Improvement of Calculation Method of Road Pavement Embankment on the Approaches to Road Bridges

Abstract

The laws of unsaturated and capillary movement of water in soils are analyzed, which are complex and insufficiently studied, but significantly affect the condition of the ground. Experience in the design and construction of the subsoil has shown that during the excavation works can significantly change the conditions of soils and their water-thermal regime. Therefore, the characteristics of soils used in stability calculations should be determined taking into account the subsequent condition of the soil in the conditions of occurrence, as well as the possible change of these conditions during construction and maintenance. One of the urgent tasks is to improve the methods of regulating the water-thermal regime of roads. By changing the conditions of its course or the type of water-thermal regime itself, significant successes can be achieved in improving the maintenance of roads, engineering and transport facilities. Dangerous effect of these factors on the embankment of the ground is manifested in the formation of wetting, wetting of the soil and layers of pavement, resulting in reduced density, strength of soils, subsidence, swelling and loss of continuity due to cracking. As a result, the strength of the road structure, the flatness of the carriageway, the durability of the pavement and the adhesion of the wheels to the roadway are reduced. The most dangerous for roads are moisture accumulation, freezing, thawing of the ground, intensive heating and intensive cooling of the layers of pavement. The analysis of regularities of formation of a water-thermal regime of a ground and its regulation at the expense of the device of optimum capillary-interrupting layers is carried out. The laws of soil moisture when raising capillary water showed that when the layer of the embankment with a high coefficient of impregnation is dehydrated over the layer with a lower coefficient, the speed of moving capillary water into the upper soil layers drops sharply. This fall occurs as a result of changes in the relationship between the driving forces of the menisci and the forces of resistance of capillary water in the soil. The process of unsaturated movement of water in the soil is determined by the combination of many factors that characterize the capillary system of the soil. The calculation uses complex indicators of soil water movement conditions, which are established experimentally for each variety and soil density at optimal humidity, as well as water filtration coefficients in the soil. To establish the relationship between these experimental data and the required values that determine the capillary system of the soil, the filtration of water in the soil was considered. Determining the optimal capillary system of the soil and establishing the unstable distribution of own capillary water in the structures of high embankments will ensure the strength of approaches to road bridges. The method of calculating the determination of the optimal composition of the road layers taking into account the processes of water-thermal regime and capillary movement of water has been improved. The algorithm of calculation in the program Microsoft Excel for selection of optimum structure of a ground cloth of a high embankment on approaches to automobile bridges is offered.