A novel computational approach for large deformation and post‐failure analyses of segmental retaining wall systems     

Ha H. Bui  Jayantha K. Kodikara  Abdelmalek Bouazza  Asadul Haque  Pathegama G. Ranjith 《国际地质力学数值与分析法杂志》2014,38(13):1321-1340

Segmental retaining wall (SRW) systems are commonly used in geotechnical practice to stabilize cut and fill slopes. Because of their flexibility, these systems can tolerate minor movements and settlements without incurring damage or crack. Despite these advantages, very few numerical studies of large deformations and post‐failure behavior of SRW systems are found in the current literature. Traditional numerical methods, such as the finite element method, suffer from mesh entanglement, thus are unable to simulate large deformations and flexible behavior of retaining wall blocks in SRW systems. To overcome the above limitations, a novel computational framework based on the smoothed particle hydrodynamics (SPH) method was developed to simulate large deformations and post‐failure behavior of soils and retaining wall blocks in SRW systems. The proposed numerical framework is a hybrid continuum/discontinuum approach that can model soil as an elasto‐plastic material and retaining wall blocks as independent rigid bodies associated with both translational and rotational degrees of freedom. A new contact model is proposed within the SPH framework to simulate the interaction between the soil and the blocks and between the blocks. As an application of the proposed numerical method, a two‐dimensional simulation of an SRW collapse was simulated and compared to experimental results conducted under the same conditions. The results showed that the proposed computational approach provided satisfactory agreement with the experiment. This suggests that the new framework is a promising numerical approach to model SRW systems. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Structural softening,mesh dependence,and regularisation in non-associated plastic flow     

Sepideh Alizadeh Sabet  René de Borst 《国际地质力学数值与分析法杂志》2019,43(13):2170-2183

A severe dependence of numerical simulations on the mesh density is usually attributed to the presence of strain softening in the constitutive relation. However, other material instabilities, like non-associated plastic flow, can also cause mesh sensitivity. Indeed, loss of ellipticity in quasi-static analyses is the fundamental cause of the observed mesh dependence. It has been known since long that non-associated plastic flow can cause loss of ellipticity, but the consequence for mesh sensitivity, and subsequently, for the difficulty of the equilibrium-finding iterative procedure to converge have remained largely unnoticed. We first demonstrate at the hand of a biaxial test structural softening and a marked mesh dependence for an ideally plastic material equipped with a non-associated flow rule. The phenomena are then analysed in depth using an infinitely long shear layer. Finally, it is shown that the mesh effect disappears when the standard continuum model is replaced by a Cosserat continuum, a well-known regularisation method for strain-softening constitutive relations.  相似文献   

Mathematical identification of diffuse and localized instabilities in fluid‐saturated sands     

Constance Mihalache  Giuseppe Buscarnera 《国际地质力学数值与分析法杂志》2014,38(2):111-141

The mathematical properties of diffuse and localized failure modes in fluid‐saturated sands are investigated. The granular medium is modeled as an elastoplastic solid, and a recently proposed set of scalar indices, here referred to as moduli of instability, is used to identify the onset of potential bifurcations of the incremental response. First, the analytical properties of these moduli are discussed, stressing their dependence on the kinematic constraints associated with the imposed deformation modes. Then, by using an elastoplastic model for sands, drained and undrained loading paths are simulated under axisymmetric, plane‐strain and simple shear conditions. For each deformation mode, the instability moduli are computed and monitored throughout the simulations, with the purpose of elucidating the consequences of changes in control conditions. In addition, it is illustrated that suitable linear transformations allow the same strategy to be used to perform drained or undrained shear band analyses and predict the interval of possible band inclinations. The final comparison against literature experiments on loose Hostun sand shows that the instability moduli are indicators of the loss of resistance against specific modes of deformation. As a result, they can be used to identify and explain a number of failure mechanisms that can be commonly observed in experiments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Short-term effects of fishing on life history traits of fishes   总被引：4，自引：4，他引：4  

Rochet  Marie-Joelle 《ICES Journal of Marine Science》1998,55(3):371-391

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Estimating reaction norms for age and size at maturation with reconstructed immature size distributions: a new technique illustrated by application to Northeast Arctic cod   总被引：3，自引：1，他引：3  

Heino  Mikko; Dieckmann  Ulf; Godo  Olav Rune 《ICES Journal of Marine Science》2002,59(3):562-575

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Estimation of Marine Soil Parameters for Preliminary Analysis of Geotechnical Structures in the Taiwan Strait Connection Project     

Jian-Hua Yin  Hong-Jian Liao  Cheng Zhou  Chun-Man Cheng 《Marine Georesources & Geotechnology》2003,21(3):167-182

No direct site investigation (SI) data are available for the prospective Taiwan Strait connection project. Any quantitative analysis on the performance of a tunnel, a bridge, or of on-shore (or off-shore) connections needs reasonable geotechnical model parameters. Correlations between basic properties of marine soils and geotechnical model parameters have been established before by the first author based on a large amount of laboratory test data. The established correlations together with other relations considering main types of soils in the Taiwan Strait region are used to estimate the geotechnical model parameters of the marine soils. These correlations and estimated values of the geotechnical parameters of the marine soils are presented and discussed in this article. The estimated geotechnical model parameters can be used for a preliminary analysis of the performance of geotechnical structures of the prospective project.  相似文献   

Dietary plasticity of the oceanic striped dolphin, Stenella coeruleoalba, in the neritic waters of the Bay of Biscay     

J. Spitz  E. Richard  L. Meynier  C. Pusineri  V. Ridoux   《Journal of Sea Research》2006,55(4):309-320

The striped dolphin, Stenella coeruleoalba, is an oceanic species that occasionally occurs in neritic habitats; in the Bay of Biscay it is abundant offshore and erratic in occurrence over the shelf. Given that prey assemblages differ widely among these habitats both in terms of taxonomic composition and of ecology, this would suggest that striped dolphins are able to shift from vertically migrating meso-pelagic prey to neritic or coastal prey types. We investigated the striped dolphin's dietary plasticity by examining the stomach contents of individuals stranded along the French Atlantic coast. 1109 prey items were identified belonging to 30 distinct taxa and their biomass was calculated. Fish accounted for 91% of the diet by number and 61% by mass; the rest was mostly cephalopods, crustaceans being present as trace. Specific composition included both oceanic (myctophid and sternoptychid fish; histioteuthid, gonatid and brachioteuthid cephalopods), neritic (gadids and anchovy; loliginid, sepiolid and sepiid cephalopods) and even coastal (atherinid fish) prey types, showing that these animals had changed their diet as they moved over the shelf.  相似文献   

Dimorphism in the Ascidian Pyura stolonifera Near Melbourne, Australia, and its Evaluation Through Field Transplant Experiments     

J. E. Dalby  Jr 《Marine Ecology》1997,18(3):253-271

Abstract. On the central coast of Victoria, Australia, the ascidian Pyura stolonifera (H eller . 1878) assumes 2 morphs. a yellow form living exclusively on inner shores, and a brown morph mainly on outer coasts. Distributional surveys, morphological analyses and field transplant experiments were conducted as part of a multidisciplinary investigation designed to elucidate the environmental and genetic components of dimorphism in this species. Distributional surveys revealed that the 2 morphs have a parapatric distribution. Morphological analyses showed striking differences between morphs in colours of tissue types, external anatomy, morphometry and gravimetry. Possible ecological significances of this morphological differentiation are discussed. Transplant experiments, in which morphs were moved within and between habitats, yielded no evidence for morphological plasticity in adults of this species for the great majority of characters examined.  相似文献   

A rigorous semi‐analytical solution for undrained cylindrical cavity expansion in critical state soils          下载免费PDF全文

Apostolos Vrakas 《国际地质力学数值与分析法杂志》2016,40(15):2137-2160

This paper presents a generalized, rigorous and simple large strain solution for the undrained expansion of a vertical cylindrical cavity in critical state soils using a rate‐based plasticity formulation: the initial stress field is taken as anisotropic, that is with horizontal stresses that differ from the vertical stress, and the soil is assumed to satisfy any two‐invariant constitutive model from the critical state (Cam‐clay) family; no simplifying assumption is made during the mathematical derivation; calculating the effective stresses around the cavity requires the solution of a nonlinear equation by means of the Newton–Raphson method in combination with quadrature. Cavity expansion curves and stress distributions in the soil are then presented for different critical state models (including the modified Cam‐clay model). The solution derived can be useful for estimating the instantaneous response of saturated low‐permeability soils around piles and self‐boring pressuremeters and can serve as trustworthy benchmark for numerical analysis codes. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Modelling chemo‐hydro‐mechanical behaviour of unsaturated clays: a feasibility study     

Z. Liu  N. Boukpeti  X. Li  F. Collin  J.‐P. Radu  T. Hueckel  R. Charlier 《国际地质力学数值与分析法杂志》2005,29(9):919-940

Effective capabilities of combined chemo‐elasto‐plastic and unsaturated soil models to simulate chemo‐hydro‐mechanical (CHM) behaviour of clays are examined in numerical simulations through selected boundary value problems. The objective is to investigate the feasibility of approaching such complex material behaviour numerically by combining two existing models. The chemo‐mechanical effects are described using the concept of chemical softening consisting of reduction of the pre‐consolidation pressure proposed originally by Hueckel (Can. Geotech. J. 1992; 29 :1071–1086; Int. J. Numer. Anal. Methods Geomech. 1997; 21 :43–72). An additional chemical softening mechanism is considered, consisting in a decrease of cohesion with an increase in contaminant concentration. The influence of partial saturation on the constitutive behaviour is modelled following Barcelona basic model (BBM) formulation (Géotech. 1990; 40 (3):405–430; Can. Geotech. J. 1992; 29 :1013–1032). The equilibrium equations combined with the CHM constitutive relations, and the governing equations for flow of fluids and contaminant transport, are solved numerically using finite element. The emphasis is laid on understanding the role that the individual chemical effects such as chemo‐elastic swelling, or chemo‐plastic consolidation, or finally, chemical loss of cohesion have in the overall response of the soil mass. The numerical problems analysed concern the chemical effects in response to wetting of a clay specimen with an organic liquid in rigid wall consolidometer, during biaxial loading up to failure, and in response to fresh water influx during tunnel excavation in swelling clay. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献