Acoustic experimental study of two types of rock from the Tibetan Plateau under the condition of freeze-thaw cycles

摘要

Under the condition of freeze-thaw cycles,two types of rocks(granite and andesite),used as slope protection for the Qinghai-Tibet Railway,were tested according to the special climatic conditions in the Tibetan Plateau,and their various damage processes in appearance were carefully observed.Observation results show that damage of andesite was more serious than that of granite.Using an acoustic instrument,ultrasonic velocity was tested.The changing trends of velocity with the number of freeze-thaw cycles were analyzed,and the freeze-thaw cycle damaging the physical and mechanical properties of rocks can be seen.According to the changing trends of ultrasonic velocity with the number of freeze-thaw cycles,mechanical parameters of rocks,such as dynamic elasticity modulus,Poisson's ratio,and dynamic bulk modulus were analyzed.It is found that they all have declining trends as the number of freeze-thaw cycles increases,and in particular,when the cycle number reaches a certain extent,the Poisson's ratio of rocks begins to become negative.