颗粒级配及含盐量对西宁地黄土状盐渍土抗剪强度特征影响试验研究

Experiment Study on the Effect of Soil Particle Size Distribution and Salt Content on the Shear Strength of Xining Salinized Soil

摘要: 通过对西宁盆地广泛分布的黄土状盐渍土进行筛分试验，获得5组不同粒径(<0.1 mm, 0.1~0.25 mm, 0.25~0.5 mm, 0.5~1.0 mm和1.0~2.0 mm)的土体，在土体中加入不同质量硫酸钠(Na2SO4)以配制成不同粒径、不同含盐量(0.0%、0.5%、1.0%、3.0%、6.0%、9.0%和12.0%)的盐渍土试样，通过室内直剪试验对上述试样进行剪切试验，试验结果表明：1) 含盐量和土体粒径对盐渍土抗剪强度指标和试样变形破坏产生显著影响，对于5种不同粒径盐渍土，其抗剪强度指标均随含盐量增加表现出先减小后增加变化特征，黏聚力和内摩擦角最小值所对应含盐量均为1%~3%；2) 对于粘聚力，当含盐量小于等于6%时，粘聚力随粒径增加表现出降低的变化特征，当含盐量为9%和12%时，粘聚力则表现出增加的变化特征；3) 对于内摩擦角，当含盐量为0.0%~3.0%时，土体黏聚力随粒径增大表现出增加的变化趋势，当含盐量为6.0%、9.0%和12.0%时，其内摩擦角则随粒径增加表现出先增加后减小的变化特征；4) 随含盐量逐渐增加，盐渍土剪应力–应变关系表现出盐渍土由弹塑性逐渐过渡至脆性的材料特性；5) 对于粒径较小(<0.5 mm)的盐渍土，随着含盐量逐渐增加，盐渍土的变形和破坏特征表现为由弹塑性变形破坏过渡至脆性变形破坏的变化规律，对于粒径较大盐渍土(>0.5 m)，其破坏特征主要以脆性破坏为主。该研究结果对于揭示青藏高原东北部盐渍土地区边坡水土流失、边坡失稳机理具有重要的理论研究价值，同时也对该区及地质特征与气候特征与该区相似的区域水土流失、滑坡等地质灾害的科学防治和边坡治理具有实际指导意义。

Abstract: Based on sieve tests, 5 sets of soil with different particles size (<0.1 mm, 0.1 - 0.25 mm, 0.25 - 0.5 mm, 0.5 - 1.0 mm and 1.0 - 2.0 mm) were obtained. Built on that, Na2SO4 powder in different mass was added into sieved soil to make salinized soils in different salt contents with different particle sizes. After these, indoor direct shear tests were conducted to these salinized soils. The results exhibit that: 1) both salt content and soil particle size distribution exert significant effects on the shear strength properties and failure behaviors of salinized soil. For the five sets of salinized soils in different particle sizes, their shear strength indices exhibit an initial decreasing and then increasing trend with salt content and the salt content corresponding to minimum values in shear strength is 1% and 3%. Additionally, cohesion is sensitive to the variation of salt content and internal frictional angle is insensitive; 2) for cohesion, as salt content ranges from 0.0% to 6.0%, it experienced a linear decreasing trend with soil particle size increasing, whereas as salt content distribute from 9.0% to 12.0%, it exhibits an increasing trend with soil particle size increasing; 3) for internal friction angle, as salt content less than 6.0%, it exhibits an increasing trend and beyond this value, it exhibits an initial increasing and then declining trend with particle size increasing; 4) with salt content increasing, shear stress-strain curve experienced a transition from elastic-plastic to brittle property; 5) as to salinized soil with soil particles size less than 0.5 mm, with salt content increasing, its deformation and failure property are characterized with a transition from elastic-plastic to brittle property, and as to soil with particle size larger than 0.5 mm, its deformation and failure properties are dominated with brittle feature. The researching results have a significant role in salinized arable land reclamation in regions jeopardized with soil salinization and soil erosion, also can be used to shed light on the mechanism of soil erosion and slope failure in salinized regions and play a practical role in soil erosion prevention.