路基水盐迁移及其对路用性能的弱化影响研究

针对盐渍土地区的高速公路填料,采用自制冻融循环试验装置进行了冻融循环作用下砾类土路基水盐迁移试验,结果表明:距路基顶面20 cm以下的中上部土层为主要的“聚盐层”,此高度范围主要发生盐分迁移和“水去盐留”的蒸发聚盐过程。分析了细粒含量对砾类土路基冻融循环冻胀变形量和压实度衰减率的影响,细粒含量越高,路基冻融变形量越大,压实度衰减率越大。土样经过冻融循环后,其回弹模量和CBR显著降低,冻融循环引起的路基次生盐渍化导致其路用性能的弱化。从减少毛细水和盐分迁移、减缓路基压实度衰减和冻胀角度出发,季节性大温差极端环境下强盐渍土地区砾类土路基填料应将细粒含量控制在10%以下。

Study on Subgrade Water-salt Migration and Its Influence on Road Performance Weakening

The water-salt migration test of gravel soil subgrade under the action of freeze-thaw cycle was carried out by self-made freeze-thaw cycle test device based on the highway filler in saline soil area. The test results show that the upper and middle soil layers below 20 cm from the top of the subgrade are the mainsalt-accumulating layers. Salt migration and evaporation and salt-accumulating process of water desalination and salt retention occur mainly in this height range. The influence of fine particle content on frost heave deformation and compactness attenuation rate of gravel soil subgrade during freeze-thaw cycles is analyzed. The higher the fine particle content is, the larger the frost-thaw deformation of subgrade is and the greater the compactness attenuation rate is. After freeze-thaw cycles, the modulus of resilience and CBR of soil samples decrease significantly. Secondary salinization of subgrade caused by freeze-thaw cycles leads to the weakening of road performance. From the point of view of reducing capillary water and salt migration, reducing subgrade compaction attenuation and frost heave, the content of fine particles should be controlled below 10% in gravel soil subgrade filling in seasonally large temperature difference extreme environment in strong saline soil area.