软岩硐室稳定性的复合结构柔性反底拱控制时效分析

Time effects of flexible inverted arch with composite structures to control stability of chamber adjoining with soft rock masses

地下工程的围岩为软岩或因赋存深度的增加而呈现软岩特征时,其稳定性控制问题趋于突出,而对软岩硐室底臌的有效控制是决定硐室整体稳定性、保障其服务年限的关键。设计应用于软岩硐室底臌控制的复合结构柔性反底拱,探讨其作用机理,其控制底臌的时间效应包括成拱初期的负底臌效应、吸收变形能为主要特征的柔性支护阶段和后期延长服务年限为目的的刚性支护阶段,其中柔性支护作用保证了相对较长而且稳定的软岩硐室服务年限。经实践证明,试验条件下的负底臌效应历时63 d,柔性结构控制底臌的作用时间为158 d,反底拱刚性结构对底臌的控制可以延长巷道的服务年限140 d,即巷道在1 a内无需底板修复。复合结构柔性反底拱的底臌控制效果明显,但是硐室整体稳定性并非单一依赖于对底臌的控制,支护体系在边界上存在相对薄弱的环节等因素,依然可转化为软岩硐室整体破坏的主要原因。

It is important to determine the stability of underground projects which are driven in soft rock masses or buried in deep site. Restraining the floor heave of the chamber adjoining with soft rock masses is an effective approach to control its stability and ensure its service period. The flexible inverted arch with composite structures is designed mainly to reduce the floor heave, and its operating mechanism is also studied. The time effects of the flexible inverted arch with composite structures to control the floor heave of the chamber adjoining soft rock masses will include the initial stage with negative floor heave, flexible support stage to absorb deformation energy, and rigid support stage to prolong its service period. The flexible support effect has steadily ensured a longer service period of the chamber. The practices indicate that the time effects of negative floor heave under test conditions last a period of 63 days, the controlling period of flexible structure to the floor heave may be up to 158 days, and the service period of 140 days of the testing roadway is prolonged by the rigid structure of inverted arch to restrain the floor heave. Therefore, the testing roadway may dispense with rebuilding work in one year, particularly in the floor heave. Although the flexible inverted arch with composite structures has distinct effects to control the floor heave, the overall stability of the chamber can not simply depend on the only factor. The relatively weak boundary part of the supporting system will become the main cause of the destruction of the chamber adjoining soft rock masses.