采用玻璃纤维锚杆预加固掌子面软弱岩体的有限元分析和工程应用

The FEM Analysis and Application of NITM Tunnel Using GFRP Bolt as the Pre-Reinforcement of Front Rock of Tunnel

新意法的核心是通过对隧道掌子面前方核心岩体的预加固,控制掌子面水平挤出变形,确保掌子面的稳定,最终实现隧道的全断面开挖。玻璃纤维锚杆以其易于切削的优点成为新意法隧道的掌子面预加固主要方法之一。如何确定锚杆的加固密度、锚杆长度、锚杆的搭接长度和锚杆布置是设计和施工上的关键问题。针对浙江奇坑隧道的新意法施工,本文采用三维有限元数值模拟方法,针对新意法各施工工况进行计算分析,得到了锚杆密度、锚杆长度和锚杆搭接长度与掌子面挤出变形的关系;本文提出了采用隧道掌子面挤出变形的控制值作为隧道掌子面稳定性的评价依据,根据挤出变形的控制值来确定锚杆的相应设计参数;文章最后将现场监测结果和计算结果进行了比较分析,分析表明:计算和监测结果相当吻合,计算结果对施工具有实际指导意义。相信本文提出的论点和方法可供类似工程参考借鉴。

The philosophy of the new Italian tunneling method (NITM) is to keep under control the extrusion of tunnel workface and keep front rock stable by pre-reinforcement of front weak rock, and finally to achieve a full face excavation. Due to its being easy to break, the GFRP bolt has become one of the most important methods for the pre-reinforcement of tunnel face when tunneling with NITM. When applying GFRP, the density, length and overlap of the reinforcement constitute the parameters that characterize this reinforcement technique. Based on the application of GFRP bolt in the project of Qikeng Tunnel, Zhejiang province, this paper has obtained the relations between the extrusion and the design parameters of GFRP bolt using finite element method (FEM);this paper also suggests that the extrusion of tunnel face be taken as the index to judge the stability of tunnel face and the design parameters of GFRP bolts. This paper has carried out a comparison analysis between FEM results and site measurements, and the comparison shows that the FEM results agree very well with the site measurements and can be practical and instructive. The authors believe that the viewpoint and method mentioned in this paper shall be a good reference for the similar project.