Experimental Study On Water And Heat Distribution Characteristics Of Road Subgrade In Saline Soil Area Of Southern Xinjiang

Xinjiang is located in Tarim basin north of Karakoram mountain to the south of Tianshan Mountain.It is the key construction area of Xinjiang core area of "Silk Road Economic Belt" in China.As the central city of South Xinjiang,Xinjiang alar city has a very important regional position in its traffic infrastructure construction.With the continuous growth of road infrastructure construction mileage in Arar City,the special climate and engineering geological environment in the saline soil area of South Xinjiang make the temperature field,salt field,water field and stress field interact with each other in the road base of the urban road in southern Xinjiang,forming a complex multi field environment coupling environment interaction system.The multi field coupling environment is the road road coupling environment The main causes of subgrade damage and failure are studied.The damage and failure mechanism of water salt temperature multi field environmental action of road subgrade in saline soil area of South Xinjiang is studied,and the distribution characteristics of subgrade water,salt and heat are studied.It provides theoretical support and scientific basis for road engineering construction and disease prevention and control in saline soil area of South Xinjiang.The main research work of this paper is as follows:(1)The research on the road engineering diseases in the saline soil area of South Xinjiang is carried out.It is found that the damage of subgrade structure of urban road in Aral city of South Xinjiang is mainly caused by seasonal salt frost heaving and water salt dry and wet cycle.The main performance is the dry and wet cycle of chloride sulfate and the damage of cement-based materials in subgrade materials by the cyclic effect of salt freezing and thawing.The water salt medium in subgrade soil is migrated and accumulated to the bearing base and surface layer and structural materials under capillary action,and the seasonal freeze-thaw cycle causes the salt heaving frost heaving damage of subgrade structure,and continues to damage the subgrade structure The damage and damage of subgrade and pavement structure are caused by the water salt dry wet cycle,seasonal salt expansion freeze thaw cycle and road driving load.(2)The monitoring test of water and heat distribution characteristics of road subgrade in saline soil area of Southern Xinjiang was carried out.Based on the monitoring section set up in the road construction section of Tamen Road(the connection section of Huyang Avenue and Qiushou Avenue)in Alar City,the monitoring test research of moisture and temperature at different subgrade depths and the determination of salt at different depths were carried out.The monitoring test results show that the main reasons for the deformation and failure of the subgrade are the moisture migration caused by the temperature gradient in the subgrade structure layer and the change of its phase state and composition.Under the effect of seasonal high and low temperature freeze-thaw cycle,the road subgrade structure is damaged,resulting in pavement cracking,bulging,subsidence and other diseases.(3)The experimental study on the one-dimensional soil column water thermal characteristics of subgrade soil was carried out.The basic physical and chemical properties of salinized subgrade soil were tested and studied by indoor geotechnical test.The plastic limit index was 18 and liquid limit index was 0.8.According to the classification index of soil,the soil properties of subgrade soil were soft plastic and clay.The dry density is 1.69g/cm3,and the best moisture content is 18.25%.Through one-way freezing test of one-dimensional soil column in indoor,it is found that under the condition of freezing time and cold end temperature,the frost heaving is relatively small when the salt content is 10%;under the condition of freezing time and cold end temperature,the absolute value of the difference between water content and optimum water content is larger,the greater the frost heaving is.The deformation of frost heave is related to the temperature,salt content and water content of cold end.(4)The water and heat transfer of subgrade is simulated by using the multi physical field analysis software COMSOL multiphysics software,and the test of subgrade soil is verified.The results show that the simulated distribution of water separation field and temperature field are basically consistent with the distribution trend of water separation field and temperature field distribution monitored by the actual test,and the reliability of the model is verified.