Earthquake-induced soil liquefaction causes ground and foundation failures, and it challenges the scientific community to explore the liquefaction problem in deep deposit under strong shaking. Due to the capacity limitation of physical modelling facility, it is difficult to reproduce soil liquefaction response of deep sand ground by centrifuge shaking table test. To address this problem, a suite of centrifuge model tests were conducted with the aid of Iai's Type III generalized scaling law (i.e., GSL) to observe the liquefaction response of deep sand ground, where Models 1 and 2 were used to validate the GSL and Model 3 with the validated GSL stands for the deep sand ground with prototype depth of 80 m. The test results of Models 1 and 2 indicate that GSL generally performs well for small-strain shear modulus, nonlinear dynamic response of acceleration and the generation of excess pore water pressure, but leaves considerable errors for post-shaking dissipation process and ground settlement with large plastic strain. The test results of Model 3 indicate that liquefaction is also possible in depth of 30-40 m under shaking event of PBA = 0.4 g and Mw = 7.5. For deeper depth without triggering of liquefaction, a depthdependent power function relationship between the peak excess pore water pressure and Arias intensity has been established. The test results also revealed that consolidation and earthquake shaking history contribute to the development of soil anisotropy in a deep ground, leading to a continuous increase of anisotropy degree, which could be evaluated using the small-strain shear moduli in different stress planes under orthogonal stress conditions.

The dynamic response of piles is a fundamental issue that significantly affects the performance of pile foundations under vertical cyclic loading, yet it has been insufficiently explored due to the limitations of experimental methods. To address this gap, a hydraulic loading device was developed for centrifuge tests, capable of applying loads up to 2.5 kN and 360 Hz. This device could simulate the primary loading conditions encountered in engineering applications, such as those in transportation and power machinery, even after the amplification of the dynamic frequency for centrifuge tests. Furthermore, a design approach for model piles that considers stress wave propagation in pile body and pile-soil dynamic interaction was proposed. Based on the device and approach, centrifuge comparison tests were conducted at 20 g and 30 g, which correspond to the same prototype. The preliminary results confirmed static similarity with only a 1.25% deviation in ultimate bearing capacities at the prototype scale. Cyclic loading tests, conducted under various loading conditions that were identical at the prototype scale, indicated that dynamic displacement, cumulative settlement, and axial forces at different burial depths adhered the dynamic similarity of centrifuge tests. These visible phenomena effectively indicate the rationality of centrifuge tests in studying pile-soil interaction and provide a benchmark for using centrifuge tests to investigate soil-structure dynamic interactions.

Low-saturation liquid-containing granular materials are commonly encountered in both natural and industrial settings, where interstitial liquids significantly affect the motion of particles, while particle size polydispersity plays a crucial role in determining the level of system cohesion. In this study, the collapse of wet polydisperse granular columns is numerically investigated based on the developed discrete element model, with corresponding dam-break experiments performed to validate our numerical model and methodology. The dependence of the dynamics and flow mobility on particle size distribution is primarily examined, and the underlying mechanisms are also explored by analyzing particle path lengths and average fidelity. Building upon the effective Bond number proposed using the mixing theory, a macroscopic cohesion parameter at the material scale is defined by considering the dependence of the collapse on the system size effect. The relevance of this cohesion parameter in describing different wet polydisperse granular collapses is further validated based on our designed experimental tests and DEM simulations. The approach of constructing the cohesion parameters at different scales can be extended to characterize cohesion effects in more complex wet polydisperse granular flows and describe their associated rheological behaviors.