第四纪浅表堆沉积土石混合体广泛分布于地表,从结构特征研究其力学特性是解决日益复杂的岩土工程问题的有效途径之一。目前,土石混合体结构的量化主要从密度、含石量、孔隙比等宏观指标间接描述,而微细观的结构指标存在尺度间关联的技术瓶颈。为了更好地研究土石体堆沉积结构对土石混合体力学行为的影响,针对堆沉积演化的成层状特征,采用标准差量化其块石分布形式,借鉴综合结构势理论,将均匀与不均匀土石混合体三轴剪切试验偏应力的比值定义为结构参量m_s,分析该参量随轴向应变ε₁、不均匀度s及围压σ_3c的变化规律,得到其量化表达式,并引入双屈服面弹塑性本构模型进行修正应用。结果表明:m_s的变化规律能够较好地体现成层状结构特征对土石混合体力学行为的影响,且土石混合体综合结构势在应变为5%时接近完全释放,特征值m_s(5%)几乎能完全反映结构对力学特性的宏观影响;同时,引入m_s后的修正本构模型在偏应力精度方面减小了约28%的平均误差,能够更合理地反映成层状土石混合体的宏观力学特性。

Shallow quaternary deposited and sedimentary soil-rock mixtures (SRMs) are widely distributed on the earth. One of the most effective approaches to solve the increasingly complex geotechnical problems is to study the mechanical properties of SRMs from their structural characteristics. At present, the quantification of the structure of SRMs is mainly and indirectly described by macroscopic indicators, such as density, stone content, and void ratio; while the multiscale correlation between microscopic and mesoscopic structural indexes is still a technical bottleneck. To better understand the influence of the structure on the mechanical behavior of SRMs, the layered distribution form of rock blocks created in the deposited and sedimentary evolution was quantified via the standard variance based on the idea of comprehensive structural potential. The structural parameter (m_s) was defined as the ratio of the deviator stress of uniform SRMs to that of non-uniform SRMs. The variations of m_s with the axial strain (ε₁), the non-uniformity (s) and the confining pressure (σ_3c) were examined, and the quantitative expression of m_s was obtained and incorporated into an elastic-plastic constitutive model with double yield surfaces. The results show that the variation of m_s well reflects the influence of the layered structural characteristics on the mechanical behavior of SRMs. The comprehensive structural potential of SRMs is released almost completely as the axial strain reaches 5%, and the feature value (i.e., m_s (5%)) reflects the macroscopic influence of structural characteristics on the mechanical behavior of SRMs. Meanwhile, the modified constitutive model with m_s improves the accuracy of the deviator stress by about 28%. It proves that the modified constitutive model can reasonably reflect the macroscopic mechanical properties of layered SRMs.