Analysis on Causes of Gap under CRTSⅡ Slab Ballastless Track

In order to study the causes of the gap between the track slab and the mortar layer, the analytical solutions of track slab expansion under the constraint of mortar layer or under the constraints of mortar layer and tensioned rebars were derived. The critical expansion temperature of track slab TL when the gap under the track slab was generated was analyzed. The results show that With large stiffness of the track slab expansion, the deformation of track slab expansion can be hardly constrained by mortar layer. When the gap under the track slab is generated, TL is mainly related to the relative displacement between the track slab and the mortar layer when the constraint on the track slab caused by the mortar layer reaches the maximum. Although the frictional resistance coefficient kc between the track slab and the mortar layer obtained from China's field test is obviously larger than that of Germany. When the pushing plate force reaches maximum, the critical displacement from the pushing plate test in China is 0.01-0. 06 mm, which is far less than the 0.5-0.9 mm measured by the German pushing plate test. As a result, when the gap under the track slab is generated, TL from China is much less than that from Germany. When the connection of tensioned rebars is finished, TL from China increases about 0.1-0.5℃, while TL from Germany increases about 4.1-7.3℃. To reduce the probability of gap, requirements should be put forward for the adaptability of the mortar layer to the deformation of the track slab in the design process and reinforcement maintenance of CRTSⅡ slab ballastless track. © 2021, Department of Journal of the China Railway Society. All right reserved.