地铁荷载作用下地裂缝邻近土体受力数值分析

Numerical Analysis of Stress in Soil due to Subway Moving Loads in Ground Fissure Area

利用有限元分析法,对西安穿越地裂缝带的地铁隧道与土体在地铁荷载下的动力相互作用进行了三维模拟,分析了整体式隧道和分段式隧道两种情况下衬砌与土接触压力的分布规律和衬砌下部土中动应力的传递规律及影响范围,并将地铁列车荷载引起的动应力与初始静应力进行了比较,得出了地铁动荷载与重力荷载之间的强度差异。分析表明,列车从上盘往下盘运行过程中,在地裂缝附近,下盘拱底与土附加接触压力较正常值大,上盘则较正常值小,下盘拱顶与土附加接触拉应力较正常值大,上盘拱顶与土之间则产生附加接触压应力;土中竖向动应力从衬砌底传递至下部11 m过程迅速减小,动应力对此范围以外的土体影响较小;地裂缝附近分段式隧道条件下土中竖向动应力较大;就本次模拟工况而言,地铁动荷载产生的动应力比初始静应力要小很多,初始应力与动应力的最小倍数在60倍以上。

The dynamic interaction between metro tunnel and soil under subway loads in Xi＇an ground fissure area is studied by finite element analysis,the simulation results such as the distribution laws of contact pressure between tunnel lining and soil,the transfer rules and influence scope of dynamic stresses in the soil below the tunnel lining are analyzed for integral tunnel and sectional tunnel. Then dynamic stress caused by subway moving load is compared with initial static stress,and the intensity difference between subway dynamic load and gravity load is studied. Analysis results show that,when the train moves from hanging wall to footwall,the additional contact pressure between footwall arch bottom and soil are larger than the normal values near the ground fissure,and they are smaller than the normal values at hanging wall; the additional contact tensile pressure between footwall vault and soil are larger than normal values,and it produces additional contact compressive stress between hanging wall vault and soil. The vertical dynamic stress decreases rapidly from the bottom of tunnel lining to its 11 meters below,and they have no significant effect on the soil outside of this range. The vertical dynamic stress in the soil near the ground fissure under the condition of sectional tunnel is much larger than the condition of integral tunnel. The dynamic stress caused by subway moving load is much smaller than initial static stress under this simulation condition,and the smallest multiple between initial static stress and dynamic stress is more than 60 times.