Mechanical properties and damage evolution features in uniaxial compression with non-coincident interlayer contact in double-block ballastless track

Abstract

As interlayer cracking has become as a significant issue in ballastless tracks, investigating the mechanical properties and damage characteristics during uniaxial compression with non-coincident contact is vital for enhancing the operational performance of ballastless tracks. This study conducted experiments on interlayer non-coincident contact damage in double-block ballastless tracks with nominal normal pressures of 0.666 MPa, 1.244 MPa, 2.489 MPa, and 3.733 MPa. The research explored the relationship between normal load and normal deformation stiffness, analyzed the interlayer contact damage mechanism of concrete, and investigated the damage evolution mechanism under non-coincident contact conditions based on Acoustic Emission (AE) signals. The findings indicate that: I) When the nominal pressure is respectively less than and greater than 1.333 MPa, the normal deformation stiffness and normal load satisfy linear and power function relationships, respectively. II) The interaction of interlayer protrusions under non-coincident contact, combined with the outward expansion resulting from interlayer mutual compression deformation, are two significant factors contributing to the formation of tensile cracks, while the presence of significant shear stresses directly beneath the interlayer contact points is the primary cause of shear cracks. III) After loading, The ballastless track slab matrix remains undamaged, while the supporting layer matrix may experience comprehensive cracking when the nominal pressure exceeds 1.333 MPa. IV) During the stage of only interlayer interface damage, both tensile and shear cracks are the primary causes of concrete damage. In the stage where damage occurs to both the interlayer interface and matrix, tensile cracks play a dominant role. However, when comprehensive matrix cracking occurs, shear cracks take on a dominant role. The outcomes of this study contribute to a deeper understanding of the damage mechanisms of ballastless tracks under train loads following interlayer cracking. Particularly focusing on the evolution characteristics of damage under high interlayer pressure.