Experimental analyses of shearing mechanism of coral sand
SHE Yinpeng;LYU Yaru;LI Feng;YUAN Jianmin;College of Mechanics and Materials,Hohai University;State Key Laboratory of Disaster Prevention & Mitigation of Explosion &Impact,PLA Univ.of Sci.& Tech.;College of Field Engineering,PLA Univ.of Sci.& Tech.;College of Defense Engineering,PLA Univ.of Sci.& Tech.;
To investigate the shearing mechanism of coral sand and interfaces between coral sand and structures,the sieving tests,direct shear tests and scanning tests were carried out on coral sand sampled from a coral reef in South China Sea.In addition,direct shear tests on contact coral sands and steel,concrete and fiber reinforced polymer/plastic(FRP)were performed.The shearing mechanism was analyzed based on the particle size,mechanical behaviours and microstructures.It is found that the particle size is mainly from 0.3mm to 4.5 mm,taking up approximately 88% of the total mass.Special characteristics are observed from shear stress-displacement curves of coral sand.The internal friction angle of coral sand increases with an increasing particle diameter.The interface friction angle between coral sand and FRP composite material is smaller than that between coral sand and concrete,which is in turn larger than that between coral sand and steel.The interface friction angle between coral sand and structures is slightly larger than that between quartz sand and structures.There are many obvious cavities on coral sand with large particle size and the coral sand with small particle size has loose structure.The ratio of crushed grains to the total mass is defined as crush percentage,which increases logarithmically with an increasing particle size,and exponentially increases with an increasing axial stress.