中心轴式预切槽机械在大断面黄土隧道中的应用试验

黄土是一种特殊的第四纪陆相松散堆积物,具有强度低、变形大、自稳能力差的特点,我国大断面黄土隧道的建设通常采用三台阶七步开挖法、CD法、CRD法、双侧壁导坑法等,存在施工工序多、施工进度慢、变形量难以控制、临时支护用量大、对各小断面支护结构的连接工艺要求高等问题,研究适合软弱围岩隧道机械化施工的工法非常必要。预切槽法由于具有控制地层变形能力强、施工速度快的特点,受到国内隧道界的再次关注。2013年,中铁重工集团研制成功了国内第一代中心轴式预切槽机械。为了掌握预切槽机械切灌过程性能及预衬砌的受力变形特性,进行预切槽机械在黄土隧道中的工业化试验。研究认为:(1)研制的中心轴式预切槽机械在黄土地层切割成槽能力良好,但在切灌一体化方面尚需要深入研究;(2)由于限制了地层的变形,预衬砌承受的地层压力较大。(3)预切槽法对切槽脚部地基的承载力要求较高,预衬砌脚部是拉应力集中区域,实际施工中要进行合理加固。

Application Test of Center Axis Pre-cut Machine in Large-section Loess Tunnel

Loess is a special kind of quaternary continental loose debris, characterized by low strength, large deformation and poor stability.Large section loess tunnel construction in China usually employs such methods as three-bench seven-step excavation method,CD,CRD and double side drift method,which may result in great many construction processes,low progress,difficulties in controlling deformation,excessive temporary support and complex connection of supporting structures in each individual small section. Therefore,it is necessary to study mechanized construction method for soft ground tunneling. The pre-cut method attracts again the attention of domestic tunnel constructors due to its advantages in controlling ground deformation and construction speed. In 2013,China Railway Construction Heavy Industry Co.,Ltd. successfully developed the first generation center axis pre-cut machine in China. To master the performances and characteristics of the machine with respect to the stress and deformation in pre-lining process,tests are conducted in largesection loess tunnel. The results show that( 1) the machine has good cutting capacity in loess strata,but further study is required on the integration of cutting and filling;( 2) due to limited deformation of strata,the pre-lining bears bigger ground pressure;( 3) the pre-cut method requires higher bearing capacity of the foot foundation and the foot of the pre-lining is a tensile-stress-concentrated area,which needs to be consolidated during construction.