穿越地裂缝带地铁隧道结构应力预测方法研究

摘要

西安地处国内地裂缝发育最强烈的汾渭盆地,地裂缝的活动性会造成地铁隧道结构扭曲及衬砌面开裂并影响地铁的施工及安全运营,采用特殊材料制作几何相似比常数为1∶20的地裂缝与地铁隧道结构相互作用的隧道模型,通过对隧道模型结构应力监测数据与应力预测值进行对比分析揭示了地裂缝位错作用下隧道的变形破坏规律,并建立了地铁隧道结构应力的预测模型.试验结果表明:随着地裂缝位错量的增加,位于隧道结构上部的地裂缝上盘压力增加、下盘压力减小,位于隧道结构下部的上盘压力迅速减小、下盘压力持续增加;位于地裂缝下盘的隧道结构上部整体受拉而下部整体受压,位于地裂缝上盘的隧道结构上部先受压后受拉;位于地裂缝下盘的隧道结构沿纵向发生向下的弯曲变形致使其环向应变表现为拱底受压而拱顶和左右两拱腰均受拉的受力特点;指数平滑法对初始观测值的要求低且受异常值影响小可作为隧道结构应力预测的首选方法,当应力值达到预警值时进行报警采取适当的加固措施可保证地铁隧道的正常施工与安全运营.%Xi'an is located in Fenwei basin which is the most serious area of the ground fissure formation in China.Ground fissure's activity can cause the subway tunnel structure distortion and the lining surface crack,which directly affecting the subway construction and the safe operation.The tunnel model between the ground fissure and the subway tunnel structure with the geometric similarity ratio 1 ∶ 20 is made with special materials.Through the comparison of the stress monitoring data and the stress prediction value of the tunnel model,the deformation and failure law of the tunnel under the action of the ground fissure dislocation is revealed,and the prediction model of the structural stress of the subway tunnel is established.Test results show that with the increase of ground fissure displacement,the upper plate pressure in upper part of tunnel structure increases and the footwall pressure decreases,while the upthrown block pressure in lower part of tunnel structure decreases rapidly and the lower pressure continued to increase.The upper part of the tunnel structure which located in the footwall of ground fissure is under tension and the lower part is compressed,and the upper part of the tunnel structure which located in the upthrown block of ground fissure is firstly compressed and then pulled.Tunnel structures in the footwall of ground fissure along the vertical downward bending deformation results shows the arch bottom is compressed and the vault and the arch waist is tension.The exponential smoothing method can be used as the first choice for the prediction of tunnel structure stress which is affected small by the initial observations and outliers,the normal operation and safety operation of the subway tunnel can be ensured by taking appropriate measures when the stress value reaches the warning value.