scholarly journals Probabilistic Failure Estimation of an Oblique Loaded Footing Settlement on Cohesive Geomaterials with a Modified Cam Clay Material Yield Function

Geotechnics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 347-384
Author(s):  
Ambrosios-Antonios Savvides ◽  
Manolis Papadrakakis
Keyword(s):  
Random Distribution ◽  
Failure Load ◽  
Constitutive Relations ◽  
Latin Hypercube Sampling ◽  
Element Model ◽  
Shallow Foundation ◽  
Clay Material ◽  
Modified Cam Clay ◽  
Non Linear ◽  
Cam Clay

In this work, a quantitative uncertainty estimation of the random distribution of the soil material properties to the probability density functions of the failure load and failure displacements of a shallow foundation loaded with an oblique load is portrayed. A modified Cam Clay yield constitutive model is adopted with a stochastic finite element model. The random distribution of the reload path inclination κ, the critical state line inclination c of the soil and the permeability k of the Darcian water flow relation, has been assessed with Monte Carlo simulations accelerated by using Latin hypercube sampling. It is proven that both failure load and failure displacements follow Gaussian normal distribution despite the excessive non-linear behaviour of the soil. In addition, as the obliquity increases the mean value of failure load and the failure displacement always increases. The uncertainty of the output failure stress with the increase of the obliquity of the load remains the same. The failure spline of clays can be calculated within an acceptable accuracy with the proposed numerical scheme in every possible geometry and load conditions, considering the obliquity of the load in conjunction with non-linear constitutive relations.

scholarly journals A computational study on the uncertainty quantification of failure of clays with a modified Cam-Clay yield criterion

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Ambrosios A. Savvides ◽  
Manolis Papadrakakis
Keyword(s):  
Random Distribution ◽  
Failure Load ◽  
Computational Study ◽  
Soil Depth ◽  
Yield Criterion ◽  
Constitutive Relations ◽  
Compressibility Factor ◽  
Latin Hypercube Sampling ◽  
Modified Cam Clay ◽  
Cam Clay

AbstractIn this study, the quantitative effect of the random distribution of the soil material properties to the probability density functions of the failure load and displacements is presented. A modified Cam-Clay failure criterion is embedded into a stochastic finite element numerical tool for this purpose. Various assumptions for the random distribution of the compressibility factor $$\kappa$$ κ , of the constitutive relation, the critical state line inclination c of the soil, and the permeability k have been tested and assessed with Latin hypercube sampling followed by Monte Carlo simulation. It is confirmed that both failure load and displacements follow Gaussian normal distribution despite the nonlinearity of the problem. Moreover, as the soil depth increases the mean value of failure load decreases and the failure displacement increases. Consequently, failure mechanism of clays can be determined in this work within an acceptable variability, taking into account the soil depth and nonlinear constitutive relations which in the analytical solutions is not feasible as it is assumed the Meyerhoff theory which considers the elastic halfspace.

An anisotropic elastoplastic model for soft clays

2003 ◽  
Vol 40 (2) ◽  
pp. 403-418 ◽  
Author(s):  
Simon J Wheeler ◽  
Anu Näätänen ◽  
Minna Karstunen ◽  
Matti Lojander
Keyword(s):  
Experimental Data ◽  
Yield Curve ◽  
Constitutive Relations ◽  
Stress Path ◽  
Elastoplastic Model ◽  
Soft Clays ◽  
Rotational Hardening ◽  
Modified Cam Clay ◽  
Cam Clay

An anisotropic elastoplastic model for soft clays is presented. Experimental data from multistage drained triaxial stress path tests on Otaniemi clay from Finland provide support for the proposed shape of the yield curve and for the proposed relationship describing the change of yield curve inclination with plastic straining. Procedures are proposed for determining the initial inclination of the yield curve and the values of the two additional soil constants within the model. Comparisons of model simulations with experimental data demonstrate significant improvements in the performance of the new model over the Modified Cam Clay model. The remaining discrepancies are mainly attributable to the important role of destructuration in the sensitive Otaniemi clay.Key words: anisotropy, constitutive relations, elastoplasticity, laboratory tests, rotational hardening, soft clays.

Calculated and observed behaviour of a reinforced embankment over soft compressible soil

1996 ◽  
Vol 33 (2) ◽  
pp. 324-338 ◽  
Author(s):  
R Kerry Rowe ◽  
C T Gnanendran ◽  
A O Landva ◽  
A J Valsangkar
Keyword(s):  
Progressive Failure ◽  
Large Strain ◽  
Field Measurements ◽  
Clay Material ◽  
Element Analysis ◽  
Foundation Soil ◽  
Clayey Silt ◽  
Modified Cam Clay ◽  
Compressible Soil ◽  
Cam Clay

The finite element analysis of an instrumented geotextile-reinforced test embankment is described and the results are compared with the field measurements. The embankment was constructed to failure on a soft compressible organic clayey silt deposit at Sackville, New Brunswick. The analysis adopts a fully coupled large-strain elasto-plastic Biot consolidation model with modified Cam-clay material behaviour. It is shown that the analysis captured many features of the embankment behaviour. However, it is concluded that the elasto-plastic modified Cam-clay formulation is not adequate for accurately and simultaneously predicting the multiple characteristics (e.g., vertical and horizontal deformations, pore pressures, and geotextile strains) of the embankment behaviour, primarily because of the rate sensitive nature, and the consequent progressive failure of the foundation soil. Key words: embankment, geotextile, reinforcement, analysis, field behaviour, deformations.

A structured Cam Clay model

2002 ◽  
Vol 39 (6) ◽  
pp. 1313-1332 ◽  
Author(s):  
M D Liu ◽  
J P Carter
Keyword(s):  
Parametric Study ◽  
Soil Structure ◽  
Constitutive Relations ◽  
Calcareous Soils ◽  
New Model ◽  
Clay Model ◽  
Proposed Model ◽  
Modified Cam Clay ◽  
Structured Soils ◽  
Cam Clay

A theoretical study of the behaviour of structured soil is presented. A new model, referred to as the Structured Cam Clay model, is formulated by introducing the influence of soil structure into the Modified Cam Clay model. The proposed model is hierarchical, i.e., it is identical to the Modified Cam Clay soil model if a soil has no structure or if its structure is removed by loading. Three new parameters describing the effects of soil structure are introduced, and the results of a parametric study are also presented. The proposed model has been used to predict the behaviour of structured soils in both compression and shearing tests. By making comparisons of predictions with experimental data and by conducting the parametric study it is demonstrated that the new model provides satisfactory qualitative and quantitative modelling of many important features of the behaviour of structured soils.Key words: calcareous soils, clays, fabric, structure, constitutive relations, plasticity.

Numerical Simulation of Triaxial Test in Clayey Soil Using Different Constitutive Relations

2011 ◽  
Vol 243-249 ◽  
pp. 2973-2977 ◽  
Author(s):  
Mohammed Y. Fattah ◽  
Firas A. Salman ◽  
Bestun J. Nareeman
Keyword(s):  
Clayey Soil ◽  
Triaxial Compression ◽  
Constitutive Relations ◽  
Triaxial Tests ◽  
Elastic Model ◽  
Residual Soils ◽  
Stress Strain ◽  
Linear Elastic ◽  
Modified Cam Clay ◽  
Cam Clay

The stress paths to which specimens are subjected in triaxial tests together with the yield surfaces, which may be exercised in different models of such a test are simulated. A laboratory testing on undisturbed clay soil samples was performed in order to characterize the stress-strain behaviour of the residual soils in Sao Paulo sedimentary deposit. The sample is tested under isotropically consolidated drained triaxial compression. Strain controlled procedure was used to simulate stress-strain relationships of the soil. Seven models are used; namely: linear elastic, Duncan-Chang hyperbolic, Mohr-Coulomb, Cam clay, modified Cam clay, new Mohr-Coulomb and Cap model. It was concluded that the results of Cam clay and Duncan Chang models are the closest to the experimental data under low confining pressures; 49 and 98 kPa. Both models exhibit parabolic stress-strain relationships while the linear elastic model results are far away from experimental ones especially at large stress levels. At high confining pressure; 196 kPa, the modified Cam clay best correlates the stress and strain.

scholarly journals Evaluation of Moisture and Decay Models for a New Design Framework for Decay Prediction of Wood

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 721
Author(s):  
Jonas Niklewski ◽  
Philip Bester van Niekerk ◽  
Christian Brischke ◽  
Eva Frühwald Hansson
Keyword(s):  
Service Life ◽  
Wood Decay ◽  
Element Model ◽  
Digital Design ◽  
Design Guideline ◽  
Digital Performance ◽  
Detail Design ◽  
Non Linear ◽  
Service Life Design ◽  
Life Design

Performance-based, service-life design of wood has been the focus of much research in recent decades. Previous works have been synthesized in various factorized design frameworks presented in the form of technical reports. Factorization does not consider the non-linear dependency between decay-influencing effects, such as between detail design and climate variables. The CLICKdesign project is a joint European effort targeting digital, performance-based specification for service-life design (SLD) of wood. This study evaluates the feasibility of using a semi-empirical moisture model (SMM) as a basis for a digital SLD framework. The performance of the SMM is assessed by comparison against a finite element model (FEM). In addition, two different wood decay models (a logistic, LM, and simplified logistic model (SLM)) are compared. While discrepancies between the SMM and FEM were detected particularly at high wood moisture content, the overall performance of the SMM was deemed sufficient for the application. The main source of uncertainty instead stems from the choice of wood decay model. Based on the results, a new method based on pre-calculated time series, empirical equations, and interpolation is proposed for predicting the service life of wood. The method is fast and simple yet able to deal with non-linear effects between weather variables and the design of details. As such, it can easily be implemented as part of a digital design guideline to provide decision support for architects and engineers, with less uncertainty than existing factorized guidelines.

Approximate Macroscale Constitutive Relations Using a Finite Element Based Constitutive Equations for Microscale Contact

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Finite Element ◽  
Contact Force ◽  
Rough Surfaces ◽  
Constitutive Relations ◽  
Cumulative Effect ◽  
Element Model ◽  
Tangential Component ◽  
Total Force ◽  
Asperity Contact ◽  
Elastic Plastic

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the asperity-asperity constitutive relations from a finite element model of their elastic-plastic interaction. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Multiscale modeling of the elastic-plastic rough surface contact is presented in which asperity-level FE-based constitutive relations are statistically summed to obtain total force in the normal and tangential direction. The equations derived are in the form of integral functions and provide expectation of contact force components between two rough surfaces. An analytical fusion technique is developed to combine the piecewise asperity level constitutive relations. This is shown to yield upon statistical summation the cumulative effect resulting in the contact force between two rough surfaces with two components, one in the normal direction and a half-plane tangential component.

Sign in / Sign up

Export Citation Format

Share Document