scholarly journals Deformation characteristics of saturated clay in three-dimensional cyclic stress state

2019 ◽  
Vol 56 (12) ◽  
pp. 1789-1802 ◽  
Author(s):  
Chuan Gu ◽  
Yongzheng Wang ◽  
Yuanqiang Cai ◽  
Jun Wang
Keyword(s):  
Stress State ◽  
Three Dimensional ◽  
Cyclic Stress ◽  
Principal Strain ◽  
Principal Stresses ◽  
Cycle Number ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
Wide Range ◽  
Stress Ratios

The dynamic stress field induced by moving loads is three dimensional, involving the cyclic variation of major, intermediate, and minor principal stresses, while so far very limited laboratory studies have been undertaken on the one-way deformation behavior of saturated clays in three-dimensional stress state. In this study, an advanced true triaxial apparatus, which can apply cyclic major and intermediate principal stresses simultaneously, is employed to carry out a total of 65 one-way cyclic tests on both normally and overconsolidated clays. Four values of overconsolidation ratio (OCR), five values of bcyc, which is termed the coefficient of cyclic intermediate principal stress, and a wide range of cyclic stress ratios (CSR) are tested. Emphasis is put on the effects of bcyc and OCR on the characteristics of permanent major and intermediate principal strains. Test results show that the increase of bcyc significantly reduces the accumulation of major principal strain, and linear relationships are observed between the permanent major principal strain and bcyc for test data with the same CSR, OCR, and cycle number. A critical value of bcyc ≈ 0.5, at which the permanent intermediate principal strain changes from tension to compression, is observed for the remolded clay. Furthermore, an empirical model is proposed, allowing the long-term deformation of saturated clays to be predicted in three-dimensional cyclic stress state.

Anisotropic Behavior of Geomaterial under Three-Dimensional Stress States

2010 ◽  
Vol 160-162 ◽  
pp. 1425-1431
Author(s):  
Kun Yong Zhang ◽  
Yan Gang Zhang ◽  
Chi Wang
Keyword(s):  
Stress State ◽  
Principal Stress ◽  
Three Dimensional ◽  
Complex Stress State ◽  
Triaxial Tests ◽  
Induced Anisotropy ◽  
Principal Stresses ◽  
True Triaxial ◽  
Stress Effects ◽  
Stress Induced Anisotropy

Most soil constitutive models were developed based on the traditional triaxial tests with isotropic assumption, in which the load is applied as the major principal stress direction and the other two principal stresses are symmetric. When such isotropic models are applied to practical analysis, stress induced anisotropy under complex stress state and the middle principal stress effects are often neglected, thus there are many disagreements between the calculated results and the infield testing data. To simulate the practical loading process, true triaxial tests were carried out on geomaterial under three-dimensional stress state. It was found that the stress induced anisotropy effects are remarkable and the middle principal stress effects are obvious because of the initial three-dimensional stress state. Such kind of stress-induced anisotropy could have important impact on the numerical analysis results and should be taken into consideration when developing the constitutive model.

A Rigid-Flexible Boundary True Triaxial Apparatus for Testing Soils in a Three-Dimensional Stress State

2011 ◽  
Vol 34 (3) ◽  
pp. 102886
Author(s):  
L. D. Suits ◽  
T. C. Sheahan ◽  
Jian-Hua Yin ◽  
Wan-Huan Zhou ◽  
M. Kumruzzaman ◽  
...  
Keyword(s):  
Stress State ◽  
Three Dimensional ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus

Stress–strain behaviour of unsaturated soil in true triaxial tests

2002 ◽  
Vol 39 (3) ◽  
pp. 608-619 ◽  
Author(s):  
Hajime Matsuoka ◽  
De'an Sun ◽  
Akiteru Kogane ◽  
Nobuhiko Fukuzawa ◽  
Wataru Ichihara
Keyword(s):  
Unsaturated Soil ◽  
Failure Criterion ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Tests ◽  
Principal Stresses ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus ◽  
True Triaxial Tests

A suction-controlled true triaxial apparatus for unsaturated soil was developed from the existing true triaxial apparatus for sand by attaching a device to supply matric suction to specimens. Using the developed apparatus, true triaxial tests (σ1 [Formula: see text] σ2 [Formula: see text] σ3; where σ1, σ2, and σ3 are the three different principal stresses) on an unsaturated silty soil were carried out under constant suction using the negative pore-water pressure method (s = –uw > 0; ua = 0) for applying the matric suction, s (s = ua – uw; where ua is the pore-air pressure and uw is the pore-water pressure). It was found that the true triaxial test results under three different principal stresses are uniquely arranged on the "extended spatially mobilized plane (extended SMP)" for frictional and cohesive materials that is modified from the original SMP for frictional materials by introducing "a bonding stress, σ0 (= c·cotϕ, where c is cohesion and ϕ is the internal friction angle)." It was also found that the shear strengths of the unsaturated silty clay obtained by the true triaxial apparatus nearly agree with the extended SMP failure criterion (Î1Î2/Î3 = constant, where Î1, Î2, and Î3 are the first, second, and third invariants of the translated stress tensor). The measured stress-strain-strength behaviour of the unsaturated soil in three-dimensional (3D) stresses can be well simulated by an elastoplastic model with the transformed stress based on the extended SMP criterion and a special hardening parameter.Key words: failure criterion, shear strength, special shear test, suction, stress path, unsaturated soil.

Three-dimensional cyclic behavior of saturated clays: comparison between undrained and partly drained conditions

2021 ◽  
Author(s):  
Yanlin Zhang ◽  
Chuan Gu ◽  
Jun Wang ◽  
Yuanqiang Cai
Keyword(s):  
Resilient Modulus ◽  
Three Dimensional ◽  
Cyclic Stress ◽  
Cyclic Behavior ◽  
Triaxial Tests ◽  
Cyclic Stress Ratio ◽  
True Triaxial ◽  
Deformation Behaviors ◽  
Undrained Conditions ◽  
Drained And Undrained Conditions

The cyclic response of subgrade clays under traffic loadings is likely to be partly drained rather than undrained, and the traffic-induced dynamic stress field is three-dimensional rather than axisymmetric. To compare the three-dimensional deformation behaviors of saturated clays between partly drained and undrained conditions, a large number of cyclic true triaxial tests were conducted. Experimental results show that partly drained condition leads to a remarkable increase of permanent major principal strain ( ) compared to undrained condition, and the differences of between the two drainage conditions are affected greatly by the factors of cyclic stress ratio (CSR), overconsolidation ratio (OCR), and coefficient of cyclic intermediate principal stress (bcyc). The increase of bcyc induces a linear reduction of in undrained condition, while it causes a first increase and then a decrease of in partly drained condition. The clays undergo stiffness softening and hardening in partly drained and undrained conditions, respectively, and the effects of bcyc and CSR on the stiffness evolution are very different between the two drainage conditions. The mechanism of the complex and resilient modulus behaviors in three-dimensional state and partly drained condition is further discussed. In addition, two different empirical models are employed to predict in partly drained and undrained conditions, respectively.

Resilient behavior of coarse granular materials in three-dimensional stress state

2020 ◽  
Vol 57 (9) ◽  
pp. 1280-1293 ◽  
Author(s):  
Chuan Gu ◽  
Xingchi Ye ◽  
Jun Wang ◽  
Yuanqiang Cai ◽  
Zhigang Cao ◽  
...  
Keyword(s):  
Stress State ◽  
Granular Materials ◽  
Resilient Modulus ◽  
Three Dimensional ◽  
Principal Stresses ◽  
Axisymmetric Stress State ◽  
Promotion Effect ◽  
Fines Content ◽  
Cyclic Shear ◽  
Resilient Behavior

The traffic-induced cyclic stresses on the road base and subbase courses are usually in three-dimensional stress state, while so far most laboratory studies have focused on the deformation behavior of base and subbase layers in axisymmetric stress state. This study investigates the three-dimensional resilient behavior of coarse granular base and subbase materials based on a true triaxial apparatus. The factors of effective confining pressure, [Formula: see text], amplitude of cyclic shear stress, qampl, coefficient of cyclic intermediate principal stress, bcyc, and fines content are involved. Test results indicate that the increase of either [Formula: see text] or qampl leads to a nonlinear growth of resilient modulus with a decreasing growth rate. bcyc, which is proposed to represent the coupling of cyclic major and intermediate principal stresses, is found to have a promotion effect on the resilient stiffness, and the promotion effect tends to be enhanced by the increase of qampl. A modified model is established to predict the resilient modulus of coarse granular materials in three-dimensional stress state. There appears to exist a critical value of fines content, at which the variation trend of resilient modulus is changed from increasing to decreasing, and the critical fines content is related to both [Formula: see text] and bcyc.

scholarly journals Modified Fracture Mechanics Approach for Hydraulic Fracturing Stress Measurements

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Guiyun Gao ◽  
Chenghu Wang ◽  
Hao Zhou ◽  
Pu Wang
Keyword(s):  
Fracture Mechanics ◽  
Hydraulic Fracturing ◽  
Field Tests ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Stress Determination ◽  
Confining Stress ◽  
Principal Stresses ◽  
True Triaxial ◽  
Stress Ratios

Hydraulic fracturing (HF) test has been widely used to determine in situ stress. The use of a conventional continuum method for this purpose has raised considerable controversies concerning field tests, particularly in the determination of the maximum horizontal principal stress under preexisting fractures. Fracture mechanics methods are very promising when considering preexisting cracks. However, most fracture mechanics methods do not include the effects of confinement on fracture parameters that depend on confining stress. In the present paper, we proposed a modified approach based on fracture mechanics for stress determination considering the relation between fracture toughness and confining stress based on the Rummel and Abou-Sayed methods. Then, we conducted true triaxial hydraulic fracturing tests under different stress ratios for granite and sandstone specimens to verify the proposed approach. The observed typical pressure-time curves indicate that in the conducted hydraulic fracturing tests, the steady fracture growth was attained. Moreover, we demonstrated that the stress ratios influence crack orientations. The horizontal maximum principal stresses determined using the modified Rummel method achieve the lowest relative error compared with other considered stress estimation approaches. This modified fracture mechanics method could be used as a potential alternative approach to obtain a considerably more precise estimation of the maximum horizontal stress in hydraulic fracturing stress determination.

Comparison of Conventional and Pontic Fixed Partial Dentures Over Implants Using the Finite Element Method: Three-Dimensional Analysis of Cortical and Medullary Bone Stress

2020 ◽  
Vol 46 (3) ◽  
pp. 175-181
Author(s):  
Marcelo Bighetti Toniollo ◽  
Mikaelly dos Santos Sá ◽  
Fernanda Pereira Silva ◽  
Giselle Rodrigues Reis ◽  
Ana Paula Macedo ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Medullary Bone ◽  
Principal Stresses ◽  
Bone Stress ◽  
Bone Damage ◽  
Rehabilitation System ◽  
Minimum Requirements

Rehabilitation with implant prostheses in posterior areas requires the maximum number of possible implants due to the greater masticatory load of the region. However, the necessary minimum requirements are not always present in full. This project analyzed the minimum principal stresses (TMiP, representative of the compressive stress) to the friable structures, specifically the vestibular face of the cortical bone and the vestibular and internal/lingual face of the medullary bone. The experimental groups were as follows: the regular splinted group (GR), with a conventional infrastructure on 3 regular-length Morse taper implants (4 × 11 mm); and the regular pontic group (GP), with a pontic infrastructure on 2 regular-length Morse taper implants (4 × 11 mm). The results showed that the TMiP of the cortical and medullary bones were greater for the GP in regions surrounding the implants (especially in the cervical and apical areas of the same region) but they did not reach bone damage levels, at least under the loads applied in this study. It was concluded that greater stress observed in the GP demonstrates greater fragility with this modality of rehabilitation; this should draw the professional's attention to possible biomechanical implications. Whenever possible, professionals should give preference to use of a greater number of implants in the rehabilitation system, with a focus on preserving the supporting tissue with the generation of less intense stresses.

Validation of three‐dimensional echocardiographic principal strain analysis for assessing left ventricular contractility: An animal study

2019 ◽  
Vol 46 (5) ◽  
pp. 2137-2144
Author(s):  
Sahmin Lee ◽  
Seunghyun Choi ◽  
Sehwan Kim ◽  
Yeongjin Jeong ◽  
Kyusup Lee ◽  
...  
Keyword(s):  
Animal Study ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Left Ventricular ◽  
Principal Strain ◽  
Ventricular Contractility ◽  
Left Ventricular Contractility

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

scholarly journals Application of Dendrimers for Treating Parasitic Diseases

Pharmaceutics ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 343
Author(s):  
Veronica Folliero ◽  
Carla Zannella ◽  
Annalisa Chianese ◽  
Debora Stelitano ◽  
Annalisa Ambrosino ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Water Solubility ◽  
Parasitic Infection ◽  
Three Dimensional ◽  
Medical Knowledge ◽  
High Ratio ◽  
Molecular Volume ◽  
Parasitic Infections ◽  
Parasitic Diseases ◽  
Wide Range

Despite advances in medical knowledge, parasitic diseases remain a significant global health burden and their pharmacological treatment is often hampered by drug toxicity. Therefore, drug delivery systems may provide useful advantages when used in combination with conventional therapeutic compounds. Dendrimers are three-dimensional polymeric structures, characterized by a central core, branches and terminal functional groups. These nanostructures are known for their defined structure, great water solubility, biocompatibility and high encapsulation ability against a wide range of molecules. Furthermore, the high ratio between terminal groups and molecular volume render them a hopeful vector for drug delivery. These nanostructures offer several advantages compared to conventional drugs for the treatment of parasitic infection. Dendrimers deliver drugs to target sites with reduced dosage, solving side effects that occur with accepted marketed drugs. In recent years, extensive progress has been made towards the use of dendrimers for therapeutic, prophylactic and diagnostic purposes for the management of parasitic infections. The present review highlights the potential of several dendrimers in the management of parasitic diseases.

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