Study of the characteristics of ballast bed resistance for different temperature and humidity conditions.

• The resistance characteristics of ballast bed in different temperature and humidity were explored. • The characteristics of ballast bed resistance in freezing environment were explored. • The variation rule of ballast bed resistance during melting process of ice and snow was explored. A ballasted track structure is one of the most representative types of railway construction. Due to the influences of low-temperature rain and snow environments in alpine regions, an in-depth study of the resistance characteristics and evolution patterns of ballasted track beds is urgently needed. A full-scale ballasted track model was constructed in an insulated test chamber with a programmable temperature-controlled environment. The longitudinal and lateral resistances of the ballast bed were tested for different temperature and humidity conditions, and the performance evolution patterns were analyzed. After the failure of the internal ice layers, a resistance test was carried out for the ballast bed in a low-temperature freezing environment, and the influence of the ice destruction on the characteristics of the ballast bed resistance was analyzed. By simulating the low temperature rise environment, the variation patterns of the ballast bed resistance during the freeze–thaw process were tested and analyzed. The results showed the following. The ballast bed resistance in a dry and low-temperature environment was different from that at normal temperature, and the variation with temperature was greater than that at a normal temperature. The resistance of the ballast bed in a wet state decreased compared to that in a dry condition; as the humidity increased from 34% (dry) to 91% (wet), the longitudinal resistance decreased by 22% and the lateral resistance decreased by 17%. The freezing environment could increase the ballast bed resistance when the sleepers had small displacements. However, after the displacement exceeded a certain value (3.8 mm longitudinally and 2.9 mm laterally under the test conditions), the ballast bed resistance was reduced, with the average reduction rates of the longitudinal and lateral resistances reaching 4.55 kN/mm and 2.90 kN/mm, respectively. The rapid rise and fall of the ambient temperature had an enormous influence on the ballast bed resistance. When an ice-water mixture appeared inside the ballast bed at about 0 °C, the longitudinal and lateral resistances were reduced to 31.64% and 30.28%, respectively, of the resistances in a normal situation. The state dependence of the ballast bed resistance on the low-temperature rain and snow environment indicated that more attention is necessary for the complex service characteristics of the ballasted track under similar conditions. [ABSTRACT FROM AUTHOR]