Research On The Coupling Relationship Between The Microstructure Characteristics And Mechanical Properties For The The Calcareous Sand

In this paper, the coupling relationship between microstructures andmechanical properties of Calcareous sand in Coral reef sites werecomprehensively analyzed. The dry density of Calcareous sand with differentwater content, the evolution of microstructures and its correlation with themechanical properties and the influence of these characters on theengineering geological properties were all analyzed in detail. During theanalysis process, extraction of micro-structural features after sand compactiontest and direct shear test were used as the main approaches. The researchcontents and main conclusions are as follows:1. Main parameters of Calcareous sand were obtained by serious ofin-situ tests such as shallow plate load test, spiral plate load test, rebound testand so on. Parameters such as particle size, moisture content, density,cohesion, internal friction angle and bearing capacity were investigated fromthe aspects of influence parameters and evolution characteristics.2. During the sample preparation process, a new method for obtainingundisturbed sand sample after compaction test was proposed. The methodguarantees the sample undisturbed by adding dilution water and gelatin inaqueous solution diluted by iso-amyl acetate2-cyanoacrylate.3. Micro-structure of the coarse grained soil were analyzed based on thedata obtained through lab tests. The arrangement of calcareous sand particlesand evolution characteristic of pore were discussed. The results indicate thatgrain group that contains large grains is the internal reason which controls thedensity of calcareous sand, while the change of moisture is the external one.4. A good coupling effects between the average rotation entropy andshear strength were observed. A constitutive relations of shear strength wasproposed. The correlation between moisture, dry density and shear strengthwere shown by a newly established expression which is expressed withparameters such as average rotation entropy, dry density and moisture. In the last part, the research results were summarized briefly，the outlookof researches on calcareous sand was discussed.