逆断层错动作用下地铁隧道结构损伤分析

Damage Analysis on Subway Tunnel Structure under Effect of Reverse Fault Dislocation

以乌鲁木齐地铁隧道穿越西山活动逆断层工程为例,建立三维弹塑性有限元模型.首先模拟分析了逆断层错动作用下隧道二次衬砌塑性应变发展过程,拉压损伤因子、剪切应变的横向及纵向分布规律,计算了混凝土的裂缝宽度;其次研究了不同错动位移、隧道底部距围岩交界面不同垂直距离及不同破碎带宽度的结构损伤规律,最后进行了设置柔性接头的减灾效果研究.结果表明:二次衬砌结构破坏首先出现在拱顶;然后是拱底,最后在拱腰处累积.破裂面附近拱腰处发生拉压剪的共同破坏;远离破裂面上盘拱顶,破碎带拱底处发生受拉破坏;远离破裂面上盘拱底,破碎带拱顶处发生受压破坏.基于混凝土裂缝得到隧道拉裂破坏的严重与轻微受损区分别为10 m和30 m.错动位移越大,结构受损越严重;隧道底部距围岩交界面垂直距离越大,土层越厚,耗散能量越多,结构受损越轻;破碎带宽度越大,隧道破坏越严重,当破碎带宽度达到26 m时,破碎带宽度对隧道的影响基本保持稳定.设置柔性接头可以显著降低结构的损伤,基本满足在设防错动位移下的设计要求.

Taking the subway tunnel in Urumqi crossing Xishan reverse active fault as an example,a three-dimensional elastic-plastic finite element model of soil-tunnel structure was established to simulate and analyze plastic strain development process of secondary lining,transverse and longitudinal distribution of tensile damage factor,compressive damage factor and shear strain,calculate the crack width of concrete under the action of reverse fault dislocation.Then the damage law of the tunnel structure with different dislocation displacements,different vertical distances from tunnel bottom to the interface of surrounding rocks and different widths of fault zone was studied.Finally,the disaster reduction effect of the flexible joint was studied.Results show that the damage of secondary lining first appeared in the vault,then the bottom,and finally accumulated at the waist.The shear,tensile and compressive damage all appear at the tunnel waist of the rupture surface.When the tunnel structure is away from rupture surface,the tensile damage appears at the tunnel vault of hanging wall and invert of fault zone,the compressive damage appears at the tunnel invert of hanging wall and vault of fault zone.The severe and slightly tensile-crack damaged length are 10 m and 30 m respectively based on the crack width of concrete.The larger the fault displacement is,the more serious the structural damage is.The larger the vertical distances from tunnel bottom to the interface of surrounding rocks,the thicker the soil is,resulting in that more energy is dissipated and the structural damage is lighter.The damage to tunnel increases with the increase of width of fault zone,but when the width increases to 26 m,the influence of width of fault zone on tunnel damage becomes stable.Setting flexible joints can significantly reduce structural damage and substantially meet the design requirements for fault displacement.