Stiffness degradation and shear strength of silty sands

2004 ◽  
Vol 41 (5) ◽  
pp. 831-843 ◽  
Author(s):  
Junhwan Lee ◽  
Rodrigo Salgado ◽  
J Antonio H Carraro
Keyword(s):  
Shear Strength ◽  
Nonlinear Behavior ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Soil Behavior ◽  
Cone Penetration ◽  
Stress Strain ◽  
Early Loading ◽  
Realistic Representation ◽  
Strain Relationship

Soils behave nonlinearly from very early loading stages. When granular soils contain a certain amount of fines, the degree of nonlinearity also changes, as stiffness and strength characteristics vary with fines content. Hyperbolic stress–strain models and variations of these models are often used for description of the nonlinear behavior. A modified hyperbolic stress–strain relationship is used in this paper for representing the degradation of the elastic modulus of silty sands. The model is based on two modulus degradation parameters that determine the magnitude and rate of modulus degradation as a function of stress level. Realistic representation of soil behavior using this nonlinear relationship requires estimation of the degradation parameters as a function of silt content and relative density DR. A series of triaxial test results on sands containing different amounts of nonplastic silt were analyzed with this purpose. Relationships between the degradation parameters and cone penetration test (CPT) cone resistance qc are also proposed.Key words: hyperbolic model, silty sands, triaxial tests, modulus degradation, stress–strain response, shear strength, Gmax.

Laboratory Triaxial Test Study on Soil Reinforced with Roots of Manilagrass

2011 ◽  
Vol 250-253 ◽  
pp. 1366-1370 ◽  
Author(s):  
Kai Fu Liu ◽  
Xiang Ru Yang ◽  
Xin Yu Xie ◽  
Chang Fu Wu ◽  
Yong Hai Liu
Keyword(s):  
Shear Strength ◽  
Triaxial Test ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Research Results ◽  
Test Study ◽  
Strain Relationship ◽  
Optimal Quantity ◽  
Better Than

Laboratory triaxial tests of the soil reinforced with roots of Manilagrass were carried out in order to understand the stress-strain relationship. The change of shear strength indexes of the soil reinforced with roots of Manilagrass was investigated with the quantity of grassroots planted in the soil specimens. The results of laboratory triaxial tests show that the strength and capacity for resisting the deformation of soil reinforced with roots are better than those of unreinforced soil. And under the certain number of grassroots layers, the strength and capacity for resisting the deformation of soil reinforced with roots increase firstly and then reduce with the increasing of Manilagrass roots quantity. In other words, there is an optimal quantity of Manilagrass roots affecting the strength and capacity for resisting the deformation of soil reinforced with roots. The research results are important for understanding the mechanism and use of vegetation protection for slope.

scholarly journals Investigation of the Mechanical Behavior of Polypropylene Fiber-Reinforced Red Clay

2021 ◽  
Vol 11 (22) ◽  
pp. 10521
Author(s):  
Jia Liu ◽  
Xi’an Li ◽  
Gang Li ◽  
Jinli Zhang
Keyword(s):  
Shear Strength ◽  
Polypropylene Fiber ◽  
Strain Curve ◽  
Triaxial Tests ◽  
High Water Content ◽  
Hyperbolic Model ◽  
High Plasticity ◽  
Fiber Reinforced ◽  
Red Clay ◽  
Stress Strain

Red clay is not easy to use as a natural foundation because of its high water content, high plasticity index, large void ratio, and susceptibility to shrinkage and cracking. In this study, consolidated undrained triaxial tests were conducted to examine the mechanical properties of polypropylene fiber-reinforced red clay and to analyze the influence of the fiber content (FC), fiber length (FL), and cell pressure on its shear strength. By performing a regression analysis on the test data, a hyperbolic constitutive model that considers the influence of FC, FL, and cell pressure was established, and a method was developed to estimate the parameters of the model. The findings show that, in contrast with the nonreinforced red clay, the fiber-reinforced red clay had a stress-strain curve characterized by typical strain hardening, with the shear strength increasing with FC, FL and cell pressure. The calculated results of the model coincide with the test results well, confirming that the hyperbolic model could appropriately describe the stress-strain relationship of polypropylene fiber-reinforced red clay and have reference value for the design and construction of fiber-reinforced red clay foundations.

A Characteristic and a Precisely Constitutive Model for Undrained Clay

2020 ◽  
Vol 975 ◽  
pp. 203-207
Author(s):  
Shih Tsung Hsu ◽  
Wen Chi Hu ◽  
Yu Heng Lin ◽  
Zhuo Ling
Keyword(s):  
Shear Strength ◽  
Plastic Strain ◽  
Constitutive Model ◽  
Strain Hardening ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Proposed Model ◽  
Taipei Basin ◽  
Undrained Shear

Constitutive models for soils are usually adopted in numerical method to analyze the behavior of geotechnical structures. This study performs a series of consolidated-undrained triaxial tests to establish the stress-strain curve of clay. A constitutive model that considers continuous strain hardening-softening is proposed based on the results of triaxial tests. Triaxial test results reveal that undrained shear strength linearly increases with an increase in consolidated pressure , the normalized undrained shear strength is about 0.52 not only for this study but also for the other two cases around Taipei Basin. Due to undrained condition, an associated flow rule between plastic strain increment and stress tensor is adopted. As accumulative plastic strain or/and consolidated pressure change, the mobilized undrained shear strength also changes. All parameters needed for the proposed model can be expressed as a function of undrained shear strength Su, The mobilized undrained shear strength for the proposed model during strain hardening-softening can be in term of accumulative plastic strain. This model can calculate the stress-strain curves of clayed soils accurately.

On the Hypothesis of Effective Stress in Consolidation and Strength for Unsaturated Soils

2012 ◽  
Vol 256-259 ◽  
pp. 108-111
Author(s):  
Seboong Oh ◽  
Ki Hun Park ◽  
Oh Kyun Kwon ◽  
Woo Jung Chung ◽  
Kyung Joon Shin
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Effective Stress ◽  
Unsaturated Soils ◽  
Water Retention Curve ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Soil Behavior ◽  
Soil Water Retention Curve ◽  
Soil Water Retention

The hypothesis on effective stress of unsaturated soils is validated by consolidation strength results of triaxial tests for the compacted residual soil. The effective stress can describe the unsaturated soil behavior, which was defined from shear strength or from soil water characteristic curves. Since the effective stress from consolidation agrees with that from the shear strength, the effective stress from soil water retention curve could describe the unsaturated behavior consistently on both consolidation path and stress at failure. The effective stress can describe the entire unsaturated behavior from consolidation to failure.

scholarly journals Loading rate effect on mechanical properties of an unsaturated silty sand

2021 ◽  
Vol 337 ◽  
pp. 01018
Author(s):  
Christian Barahona ◽  
Luis Sandi ◽  
Juan Carlos Rojas ◽  
Di Emidio Gemmina ◽  
Adam Bezuijen ◽  
...  
Keyword(s):  
Specific Volume ◽  
Loading Rate ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Strain Rates ◽  
Soil Behavior ◽  
Stress Strain ◽  
Loading Rates ◽  
Strain Behavior ◽  
Strain Paths

This paper presents the results of an experimental study on the effects of testing rate on stress-strain behavior and volumetric changes of soil. A series of suction-controlled triaxial tests has been performed on reconstituted specimens of a silty sand (SM), at different stress-rates and strain-rates, respectively. The stress-strain paths were applied by using a modified version of a Bishop and Wesley device (USPv2), capable of applying independently pore-water and air pressure at both ends of the soil sample. During the isotropic compression stages loading rates of 2 and 32 kPa/h have been applied under constant suction values of 15 and 45 kPa. The drained deviator stages were conducted at the same suction levels under strain rates of 0.25 and 2.50 %/h. Results are presented in terms of applied loading rates as a function of the specimens specific volume, preconsolidation pressure, soil compressibility and deviatoric stress against strain rate. A comparison of results was made to a former study, under similar testing conditions of suction and loading rates at University of Napoli Federico II. The effect of loading rate on the soil behavior seems to have an insignificant effect on the specific volume variations, for the imposed values during the testing campaign.

scholarly journals An Incremental Formulation of Constitutive Equations for Deposited Snow

1980 ◽  
Vol 25 (92) ◽  
pp. 289-307 ◽  
Author(s):  
J. Desrues ◽  
F. Darve ◽  
E. Flavigny ◽  
J.P. Navarre ◽  
A. Taillefer
Keyword(s):  
Experimental Data ◽  
Axial Strain ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Theoretical Formulation ◽  
Non Linear ◽  
Incremental Formulation ◽  
Strain Relationship ◽  
Strain Paths ◽  
Incremental Form

Abstract The behaviour of a snow mass under natural loadings (gravity forces, boundary conditions) can be computed by the finite-element method, in so far as a convenient formulation of the stress–strain relationship for snow is available. This paper deals with such a formulation given in incremental form. Experiments have been performed, which show that deposited snow can be considered as a non-linear visco-elastic material with memory effect. The proposed theoretical formulation takes into account these properties. The elastic part of the deformation is assumed to be isotropic and non-linear; the viscous part is expressed in terms of a creep-rate, which results from a superposition of elementary creep-rates according to Boltzmann’s principle. The values of parameters can be obtained from isotropic creep experiments. The experimental data and the resulting parameters are reported. Since the parameters were determined, the formulation of the rheological law was then tested by integration on “stress–strain paths" corresponding to other experiments of a different type, performed on the same snow. The experiments are triaxial tests at constant axial strain-rate, with a preliminary stage of isotropic compression. Experimental data are compared to theoretical curves obtained by integration of the rheological law. The calculated behaviour is consistent with the experimental results.

scholarly journals Experimental Investigation on Shear Strength and Liquefaction Potential of Rubber-Sand Mixtures

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Zhou Enquan ◽  
Wang Qiong
Keyword(s):  
Shear Strength ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Construction Materials ◽  
Horizontal Displacement ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Liquefaction Potential ◽  
Direct Shear Tests ◽  
Rubber Particles

The application of scrap tires as construction materials in civil engineering is one of the most promising ways to recycle this pollutant. The objective of this study was to investigate the shear strength and liquefaction potential of saturated rubber-sand mixtures. Direct shear tests and cyclic triaxial tests were conducted on rubber-sand mixtures at various rubber contents. It was found that the addition of rubber particles to sand changed the shear stress-horizontal displacement development. The addition of rubber particles to sand improved the shear strength slightly and improved resistance to liquefaction significantly. Additionally, a hyperbolic model was proposed to describe the pore water pressure generation. This study demonstrates the effect of rubber particles on the physical properties of sand.

The Maximum Stress in Optical Glass Fibers Under Two-Point Bending

2000 ◽  
Vol 123 (1) ◽  
pp. 70-73 ◽  
Author(s):  
Mikio Muraoka
Keyword(s):  
Axial Force ◽  
Maximum Stress ◽  
Optical Glass ◽  
Glass Fibers ◽  
Order Term ◽  
Nonlinear Behavior ◽  
Bending Stress ◽  
Stress Strain ◽  
Nonlinear Stress ◽  
Strain Relationship

The maximum stress in optical glass fibers subjected to two-point bending was evaluated by E. Suhir, “Effect of the Nonlinear Behavior of the Material on Two-Point Bending of Optical Glass Fibers,” ASME Journal of Electronic Packaging, Vol. 114, pp. 246–250, taking into account the shift in the neutral axis due to the nonlinear stress-strain relationship of the materials. However, the resulting distribution of bending stress on the fiber cross-section is not realistic because it produces a nonzero axial force. In the present study, we derive the correct formulas for evaluating the maximum stress under the valid condition that the bending stress does not contribute to the axial force. Moreover, we employ the nonlinear stress-strain relationship containing a third-order term of strain, which is more appropriate for the materials than that utilized by Suhir.

Shear strength and stress—strain behaviour of Athabasca oil sand at elevated temperatures and pressures

1987 ◽  
Vol 24 (1) ◽  
pp. 1-10 ◽  
Author(s):  
J. G. Agar ◽  
N. R. Morgenstern ◽  
J. D. Scott
Keyword(s):  
Shear Strength ◽  
Oil Sands ◽  
Elevated Temperatures ◽  
Triaxial Compression ◽  
Substantial Reduction ◽  
Hyperbolic Model ◽  
Oil Sand ◽  
Hydrocarbon Gases ◽  
Stress Strain ◽  
Strain Behaviour

The results of a series of triaxial compression tests on undisturbed samples of Athabasca oil sand at elevated temperatures ranging from 20 to 200 °C are summarized. The material tested had experienced gradual unloading and depressurization as a result of erosion in the Saline Creek valley near Fort McMurray. More deeply buried oil sands are known to contain much higher concentrations of dissolved hydrocarbon gases in the pore fluids. The measured shear strength of Athabasca oil sand did not change significantly as a result of the increased temperatures that were applied. The strength of Athabasca oil sand (at 20–200 °C) was found to be greater than comparable shear strengths reported for dense Ottawa sand (at 20 °C). Although heating to 200 °C had little effect on shear strength, it is recognized that pore pressure generation during undrained heating may cause substantial reduction of the available shearing resistance, particularly in gas-rich oil sands. The experimental data were used to investigate the influence of such factors as stress path dependency, microfabric disturbance, and heating to elevated temperatures on the shear strength and stress–strain behaviour of oil sand. Curve fitting of the test data suggests that the hyperbolic model is a useful empirical technique for stress—deformation analyses in oil sands. Hyperbolic stress—strain parameters derived from the experimental results for Athabasca oil sand are presented. Key words: oil sand, Athabasca oil sand, tar sand, shear strength, stress, strain, deformation, heating, high temperature, elevated temperatures, high pressure, elevated pressure, thermal properties, drained heating, undrained heating, triaxial compression testing.

scholarly journals Stress-strain Relationship in Homogeneous and Two-layered Triaxial Test Specimens

2020 ◽  
Author(s):  
Gabriel Oliveira ◽  
Isabel Falorca
Keyword(s):  
Soil Mechanics ◽  
Triaxial Compression ◽  
Nonlinear Behavior ◽  
Confining Pressure ◽  
Test Method ◽  
Compression Tests ◽  
Stress Strain ◽  
Triaxial Apparatus ◽  
Strain Relationship ◽  
The Stability

The stress-strain relationship of a homogeneous specimen, obtained from triaxial compression test, allows to determine stiffness parameters for numerical-method based analyses in common geotechnical software. Stiffness parameters are defined as the ratio of stress to strain along an axis. However, when a heterogeneous specimen is tested, the equivalent elastic modulus that represents a simplification of the nonlinear behavior is complex. This paper presents a study intended to contribute to the debate about the degree to which conventional soil mechanics approaches can be applied to layered specimens. Triaxial compression tests were carried out on both homogeneous and two-layered specimens under a low effective confining pressure of 30 kPa. The triaxial apparatus was chosen since the applied stress and specimen boundary conditions are well defined, and the repeatability of the test method is good. The behavior of both specimens was studied in terms of the stress-strain relationship and stiffness. The main differences were crucial to understanding the composite soil-aggregate interaction, which is discussed and compared. The results indicate that the interface between composite soil and aggregate is important to keep the stability of the layer of aggregate over the soft composite soil, and practical methods of achieving that are suggested.

Sign in / Sign up

Export Citation Format

Share Document