Éléments de couplage thermomécanique dans la consolidation de sols non saturés

2000 ◽  
Vol 37 (2) ◽  
pp. 308-317 ◽  
Author(s):  
C Saix ◽  
P Devillers ◽  
M S El Youssoufi
Keyword(s):  
Unsaturated Soils ◽  
Mechanical Characteristics ◽  
Experimental Results ◽  
Silty Sand ◽  
Characteristic Parameters ◽  
Mechanical Coupling ◽  
Thermal Consolidation ◽  
Quantitative Results ◽  
Mechanical Consolidation ◽  
Sols Non Saturés

Thermomechanical couplings in the consolidation of an unsaturated clayey silty sand are investigated. The couplings are analysed through the influence of the temperature (relative to the total vertical stress) on the mechanical characteristics (relative to thermal) of the consolidation. They are evidenced by means of two types of tests (thermal consolidation and mechanical consolidation). The two types of tests lead to quantitative results comparable with regards to characteristic parameters of both types of consolidation. Some elements of interpretation are proposed to integrate all of the experimental results within a framework of thinking resorting to the thermoelastoplastic behaviour of the soil under study and to the thermal and mechanical hardening phenomena.Key words: unsaturated soils, consolidation, thermal, mechanical, coupling, hardening.

Appareil triaxial pour l'étude du comportement thermique dé sols non saturés

1990 ◽  
Vol 27 (1) ◽  
pp. 119-128 ◽  
Author(s):  
C. Saix ◽  
P. Jouanna
Keyword(s):  
Key Words ◽  
Unsaturated Soils ◽  
Saturated Soils ◽  
Clayey Soils ◽  
Triaxial Apparatus ◽  
State Of Stress ◽  
Thermal Consolidation ◽  
Mechanical Consolidation ◽  
Sols Non Saturés

The thermal consolidation of unsaturated soils in a thermo-hydro-mechanical framework is studied in a thermal triaxial apparatus described in the paper. The results of the first tests performed, under a given state of stress, on both silty and clayey soils, show some similarities between purely thermal consolidation and mechanical consolidation on saturated soils. Key words: unsaturated soils, temperature, triaxial, consolidation. [Journal translation]

The Mechanical Characteristics and Sealing Performance Evaluation of Bolted Pipe Flange Connections With Metallic Flat Gaskets Subjected to Internal Pressure

2016 ◽  
Author(s):  
Koji Kondo ◽  
Koji Sato ◽  
Satomi Takahashi ◽  
Toshiyuki Sawa
Keyword(s):  
Plastic Deformation ◽  
Mechanical Characteristics ◽  
Experimental Results ◽  
Leak Rate ◽  
Effect Of Temperature ◽  
Load Factor ◽  
Stress Distributions ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Higher Temperature

Bolted pipe flange connections with metallic gaskets have been used under higher pressure as well as higher temperature. However, a few researches on the mechanical characteristics in connections with metallic gaskets have been carried out. It is necessary to examine the mechanical characteristics such as the contact gasket stress distributions which govern the sealing performance, the deformation of the metallic gaskets, changes in axial bolt forces and the hub stress under higher pressure and temperature. In the present paper, the objectives are to examine the changes in axial bolt forces, the hub stress and the contact gasket stress distributions and the sealing performance of the pipe flange connections with metallic flat gaskets. Firstly, the mechanical characteristics of the connections under higher pressure are analyzed using FEA. Then, experiments were carried out to measure the load factor, the hub stress and the leak rate (the sealing performance). The relationship between the average contact gasket stress and the leak rate was measured using platen device at room temperature. The FEA results are fairly coincided with the experimental results. It is shown that the leak rate decreases as the contact gasket stress increases and when the plastic deformation of gaskets occurs, the sealing performance increases. The leak rate was measured in the range of 10−4∼10−7 [Pa·m3/s]. It is found that the sealing performance increases as the gasket width increase in the elastic deformation range while it is independent of the gasket width when the plastic deformation occurs. The effect of temperature on the mechanical characteristics of the connection is also examined. The FEA results are in a fairly good agreement with the experimental results. It is found that the sealing performance increases as the temperature increases. In addition, a method how to determine the bolt preload for increasing the sealing performance is proposed.

scholarly journals Structural and mechanical characteristics of some lead-free Cu-Sn based solder alloys

2008 ◽  
Vol 62 (3) ◽  
pp. 160-163 ◽  
Author(s):  
Aleksandra Mitovski ◽  
Ljubisa Balanovic ◽  
Dragana Zivkovic ◽  
Sasa Marjanovic ◽  
Bata Marjanovic ◽  
...  
Keyword(s):  
Mechanical Characteristics ◽  
Dendritic Structure ◽  
Production Method ◽  
Experimental Results ◽  
Lead Free ◽  
Solder Alloys ◽  
Slow Cooling ◽  
Mechanical And Electrical Properties ◽  
Additional Thermal Treatment ◽  
Lead Free Solders

The results of structural and mechanical characteristics of lead-free Cu-Sn based solder alloys, produced in Company "11. mart" AD Srebrenica (Republic of Srpska), are presented in this paper. The results of investigation of samples - alloys CuSnl4, CuSnlFelAlO.5, CuSnlOFelAllMnO.5 and CuA110Fe3Mn produced by different processing methods, include the data obtained by optical microscopy and measurements of hardness, micro hardness and electroconductivity, in order to characterize mentioned alloys and define the influence of processing method applied on their structural and mechanical properties. Microstructural experimental results of samples produced by casting in a metal mould with fast water cooling showed clearly sharp dendritic structure. Samples obtained by casting in a sand mould, displayed structure with big crystals, higher amount of segregation and inclusions on the grain boundaries, as a result of the slow cooling process. Hardness and microhardness tests showed increasing values as the amount of tin raised. Sample 3 showed the lowest value, as a result of the crystallization process and lackness of additional thermal treatment. Experimental results of the electroconductivity test showed that mentioned sample has got the highest value, which can be also explained by its production method. Results presented in this paper can contribute to investigations of copper-tin lead-free alloys, having in mind that various potential lead-free solders still haven't been completely investigated from the aspects of their structural, mechanical and electrical properties.

Efficiency of Bio-Sourced Composites in Confining Recycled Aggregates Concrete

2022 ◽  
Author(s):  
Elhem Ghorbel ◽  
Mariem Limaiem
Keyword(s):  
Mechanical Behavior ◽  
Analytical Modeling ◽  
Mechanical Characteristics ◽  
Epoxy Polymer ◽  
Experimental Results ◽  
Confined Concrete ◽  
Recycled Aggregates ◽  
Demolition Waste ◽  
Traditional System ◽  
Flax Fibers

This research investigates the efficiency of using Flax Fibers reinforced bio-sourced polymer by comparison to traditional system based on Carbone Fiber Reinforced Epoxy Polymer in order to confine recycled aggregates concrete. Four concrete formulations have been formulated by incorporating recycled aggregates from demolition waste (0%, 30%, 50% and 100%). An air-entraining agent was added to the formulations to achieve the level of 4% occluded air. The main objective is to discuss and to evaluate the effectiveness of confining them using bio-sourced composite by comparison to traditional ones. To hit this target, the developed approaches are both experimental and analytical. The first part is experimental and aimed to characterize the mechanical behavior of the materials: the composites used in the confining process the unconfined concrete (effect of incorporating recycled aggregates on the overall mechanical characteristics). We establish that bio-sourced composites are efficient in strengthening recycled aggregates concrete especially if they are air-entrained. The second part of this work is dedicated to analytical modeling of mechanical behavior of confined concrete with composite under compression based on Mander’s model. The input parameters of the model were modified to consider the rate of recycled aggregates incorporation. Comparison between experimental results and the modified Mandel’s Model is satisfactory.

Modified State Surface Approach to Study Unsaturated Soil Hysteresis Behavior

2020 ◽  
Vol 2674 (10) ◽  
pp. 484-498
Author(s):  
Beshoy Riad ◽  
Xiong Zhang
Keyword(s):  
Mechanical Behavior ◽  
Unsaturated Soils ◽  
Construction Material ◽  
Constitutive Models ◽  
Experimental Results ◽  
Special Focus ◽  
Surface Approach ◽  
Hysteresis Behavior ◽  
Mechanical Hysteresis ◽  
Hydraulic Hysteresis

Unsaturated soils are often used as a construction material in transportation infrastructures. In this situation, unsaturated soils are subjected to cyclic mechanical loading from traffic loads or wetting-drying cycles in seasonal climatic conditions. While mechanical hysteresis is a common feature of soils in general, hydraulic hysteresis is associated with unsaturated soils. Although several constitutive models for unsaturated soils have been proposed, the mechanical and hydraulic hysteresis behavior of unsaturated soils has been little studied. A modified state surface approach (MSSA) was first proposed for investigating the mechanical behavior of unsaturated soils. It was then extended to study the coupled hydro-mechanical behavior of unsaturated soils with a special focus on the consistency between different soil phases. However, hydraulic and mechanical hysteresis were neglected in MSSA formulations. In this paper, based on evidence from experimental results, the MSSA is extended further to study the coupled hydro-mechanical hysteresis behavior of unsaturated soils. The extended MSSA can reproduce several forms of mechanical and hydraulic behavior observed in experimental results that cannot be represented by existing constitutive models. To demonstrate the capabilities of the extended MSSA, typical behaviors are simulated and compared, qualitatively, with the characteristic trends of the behavior of unsaturated soils. Experimental results from the literature are then used to evaluate the model to predict, quantitatively, the observed behaviors. The agreement between measured and predicted results is considered satisfactory and confirms the possibility of the proposed approach to reproduce the hysteresis behavior of unsaturated soils.

scholarly journals Relationship Among Preparation, Structure and Superconductivity in Ti-Ca-Ba-Cu-O Compounds

1993 ◽  
Vol 15 (3-4) ◽  
pp. 117-138
Author(s):  
I. Kirschner ◽  
S. Leppävuori ◽  
A. Uusimäki
Keyword(s):  
Single Phase ◽  
Substantial Effect ◽  
Experimental Results ◽  
Characteristic Parameters ◽  
Term Stability ◽  
Long Term Stability ◽  
Preparation Conditions ◽  
Superconducting Parameters

Analysis of a comprehensive set of experimental results has proven the substantial effect of the precise preparation conditions upon the structure and superconducting parameters of Ti-Ca-Ba-Cu-O samples. The techniques required for the preparation of specimens of single phase and long-term stability, together with methods for improvement of the characteristic parameters have been determined. Comparing results derived from samples prepared by different methods has allowed the quantitative differences of the characteristic parameters to be evaluated.

A UNIFIED FRACTAL MODEL FOR PERMEABILITY COEFFICIENT OF UNSATURATED SOIL

Fractals ◽  
2019 ◽  
Vol 27 (01) ◽  
pp. 1940012 ◽  
Author(s):  
GAOLIANG TAO ◽  
XIAOKANG WU ◽  
HENGLIN XIAO ◽  
QINGSHENG CHEN ◽  
JIANCHAO CAI
Keyword(s):  
Relative Permeability ◽  
Unsaturated Soil ◽  
Permeability Coefficient ◽  
Unsaturated Soils ◽  
Fractal Theory ◽  
Characteristic Curve ◽  
Fractal Model ◽  
Computational Effort ◽  
Model Parameters ◽  
Mechanical Coupling

Due to the significant challenges in the measurements, evaluation of permeability coefficient for unsaturated soil is of immense importance for investigating the seepage and hydro-mechanical coupling problems of unsaturated soil. However, the predictions of existing typical models reveal significance divergence for permeability coefficient of unsaturated soils even under identical conditions. In particular, the existing models are greatly restricted in their practical application due to their complexity in the form of integral expressions that require significant computational effort. Here, a simplified unified model is presented to estimate the relative permeability coefficient. First, a fractal-form of soil–water characteristic curve (SWCC) is derived from fractal theory. Then, on the basis of the proposed SWCC models, the classical models (i.e. Childs and Collis-George (CCG) model, Burdine model, Mualem model and Tao and Kong model, respectively) for evaluating the permeability coefficient of unsaturated soil are converted to be presented in fractal forms. It is interestingly found that the fractal forms of these models are enormously similar. Based on these observations, a simplified unified fractal model for the relative permeability coefficient of unsaturated soil is proposed, where only two parameters (i.e. fractal dimension and air-entry value) are included, thereby significantly reducing the computational efforts. The detailed procedure for determining model parameters is elaborated. The accuracy of this model is verified by comparing its predictions with the experimental data for over 12 types of unsaturated soils. The results highlight that, compared with existing models, the proposed model would be much more efficiently used for estimating the relative permeability coefficient of unsaturated soils, thereby facilitating its application for investigating the associated seepage and hydro-mechanical coupling problems in practice.

scholarly journals Relative performance of two unsaturated soil models using different constitutive variables

2014 ◽  
Vol 51 (12) ◽  
pp. 1423-1437 ◽  
Author(s):  
Martí Lloret-Cabot ◽  
Simon J. Wheeler ◽  
Jubert A. Pineda ◽  
Daichao Sheng ◽  
Antonio Gens
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Experimental Tests ◽  
Experimental Results ◽  
Degree Of Saturation ◽  
State Variables ◽  
Retention Behaviour ◽  
Model Predictions ◽  
Water Retention Behaviour

Mechanical and water retention behaviour of unsaturated soils is investigated in the context of two well established coupled constitutive models, each of which is formulated in terms of a different set of stress state variables or constitutive variables. Incremental relationships describing the volume change and variation of the degree of saturation are derived for each model. These incremental relationships are used to simulate a set of experimental tests on compacted Speswhite kaolin previously reported in the literature. Six individual tests, involving isotropic compression and various forms of shearing, are analyzed in the context of the incremental forms developed, and the model predictions are then compared against experimental results. The results show that, although each constitutive model uses a different set of constitutive variables and a different scheme for coupling mechanical and water retention behaviour, the two sets of model predictions are similar and both sets provide a reasonable match to the experimental results, suggesting that both models are able to capture the relevant features of unsaturated soil behaviour, despite expressing the constitutive laws in different ways.

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