地层膨胀力对盾构管片结构受力影响分析

Study on Influence of Stratum Expansion Force upon Stress State of Shield Segments

膨胀土具有显著的吸水膨胀和失水收缩、且胀缩变形往复可逆的特点,类似地层盾构隧道研究相对较少。针对成都地铁某盾构区间实例,根据盾构隧道埋深与盾构隧道外径关系进行分类,通过单一变化膨胀力,借助有限元软件采用壳单元建立荷载-结构模型计算各工况下管片的内力,对比分析管片内力和安全系数,研究膨胀力对盾构管片结构受力的影响。研究结果表明:随着隧道埋深的增加,地层膨胀力对管片结构受力表现为有利;可通过调整线路高程、增加盾构管片埋深、管片背后注浆等措施,降低地层膨胀力对管片结构受力的影响。

The expansive soil is prominently characterized by water swelling and dry shrinkage, and the swelling and shrinkage deformation is reversible over and over again. But the studies on shield tunnel in the similar strata were relatively fewer. For this reason in this paper, in combination with an actual example of shield tunnel on Chengdu Metro, the work conditions were classified according to the relationship between buried depth of shield tunnel and its diameter. And then through a single change of expansion force, a load-structure model was established by using shell element of finite element software, so as to calculate the internal force of every shield segment under different work conditions. By comparative analysis on shield segment internal force and safety factor, the influence of expansion force upon the stress state of shield segment was studied. The results of the study show that： （a） with the increasing of buried depth of the tunnel, the stratum expansion force is beneficial to the stress state of the shield segment; （ b） the influence of stratum expansion force on shield segment can be reduced by adjusting route elevation, increasing buried depth of shield segment, grouting behind the segment and by other measures.