Keamogetse Taziba, Mostafa Mohamed, Raj Patel, Omar El-Kezza, Therese Sheehan, Salim Akhtar
The effects of high-speed train induced vibrations on interfacial friction behaviour of granular fills materials are of paramount importance in the railway trackbed design. This paper presents a new dual-function testing apparatus (DPSTA) for evaluating the interfacial friction behaviour of granular materials subject to vibration loading via direct shear and pullout test. This apparatus comprises of four parts, normal load actuator, mechanical horizontal actuator, vibration mechanism and data acquisition system. The DPSTA box section can accommodate a soil sample with dimensions of 450 mm length, 450 mm width and 280 mm depth. The box section front wall is equipped with load cells that can be arranged to measure the shear band within the soil during the direct shear tests as well as the lateral earth pressure during pullout tests. The DPSTA vibration mechanism can induce sinusoidal vibration with G-forces ranging from 0.001 g to 0.08 g onto the granular soil sample simulating high-speed train induced vibrations. Moreover, the mechanical horizontal actuator strain rate remains constant during static and vibrational loading conditions which were tested under normal stresses of 31.57, 61.57 and 91.57 kPa. The data acquisition system can collect data during both static and vibrational loading conditions providing significant insights into the effects of vibrations on interfacial friction during shearing and pullout tests. The commissioning test results have demonstrated the workability and reliability of the new dual-function apparatus DPSTA.