Jordan Journal of Civil Engineering

Characteristics of pre-peak mechanical damage and energy evolution of typical hard-rock in diversion tunnel under cyclic loading-unloading


Rongzhou Yang; Yonghui Lai; Ying Xu; Suqian Ni;


An in-depth understanding of the pre-peak mechanical damage and energy evolution characteristics of typical hard-rock in a diversion tunnel under cyclic load is of great significance to promote the safe and efficient construction of the diversion tunnel and the stability of surrounding rock. To study the pre-peak mechanical characteristics and the competition mechanism between energy storage and energy dissipation of typical hard-rock in a diversion tunnel under cyclic loading-unloading, the cyclic loading-unloading tests were carried out on typical granite and tuff in the diversion tunnel. The results show that the pre-peak stress-strain curves of granite and tuff showed the evolution characteristics from "sparse" to "dense" and then to "sparse", reflecting the initial plastic compaction effect and the late cumulative damage effect. The obvious elastic deformation of rock samples occurred in the whole process of cyclic loading-unloading deformation, which highlighted the elastic-brittleness of rock samples, and the plastic deformation of rock samples gradually transformed to elastic deformation with the increase of the number of cycles. The main reason that the unloading deformation modulus was slightly less than the loading deformation modulus was the existence of plastic deformation during each cycle, which led to the generation of unclosure degree. The elastic energy ratio of rock samples after the initial compaction stage was significantly greater than the dissipated energy ratio, which promoted the transformation of input energy to elastic energy. However, due to the continuous existence of the cumulative effect of plastic dissipative energy, the cumulative dissipative energy of rock samples increases continuously, which will promote the development of damage of rock samples.


Diversion tunnel, Cyclic loading-unloading, Granite/Tuff, Mechanical properties, Energy evolution