An experimental and constitutive investigation on the chemo-mechanical behaviour of a clay

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Accurately modeling the mechanical behavior of materials is crucial for numerous engineering applications. The quality of these models depends directly on the accuracy of the constitutive law that defines the stress–strain relation. However, discovering these constitutive material laws remains a significant challenge, in particular when only material deformation data is available. To address this challenge, unsupervised machine learning methods have been proposed to learn the constitutive law from deformati

Amid profound transformations in the global energy landscape, the restructuring of electricity sectors has become a central element of national strategies to accelerate the growing integration of renewable energy sources (RES) into the power system. In parallel, the liberalization of the electricity industry in the 1990s has led to a significant transformation of this sector, rearranging the vertically integrated supply model into a market-regulated system. This has resulted in an increased need for flexibl

The emplacement of magmatic intrusions in the earth’s crust has been investigated for decades. The driving mechanism is the density difference between the fluid and the rock. In the absence of heterogeneities, this difference creates a constant buoyancy force. This buoyancy governs the internal fluid pressure in excess of the background stress (magmatic overpressure) and creates a self-sustained hydraulic fracture (HF). From early on, HF was investigated under a 2D plane-strain assumption, revealing a head-

The majority of the seismic events in the Mediterranean region are hosted in carbonate-bearing rocks at depths representative of the semi-brittle regime. Within this regime, both brittle behavior (i.e. deformation is localized on the fractures and on the faults) and ductile one (i.e. deformation is distributed and accommodated in the rock core) coexist. The influence of this interplay on the nucleation and propagation of seismic events is poorly studied. Up to now, most experimental work has been conducted

This report proposes an overview of the activities and services provided by the library to the School of engineering (STI) in 2014 as well as the STI collection accessible at the Library. It also presents the main projects that will be continued or initiate in 2015.

Determination of the initial detaching volume is one of the major challenges in snow avalanche and debris flow forecast. Soil liquefaction due to loss of cohesion results in landslides, whereas quasi-brittle failure triggers the release of snow avalanches. Induced strain softening is the main cause of failure in both cases. In the recent decades, the finite element method has established as the preferred choice for stability analyses, thanks to the possibility of describing complex geometries, different mat

Experimental data have been collected over a year-long period in a large weighing lysimeter. Natural climatic forcing occurs, except for rainfall which is artificially generated as a given Poisson process at a daily timescale. A constant water table is maintained and excess infiltrated water is discharged through the outlet at the bottom of the lysimeter. Soil water storage and evapotranspiration fluxes (accentuated by a willow tree planted in the lysimeter) were monitored throughout the experiment, so that

Owens second hypothesis [1] states that the surface shear stress induced by the fluid on the stationary sediment on the ground in a particle saltation layer equals the threshold for particle entrainment. Despite the fact that most numerical models describing sediment entrainment and particle mass fluxes in turbulent boundary layer flows make use of Owens second hypothesis, no direct experimental validation of this assumption has been presented to date. We present direct measurements of the fluid shear stres

A model based on the Euler-Bernoulli theory is used to assess the sensitivity of residual stresses in solid oxide fuel cells to the mechanical properties and geometry of the constituents. It considers different cell configurations, characterised by the presence or not of a compensating layer, and a cathode based on either lanthanum strontium manganite (LSM) or lanthanum strontium cobaltite ferrite (LSCF). The implementation of creep in the model provides insights into the parameters that affect the zero-str

Natural ecosystems provide services such as ameliorating the impacts of deleterious human activities on both surface and groundwater. For example, several studies have shown that a healthy riparian ecosystem can reduce the nutrient loading of agricultural wastewater, thus protecting the receiving surface water body. As a result, in order to develop better protection strategies and/or restore natural conditions, there is a growing interest in understanding ecosystem functioning, including feedbacks and nonli

The World is facing major challenges regarding environmental threats, resource constraints and the large unbalance of wealth among developing and developed countries. Energy engineering is at the core of the actions to be undertaken to meet these challenges in a harmonious way within the framework of strong economic constraints. The rational use of energy, materials and capital, as well as an increased use of renewable energy constitute some of the essential ingredients of more sustainable policies. Energy

The importance of Fibre Reinforced Polymers (FRPs) as a material used for civil engineering purposes has grown in the last decade. Especially the introduction of pultrusion at an industrial level as a way to produce big batches of FRP made it possible to offer the advantages – like the high strength-to-weight ratio or the good corrosion resistance – at a reasonable cost. One issue when designing with pultruded FRPs are the connections. Up to now, connections between pultruded FRPs have been designed in the

This study investigates the influence of petroleum hydrocarbons on a microbial community in the vadose zone under field conditions. An artificial hydrocarbon mixture consisting of volatile and semi-volatile compounds similar to jet-fuel was emplaced in a previously uncontaminated vadose zone in nutrient-poor glacial melt water sand. The experiment included monitoring of microbial parameters and CO2 concentrations in soil gas over 3 months in and outside the hydrocarbon vapor plume that formed around the bur

Novel, highly sensitive piezoelectric acoustic sensors based on partially unclamped Pb(Zr-x, Ti1-x)O-3 (PZT) coated cantilever and bridge have been fabricated by silicon micromachining. High sensitivity at low frequencies (5-100 Hz) has been achieved by patterning very narrow slits (3 to 5 mum) around the structures. A typical response of 100 mV Pa-1 and a noise equivalent pressure of 1.6 mPa Hz(1/2) at 20 Hz have been measured using a 10 pF charge amplifier. Stress compensation, dry etching and integration

The overall topic of the investigation was the sepn. of basic proteins by cation exchange displacement chromatog. For this purpose two principal column morphologies were compared for the sepn. of RNase A and a-chymotrypsinogen, two proteins found in the bovine pancreas. These were a column packed with porous particles (Macro-Prep S, 10 mm, 1000 .ANG.) and a monolithic column (UNOTM S1). Both columns are strong cation exchangers, carrying -SO3--groups linked to a hydrophilic polymer support. Poly(diallyl-dim

The herbicide transport and the groundwater vulnerability to pesticide contamination were studied in the alluvial aquifer of the Rhône River Valley near Martigny (Southwest Switzerland). The low clay and organic matter content of the soil, the intensive agricultural use, and the low depth of the groundwater table, lead to an alleged high vulnerability of the groundwater to contamination. Groundwater is used for irrigation, drinking water supply, and industrial purposes; it is of great economic and ecologica

To gain insight into the physical nature of the coupling between mechanical stress and humidity variations, the behaviour of thin wood strips was studied using specially developed apparatus for creep/recovery and relaxation/blotting-out tests in a controlled humidity environment. The load time and the rate of viscoelastic creep were found to have little influence on mechano-sorptive creep. Moreover, creep trajectory curves for specimens with continuous and interrupted humidity cycles indicated divergence fr

We present a fully Hamiltonian and computationally efficient scheme to include the electrostatic effects due to the classical environment in a Car-Parrinello mixed quantum mechanics/mol. mechanics (QM/MM) method. The polarization due to the MM atoms close to the quantum system is described by a Coulombic potential modified at short range. The functional form of this potential has to be chosen carefully in order to obtain the correct interaction properties and to prevent an unphys. escape of the electronic d

For a software system to be perceived as a success, or even just as properly functioning, many quality attributes, besides functionality, need to be at an acceptable level. However, current software development processes focus on the functional aspects of a system to be developed. They hardly help to systematically engineer for quality attributes other than functionality. It is a system`s architecture by which such quality requirements are satisfied. In particular, software components are an incarnation of

This study aimed to model phenomenologically the dynamics of arterial wall remodeling under hypertensive conditions. Sustained hypertension was simulated by a step increase in blood pressure. The arterial wall was considered to be a thick-walled tube made of nonlinear elastic incompressible material. Remodeling rate equations were postulated for the evolution of the geometric dimensions of the hypertensive artery at the zero-stress state, as well as for one of the material constants in the constitutive equa

An experimental and constitutive investigation on the chemo-mechanical behaviour of a clay

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Learning physics-consistent material behavior from dynamic displacements

Modeling, optimization and experimental assessment of transient-induced fatigue in hydraulic machines

Magmatic Intrusions From a Hydraulic Fracture Modeling Perspective

On the stability of carbonate-bearing faults at the brittle-to-ductile transition

Annual Report 2014, School of Engineering (STI) Services and Collections

Mixed strain-displacement finite elements for landslide and avalanche release prediction

Non-stationarity in experimental travel time measured in a lysimeter: theoretical and modeling lessons from a simplified hydrological system

EXPERIMENTAL VALIDATION OF A CONSTANT SURFACE SHEAR STRESS IN PARTICLE SALTATION LAYERS

Sensitivity of Stresses and Failure Mechanisms in SOFCs to the Mechanical Properties and Geometry of the Constitutive Layers

Modelling carbon and nitrogen turnover in variably saturated soils

Engineering faced with the challenging trilemma: energy, environment and economics

Adhesively bonded lap joints of pultruded GFRP shapes

Microbial community response to petroleum hydrocarbon contamination in the unsaturated zone at the experimental field site Vaerlose, Denmark

Piezoelectric Pb(Zr-x,Ti1-x)O-3 thin film cantilever and bridge acoustic sensors for miniaturized photoacoustic gas detectors

Investigation of particle-based and monolithic columns for cation exchange protein displacement chromatography using poly(diallyl-dimethylammonium chloride) as displacer

Regional and local scale pesticide transport in the alluvial plain of the Swiss Rhône River Valley

Transient moisture effects on wood creep

A Hamiltonian electrostatic coupling scheme for hybrid Car-Parrinello molecular dynamics simulations

On Quality Attribute Based Software Engineering

A model for geometric and mechanical adaptation of arteries to sustained hypertension