The causeway supporting the pier foundations for the railway viaduct had been subjected to several programmes of grouting. The work specification was prepared by
C.I.E. and a constant check had to be kept on the grout levels during injection, to
ensure a sufficient spread was being maintained in the strata below the viaduct.
Each span and pier was first dried out by placing a purpose made sheet pile dam across two of the piers, the sheet piles being driven into the seabed on each occasion. Th is allowed drilling and installation of the grout pipes to take place in reasonably dry surface conditions. The exercise was carried out in the 1950’s, 60’s & 70’s to prevent scouring of the river bed, and undermining of the viaduct foundations by tidal flow in the bay. Joseph Edwards supervised these earlier works during his time with Cementation Limited and lately for PJ Edwards & Co Ltd.
In August 2009 one of the viaduct piers collaped due to severe scouring in the causeway. A passenger train had just passed over when the train driver witnessed the collapse behind him. Due to his immediate emergency response, he prevented a certain catasrophe had the next train reached the viaduct. Emergency works were required to repair the causeway, rebuild the collapsed peir and decking and upgrade the remaining existing piers through underpinning. The works were designed by Irish Rail.
PJ Edwards & Co Ltd were engaged to carry out the underpinning of the existing piers by minipiling using 51 & 76mm hollow stem self-drilling piling techniques. These piles were drilled to depths of up to 18.5 metres through the existing stone filled causeway, typically 6 metres deep overlying 6 metres of silt, overlying very stiff boulder clay. Each pile required coring a 150mm corehole through the existing ashlar limestone masonry pier and installing a 135mm diameter permanent casing into the causeway. The silt below the causeway was then pregrouted below the casing for a depth of 2.5 metres before the pile was finally installed.