Now showing 1 - 10 of 46
  • Publication
    Geothermal energy in small countries - laying the foundations for innovative development
    (World Federation of Engineering Organizations, 2011-09-04) ;
    Creation of an environment in which shallow geothermal energy can thrive will require a coherent approach and a high level of collaboration with professionals from countries that have developed technical expertise in the area. Implementation of regulations, standards and guidelines adapted from best practice in countries such as Switzerland, Germany and Sweden, in addition to understanding the mistakes and successes made by these countries, with respect to the development of their geothermal industries, will help small countries such as Ireland to develop a well-regulated market for the technology. This paper outlines and addresses some of the technical, regulatory and certification issues faced particularly by small countries in their efforts to develop a shallow geothermal energy industry, provides examples of best practice with regard to development in countries with established geothermal energy industries and presents proposed solutions to these issues / barriers using the existing situation in Ireland by way of example.
  • Publication
    Characterisation of Quick Clay at Dragvoll, Trondheim, Norway
    (Southeast Asian Geotechnical Society, 2012-12) ; ; ;
    A detailed characterisation of the quick clay underlying the NTNU research site at Dragvoll, Trondheim is presented. The objective of the work is to provide guidance on quick clay parameters to engineers and researchers working with similar clays in Scandinavia and North America. Dragvoll clay is characterised by its high sensitivity and is quick at relatively shallow depth. The material exhibits low undrained shear strength and high compressibility except over a shallow overconsolidated zone. Its properties are similar to other quick clays in the area and are consistent with well know correlations for Norwegian clays. A combination of simple index tests such as water content and Atterberg limits and CPTU testing proved very useful in characterising the material. The material is very sensitive to sampling and laboratory handling. Results of standard and non standard tests, such as piezoball testing, are presented.
  • Publication
    Evaluation of peat strength for stability assessments
    (Thomas Telford Ltd., 2013-04-03) ;
    n this paper guidance is given for the assessment of peat strength for stability assessments based on laboratory undrained simple shear tests. When considering the stability of peat, these tests will yield a conservative estimation of the in situ strength of the peat mass. The study was motivated by recent interest in renewable energy developments in upland peat areas. The results of more than 111 simple shear tests from 16 sites in Ireland, Scotland and the Netherlands were studied. It was found that the strength of peat is strongly influenced by its stress history, and also varies as a function of the water content and degree of decomposition (fibre content). The normally consolidated normalised strength ratio (s u/σ′v) from simple shear tests of peat was found to be approximately 0·4, which is towards the lower bound of previously published data for peat. Comparisons of strengths derived from simple shear and field vane tests showed that the ratio of the strength derived from the two tests was influenced by the degree of decomposition, and that previously published correction factors for field vane strengths are inappropriate. Guidance is given for engineers working on future schemes on upland peat areas.
  • Publication
    Some experience in measuring pore water suction in Dublin glacial till
    Several recent articles and discussions in GIN, by Penman (2002), Thomann et al. (2003), Ridley (2003) and Sellers et al. (2003) highlight the importance of pore water pressure and suctions and in particular the difficulties associated with measuring suction. This article outlines some recent experience in measuring suctions, which were developed in cut slopes in a very stiff glacial till during the Dublin Port Tunnel (DPT) project in Ireland. A particular feature of the project was the execution of a fully instrumented 12m deep trial excavation (Menkiti et al., 2004). Initially some background to the project and to the problem will be given. Then some details of the specification, installation technique and some examples of the measurements obtained will be outlined. Finally some conclusions will be made on the lessons learned and recommendations will be made for future similar applications.
  • Publication
    Developing Geothermal Energy Research Capabilities at University College Dublin
    (Geothermal Association of Ireland, 2011) ;
    Ireland has one of the highest energy dependencies in Europe and as such must adapt quickly to increase renewable energy exploitation levels in order to secure its energy future. A mix of renewable energy technology types (wind, solar, biomass, wave, tidal, geothermal) will be required in order to achieve Ireland’s national renewable energy generation targets. Geothermal (or ground source) energy can have a part to play in this mix. Over the last number of years the School of Civil, Structural & Environmental Engineering in University College Dublin has begun to develop shallow geothermal energy research capabilities in several areas of interest. Early studies involved the investigation of water chemistry and settlement issues at several sites on the Cork docklands. It was concluded that the chemical characteristics of the water contained in the aquifer could hinder the development of open loop geothermal systems in the area, and that settlement may be a potential concern in cases where open loop systems are installed due to the presence of highly compressible alluvium deposits. Subsequent work has involved the development, construction & performance validation of a thermal response testing rig for site thermal characterisation, installation of both domestic and commercial sized energy piles for research purposes and investigation of soil, rock and grout thermal properties using both steady-state and non-steady-state laboratory testing techniques. This paper gives a brief overview of the completed and ongoing work in the School of Civil, Structural & Environmental Engineering.
  • Publication
    Assessment of an MASW technique incorporating discrete particle modelling
    (Environmental & Engineering Geophysical Society, 2008-06) ;
    A Discrete Particle Scheme (DPS) consisting of interacting circular particles is utilised to examine the Multichannel Analysis of Surface Waves (MASW) technique. Synthetic earth models of various complexity are generated using the DPS and analysed by the MASW dispersion and inversion techniques. For normally dispersive cases, dominated by the fundamental mode, the MASW profiles closely match the true synthetic shear wave velocity (Vs) profiles. When tested on a model that contains a low velocity layer, the accuracy is reduced. MASW field tests at a highly uniform site in Norway (Onsøy) and a site with distinctive layer boundaries in Ireland (Ballinasloe) result in highly repeatable profiles of Vs. Resolution of dispersion curves at low frequencies (<10Hz) is a problem at the Ballinasloe test site, which limits the depth of penetration of the technique. MASW inversion results compare excellently with downhole seismic cone tests at the Onsøy test site and reasonably with a seismic refraction survey at the Ballinasloe site.
      2096Scopus© Citations 15
  • Publication
    Characterisation of Norwegian marine clays with combined shear wave velocity and CPTU data
    (NRC Research Press, 2010-07) ;
    A database of research quality CPTU and shear wave velocity information for Norwegian marine clays has been assembled so as to study the small strain stiffness relationships for these materials and to examine the potential use of CPTU and Vs data in combination for the purposes of characterising these soils. Data for sites where high quality block sampling was carried out have mostly been used. Improvements have been suggested to existing correlations between Gmax or Vs and index properties for these soils. Recent research has shown that CPTU qt and especially u2 and Vs can be measured reliably and repeatably and are not operator or equipment dependant. Therefore a new soil classification chart involving Qt and normalised shear wave velocity (Vs1) or Vs1 and Δu/σv0' is presented. Using this chart it is possible to clearly distinguish between clays of different OCR.
      3669Scopus© Citations 58
  • Publication
    Performance of soil nails in Dublin glacial till
    Soil nailing is being used in many projects in glacial tills in Ireland, particularly to provide temporary support to steep slopes. Little design guidance is available for such materials and it is known that application of design procedures developed for other material is conservative. Detailed nail instrumentation and field monitoring during large scale soil nailing works for the Dublin Port tunnel project has been undertaken. It was found that the short-term behaviour of nails was the reverse of that assumed in current design methods. Most load was induced due to drilling and nailing the lift immediately below the nail being monitored, rather than due to excavation induced stress relief. The highest forces were developed in the upper nails, where the largest ground movements occur. This is the reverse of most current design methods where the highest soil-nail bond is assigned to the deepest nails. It would seem that the observed short-term, pre-failure behaviour of nailed slope is governed more by the deformation pattern of the slope rather than by large scale development of failed wedges. Current design procedures should be reviewed. Despite this the trial confirmed that the currently used procedures are highly conservative for Dublin glacial till.
      3109Scopus© Citations 12
  • Publication
    Review of peat strength, peat characterisation and constitutive modelling of peat with reference to landslides
    (Wrocław University of Technology, 2005)
    The correct estimation of the shear strength of the peat subsoil is one of the major aspects of assessing risk of landslip in blanket peat areas. Due to the fibrous structure of the peat, its behaviour during shear is somewhat different from that of mineral soils (e.g. soft clays) and it has been found difficult to obtain reliable values of its shear strength. To estimate the shear strength of the peat, the geotechnical engineer is faced with making use of a several testing techniques, both in the laboratory and in situ, which were actually developed for mineral soils. Whether these techniques are applicable to peat is not clear. The objectives of this note are to review: 1. Available methods of characterising peat. 2. Previous research that has been carried out on estimating the shear strength of peat in Ireland and elsewhere using both laboratory and in situ testing. 3. Efforts that have been made to model peat using advanced numerical modelling. Following the review some recommendations will be made as to which test type is most applicable to peat soils and recommendations will be made for further work.
  • Publication
    Interpretation of In Situ and Laboratory Thermal Measurements Resulting in Accurate Thermogeological Characterisation
    (Taylor & Francis, 2012-09) ;
    Growing worldwide interest in the exploitation of geothermal energy resources has led to a scenario where the technology routinely forms part of building-scale renewable energy feasibility studies. A thorough understanding of site-specific thermogeological parameters is a vital design requirement of such systems and accurate measurement and interpretation of these parameters is necessary in order to inform scientifically rigorous system design. An overview of the theory underlying a number of laboratory and in situ thermal characterization testing methods and the results from a number of testing regimes carried out using the various thermal characterization equipment constructed in University College Dublin are presented. Results from both the laboratory steady-state and non-steady-state thermal analysis systems and the in situ thermal characterization system are shown to provide accurate measurements of soil and rock thermal parameters. In addition, the settlement profiles of a number of the tested materials were investigated in order to gain an in-sight into this potential drawback of exchanging the backfill material placed around electricity cables to optimize thermal transfer efficiency.