超固结土三轴率敏性特性及影响因素分析

Investigation of triaxial rate-dependent characteristic and its influencing factors of remoulded over-consolidated clay

为建立超固结土的弹黏塑性本构模型并预测其长期变形,研究土体不同应力历史的时间相依变形特性,采用土体率敏性三轴试验,对预加800k Pa有效应力历史的饱和黏土开展不同加载速率下的三轴剪切试验,并通过改变有效围压(50,100,200和400kPa)、细砂含量(占比0%,10%和20%)和加载速率(0.5625%/min,0.037 5%/min和0.002 5%/min)等方式,深入探讨超固结比、黏性以及应变速率对土体变形特征的影响,引入能通过试验测定的应变率参数ρ来表征黏土率敏性大小。试验结果表明:归一化不排水抗剪强度随超固结比(OCR)单调递增;随着OCR的增大,土体剪胀软化越明显;应变速率与土体的抗剪强度呈半对数线性关系;随着含砂的降低,土体的黏性增大,剪胀软化也越明显;率敏性随超固结比的增大而增强,土体黏性越大率敏性就越显著。

In order to establish an elasto-viscoplasticity constitutive model and predict its long-term deformation of over-consolidated clay,their time-dependent deformation characteristics with different stress history needed to be investigated by the rate-dependent triaxial shear test,which is a very effective method to measure time-dependent deformation.The undrained triaxial shear compression tests were performed on saturated clay with an effective stress history of pre-stressing confining pressure of 800 kPa,and the influence of over-consolidated ratio,strain rate,and viscosity on mechanics characteristics of saturation remolded clay was investigated by changing confining pressure of 50,100,200,and 400 kPa,and sand content of 0%,10%,and 20%,and strain rate of 0.562 5%/min,0.0375%/min and 0.002 5%/min,respectively.The strain rate parameterρdetermined by the tests was chosen to indicate the strain rate sensitivity.The experimental result shows that:normalized undrained shear strength increases monotonously with over-consolidation ratio;dilatancy and softening property of clay becomes more obvious with the increase of over-consolidated ratio;strain rate shows a half logarithm linear relationship with shear strength of clay;when viscosity of clay increases with the decrease of sand content,dilatancy and softening property of clay also becomes more obvious;rate sensitivity of clay is enhanced with the increase of over consolidation ratio,and it also becomes more obvious with higher viscosity.