基于声发射参量表征块石胶结充填体损伤破坏机理研究

发布时间：2018-02-05 01:58

本文关键词： 块石胶结充填体损伤破坏模式声发射概率密度函数声发射速率过程理论　出处：《江西理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：声发射、应力、应变参量三者均属材料本构参量,对块石胶结充填体进行稳定性评价时,其受力历史是未知的,很难根据应力应变参量的本构关系来评价,而材料声发射由于具有不可逆性,正好弥补了这一不足。因为加载过程中的微裂纹扩展速率可以利用声发射事件的概率密度表征,本文拟应用学者Dai和学者Labuz研究脆性材料(混凝土、岩石等)声发射特性时提及的声发射事件累积数N与应力水平σ%间的声发射事件概率密度函数,通过不同骨料配比块石胶结充填体单轴加载声发射试验,获得承载过程不同时刻的声发射累积数,根据计算公式得出声发射事件概率密度,通过声发射事件概率密度与应力水平关系曲线分析,表征单轴载荷下块石胶结充填体不同强度等级(骨料配比不同)力学参数(相对应力水平)与声发射参数(声发射事件概率密度)的关系。综上所述,本文主要研究结论如下:(1)通过分析不同块石含量胶结充填体破坏过程全应力-应变曲线,根据曲线的变化特征可以将充填体试样变形过程划分为压密、弹性变形、屈服变形、破坏以及残余承载五阶段;块石含量的增加在一定程度上减少了垂直于压应力方向的原始微裂隙、孔隙数量,改善了块石胶结充填体初始内部结构。(2)随着块石含量增加,累计声发射事件数快速增长阶段(直线段)出现由压密段向塑性段过渡的明显趋势;由于累计声发射事件数与损伤存在关联,因此,在块石含量的影响下,整个承载过程胶结充填体损伤的主要阶段出现后移趋势;块石含量较低时,整个承载过程中损伤值及其变化规律比较接近纯尾砂胶结充填体,块石含量持续增加,达到45%左右时,中等应力水平以下(应力水平小于50%),损伤值变化不明显,且一直在较低水平波动,说明块石含量增加对尾砂胶结充填体承载前期的损伤具有较好的抑制作用。(3)通过分析大量声发射试验数据得到,块石胶结充填体的破裂模式主要可以分为劈裂破裂模式、条形破裂模式和爆裂破裂模式;这些破裂模式的形成均由块石含量的变化引起;将声发射参数和块石含量建立联系,拟合得出声发射速率参数a,根据其变化趋势可得到三种块石胶结充填体破坏判别模式,即持续减小趋势可判别该试件为劈裂破坏;随时间上下波动无明显上升或下降趋势可判别为条形破坏;小幅波动出现急速上涨可判别为爆裂破坏。
[Abstract]:Acoustic emission, stress and strain parameters all belong to the constitutive parameters of materials. When evaluating the stability of cemented filling body, the history of stress is unknown, so it is difficult to evaluate the constitutive relationship of stress and strain parameters. Due to the irreversibility of the material acoustic emission (AE) makes up for this deficiency because the microcrack propagation rate in the loading process can be characterized by the probability density of the AE event. This paper intends to apply Dai and Labuz to study brittle materials (concrete). The probability density function of AE event between the cumulative number of AE events N and stress level 蟽% mentioned in acoustic emission (AE) characteristics is tested by uniaxial loading of block cemented filling body with different aggregate ratio. The cumulative number of acoustic emission at different time in the loading process is obtained and the probability density of acoustic emission event is obtained according to the calculation formula. The relationship between the probability density of acoustic emission event and the stress level is analyzed by means of the curve of the probability density of acoustic emission event. The relationship between mechanical parameters (corresponding force level) and acoustic emission parameters (AE event probability density) under uniaxial loading is characterized. The main conclusions of this paper are as follows: (1) by analyzing the total stress-strain curves of cemented filling with different rock contents, the deformation process of filling samples can be divided into compaction according to the changing characteristics of the curves. Elastic deformation, yield deformation, failure and residual loading; The increase of rock mass content to some extent reduces the original micro-fractures perpendicular to the compressive stress direction, the number of pores, and improves the initial internal structure of the block cemented filling. 2) with the increase of rock mass content. The accumulative number of acoustic emission events in the rapid growth stage (straight line section) shows a clear trend from the compaction section to the plastic segment. Because of the correlation between the cumulative number of AE events and the damage, the main damage stage of cemented backfill appears backward trend under the influence of rock mass content. When the rock content is low, the damage value and its change law are close to the pure tailings cemented filling body during the whole loading process, and the rock mass content continues to increase, reaching about 45%. Below the medium stress level (the stress level is less than 50%), the damage value is not obvious, and has been fluctuating in the lower level. It shows that the increase of rock mass content has a better inhibition effect on the damage of tailings cemented filling in the early loading stage. (3) by analyzing a large number of acoustic emission test data. The fracture modes of the cemented filling body can be divided into split fracture mode, stripe fracture mode and burst fracture mode. The formation of these fracture modes is caused by the change of rock mass content. The acoustic emission parameters are related with the mass content, and the acoustic emission rate parameters a are fitted. According to the change trend, three kinds of failure discrimination models of cemented filling body can be obtained. That is to say, the continuous decreasing trend can distinguish the specimen as splitting failure; There is no obvious upward or downward trend with time fluctuation, which can be identified as strip failure. Small fluctuation appears rapid rise can be distinguished as burst damage.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD853.34

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