冲击载荷作用下高温砂岩动态力学性能试验研究

Experimental study on dynamic mechanical properties of high temperature sandstone under impact loads

为研究高温状态下岩石动态力学性能,利用变截面SHPB试验装置及配套高温环境箱,对常温(25℃),200℃,400℃,600℃,800℃和1 000℃共6种温度作用下砂岩试件,进行6种加载速率冲击压缩试验。结果表明:(1)动态峰值应力与加载速率呈二次多项式函数关系,正相关性显著。200℃～800℃温度具有强化作用,200℃时最明显;1 000℃温度具有软化作用。(2)动态峰值应变与加载速率近似为二次多项式函数关系,正相关性明显。200℃～600℃温度作用影响不明显;800℃温度作用明显,1 000℃时温度作用显著。(3)动态弹性模量受加载速率作用不明显,随温度升高整体呈下降趋势。200℃～600℃时幅值变化在一定范围;800℃和1 000℃时幅值相对较小。(4)试件破坏形态不同,随温度增加由脆性破坏向延脆性破坏转化。随加载速率增大,破裂面逐渐增多,破碎程度加剧,碎块尺寸减小。1000℃时,加载速率较小时破碎效果不明显,加载速率较大时破碎效果显著。

To investigate the dynamic properties of sandstone under high temperature,impact compression tests at 6 loading rates were carried out under different temperatures of 25℃,200℃,400℃,600℃,800℃and 1 000℃using variable cross-section split Hopkinson pressure bar test apparatus and high temperature equipment.Test results show that there shows a positive quadratic function relationship between the dynamic peak stress and the loading rate.Strengthen effect of the temperature on the dynamic peak stress appears in the range of 200℃to 800℃,which is most obvious at 200℃,while the dynamic peak stress is weaken at 1 000℃.There is also a positive quadratic function relationship between the dynamic peak strain and the loading rate.The effect of the temperature on the dynamic peak strain is inconspicuous from 200℃to 600℃,but is remarkable at 800℃,especially at 1 000℃.The dynamic elastic modulus decreases with rising the temperature but is almost independent of the loading rate.The dynamic elastic modulus varies in a certain range from 200℃to 600℃,while has a smaller change at 800℃and 1 000℃.With increasing temperature,the failure mode presents a transformation from brittle failure to ductile-brittle failure.The bigger the loading rate is,the more the fracture surfaces are,the worse the broken degree is,and the smaller the fracture fragments are.At 1 000℃,fracture effect is more remarkable in a larger loading rate.