高温后花岗岩断裂特性的加载速率效应研究

Loading rate effect on fracture properties of granite after high temperature

为考察温度和加载速率对花岗岩断裂特性的影响规律,对25～800℃之间5种温度水平高温后的中心直裂纹花岗岩巴西圆盘试样分别进行了5种加载速率下的室内劈裂试验.结果表明：圆盘的荷载-位移曲线呈现典型的脆性特征,但随温度的升高,脆性特征逐渐弱化,与加载速率相比,温度对曲线的发展趋势影响较大;随温度的升高,花岗岩断裂韧度逐渐减小且在400℃时发生突变;不同温度条件下断裂韧度随加载速率的增大逐渐增加,但增加幅度逐渐减小最终趋于平缓,具有明显的加载速率效应,提出了相应的经验公式KIC=A＋B/（v＋C）,其中随温度的升高,参数A逐渐降低,参数B波动较小,而参数C逐渐增大,同时获得了花岗岩材料断裂韧度的下限值KIC0。

Indoor splitting test of cracked straight-through Brazilian disc samples of granite after five temperature levels between 25 and 800 ℃ was conducted with five different kinds of loading rate.The influence of temperature and loading rate on the fracture properties of granite was studied.The results show that loading-displacement curves of the disc samples present typical brittle characteristics,while the brittle characteristics weaken gradually with the increase of temperature.Compared with the loading rate,the influence of temperature on the development trend of loading-displacement curves is greater.The fracture toughness of granite decreases gradually with the increasing temperature and a mutation occurs when the temperature is 400℃.The fracture toughness of granite increases gradually with the growth of loading rate under different temperature conditions,while the increasing amplitude weakens gradually and flattens out,presenting obvious loading rate effect.Corresponding theoretical model KIC=A＋B/（v＋C）was put forward,and with the increasing temperature,parameter Adecreases while parameter Cincreases gradually,with parameter Bkeeping stable relatively.Lower limit KIC0 of the fracture toughness of granite was also obtained.