高温后砂岩静、动态力学特性研究与比较

 通过在SHT4206电液伺服万能试验机和分离式霍普金森压杆(SHPB)试验系统上对高温作用后砂岩分别进行静、动载荷加载试验，系统地分析比较了热作用后砂岩在静、动载荷加载下的破坏模式、峰值强度和峰值应变的差异，并从微观角度探讨温度对岩石力学性质的影响。研究结果表明：(1) 高温后砂岩的动态力学特性与静态力学特性相比变化显著，随着温度的升高，静载荷时岩石破坏模式表现为劈裂破坏并伴随着脆性断裂，而动载荷作用时岩石破坏模式表现拉伸破坏；(2) 静、动载荷作用下的峰值强度随着温度的升高而明显降低，且基本呈线性关系，静载荷作用下，平均峰值强度从126.37 MPa降到64.76 MPa，降低幅度为48.8%，动载荷作用时，平均峰值强度从176.3 MPa降到83.1 MPa，降低幅度达到了52.9%；(3) 静、动载荷作用下的峰值应变都随温度的升高而增大。温度引起的热应力和微结构的变化导致砂岩力学性质发生改变，以及不同加载方式引起试样内部孔隙扩展和微裂纹的生成方式不同，导致其抵抗外力变形的能力存在差异。

STUDY AND COMPARISON OF MECHANICAL PROPERTIES OF SANDSTONE UNDER STATIC AND DYNAMIC LOADINGS AFTER HIGH TEMPERATURE

Experiments are carried out to study sandstone mechanical properties after high temperature under static and dynamic loadings by the SHT4206 electro-hydraulic servo-controlled testing machine and split Hopkinson pressure bar(SHPB) equipment,respectively.The differences of rock failure mode,peak strength and peak strain after high temperature under static and dynamic loadings are analyzed and compared systematically.The effects of temperature on rock mechanical properties are investigated from microcosmic angle.The results show that:(1) The dynamic and static mechanical properties of rock are different evidently.With the increase of temperature,the failure mode of rock exhibits splitting failure with brittle fracture under static loadings while the rock failure mode is tensile fracture under dynamic loading.(2) The peak strength decreases evidently with the increase of temperature in a nearly linear way under static and dynamic loadings.The average peak strength decreases from 126.37 to 64.76 MPa in an extent of 48.8% under static loading,as well as from 176.3 to 83.1 MPa in an extent of 52.9% under dynamic loading.(3) The peak strain increases with the increase of temperature under static and dynamic loadings.Thermal stress and variation of microstructure induce different mechanical properties of sandstone due to the effect of temperature.The different modes of internal crack propagation and formation of microcracks appear due to different loading methods,which results in the difference in resistance of deformation.