Research on the mechanism of railway ballast shear performance under various sand contents and load conditions

Railway operation in desert areas faces unique challenges due to wind-blown sand penetration on the safety of the line. In-depth research on the impact of wind-blown sand penetration on the shear performance of the railway ballast is crucial for understanding potential problems in sandy railways and formulating effective maintenance strategies. This paper conducts a series of direct shear tests under various sand contents and load conditions using an independently developed automatic control loading direct shear test apparatus suitable for railway ballast. By accurately considering the interaction between sand and ballast particles, some direct shear numerical models of different sand-containing ballast boxes based on refined particle simulation are established based on the discrete element method (DEM) and particle scaling method, exploring the variation in shear strength, shear deformation, contact relationships, and rotational characteristics of railway sand-containing ballast from macroscopic and microscopic perspectives. The results show that with the increase in shear strain, the shear stress of the ballast with various sand contents increases first and then tends to stabilize, and the phenomenon of dilation occurs in all cases. When the normal load is constant, the shear strength and cohesion of the ballast show a trend of first decreasing and then increasing with the increase in sand content. The wind-blown sand penetration inhibits the rotational deformation during shearing, enhancing particle aggregation. With the increase in sand content, the contact coordination number, powerful force chain number, and total force chain number all increase continuously. However, the average contact force shows a trend of gradually decreasing and then increasing. This study provides theoretical support and experimental backing for the operation and maintenance of the ballast bed in sandy railways.