Study On The Engineering Geological Characteristics Of Holocene Coral Reef Sediments In The South China Sea

Coral sediments as a kind of special geotechnical material is different from terrigenous sediments,with the vigorous development of the offshore oil industry,the south China sea reef construction deepens,sea power strategy,and the in-depth implementation of maritime silk road initiative,was widely attention in recent years,the focus is mainly on the sand,the engineering properties of sediment research,the study found that coral sand particles contain rich inner pore and has high edge Angle,the natural conditions between particles often have cemented structure.The mechanical properties of coral sand are completely different from those of terrestrial quartz sand,and are affected by many factors,such as chemical origin,biological composition,age of formation,particle size distribution,etc.However,the study on the sedimentary law of coral sediments and the mechanical properties of coarse and giant sediments is relatively weak.In this paper from the coral reef coral sediments in different facies belt of the south China sea,based on analysis of particles,biological composition analysis and determination of s research results,the reef sediments of the engineering geological points to distinguish with research work,revealed the spatial distribution of coral sediment,and the typical reef sediments,coarse grain and large grain soil large one dimensional compression test,reveals its compression deformation law.The main research contents and achievements of this paper are as follows:?1?Carried out laboratory particle analysis and experimental research on sediment cores obtained from six boreholes on a certain island in the south China sea.Based on the classification of Clark,A.R.,and Walker,B.F.,and referring to the national standard of engineering classification of soil and geotechnical engineering code,carried out the designation and stratification of sediments;Coral bone particles in typical sediments were selected to carry out ¹⁴C dating study,and the cross-facies zone sedimentary profile was constructed.The results show that the holocene coral reef sediments are generally poorly graded macrograined and coarse-grained soils,and the grain size of sediments gradually becomes smaller from the fore-reef slope to the island facies.Coral gravel sand was the main sediment in the gray-sand island facies and coralline breccia was the main sediment in other facies belts.The particle size analysis method is introduced to reveal the spatial distribution law of coral reef sediments.?2?Carry out the experimental study on the limit pore ratio of coral sediments,and discuss the main factors affecting the initial pore ratio of coral coarse soil.It is found that C_u and C_c are linearly correlated with the initial pore ratio.The particle shape also has a great influence on the initial pore ratio,and the rule is:sheet>massive>bar.?3?Carry out a large-scale one-dimensional compression experiment on coral coarse soil of different types and different levels,and discuss the compression law of coral coarse soil.It was found that the initial pore ratio was the main factor affecting the coarse coral soil,and the larger the initial pore ratio was,the greater the compressibility was.The larger the inhomogeneity coefficient C_u,the smaller the initial pore ratio and the smaller the compressibility of the sample.The larger the coefficient C_c,the larger the initial pore ratio and the lower the compressibility of the sample.?4?Carry out experimental research on particle crushing of coarse soil,and obtain the particle crushing rule of coral coarse soil in the process of one-dimensional compression.It was found that the relative particle crushing rate was positively correlated with the initial pore ratio.There was no decrease in particles less than 0.25mm before and after loading,which proved that 0.25mm was a relatively stable particle size in the process of compression of graded coral coarse soil.The coral-coarse soil at different levels had different particle sizes with the corresponding maximum particle size.