颗粒形状对强度和变形具有显著的影响,但影响规律尚不清楚。利用高强度的α-半水石膏粉制备类岩石颗粒,采用中压三轴仪固结排水试验,结合布拉斯谢克形状参数,研究形状系数对土石混合料的力学特性的影响规律,揭示颗粒形状对土石混合料力学特性的影响机制。结果表明,随着颗粒形状系数Y的增大,试样的峰值偏应力逐渐增大,后趋于平稳。随着试样中颗粒形状系数Y的增大,内摩擦角和初始抗剪角φ₀逐渐减小,黏聚力随之增大,抗剪角增量Δφ先减小后增大。形状系数通过改变骨架颗粒的应力传递路径,促使大粒径颗粒优先破碎。当Y从0.63增至0.73时,破坏模式由边缘破损向局部破裂、最终向完全碎裂转变。椭球状颗粒(Y≥0.69)因长轴端部应力集中,破碎集中于剪切带区域,形成局部断裂;而近球形颗粒因应力均匀分布,呈现表面剥落。揭示土石混合料形状对力学特性的影响机理,可为土石混合料路基沉降的预测与设计提供科学依据。

[Objective] This study systematically investigates the influence of particle shape on the mechanical properties of soil-rock mixtures, with a particular focus on strength and deformation characteristics. It aims to address the current knowledge gap regarding the specific mechanisms through which particle shape affects the mechanical behavior of such materials. By establishing quantitative relationships between shape parameters and mechanical response, the study aims to provide a scientific basis for predicting and controlling the settlement of soil-rock mixture subgrades in engineering practice. [Methods] High-strength α-hemihydrate gypsum powder was utilized to fabricate rock-like particles with controlled shapes. The Brazilian shape parameter (Y) was employed to quantitatively characterize particle morphology. A series of consolidated-drained triaxial tests were conducted using a medium-pressure triaxial apparatus to systematically evaluate the mechanical properties of soil-rock mixtures containing particles with different shape coefficients. The testing program included comprehensive measurements of peak deviatoric stress, internal friction angle, cohesion, and other shear strength parameters under different confining pressures. Microstructural analysis was performed to observe particle breakage patterns and stress transmission mechanisms. [Results] The experimental results revealed significant shape-dependent mechanical behavior. As the particle shape coefficient Y increased, the peak deviatoric stress of the specimens initially increased and then tended to stabilize. With increasing Y, the internal friction angle and initial shear angle φ₀ gradually decreased, while the cohesion exhibited a corresponding increase. The increment of shear angle Δφ showed a non-monotonic trend, first decreasing and then increasing. The shape coefficient was found to alter the stress transmission path within the particle skeleton, leading to preferential breakage of large-sized particles. When Y increased from 0.63 to 0.73, the failure mode transitioned from edge damage to localized rupture, and ultimately to complete fragmentation. Ellipsoidal particles (Y≥0.69) exhibited stress concentration at the long-axis ends, resulting in localized fracture concentrated in the shear band region. In contrast, near-spherical particles demonstrated uniform stress distribution and exhibited surface spalling. [Conclusion] This study successfully establishes the quantitative relationship between particle shape and mechanical properties of soil-rock mixtures, revealing the underlying mechanisms of shape effects. The findings demonstrate that particle shape significantly influences the strength, deformation, and failure characteristics through its control on stress transmission and particle breakage patterns. The study provides a scientific basis for the prediction and design of soil-rock mixture subgrade settlement, offering practical guidance for engineering applications. Future research should focus on extending these findings to field-scale conditions and developing predictive models that incorporate shape effects for improved design accuracy.