Project summary
The Dunkettle interchange, just east of Cork City in Ireland, is an important connection point for local traffic and the national highway system. It has also become infamous across the country for its congestion.
To improve the interchange’s capacity and reduce the disruption it causes, the central roundabout is being replaced with a series of link roads. These roads, however, would need to pass over reclaimed land next to the River Lee that has never been built on before.
Objective:
A geotechnical monitoring system was needed to provide the necessary data to safely build the link roads. Once in place, the system would be used to provide data for three years. During this time, the data would be gathered by Jacobs and sent to a third party for analysis.
There was no existing geotechnical information about the reclaimed land, therefore the solution needed to be flexible enough to be easily modified as new information became available.
A combination of extensometers, inclinometers, piezometers, hydrostatic profile gauges and settlement plates were used for stability monitoring. Readings were recorded both manually and automatically, depending on the instrument. Piezometer data was stored on DT2055B Data Loggers to be manually downloaded via USB once a week. This solution was simple enough that John Sisk & Son could take accurate readings to provide specialists with useful data. In particular, the ability to create templates to guide the data collection process facilitated the handover of data collection responsibilities.
The challenges:
With no existing geotechnical data about the area, the client needed a solution that could be easily adapted to unexpected circumstances.
The monitoring system needed to be simple enough to be used by non-specialists for long-term data collection.
Our work:
Boreholes were drilled for a combination of extensometers, inclinometers, and piezometers. These boreholes were fully grouted. Baseline measurements were obtained on all instruments.
The ground stability measurement system was simple enough to be taken over by non-specialist teams. Murphy Geospatial was able to provide the client with new equipment at short notice as the needs of the operation changed.
Data collection for the north side of the site has been successfully handed over to Jacobs. The data produced by the system is being used to refine the soil models used by the developers and inform the implementation of data collection on the site’s south side.
Our team:
Installed and baselined all instrumentation on the site, working closely with the designer and client to arrange the handover once all instruments were installed as listed below.
Instrumentation
Magnetic extensometers
Inclinometers
Vibrating wire piezometers
DT2055B 5 channel loggers
Hydrostatic profile gauge
Settlement plates
Results:
Data collection for the north side of the site has been successfully handed off to the Jacobs. The data produced by the system is being used to refine the soil models used by the developers and inform the implementation of data collection on the site’s south side.
Testimonial
“I found the Murphy Geospatial team very good and knowledgeable. Materials were always on hand, and they kept with the programme, leading to no lost time.
They were exceptional at showing the young (Sisk) engineers how to collect the data from the various instrumentations to be then able to compile and have it in a format for the DSR to review.
The service provided was excellent, if there were any issues, I just needed to pick up the phone to Eddie, and if he couldn’t answer my query over the phone, he would be on site the next day.
Some of the instrumentation showed sufficient excess pore water pressure had dissipated to allow for the next lift of the embankments to go on. The dissipation of sufficient excess pore water pressure (90%) was needed to proceed; if this wasn’t achieved, the risk of proceeding might have led to slope failure.
Instrumentation and the data collected weekly were very important and helped with programming ahead with earthworks.”
Philip O’Connor
Site Engineer
John Sisk & Son (Holdings) Ltd
Contact
For more information on this project, please contact Michael Durnin at mdurnin@murphygs.ie or +353 86 856 57955
