Comments on use of the Barcelona Basic Model for unsaturated soils

2002 ◽  
Vol 26 (15) ◽  
pp. 1561-1571 ◽  
Author(s):  
S. J. Wheeler ◽  
D. Gallipoli ◽  
M. Karstunen
Keyword(s):  
Unsaturated Soils ◽  
Basic Model

Modified state-surface approach to the study of unsaturated soil behavior. Part I: Basic concept

2009 ◽  
Vol 46 (5) ◽  
pp. 536-552 ◽  
Author(s):  
Xiong Zhang ◽  
Robert L. Lytton
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Stress Path ◽  
Complex Stress ◽  
Soil Behavior ◽  
Elastic Surface ◽  
Surface Approach ◽  
Basic Model ◽  
Plastic Hardening ◽  
Complex Stress Path

The traditional state-surface approach to the study of unsaturated soil behavior is becoming much less popular these days, as it uses unique constitutive surfaces to represent unsaturated soil behavior. This approach is essentially a nonlinear elastic formation and cannot be used to explain complex stress-path dependency for unsaturated soils. In this paper, a modified state-surface approach (MSSA) is proposed to represent unsaturated soil behavior under isotropic stress conditions in which a conventional void-ratio state surface is considered to be made up of an elastic surface and a plastic hardening surface. The plastic hardening surface remains stationary at all times, whereas the elastic surface remains unchanged when the soil experiences elastic deformation and moves downward when there is plastic hardening occurrence. Using the MSSA, the loading–collapse (LC) and the suction increase (SI) yield curves in the Barcelona basic model (BBM) are derived. The prediction of three typical cases of soils under isotropic conditions and experimental results using the proposed approach confirmed its feasibility, simplicity, and potential for the study of unsaturated soil behavior.

scholarly journals Numerical and Experimental Analysis of Horizontal Stress Changes and Soil Collapse During Chemical Dissolution in a Modified Oedometer Cell

2016 ◽  
pp. 19-27
Author(s):  
Cecilia Lins ◽  
Nayra Silva ◽  
Leonardo Guimarães ◽  
Analice Lima ◽  
Igor Gomes
Keyword(s):  
Unsaturated Soils ◽  
Horizontal Stress ◽  
Sample Volume ◽  
General Purpose ◽  
Dissolution Process ◽  
Solid Matrix ◽  
Soil Behavior ◽  
Mineral Concentration ◽  
Basic Model ◽  
Stress Changes

The purpose of this paper is to investigate the horizontal stress evolution and soil collapse during the cement dissolution process using a combination of experimental and numerical methods. The experimental procedure was carried out using a modified oedometer cell with horizontal stress measurements and synthetic samples in order to simulate simultaneous cement dissolution, stress changes and sample deformation. The samples were loaded at a constant vertical stress and exposed to a reactive fluid which dissolved the cementation of the artificial soil. During the dissolution process, sample volume decreased and horizontal stress changes were observed. Initially the horizontal stress decreased due to grain mass loss and then increased due to solid matrix rearrangement. Numerical simulation of these coupled chemical and mechanical processes was performed using a general purpose finite element code capable of performing numerical analysis of engineering problems. The constitutive model adopted to reproduce the soil behavior is an extension of the Barcelona Basic Model for unsaturated soils including the cement mineral concentration as state variable. Some new features were incorporated to the original elasto-plastic model in order to represent the results observed in the experiments. In this paper a good agreement between experimental and numerical results was achieved.

scholarly journals Investigating the Effect of Geocell Changes on Slope Stability in Unsaturated Soil

2020 ◽  
Vol 14 (1) ◽  
pp. 66-75
Author(s):  
Behnam Mehdipour ◽  
Hamid Hashemolhosseini ◽  
Bahram Nadi ◽  
Masoud Mirmohamadsadeghi
Keyword(s):  
Slope Stability ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Bending Strength ◽  
Load Capacity ◽  
Three Dimensional ◽  
Bending Moment ◽  
Soil Conditions ◽  
Vertical Side ◽  
Basic Model

The purpose of this research is to investigate the performance and efficiency of reinforced slope in the stability of geocell layers in unsaturated soil conditions. Slope reinforced with geocell acts like a beam in the soil due to the geocell having a height (three-dimensional). Due to its flexural properties, it has moment of inertia as well as bending strength, which reduces the displacement and increases the safety factor of the slope. Taking into consideration unsaturated conditions of soil contributes a lot to making results close to reality. One of the well-known models among elastoplastic models for modeling unsaturated soils is Barcelona Basic Model, which has been added to the FLAC2D software by codification. Changes in thickness, length and number of geocell layers are remarkably effective on slope stability. The results show that the geocell's reinforcing efficiency depends on the number of layers and depth of its placement. As the depth of the geocell's first layer increases, the lateral and vertical side elevation of the upper part of the slope increases with respect to the elevation. Load capacity increases with increasing geocell length. By increasing the length of the geocell layer, the joint strength, the mobilized tensile strength, and the bending moment are increased. At u/H = 0.2, an increase in the bending momentum of about 20% occurs with increasing geocell thickness. In u/H = 1, the increase in bending momentum is 10.4%. In addition, by increasing the thickness of the geocell, the Value of moment of the inertia increases and, as a result, the amount of geocell reinforcement bending moment increases.

Extended Barcelona Basic Model for unsaturated soils under cyclic loadings

2011 ◽  
Vol 38 (5) ◽  
pp. 731-740 ◽  
Author(s):  
Dorival M. Pedroso ◽  
Marcio M. Farias
Keyword(s):  
Unsaturated Soils ◽  
Basic Model

Unified hardening (UH) model for overconsolidated unsaturated soils

2014 ◽  
Vol 51 (7) ◽  
pp. 810-821 ◽  
Author(s):  
Y.P. Yao ◽  
L. Niu ◽  
W.J. Cui
Keyword(s):  
Unsaturated Soils ◽  
Path Dependence ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Stress Path ◽  
Triaxial Tests ◽  
Additional Material ◽  
Basic Model ◽  
Proposed Model ◽  
Unsaturated Clays

Naturally deposited clays are often unsaturated and overconsolidated. Within the frameworks of the Barcelona Basic model (BBM) for normally consolidated unsaturated clays and the unified hardening (UH) model for overconsolidated saturated clays, a three-dimensional constitutive model for overconsolidated unsaturated clays is proposed in this paper. This model can be reduced to the original UH model for overconsolidated saturated clays when suction becomes zero and the BBM when the overconsolidated behaviour disappears. Compared with existing constitutive models for unsaturated clays, the influence of a high overconsolidation ratio (OCR) on wetting deformation can be adequately described. Also, many other characteristics of overconsolidated unsaturated clays can be modelled, including strain-hardening, softening, shear dilatancy, and stress path–dependence behaviour. Compared with the BBM, the proposed model requires no additional material parameter. The validity of the UH model for overconsolidated unsaturated clays has been confirmed by data from two groups of wetting tests performed by the authors and previous triaxial tests in the literature.

scholarly journals Pressuremeter test in unsaturated soils: a numerical study

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Ehsan Keshmiri ◽  
Mohammad Mehdi Ahmadi
Keyword(s):  
Unsaturated Soils ◽  
Numerical Study ◽  
Relative Weight ◽  
Cavity Pressure ◽  
Pressuremeter Test ◽  
Basic Model ◽  
Limit Pressure ◽  
Analysis Technique ◽  
Weight Analysis ◽  
Soil Behaviour

AbstractThe paper presents a numerical analysis of pressuremeter test in unsaturated cohesive soils. In practice, pressuremeter is commonly expanded up to 10–15% cavity strains. At these strains, limit pressure is not usually reached, and its value is estimated by extrapolation. Accordingly, authors suggest using cavity pressure at 10% strain (P10) for the interpretation of pressuremeter test rather than limit pressure. At this strain, it is also assured that plastic strain occurs around the cavity, which is crucial for the interpretations. In unsaturated soils, the moisture at which a soil is tested has a noticeable influence on the pressuremeter cavity pressure, and consequently, on the magnitude of P10. In this paper, unsaturated soil behaviour has been captured by Barcelona basic model (BBM), and the influence of each BBM parameter on the P10 value is explored. Next, relative weight analysis technique is performed to investigate the relative importance of BBM parameters in prediction of P10. Artificial intelligence technique of genetic programming is used to develop a relationship to predict the P10 value in unsaturated soils from BBM parameters. Finally, the application of the proposed equation is shown through illustrative examples.

scholarly journals Numerical and experimental modeling of geomechanical behavior of partially saturated soils

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alireza Sadeghabadi ◽  
Ali Noorzad ◽  
Amirali Zad
Keyword(s):  
Finite Difference ◽  
Unsaturated Soils ◽  
Expansive Soils ◽  
Numerical Analyses ◽  
Partially Saturated ◽  
Basic Model ◽  
Partially Saturated Soils ◽  
Earthen Structures ◽  
Modified Cam Clay ◽  
Set Up

AbstractThe Barcelona Basic Model (BBM) has been implemented in a finite difference-based computer program to simulate the behavior of unsaturated soils subjected to wetting. The BBM implementation was verified using analytical solutions, and the proposed model has been used to simulate the response of a compacted embankment under complete saturation and suction induced conditions. Numerical analyses indicate that considerable amount of total and differential settlements could develop at the top surface of the embankment. BBM is executed into FLAC2D extending a defined module for modified Cam Clay (MCC) and has been set up an analytical solution for suction-dependent stress and strain. Evaluating the effect of anisotropy and nonlinear apparent tensile strength in unsaturated soils, a modification to BBM formulation has been proposed and optimized by developing numerical analyses to reduce the size of elastic region of loading collapse (LC) curve. Then, an experimental study in the literature is investigated by utilizing comparative curves from BBM and modified BBM indicating well agreement with natural circumstances. As a result of the work presented in this research, finite difference codes with BBM and modified BBM has the capability of simulating the real behavior and is operational being applied to problems associated with earthen structures in unsaturated or partially saturated of expansive soils as a three-phases medium.

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