Study On Small-strain Dynamic Properties Of Sand In Anisotropic Consolidation

Small strain dynamic parameter is important parameter in geotechnical engineering.Lots of science researchers have acquired many conclusions.But,Soil consolidation process is limited by instrument which did not match the practical engineering well.This paper briefly summarizes the research achievements of previous scholars.Resonant column apparatus and true triaxial apparatus with bender-extender elements were employed to achieve the effect on small strain dynamic parameter for sand in anisotropic consolidation.The specific research content as follows:(1)The traditional Stokoe resonant column is improved by iron wire and weights to achieve two-directional anisotropic consolidation.Shear modulus of sand was measured under two-directional anisotropic consolidation by resonant column apparatus.The result shows increasing kc increased G0.The effect of kc on G0 was significant when specimens were in loose state under low confining pressure.Additionally,kc had little effect on the shear modulus reduction curve.Finally,a four-parameter formula for G0 under kc>1 was established.(2)True triaxial apparatus with bender-extender elements were employed to achieve combined S-wave and P-wave tests on sand under three-directional anisotropic consolidation.The results show that the intermediate principal stress has little effect on G0 and M0 when the major and minor principal stresses keep constant.G0 and M0 increase with an increase in major or minor principal stress when the other two principal stresses remain unchanged.The major principal stress has great effect on M0 while the minor principal stress has significant effect on G0 in tests under indentical conditions.Tests with constant mean principal stress p and intermediate principal stress coefficient b indicate that an increase in b results in a non-linear decrease in G0 and M0.Moreover,increasing p(i.e.,increasing major and minor principal stresses simultaneously)leads to an increase in G0 and M0 while increasing generalized shear stress q results in a decreased G0 and an increased M0.(3)True triaxial apparatus with bender-extender elements were employed to achieve dynamic tests on sand under three-directional anisotropic consolidation.The result shows that the increasing b limit the growth of accumulation strain and strengthen rebound modulus when the major principal stress and the minimum principal stress are stable.If the value of b is 0.5,the small shear modulus G0 is maximum.Under the consolidation whose p and b is stable,if the value of b is 0.25,accumulation strain is maximum,degradation index and rebound modulus are minimum after the same number of cycles.The small shear modulus increases with reduce of b.