不同高温处理后北山花岗岩物理力学性质

Physical and mechanical properties of Beishan granite after different high temperature treatments

在中国,北山花岗岩被选为高放废物处置库的潜在围岩。本研究对北山花岗岩试件分别进行了300,400和500℃的热处理,并对热处理后的试件进行了常规三轴压缩试验。结果表明:经过300、400和500℃热处理后,试样直径分别增加0.066%,0.143%和0.409%;并且试件直径的变化略大于试件轴向长度的变化。力学试验结果表明:随着温度的升高,峰值强度略有增加,剪胀阈值有所降低。峰值应变和剪胀阈值应变表现出很强的温度依赖性;温度越高,应变越大。温度的升高对阈值弹性模量Ec和切线弹性模量Et有负面影响;在300到500℃以内,泊松比随温度的升高而减小,但仍大于未经热处理试件的泊松比。此外,声发射监测显示,在加载初期有一平静阶段,说明微裂纹受到加热而闭合,有助于峰值强度的提高。

In China,Beishan granite is chosen as a potential host surrounding rock of a high-level radioactive waste(HLW)repository.For this research,Beishan granite specimens were heated up to 300℃,400℃ and 500℃,respectively.And conventional triaxial compression tests were conducted after cooling down the samples.The results show that after 300℃,400℃ and 500℃ heating treatment,the diameter of samples increases by 0.066%,0.143%and 0.409%,respectively,which is a little larger than the axial length changes.Mechanical tests show that peak strength increases slightly with increasing temperature.However,the dilatancy threshold is lower than that observed for samples which have not experienced heating treatment.Peak strain and dilatancy threshold strain show a strong temperature dependence.The higher the temperature,the greater the strain.Furthermore,increasing temperature has negative influence on threshold elastic modulus E_(c) and tangent elastic modulus E_(t).Poisson ratio decreases when temperature increases from 300℃ to 500℃,but it is still larger than that observed for samples which have not experienced heating treatment.In addition,AE monitoring shows a quiet period in the initial loading stage,which proves that the micro cracks are closed during heating and contribute to the increase of peak strength.