土石混合体是拥有复杂物理力学性质的极端不均匀松散岩土介质系统,由于尺寸效应而表现出不同的强度和变形特性。以四川省康定市折多山某土石混合体边坡土样为研究对象,分析其基本物理性质并配置重塑土,设计了3种尺寸试样并进行静三轴试验,试样尺寸分别为直径100 mm×200 mm(D100H200)、直径150 mm×300 mm(D150H300)、直径300 mm×600 mm(D300H600)。结果表明:应变小于1.5%时,试样偏应力不受尺寸影响,均随试样变形增大而线性增大,当变形超过1.5%后,D100H200试样的应力应变关系曲线属于应变硬化型,D150H300和D300H600试样则属于应变软化型;不同尺寸的土石混合体均随着围压从100 kPa增大到300 kPa时趋于硬化,试样的峰值强度与围压线性相关并随着试样尺寸增大先增大后稳定,建立了峰值强度预测模型;试样的初始弹性模量随试样尺寸增大不断降低,D150H300和D300H600试样测得的黏聚力分别是D100H200试样的38.28%和34.89%,内摩擦角也分别是其92.20%和85.37%,建立黏聚力折减系数模型发现黏聚力随着试样尺寸的增大而降低至临界值时稳定。
The soil-rock mixture (S-RM) is a highly heterogeneous, loose geotechnical medium with complex physical-mechanical behavior, whose strength and deformation are strongly influenced by size effects. In this study, S-RM slope materials were sampled from the Zheduo Mountain area of Kangding City, Sichuan Province, China, and used for subsequent testing and analysis. These basic physical properties of the samples were analyzed, and remolded soil were prepared. Three specimen sizes were designed for the static triaxial tests, with diameter 100 mm×200 mm (D100H200), diameter 150 mm×300 mm (D150H300), diameter 300 mm×600 mm (D300H600), respectively. The results show that: The deviatoric stress of the specimens is not affected by their size and increases linearly with specimen deformation when the strain is less than 1.5%. However, the stress-strain relationship curves of the D100H200 specimens exhibit strain-hardening behavior, whereas the curves of the D150H300 and D300H600 specimens demonstrate strain-softening behavior when the strain exceeds 1.5%. S-RMs tend to harden with confining pressure increases from 100 kPa to 300 kPa of different sizes. The peak deviatoric stress is linearly related to the confining pressure and initially increases with specimen size before stabilizing. A predictive model for the peak principal stress difference has been established. The initial elastic modulus of the specimen decreases continuously as the specimen size increases. The cohesion values measured for D150H300 and D300H600 specimens are 38.28% and 34.89% of that for the D100H200 specimen, similarly, the internal friction angles are 92.20% and 85.37% of that for the D100H200 specimen. A cohesion reduction coefficient model was established, revealing that cohesion decreases with increasing specimen size and stabilizes upon reaching a critical value.
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