不同应力路径下绢云母片岩粗粒料声发射特征

粗粒料在变形和颗粒破碎过程中伴随着明显的声发射(AE),通过监测粗粒料在外力作用下的声发射信号特征可用来研究其力学机制。为探讨不同应力路径下绢云母片岩粗粒料声发射规律,采用改装设计的大型三轴试验机,对绢云母片岩粗粒料分别开展了常规三轴固结排水、等p(体应力)和等q(偏应力)应力路径试验,同时监测其声发射信号。研究表明,对于粗粒料的声发射必须考虑颗粒间的滑动摩擦、翻滚摩擦、颗粒破碎这3种细观机制。不同围压、不同应力水平对颗粒间的滑移、翻滚以及颗粒破碎活动影响较大,因此,在不同阶段,摩擦型AE与破碎型AE所占比例各不相同。在等p路径下,当累计声发射信号出现拐点时,可判断其为应变软化点。等q试验产生的累计AE计数与累计AE能量计数要比等p试验的累计AE计数和累计AE能量计数少一个量级,说明等p试验状态下的声发射要比等q试验活跃。等p试验中,随着体应力逐渐增大,累计AE参量增长率逐渐增大,而等q试验中,随着偏应力逐渐增大,累计AE参量增长率逐渐降低。

Acoustic emission characteristics of sericite schist coarse aggregates under different stress paths

Acoustic emission (AE) will evidently accompany in the process of deformation and grain crushing of the coarse aggregates. Monitoring the acoustic emission signal characteristics of the coarse aggregates under the action of external force can be used to study the crushing mechanism. This paper studies the acoustic emission characteristics of sericite schist coarse aggregates. It uses the coupled acoustic emission large-scale triaxial test apparatus to carry out the conventional consolidated drained triaxial tests, the constant volumetric stress p and the constant deviatoric stress q tests on sericite schist coarse aggregates. The acoustic emission signals are monitored. The test results show that the acoustic emission of coarse aggregates is mainly from the particle breakage, sliding friction and rolling friction. The activities of inter-particle sliding, rolling and particle breakage are severely affected by different confining pressures and different stress levels. So the proportions of frictional AE and fractured AE are different at different stress levels. Under the constant p stress path test, the inflection point of accumulative acoustic emission signals appears, which can judge the strain softening point. The acoustic emission during the constant q test is obviously lower than that during the constant p test. The growth rate of accumulative acoustic emission parameters is gradually increased with the volumetric stress increasing in the constant p test. However, the growth rate of accumulative AE parameters is gradually decreased with the deviatoric stress increasing in the constant q test. It can be deduced that the acoustic emission of coarse aggregates is greatly influenced by shear stress.