| The structure of the soil refers to the arrangement characteristics(geometric characteristics)and the connection characteristics(mechanical properties)of the particles in the soil.The former is called a fabric and the latter is called a particle connection.Due to the different sedimentary history and sedimentary environment,the soil will form different internal structures.The anisotropy and nonlinearity exhibited by the soil are macroscopic manifestations of changes of the internal structural elements of the soil.Structurality is an important characteristic of soil,which has a significant impact on the mechanical behavior of the soil.For sandy soils,the arrangement characteristics(fabric)of particles in soils are the main factors affecting their mechanical properties.In the past,the study on the mechanical properties of the sand,especially the small strain dynamic characteristics,is not sufficient.Therefore,the preparation of two kinds of sand samples is realized by the two methods of dry deposition(DD)method and moist tamping(MT).The experimental study of small strain dynamic characteristics of sand samples under different initial fabrics is carried out by using the resonance column instrument.The specific research content as follows:(1)Experiment on Toyoura sand samples prepared by two different fabrics was carried out by using Resonance Column Instrument.The effects of different confining pressures and different relative densities on dynamic shear modulus and damping ratio under different fabrics are discussed.Studies have shown that the difference in maximum shear modulus(G0)values for different fabrics at the same void ratio is small under low confining pressure.The G0 of DD and MT increase under high confining pressure.The effect of fabric on the normalized dynamic shear modulus and strain relationship curve is small.(2)Sand specimens with different initial fabric were prepared in the laboratory by resonance column apparatus.The time effect experiments of different conditions were carried out.The results show that the influence of the time effect of the DD sand samples on the shear modulus is greater than that of the MT sand samples.At low confining pressure and low densities,the time-effect amplitudes of the two fabric samples differ the most.The influence of the time effect of the MT sand samples on the damping ratio is greater than that of the DD sand samples under low pressure.The influence of the stress history on the time effect of the DD sand samples is larger than that of the MT sand samples.(3)The traditional Stokoe resonance column was modified.The effect of different sand fabrics on the small strain shear modulus under anisotropic consolidation was studied by improving the post-resonance column.Experimental studies have shown that under low confining pressure,the effect of kc on the shear modulus of the DD sand samples is more obvious than that of the MT sand samples.Under high confining pressure,with the increase of densities,kc has little effect on the shear modulus of the two structural samples,although the confining pressures and the relative densities are different,but the different fabric has almost no effect on the normalized shear modulus attenuation curve. |
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