| Taking the dynamic characteristics of silty soil modified by biological enzyme as the research object,the variation law of hysteresis curve,dynamic elastic modulus,damping ratio and cumulative plastic deformation of silty soil modified by biological enzyme was studied.Firstly,through the basic physical and mechanical tests,the influence of the amount of biological enzyme on the physical and mechanical properties of silty soil was studied,and the related physical and mechanical indexes of silty soil and the optimal amount of biological enzyme in silty soil improved by biological enzyme were obtained.Secondly,through a series of dynamic triaxial tests with different enzyme content,different confining pressures and different frequencies,the dynamic stress-strain relationship curve of silty soil modified by biological enzyme was obtained.Through the dynamic stress-strain curve,the morphological characteristics of the hysteretic curve were analyzed and the dynamic backbone curve was obtained.Finally,the dynamic elastic modulus,damping ratio and cumulative plastic deformation characteristics are analyzed by using hysteresis curves.The main research contents and relevant conclusions as follows。1.Main research contents(1)The basic physical and mechanical indexes of silty soil samples were obtained through the basic geotechnical tests,such as particle screening test,standard compaction test,limit moisture content test and direct shear test.Through the direct shear test,the optimum dosage of biological enzyme in silty soil was determined.(2)Using dynamic triaxial tests,the dynamic stress-strain relationship curves under different enzyme content,different confining pressures and different vibration frequencies were obtained.Using the four parameters of hysteretic curve inclination,width,density and area,the morphological characteristics of the hysteretic curve of silty soil modified by biological enzyme were analyzed.By analyzing the morphological characteristics of hysteresis curve,the stiffness and elastic properties,viscosity,meso-damage degree and energy dissipation capacity of silty soil modified by biological enzyme were obtained under the influence of enzyme content,confining pressure and frequency with the variation of dynamic stress amplitude.(3)According to the dynamic backbone curve and hysteresis curve,the characteristics of dynamic elastic modulus and damping ratio of silty soil modified by biological enzyme were analyzed respectively,and the variation rules of dynamic backbone curve,dynamic elastic modulus and damping ratio of silty soil modified by biological enzyme under different influencing factors were discussed.(4)According to the hysteresis curves of dynamic triaxial tests with different enzyme content and different confining pressures,the cumulative plastic deformation characteristics of silty soil modified by biological enzyme were analyzed by residual strain,and the variation law of cumulative plastic deformation with vibration order was discussed.2.Relevant conclusions(1)The effects of different contents of enzymes on the optimum water content and maximum dry density of silty soil are small,and the enzymes can effectively improve the shear strength of silty soil.When the content of enzymes is 0.01%,the shear strength of silty soil is the maximum.(2)By analyzing the morphological characteristics of hysteresis curve of soil samples,it was found that when the amount of enzyme was 0.01%and the frequency was 1.5Hz,under the same dynamic stress,the stiffness of silty soil was the largest,and the viscosity,meso damage degree and energy dissipation capacity were the smallest.Increasing the confining pressure could effectively improve the axial bearing capacity of soil.(3)The amount of soil enzyme has little effect on the damping ratio,the frequency has little effect on the dynamic backbone curve,and the confining pressure has great effect on the dynamic backbone curve,dynamic elastic modulus and damping ratio.It shows that the confining pressure has an important effect on the dynamic characteristics of enzyme improved silty soil,and increasing the confining pressure can significantly improve the soil strength.(4)The cumulative plastic strain increases with the increase of vibration times,but the change of vibration times has little effect on the cumulative plastic strain. |
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