Completed Projects

PhD student:    Alan Duggan          Start and finish dates:    09/11 - 07/16

Funding:    NUI Galway (College of Engineering and Informatics Scholarship) - €68,000

External Examiner:   Prof. Ian Jefferson, University of Birmingham

Summary:   Disturbance to and/or lowering of the groundwater table in peatlands, brought about by excavate-and-replace methods during highway construction, can result in significant release of CO₂ to the atmosphere. Through both closed chamber testing and the use of various carbonation depth assessment techniques, this research has demonstrated that stabilised peat acts as a net carbon sink, with a more environmentally-friendly on-site impact than excavate-and-replace strategies. A (cradle-to-gate) Life Cycle Assessment was performed to appraise various ground improvement/foundation options (including stabilisation, using the new research findings) for the construction of a 2 km section of the M6 motorway, near Ballinasloe, Ireland. The LCA demonstrated that soil stabilisation, using a high percentage of GGBS in the binder, offered the lowest Embodied Carbon of the options considered.

PhD student:    Martin Timoney          Start and finish dates:    09/09 - 01/15

Funding:    Irish Research Council for Science and Engineering Technology (IRCSET) - €72,000,    Keller Foundations UK - €12,000

External Examiner:   Prof. Helen Ahnberg, Swedish Geotechnical Institute

Summary:    Deep Dry Soil Mixing is becoming increasingly popular internationally. In situ verification of the stabilised strengths is generally considered necessary, and the tests commonly recommended are the Pull-Out Resistance Test (PORT) and Push-In Resistance Test (PIRT). Guidance on the bearing factor required for interpreting stabilised strengths from PORT and PIRT results is largely based on Scandanavian experience, somewhat limiting international confidence in the method. This research entailed novel reduced-scale PORT and PIRT testing of a cement-stabilised silt/clay under controlled laboratory conditions, with a view to deriving appropriate bearing factors and an understanding of the factors on which they depend.

PhD student:    Brian Sexton          Start and finish dates:   10/10 - 10/14

Funding:    Irish Research Council for Science and Engineering Technology (IRCSET) - €72,000

External Examiner:   Prof. Michael Hicks, Delft University of Technology

Summary:    The ability of stone columns to arrest primary settlement in soft soils has been studied both analytically and numerically. However, the impact of stone columns on creep settlements has received scant attention to date, and designers tend to apply the same settlement improvement factor to creep settlements as calculated for primary settlements. In this research, various isotache soil models incorporating creep were used in conjunction with unit cell analyses implemented in PLAXIS 2D finite element software to ascertain the extent of the reduction to creep settlements offered by stone columns, and the mechanisms dictating this response.  

PhD student:    Brian Sheil          Start and finish dates:    10/10 - 10/14

Funding:    NUI Galway (College of Engineering and Informatics Fellowship) - €68,000

External Examiner:     Dr. Michael Brown, University of Dundee

Summary:    Using PLAXIS 3D finite element analysis and analytical modelling, various factors affecting friction pile group behaviour in clay were studied in this research, including soil stiffness non-linearity, reinforcing effects of neighbouring piles, pile installation and pre-failure pile-soil slip. 

PhD student:    Kevin Flynn          Start and finish dates:    08/10 - 06/14

Funding:    Keller Foundations UK - €50,000 in kind,  NUI Galway (College of Engineering and Informatics Fellowship) - €48,000,  Galway University Foundation - €20,000

External Examiner:    Prof. Barry Lehane, University of Western Australia

Summary:   The results of instrumented DCIS pile tests carried out at five sites in the U.K. (in sand and mixed ground conditions) were used to provide new insights into the shaft and base behaviour of this ‘hybrid’ pile type. In addition, detailed statistical treatment of a new database of DCIS pile data has enabled the suitability of design methods for standard driven piles to be appraised. 

PhD student:    Micheál Killeen          Start and finish dates:    09/07 - 06/12

Funding:    Irish Research Council for Science and Engineering Technology (IRCSET) - €72,000

External Examiner:    Prof. David Richards, University of Southampton

Summary:   This numerical research, using PLAXIS 3-D Foundation, examined differences between stone columns modelled as a unit cell (i.e. infinite grids) and in small discrete groups as typically used to support foundations on soft clay. The effects of geometric factors (such as length, diameter, spacing and position beneath the footing) on settlement improvement factor were examined systematically and were linked to the underlying mechanisms (bulging, individual punching and block failure).

MEngSc student:    Eugene Baily        Start and finish dates:   06/13 - 12/16

Funding:    Shell Exploration and Production Ireland Limited - €25,000, Irish Research Council Postgraduate Scholarship - €45,750.

External Examiner:   Dr. Tomás O'Flaherty, Institute of Technology, Sligo

Summary:    In this research, data from instrumentation incorporated in the retaining walls of the launch and reception shafts of the Corrib Gas Tunnel, Co. Mayo were interpreted. Both shafts were equipped with inclinometers and shape accel arrays on sheet pile walls, while the secant pile wall in the reception shaft was equipped with vibrating wire strain gauges. The measurements were compared with the output from finite element modelling.

MEngSc student:    Eanna McKeon          Start and finish dates:   02/13 - 04/15

Funding:    Aidan O'Connell and Associates - €17,000

External Examiner:   Prof. Cyril Lynsdale, University of Sheffield

Summary:    Damage to domestic dwellings in the greater-Dublin area, owing to the presence of pyrite in underfloor fill material, has prompted a national crisis in recent years. A novel physical model was developed in which the vertical profile of underfloor materials representative of Irish construction practice (including an aggressive pyrite-bearing mudstone fill) was reproduced at full scale. Fill expansion rates and pressures were measured, and the expansion rates were used to assess likely time to manifestation of damage. Factors affecting the expansion process (temperature, density, external water supply) were considered in a companion series of pipe experiments.

MEngSc student:    Brien Curran         Start and finish dates:   09/09 - 12/11

Funding:    Ward and Burke Construction Limited - €40,000

External Examiner:   Prof. David Chapman, University of Birmingham

Summary:    In this research, jacking force and penetration rate data were interrogated for microtunnelling drives in a variety of Irish soil and rock conditions, with a view to establishing face pressures, pipe-soil frictional resistances and the effect of lubrication and stoppages. In addition, settlement profiles were interpreted leading to the first Irish guidance for estimating settlements over tunnels in glacial tills.