围岩时变承载能力定量评估的LDP-GRC耦合新方法
A new approach of coupling between LDP and GRC for quantitative evaluation of time-dependent self-carrying capacity of surrounding rock

摘要 为定量判断二次支护时机，在围岩自承载系数基础上考虑岩石的流变力学性质，采用Boltzmann流变模型推导了围岩时变承载系数，研究了时间轴上围岩自承能力的变化过程和发挥程度.并以围岩时变承载系数为基础建立考虑时变效应的LDP和GRC曲线耦合新方法，定量得出二次支护时机及围岩时变承载系数间的相关关系.研究结果表明：1）不同隧洞断面处的围岩自承能力随时间变化趋势相似，都是开挖初期围岩自承能力迅速变弱，随后慢慢趋于稳定；经过相同的蠕变时间，距离开挖面越远，围岩自承能力越弱.2）同一隧洞断面处，时间越早围岩时变承载系数越大，围岩自承能力尚未充分发挥，不宜进行二次支护，即二次支护时机应该避开初期围岩自承能力变化剧烈时段.
Abstract：In order to assess the secondary support time quantitatively,the time-varying self-bearing coefficient of surrounding rock is proposed based upon the Boltzmann rheological model,which aims to investigate the time-dependent process in which the surrounding rock’s self-bearing capacity changes and develops.It takes into consideration the rheological mechanics characteristic of rock based on the self-bearing coefficient of surrounding rock. Then, a new coupling approach between LDP and GRC considering time-dependent effect is established based upon time-varying self-bearing coefficient of surrounding rock, and the secondary support time versus the time-varying self-bearing coefficient of surrounding rock is accurately evaluated.The results show that:1)The change of self-bearing capability of surrounding rock over time is similar at different cross sections of tunnel, namely, self-bearing capacity of surrounding rock drastically reduces in the early excavation stage and then tends to be steadied.And the farther away from the excavation surface,the weaker the self-bearing capacity of surrounding rock is;2)The coupling analysis reveals that the sooner the secondary support is set up,the greater time-varying self-bearing coefficient is.It is not reasonable to carry out the secondary supporting structure when the time-varying self-bearing coefficient drops dramatically over time, because the self-bearing capability of surrounding rock cannot perform well then.