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非饱和土的真三轴强度准则及三向应力状态预测是实现非饱和土理论工程应用的重要问题,依据非饱和土的双应力状态变量及吸附强度特性,构建适用于非饱和土的双剪单元体模型,继而建立分段线性的非饱和土统一强度理论,分析其特例、平面极限线和空间极限面的特性,并用已有的非饱和粉砂的刚性与柔性真三轴试验结果进行验证。研究结果表明:本文非饱和土统一强度理论的极限线覆盖了所有外凸区域,饱和土的统一强度理论以及非饱和土的Mohr-Coulomb强度准则均为其特例,而且还包括很多新的强度准则;非饱和粉砂的所有真三轴试验数据均落在非饱和土统一强度理论的极限线范围内,并与统一强度理论参数b=1/2时的预测值吻合较好;外接圆Drucker-Prager准则不能反映非饱和土的真实强度特性,b=1/2时非饱和土统一强度理论可线性逼近拓展的非线性SMP准则。
The true triaxial strength criterion and three-dimensional stress state prediction of unsaturated soils are important issues in the application of unsaturated soil theory engineering. Based on the dual-stress state variables and the adsorption strength characteristics of unsaturated soils, Then, the unified strength theory of piecewise linear unsaturated soils is established, the characteristics of its special case, plane limit line and space limit surface are analyzed and verified by the rigid and flexible true triaxial test results of the existing unsaturated silt . The results show that the limit line of the unified strength theory for unsaturated soils covers all the convex regions. The unified strength theory of saturated soils and the Mohr-Coulomb strength criterion for unsaturated soils are all special cases, and many new strength criteria ; All true triaxial test data of unsaturated silt falls within the limit line of the unified strength theory of unsaturated soils and is in good agreement with the predicted value of unified strength theory parameter b = 1/2. The circumcircle Drucker- Prager criterion can not reflect the true strength characteristics of unsaturated soils, b = 1/2 when the unified strength theory of unsaturated soils can approximate the extended nonlinear SMP criterion linearly.