砂卵石地层下伏膨胀岩土盾构隧道结构内力特征

摘要

The Chengdu metro line 2 partly passes through the complex strata of sandy pebble and expansive soil. In order to obtain the influence law of expansive force resulted from partial expansion on shield tunnel lining structure load in complex layers,the influence of partial expansion with various ranges and expansion forces on the contact pressure of tunnel lining structure was analyzed with a numerical method. Load distribution and internal forces of tunnel lining structure at the stage of grouting and after tunnel transfixion were obtained by field tests and compared with the calculated structural internal forces under different expansion loads. The research show that the expansion thickness and range have a little effect on the increment of pressure on the lining structure,but the expansion force has a great influence on the increment. The existence of partial expansion will increase the bending moment of segment and is harmful to the lining structure. The negative bending moment becomes the control factor of tunnel structure design in the complex layers. When structure internal forces in complex layers of sandy pebble and expansive soil are calculated,the influence of expansion load should be considered and it is better to use a numerical method to determine its value.%成都地铁二号线区间盾构隧道局部穿过砂卵石下伏膨胀岩土地层，为获得下伏地层膨胀荷载对盾构隧道衬砌结构内力的影响规律，采用数值方法分析了下伏地层在不同范围发生局部膨胀时对衬砌结构外侧压力的影响。通过现场测试得到了盾尾注浆时和隧道贯通后衬砌结构荷载及内力的分布规律，并与不同膨胀荷载下结构内力的计算结果进行了比较。研究表明：膨胀圈厚度及范围对膨胀后压力增量的影响较小，膨胀力对压力增量的影响较大；局部膨胀荷载的存在将增大管片结构弯矩，对结构受力不利，负弯矩是下伏膨胀岩土地层盾构隧道结构设计的控制因素。计算砂卵石下伏膨胀岩土地层中盾构隧道结构内力时，应考虑膨胀荷载的影响，膨胀荷载可采用数值分析等手段确定。