Laboratory investigation on the mechanical behaviour of Tournemire argillite

2015 ◽  
Vol 52 (3) ◽  
pp. 268-282 ◽  
Author(s):  
H. Abdi ◽  
D. Labrie ◽  
T.S. Nguyen ◽  
J.D. Barnichon ◽  
G. Su ◽  
...  
Keyword(s):  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Damage Model ◽  
Orientation Angle ◽  
Triaxial Tests ◽  
Experimental Program ◽  
Emission Data ◽  
Testing Program ◽  
Bedding Planes ◽  
Rock Specimens

This paper presents the results of a laboratory testing program that was designed to investigate the mechanical behaviour of the Tournemire argillite. Eighty rock samples were obtained from boreholes drilled at different angles in the walls and floor of an existing gallery at the Tournemire Underground Research Laboratory (URL), France. The experimental program consists of the measurement of the physical properties of the argillite and its mechanical response to loading during uniaxial tests, triaxial tests with various confining pressures, unconfined and confined cyclic tests, and Brazilian tests. Since the Tournemire argillite is characterized by the presence of closely spaced bedding planes, the rock specimens were loaded in different directions to bedding planes (i.e., loading orientation angle, θ = 0°, 30°, 45°, 60°, and 90°). Acoustic emission data were also recorded to detect the initiation and propagation of micro-cracks during the uniaxial tests. Most of the tests were performed at the natural moisture content of the rock specimens as delivered to CANMET Laboratories in Ottawa, Canada, where the experiments were conducted. The main objective of the testing program is to identify the mechanical properties of the Tournemire argillite. This paper mainly focuses on the description and interpretation of the test results. The development of an elastoplastic-damage model to describe the mechanical behaviour of the Tournemire argillite is the subject of another paper.

Experimental behaviour and modelling of an unsaturated compacted soil

2000 ◽  
Vol 37 (4) ◽  
pp. 748-763 ◽  
Author(s):  
Celestino Rampino ◽  
Claudio Mancuso ◽  
Filippo Vinale
Keyword(s):  
Unsaturated Soils ◽  
Mechanical Response ◽  
Stress Path ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Experimental Program ◽  
State Variables ◽  
Soil Response ◽  
Optimum Water Content ◽  
Triaxial Cell

This paper reports the experimental study and modelling of the mechanical response of a silty sand used in the core of the Metramo dam, Italy. Specimens were prepared by compacting the soil at optimum water content conditions using the modified Proctor technique. Tests were performed under suction-controlled conditions by a stress path triaxial cell and an oedometer. The experimental program consists of 23 tests carried out in the suction range of 0-400 kPa. The findings indicate the strong influence of suction on compressibility, stiffness, and shear strength. The mechanical properties of the soil improve with suction following an exponential law with decreasing gradient. Furthermore, the soil exhibited collapsible behaviour upon wetting even at low stress levels. Interesting results were also achieved in elastoplastic modelling as well. The results led to characterization of soil behaviour with reference to widely accepted modelling criteria for unsaturated soils, providing noteworthy suggestions about their applicability for granular materials with a non-negligible fine component. Finally, some remarks are made for the extension under unsaturated conditions of the "Nor sand" model for saturated granular soils. The proposed approach yields improved predictions of deviator soil response of the tested soil when Cambridge-type frameworks prove invalid.Key words: unsaturated soils, stress state variables, triaxial tests, oedometer tests, constitutive model.

Development of a constitutive model for a bedded argillaceous rock from triaxial and true triaxial tests

2015 ◽  
Vol 52 (8) ◽  
pp. 1072-1086 ◽  
Author(s):  
T.S. Nguyen ◽  
A.D. Le
Keyword(s):  
Constitutive Model ◽  
Mechanical Response ◽  
Opalinus Clay ◽  
Triaxial Tests ◽  
Physical Processes ◽  
True Triaxial ◽  
Inherent Anisotropy ◽  
Bedding Planes ◽  
Cylindrical Samples ◽  
True Triaxial Tests

In this work, a constitutive model that predicts the mechanical behaviour of Opalinus clay is developed. The model is based on the theory of plasticity, and takes into consideration the inherent anisotropy due to the existence of bedding planes, hardening behaviour before the peak strength, softening behaviour after the peak, and creep effects. The model was implemented into the equations of pseudostatic equilibrium to simulate the mechanical response of Opalinus clay during conventional triaxial tests (using cylindrical samples) and true triaxial tests (using cubic samples). The model satisfactorily reproduces the main physical processes that prevailed during those tests.

scholarly journals Development of a viscoelastoplastic model for a bedded argillaceous rock from laboratory triaxial tests

2017 ◽  
Vol 54 (3) ◽  
pp. 359-372 ◽  
Author(s):  
Zhenze Li ◽  
Thanh Son Nguyen ◽  
Grant Su ◽  
Denis Labrie ◽  
Jean Dominique Barnichon
Keyword(s):  
Mechanical Behaviour ◽  
Nuclear Safety ◽  
Theoretical Research ◽  
Triaxial Tests ◽  
Radiological Protection ◽  
Creep Tests ◽  
Geological Disposal ◽  
Inherent Anisotropy ◽  
Bedding Planes ◽  
Using Data

Argillaceous rocks are candidate host and (or) cap formations for the geological disposal of nuclear wastes in many countries, including Canada, France, and Switzerland. The understanding of the long-term mechanical behaviour of such rocks is an essential requirement for the assessment of their performance as a barrier against radionuclide migration. The French Institute for Radiological Protection and Nuclear Safety (IRSN) operates an Underground Research Laboratory (URL) in Tournemire, France, in a rock formation known as the Tournemire shale. Many types of experiments are conducted at the Tournemire URL to better understand the physical and chemical behaviour of this shale and its interaction with seal materials intended to be used in the geological disposal of radioactive wastes. The Canadian Nuclear Safety Commission (CNSC) collaborates with the IRSN and CanmetMINING laboratories to perform experimental and theoretical research on the mechanical behaviour of the Tournemire shale. Using data from creep tests, and monotonic and cyclic triaxial tests performed at CanmetMINING Laboratories, we developed constitutive relationships for the mechanical behaviour of the Tournemire shale. The model is based on the theory of plasticity, and takes into consideration the inherent anisotropy due to the existence of bedding planes, hardening behaviour before the peak strength, and viscosity.

scholarly journals Rock Failure Analysis Based on a Coupled Elastoplastic-Logarithmic Damage Model

2017 ◽  
Vol 62 (4) ◽  
pp. 753-774
Author(s):  
M. Abdia ◽  
H. Molladavoodi ◽  
H. Salarirad
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Mechanical Response ◽  
Damage Model ◽  
Yield Function ◽  
Irreversible Thermodynamics ◽  
Stiffness Degradation ◽  
Shear Stresses ◽  
Rock Materials ◽  
Damage Process

Abstract The rock materials surrounding the underground excavations typically demonstrate nonlinear mechanical response and irreversible behavior in particular under high in-situ stress states. The dominant causes of irreversible behavior are plastic flow and damage process. The plastic flow is controlled by the presence of local shear stresses which cause the frictional sliding. During this process, the net number of bonds remains unchanged practically. The overall macroscopic consequence of plastic flow is that the elastic properties (e.g. the stiffness of the material) are insensitive to this type of irreversible change. The main cause of irreversible changes in quasi-brittle materials such as rock is the damage process occurring within the material. From a microscopic viewpoint, damage initiates with the nucleation and growth of microcracks. When the microcracks length reaches a critical value, the coalescence of them occurs and finally, the localized meso-cracks appear. The macroscopic and phenomenological consequence of damage process is stiffness degradation, dilatation and softening response. In this paper, a coupled elastoplastic-logarithmic damage model was used to simulate the irreversible deformations and stiffness degradation of rock materials under loading. In this model, damage evolution & plastic flow rules were formulated in the framework of irreversible thermodynamics principles. To take into account the stiffness degradation and softening on post-peak region, logarithmic damage variable was implemented. Also, a plastic model with Drucker-Prager yield function was used to model plastic strains. Then, an algorithm was proposed to calculate the numerical steps based on the proposed coupled plastic and damage constitutive model. The developed model has been programmed in VC++ environment. Then, it was used as a separate and new constitutive model in DEM code (UDEC). Finally, the experimental Oolitic limestone rock behavior was simulated based on the developed model. The irreversible strains, softening and stiffness degradation were reproduced in the numerical results. Furthermore, the confinement pressure dependency of rock behavior was simulated in according to experimental observations.

Virtual trabecular bone models and their mechanical response

2008 ◽  
Vol 222 (8) ◽  
pp. 1185-1195 ◽  
Author(s):  
F E Donaldson ◽  
P Pankaj ◽  
A H Law ◽  
A H Simpson
Keyword(s):  
Finite Element ◽  
Trabecular Bone ◽  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Elastic Response ◽  
Anatomical Site ◽  
Virtual Samples ◽  
Micro Level ◽  
Architectural Characteristics

The study of the mechanical behaviour of trabecular bone has extensively employed micro-level finite element (μFE) models generated from images of real bone samples. It is now recognized that the key determinants of the mechanical behaviour of bone are related to its micro-architecture. The key indices of micro-architecture, in turn, depend on factors such as age, anatomical site, sex, and degree of osteoporosis. In practice, it is difficult to acquire sufficient samples that encompass these variations. In this preliminary study, a method of generating virtual finite element (FE) samples of trabecular bone is considered. Virtual samples, calibrated to satisfy some of the key micro-architectural characteristics, are generated computationally. The apparent level elastic and post-elastic mechanical behaviour of the generated samples is examined: the elastic mechanical response of these samples is found to compare well with natural trabecular bone studies conducted by previous investigators; the post-elastic response of virtual samples shows that material non-linearities have a much greater effect in comparison with geometrical non-linearity for the bone densities considered. Similar behaviour has been reported by previous studies conducted on real trabecular bone. It is concluded that virtual modelling presents a potentially valuable tool in the study of the mechanical behaviour of trabecular bone and the role of its micro-architecture.

Numerical Investigation of Ductile Fracture in Pipelines Under Complex Loading Using a Phenomenological Damage Model

2021 ◽  
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa
Keyword(s):  
Ductile Fracture ◽  
Mechanical Response ◽  
Numerical Study ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Numerical Procedure ◽  
Complex Loading ◽  
Experimental Tests ◽  
Compact Tension ◽  
Axial Tensile

Abstract This paper presents a numerical study on pipes ductile fracture mechanical response using a phenomenological computational damage model. The damage is controlled by an initiation criterion dependent on the stress triaxiality and the Lode angle parameter, and a post-initiation damage law to eliminate each finite element from the mesh. Experimental tests were carried out to calibrate the elastoplastic response, damage parameters and validate the FEM models. The tested geometries were round bars having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture toughness tests in deeply cracked bending specimens SE(B) and compact tension samples C(T). The calibrated numerical procedure was applied to execute a parametric study in pipes with circumferential surface cracks subjected to tensile and internal pressure loads simultaneously. The effects of the variation of geometric parameters and the load applications on the pipes strain capacity were investigated. The influence of longitudinal misalignment between adjacent pipes was also investigated.

scholarly journals Experimental and FEM Investigation of Cob Walls under Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Enrico Quagliarini ◽  
Gianluca Maracchini
Keyword(s):  
Compressive Strength ◽  
Mechanical Behaviour ◽  
Poisson’S Ratio ◽  
Construction Material ◽  
Strong Dependence ◽  
Environmental Benefits ◽  
Poisson's Ratio ◽  
Experimental Program ◽  
Rammed Earth ◽  
Crack Model

Earth has been used as construction material since prehistoric times, and it is still utilized nowadays in both developed and developing countries. Heritage conservation purposes and its intrinsic environmental benefits have led researchers to investigate the mechanical behaviour of this material. However, while a lot of works concern with rammed earth, CEB, and adobe techniques, very few studies are directed towards cob, which is an alternative to the more diffused rammed earth and adobe in specific geographic conditions. Due to this lack, this paper presents an experimental program aimed at assessing the failure mode and the main mechanical properties of cob earth walls (compressive strength, Young’s modulus, and Poisson’s ratio) through monotonic axial compression tests. Results show that, if compared with CEB, adobe, and rammed earth, cob has the lowest compressive strength, the lowest modulus of elasticity, and Poisson’s ratio. Differences are also found by comparing results with those obtained for other cob techniques, underlining both the high regional variability of cob and the need of performing more research on this topic. A strong dependence of material properties on loading rate and water content seems to exist too. Finally, the ability of a common analytical method used for masonry structures (an FEM macromodelling with a total strain rotating crack model) to represent the mechanical behaviour of cob walls is showed.

scholarly journals Magnetic measurement system of sandy gravel specimens shape during tests in a large triaxial apparatus

2019 ◽  
Vol 92 ◽  
pp. 02004
Author(s):  
Roberta Ventini ◽  
Alessandro Flora ◽  
Stefania Lirer ◽  
Claudio Mancuso
Keyword(s):  
Relative Humidity ◽  
Mechanical Response ◽  
Magnetic Measurement ◽  
Triaxial Tests ◽  
Sandy Gravel ◽  
Partially Saturated ◽  
Triaxial Apparatus ◽  
Large Size ◽  
Size Of Particles ◽  
The University

As well known, rockfill behaviour is strongly influenced by both intrinsic (mineralogy and size of particles, grain shapes, soil grading etc.) and state parameters (relative density, stress state, relative humidity). To investigate their mechanical response to stresses and relative humidity (RH) loadings, a large size triaxial device (H = 410 mm, D = 200 mm) has been developed at the University of Naples Federico II (Italy), including modifications required to impose partially saturated conditions in the specimen by means of the vapour equilibrium technique. In order to evaluate local axial and radial strains and global volumetric strains in partially saturated conditions, a magnetic shape detector device has been designed and installed. The accuracy of this system has been evaluated in some isotropic compression triaxial tests on compacted sandy-gravel specimens. The experimental data clearly show the effectiveness of the magnetic system in the measurement of axial displacements while the measurement in radial direction appear to be strongly affected by the non-linearity of the complex magnetic field generated during the test and requires further checking tests.

scholarly journals An experimental study on flexural strengthening of RC beams using CFRP sheets

2018 ◽  
Vol 7 (4) ◽  
pp. 2075 ◽  
Author(s):  
Yasmin Murad
Keyword(s):  
Flexural Strength ◽  
Orientation Angle ◽  
Longitudinal Axis ◽  
Flexural Behavior ◽  
Experimental Program ◽  
Rc Beams ◽  
Rc Structures ◽  
Flexural Strengthening ◽  
Cfrp Sheets ◽  
Reinforced Polymer

 The use of carbon fiber reinforced polymer (CFRP) sheets is becoming a widely accepted solution for strengthening and repairing rein-forced concrete (RC) structures. To date, the behavior of RC beams, strengthened with 60˚ and 45˚ inclined CFRP sheets, has not clearly explained. An experimental program is proposed in this paper to investigate the flexural behavior of RC beams strengthened with CFRP sheets. CFRP sheets were epoxy bonded to the tension face to enhance the flexural strength of beams inducing different orientation angles of 0˚, 45˚, 60˚ and 90˚ with the beam longitudinal axis. The study shows that strengthening RC beams with CFRP sheets is highly influenced by the orientation angle of the sheets. The orientation angle plays a key role in changing the crack pattern and hence the failure mode. The influence of CFRP sheets was adequate on increasing the flexural strength of RC beams but the ductility of the beams was reduced. The best performance was obtained when strengthening RC beam obliquely using 45˚ inclined CFRP sheets where the specimen experienced additional deflection and strength of 56% and 12% respectively and the reduction in its ductility was the least. It is recom-mended to strengthen RC beams, which are weak in flexure, using 45˚ inclined CFRP sheets.  

Development of the PGT 25 High Efficiency Gas Turbine: Part 3 — Experimental Program and Testing

1984 ◽  
Author(s):  
P. Lacitignola ◽  
E. Valentini
Keyword(s):  
Gas Turbine ◽  
High Efficiency ◽  
Engine Performance ◽  
Experimental Methods ◽  
Experimental Program ◽  
Load Testing ◽  
Testing Program ◽  
Full Load ◽  
Engine Testing ◽  
Turbine Design

This paper presents a review of the engineering testing program related to development of the PGT-25 gas turbine. The experimental methods employed and their capability of providing information for the tuning of the engine and its parts are discussed. Testing has continuously supported turbine design and development; integration of analytical and experimental procedures has proven to be efficient for successful final engine testing. Full load testing, using well developed instrumentation, has made it possible to know actual component behavior and engine performance in steady and transient states, over the entire speed and power range. The reliability of the machine has been assessed through the results of these tests.

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