The Mechanism Of Aggregation Packing Based On The Individual Characteristics Of Coral Particles

In recent years,with the strategic needs of national economy,energy and security,it is urgent to promote the construction of the South China sea reef project.Considering the high cost of long-distance transportation of traditional aggregate such as crushed stone,and coral material is the only building material in the South China Sea,the basic application research is imminent.Based on the background of structural fillers such as airport runway,revetment and breakwater in the construction of islands and reefs,and the problems such as irregular geometry of coral debris particles,abundant inner and outer pores,high water absorption and so on,which lead to insufficient compactness and low bearing capacity of hydraulic fill foundation,a systematic study on the mechanism of aggregation dense pile associated with individual characteristics of coral particles was carried out.The main research contents and conclusions are summarized as follows:(1)The characteristics of abundant inner and outer pores of coral particles were analyzed by SEM and mercury injection test,and the characteristics of high water absorption caused by the pores were revealed by water absorption test.Lastly,the low strength of coral particles,pores filling and Strength hardening after cement wrapping was revealed by particle strength test.(2)On the basis of particle image acquisition and analysis,the equivalent ellipse reference method and complex Fourier analysis method for coral particle geometric description are proposed.And based on the correlation analysis of two kinds of geometric indexes,the evaluation system of shape and angular of particle characteristics is proposed.Further quantitative statistics revealed the distribution characteristics of irregular particles of coral aggregate.(3)Based on the principles of inverse Fourier transform,grading transformation and digital image analysis,the physical mechanism of aggregate packing simulation method is proposed.The packing process includes particle digitization,particle movement(translation and rotation),collision detection,vibration simulation and the extraction of packing structure parameters.(4)The packing simulation analysis,related single level geometry of particle shape,angular features and surface texture,reveals that limiting the content of irregular particles in needle bar(F_S>0.4)and angular(F_C>0.5)in aggregate can improve the compactness of packing structure,limit the the distribution of macropores and play the role of framework between aggregates.(5)The packing simulation related the particle geometry characteristics reveals the decrease of structure density and the increase of macropores volume distribution with the increase of the content of irregular particles.On this basis,the contact conceptual model of ideal single grain,irregular single grain,and honeycomb of arch frame is proposed.The content of irregular particles should be limited to less than 1/2 or more strict 1/4.The simulation analysis of the correlation of the upper limit particle size shows that the increase of the upper limit particle size of coral aggregate to 53mm is conducive to the denser accumulation structure.In practical application,it can weaken the large surface area of the system,which is the combination of coral particle surface roughness and more fine particle.Based on the simulation analysis of the particle size distribution,it is verified that the effect of large void ratio caused by the irregular particle size of coral aggregate exists objectively,and the setting of fine fraction(P5)is more than 40%,which can reduce the distribution of large void in the dense system,and make the accumulation structure more compact.On this basis,the evolution of irregular skeleton gap to much suspension density and few suspension density of coral packing accumulation structure with the increase of fine aggregate content is proposed.(6)On the one hand,the vibration compaction test results of coral aggregate verify the influence mechanism of upper limit particle size and particle size composition in physical mechanism packing simulation.On the other hand,it reveals the basic characteristics of special geometric and physical characteristics of coral,resulting in the high optimal water content(about 14%)and high cement composition(>6%)in the design of cement coral aggregate.