Abstract
In order to reveal the mechanical properties and damage mechanism of coal with parallel multibedding under stress disturbance, the raw coal samples with parallel multibedding were selected. The uniaxial compression and acoustic emission damage measurement were carried out using the coal-rock mechanics damage coupling test system, revealing the bedding effect of coal deformation-damage failure differentiation under different loading methods; based on the test results, a coupling characterization model of mechanical damage of coal and rock with parallel multibedding is established. The results show that (a) the acoustic emission of raw coal samples under different loading modes has obvious differentiation characteristics of bedding effect. When the vertical bedding is loaded, the peak stress of raw coal samples is relatively high and the acoustic emission activity period is relatively long; when the parallel bedding is loaded, the active degree of acoustic emission is relatively strong, and there is an obvious mutation period after the acoustic emission enters the acute period. (b) Under different loading modes, the difference in the influence of bedding on the fracture evolution of raw coal specimens is mainly concentrated before the stress turning point. In stage I, the acoustic emission b value of raw coal specimens decreases first, then becomes stable under vertical bedding loading, and decreases under parallel bedding loading; in stages II and III, the acoustic emission b value of raw coal samples showed the same change trend under different loading modes. (c) Combined with the basic principle of continuous damage mechanics and based on the difference of bedding effect, the relationship between cumulative acoustic emission ringing count and stress and damage variable of the raw coal samples was established. The rationality and effectiveness of the model are verified by experiments.
Highlights
Compared with rock matrix, bedding is mostly a weak structure or weak plane. e bedding has an obvious effect on the physical and mechanical properties of rock [1], and the bedding effect has a significant impact on the construction and follow-up maintenance of geotechnical engineering, such as slope, tunnel, and traffic engineering [2]
There are few reports on the bedding effect on the deformation-damage differentiation of coal-rock mass under different loading modes. erefore, this article selects raw coal samples with parallel multibedding by ultrasonic, uniaxial compression tests and acoustic emission tests for damage detection were performed on raw coal specimens with parallel multibedding to study the bedding effect on the deformation-damage differentiation of coal-rock mass under different loading modes. e difference in the internal fissure evolution of coal-rock mass under different loading modes was revealed
Acoustic emission of rock materials is an elastic wave accompanying internal damage of rock materials [15], and there must be a correlation between acoustic emission and internal damage and failure of rock materials [16]. erefore, the degree of damage and failure of rock materials can be indirectly determined by monitoring the acoustic emission during the test of rock materials. (Limited by the length of this article, only the test results of raw coal samples V1-1, V1-2, P2-1, and P2-2 were analyzed.)
Summary
Compared with rock matrix, bedding is mostly a weak structure or weak plane. e bedding has an obvious effect on the physical and mechanical properties of rock [1], and the bedding effect has a significant impact on the construction and follow-up maintenance of geotechnical engineering, such as slope, tunnel, and traffic engineering [2]. Zhang et al studied the failure characteristics and acoustic emission characteristics of roof sedimentary rock with bedding using an uniaxial compression test and proposed a calculation method of in situ stress based on the Kaiser effect of acoustic emission [4]. Erefore, this article selects raw coal samples with parallel multibedding by ultrasonic, uniaxial compression tests and acoustic emission tests for damage detection were performed on raw coal specimens with parallel multibedding to study the bedding effect on the deformation-damage differentiation of coal-rock mass under different loading modes. Combined with the basic principle of continuous damage mechanics, the constitutive relation between acoustic emission cumulative ringing count and mechanical parameters of coal-rock mass with bedding was established based on the differentiation of the bedding effect. Combined with the basic principle of continuous damage mechanics, the constitutive relation between acoustic emission cumulative ringing count and mechanical parameters of coal-rock mass with bedding was established based on the differentiation of the bedding effect. e research results provide an effective basis for selecting key space-time areas for stress failure monitoring of coal-rock mass with parallel multibedding and can predict the damage evolution process of coal-rock mass with parallel multibedding under external load
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