A multi-material ALE model for investigating impact dynamics of pile-soil systems

Multi-material arbitrary Lagrangian Eulerian (MMALE) method, coupled with moment of fluid (MOF) interface reconstruction, was studied and applied to multi-material large deformation flow problems. In MMALE method, the mesh lines are allowed to cross the material interfaces and mixed cells are introduced. In mixed cells, the MOF method is used to reconstruct the interfaces. The numerical examples show the high accuracy and resolution of MOF-MMALE, it is validated that MOF-MMALE method is an effective way to simulate flow problems of multi-material large deformation.

Dynamic response of piles embedded in granular soil to lateral impacts

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A simplified integrating model is developed for soil-pile dynamic interaction system under seismic loading. Different from previous work, this simplified model constructs the whole system stiffness matrix by combining the stiffness matrix of pile and near region soil system according to the volumetric ratio of pile group and soil system. This simplified model can avoid deviation brought by previous soil-pile surface model and can felicitously simulate the co-working mechanism between soil and piles. The feasibility of the proposed approach is assessed by comparing with in-site observation result of real project.

A new numerically stable sequential algorithm for coupled finite-strain elastoplastic geomechanics and flow

Investigation on lateral impact resistant performance of aluminum foam-filled 6082-T6 aluminum alloy circular tubes: Experimental and numerical study

This special section of the International Journal of Geomechanics contains selected papers that are based on the presentations at the GeoHunan International Conference: Challenges and Recent Advances in Pavement Technologies and Transportation Geotechnics, held in Changsha, Hunan, China, on August 3–6, 2009. The subject of geomechanics has come a long way in developing constitutive models for geomaterials, including nontraditional materials. Yet, there are complex geomechanics problems that do not have well-defined constitutive models and solutions. Recently, advanced modeling and numerical simulation techniques such as neural network, bound theorem, and centrifuge modeling have been employed to solve some of those geomechanics problems. Owing to the rapid expansion in the use of computer software, nonlinear numerical analysis or neural network modeling has become very popular among researchers and practicing engineers in recent years. Although theoretical models have been around for a long time, it has always been challenging to develop such models. Recently, small-scale centrifuge-based simulations have shown a promising capability of modeling prototype geostructures without a gravityinduced in situ stress field. This special section contains six full-length papers covering such advanced modeling and numerical simulations, different from traditional constitutive modeling, in geomechanics. The paper contributed by Xiang et al. discusses settlement prediction on a chimney foundation by a neural network. In their work, seven models with different input series were developed. The optimal model was determined by comparing the forecasting performance. Xiao et al. carried out numerical simulations of a single pile in expansive soil and extensively studied the load transfer mechanism and soil-pile interaction. Chen and Yu present a study on centrifuge modeling, in which staged construction on a reinforced lime-stabilized embankment was simulated by spinning the model at various g-levels. Centrifuge test results were used to verify and validate their numerical analysis. A comprehensive literature review on constitutive modeling of unsaturated soil is presented by Zhang and Li. Some limitations in the framework of the Barcelona Basic Model are discussed, and a new approach is proposed to overcome the limitations. Fu et al. investigated the compressive behavior of anchored rock masses through a series of physical model tests. The test results were compared with specimens without anchor bolts. It was concluded that the improvement attributable to vertical bolts is more effective. Zhao et al. employed an upper bound limit analysis to evaluate the ultimate pullout capacity of horizontal shallow plate anchors. Dilation and nonlinear behavior of soil was found to have profound effects on the ultimate pullout capacity.

Crashworthiness design of graded cellular materials: An asymptotic solution considering loading rate sensitivity

Vertical vibration of a circular foundation in a transversely isotropic poroelastic soil

Lateral impact behaviour of CCFT columns with spherical-cap gap imperfection: Numerical modelling and design method

Effect prediction of stiffened-ring cylindrical shells subjected to drop mass impact

Centrifuge modeling of the behaviour of helical piles in cohesive soils from installation and axial loading

The interaction between a laterally loaded pile and the surrounding soil is typically limited to the shallower soil layer. Often, this zone is above the water table and therefore the interaction takes place under unsaturated conditions. The available evidence is scarce but suggests that unsaturated conditions play a major role on the pile’s response. The actual mechanisms governing the soil–pile interaction under unsaturated soil conditions are not understood entirely, and this paper provides a useful insight on this topic. The analysis is carried out with a fully coupled three-dimensional numerical model, the soil behaviour is simulated with a Modified Cam Clay Model extended to unsaturated conditions. The model accounts for the increase in stiffness and strength of unsaturated soils as well as the volumetric collapse upon wetting. The constitutive model is calibrated on the laboratory data and validated against centrifuge data with satisfying agreement. The results highlight the substantial differences in the soil reaction against the pile depending on different water saturation profiles. The study also shows that the influence of unsaturated conditions on the pile response increases as the pile’s flexibility increases. Comparing the findings with currently available design methods such as the p-y curves, it is found that these do not adequately describe the unsaturated soil reaction against the pile, which opens the door for new research in the field. The proposed numerical model is a promising tool to further investigate the mechanisms underlying the soil–pile interaction under unsaturated soils.

Being the latest representative of gravity installed anchors (GIAs), the OMNI-Max anchor can perform comprehensive behaviors in the seabed, like keying and diving, by adjusting orientation and position to derive higher capacity and to avoid anchor failure. During the keying process of GIAs, many factors may influence the keying capacity, such as the embedment depth, the anchor orientation, the rotational center, the bearing area, and the soil strength. Based on the coupled Eulerian–Lagrangian (CEL) technique, large deformation finite element analyses combined with a bounding-surface plasticity constitutive model are performed to investigate systematically the keying behavior of GIAs in sand. A series of analytical cases involving multiple factors are designed and analyzed to explore the effects of various factors on the keying capacity of GIAs, defined by the soil resistance coefficient during keying. The soil resistance coefficient increases with increasing soil density, while it tends to be stable with the increase of the embedment depth. The closer the rotational center approaches to the two ends of the anchor, the greater the soil resistance coefficient becomes. When the loading arm angle is in π/6–π/4, the soil resistance coefficient takes a relatively small value, while the degree of influence decreases with increasing embedment depth. An explicit expression of the soil resistance coefficient during keying is derived to quantify the effects of various factors, whose applicability and accuracy are validated by different ways. These findings are helpful to understand further the comprehensive anchor behaviors and to promote the application of GIAs in offshore engineering.

Behaviour of cold-formed dimpled columns under lateral impact