高温后砂岩动态压缩条件下力学特性研究

Mechanical properties of sandstones after high temperature under dynamic loading

利用分离式霍普金逊压杆装置(SHPB)进行单轴动态压缩实验,研究砂岩经历25℃～800℃高温作用冷却后,密度、纵波波速、峰值强度随温度的变化规律;同时从破坏模式、块度分布以及高速摄影特性角度分析了高温后砂岩的动态破碎特性。研究结果表明:随着温度的升高,试样的密度、纵波波速、峰值强度均逐渐减小,200℃后纵波波速降低的幅度增大,400℃～600℃之间峰值强度降低幅度较小,800℃后峰值强度急剧下降;历高温后砂岩的动态破碎特点主要为拉伸破坏,且随着温度的升高,破碎程度越大,岩块分布趋细粒化。通过高速摄影仪拍摄图象,直观地再现了岩石动态破坏过程,发现纵向裂纹沿加载方向随机分布在岩样四周,且初始载荷时岩石破碎形态不具代表性而是随着应力波多次反射才形成最终的破坏形态。

The mechanical properties of sandstone specimens such as density,longitudinal wave velocity,peak dynamic strength are studied under dynamic compression loading after being heated at different temperatures（25℃～800℃）.Dynamic fragmentation characteristics of sandstone specimens are analyzed from different aspects of failure mode,fragment distribution and high-speed photography.The testing device of SHPB is adopted to conduct the dynamic experiments of rock specimens experiencing high temperatures.Though the experimental results are discrete,the general law is obvious.The results show that,with the increasing temperature,the specimen density,the longitudinal wave velocity and the peak strength all gradually decrease,and the decreased magnitude of the longitudinal wave velocity increases when the temperature is over 200℃.And the temperature changes from 400℃ to 600℃,the peak strength of rock has less decreased magnitude,and decreases sharply when the temperature is over 800℃.The dynamic failure characteristics of sandstone are mainly tensile failure after high temperature,with the increasing temperature,when rock fragmentation degrees increase,rock blocks become smaller.Through high-speed photography,dynamic failure process of rock is expressed.It is obtained that radial cracks are distributed around the specimens along the loading direction,the failure mode of rock is not representative at the initial loading,but the final failure mode of rock is obtained through the stress wave multiple reflection.