湿陷性黄土隧道三台阶法施工时间应变规律

Rule of Time-dependent Stress of Tunnels in Wet Subsidence Loess Constructed by 3-bench Excavation Method

通过对湿陷性黄土围岩监测,揭示时间应变规律,结合此规律形成一套三台阶施工工法,并总结出使用此工法施工围岩的变形特性如下:上台阶开挖后稳定7 d左右,表现为沉降,在施工二台阶马口时,允许上台阶初期支护在可控范围内下沉,也是应力释放的过程;三台阶施工沉降变形规律与二台阶类似,在仰拱封闭后,围岩趋于稳定。

The rule of the time-dependent strains of the tunnels in wet subsidence loess ground is revealed by means of monitoring of the wet subsidence loess ground. A kind of 3-bench construction method is developed on basis of the rule of the time-dependent strains. The deformation behavior of the tunnels constructed by 3-bench excavation method is summarized as follows ： After top heading excavation, the tunnel stability can maintain 7 days before settlement occurs ; During the excavation of the second bench, the controlled settlement of the primary reinforcement structure of the top heading is allowed, which is a stress releasing process; The settlement deformation caused by the third bench excavation is similar to that caused by the second bench excavation; When the ring is closed after invert installation, the ground tends to be stable. 3-bench construction is executed under the guidance of the above deformation rule in the construction of Lanzhou-Chongqing railway and satisfactory effects have been achieved.