花岗岩在不同温度劈裂载荷下的损伤演化与失稳前兆

Damage evolution and destabilization precursors in granite under splitting load at different temperatures

为了阐明深地钻探中花岗岩在劈裂载荷与高温作用下的复杂机械和损伤特性,对经50~600℃处理的花岗岩试样进行巴西劈裂声发射(AE)试验。结果表明,温度变化会使花岗岩的机械与声发射特性发生改变,从而改变其破裂演化过程。当温度超过500℃时,花岗岩的抗拉强度大幅降低,剪切损伤模式占比增加。此外,破裂速率亦呈现明显增长趋势。在基于撞击数和能量计数的损伤参数演化曲线的基础上,定义“损伤参数突变点”来判断作为岩石破坏的前兆信息。基于撞击数的“突变点”比岩石失稳的信号提前到达,且岩石损伤越大,提前的时间越久。通过这个时间差,可以达到预警岩石失稳的效果。

Brazilian splitting acoustic emission(AE)tests were conducted on the granite specimens that were heated at the temperatures from 50 to 600℃ to investigate the mechanical and damage characteristics of granite under high temperatures and splitting load in deep drilling.The results indicate that temperature variations significantly alter the mechanical characteristics and AE properties of granite,thereby influencing the evolution of fractures.At the temperature above 500℃,the tensile strength of granite decreases significantly and the proportion of shear-induced damage modes increases.Furthermore,the rate of fracturing also exhibits a noticeable increase.Damage parameter mutation points on the damage parameter evolution curves of hit counts and energy counts were defined to determine the rock damage precursor.Mutation points based on hit counts arrive earlier than rock instability signals.The greater the damage is,the earlier the mutation points arrive.This time difference can be used to identify rock destabilization signals.