大面积加卸载对软土地铁隧道的影响

选择HSS(Hardening Soil Small-Strain Model)本构,建立二维平面应变模型,进行既有软土地铁隧道上地表大面积加卸载情况下土体固结分析。研究结果显示:①大面积加载会增大衬砌结构的变形,并进而导致衬砌结构出现病害;②渗漏水会增大衬砌结构的内力;③回填土应及时卸除;④卸载后土体回弹,但有一部分变形无法得到恢复,回填土厚度越大,无法恢复的沉降越大;⑤在衬砌结构损伤的情况下,水平大直径卸载后无法恢复,最终表现为增长,根据曲线形态将沉降过程分为5个阶段。结合工程实例,对监测数据进行分析,验证上述结论。

Effects of loading and unloading large-scale area load acting on soft soil metro line

Hardening Soil Small-Strain(HSS) constitutive model was selected to establish two-dimensional plane-strain finite element model which can be used to investigate soil consolidation process in soft soil during loading and unloading within large-scale area for metro line construction.The results showed that: ①loading in large-scale area increases the deformation of the tunnel lining,and thus leads to lining damage;②leakage of the segments increases the internal forces of the lining;③backfill should be removed in time;④soil mass rebounds after unloading,but part of the deformation cannot be restored.The residual settlement which cannot be restored becomes larger when the backfill is thicker;⑤large diameter in horizontal direction cannot be recovered after unloading when the lining is damaged,and the final diameter extended.The settlement process was divided into five stages based on the subsidence curve shape.With practical example,the monitoring data was analyzed and the conclusions were verified.