Study of soft soil triaxial shear creep test and model analysis

Digital image measuring principle and the way to eliminate or reduce error in the triaxial test are introduced; and digital image processing technique is used in triaxial shear creep test. The test results show that thickness of the water film between soil particles has big effect in creep. In undrained condition, Sample soil particles of water film unchanged and viscosity coefficient is constant too, so soil creep deformation has a greatly change. While in drained condition, water is discharged from the soils, soil is concretion and induration and soil particles of water film is thinning and soil density increases and viscosity enhances; creep deformation is smaller. And transient pore water pressure will continue to rise for Manadei-Cryer effect; the whole process is taken about 10 min. With the deviatoric stress level increasing, soil sample is bulging, then shear plane appears and it is usually located in the lower part of the sample. Comparison the results of digital image measure method and displacement conversion method gotten shear strain showed that: samples of the non-uniform deformation can lead to larger error in displacement conversion method for calculating the shear strain. Singh - Mitchell model describes the soil shear creep properties exactly. And parameter gotten by the two methods is not a big difference. When deviatoric stress level is low, the parameters can be gotten from displacement conversion method.