Experimental Study On Rate Effect And Deformation Aging Characteristics Of Soft Clay Mechanical Properties

When constructing structures on soft clay foundations,the method of calculating settlement has always received special attention from many scholars and engineers.China’s soft clay is widely distributed,mainly located in coastal areas along rivers,inland lake basins and plains.It has the unfavorable characteristics of high natural water content,high compressibility and low shear strength.The deformation characteristics of soft clay are closely related to time,including the consolidation of the drainage of ultra-quiet pore water to reduce the volume of the soil,and the creep of the rearrangement of the soil particles under the consolidation pressure.Determined the long-term settlement of the soil.Therefore,how to accurately grasp the time-dependent characteristics of soil deformation is a hot issue jointly discussed by engineering and academic circles.In this study,a large number of laboratory tests were carried out to conduct an in-depth comprehensive research and analysis of the time-dependent mechanical properties of soft clay.The main research contents and results are as follows:(1)A series of long-term oedometer tests of soft clays were carried out.The time-dependent characteristics and deformation mechanism of soft clay deformation were analyzed,and it provided a test basis for the establishment of an elastic-viscoplastic constitutive model..The test results show that the secondary consolidation coefficient of the soil decreases with the increase of loading time and preloading effect;the secondary consolidation coefficient is not affected by the drainage distance;and the secondary consolidation coefficient increases with the increase of the load,but The increase depends on the consolidation state of the soil.The turning point of the secondary consolidation coefficient with the load curve appears at a certain range related to p_c.(2)A series of oedometer tests of different soft clays and soft clays with different sand content and different drainage distances were carried out.The analysis of the?-lgt curves and stress-strain curves(E-O-P curve)of various soft clays verified the correctness of Hypothesis B.With the increase of the drainage distance,the completion time of the primary consolidation of the soil sample increases,and the strain value at the completion of the primary consolidation increases,but the secondary consolidation coefficient does not change much.The test shows that the drainage distance has a significant influence on the consolidation characteristics of soft clay.The secondary consolidation coefficient of the soil and the completion time of the primary consolidation jointly determine the growth rate of the strain value with the drainage distance when the primary consolidation is completed.(3)A series of undrained triaxial shear tests of various soft clays and soft clays with different sand content rates were carried out.The test results show that the stress-strain relationships of soft clays show a significant rate correlation.As the shear rate increases,the undrained shear strength of the clay also increases,and the correlation between the rates decreases as the confining pressure and sand content increase.Within a certain range of sand content,the undrained shear strength of soft soil decreases with increasing sand content,and when the sand content continues to increase to a certain critical value,the undrained shear strength increases with increasing sand content.