Soil parameters for deformation analysis of sand masses

1987 ◽  
Vol 24 (3) ◽  
pp. 366-376 ◽  
Author(s):  
P. M. Byrne ◽  
H. Cheung ◽  
L. Yan
Keyword(s):  
Relative Density ◽  
Back Analysis ◽  
Field Measurements ◽  
Monotonic Loading ◽  
Triaxial Tests ◽  
Deformation Analysis ◽  
Repeated Loading ◽  
Soil Parameters ◽  
Stress Strain ◽  
Tangent Stiffness

Meaningful stress and deformation analysis of soil structures requires an adequate stress–strain law. Herein are presented guidelines for selection of parameters for a simple incremental hyperbolic stress–strain law for sand based upon a tangent stiffness that varies with stress level. The parameters are obtained from an examination of laboratory and field measurements available in the literature, and are presented in terms of both penetration value and relative density. The laboratory results indicate the importance of first-time or primary loading versus repeated loading on modulus values. Back analysis of field observations for monotonic loading conditions indicates that primary loading modulus values obtained from triaxial tests are appropriate at low relative density, whereas perhaps higher values, in the repeated loading range, are appropriate at high relative densities. Key words: sand, deformation, analysis, hyperbolic, tangent stiffness, modulus, relative density, monotonic loading, repeated loading.

Determination of Elastic and Plastic Subgrade Soil Parameters for Asphalt Cracking and Rutting Prediction

1996 ◽  
Vol 1540 (1) ◽  
pp. 97-104 ◽  
Author(s):  
G. Behzadi ◽  
W. O. Yandell
Keyword(s):  
Moisture Content ◽  
Constitutive Model ◽  
Permanent Deformation ◽  
Triaxial Tests ◽  
Deformation Analysis ◽  
Soil Parameters ◽  
Dry Density ◽  
Silty Clay ◽  
Exponential Relationship ◽  
Deviator Stress

A preliminary step in the prediction of rutting and cracking in a number of accelerated loading facility trials in Australia is presented. The results of laboratory repeated load triaxial tests were used to characterize the residual and resilient deformation of a silty clay subgrade material. The analysis of permanent deformation indicated that the well-known model ∈p = INS can be used to estimate the accumulated strain at any number of loading cycles. The parameter S (the slope of the line in a plot of log ∈p –log N) was found to be independent of stress and density, but very small increases were observed as moisture content increased. The parameter I (the intercept in a plot of log ∈p –log N) was found to be most sensitive to deviator stress. The test results also indicated that I increased with increasing moisture content and decreased as dry density increased. The analysis revealed that an exponential relationship existed between I and deviator stress. This relationship was used to develop a constitutive model for silty clay based on the previously mentioned well-known model. The constitutive model obtained would be able to predict the plastic strain under any number of loads at any specified stress level. Resilient deformation analysis has shown that resilient modulus initially decreased rapidly with increasing deviator stress and then increased slightly or was nearly constant. The elastic and plastic parameters will be used as input for performance predictors such as VESYS and Mechano-Lattice.

scholarly journals Systematic slope stability assessment through deformation field monitoring

2019 ◽  
Vol 92 ◽  
pp. 18009
Author(s):  
Yukun Wei ◽  
Anders B. Lundberg ◽  
Fredrik Resare
Keyword(s):  
Slope Stability ◽  
Measurement Data ◽  
Back Analysis ◽  
Field Measurements ◽  
Field Monitoring ◽  
Monitoring Data ◽  
Soil Parameters ◽  
Stability Assessment ◽  
Stability Of Slopes ◽  
The Stability

Field monitoring is frequently carried out during excavations and other geotechnical activities and provides additional information during the execution of a construction project. The interpretation of field monitoring data is often obscured by measurement noise and disturbance, and a systematic approach to assess both the quality and implications of the field monitoring data is very helpful in geotechnical practice. The possibility to infer practical conclusions from the field monitoring data depends on the type of field measurements, especially in monitoring of the stability of slopes. Pore pressure measurements can serve as a direct measurement of utilized soil strength for a slope, while deformation measurements are significantly more ambiguous and complicates the interpretation. The assessment of slope stability through field monitoring of deformations requires inverse or back analysis of the soil properties, followed by a forward analysis of the resulting slope stability. Such an inverse or back analysis is frequently influenced by non-uniqueness of the material properties and the stability of the measurement data. Systematic approaches to inverse or back analysis have been demonstrated in the scientific literature, but the practical use of these methods is not entirely straight-forward. The current paper presents a case study of systematic slope stability assessment through field measurements of deformations with a review of the field monitoring programme, numerical simulations of deformations, and a simplified approach to back analysis of the soil parameters. The excavation of a slope in an urban environment including layers of organic clay covered with highly heterogeneous gravel fill is used as an example of geotechnical back analysis. The aim is to elucidate some of the challenges in geotechnical back analysis while providing some practical solutions for practice.

Parameters for stress and deformation analysis of rockfill dams

1993 ◽  
Vol 30 (4) ◽  
pp. 690-701 ◽  
Author(s):  
F. Saboya Jr. ◽  
P.M. Byrne
Keyword(s):  
Finite Element ◽  
Stress Ratio ◽  
Back Analysis ◽  
Field Measurements ◽  
Deformation Analysis ◽  
Element Analysis ◽  
Normal Loading ◽  
Tangent Moduli ◽  
Reservoir Filling ◽  
Good Agreement

Stress–strain parameters for modelling the response of rockfill dams to construction and reservoir filling are examined. Parameters from both laboratory tests and back analysis of existing dams are considered. The influence of physical properties of the material, such as mineral composition, grading curves, grain shape, and grain size, is also examined. The results of the study were applied to Foz do Areia dam in Brazil. Finite element analyses were carried out using selected material parameters to predict the response of the dam for both construction and reservoir-filling stages. The predicted and observed results were found to be in good agreement during the construction stage. During reservoir filling, measurements indicated that the dam initially behaved in a much suffer manner than during construction. The stiffer response results from an initial unloading of stress ratio caused by the water load on the face. Under increased reservoir loading, the stress ratio increases again, activating the softer normal loading modulus, leading to substantially larger movements. The predicted results for both construction and reservoir filling are in good agreement with the measurements, provided a stress ratio criterion is used to specify the appropriate tangent moduli. Key words : rockfill, dams, deformations, finite element analysis, field measurements.

Finite Element Modeling of a Mechanically Stabilized Earth Trial Wall

2021 ◽  
pp. 036119812110164
Author(s):  
Andrew Lees ◽  
Michael Dobie
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Retaining Wall ◽  
Back Analysis ◽  
Soil Parameters ◽  
Failure Behavior ◽  
Valuable Insight ◽  
Deformation And Failure ◽  
First Case ◽  
Soil Shear Strength

Polymer geogrid reinforced soil retaining walls have become commonplace, with routine design generally carried out by limiting equilibrium methods. Finite element analysis (FEA) is becoming more widely used to assess the likely deformation behavior of these structures, although in many cases such analyses over-predict deformation compared with monitored structures. Back-analysis of unit tests and instrumented walls improves the techniques and models used in FEA to represent the soil fill, reinforcement and composite behavior caused by the stabilization effect of the geogrid apertures on the soil particles. This composite behavior is most representatively modeled as enhanced soil shear strength. The back-analysis of two test cases provides valuable insight into the benefits of this approach. In the first case, a unit cell was set up such that one side could yield thereby reaching the active earth pressure state. Using FEA a test without geogrid was modeled to help establish appropriate soil parameters. These parameters were then used to back-analyze a test with geogrid present. Simply using the tensile properties of the geogrid over-predicted the yield pressure but using an enhanced soil shear strength gave a satisfactory comparison with the measured result. In the second case a trial retaining wall was back-analyzed to investigate both deformation and failure, the failure induced by cutting the geogrid after construction using heated wires. The closest fit to the actual deformation and failure behavior was provided by using enhanced fill shear strength.

Reliability analysis of static liquefaction of loose sand using the random finite element method

2015 ◽  
Vol 32 (7) ◽  
pp. 2100-2119 ◽  
Author(s):  
Ali Johari ◽  
Jaber Rezvani Pour ◽  
Akbar Javadi
Keyword(s):  
Finite Element ◽  
Pressure Ratio ◽  
Monotonic Loading ◽  
Unit Weight ◽  
Soil Parameters ◽  
Loose Sand ◽  
Element Analysis ◽  
Content Type ◽  
Static Liquefaction ◽  
Random Finite Element

Purpose – Liquefaction of soils is defined as significant reduction in shear strength and stiffness due to increase in pore water pressure. This phenomenon can occur in static (monotonic) or dynamic loading patterns. However, in each pattern, the inherent variability of the soil parameters indicates that this problem is of a probabilistic nature rather than being deterministic. The purpose of this paper is to present a method, based on random finite element method, for reliability assessment of static liquefaction of saturated loose sand under monotonic loading. Design/methodology/approach – The random finite element analysis is used for reliability assessment of static liquefaction of saturated loose sand under monotonic loading. The soil behavior is modeled by an elasto-plastic effective stress constitutive model. Independent soil parameters including saturated unit weight, peak friction angle and initial plastic shear modulus are selected as stochastic parameters which are modeled using a truncated normal probability density function (pdf). Findings – The probability of liquefaction is assessed by pdf of modified pore pressure ratio at each depth. For this purpose pore pressure ratio is modified for monotonic loading of soil. It is shown that the saturated unit weight is the most effective parameter, within the selected stochastic parameters, influencing the static soil liquefaction. Originality/value – This research focuses on the reliability analysis of static liquefaction potential of sandy soils. Three independent soil parameters including saturated unit weight, peak friction angle and initial plastic shear modulus are considered as stochastic input parameters. A computer model, coded in MATLAB, is developed for the random finite element analysis. For modeling of the soil behavior, a specific elasto-plastic effective stress constitutive model (UBCSAND) was used.

Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay

1986 ◽  
Vol 2 (1) ◽  
pp. 139-144 ◽  
Author(s):  
J. H. Atkinson ◽  
J. S. Evans ◽  
D. Richardson
Keyword(s):  
Stress Path ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Stress History ◽  
Strain Behaviour ◽  
Reconstituted Soil ◽  
Path Dependent ◽  
London Clay ◽  
Soil Behaviour

AbstractSoil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works.To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent in situ conditions before and during construction.The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.

Application of a multilaminate model to simulate the undrained response of structured clay to shield tunnelling

2008 ◽  
Vol 45 (1) ◽  
pp. 14-28 ◽  
Author(s):  
H. Kien Dang ◽  
Mohamed A. Meguid
Keyword(s):  
Field Measurements ◽  
Soil Parameters ◽  
Explicit Integration ◽  
Integration Algorithm ◽  
Finite Element Program ◽  
Surface Displacements ◽  
Implicit Integration Algorithm ◽  
Element Program ◽  
Shield Tunnelling ◽  
Structured Clay

A constitutive model based on the multilaminate framework has been implemented into a finite element program to investigate the effect of soil structure on the ground response to tunnelling. The model takes into account the elastic unloading–reloading, inherent and induced anisotropy, destructuration, and bonding effects. The model is successfully calibrated and used to investigate the undrained response of structured sensitive clay in the construction of the Gatineau tunnel in Gatineau, Quebec. Numerical results were compared to the field measurements taken during tunnel construction. To improve the performance of the numerical model, an implicit integration algorithm is implemented and proven to be very effective when coupled with the multilaminate framework as compared to the conventional explicit integration methods. The effect of different soil parameters including bonding and anisotropy on the tunnelling induced displacements and lining stresses is also examined using a comprehensive parametric study. The results indicated that soil bonding and anisotropy have significant effects on the shape of the settlement trough as well as the magnitudes of surface displacements and lining stresses induced by tunnelling.

Impact of random soil properties on stress–strain response

2004 ◽  
Vol 41 (2) ◽  
pp. 351-355 ◽  
Author(s):  
Dieter Stolle ◽  
Peijun Guo ◽  
Gabriel Sedran
Keyword(s):  
Soil Properties ◽  
Constitutive Modelling ◽  
Soil Parameters ◽  
Strain Response ◽  
Constitutive Behaviour ◽  
Stress Strain ◽  
Deterministic Analysis ◽  
Model Predictions ◽  
Random Variability ◽  
The Impact

This paper analyzes the impact of natural random variation of soil properties on the constitutive modelling of geomaterial behaviour. A theoretical framework for accommodating variation in soil properties is presented. The framework is then used to examine the consequence of parameter variability on stress–strain relations. An important observation is that average soil parameters from a series of tests on small specimens, in which density of the specimens varies randomly, do not necessarily reflect the average constitutive behaviour of soil. Model predictions are shown to be consistent with the experimental data.Key words: random variability, deterministic analysis, soil parameters, constitutive model.

A Two-Dimensional Linear Assumed Strain Triangular Element for Finite Deformation Analysis

2005 ◽  
Vol 73 (6) ◽  
pp. 970-976 ◽  
Author(s):  
Fernando G. Flores
Keyword(s):  
Finite Deformation ◽  
Degrees Of Freedom ◽  
Yield Function ◽  
Triangular Element ◽  
Deformation Analysis ◽  
Elastic Model ◽  
Stress Strain ◽  
Metric Tensor ◽  
Assumed Strain ◽  
Non Linear

An assumed strain approach for a linear triangular element able to handle finite deformation problems is presented in this paper. The element is based on a total Lagrangian formulation and its geometry is defined by three nodes with only translational degrees of freedom. The strains are computed from the metric tensor, which is interpolated linearly from the values obtained at the mid-side points of the element. The evaluation of the gradient at each side of the triangle is made resorting to the geometry of the adjacent elements, leading to a four element patch. The approach is then nonconforming, nevertheless the element passes the patch test. To deal with plasticity at finite deformations a logarithmic stress-strain pair is used where an additive decomposition of elastic and plastic strains is adopted. A hyper-elastic model for the elastic linear stress-strain relation and an isotropic quadratic yield function (Mises) for the plastic part are considered. The element has been implemented in two finite element codes: an implicit static/dynamic program for moderately non-linear problems and an explicit dynamic code for problems with strong nonlinearities. Several examples are shown to assess the behavior of the present element in linear plane stress states and non-linear plane strain states as well as in axi-symmetric problems.

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