Study On The Relationship Between The Strength Of Limestone Single-grained Aggregate And Simple Grade Ingredients

At present,coarse-grained soil fillers have been widely used in airport filling engineering,but studies have found that coarse-grained soil fillers will show significant particle breakage under external load,which will lead to the particle size distribution curve and internal particles of coarse-grained soil fillers.The change of the shape affects the engineering characteristics of coarse-grained soil fillers,and poses potential safety hazards during the construction and operation of the airport.Based on this,this paper has carried out research on the influence of the particle shape of coarse-grained soil on crushing,the impact of particle crushing on gradation and the effect of gradation on shear strength.This article uses advanced image acquisition and processing technology to analyze the particle shape of different particle groups.Then obtain the shear strength of the coarse-grained soil filler through a large triaxial compression tester,and sieve the samples after the sample preparation and the triaxial compression test are completed to obtain the content of each particle group,calculate the crushing rate and after the test The shape index of the shape,and through the particle flow software PFC(2D)as a platform to analyze the mesostructure of coarse-grained soil and finally draw the following conclusions:(1)Compared with the grain group 10-20 mm and the grain group 20-40 mm,the contour index between the two grain groups is quite different.The shape of the particles shows a significant size effect.The smaller the particle size,the smaller the angularity of the particles,and the closer the shape is to a circle.After the test,the particle group 10-20 mm and the particle group 20-40 mm in different gradations become narrower and longer than before the test,and the irregularity of the shape increases;as the confining pressure increases,the particles in the same gradation become larger Narrow and long,the irregularity of the shape increases.The shape change in the sample preparation stage can be ignored,and the shape change in the sample preparation stage has little effect on the change rule of the shape index.The correlation between the shape index and the confining pressure is poor.(2)As the confining pressure increases,the relative breaking rate of the particles also increases,and the linear relationship between the two is good.The relative crushing rate is related to the particle size.Under the same confining pressure,the larger the particle size,the easier the particles are to break,and the larger the particle size,the faster the relative crushing rate increases with the confining pressure.By comparing the relative crushing rate of coarse-grained soil broken in the sample preparation stage and neglected in the sample preparation stage,it can be found that ignoring the particle breakage in the sample preparation stage will make the calculated value of the relative breakage rate too large and cannot be ignored.(3)Based on the single-grain sample,a method for predicting the particle size distribution curve of the triaxial test under different confining pressures is proposed.Approximately unique relationship.This relationship can be expressed by a power function.The fractal dimension can be used as a quantitative index for particle crushing,and the overall shape of the sample can be related to crushing.Each crushing rate can only express the crushing of the whole sample.Based on a simple gradation,the crushing rate of the particle group is proposed to show the crushing situation of each particle group in the sample.(4)The strength of the single-grain group is less than that of the mixed-grain group.The single-grain group and the mixed-grain group have poor gradation.Linear fitting will produce a large amount of pseudo-cohesion.At different gradations,the shear strength of coarse-grained soil increases with the increase of the content of large particles in the sample.When the content is too high,the particle breakage will reduce the strength,and the overall strength will increase first and then decrease.(5)When the slope k of the particle's relative crushing rate is greater than a certain value,the increase in particle crushing will cause a significant decrease in the internal friction angle ?.According to PFC(2D)mesoscopic analysis,as the content of large particles in coarse-grained soil samples increases,the proportion of strong chains increases and the strength increases.When the content of large particles increases beyond a certain limit,the strength will decrease.The coordination number and the crushing relationship are good,and the crushing rate increases as the coordination number increases.(6)The strength of the mixture is controlled by the content of each particle group and particle breakage.Based on this,the formula for calculating the internal friction angle of the mixture based on the particle group content and particle breakage rate is proposed,and the calculation result is compared with the test value.The result proves the calculation The method can effectively reflect the change law of the mixture strength with the content of the particle group and the particle breakage rate.