Analysis Of Factors Influencing Physical And Mechanical Properties And Experimental Research On Manufacturing Methods Of Tectonically Deformed Coal's Moulded Coals

In the laboratory test of mechanical properties of broken coal and rock mass,the common method is to use moulded coals instead of raw coal for test and use moulded coals to reflect the mechanical properties of raw coal.Based on the measurement of the physical properties of tectonically deformed coal,the parameters of the density,wave velocity,uniaxial compressive strength and elastic modulus of tectonically deformed coal's moulded coals are obtained,and the effects of the forming pressure,holding time,loading rate,pressing layers,curing time,curing temperature,curing mode and moisture content on the parameters of the moulded coals density,wave velocity,uniaxial compressive strength and elastic modulus are studied.Based on the orthogonal test of three factors of particle size distribution,forming pressure and moisture content in the preparation of tectonically deformed coal's moulded coals,particle size distribution,the main control factor of physical and mechanical properties of moulded coals,is determined.The differences of density,wave velocity,strength,cohesion,internal friction angle modulus and Poisson's ratio of moulded coals with eight kinds of particle grading are compared,and the changing relationship and mechanism between particle grading and physical and mechanical properties of moulded coals are revealed.Based on the analysis results of influencing factors of tectonically deformed coal's moulded coals forming,and the comprehensive evaluation indexes of density,wave velocity and strength,the standard of moulded coals making is explored to form a complete system of tectonically deformed coal's moulded coals making and influencing factors.The following conclusions are obtained:?1?The influence of moulded coals forming pressure,holding time,loading rate,number of pressing layers,curing time,curing temperature,curing mode and moisture content on moulded coals density,wave speed,strength,modulus of elasticity and other physical and mechanical parameters was analyzed,and the mechanism of different influencing factors on moulded coals physical and mechanical properties was explained.?2?Through the orthogonal test of molding pressure,particle gradation and moisture content,it is found that the particle gradation has obvious influence on the density and strength of moulded coals,and it has a strong linear correlation with the three evaluation indexes of density,wave speed and strength,which shows that the particle gradation determines the physical and mechanical properties of moulded coals to a large extent.?3?Particle size has a significant impact on the physical and mechanical properties of tectonically deformed coal's moulded coals.Therefore,uniaxial and triaxial full stress-strain tests were carried out for eight different graded moulded coals.The differences of density,wave velocity,strength,cohesion,internal friction angle,elastic modulus and Poisson's ratio of tectonically deformed coal's moulded coals with different particle size were compared,and the rules and causes of the changes of parameters with the particle size of moulded coals were analyzed.The corresponding relationship between the strength,elastic modulus,Poisson's ratio,cohesive force,internal friction angle and the grading characteristic value of moulded coals was studied,and the mechanism of particle size matching physical and mechanical properties of moulded coals was obtained by combining the microstructure analysis of moulded coals particle composition.?1?The quality and density of moulded coals formed by coarse particles are large,but the compactness is low,resulting in small wave velocity,cohesion,strength and elastic modulus;the compactness of moulded coals formed by fine particles is high,with large density,wave velocity,elastic modulus,strength and cohesion.The results show that the coarse particles are not conducive to the stability of moulded coals properties,and the more the proportion of fine particles,the higher the strength.?2?The cohesion decreases with the increase of particle size,and the decrease range is very obvious when the particle size is small?0.1-2.6mm?,but not obvious when the particle size is large?>2.6mm?;the internal friction angle increases with the increase of particle size as a whole,it can be considered that the coarser the particle size,the greater the internal friction angle of moulded coals.?3?The elastic modulus and Poisson's ratio decrease with the increase of moulded coals particle size.The main reason is that more pores in the moulded coals will reduce the compactness,and the number of pores in the moulded coals determines the compactness.According to the analysis,the elastic modulus and Poisson's ratio of the moulded coals are affected by the compactness.?4?The gradation characteristic values d₁₀,d₃₀,d₅₀,d₆₀ have a good corresponding relationship with the physical and mechanical parameters of moulded coals.The analysis shows that the uniaxial compressive strength,elastic modulus,and viscosity of moulded coals when the particle size range between 0-3mm,the cohesive force will decrease rapidly with the increase of the particle size.After the particle size more than3mm,it will slowly decrease.However,the wave velocity,internal friction angle,and poisson's ratio of moulded coals showed a downward trend as the moulded coals particle size increased.?5?By analyzing the microstructure of different particle grading moulded coals,the internal structure of moulded coals can be divided into skeleton structure,suspension state,filling state and dense structure according to the contact state between the particles.The internal force and strength of moulded coals formed according to the four contact states will increase in turn due to the different inter particle forces in different contact states.?4?Based on the analysis results of forming pressure,holding time,loading rate,pressing layers,curing time,curing temperature,curing mode,moisture content and particle grading and other influencing factors in the process of making tectonically deformed coal's moulded coals,taking the density,wave speed and strength parameters of moulded coals as evaluation indexes,the making standards of moulded coals under different evaluation indexes are determined,and the density,wave speed and strength are integrated The degree evaluation index forms the production method of tectonically deformed coal's moulded coals.There are 55 figures,38 tables and 100 references in this paper.