深埋超大跨单拱隧道开挖与支护参数优化研究

研究目的:基于新建京张铁路八达岭4线隧道超大跨、超大断面单拱的特点:跨度达27.3 m,高度达18 m,断面面积为386.56 m2,如此大的单跨在国内尚属首例,在开挖过程中,拟定四种开挖方案:单侧壁导坑法、单岩柱法、CRD四洞法和CRD六洞法。利用有限元软件对四种开挖方案进行数值模拟开挖和支护全过程仿真计算,得到最优的开挖方案。研究结论:通过在开挖支护过程中对围岩最大拉压应力、拱顶沉降、地表沉降、锚杆轴力、衬砌最大拉压应力等7个指标参数的比较,提出优化的开挖方法为单侧壁导坑法,其次是CRD六洞法,并且采用0.3 m厚的喷射混凝土衬砌和5 m长的锚杆(间距1.5 m×1.0 m)作为支护参数。该结论对设计施工具有指导意义。

Study on Optimization of Excavation and Support Parameters for Deep-buried Super-large Span Single-arch Tunnel

Research purposes: The Badaling Four-line-way Tunnel of the new Beijing-Zhangjiakou Railway is the first tunnel with so large span in China,featured with the span of 27.3 m,the height of 18 m and the cross section area of 386.56 m2.For excavation,the following four excavation methods were planned: the single-wall pilot method,the single rock column method,the CRD four-hole method and the six-hole CRD method.The finite element software was used to make the simulation calculation of the excavation and support processes with the four methods mentioned above for the purpose of getting the optimal construction scheme. Research conclusions:From the comparison of the seven parameters of the maximum drawing and compressive stresses,the vault settlement,the ground settlement,the axial force of the anchor arm and the maximum drawing and compressive force of the lining,it can be seen the single-wall pilot method is the optimal excavation method,followed by six-hole CRD method,based on taking the 0.3 m thick spraying concrete lining and 5 m long anchor arm as the support paramters.The research result is reasonable and has the reference to the design and construction.