scholarly journals Cracking behaviour of fine-grained soils: from laboratory testing to numerical modelling

2019 ◽  
Vol 92 ◽  
pp. 16004
Author(s):  
Pierre Gerard ◽  
Ian Murray ◽  
Alessandro Tarantino
Keyword(s):  
Effective Stress ◽  
Failure Criterion ◽  
Shear Failure ◽  
Digital Camera ◽  
Failure Criteria ◽  
Fine Grained ◽  
Fine Grained Soil ◽  
Desiccation Cracking ◽  
Stress States ◽  
Stress Dependent

Many experimental evidences suggest that desiccation cracks in clay initiate as a result of the mobilization of soil tensile strength. However this mechanical approach disregards the cohesionless and effective stress-dependent behaviour of fine-grained soil. On the other hand recent findings in the literature suggest that effective stress-dependent shear failure criteria would be appropriate to explain the mechanisms of desiccation cracking for tensile total stress states. This work aims at assessing the validity of a shear failure criterion to predict the onset of cracking in clay forms exposed to air drying. Clay forms of various geometries were experimentally subjected to non-uniform hydraulic and mechanical boundary conditions. Time and location for crack initiation are monitored using a digital camera. Cracking experiments are then modelled in a hydro-mechanical framework using an effective-stress shear failure criterion. The comparison of simulations with experimental results for both the time and the location of cracking allows assuming that cracking occurs due to failure in shearing.

Axial-Shear Failure Behavior of Human Femoral Trabecular Bone

1999 ◽  
Author(s):  
Yves P. Arramon ◽  
Oscar C. Yeh ◽  
Elise F. Morgan ◽  
Tony M. Keaveny
Keyword(s):  
Mechanical Behavior ◽  
Trabecular Bone ◽  
Failure Criterion ◽  
Shear Failure ◽  
Computer Models ◽  
Failure Behavior ◽  
Multiaxial Loading ◽  
Bone Implant ◽  
Computer Aided ◽  
Stress States

Abstract An understanding of the failure of trabecular bone subjected to multiaxial loading has relevance in the mechanics of trauma and bone implant interfaces. The development of computer aided tomography-based computer models allow predictions of the mechanical behavior of whole bones when subjected to stress states too complex to be described analytically (Ford et al., 1996; Keyak et al., 1998; Oden et al., 1998). However, these models cannot confidently predict the failure of the trabecular bone without an experimentally validated multiaxial failure criterion.

The Residual Stress in Thawing Soils

1973 ◽  
Vol 10 (4) ◽  
pp. 571-580 ◽  
Author(s):  
J. F. Nixon ◽  
N. R. Morgenstern
Keyword(s):  
Residual Stress ◽  
Effective Stress ◽  
Simple Procedure ◽  
Frozen Soil ◽  
Fine Grained ◽  
Deformation Properties ◽  
Fine Grained Soil ◽  
Soil Skeleton ◽  
Strength And Deformation ◽  
Undrained Strength

If a fine grained soil is thawed under undrained conditions, in general an effective stress exists in the soil skeleton. This effective stress is termed the residual stress. In ice-rich soil the residual stress may be zero, but various combinations of stress and thermal histories can result in significant residual stresses being generated upon thawing.A simple procedure for measuring the residual stress is described and the method is employed to obtain values for the residual stress in natural and reconstituted samples of frozen soil. The residual stress is found to be dependent on the void ratio in the thawed undrained condition. A profile of the residual stress with depth is given for the natural permafrost samples that have been tested.Some implications of the residual stress in practice are discussed, with particular emphasis on the undrained strength and deformation properties of thawed permafrost.

scholarly journals An Experiment on Incorporation of Bentonite Clay in Mortar

2020 ◽  
Vol 8 (5) ◽  
pp. 3866-3873
Keyword(s):  
Clay Mineral ◽  
Chemical Weathering ◽  
Shear Failure ◽  
Bentonite Clay ◽  
Stone Masonry ◽  
Major Constituent ◽  
Fine Aggregate ◽  
Fine Grained ◽  
Fine Grained Soil ◽  
Fixed Proportion

Mortar refers to a binding paste which is workable in nature and consistency, used as a binder in construction activities such as stone bonding in stone masonry, brick bonding in brick masonry and as well as in concrete works. Mortar is often used as a means for decorative works attaining to its workable nature, which in this project I have intended to enhance. Mortar is further used as a sealant in order to fill cracks and gaps within the structure. The term mortar is taken from the Latin term “ mortarium” which means crushed. Mortar is often prepared by mixing a suitable binder, fine aggregate or in simpler terms sand and water by a fixed proportion by mass or volume. The ratio of the constituents depends on the quality and magnitude of the work being done. Mortar gains its strength due to the various chemical reactions that occur while the mortar is being cured in water, gaining 99% strength in 28 days. The most used binder in modern times is Portland cement, which was used at the onset of 20th century. A common binder prevailing in the past was lime and the associated mortar mix was called lime mortar. A major part of this project lies in the use of clay as a substitute for sand in mortar. Clay refers to a fine-grained soil deriving its origin from naturally occurring rocks that have undergone chemical weathering. Clay mineral can be classified into three types i.e. Kaolinite, montmorillonite and illite. The type of clay that has been used in this experiment is Bentonite which is a volcanic in origin and has montmorillonite as a major constituent. Clay has water entrapped within its structure and the amount of water depends on the type of clay mineral being dealt with. One of the major properties of clay that I have tried to exploit in this project is its plastic nature i.e. the ability of the soil to gain resistance against shear failure by sliding as they get into a dry state as opposed to possessing very little or no resistance to the same when they absorb water. Attaining help of various properties of clay, in this project I will try to evaluate the various properties of a mortar cube by mixing a fixed proportion by mass of clay in the same and present my observations

scholarly journals Computational micromechanics-based prediction of the failure of unidirectional composite lamina subjected to transverse and in-plane shear stress states

2020 ◽  
Vol 54 (24) ◽  
pp. 3637-3654 ◽  
Author(s):  
Lei Wan ◽  
Yaser Ismail ◽  
Chao Zhu ◽  
Ping Zhu ◽  
Yong Sheng ◽  
...  
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Finite Element Model ◽  
Failure Criterion ◽  
Element Model ◽  
Failure Criteria ◽  
Plane Shear ◽  
The Matrix ◽  
Stress States ◽  
The Finite Element Model

This paper presents a micromechanics-based 3D finite element model for predicting the damage initiation, propagation, and failure strength of TC33/Epoxy carbon fiber reinforced polymer (CFRP) unidirectional lamina under biaxial loadings. The finite element model is generated by introducing representative volume element (RVE) with a random distribution of fibers and a non-zero thickness, numerically identified interface phase via cohesive elements. In the finite element model, the carbon fibers are considered as elastic, while the elasto-plastic behavior and damage of the matrix are governed by extended Drucker–Prager plastic yielding model and ductile damage criterion. By imposing periodic boundary conditions to the RVEs, various cases subjected to uniaxial and biaxial loading conditions are carried out. During the combined transverse and in-plane shear stress states, a failure transition from compression- or tension-dominated to shear-dominated is captured, and the effects of the interfacial strength on the transition damage mechanisms are discussed. The corresponding failure locus is compared with the upper bound and lower bound predictions of three phenomenological failure criteria (Hashin, Tasi–Wu, and Puck failure criteria) for composites. It was found that in the interface-dominated failure of a CFRP lamina with a weak interface, the Hashin failure criterion performs best among the currently popular failure criteria. However, in the matrix-dominated failure with a strong interface, the Puck failure criterion performs best. Comparing these three criteria, it can be seen the Tsai–Wu may be generally better than both of others as it presents more neutral predictions in both of the examined cases.

scholarly journals New Interface for Assessing Wellbore Stability at Critical Mud Pressures and Various Failure Criteria: Including Stress Trajectories and Deviatoric Stress Distributions

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 4019
Author(s):  
Wang ◽  
Weijermars
Keyword(s):  
Shear Failure ◽  
Axial Stress ◽  
Failure Criteria ◽  
Wellbore Stability ◽  
Tensile Failure ◽  
Wellbore Instability ◽  
Wellbore Pressure ◽  
Stress States ◽  
Deviatoric Stresses ◽  
Wellbore Failure

This study presents a new interface for wellbore stability analysis, which visualizes and quantifies the stress condition around a wellbore at shear and tensile failure. In the first part of this study, the Mohr–Coulomb, Mogi–Coulomb, modified Lade and Drucker–Prager shear failure criteria, and a tensile failure criterion, are applied to compare the differences in the critical wellbore pressure for three basin types with Andersonian stress states. Using traditional wellbore stability window plots, the Mohr–Coulomb criterion consistently gives the narrowest safe mud weight window, while the Drucker–Prager criterion yields the widest window. In the second part of this study, a new type of plot is introduced where the safe drilling window specifies the local magnitude and trajectories of the principal deviatoric stresses for the shear and tensile wellbore failure bounds, as determined by dimensionless variables, the Frac number (F) and the Bi-axial Stress scalar (χ), in combination with failure criteria. The influence of both stress and fracture cages increases with the magnitude of the F values, but reduces with depth. The extensional basin case is more prone to potential wellbore instability induced by circumferential fracture propagation, because fracture cages persists at greater depths than for the compressional and strike-slip basin cases.

scholarly journals EVALUATING ELASTIC-PLASTIC BEHAVIOUR OF ROCK MATERIALS USING HOEK–BROWN FAILURE CRITERION

2012 ◽  
Vol 18 (3) ◽  
pp. 402-407 ◽  
Author(s):  
Hadi Hasanzadehshooiili ◽  
Ali Lakirouhani ◽  
Jurgis Medzvieckas
Keyword(s):  
Failure Criterion ◽  
Yield Criterion ◽  
Failure Criteria ◽  
Flow Rule ◽  
Rock Masses ◽  
Rock Materials ◽  
Failure Initiation ◽  
Plastic Behaviour ◽  
Yield Behaviour ◽  
Stress States

As a matter of fact, the failure criteria only predict failure's initiation in materials. And, in order to predict post-yield behaviour of materials, a much complicated formulation for stress-strain relationship is required, which we know as plasticity theory. For instance, these formulations are developed based on Mohr-Coulomb criterion for soils and Drucker-Prager criterion for concrete. According to a majority of rock mechanics researchers, the empirical and experimental Hoek-Brown failure criterion is one of the well-progressed and suitable criteria, which can efficiently predict the rock failure initiation under different stress states for various types of intact rocks and rock masses. In this article, according to the suggestion by Heok explained in his paper of 1997, this rugged mentioned criterion is considered as a yield criterion and the elastic-perfect plastic behaviour of rock masses is determined using calculating material constitutive matrix's arrays in terms of Hoek-Brown's material constants and mechanical characteristics of rock materials in the general stress space, considering associated flow rule.

scholarly journals Mesoscale Modelling of Concretes Subjected to Triaxial Loadings: Mechanical Properties and Fracture Behaviour

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1099
Author(s):  
Qingqing Chen ◽  
Yuhang Zhang ◽  
Tingting Zhao ◽  
Zhiyong Wang ◽  
Zhihua Wang
Keyword(s):  
Mechanical Properties ◽  
Tensile Stress ◽  
Failure Criterion ◽  
Mesoscale Model ◽  
Fracture Behaviour ◽  
Descent Method ◽  
Triaxial Stress ◽  
Gradient Descent Method ◽  
Stress States ◽  
Shear Failures

The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with good robustness gave reliable and detailed damage evolution processes under different triaxial stress states. The lateral tensile stress significantly influenced the multiaxial mechanical behaviour of the concretes, accelerating the concrete failure. With low lateral pressures or tensile stress, axial cleavage was the main failure mode of the specimens. Furthermore, the concretes presented shear failures under medium lateral pressures. The concretes experienced a transition from brittle fracture to plastic failure under high lateral pressures. The Ottosen parameters were modified by the gradient descent method and then the failure criterion of the concretes in the principal stress space was given. The failure criterion could describe the strength characteristics of concrete materials well by being fitted with experimental data under different triaxial stress states.

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