上方开挖时压顶梁对箱形地铁区间隧道纵向变形的控制效果

Control Effect of Capping Beam on Longitudinal Deformation of Box Interval Metro Tunnel During Excavation Above

广州市白云公园—飞翔公园站明挖箱形地铁区间隧道出现了变形缝开裂等病害。基于荷载-结构法,运用MIDAS/Fea有限元软件建立三维数值模型,分析上方连接通道开挖时箱形地铁隧道的纵向变形规律,从而解释病害的原因。针对该类病害问题,在数值模型中增设压顶梁,研究压顶梁对箱形隧道纵向变形的控制效果。结果表明:若不采取抗隆起措施,隧道上方开挖深度较大时变形缝两侧箱体的差异沉降较大,易造成隧道结构开裂,发生渗漏水等病害;设置压顶梁后,箱形隧道最大隆起量为无压顶梁时的11%;压顶梁能有效抑制箱形隧道底板脱空。

There are diseases including deformation joint cracks in the box interval metro tunnel excavated openlybetw een Baiyun Park station and Feixiang Park station. Athree- dimensional numerical model was established byusing MIDAS /Fea f inite element softw are based on load- structure method. The longitudinal deformation rule for boxmetro tunnel was analyzed during the connection channel excavation above, which explained the cause of thedisease. According to this kind of disease problem, the capping beam was added in the numerical model and thecontrol effect of the capping beam on longitudinal deformation of box tunnel was studied. The results show that thesettlement difference betw een the boxes on both sides of deformation joint is huge with large excavation depth abovethe tunnel if the ant- uplift measures are not taken, which may cause the diseases such as tunnel structure cracks andw ater leakage. The maximum uplift capacity of box tunnel w ith capping beam is 11% of that without capping beam,w hich indicates that the capping beam can effectively prevent the drop of box tunnel floor .