非饱和土增湿变形的实用计算方法

Practical Computation Method of Deformation with Water Content Increasing of Unsaturated Soil

非饱和土力学研究目前还未进入实用阶段,主要原因在于吸力量测困难。本文提出了用等效吸力代替真实吸力的试验方法。首先以常规静三轴试验得到的原状饱和土以及非饱和土的应力-应变曲线为基础,根据变形等效的原则确定与某一饱和度相当的围压即为等效吸力;然后建立饱和度与等效吸力之间的非线性关系,并验证了该数学公式的正确性;再根据试验结果分析含水量对非饱和土强度的影响,建立了非饱和土的实用抗剪强度公式;最后按照邓肯-张模型的参数整理方法得到了不同饱和度非饱和土的模型参数,探索这些参数随饱和度的变化规律,建立了引入饱和度的非饱和黄土实用非线性模型,并进行了降雨入渗情况下非饱和土增湿变形的计算。结果表明,饱和度最大值为95%,等效吸力最大值为160k Pa,最大水平位移与竖向位移分别为0.6 cm和20.0 cm,均出现在浸水位置。计算结果合理地反映了非饱和土变形的分布趋势,验证了方法的合理性。

The research of unsaturated soil mechanics cannot yet reach in practical application because of the difficulty in measuring suction. A new test method to measure suction is suggested in this paper, in which the actual suction is replaced by equivalent suction. The cell pressure in a certain degree of saturation is taken as the equivalent suction according to the principle of deformation equivalence and the stress-strain curves obtained by triaxial compression tests of saturated and unsaturated undisturbed soil. A nonlinear relationship formula between equivalent suction and degree of saturation is presented.Then, considering the influences of water contents on strength, a non-linear shear strength model and stress-strain model of unsaturated loess are developed. And the parameters of Dancun-Chang＇s model are obtained for unsaturated soils with different saturation degree. The deformation from presented model under the case of rain-seepage into unsaturated soil show that the maximum of suction and displacement occurs in place in flooding, in which the maximum degree of saturation is 95%, the maximum equivalent suction is 160 kPa, the maximum horizontal displacement and vertical displacement are 0.6 cm and 20.0 cm, respectively. The calculation results rationally reflect the distribution trend of unsaturated soil deformation.