摘要
由于非饱和土性状主要受三个状态变量(σif—外加应力、u_w—孔隙水压力、u_w—孔隙气压力)及其历史的控制,因此,孔隙水、气压力的理沦和实验就成了研究非饱和土强度和变形特性的前提,也是验证土骨架应力应变模型的有效手段之一。本文基于吸力方程和笔者提出的广义非线性应力应变模型,根据质量守恒原理,导出了恒温不排气、不排水条件下求解孔隙压力系数的一般迭代算式。通过计算分析与试验验证表明:(1)本文的方法可以用于定量地揭示复杂应力条件下非饱和土孔隙压力的生成规律,并能实现由非饱和逐渐向饱和状态的平衡过渡,(2)非饱和土孔隙压力系数的影响因素很多,不仅与土骨架的压缩性、剪胀性、土体初始状态有关,而且还与外加压力及土体现时状态有关;(3)文中所给的四种广义非线性应力应变模型中,只有E-u-K模型能较好地模拟非饱和土孔隙压力的生成,而其它模型所预测的结果不是偏大就是偏小。
The theoretical and experimental studies on pore air and water pressure coefficients are the premiss of investigation on the strength and the deformation for unsaturated soils, and also an important means of verifying stress-strain constitutive models, as the mechanical behavior of unsaturated soils is mainly dependent upon the three following state varibles, pore air pressure u_a, pore water pressure u_w and external applied stress a_(ij), and their history. An isothermal, undrained set of iterative equations of pore pressure coefficients has been developed in this paper based on the mass conservation law, the generalized nonlinear stress-strain models proposed by the first author and the suction function of unsaturated soils. calculated analysis and experimental evaluation show that: (1) the formulae suggested in this paper can be used to predict the generation of pore air and water pressures in unsaturated soils undergone complex external applied loading, and can be transposed from unsaturated state into saturated state smoothly, and (2) the pore air and water pressure coefficients are not only related to the compressibility, the dilatancy of the soil skeleton and the initial state variables of the soil, but also related to the external applied loading and the soil state variables at present, and (3) among all the generalized nonlinear stress strain models, model E~μ~K is the most available for simulating the generation of pore air and water pressures in unsaturated soils.
