循环冻融条件下安山岩和花岗岩的物理力学特性试验研究

Acoustic Experimental Study of Two Types of Rock from the Tibetan Plateau under the Condition of Freeze-Thaw Cycles

结合青藏铁路块石护坡路基处于青藏高原特殊的气候条件,对用于青藏铁路护坡的两种主要岩石(花岗岩和安山岩)进行循环冻融试验.结果表明:两种岩石在经历了数次冻融循环后都出现了微细裂纹;声波监测表明,超声波速同冻融循环周期呈指数下降关系,显示了冻融循环对岩石风化的影响以及循环后岩石物理力学参数变化的趋势.结果说明,花岗岩的冻融后质量变化率远远低于安山岩,而孔隙率较大的安山岩破坏现象较花岗岩严重.随着冻融过程的深入,岩石的超声波纵横波速比同比在不同区域内下降,同时岩石的冻融过程中可能会出现负的泊松比.

Under the condition of freeze-thaw cycles,two types of rock（granite and andesite）,which were used as slope protection of 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.The observation results show that the damage of andesite was more serious than that of the granite.Using acoustic instrument,ultrasonic velocity was tested.The changing trends of the velocity with cycle number of freeze-thaw were analyzed,and the freeze-thaw cycle damaging the physical and mechanical properties of rocks can be seen.According to the changing trends of the ultrasonic velocity with the cycle number of freeze-thaw,a few mechanical parameters of the rocks,such as dynamic elastic modulus,Poisson ratio,and dynamic bulk modulus,were analyzed.It is found that they all have declining trend as the cycle number of freeze-thaw increases,and in particular,when the cycle number reaches a certain extent,the Poisson ratio of part rocks begins to become negative.