非饱和土的峰值强度特性及破坏包线模型
Peak strength characteristics and failure envelope model of unsaturated soils
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摘要: 针对非饱和压实土,在不同含水率下,通过三轴压缩试验及抗拉强度试验,研究了非饱和土的峰值破坏点及破坏包线。基于试验结果,讨论了非饱和土破坏包线模型的构成方法。首先,按照土体的破坏模式,破坏包线可表征为两段Mohr–Coulomb型直线。其次,非饱和状态对峰值强度的影响主要表现为剪胀作用和颗粒间作用力两方面,按照非饱和时峰值强度的主要组成部分及其表示方法,给出了黏聚力–剪胀作用型和颗粒间作用力–剪胀作用型两种物理意义明确的曲线型破坏包线。基于分段线性破坏包线,讨论了曲线型破坏包线参数的确定方法。最后,给出并分析了非饱和时不同含水率下土体的破坏包线及其变化特性。Abstract: The peak strengths and failure envelopes of unsaturated compacted soils are investigated via triaxial compression and uniaxial tensile tests over a wide range of water content. Based on the experimental evidence, a method for deriving failure envelope model for unsaturated soils is discussed. Firstly, according to the mode of failure, the failure envelope can be approximated by a bilinear Mohr–Coulomb envelope. Secondly, the effect of unsaturated state on the peak strength can be described in terms of dilatancy and interparticle stress. Then accounting for the primary components of unsaturated peak strength and its description, two curved failure envelopes with clear physical meaning are proposed, named after cohesion-dilatancy and interparticle stress-dilatancy envelope respectively. Based on the piecewise linear failure envelope, the method for determining the parameters of the curved failure envelope is discussed. Finally, the failure envelopes and their variation characteristics under different water contents in unsaturated state are given and analyzed.