The Study And Test On Dynamic Properties Of Recently Deposited Soils And Vibratory Liquefaction Of Sands In Area Of Nanjing And Its Neighbor

In this dissertation, the studies on dynamic behavior of soils and liquefaction potential of saturated sands are briefly reviewed. Liquefaction of saturated sands is a greatly complicated phenomenon. Its generation, development and dissipation are restricted by physical property, stresscondition and boundary condition of soils. In addition, there are a lot of influencing factors such as density, structure property,clay content, degree of saturation, gradation, hydraulic conductivity, initial stress condition and dynamic load character and so on. The researches of dynamic behavior and liquefaction potential of saturated sands have been further. However, more and more macroscopic liquefaction phenomena and experimental investigations show that different depositional environments lead to different structure of soils, while the influence of structure property of soils on liquefaction resistance is no less than that of density and consolidation stress and so on. Ancient alluvial flat deposits, namely recently deposited soils, are easier liquefaction during earthquake. On the other hand, among recently deposited soils of Nanjing and its surrounding areas, there are two types of soils with special structure, that is, Silty clay and fine sand interbedded strata of Nanjing with appearance presenting .thousand layers cake. and Nanjing fine sand with schistous grain. Up to the present, to dynamic character and liquefaction resistance of both fine particle soils with special structure, nobody has researched more profoundly. So, it is of critical importance to study dynamic properties and their liquefaction potential of recently deposited soils of Nanjing and its surrounding areas during earthquake. In this dissertation, free vibration column tests are performed on undisturbed specimens of recently deposited soils of Nanjing and its surrounding areas. The influences of soil structure, confining pressure and strain amplitude on dynamic properties of recently deposited soils of Nanjing and its surrounding areas are discussed. Furthermore, based on test results and theoretical analysis, the averaging curves, recommended values and envelopes of dynamic shear modulus ratio GGmax and damping ratio λ versus dynamic strain γ for recently deposited soils of Nanjing and its surrounding areas are presented. By use of vibration triaxial apparatus, Nanjing silty clay and fine sand interbedded strata and Nanjing fine sand were tested and their test results are discussed. In this paper, the influences of consolidation ratio and effective K cII ABSTRACT ' consolidation stress σ 3on liquefaction resistance of two types of soils are considered.