| In the overall situation of promoting the marine construction in China, sand is essential building material. The sea sands generally exist in different sea areas, and their natures are significantly different. Therefore,study on the physical property, chemical property, water physical property, mechanical property, micro-/ meso-Structure,which of formation of porous biological debris of sand and terrigenous mineral sand, and discover the rules.It has practical significance for the construction of marine infrastructure. Through a series of laboratory tests, this paper measures and describes the physical and chemical properties as well as mechanical parameters of the sea sands, analyzes the microstructure characteristics, and explores the nature differences of various sands. The sea sand from five locations,including Q ingdao, Taizhou, Xisha and Nansha, as the research object(for easy record were denoted as Q sand, T sand, X sand, Z sand, N sand). The main research contents and conclusions are as follows:1. For the mineral composition analysis of the sea sand by using X ray diffraction, Q sand minerals are mainly feldspar, quartz, zinc phosphate and zircon; T sand mainly consist of quartz, microcline, albite, iron sulfate.The content of CaCO3, Z and N of X sand sand sand was more than 50%, are calcareous sand. In addition to the main mineral composition of calcareous sand calcite. And the mineral composition of N sand and magnesium calcite.2. Five sea sands sieve analysis test,and the relationship between the coefficient o f nonuniformity is CuQ<CuT<CuN<CuX<CuZ<5; The relationship between the curvature coefficient of the sea sand is Cc T <CcZ<1<CcN<CcX<CcQ<3. Q, X, N sand gradation means good continuity, and gradation of T sand and Z sand means poor continuity.3. The composition and origin of sand are different, and the physical properties and water physical properties are quite different.Because of the difference of the inner pore and the reason of the formation of the calcareous sand,The maximum dry density of N sand and Z sand is smaller than that of X sand. Compared with pure terrigenous mineral detrital origin T sand and Q sand, the maximum dry density to 20%. Based on the inner pore of calcareous sand can save water, The optimum moisture content of N sand and Z sand were the highest, X sand times, T sand and Q sand were the lowest.4. The sand’s three axial compression shear strength is greater than the direct shear strength.(1) Calcareous sand shows an advantage in granule strength, coarse and fine particles between the occlusal strength, because of the complex and rough surface of the particles, make it has the inner pore and the pore space due to the internal pore,and has highternal friction angle and peak shear strength value.(2) Calcareous sand main force difference(peak value) and the axial strain are higher than sand for T sand and Q sand, which indicates calcareous sand need more axial load under the same confining pressure conditions.The axial strain of the calcareous sand contains both the axial compression deformation and biological pores of the sand particles in the shear resistance and particles in the partial cut or broken particles, whose plastic deformation is larger than the T sand and Q sand.5. Under the same water content conditions, the average abundance and average roundness of N sand and Z sand particles is less than T sand and Q sand, which shows that the inner pores of N sand and Z sand make the particles more complex surface morphology. And the complex shape of the particles directly affects the ro undness of the pores. The porous medium and the dense medium have obvious influence on the particle shape, particle composition and the derived pore properties of the sand.The maximum probability entropy of calcareous sand was significantly lower than the maximum probability entropy of T sand and Q sand, which showed that the calcareous sand of the biological clastic formation had better stability. |
