural states for segment ring in some special conditions,some recommends are given as follows:(1)The ground disturbance should be avoided and reduced in the formulation of the construction scheme and the actual operation;(2)Special conditions should be taken into account in the structural design and the formulation of monitoring standards during service period,and the distance and scale of neighboring engineering should be limited strictly;(3)In the design scheme,the deformation of segment ring could becontrolled effectively by placing the joint in the 45°area as much as possible,enlarging the overlap of rings,strengthening the bolts in joint,and adopting double row bolts;(4)Increasing the segment thickness can reduce the convergence deformation of the segment ring to a certain extent.After economic and technical comparison,the segment thickness can be appropriately increased.