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The gravitational field affects the evolution of multiphase media, such as rocks, soil, and alloy melts. Hypergravity increases the body force of matter, enhancing the driving force of the relative motion between substances with different densities and accelerating the evolution of multiphase media. Hypergravity experiments provide a new approach to exploring the motion of multiphase media and solving engineering problems. Hypergravity experiments have been conducted in different disciplines, such as materials science, geological science, and geotechnical engineering However, the knowledge barriers between various research fields have caused the development of centrifuges/inflight devices and theoretical research on the mechanisms of matter in motion in hypergravity to lag behind the application of hypergravity experiments, limiting the progress in these experiments. This article systematically summarizes and proposes the fundamentals of hypergravity experiments, while the scientific challenge of the nonlinear hypergravity effect induced by high hypergravity on multiphase media evolution is clarified. Evaluation criteria are proposed for the noninertial frame effects of the centrifugal hypergravity field. The development of the high-centrifugal acceleration, large-capacity, and long-beam centrifuges are determined as the future research direction. Representative cases are used to demonstrate the effectiveness and great potential of the hypergravity experiments for the solidification of alloy melts and physical modeling. Challenges in the experimental methodology are also clarified. This paper reviews the fundamentals and applications of hypergravity experiments in various disciplines, pointing out the research direction of hypergravity experiments on multiphase media evolution.

An augmented finite element method (“A-FEM”) is presented that is a variant of the method of Hansbo and Hansbo (Comput Methods Appl Mech Eng, 193: 3523–3540, 2004), which can fully account for arbitrary discontinuities that traverse the interior of elements. Like the method of Hansbo and Hansbo, the A-FEM preserves elemental locality, because element augmentation is implemented within single elements and involves nodal information from the modified element only. The A-FEM offers the additional convenience that the augmentation is implemented via separable mathematical elements that employ standard finite element nodal interpolation only. Thus, the formulation is fully compatible with standard commercial finite element packages and can be incorporated as a user element without access to the source code. Because possible discontinuities include both elastic heterogeneity and cracks, the A-FEM is ideally suited to modeling damage evolution in structural or biological materials with complex morphology. Elements of a multi-scale approach to analyzing damage mechanisms in laminated or woven textile composites are used to validate the A-FEM and illustrate its possible uses. Key capabilities of the formulation include the use of meshes that need not conform to the surfaces of heterogeneities; the ability to apply the augmented element recursively, enabling modeling of multiple discontinuities arising on different, possibly intersecting surfaces within an element; and the ease with which cohesive zone models of nonlinear fracture can be incorporated.

Internal erosion can trigger severe engineering disasters, such as the failure of embankment dams and uneven settlement of buildings and sinkholes. This paper comprehensively reviewed the mechanisms of soil internal erosion studied by numerical simulation, which can facilitate uncovering the internal erosion mechanism by tracing the movement of particles. The initiation and development of internal erosion are jointly influenced by the geometric, mechanical, and hydraulic conditions, which determine the pore channels and force chains in soil. The geometric conditions are fundamental to erosion resistance, whereas the mechanical conditions can significantly change the soil erosion resistance, and the hydraulic conditions determine whether erosion occurs. The erosion process can be divided into particle detachment, transport, and clogging. The first is primarily affected by force chains, whereas the latter two are mostly affected by the pore channels. The stability of the soil is mainly determined by force chains and pore channels, whereas the hydraulic conditions act as external disturbances. The erosion process is accompanied by contact failure, force chain bending, kinetic energy burst of particles, and other processes due to multi-factor coupling.

Soil strain is the key parameter to control the elasto-plastic deformation and even the failure processes. To overcome the defect that the strain of the model soil is always smaller than that of the prototype in Iai’s generalized scaling law (GSL), a modified scaling law was proposed based on Iai’s GSL to secure the same dynamic shear strain between the centrifuge model and the prototype by modulating the amplitude and frequency of the input motion at the base. A suite of dynamic centrifuge model tests of dry sand level ground was conducted with the same overall scaling factor ( λ =200) under different centrifugal accelerations by using the technique of “modeling of models” to validate the modified GSL. The test results show that the modified GSL could achieve the same dynamic strain in model as that of the prototype, leading to better modeling for geotechnical problems where dynamic strain dominates the response or failure of soils. Finally, the applicability of the proposed scaling law and possible constraints on geometry scaling due to the capability limits of existing centrifuge shaking tables are discussed.

Geotechnical centrifuge modeling, which can effectively simulate the stress field of soil in the prototype, was adopted to help investigate the effects of the uplifting of pipes buried at different depths within a medium dense sand under (1) a static state and (2) a dynamic state. To acquire the displacement vector fields and strain contours in the soil around pipes, particle image velocimetry technology was applied. The study focused on the deformation mechanisms of soil surrounding the pipes and ground surface. Two different deformation triggers, external forces and soil liquefaction, were considered. When uplifting was caused by an external force, the relationship between the soil deformation and uplift resistance was similar to the typical ground load–deformation characteristic relationships. There was little displacement of soil during the elastic stage. Along with the uplifting of the pipe, a plastic zone within the range of one pipe diameter (1D) above the pipe appeared in the soil at peak resistance. During the post-peak period, a shear failure plane extended upwards to the ground surface, at an inclined angle forming a trumpet-like shape. The ground surface deformation range expanded according to the buried depth of the pipe. Meanwhile, in a liquefied field, the soil flowed within a heart-shaped region around the pipe. The soil deformation region surrounding a shallow buried pipe, with a width of 5D–6D, was far larger than that found for a pipe buried at the same depth in a static field. Both heave and settlement could be observed on the ground surface.

Underground pipelines are widely applied in the so-called lifeline engineerings. It shows according to seismic surveys that the damage from soil liquefaction to underground pipelines was the most serious, whose failures were mainly in the form of pipeline uplifting. In the present study, dynamic centrifuge model tests were conducted to study the uplifting behaviors of shallow-buried pipeline subjected to seismic vibration in liquefied sites. The uplifting mechanism was discussed through the responses of the pore water pressure and earth pressure around the pipeline. Additionally, the analysis of force, which the pipeline was subjected to before and during vibration, was introduced and proved to be reasonable by the comparison of the measured and the calculated results. The uplifting behavior of pipe is the combination effects of multiple forces, and is highly dependent on the excess pore pressure.

The great Wenchuan earthquake ( M s = 8.0) in 2008 caused severe damage in the western part of the Chengdu Plain. Soil liquefaction was one of the major causes of damage in the plain areas, and proper evaluation of liquefaction potential is important in the definition of the seismic hazard facing a given region and post-earthquake reconstruction. In this paper, a simplified procedure is proposed for liquefaction assessment of sandy deposits using shear wave velocity ( V s ), and soil liquefaction from the Banqiao School site was preliminarily investigated after the earthquake. Boreholes were made at the site and shear wave velocities were measured both by SASW and down-hole methods. Based on the in-situ soil information and V s profiles, the liquefaction potential of this site was evaluated. The results are reasonably consistent with the actual field behavior observed after the earthquake, indicating that the proposed procedure is effective. The possible effects of gravel and fines contents on liquefaction of sandy soils were also briefly discussed.

It is important to test water content of rock-soil mixtures efficiently and accurately to ensure both the quality control of compaction and assessment of the geotechnical engineering properties. To overcome time and energy wastage and probe insertion problems when using the traditional calibration method, a TDR coaxial test tube calibration arrangement using an upward infiltration method was designed. This arrangement was then used to study the influence of dry density, pore fluid conductivity, and soil/rock ratio on the relationship between water content and the dielectric constant of rock-soil mixtures. The results show that the empirical calibration equation forms for rock-soil mixtures can be the same as for soil materials. The effect of dry density on the calibration equation has the most significance and the influence of pore fluid conductivity can be ignored. The impact of variation of the soil/rock ratio can be neutralized by considering the effect of dry density in the calibration equation for the same kind of soil and rock. The empirical equations proposed by Zhao et al. show a good accuracy for rock-soil mixtures, indicating that the TDR method can be used to test gravimetric water content conveniently and efficiently without calibration in the field.

The safe landing of a Moon lander and the performance of the precise instruments it carries may be affected by too heavy impact on touchdown. Accordingly, landing characteristics have become an important research focus. Described in this paper are model tests carried out using simulated lunar soils of different relative densities (called “simulant” lunar soils below), with a scale reduction factor of 1/6 to consider the relative gravities of the Earth and Moon. In the model tests, the lander was simplified as an impact column with a saucer-shaped footpad with various impact landing masses and velocities. Based on the test results, the relationships between the footpad peak feature responses and impact kinetic energy have been analyzed. Numerical simulation analyses were also conducted to simulate the vertical impact process. A 3D dynamic finite element model was built for which the material parameters were obtained from laboratory test data. When compared with the model tests, the numerical model proved able to effectively simulate the dynamic characteristics of the axial forces, accelerations, and penetration depths of the impact column during landing. This numerical model can be further used as required for simulating oblique landing impacts.

An increasing number of extra-long and large-scale civil engineering projects are adjacent to, crossing, or traversing active faults due to urbanization, making the study of the interaction between faults and shallow foundations essential. In this study, 14 different combinations of foundation positions and loads were tested under reverse faulting to observe the failure patterns of the overlying soil and movements of the foundation. In addition to the three classic types of fault rupture summarized by Ahmed and Bransby (J Geotech Geoenviron Eng 135:914–924,  2009 ) in centrifuge tests, two novel patterns of transitional fault ruptures were identified, making the transition of the fault rupture from the hanging wall to the footwall more gradual. The characteristics of vertical displacement of the surface and movement of the foundation under these five different rupture patterns are summarized, enabling an inference of unobservable fault rupture propagation beneath the surface on the basis of these visible features above the surface. Principal stress axis rotation angles and the soil compaction coefficient were applied to quantitatively explain the combined effects of the foundation position and load on the formation of different types of rupture patterns.