Study On One-dimensional Consolidated Fractional Viscoelastic Model

Saturated soft clay is widely distributed in coastal,riverside and lakeside areas of China.Soft clay foundation has the characteristics of high compressibility,low permeability and remarkable rheological characteristics,resulting in a long duration of consolidation deformation,so the calculation of consolidation theory is very important in civil engineering design.Since Terzaghi proposed the classical one-dimensional consolidation theory based on the six-point hypothesis in 1925.Many scholars at home and abroad have carried out a lot of research on the revision of their assumptions based on experiments,and the classical consolidation theory has been constantly improved and developed,so far it has achieved good results.However,due to the special physical characteristics of soft clay,a reliable conclusion has not been reached on the consolidation theory of soft clay.In this paper,the one-dimensional consolidation problem of saturated soft clay will be deeply discussed by means of literature research and fractional viscoelastic theory analysis,so as to further develop and improve the one-dimensional consolidation theory of soft clay and provide a theoretical basis for the practical needs of engineering.The main work and achievements are as follows:1?For the description of the classic soft soil viscoelasticity Kelvin model and the measured data of literature,this article,Abel sticky pot model for fractional order of the calculation results,the Kelvin model calculation results and experimental results are compared,the results showed that choosing appropriate parameters of fractional order fractional model better than the Kelvin model void water pressure and settlement of soft clay.2?The response of integer order Kelvin model and modified Abel viscoelastic model to void water pressure and settlement was compared under step load.Based on different fractional order,the viscous coefficient and compression modulus,detailed analysis of the fixed fractional Abel sticky pot model and the integer order consolidation settlement of soft clay under the Kelvin model,the results show that the fractional order is smaller,the greater the viscosity coefficient,the modulus of elasticity,the greater the correction fractional Abel stick pot model is better than integer order Kelvin model can reflect the soil pore pressure dissipation in the situation.The validity of fractional order correction Abel clay pot model is demonstrated again.3?The differential equation of fractional viscoelastic effective stress is established.Taking the bilateral continuous drainage physical model as an example,the semi-analytical solution of one-dimensional consolidation settlement of soft clay under constant load is obtained by using the Laplace transform technique.Finally,the numerical solution of effective stress and settlement is obtained by using the Crump numerical Laplace inversion method.The effects of different parameters on the water pressure and settlement of one dimensional consolidated voids in saturated soft clay were analyzed.The results show that the larger the interface parameters,the smaller the fractional order,the smaller the viscosity coefficient and the larger the instantaneous load,the faster the pore pressure dissipates in the soil at the initial stage of consolidation.Similarly,the semi-analytical solution of the consolidated pore pressure of the soft clay under three common loads is derived.Finally,the influence of different parameters on the water pressure and settlement of the one-dimensional consolidated pore of the saturated soft clay under cyclic loads is analyzed.The results show that the smaller the fractional order,the smaller the viscosity coefficient,and the larger the elastic modulus are,the faster the settlement curve tends to be flat,and the overall settlement velocity of the half-sinusoidal cyclic load is better than that of the sinusoidal cyclic load in the settlement consolidation.Cyclic load is not conducive to soil consolidation.All the results show that the viscoelastic behavior of saturated soft clay is well represented by the modified fractional order Abel viscoelastic model.