寒区高吸力非饱和土的破坏准则研究

针对北方寒旱区路基边坡时常因拉剪强度不足而发生浅层滑坡的现象，通过常规三轴试验探究了冻融和高吸力对非饱和土的强度特性影响。结果表明：随着冻融次数的增加，非饱和土的土-水特征曲线逐渐下移，抗拉强度与抗剪强度逐渐减小；随着基质吸力的增加，抗剪强度逐渐增大，抗拉强度逐渐降低。鉴于传统的抗拉抗剪联合公式不能很好地反映经冻融作用之后高吸力非饱和土抗拉区破坏包线的实际情况，通过引入“界值”概念，提出一种新的抗拉区绘制破坏包线的方法对传统公式进行修正，修正后的公式具有很好的适用性，可以为寒旱区非饱和土边坡稳定性计算提供可靠的理论依据。

Study on failure criterion of unsaturated soil with high suction in cold regions

Aiming at the phenomenon that shallow landslides often occur in the slope of roadbed in cold and arid regions of northern China due to insufficient tensile and shear strength， high and low temperature alternating box is used to simulate the effects of different freeze and thaw actions in cold regions. Simulation and arid regions by the method of steam balance to control the soil is in a state of high suction， and the high suction soil water characteristic curve method of data with axis-translation get low suction test data combined with soil and water characteristic curve plotted by different broad suction under the action of freeze and thaw soil water characteristic curve， through conventional triaxial test and uniaxial tensile test to explore the strength characteristics of unsaturated soil freeze and thaw cycles and high suction. The results show that the water-holding capacity of soil decreases with the increase of freeze-thaw cycles. In terms of mechanics， the tensile strength and shear strength of unsaturated soil with high suction decrease gradually with the increase of the number of freeze-thaw cycles. With the increase of matric suction， the shear strength increases and the tensile strength decreases. The uniaxial tensile strength obtained from the shear strength data obtained from the conventional triaxial test is much larger than that obtained from the actual uniaxial tensile strength test for unsaturated soil with high suction. Because of the traditional formula of tensile shear joint not well reflect the high suction of unsaturated soil tensile area after unfreezing the actual situation of the failure envelope， by introducing the concept of “boundary value”， this paper proposes a new paint tensile area failure envelope method to modify the traditional formula， the revised formula has good applicability. It can provide a reliable theoretical basis for the calculation of unsaturated soil slope stability in cold and arid areas.