Dynamic Characteristics Of Coral Sand In The Condition Of Particle Breakage

With the implementation of the strategy of"Marine potestatemr",more and more offshore projects and island reef projects are being or will be constructed.Coral sand is a common foundation soil and filling material in offshore engineering and island reef engineering.It has the characteristics of brittleness and easy breakage.The natural or artificial foundation formed by coral sand is often subjected to large overburden pressure or compaction function during construction,resulting in particle breakage.In addition,coral sand foundations will be affected by dynamic loads such as traffic loads,earthquakes,and wind loads in engineering.The impact of particle breakage on the dynamic characteristics of coral sand is very important to the structural safety of offshore engineering and island reef engineering.In this paper,the coral sand in the South China Sea is taken as the research object and samples with different particle breakage degrees were prepared by one-dimensional consolidation test,and the samples were subjected to GCTS resonant column test and GDS dynamic triaxial test to study the impact of coral sand particle breakage to dynamic characteristics and liquefaction resistance.The main research results and conclusions are as follows:(1)When the consolidation pressure is 200k Pa,the coral sand has obvious particle breakage,and its’Hardin relative breakage increases with the increase of consolidation confining pressure,but under the consolidation pressure given in this test,its growth rate is gradually slowing down,when the consolidation pressure increases from 200k Pa to1200k Pa,its’Hardin relative breakage increases by 24%.(2)The particle breakage of coral sand has an important effect on its liquefaction resistance.By establishing the relationship between Hardin’s relative breakage and liquefaction resistance CRR,it is found that with the increase of particle breakage,the liquefaction resistance of coral sand generally decreases.Compared with the original unbroken coral sand,the liquefaction resistance of the coral sand decreased by 30%under the breakage degree corresponding to the one-dimensional consolidation pressure of 1200k Pa.(3)The maximum dynamic shear modulus of coral sand increased first and then decreased with the increase of breakage degree,and the maximum dynamic shear modulus of coral sand reached the maximum value when the one-dimensional consolidation confining pressure was400k Pa and the maximum dynamic shear modulus is increased by about11%compared with the unbroken original coral sand sample.(4)Based on Hardin’s relative breakage,this paper proposes a modified relative breakage B_r’to characterize the breakage of coral sand particles.This index and the maximum dynamic shear modulus are in line with the Gauss function relationship,which can reflect the relationship between the degree of coral sand particle breakage and its dynamic shear modulus.(5)The Darendeli viscoelastic constitutive model is modified based on the proposed modified relative breakage,and a viscoelastic constitutive model of sand soil that consider the effect of coral sand’s particle breakage is established,and the model parameters are given.