中老铁路沙嫩山隧道大变形区段松动圈发展规律及控制技术

Development Laws and Control Technologies of Broken Zone of Large Deformation Section in Shanenshan Tunnel of China-Laos Railway

通过现场测试隧道围岩变形分析中老铁路沙嫩山隧道大变形特征及围岩松动圈范围。结果表明:隧道大变形以水平收敛为主,存在拱架弯折、喷射混凝土剥落、掌子面溜塌等变形破坏现象,变形主要位于拱顶及拱腰;单线段、双线段隧道围岩松动圈范围分别在6.0~6.5、8.0~9.0 m,均达到隧道设计跨度的58%以上。根据测试分析结果,从主动控制隧道变形出发,考虑注浆对围岩力学性能的改善作用,提出单线段隧道采用双层小导管或管棚对掌子面进行超前支护,锚杆打设深度不小于6.0 m,注浆范围不小于2.5 m;双线段隧道采取双层纵向连接筋搭接钢拱架、增设4根锁脚锚管、加设临时水平横撑或三角横撑等措施进行支护,锚杆打设深度不小于8 m,注浆范围不小于4 m。采用综合措施后,隧道4个测试断面最大水平收敛和最大拱顶沉降的平均值均减小53%以上。

Based on the field test of tunnel surrounding rock deformation,the characteristics of large deformation and the range of surrounding rock broken zone of Shannenshan Tunnel on the China-Laos Railway were analyzed.The results show that the large deformation tunnel mainly converges horizontally,and there are arch bending,shotcrete spalling,tunnel face collapse and other deformation and damage phenomena.The deformation is mainly located at the vault and arch waist.The broken zones of surrounding rock of single-track and double-track tunnel are 6.0~6.5 m and 8.0~9.0 m respectively,which are more than 58%of the tunnel design span.According to the test and analysis results,starting from the active control of tunnel deformation,considering the improvement of the mechanical properties of surrounding rock by grouting,it is proposed that the single-track tunnel adopts double-layer small conduits or pipe sheds for advanced support of the tunnel face,the anchor bolt driving depth is not less than 6.0 m,and the grouting range is not less than 2.5 m.The double-track tunnel shall be supported by overlapping the steel arch with double longitudinal connecting bars,adding 4 anchor pipes for locking feet,and adding temporary horizontal or triangular cross braces.The depth of anchor bolts shall not be less than 8 m,and the grouting range shall not be less than 4 m.After adopting comprehensive measures,the average values of maximum horizontal convergence and maximum vault settlement of the four test sections of the tunnel are reduced by more than 53%.