Research On Dynamic Characteristics And Consolidation Theory Of Soft Clay

With the implemention of the national ocean power strategy,China's ocean engineering has developed rapidly.The Zhoushan Islands guard the gate of the East China Sea.Due to its special geographical location,a large number of island construction projects have also been launched.For example,in the new area of Zhoushan Islands,the Zhoudai Cross-sea Bridge,the Yushan Island Green Petrochemical Base,and the upcoming Yongzhou Railway Project Full implementation.However,in complex and changing marine environment,the mechanical behavior of marine soft clay is extremely susceptible to dynamic loads such as earthquakes,waves,traffic,etc.,which causes the stability of the soil to decrease,which gives a great threat to engineering construction and marine infrastructure operations.Due to the special physical properties of soft clay,which is both viscous and elastic,it belongs to viscoelastic soil,which is mainly characterized by rheological properties.For the study of the consolidation theory of soil,the classic one-dimensional consolidation theory was first proposed by Terzaghi,but this theory exists certain limitations.Therefore,domestic and foreign scholars have done a lot of improvement and research based on this theory,so far good research results have been obtained.However,in the theoretical study of consolidation of special soft clay,no explicit and reliable conclusion has been obtained.Therefore,it is of great practical significance to strengthen the research on the dynamic characteristics of marine soft clay soil layer under cyclic loading.In combination with the results of dynamic triaxial experiments,the effective one-dimensional consolidation of saturated soft clay can be further explored.Perfecting the one-dimensional consolidation theory of soft clay can also provide necessary technical and theoretical support for infrastructure construction and economic development in island areas.The main work and results are as follows:1.Based on the dynamic triaxial instrument manufactured by WillE,an indoor dynamic triaxial test has conducted by stress controlled loading method.relevant experiments were Carried out to study on the dynamic strain,cumulative pore pressure,and dynamic elastic modulus of marine soft clay in the Zhoushan Islands in the East China Sea under cyclic loading were affected by the number of cyclic loads,cyclic stress ratio,and confining pressure.In addition,the experimental results of the dynamic strain with the number of cycles and the dynamic elastic modulus with the dynamic strain were tested by using the Monismith power model and the H-D correction model,respectively,and obtained the consistent fitting results.2.The undisturbed soil samples and the soil samples loaded with different cyclic stress ratios were respectively subjected to electron microscopy scanning tests,and the internal microstructure and connection methods of the soil particles were analyzed in combination with the scanning electron microscopy results.Based on the microscanning results of soil samples after loading with different cyclic stress ratios,the micro-failure mechanism of Zhoushan marine soft clay under different cyclic loading was explained,and the micro-mechanism explanation of stiffness softening of soil samples after dynamic loading was given.3.Based on the viscoelastic Kelvin model and the Laplace transform method modified by the fractional-order elastic pot under the condition of double-sided semipervious water,the theoretical equation of one-dimensional consolidation of clay under cyclic load of sinusoidal waveform was obtained,and the inverse method was adopted by the Crump inversion method.To find the semi-analytical solution of the consolidation equation.The modified viscoelastic Kelvin model of this paper is degraded to Terzaghi model,and compared with the literature results.The consistent comparison results verify the feasibility and correctness of this revised model.4.For saturated soft clay,combined with the improved fractional Kelvin model introduced by the elastic pot element,taking into account the characteristics under different waveform cyclic loads,the Laplace transform was used to derive its onedimensional consolidation semi-analytical solution.The effects of top boundary parameters,fractional order,viscosity coefficient and compressive modulus on the consolidation settlement and pore water pressure of saturated soft clay were analyzed in detail,and the mechanism of consolidation settlement of saturated soft clay was given.