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The results of field researches of the oscillatory process subgrade erected with sand dunes. The analysis of the oscillations records of particle of sand dunes at the main field, in the frame and be-hind of the subgrade. Given findings change of the value of oscillation amplitudes of dunes sand depending on the speed of trains. Analytical dependence of definition of attenuation of fluctuations in a body of subgrade from sand dunes and behind its limits is revealed.

The main engineering problem associated with the degradation of permafrost and cyclic freezing-thawing of seasonal permafrost soils is a decrease in the bearing capacity of engineering structures due to the degradation of the main physical-mechanical properties of the embankment soils. The cyclical change in temperature leads to regular freezing-thawing of the soil, as a result of which such types of deformations occur as heaving during freezing and settlement during thawing. The purpose of this work is to highlight new information about complex measures to stabilize the subgrade of railways and highways in the cold regions of China. The paper considers such measures as thermosiphon stabilization, rock fill, installation of ventilation pipes and laying of thermal insulation boards. This paper also describes the disadvantages of existing measures for stabilizing the temperature regime of the embankment and its base. Considered the main transport network of the Qinghai-Tibet plateau, including the Qinghai-Tibet railway and four highways. The experimental section of the Wushu-Xining expressway on the Qinghai-Tibet plateau was chosen as the object of the study of numerical modeling; a numerical calculation of the temperature and moisture content fields of the typical embankment was carried out, as well as numerical calculation of the embankment with rock fill for the 10th year of operation. The calculations were carried out on the basis of the «Freeze-Cold» software package specially developed for engineering calculations of the freezing and thawing process in soils. The calculation showed that rock fill allows to reduce the area of the soil thawing, raising the front of frozen soil, helps to reduce the degradation of frozen soil, which ultimately has a positive effect on the bearing capacity of the entire engineering structure. Analysis of the collected data and calculated values allows to conclude that the use of rock fill of 0,8 meters depth as an insulating material to maintain the stability of the thermal regime of the embankment on frozen ground in the considered region of the Qinghai-Tibet Plateau.

This article presents promising and widely used in transport construction methods of earth bed reinforcement with the use of geotextile as a reinforcing and separating layer. It was suggested to lay down geotextile coverings manually in the zones of rail joints of an equalizing span of a continuous-flow track by 6-10 sleepers in each side of the joint, in all, 12-20 sleepers where high-speed and high-speed passenger traffic is expected. Basic technical requirements and restrictions on geometric dimensions for geotextile when reinforcing the main track bed are given. The technology of manual laying of reinforcing geotextiles when a small section of the railway track needs reinforcement during routine maintenance and repair of the railway track is given. The sequence of basic manual laying of geotextile coverings in the technological "windows" is described. Experimentally conducted work on the device coatings of geotextile manually in the areas of rail joints equalizing span of permanent way for 6 sleepers on each side of the junction in the railway sections of the Tashkent railway station (PCH-2). A design for reinforcement of the main ground in the areas of rail joints has been proposed. The basic requirements to quality control of construction works in structures with the use of a layer of geotextile materials are given.

The work is devoted to experimental study of the roadbed, filled from loess-like sandy, namely, characteristics dynamic vibration impacts arising from the passage of rolling stock, to establish the nature of the damped oscillation, the analytical expressions that can be used to estimate the bearing capacity of the subgrade to the dynamic vibration load.

The reinforcement of a soil subgrade by solidifying grouts injection, outside the limiting dimensions of train movement, can significantly increase the cost efficiency and manufacturability of strengthening. The paper suggests the most appropriate methods to strengthen the subgrade depending on the stage of defects and deformations development.