单轴压缩下加载速率对石膏波速变化影响的试验研究

Experimental Study on Impact of Loading Rate's on Wave Velocity Change of Gypsum Material under Uniaxial Compression

为研究单轴压缩下加载速率对石膏波速变化的影响,在4种不同加载速率下对石膏试样进行了单轴压缩试验,测试了加载过程中试样横向的纵波波速随应力的变化关系。结果表明,随着加载速率的增大,试样弹性模量和单轴抗压强度增大,峰值波速增大明显,与加载速率呈二次方关系;随加载速率增大,试样微裂纹更发育,材料更破碎,试样破坏类型向锥形破坏演变,使破坏点的波速明显随加载速率增大而减小;应力—波速曲线的斜率在峰值前随加载速率增大而减小,在峰值后则呈相反规律;随加载速率增加,在应力—波速曲线破坏点前,存在波速缓慢减小的过渡段与应力—应变曲线上由线弹性区向塑性区的转变段（损伤阈值出现段）相对应,其应力值占单轴抗压强度的60%~70%。

For studying the impact of uniaxial compression loading rate on the gypsum wave velocity change, uniaxial compression tests on gypsum sample under four different loading rates has been implemented to test the relationship be- tween longitudinal wave velocity changes and stress in the loading process. The experimental results show that the sample elastic modulus and uniaxial compressive strength increases with increasing loading rate, the peak wave velocity increases significantly, the relationship between the loading rate and the peak wave velocity is quadratic curve; sample presents con- ical destruction, microcrack is more development, and the material is more broken; the peak wave velocity increases sig- nificantly, and the stress corresponding to the peak point value increases, but the wave velocity of the destruction point decreases with loading rate increase; the slope of the stress-velocity curve before the peak decreases with the loading rate, inversely the law after the peak point; with the increase of the loading rate, there is an apparent wave speed＇s decreases slowly transition section in stress-wave velocity curve before the failure point, corresponding to the transition section from linear elastic to the plastic zone in stress-strain curve, it is the damage threshold segment; the stress value accounted for about 60% to 70% of the uniaxial compressive strength.