Railway Station Platform in Dublin
We were asked to carry out a design and construct underpinning system to prevent further horizontal and vertical movement of a railway platform retaining wall.
The platform was relying on support from a 450mm wide masonry retaining wall. Unfortunately the foundations to the wall were not at a suitable depth and the wall at 450mm wide was not sufficient to support the horizontal movement caused by the fill material behind it.
The wall in places had moved laterally by up to 100mm and this movement had caused a dropping of the platform surface which was becoming unsuitable for pedestrian traffic.
Our underpinning scheme consisted of low vibration mini piles and cantilever needle beams to support the wall and prevent further downward movement. The cantilever needle beams were incorporated within a raft slab so that the weight of the fill material above could be used to lessen the tension requirement of the rear piles.
Diamond coring was carried out to form the needle pockets this reduced excessive vibration on the already distressed retaining wall. Parallel Flange Channels were used as the needle reinforcement.
We thought it would be advantageous to cast a new retaining wall off our raft slab, this new retaining wall would remove all horizontal loading from the old wall and prevent further movement. Reinforcing bars were resin anchored into the old retaining wall and these were cast into the new wall to add to the stability of the old retaining wall and prevent it overturning under its own self weight.
We installed 130No 105mm dia mini piles and constructed 90No needle beams / raft slab to support 90l/m of retaining wall and platform with the railway line fully operational.