Study of the stress state of the sleeper base and sleepers of rail track with accounting variable conditions of their resting

Abstract

The live problem of the stress state of the sleeper base and rail sleepers is considered in the article with taking into account specific normal and specific shear stresses under variable conditions of the sleepers resting on the base. The methodology is aimed at the determination of the mutual influence of normal (compressive) and tangential (shear) specific stresses on formation of stability due to the displacement of individual parts of the base. Stability zones and shear zones of the sleeper base parts are also determined by the authors at different conditions of the sleeper resting on the base. Further, zones with insecure position of the base under the sleepers are found when they and their under-rail parts continuously rest on the base. It is stated that insecure position of the base is formed when specific shear stresses excess specific stresses of shear resistance, which consists of specific friction and specific cohesion between the parts in the base. It is also established that loss of stability of the ballast particles causes their displacement in the direction of the action of specific shear stresses. In these zones, density and rigidity of the sleeper base decreases leading to a gradual redistribution of reactive resistance of the base along the sleeper, and, depending on this redistribution, a change in the bending moments acting on the sleeper occurs. It is found that when the sleepers rest only by their under-rail parts, shear stresses and forces, as well as stresses and shear resistance forces under the middle part of the sleepers are distributed in such a way that shear forces exceed resistance forces up to the depth of 60 cm from the sleepers sole. This phenomenon leads to the displacement of ballast particles under the middle part of the sleeper, consolidation of the ballast and resting of the sleepers by their middle part with possible cracks formation. In the end sections of the sleepers, there is also a loss of ballast stability. Recommendations for improving stability indicators of the sleeper base and strength of the sleepers are given. The obtained results of the study can be used for the mine, industrial and railway transport.