软土三轴剪切蠕变试验研究及模型分析

将数字图像测量技术运用于三轴剪切蠕变试验，试验结果表明，土粒间水膜厚度对土的蠕变有很大的影响，不排水时，试样土颗粒间水膜保持不变，土的黏滞系数基本为一定值，土的流变变形较大；排水时，随着水的排出土体发生固结硬化，土颗粒间水膜变薄，土的密度增大，黏滞性增强，流变变形较小。在排水条件下，加载瞬间孔隙水压力会持续上升产生Manadei-Cryer效应，整个过程历时约10 min。随着偏应力水平的增加，试样发生鼓胀变形，进而形成剪切面发生剪切破坏；受排水路径的影响，剪切面通常位于试样偏下部位。对比数字图像测量方法和试样排水体积换算法在获得剪切应变时的试验结果，表明试验过程中试样变形的不均匀会导致排水体积换算法在计算剪切应变时产生较大误差；Singh-Mitchell模型很好地描述土的剪切流变特性，确定参数时两种方法得到的参数相差不大，偏应力水平较低时可采用排水量换算法进行确定。

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.