基于XFEM的平行近接施工致既有隧道衬砌开裂规律研究

On the Lining Cracking Mechanism of Existing Tunnels Caused by Parallel Construction Based on XFEM

为研究隧道致裂机理,以大岭山隧道为依托工程,通过建立扩展有限元法(XFEM)分析模型的方法研究在新建隧道爆破荷载下,既有隧道迎爆面上拱顶、拱腰、拱脚、墙腰和墙脚等五个部位的动态响应情况,对裂缝扩展的过程、不同部位裂缝的扩展比较和表面扩展裂缝宽度等不同角度进行分析,结果表明:在拱顶部位预设裂缝,裂缝两个尖端,一尖端向上扩展,另一尖端在拱顶内表面向迎爆面一侧扩展至外缘拱脚处,并最终形成完整的一块.新建隧道的爆破冲击波传播至既有隧道后,既有隧道的拱顶等五个部位的裂缝呈现不同的扩展规律.将预设裂缝口的张开位移等效为单元节点的相对位移,可见裂缝宽度均随爆破应力的增大而增大,裂缝宽度扩展速率随应力的增加而先增大后不变,裂缝扩展宽度对爆破应力的敏感度的减幅随着其与爆破作用面距离的增大而增大.

In order to study the mechanism of tunnel cracking,relying on the project of Daluoshan tunnel,the present paper investigated the dynamic response of the five parts of the existing tunnel,including the vault,the arch waist,the arch foot,the wall waist and the wall foot by building an Extended Finite Element Method(XFEM)analysis model so as to further analyze the process of crack propagation,the comparison of crack propagation in different parts,and the width of surface propagation cracks,etc.from different perspectives.The results show that a crack is preset at the top of the dome,one of its end expanding upwards,and the other end extending from the inner surface of the dome to the outer edge of the arch toe;finally a complete crack comes into being.After the blasting shock wave of the newly built tunnel propagates to the existing tunnel,the cracks in the vault of the existing tunnel and other five parts show different expansion patterns.The opening displacement of the preset crack opening is equivalent to the relative displacement of the element node.It is concluded that the crack width increases with the increase of the blasting stress,and the crack width expansion rate first increases and then remains fixed with the increase of the stress.The sensitivity of the crack propagation width to the blasting stress increases as the distance from the blasting surface widens.