Coupling of flow, contact mechanics and friction, generating waves in a fractured porous medium

We present a mixed dimensional model for a fractured poro-elasic medium including contact mechanics. The fracture is a lower dimensional surface embedded in a bulk poro-elastic matrix. The flow equation on the fracture is a Darcy type model that follows the cubic law for permeability. The bulk poro-elasticity is governed by fully dynamic Biot equations. The resulting model is a mixed dimensional type where the fracture flow on a surface is coupled to a bulk flow and geomechanics model. The particularity of the work here is in considering fully dynamic Biot equation, that is, including an inertia term, and the contact mechanics including friction for the fracture surface. We prove the well-posedness of the continuous model

Perspectives on European Earthquake Engineering and Seismology: Volume 2

Geotechnical Engineering & Applied Earth Science

Pressure Systems Energy Release Protection (Gas Pressurized Systems)

A survey of studies into hazards associated with closed or pressurized system rupture and preliminary guidelines for the performance design of primary, secondary, and protective receptors of these hazards are provided. The hazards discussed in the survey are: blast, fragments, ground motion, heat radiation, biological, and chemical. Performance guidelines for receptors are limited to pressurized systems that contain inert gas. The performance guidelines for protection against the remaining unaddressed degenerative hazards are to be covered in another study

Mixed approach for coupled flow and mechanics in a fractured medium

Denne avhandlingen presenterer en blandet endelig element metode for Biot ligningene for poroelastisitet i et reservoar, sammenkoblet med en blandet formulering av strømning innenfor en sprekk. Sprekken er representert som et flatt objekt av en dimensjon mindre enn domenet til reservoaret. Den romlige diskretiseringen kombinerer en flerpunkts spenning blandet endelig element (MSMFE) metode for elastisitet og en flerpunkts fluks blandet endelig element (MFMFE) metode for Darcy-strømningen innenfor reservoarmatrisen, sammenkoblet med en MFMFE-metode for strømningen innenfor sprekken. I reservoarmatrisen tar vi i betraktning laveste grad Brezzi-Douglas-Marini blandede endelig elementrom for poroelastisk spenning og Darcy-strømning, og stykkevis konstant forskyvning, trykk og rotasjon. Innenfor sprekken betrakter vi de endelige rommene av sprekk-trykket og fluksen til å være to kompatible par, sammen med konstant mørtelforskyvning. En stabilitetsanalyse utføres både for det kontinuerlige og semi-diskrete problemet. Videre vises eksistens og entydighet for de semi-diskrete og fullt-diskrete løsningene. Ulike numeriske simulasjoner er presentert på slutten.Masteroppgave i anvendt og beregningsorientert matematikkMAB399MAMN-MA

Numerical modelling of earthquake induced liquefaction under irregular and multi-directional loading

This PhD thesis details the numerical investigation of earthquake-induced liquefaction using state-of-the-art research tools implemented in the in-house Imperial College Finite Element Program (ICFEP). The study draws particular emphasis on the role of the multi-directional and irregular nature of the seismic motion on liquefaction, aiming to enable better risk characterisation in engineering practice. The first part focusses on the role of the vertical seismic motion on sand liquefaction, which is largely neglected in design standards. The major contribution relates to a novel concept of liquefaction triggering due to the vertical ground motion, the impact of which was catastrophic during the 2010-2011 Canterbury Earthquake Sequence in New Zealand. Energy principles are adopted in P-wave propagation to aid the interpretation of the physical mechanism. The performance of two time-integration schemes are also compared to provide guidance on numerical geotechnical earthquake engineering problems involving compressional waves. The second part concerns suggested modifications to the constitutive model for sand to mitigate limitations identified in the first part in terms of the simulated undrained cyclic strength. The modified formulation is presented and calibrated based on published element testing and its performance is thoroughly assessed. The third part investigates the applicability of the Palmgren-Miner hypothesis in liquefaction evaluation through the equivalent number of stress cycles concept. The latter is directly applicable to the magnitude scaling factors used in liquefaction assessments, but also to the laboratory evaluated cyclic strength. A procedure to test this numerically is outlined. Based on the conclusions, guidelines for improved use are discussed. The final part of this thesis models a case study. The Mw 6.2 22nd February 2011 Christchurch seismic event in New Zealand was chosen for the analyses, as it presents a well-documented case. A thorough discussion on the inferred geotechnical parameters and on the calibration of the constitutive models is made. The selection of representative input ground motions is also presented in detail. The numerical predictions are compared against the monitoring and field data, but also against the predictions of the simplified liquefaction procedure.Open Acces

Georisks in the Mediterranean and their mitigation

An international scientific conference organised by the Seismic Monitoring and Research Unit, Department of Geoscience, Faculty of Science, Department of Civil and Structural Engineering and Department of Construction and Property Management, Faculty of the Built Environment, University of Malta.Part of the SIMIT project: Integrated civil protection system for the Italo-Maltese cross-border area. Italia-Malta Programme – Cohesion Policy 2007-2013This conference is one of the activities organised within the SIMIT strategic project (Integrated Cross-Border Italo-Maltese System of Civil Protection), Italia-Malta Operational Programme 2007 – 2013. SIMIT aims to establish a system of collaboration in Civil Protection procedures and data management between Sicilian and Maltese partners, so as to guarantee the safety and protection of the citizens and infrastructure of the cross-border area. It is led by the Department of Civil Protection of the Sicilian region, and has as other partners the Department of Civil Protection of Malta and the Universities of Palermo, Catania and Malta. SIMIT was launched in March 2013, and will come to a close in October 2015. Ever since the initial formulation of the project, it has been recognised that a state of national preparedness and correct strategies in the face of natural hazards cannot be truly effective without a sound scientific knowledge of the hazards and related risks. The University of Malta, together with colleagues from other Universities in the project, has been contributing mostly to the gathering and application of scientific knowledge, both in earthquake hazard as well as in building vulnerability. The issue of seismic hazard in the cross-border region has been identified as deserving foremost importance. South-East Sicily in particular has suffered on more than one occasion the effects of large devastating earthquakes. Malta, although fortunately more removed from the sources of such large earthquakes, has not been completely spared of their damaging effects. The drastic increase in the building density over recent decades has raised the level of awareness and concern of citizens and authorities about our vulnerability. These considerations have spurred scientists from the cross-border region to work together towards a deeper understanding of the underlying causes and nature of seismic and associated hazards, such as landslide and tsunami. The SIMIT project has provided us with the means of improving earthquake surveillance and analysis in the Sicily Channel and further afield in the Mediterranean, as well as with facilities to study the behaviour of our rocks and buildings during earthquake shaking. The role of the civil engineering community in this endeavour cannot be overstated, and this is reflected in the incorporation, from the beginning, of the civil engineering component in the SIMIT project. Constructing safer buildings is now accepted to be the major option towards human loss mitigation during strong earthquakes, and this project has provided us with a welcome opportunity for interaction between the two disciplines. Finally the role of the Civil Protection authorities must occupy a central position, as we recognize the importance of their prevention, coordination and intervention efforts, aided by the input of the scientific community. This conference brings together a diversity of geoscientists and engineers whose collaboration is the only way forward to tackling issues and strategies for risk mitigation. Moreover we welcome the contribution of participants from farther afield than the Central Mediterranean, so that their varied experience may enhance our efforts. We are proud to host the conference in the historic city of Valletta, in the heart of the Mediterranean, which also serves as a constant reminder of the responsibility of all regions to protect and conserve our collective heritage.peer-reviewe

Modelling of Harbour and Coastal Structures

As the most heavily populated areas in the world, coastal zones host the majority and some of the most important human settlements, infrastructures and economic activities. Harbour and coastal structures are essential to the above, facilitating the transport of people and goods through ports, and protecting low-lying areas against flooding and erosion. While these structures were previously based on relatively rigid concepts about service life, at present, the design—or the upgrading—of these structures should effectively proof them against future pressures, enhancing their resilience and long-term sustainability. This Special Issue brings together a versatile collection of articles on the modelling of harbour and coastal structures, covering a wide array of topics on the design of such structures through a study of their interactions with waves and coastal morphology, as well as their role in coastal protection and harbour design in present and future climates

Modeling and simulation in tribology across scales: An overview

This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano- and micro-scales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions