Particle Breakage Research Of Calcareous Sand Under Confined Compression

The domestic and foreign researches for particle breakage of granular soils aremainly focused on the dynamic and static characteristics and the influencing factorsunder high stress level, so the researches under low stress level are much less. Inaddition, the mechanisms of particle breakage of granular soils are complex andaffected by many factors, so there are lots of inconveniences to study as it is oftenrestricted by objective conditions in the process. Therefore, the phenomenon ofparticle breakage under low stress level is worth thinking and studying deeply.This paper is based on the National Science Foundation (number:50778140),and the particle breakage of calcareous sands are studied in the confined compressiontests under low stress level based on that the basic physical and chemical propertiesare ascertained. The research methods and main outcomes are as follows:(1) The qualitative and quantitative analyses are provided by using fluorescencespectrometer. The surface morphology and structural characteristics of calcareoussands with different size are observed by using scanning electron microscope (SEM)imaging respectively.(2) The confined compression tests of calcareous sand are provided, and theresults show that the compression deformation of calcareous sands are mainly plasticdeformation; It has the most severe compression deformation in the initial stage of theloading, and the compressibility is related to the loading and the particle size ofsample.(3) The shear strength parameters of calcareous sands are measured by using thedirect shear tests, it is concluded that the internal friction angles of calcareous sandsparticles are larger than general quartz sands, and the internal friction angle increaseswith the increase of particle size, but the tendency is alleviated.(4) The grain size analysis tests are conducted for the samples which are aftertests: the sieving method is used for the particles that sizes are greater than0.1mmand the laser scattering method is used for the particles that sizes are less than0.1mm,and the grading curves are drew from the micron level to the largest particle size.(5) The Hardin relative breakage rates are calculated based on the grading curves, and the relationship between the grain crushing amount and the load is explored. Theexperience formula is concluded, and the concept of crushing stress is modified afterdeducing the experience formula.(6) The relationship between Hardin relative breakage rate and Einav relativebreakage rate is analyzed, and the region of the size of the two definitions of particlebreaking boundaries, the limited grading, the current grading, the initial grading andcoordinate are divided into five parts: S1~S5, and the result show that S5~lgP hassignificant index function relation suggested that S5and lgP have some internalrelationship.