Study on the effect of dynamic disturbance on creep behavior of frozen fractured red sandstone

The freezing method is an effective water shut-off method for shaft construction in water-rich Cretaceous strata in Northwest China. Blasting is an efficient excavation method for vertical shafts crossing the frozen stratum. The frozen rock wall is usually composed of ice and fractured rock mass and is influenced by both the in situ stress and blasting disturbance. To study the creep behavior of fractured rock masses under subzero temperatures and dynamic disturbances, a series of conventional triaxial creep and creep-disturbance tests were carried out. The results show that the flaw dip angle and dynamic disturbance had a significant influence on the creep failure characteristics of the specimens. The creep rate and failure strain of the accelerated creep stage of the specimens under dynamic disturbance were significantly greater than those of the specimens that did not undergo dynamic disturbance. Dynamic disturbance closed and recombined the microcracks, improved the short-term bearing capacity, increased the total creep time, and reduced the creep rate of the specimens. When the load or disturbance intensity reached a certain value, the crack propagation rate and creep rate of a specimen increased, the disturbance energy stored in the rock mass was released, and the specimen suddenly failed. Therefore, this disturbance creep phenomenon must be considered when constructing freezing vertical shafts in Northwest China. Moreover, timely support should be provided for exposed ice-filled fractured rock masses to guarantee construction safety and rock mass stability.