单轴压缩与劈裂破坏过程中充填体声发射特性研究
发布时间：2019-03-22 09:44
【摘要】：为了研究充填体损伤破坏时的声发射特性,本文对配合比为1:4和1:8的水泥分级尾砂胶结充填体分别进行了单轴压缩与劈裂破坏的声发射试验,分析了充填体试样的变形破坏模式,并得到了充填体试样在破坏过程中的声发射参数的特征规律,在此基础上,通过对声发射参数的b值和关联分形维数值的计算分析,得到了充填体试样在不同应力作用下裂纹萌生与扩展的损伤演化行为,并提出了充填体失稳破坏的预测依据;进一步利用RFPA2D数值模拟软件模拟再现了充填体试样在单轴压缩与劈裂拉伸条件下的破坏过程,从微观角度阐述了充填体试样由裂纹的萌生到失稳破坏的整个过程;最后利用声发射能率参数定义了充填体的损伤变量,建立了充填体损伤与声发射参数的关系,主要研究结论如下:(1)充填体的破坏过程主要分为孔隙压紧密实阶段、线弹性阶段、塑性屈服阶段和失稳破坏阶段,但劈裂破坏的充填体塑性屈服阶段极短,通常表现为脆性劈裂破坏。(2)配合比为1:4的单轴压缩充填体主要呈现“双曲线”形和“八”字形或倒“八”字形的剪切破坏,而配合比为1:8的充填体主要呈现一条或若干条劈裂带破坏,局部产生剪切破坏,而劈裂拉伸充填体主要沿着轴心贯穿整个试件“对称式”劈裂破坏。(3)单轴压缩与劈裂破坏的充填体在加载初期声发射信号极少,到应力峰值点或临近峰值点出现极大的声发射信号,但劈裂破坏的充填体试样在应力峰值点约45%时开始产生极大量的声发射信号,随后出现一段较为“平缓波动”的声发射信号高峰期。(4)单轴压缩与劈裂破坏的充填体试样在临近破坏时声发射b值和分形维数曲线都会呈现下降趋势,但劈裂破坏的充填体试样在应力峰值的45%~65%阶段时,声发射分形维数呈现一个明显的“下降—上升”的波动“拐点”,随后声发射分形维数的上下波动频率明显加快,意味着试件即将破坏。(5)结合充填体试样声发射b值和分形维数都同时下降且上、下振荡频率明显加快的变化特征规律,可作为充填体失稳破裂的前兆。(6)RFPA2D数值模拟再现了充填体试样由裂纹的萌生到失稳破坏的整个演化过程,单轴压缩与劈裂破坏的充填体首先是在靠近试件中心附近位置萌生损伤破坏的微单元,发展到零散分布众多破坏的微单元体,继而衍生发展成无序扩展的裂纹,随后转变成有序延伸的裂纹,最后抗压试件形成一条或若干条主斜裂纹而导致破坏,而劈裂试样最终在圆盘加载轴线的中心处形成一条由中部沿至两端的宏观裂隙带而导致破坏,与室内试验结果相比,具有很好的一致性。(7)通过声发射能率定义充填体试样在单轴压缩与劈裂拉伸破坏时的损伤变量,得到了应力-应变-损伤曲线,分析了不同应变阶段的损伤并建立了损伤模型方程。
[Abstract]:In order to study the acoustic emission (AE) characteristics of the filling body during damage and failure, the uniaxial compression and splitting tests of the cement graded tailings cementation filling with the mixture ratio of 1:4 and 1:8 were carried out in this paper. The mode of deformation and failure of the filling sample is analyzed, and the characteristic rule of acoustic emission parameters in the process of failure is obtained. On this basis, the b value of acoustic emission parameter and the correlation fractal dimension value are calculated and analyzed by means of the calculation and analysis of the b value and the correlation fractal dimension value of the acoustic emission parameter. The damage evolution behavior of crack initiation and propagation under different stresses is obtained, and the basis for predicting the instability and failure of the filling body is put forward. Furthermore, the failure process of the filling specimen under uniaxial compression and splitting tension is simulated by using RFPA2D numerical simulation software, and the whole process from crack initiation to instability is expounded from the microcosmic point of view. Finally, the damage variables of the filling body are defined by using the acoustic emission rate parameters, and the relationship between the damage of the filling body and the acoustic emission parameters is established. The main conclusions are as follows: (1) the failure process of the filling body is mainly divided into the stage of pore compaction, and the relationship between the damage of the filling body and the acoustic emission parameters is established. Linear elastic stage, plastic yield stage and unstable failure stage, but the plastic yield stage of fractured filling body is very short. It usually shows brittle splitting failure. (2) the uniaxial compression filling body with a mix ratio of 1:4 mainly shows shear failure of "hyperbolic" shape and "eight" shape or inverted "eight" shape. On the other hand, the filling body with the mix ratio of 1:8 mainly shows one or more splitting zones, and the local shear failure occurs. However, the splitting tensile filling body mainly runs through the whole specimen "symmetrical" splitting failure along the axial center. (3) the acoustic emission signals of the filling body under uniaxial compression and splitting failure are very few at the initial loading stage. A very large acoustic emission signal appears at or near the peak point of stress, but a large number of AE signals begin to be generated at the peak stress point of about 45% for the fractured filled sample. (4) the b value and fractal dimension curve of the filling sample with uniaxial compression and split failure will show a decreasing trend when the failure is approaching the failure, and then there is a peak period of the acoustic emission signal with a relatively "gentle fluctuation". However, in the 45%-65% stage of the peak stress, the acoustic emission fractal dimension presents an obvious "drop-rise" fluctuation "inflection point", and then the fluctuation frequency of the acoustic emission fractal dimension increases obviously. It means that the specimen is about to be destroyed. (5) the change characteristics of acoustic emission b value and fractal dimension both decrease at the same time and up, and the lower oscillation frequency is obviously speeded up. (6) the RFPA2D numerical simulation reproduces the whole evolution process from crack initiation to instability failure of the filling body specimen, which can be used as a precursor to the unstable failure of the filling body. The filling body of uniaxial compression and splitting failure is firstly a micro-unit that initiates damage near the center of the specimen, and develops to a micro-unit with a large number of damage scattered and scattered, and then develops into an unordered propagation crack. It is then transformed into an orderly extension of the crack, and the final compressive specimen forms one or more main oblique cracks resulting in failure. The splitting specimen finally formed a macro-crack zone from the middle to the two ends at the center of the disk loading axis, which resulted in the failure. Compared with the experimental results in the laboratory, There is good consistency. (7) the stress-strain-damage curve is obtained by defining the damage variables of the filled specimen under uniaxial compression and splitting tensile failure by the acoustic emission energy rate. The damage at different strain stages is analyzed and the damage model equation is established.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD853.34
[Abstract]:In order to study the acoustic emission (AE) characteristics of the filling body during damage and failure, the uniaxial compression and splitting tests of the cement graded tailings cementation filling with the mixture ratio of 1:4 and 1:8 were carried out in this paper. The mode of deformation and failure of the filling sample is analyzed, and the characteristic rule of acoustic emission parameters in the process of failure is obtained. On this basis, the b value of acoustic emission parameter and the correlation fractal dimension value are calculated and analyzed by means of the calculation and analysis of the b value and the correlation fractal dimension value of the acoustic emission parameter. The damage evolution behavior of crack initiation and propagation under different stresses is obtained, and the basis for predicting the instability and failure of the filling body is put forward. Furthermore, the failure process of the filling specimen under uniaxial compression and splitting tension is simulated by using RFPA2D numerical simulation software, and the whole process from crack initiation to instability is expounded from the microcosmic point of view. Finally, the damage variables of the filling body are defined by using the acoustic emission rate parameters, and the relationship between the damage of the filling body and the acoustic emission parameters is established. The main conclusions are as follows: (1) the failure process of the filling body is mainly divided into the stage of pore compaction, and the relationship between the damage of the filling body and the acoustic emission parameters is established. Linear elastic stage, plastic yield stage and unstable failure stage, but the plastic yield stage of fractured filling body is very short. It usually shows brittle splitting failure. (2) the uniaxial compression filling body with a mix ratio of 1:4 mainly shows shear failure of "hyperbolic" shape and "eight" shape or inverted "eight" shape. On the other hand, the filling body with the mix ratio of 1:8 mainly shows one or more splitting zones, and the local shear failure occurs. However, the splitting tensile filling body mainly runs through the whole specimen "symmetrical" splitting failure along the axial center. (3) the acoustic emission signals of the filling body under uniaxial compression and splitting failure are very few at the initial loading stage. A very large acoustic emission signal appears at or near the peak point of stress, but a large number of AE signals begin to be generated at the peak stress point of about 45% for the fractured filled sample. (4) the b value and fractal dimension curve of the filling sample with uniaxial compression and split failure will show a decreasing trend when the failure is approaching the failure, and then there is a peak period of the acoustic emission signal with a relatively "gentle fluctuation". However, in the 45%-65% stage of the peak stress, the acoustic emission fractal dimension presents an obvious "drop-rise" fluctuation "inflection point", and then the fluctuation frequency of the acoustic emission fractal dimension increases obviously. It means that the specimen is about to be destroyed. (5) the change characteristics of acoustic emission b value and fractal dimension both decrease at the same time and up, and the lower oscillation frequency is obviously speeded up. (6) the RFPA2D numerical simulation reproduces the whole evolution process from crack initiation to instability failure of the filling body specimen, which can be used as a precursor to the unstable failure of the filling body. The filling body of uniaxial compression and splitting failure is firstly a micro-unit that initiates damage near the center of the specimen, and develops to a micro-unit with a large number of damage scattered and scattered, and then develops into an unordered propagation crack. It is then transformed into an orderly extension of the crack, and the final compressive specimen forms one or more main oblique cracks resulting in failure. The splitting specimen finally formed a macro-crack zone from the middle to the two ends at the center of the disk loading axis, which resulted in the failure. Compared with the experimental results in the laboratory, There is good consistency. (7) the stress-strain-damage curve is obtained by defining the damage variables of the filled specimen under uniaxial compression and splitting tensile failure by the acoustic emission energy rate. The damage at different strain stages is analyzed and the damage model equation is established.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD853.34
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