Research On Mechanics Behaviors And Subgrade Stability Of Chloride Saline Soils Under Hydrothermal Action In Cold Region

ABSTRACT:Saline soil is widely distributed in China and Xinjiang, Qinghai, Gansu, Ningxia, Shanxi and Inner Mongolia which lie in the northwest of china are rich in saline soil. At the same time, most of China is located in temperate zone, so seasonally frozen ground accounts for three quarters of the total area of China. When the distribution of saline soil and seasonally frozen ground coincide with each other, subgrade filler exposed to the natural environment, the role of the repeatedly natural cycle of warming and cooling, subgrade will appear the salt expansion, frost heave, subsidence, strength change saline soil diseases and new mechanical characteristics. The disease can seriously affect the safe operation of road vehicles. With the wide range of highway construction in the western region, the issues on subgrade stability, pavement comfort, as well as subgrade filler was affected by factors such as cooling and heating, requirements continue to increase.According to the characteristics of saline soil area road construction, combined with China’s first high-grade highway construction Chaerhan-Golmud line in saline soil area as an example. It selected northwest region, Qinghai Province Chaerhan widely distributed in salt lake containing salt silty clay, through the field along the route survey, outdoor and indoor experiment and other means. It studied field temperature and geotemperature time-history variation, temperature difference between day and night geotemperature variations, transfer curves of monthly average geothermal, the water and salt migration regularity in field; based on geotemperature, the most dramatic temperature changes in the surface, the the weak saline soil subgrade engineering mechanical properties of the impact of experiment was done under different moisture and temperature changes, heating and cooling cycle amplitude and frequency; analysis suitable for the treatment method of weak saline soil. The main research results include the following aspects:(1) Summed Chaerhan-Golmud line saline soil along the distribution of the salt content, salt content type, major ion content, pH, etc., which provide the basis for the subgrade filler selection and indoor test soil samples selection.(2) The main meteorological parameters measured through field tests, determined the field temperature and geotemperature time-history variation, the upper and lower limits of the low temperature, etc., summarized the water and salt migration regularity in field.(3) Four different ways the foundation treatment methods through on-site test, analyze and evaluate its reinforcement effect. Focus summarized the gravel pile and dynamic replacement methods to reinforce the saline soil foundation on the working mechanism and reinforcement indicators. Analysis suitable for the treatment method of weak saline soil.(4) Determined saline soil shear strength and deformation law through direct shear tests under different temperature and different salt content conditions; shear strength and deformation under different moisture; shear strength and deformation law under heating and cooling cycle.(5) Saline soil subgrade filler deformation test, determined the soil samples subgrade filler deformation in the cooling process under different load conditions; subgrade filler water and salt migration law under different load conditions, salt content and ion content distribution law, comparative analysis with field water and salt distribution law.