Impact of repeated loads on saline soils of earth roadbed

Abstract

The constant development of the road network in Uzbekistan, especially in widespread saline soils, necessitates increased attention to road structure strength. Since vehicles differ in weight and speed, it is obvious that the saline soil under the pavement is subjected to successive impacts of a load of different power and application force. Experimental studies to identify the patterns of changes in saline soils' physical and mechanical properties under repeated and short-term loads were conducted on a device specially designed by the authors of this study. The experiments were conducted on samples of sulfate and chloride-sulfate medium-saline heavy silty sandy loam, compacted at optimal moisture content to maximum density. When conducting the experiment, the impact duration of vertical load Рver = 0.15 MPa on the sample was tload = 0.2 sec, and the interval between the loads was 0.5 sec, the frequency of application was f = 1.2 Hz. The number of short-term load applications was recorded using an electric meter installed on the device. After a certain number of short-term cyclic load applications on the sample, its physical and mechanical properties were determined following the requirements of state standards (GOST). The results of the study show that with an increase in the number of cyclic and short-term load impacts on the sample, the following values increase: residual strain, density, and modulus of setting, relative swelling, swelling pressure, ultrasonic transmission rate, coefficient of filtration; while the porosity, coefficient of porosity, soaking, ultimate strength in uniaxial compression, the coefficient of dynamic viscosity, adherence, the angle of internal friction and the modulus of elasticity of soil decrease. It was determined that under the repeated impact of short-term loads in compacted saline soil, residual strains and short-term redistribution of stresses in the contact of soil and salt particles occur, which leads to a change in the physical and mechanical properties of soil.