Experimental Study On Breakage Characteristics Of Andesite Gravels Under Impact And Static Loading

The recent researches on particle breakage lack specific analyses of the breakage factors and accurate descriptions of the characteristics of particle breakage.Therefore,this paper selected andesite gravels as the experimental material,firstly carried out the experimental research on single particle characteristics under uniaxial compression force state and multi-directional stress state in the "V"-shaped groove.Furthermore,the particle breakage tests of single-grad gravel under impact loading and static loading were conducted.This research concentrated on the influence of particle shape,particle size,loading magnitude and loading types to particle breakage.As well as the applicability of breakage index,the strength-deformation characteristics and evolution law of:fragmentation were discussed.This paper contains the following conclusions:(1)In the uniaxial compression state,the regular block failure forms were simply tensile cracking;while the failure forms of irregularly shaped particles were related to the number of contact points.Under the circumstance of regular shape particles breakage in the "V" groove,the damage forms were different between "line-line-face" contact and "line-line-line" contact.While for irregular shape gravel in the "V" groove,the generation location of break cracks was related to the points of contact.Therefore,the analysis showed that if particles shape,contact points and the force-receiving forms were different,the particles damage forms were different.(2)Under the impact loading and static loading,the applicability of the particle breakage indexes was first explored.For different single particle groups and different shapes,the crushing indexes Br and Bg were better for describing the aggregate particle breakage.Moreover,for the mixed particle group,the fractal dimension D could also be used as an effective breakage index.(3)Under the impact loading,particle shape,particle impact times N and particle size were coupled to affect particle breakage.Under different conditions,the main controlling factors affecting particle breakage were also different.The degree of particle breakage was related to particle shape,and the particle breaking characteristics were found by marking single particles of the gravels.There was also a good linear relationship between particle times and breakage index,and the fitting formula parameters were related to the particle shape.The influence of particle size to breakage was more obvious as impact times increasing.According to the curve of the increment of the crushed volumetric strain ??v and the breakage index Br,the particle volumetric transformation process was divided into three stages:?.void filling,?.skeleton failure,?.final stability.(4)Under the static loading,the linear relationship between breakage index and static load F was in good agreement.The particle shape affected the degree of particle breakage.The breakage stress and compaction index were related to the particle shape through the analysis of the e-lgp curve.(5)Under different types of loadings,the particle breakage e,volution laws were same,that is,under the condition of single particle group,the large particles were broken into secondary particles.The content of secondary particles had a limit point,that is,reaching the specific times of impact loading or the static loading,the particle content no longer increased,but decreased.The content of particle finally conformed to normal distribution.