Currently, most ballastless tracks in Chinese subways are traditional cast-in-situ concrete structures, which require long construction progress. In contrast, prefabricated ballastless tracks can greatly reduce the construction period. However, there are few theoretical and experimental analyses on the prefabricated new type of subway slab track. Hence, to study the mechanical properties of the new type of subway track slab, static bending crack tests of one standard slab track and nine prefabricated full-scale track slabs with basalt fiber were carried out in this paper. The influence of the reinforcement arrangement method and the basalt fiber content on the performance of the track slabs was studied. Results showed that with the increase in the basalt fiber content in the range of 0.1–0.3%, the load–strain curve growth rate increased, the stiffness decreased, and the flexural resistance reduced. All the specimens exhibited a linear portion (elastic) and then a nonlinear portion (plastic) followed by flexural failure. During the elastic stage, the basalt fiber helped to improve the rigidity of the track slab. During the plastic stage, the influence of the basalt fiber content on the failure load varied with different reinforcement arrangements. With the reinforcement arrangement F2 and 0.1% basalt fiber content, the specimen had the smallest load–strain curve growth rate and the best overall flexural performance and crack resistance, and its strain was 23.35 με at an elastic limit of 95 kN. The results can provide a reference for the design of the prefabricated slab ballastless track.

The straightness of rail joints is one of the critical factors affecting passenger comfort in high-speed railways, and investigating its influence on the dynamic performance of the vehicle–track system and riding comfort is of great significance. In this study, long-term field measurements were conducted at a turnout joint of a newly constructed high-speed railway in China, combined with multibody dynamics simulations, to systematically analyze the long-term evolution of rail joint straightness under various conditions, including pre- and post-grinding, joint commissioning, official operation, and extreme weather. Based on normalized data processing, the root mean square (RMS) index of joint straightness was extracted for feature quantification. Together with vertical acceleration and the Sperling index obtained from vehicle–track coupled dynamics simulations, a quantitative relationship between straightness and comfort was established. The results indicate that the cubic polynomial fitting method can effectively characterize the nonlinear mapping between the RMS of joint straightness and the Sperling index, further revealing a critical threshold at approximately 0.4 mm RMS beyond which vehicle running stability deteriorates and ride comfort significantly worsens. This study provides a reliable theoretical basis and engineering reference for the evaluation of rail joint quality and the optimization of maintenance strategies.

Based on the similar characteristics of installation about the penetrometer of seismic piezocone penetration tests(SCPTu) and the single pile, a theoretical relationship between ultimate bearing capacity of single pile, time-effect of shaft bearing capacity of single pile, excess pore water pressure around the pile during pile driven and the data measured from SCPTu is developed according to the cavity expanded theory, the Terzaghi one-dimensional consolidation theory and effective stress theory. The result of field test in KunShan and the calculated result which used the theoretical relationship mentioned above are compared. The results indicate that the analytical solutions agree well with the in-situ tests, which show that the applications of seismic piezocone penetration tests have wide range in the design of pile foundation.