Study On The Influence Of Particle Size Distribution Of Coarse-grained Soil On Compaction Characteristics And Particle Breakage

Coarse-grained soil has good engineering characteristics,and can be used locally for material,which is economical and convenient,so it is widely used in the construction of earth-rock dam.At present,the engineering characteristics of coarse-grained soil have been studied in depth,especially in laboratory tests,and fruitful results have been achieved.The in-situ test also has a relatively mature qualitative conclusion on the influencing factors of compaction characteristics,but the quantitative relationship between the influencing factors of compaction characteristics is relatively small.Based on this,the quantitative relationship between particle size distribution and compaction characteristics(relative density)of coarse-grained soil is studied through field rolling tests,and the relationship between the number of times of rolling and paving thickness of two variables and particle breakage in field rolling tests is analyzed.The field rolling test has the advantages of being close to the actual construction,and the measured test data can meet the engineering requirements,so it is widely used in practice.Firstly,the advantages and disadvantages of two commonly used grading formulas are analyzed and compared,and it is considered that the continuous grading formulas are more reasonable and applicable.Then,for the continuous grading equation,the influence law of relevant parameters is discussed,and the range of relevant parameters is preliminarily determined by combining curvature coefficient,non-uniformity coefficient and P5.Large-scale field rolling tests of main gravel and cushion materials under different paving thickness and rolling times were carried out by using construction site materials and machinery.The results were sorted out and fitted.Finally,the quantitative relationship between continuous grading formula and compaction characteristics(i.e.relative density)was analyzed.Based on continuous grading formula and two commonly used particle breakage indices Bg and Bw,the results were analyzed.The relationship model between compaction times,paving thickness and particle breakage was established.The following conclusions are drawn(1)Among the two parameters of the continuous grading equation,b value mainly determines the shape of the grading equation curve.When b<0.75,the grading curve is hyperbola,the smaller the curve is,the steeper the curve is;when b>0.75 the curve is inverse S shape,the larger the S shape is,the more obvious the S shape is;the value mainly determines the slope of the curve,the smaller the value,the gentler the grading curve is.(2)Compared with the traditional standard curvature coefficient and non-uniformity coefficient,the gradation equation can reflect the composition and properties of gradation more intuitively,and it is easier to adjust the relevant parameters to meet the engineering requirements.(3)The results of rolling test show that the correlation between parameters B and M is small in the continuous grading process,while the maximum particle size Dmax is positively correlated with parameters B and m,especially the correlation coefficient between B and maximum particle size Dmax is very good.The relation equation between Dmax and parameter m and the relation equation between parameter b,m and relative density can be set up to establish the relation between continuous grading equation and relative density.(4)Field rolling tests show that the paving thickness is inversely proportional to the particle breakage rate,while the number of times of rolling is proportional to the particle breakage rate.According to two commonly used quantitative criteria for particle breakage,the relationship model between continuous grading equation and paving thickness and rolling times can be established to deduce particle gradation before particle breakage.