An Associative and Non-Associative Anisotropic Bounding Surface Model for Clay

2012 ◽  
Vol 79 (3) ◽  
Author(s):  
Jianhong Jiang ◽  
Hoe I. Ling ◽  
Victor N. Kaliakin
Keyword(s):  
Mechanical Behavior ◽  
Strain Hardening ◽  
Strain Softening ◽  
Surface Model ◽  
Flow Rule ◽  
Reasonable Accuracy ◽  
Bounding Surface ◽  
Softening Behavior ◽  
Different Types ◽  
Undrained Behavior

An anisotropic elastoplastic bounding surface model with non-associative flow rule is developed for simulating the mechanical behavior of different types of clays. The non-associative flow rule allows for the simulation of not only strain-hardening but also strain-softening response. The theoretical framework of the model is given, followed by the verification of the model as applied to the experimental results of a strain-hardening Kaolin tested under different undrained stress paths. The undrained behavior of Boston Blue clay, which exhibits a strain-softening behavior, is also simulated. It is shown that the non-associative nature of the model gives more accurate results than those of the same model employing an associative flow rule, especially for normally consolidated Kaolin specimens. The results show that the model is also capable of simulating the strain-softening behavior of Boston blue clay with reasonable accuracy.

scholarly journals A Proposed Algorithm to Compute the Stress-Strain Plastic Region and Displacement of a Deep-Lying Tunnel Considering Intermediate Stress and Strain-Softening Behavior

2021 ◽  
Vol 12 (1) ◽  
pp. 85
Author(s):  
Jinwang Li ◽  
Xiufeng He ◽  
Caihua Shen ◽  
Xiangtian Zheng
Keyword(s):  
Principal Stress ◽  
Radial Displacement ◽  
Strain Softening ◽  
Plastic Region ◽  
Intermediate Principal Stress ◽  
Surrounding Rock ◽  
Parameter Analysis ◽  
Flow Rule ◽  
Stress Strain ◽  
Softening Behavior

Past studies on deep-lying tunnels under the assumption of plane strain have generally neglected the influence of intermediate principal stress even though this affects the surrounding rocks in the plastic zone. This study proposes a finite difference method to compute the stress strain plastic region and displacement of a tunnel based on the Drucker–Prager (D–P) yield criterion and non-associated flow rule and considering the influences of intermediate principal stress and the strain-softening behavior of surrounding rock. The computed results were compared with those of other well-known solutions and the accuracy and validity of the method were confirmed through some examples. Parameter analysis was conducted to investigate the effects of intermediate principal stress on stress-strain, the plastic region, the ground response curve, and the dilatability of surrounding rock. The results showed that the plastic radius , the residual radius , and radial displacement of surrounding rock first decreased and then increased with increasing intermediate principal stress coefficient b from 0 to 1, with the minimums occurring at b = 0.75. On the contrary, the peak and rate of variation of the dilatancy coefficient first increased and then decreased with increasing b and the dilatancy coefficient gradually transitioned from nonlinear to linear variation. Meanwhile, the inhibition of the plastic radius and radial displacement gradually weakened with increasing support pressure, whereas the dilatancy coefficient of the tunnel opening gradually increased.

scholarly journals The Elastoplastic Solutions of Deep Buried Roadway Based on the Generalized 3D Hoek-Brown Strength Criterion considering Strain-Softening Properties

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Rui Wang ◽  
Jian-biao Bai ◽  
Shuai Yan ◽  
Zhi-guo Chang ◽  
Yuan-ba Song ◽  
...  
Keyword(s):  
Strain Softening ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Theoretical Research ◽  
Flow Rule ◽  
Softening Behavior ◽  
Deep Underground ◽  
Elastoplastic Solutions

The deep underground roadways are widely used in the mining industries at present, but the relevant theoretical bases are not fully understood. In this paper, the numerical solutions for strain-softening surrounding rock under the generalized three-dimensional (3D) Hoek-Brown (GZZ) strength criterion are developed incorporating the confinement-dependent characteristics of ψ and η ∗ and their influences on the stress and displacement of equivalent circular roadway. On the basic of a finite difference, method for the strain-softening model is proposed to consider the variation of ψ and η ∗ in analyzing the strain-softening behavior of rock masses. Combining the equilibrium equation and strength criterion, the stress conditions for each annulus are calculated analytically. The displacement for each step is obtained analytically by solving the differential equation through invoking flow rule and Hooke’s law. The accuracy of the proposed method is verified through the comparison between the results and the previous studies. The effect of intermediate principal stress of GZZ strength criterion is considered; the rationality of the proposed method is verified by two aspects. First, by comparing with the two-dimensional narrow and generalized H-B strength criterion, the advantage of GZZ strength criterion that considers the effect intermediate main stress is highlighted. On the other hand, compared with the three-dimensional linear D-P criterion, the advantage of GZZ strength criterion in the theoretical research of deep underground roadway in coal mine is highlighted. The results show that the strain-softening of the surrounding rock in the plastic zone of the roadway can reduce the pressure of the surrounding rock, but it will greatly increase its deformation. In the high field stress areas, the strain-softening of surrounding rock is the key reason for the destruction of the roadway. It is suggested that in the design and calculation of the support system of the roadway, the strain-softening characteristics of the surrounding rock should be considered, which is very important to avoid large deformation and damage of roadway.

scholarly journals SIMULATING THE BEHAVIOR OF SOFT COHESIVE SOILS USING THE GENERALIZED BOUNDING SURFACE MODEL

2019 ◽  
Vol 15 (3) ◽  
pp. 55-76
Author(s):  
Victor Kaliakin ◽  
Andres Nieto-Leal
Keyword(s):  
Computational Cost ◽  
Constitutive Models ◽  
Surface Model ◽  
Flow Rule ◽  
Cohesive Soils ◽  
Bounding Surface ◽  
True Triaxial ◽  
Dependent Model ◽  
Complex Forms ◽  
Temperature Dependent Model

The Generalized Bounding Surface Model (GBSM) for saturated cohesive soils is a fully three­dimensional, time and temperature-dependent model that accounts for both inherent and stress induced anisotropy. To better simulate the behavior of cohesive soils exhibiting softening, the model employs a non­associative flow rule. The GBSM synthesizes many previous bounding surface constitutive models for saturated cohesive soils and improves upon their predictive capabilities. For those cases where the use of the more complex forms of the GBSM is not justified, the model can be adaptively changed to simpler forms, thus reducing the number of associated parameters, giving flexibility to the simulations and reducing the computational cost. Following a brief overview of the GBSM, the model's performance in simulating the response of soft, saturated cohesive soils is assessed under both axisymmetric and true triaxial conditions.

scholarly journals Compaction of Cohesive Granular Material: Application to Carbon Paste

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 704
Author(s):  
Zahraa Kansoun ◽  
Hicham Chaouki ◽  
Donald Picard ◽  
Julien Lauzon-Gauthier ◽  
Houshang Alamdari ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Mechanical Behavior ◽  
Aluminum Industry ◽  
Frequency Effect ◽  
Strain Rates ◽  
Cyclic Tests ◽  
Carbon Paste ◽  
Rheological Models ◽  
Softening Behavior ◽  
The Aluminum Industry

Carbon-like materials such as the anode and the ramming paste play a crucial role in the efficiency of the Hall–Héroult process. The mechanical behavior of these materials during forming processes is complex and still ill-understood. This work aimed to investigate experimentally the mechanical behavior of a carbon paste used in the aluminum industry under different loading conditions. For this purpose, experiments consisting of (1) relaxation tests at different compaction levels, (2) quasi-static cyclic tests at several amplitudes, (3) monotonic compaction tests at varied strain rates, and (4) vibrocompaction tests at different frequencies were carried out. The obtained results highlight some fundamental aspects of the carbon paste behavior such as the strain rate’s effect on the paste compressibility, the hardening-softening behavior under cyclic loadings, the effect of cycling amplitude on the stress state and the paste densification, and the frequency effect on the vibrocompaction process. These results pave the way for the development of reliable rheological models for the modeling and the numerical simulation of carbon pastes forming processes.

Color-blindness simulation for red-green and blue-yellow ambiguity

2021 ◽  
pp. 1-12
Author(s):  
Sheida Anbari ◽  
Hamid Reza Hamidi ◽  
Shokoh Kermanshahani
Keyword(s):  
Color Vision ◽  
Color Perception ◽  
Color Blindness ◽  
Daily Activities ◽  
Reasonable Accuracy ◽  
Simulation Performance ◽  
Normal Color Vision ◽  
Test Kit ◽  
Different Types ◽  
Color Vision Test

Color blindness has important effects on people’s daily activities, since most activities require a discernment between colors. It is very important for engineers and designers to understand how colorblind people perceive colors. Therefore, many methods have been proposed to simulate color perception of people affected by Dichromacy and anomalous Trichromacy. However, the simulation results rarely have been evaluated with the reports of concerned individuals. In first study, we tried to simulate the color perception of people with different types (red and green) and different degrees of color blindness. Different degrees of red-green deficiency is simulated on the 24-plates brand of the Ishihara color vision test kit. Then simulated plates were tested on people with normal color vision. The results show that the simulation performance is better in the case of high degrees of red-green deficiency. There is also a clear difference between the assessment of female and male volunteers. In another study, the perception of the color of people with blue-yellow blindness is also considered. The proposed blue-yellow blind simulation is compared with the result of another research project. The results show that the color perception of individuals with different degrees of blue-yellow blindness can be reconstructed with a reasonable accuracy.

Numerical solutions for strain-softening surrounding rock under three-dimensional principal stress condition

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sheng Yu-ming ◽  
Li Chao ◽  
Xia Ming-yao ◽  
Zou Jin-feng
Keyword(s):  
Finite Element ◽  
Principal Stress ◽  
Stress Condition ◽  
Strain Softening ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Strength Criterion ◽  
Surrounding Rock ◽  
Flow Rule ◽  
Finite Element Software

Abstract In this study, elastoplastic model for the surrounding rock of axisymmetric circular tunnel is investigated under three-dimensional (3D) principal stress states. Novel numerical solutions for strain-softening surrounding rock were first proposed based on the modified 3D Hoek–Brown criterion and the associated flow rule. Under a 3D axisymmetric coordinate system, the distributions for stresses and displacement can be effectively determined on the basis of the redeveloped stress increment approach. The modified 3D Hoek–Brown strength criterion is also embedded into finite element software to characterize the yielding state of surrounding rock based on the modified yield surface and stress renewal algorithm. The Euler implicit constitutive integral algorithm and the consistent tangent stiffness matrix are reconstructed in terms of the 3D Hoek–Brown strength criterion. Therefore, the numerical solutions and finite element method (FEM) models for the deep buried tunnel under 3D principal stress condition are presented, so that the stability analysis of surrounding rock can be conducted in a direct and convenient way. The reliability of the proposed solutions was verified by comparison of the principal stresses obtained by the developed numerical approach and FEM model. From a practical point of view, the proposed approach can also be applied for the determination of ground response curve of the tunnel, which shows a satisfying accuracy compared with the measuring data.

scholarly journals The Effects of Roadside Woody Vegetation on the Surface Temperature of Cycle Paths

Land ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 483
Author(s):  
Nikola Žižlavská ◽  
Tomáš Mikita ◽  
Zdeněk Patočka
Keyword(s):  
Solar Radiation ◽  
Surface Temperature ◽  
Well Being ◽  
Road Surface ◽  
Woody Vegetation ◽  
Surface Model ◽  
Main Hypothesis ◽  
Roadside Vegetation ◽  
Different Types ◽  
Aerial Vehicle

The article is on the effects of woody vegetation growing on the roadside on the temperature of the surface of cycle paths. The main hypothesis of the study is that vegetation has the effect of lowering the temperature of the surroundings in its shadow and thus improves the comfort of users of cycle paths in the summer months. The second hypothesis is to find out which type of road surface is most suitable for the thermal well-being of users. This goal was achieved by measuring the temperature of selected locations on cycle paths with different types of construction surfaces with nearby woody vegetation using a contactless thermometer over several days at regular intervals. The positions of the selected locations were measured using GNSS and the whole locality of interest was photographed using an unmanned aerial vehicle (UAV), or drone, and subsequently a digital surface model (DSM) of the area was created using a Structure from Motion (SfM) algorithm. This model served for the calculation of incident solar radiation during the selected days using the Solar Area Graphics tool with ArcGIS software. Subsequently, the effect of the shade of the surrounding vegetation on the temperature during the day was analysed and statistically evaluated. The results are presented in many graphs and their interpretation used to evaluate the effects of nearby woody vegetation and the type of road surface on the surrounding air temperature and the comfort of users of these routes. The results demonstrate the benefits of using UAVs for the purpose of modelling the course of solar radiation during the day, showing the effect of roadside vegetation on reducing the surface temperature of the earth’s surface and thus confirming the need for planting and maintaining such vegetation.

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