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为研究经过不同温度作用后大理岩的渐进破坏全过程,对25℃,200℃,400℃和600℃后的大理岩进行单轴压缩试验,并监测其全变形过程的声发射现象,对其声发射特性、破裂模式、启裂应力和损伤应力取值范围、损伤演化规律及应力–应变模型进行研究。研究表明,随着大理岩经历温度的升高,岩石峰值强度逐渐降低,峰值应变增大,岩样延性增强;高温后大理岩的声发射特性与常温有明显区别,热损伤导致岩样加载初期声发射信号比较活跃,而进入弹性阶段后,声发射活动性不如常温下剧烈;用声发射法求出归一化启裂应力和归一化损伤应力的范围分别为0.33~0.46和0.71~0.82,随着温度升高,二者有增大的趋势;600℃以内,岩样破坏模式由单一劈裂破坏向多劈裂面破坏转变,最后变为单剪破坏,试验表明声发射定位与岩样宏观破裂规律对应较好。同时,建立基于累计振铃计数的损伤变量,25℃下岩样损伤演化过程分为4个阶段,高温后岩样初始损伤变大,损伤变量随应变演化变得缓慢。根据裂纹轴向应变规律和声发射参数推导大理岩变形全过程应力–应变本构模型,模型计算结果与试验曲线吻合较好,且温度越高,模型适用性越好。
In order to study the whole process of progressive destruction of marble after different temperatures, uniaxial compression tests were conducted on marble at 25 ℃, 200 ℃, 400 ℃ and 600 ℃, and the acoustic emission phenomenon of the marble during its deformation was monitored. Acoustic emission characteristics, fracture modes, cracking stress and damage stress range, damage evolution law and stress-strain model. The results show that with the increase of the temperature of marble, the rock peak strength gradually decreases and the peak strain increases, and the ductility of rock samples increases. The acoustic emission characteristics of marble at high temperature are obviously different from those at room temperature. Acoustic emission signal is relatively active, but after entering the elastic phase, the activity of acoustic emission is not as vigorous as that at normal temperature. The ranges of normalized cracking stress and normalized damage stress obtained by acoustic emission method are 0.33-0.46 and 0.71-0.82 , Both of them have an increasing trend with the increase of temperature. Within 600 ℃, the failure mode of rock samples changes from single cleavage to multi-cleavage failure and eventually becomes single shear failure. The experiment shows that the acoustic emission location and rock The macro-like rupture law is better. At the same time, a damage variable based on cumulative ring counting was established. The damage evolution of rock specimen at 25 ℃ was divided into four stages. The initial damage of rock specimen after high temperature became larger and the damage variable became slower with the strain evolution. The stress-strain constitutive model of the entire marble deformation process is deduced according to the axial strain and acoustic emission parameters of the crack. The calculated results are in good agreement with the experimental curves. The higher the temperature, the better the applicability of the model.