Full-scale model testing on the dynamic behaviour of weathered red mudstone subgrade under railway cyclic loading

Although weathered red mudstone (WRM) is widely distributed in the southwest of China, its suitability as a fill material for the subgrade bed of a high-speed railway (HSR) has not been comprehensively investigated. This paper presents the results of a field full-scale model testing of the cyclic loading and response of a railway track-subgrade system for the Dazhou-Chengdu Railway, where some WRM has been used in a newly designed subgrade structure. A control section of the HSR was also built using a traditional subgrade bed (Group A&B material) to compare the performances of the different sections. To better understand the dynamic characteristics and cumulative deformation of the two types of subgrade, the dynamic actions of different axle loads and different train speeds were simulated using specifically designed track-cyclic-loading equipment. The transverse and vertical distributions of the dynamic stress, dynamic displacement and acceleration of the track-subgrade system were measured and evaluated. The influence of the wheel axle load on the growth factor of the dynamic parameters, the vertical attenuation coefficient of the dynamic stress, and the effect of using WRM in the subgrade on the post-construction settlements were investigated. The tests enabled the development of cumulative settlement laws with railway loading for the two types of subgrade. Although the dynamic parameters and cumulative settlement of the WRM subgrade are always greater than those of better-quality material (Group A&B subgrade), they comply with HSR regulations. In conclusion, the results demonstrated that weathered red mudstone can be used as a filling material in the newly designed subgrade structure for HSRs.