Geotechnics

 

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For several years we have been working on improving techniques for characterisation of soft compressible soils, with a particular emphasis on sample disturbance. Post Doc Shane Donohue has developed some rapid techniques involving measurement of shear wave velocity and suction for assessing sample disturbance in clays. Currently we have turned out attention to more difficult soils such as peat and silt.

Given the background of large peat landslides in Ireland, PhD candidate Noel Boylan is working on peat strength. He has built a special DSS apparatus to observe the deformation patterns of peat under shear. He has also been using T-bar and Ball tests to assess peat in situ. (see photo of Pollatomish landslide, Co. May 2003 attached)

PhD candidate Sophie O'Connor is investigating the BRE alluvial clay research site in Crayford, UK with a particular emphasis on use of the CPT to characterise "non-textbook" soft soils and peats.

Our work is being carried out in collaboration primarily with the Norwegian Geotechnical Institute, the Norwegian Public Roads Administration, TU Delft, BRE Hokkaido University in Japan and CPT operator Lankelma.

M. Long, S. Donohue, N. Boylan, S O'Connor, G.Cosgrave

This is currently a topical subject due to the increased pressure to develop underground space and several proposed tunnelling projects, such as the METRO and the CIE Rail Interconnector project. PhD candidate Carl Brangan has monitored the behaviour of ten deep basements. Advanced laboratory and in situ testing has been carried out on high quality samples. We have had particular success with testing GeoBore-S cores and with in situ assessment of shear wave velocity using MASW surface waves. Issues related to excavation in clay tills have now been examined in detail and we have now turned our attention to high cantilever walls in the clay till as well as excavation in the water bearing gravels near the city centre as well as the soft soils along the Docklands. We have greatly profited from collaboration with consulting engineers GCG in London on the Dublin Port Tunnel project.

C. Brangan, S. Donohue, M. Long

 

Here we collaborate strongly with the Norwegian geotechnical Institute and we have several projects, e.g.:

  • development of a seabed sampler for taking up to 40 m long high quality samples in deep water
  • development of a box corer for taking high quality samples from the upper 1 m to 1.5 m of the sea bed
  • developing techniques for rapid assessment of soil sample quality

S. Donohue, M. Long, G. Cosgrave