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为研究冻融循环对青藏粉砂土屈服及强度特性的影响,进行环境冷却温度-5℃、室温下融化,不同冻融循环次数及围压下的饱和粉砂土的固结排水三轴剪切试验。结果表明:粉砂土在整个剪切过程中呈现出剪缩的特性,且其应力–应变关系为应变硬化型,冻融循环未改变粉砂土的应力–应变及体变型式。未冻融粉砂土的体积屈服面和剪切屈服面可分别用椭圆型曲线和过原点的线性函数进行描述。冻融循环未改变粉砂土屈服面的形状,且冻融粉砂的体积屈服函数及剪切函数与塑性应变和冻融循环次数的关系可用相应的幂函数形式进行表示。其抗剪强度随着法向应力的增大而增大,随着冻融循环次数呈现出先降低后升高的趋势。冻融循环后,粉砂的黏聚力由4.82 k Pa降至2.07 k Pa,而内摩擦角则由27.11°最低降至22.93°。根据不同冻融循环次数下粉砂强度随法向应力的变化规律,指出可用线性莫尔–库仑准则来描述其强度特性。
In order to study the effect of freeze-thaw cycles on the yield and strength characteristics of Qinghai silt sand, three-axis shear of saturated silt soil under the ambient cooling temperature -5 ℃, thawing at room temperature, different freeze-thaw cycles and confining pressure Cut the test. The results show that silt sand exhibits shear-shrinkage during the whole shearing process, and its stress-strain relationship is strain-hardening type. The stress-strain and volume change of silt soil are not changed by freeze-thaw cycles. The volume yield surface and shear yield surface of unfrozen silt can be described by a linear function of the oval curve and the origin, respectively. The freeze-thaw cycle does not change the shape of the yield surface of silty sand, and the relationship between the volumetric yield function of shear strength and the plastic strain and the number of freeze-thaw cycles can be expressed by the corresponding power function. The shear strength increases with the increase of normal stress. With the number of freeze-thaw cycles, the shear strength decreases first and then increases. After freeze-thaw cycle, the cohesion of silt decreased from 4.82 kPa to 2.07 kPa, while the internal friction angle decreased from 27.11 ° to 22.93 °. According to the regularity of the strength of silt with normal stress under different freeze-thaw cycles, it is pointed out that the linear Moore-Coulomb criterion can be used to describe the strength characteristics.