加载速率对实时高温花岗岩三轴力学特性影响的实验研究

Experimental Study on the Effect of Loading Rate on Triaxial Mechanical Properties of Real-time High Temperature Granite

以未风化花岗岩为实验对象,在高温高压三轴力学实验系统上开展三轴压缩实验,分析了三种加载速率下岩样温度、围压对峰值强度、弹性模量的影响,探讨了岩样热损伤演化规律的加载速率效应,建立了花岗岩冷损伤方程。结果显示:在100℃时,加载速率增大,低围压区岩石由延性转向脆性,渐进破坏向突发失稳转变;在500℃时,加载速率增大,低围压区弹性模量硬化明显,失稳模式为准突发失稳;随着加载速率的增大,在低温30~200℃时峰值强度的增加显著,在较高温度200~500℃时峰值强度的增加幅度降低,随着围压的升高,加载速率使峰值强度增强作用降低;各级岩石温度条件下,加载速率与弹性模量相关性不显著;低围压时弹性模量增幅较大,高围压时弹性模量增幅较小;随着加载速率的提高,弹性模量损伤与岩石温度的关系由线性转变为非线性的临界围压降低。

The unweathered granite was taken into research.The triaxial compression test was carried out on the high temperature and high pressure triaxial mechanical experiment system.The effects of rock sample temperature,confining pressure on peak strength and elastic modulus were analyzed at three different loading rates.The loading rate effect of the thermal damage evolution law was established,and the cold damage equation of granite was established.The results show that the loading rate increases,the rock in the low confining pressure zone changes from ductile to brittle,and the progressive failure changes to sudden instability at 100℃.At 500℃,the loading rate increases,and the elasticity of the low confining pressure zone is obvious,the instability mode is quasi-burst instability.With the increase of loading rate,the peak intensity increases significantly at low temperature between 30 to 200℃,and decreases at higher temperature of 200 to 500℃.As the confining pressure increases,the loading rate reduces the enhancement of peak strength.Under the rock temperature conditions,the correlation between loading rate and elastic modulus is not significant.The elasticity increases greatly at low confining pressure while increasing slightly at high confining pressure.As the loading rate increases,the relationship between elastic modulus damage and rock temperature decreases from linear to nonlinear critical confining pressure.