北山花岗岩张拉力学性质及声发射特征研究

Study on Tensile and Acoustic Emission Characteristics of Beishan Granite

以我国高放射性废物处置库甘肃北山预选区为工程背景,通过巴西劈裂试验、直接拉伸试验以及三轴压缩试验研究北山花岗岩的基本力学性质,试验过程中监测声发射数据,基于声发射特征开展了巴西劈裂试件内部的破裂形式及其演化过程研究。研究表明:①直接拉伸试件的强度约为巴西劈裂试件强度的1.23倍,巴西劈裂试件呈现明显的脆性破坏,而直接拉伸试件呈现一定的塑性破坏特征;②巴西劈裂试件的声发射事件数在应力达到峰值应力的70%之前增加比较剧烈,直接拉伸试件的声发射事件数在峰值附近增加比较剧烈;③三轴压缩试验声发射事件的频率主要分布在0~80 kHz范围内,直接拉伸试验和巴西劈裂试验的声发射事件频率主要集中在0~160 kHz;④巴西劈裂试件张拉裂纹的数量约为剪切裂纹数量的20.6倍,且张拉裂纹由试件中心向端部扩展,并最终形成贯通的破裂面。

Taking Beishan pre-selected area of China′s high-level radioactive waste disposal repository in Gansu Province as the engineering background,basic mechanical properties of Beishan granite are studied by Brazilian splitting test,direct tensile test and triaxial compression test.The acoustic emission data were monitored during the test,cracks form and failure process of Brazilian splitting test specimen were studied during the characteristics of acoustic emission.The results show that:①The strength of direct tensile specimens is about 1.23 times that of Brazilian splitting specimens,specimens of Brazilian splitting test show obvious brittle failure,while specimens of direct tensile test shows plastic failure;②The acoustic emission events in Brazilian splitting test increase sharply before the stress reaches 70%of the peak stress,while the number of acoustic emission events in direct tensile test increases sharply around the peak stress;③The frequency of AE events in triaxial compression test is mainly distributed at 0~80 kHz,while the frequency of AE events in direct tensile test and Brazilian splitting test is mainly concentrated at 0~160 kHz;④The number of tensile cracks in Brazilian split test specimens is about 20.6 times of the number of shear cracks,the tensile cracks extend from the center of the specimen to the end,and finally form the through fracture surface.