Design and Performance of Low Capacity Roads on Peat Foundation Soils in Ireland

A new paper co-authored by Ciaran Reilly of Ciaran Reilly & Associates and Fintan Buggy of Roughan & O’Donovan, “Design and Performance of Low Capacity Roads on Peat Foundation Soils in Ireland”, will be presented to the 4th International Conference on Transportation Geotechnics (ICTG2021) next Wednesday. The paper examines four case histories, including a re-examination of the case of Cush Road on the Kildare/Offaly border documented by Prof Eamon Hanrahan for over 26 years and more modern uses of high performance geosynthetics to improve performance of low volume roads on peat soils in Ireland.

The International Conference on Transportation Geotechnics is organised every four years by ISSMGE Technical Committee on Transportation Geotechnics (TC202) and this 4th conference is hosted by the University of Illinois at Urbana-Champaign. The paper will be available from the ISSMGE website after the conference.

N17/R320 Lisduff Junction Upgrade – earthworks check

Ciaran Reilly & Associates has recently been engaged by Barry Transportation to undertake the role of Independent Checking Consultant in accordance with DN-ERW-03083 “Managing Geotechnical Risk” for the N17/R320 Lisduff Junction Upgrade on the N17 national road at Lisduff, Claremorris, Co Mayo. The area had been identified as High Collision Location by TII and this project will replace two at-grade junctions with a new compact grade-separated junction. The proposed works will involve a new bridge over the N17 and approximately 1.2km of link, junction, and local road. We look forward to working with Barry Transportation on this project to help improve road safety in the west of Ireland. (Image: Google Maps).

Satellite image with map of new N17/R320 Lisduff Junction Upgrade road layout

Lime modification at N4 Collooney to Castlebaldwin Road Improvement project

We’re currently working with Oliver Conroy Plant & Agri Hire and Roadbridge on the design and reporting of lime modification of cohesive soils at the N4 Collooney to Castlebaldwin Road Improvement site.

Pulverisation and rolling of lime treated soil

Treatment with lime is allowing unacceptable Class U1 material be processed to acceptable Class 2 general fill, allowing efficient and sustainable reuse of local soil which may have been disposed of as a waste. This process also saves on importation of suitable fill from elsewhere, dramatically reducing road haulage movements and hence disturbance to the local environment. 

Lime modification plant spreading lime and ripping treated soil

7th CEN TC250 SC7 Working Groups meeting in Naples

Dr Ciaran Reilly recently attended the 7th CEN TC250 SC7 Working Groups meeting in Naples on behalf of NSAI to discuss the ongoing work in preparing the next generation of Eurocode 7, the structural Eurocode covering the design of geotechnical structures. The outcome of the process will be a significantly changed and easier to use standard when the new document is released after 2020.

Ciaran is a member of the NSAI mirror committee to SC7. This committee is charged with reviewing and commenting on the revised documents and will prepare the necessary Irish National Annexes to the new Eurocode 7 parts when they are finalised.

The meeting was held in the spectacular Villa Doria d’Angri, part of the Parthenope University of Naples and built on a bench of tuff rock overlooking the Gulf of Naples and Mount Vesuvius.

View of Naples from Villa Doria D'Angri

Assessing geotechnical constraints on the development of Ulster Canal Greenway Phase 2

Last week, we spent two days carrying out a walkover survey of the disused Ulster Canal alignment between Smithborough in Co. Monaghan and Middletown in Co. Armagh with Clandillon Civil Consulting. Our task was to identify and map potential geotechnical and geological constraints to the development of this very interesting 22km cross border greenway project, to feed in to a wider technical scoping study for the project under preparation by Clandillon Civil Consulting. The project is supported by the European Union’s INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB).

The canal alignment is quite overgrown and difficult to access but the views were beautiful and the industrial heritage of this unusually narrow canal is fascinating.

The canal’s original engineers and surveyors chose an optimal route, threading the canal between the local drumlins and moraines. This way, the canal follows the edge of the low-lying alluvial deposits between the drumlins and moraines, minimising the need for locks, while keeping the foundations in the competent glacial deposits at the toe of the adjacent slopes.

Phase 2 of the Ulster Canal Greenway, due to open in 2020, will make a fine addition to Ireland’s growing collection of greenways.

Designs for StoneTerra gravity retaining walls

On Thursday last we visited two sites in County Cork where StoneTerra modular block gravity retaining walls we had carried out design for were under construction. The first site was part of the Bandon Flood Relief Scheme, where a StoneTerra wall was retaining a river bank, and the second site was a new Topaz service station near Fermoy, where the levelling pad was just being installed ahead of the placing of the blocks.



We also visited two sites where geogrid was being used as reinforcement in other StoneTerra structures, allowing for wall heights in excess of that possible using gravity retaining wall design principles.



All four projects were progressing well and we were again impressed with the speed and efficiency of installation possible with the StoneTerra system, as well as the aesthetic finish of the blocks.

Geotechnical Engineering for Ground and Surface Water conference

We were delighted to help organise the recent Geotechnical Society of Ireland/Engineers Ireland conference, “Geotechnical Engineering for Ground and Surface Water”. Twelve very interesting papers were presented in front of an audience of over 120 attendees at the Midlands Park Hotel in Portlaoise. Among the presentations, one of the key points that stood out was the critical role of the geotechnical engineer in the design of flood protection works, with geotechnical engineering works making up the vast majority of the capital spend in any flood protection scheme. The value of geotechnical expertise was stressed throughout.

Ciaran Reilly chaired a session on groundwater modelling, where two very interesting papers on the modelling of regional scale aquifers were presented.

The proceedings of the conference are now available to purchase on the Engineers Ireland website, and would make a valuable reference document for any civil engineering designer or contractor engaged in works involving ground water or flood protection.

No Dig Berlin 2017

The papers presented at No Dig Berlin 2017, the trenchless technology symposium held last March, are available online now. We were delighted to attend a very well organised event and learn of innovations and best practice in the industry. The paper authored by Trevor Orr and Ciaran Reilly on the role of lubricant slurries and effective stress in skin friction reduction in pipe jacking was well received at the symposium, as were all the other papers.

Herrenknecht AG, the tunnelling equipment manufacturer, presented a promising innovation in miniaturisation. They are developing a new small diameter TBM suited for installing significant lengths of HV underground cable to help Germany meet its targets for putting, as we understand it, all new heavy electricity lines from wind farms in the North Sea underground. This is an adaption of the microtunnelling technique with which we are very familiar. We look forward to following the development of this technology and can foresee many applications for this new equipment in UK and Ireland.

Design check of reinforced access road designs for Centre Parcs, Ballymahon

We recently assisted Thrace Synthetic with independent design checks of reinforced soil access roads for the first phase of the 164ha development of the Centre Parcs holiday village in Co. Longford. A set of designs were prepared to deal with a wide variation in ground conditions encountered on the site, with a target CBR of 15% being set at the finished access road surface.

Good construction site practice, high quality materials, and favourable weather conditions led to the target CBR value being consistently exceeded in acceptance testing, with CBR results in excess of 40% frequently being achieved at subformation level in the marginal tills at the site.

Ground investigation in Co. Monaghan

We recently commissioned a ground investigation in Co. Monaghan to support the design of a sports field. There is a deep cut into a slope at one end of the sports field, and using information from the recently-updated Geological Survey of Ireland (GSI) Quaternary Data Viewer we could begin to develop an understanding of the likely geology at desk study stage and make an informed prediction that overburden would extend to a significant depth.  The prediction was correct in this case and drilling encountered overburden of glacial till to the planned investigation depth.

Monaghan ground investigation

The latest GSI Quaternary mapping suggests the site is a drumlinised ribbed moraine. Current knowledge suggests that, in the region of interest, the transition from ribbed moraine (yellow areas in the image below) to drumlin bedform (magenta lines) may be related to ice movement increasing in velocity at this location during deposition. A lot of what we can say about the glacial landscape left behind in warmer places is informed by observations of current glacier movements in colder places, and the paper by Johnson et al. on observations of an active drumlin field in Iceland is a fascinating read on the topic. As with any project which involves an element of ground risk, an understanding of both the geological background of the site and the geotechnical properties of the materials there today is essential to achieving a reliable design.

Screenshot of GSI data plotted in QGIS