CARRICKFERGUS CASTLE, NORTHERN IRELAND
Carrickfergus Castle is a Norman castle in Northern Ireland, situated in the town of Carrickfergus in County Antrim, on the northern shore of Belfast Lough.
Besieged in turn by the Scots, Irish, English and French, the castle played an important military role until 1928 and remains one of the best preserved medieval structures in Ireland.
For more than 800 years, Carrickfergus Castle has been an imposing monument on the Northern Ireland landscape whether approached by land, sea or air. The castle now houses historical displays as well as cannons from the 17th to the 19th centuries.
Material: LECA LWA (10-20mm)
Interesting Fact: The pneumatic blowing delivery of Leca LWA speeded up the delivery process significantly, with up to 1 m3 of Leca LWA being delivered per minute.
Delivery Method: Pneumatic Delivery
Main Contractor: Adman Limited
Overview of Project
Recently, reparation works were organised to strengthen the ancient structure. This required substantial backfill for the ancient walls.
This unique engineering project had issues which required remedy, including limited access to the site, delicate groundworks with the adjacency to the local river and the delicacy of a heritage structure which is over 800 years old.
Furthermore, with a vertical rise of 4m to the entrance – alternative solutions such as gravel or type 1 fill was a negative solution due to excessive weight and delivery limitations.
Leca LWA was selected due to its natural lightweight properties as a lightweight back fill for retaining walls, its water management properties and its unique ability to be pneumatically blown through a piping system – reducing the need for bulk bags being delivered throughout this delicate and historical castle. The engineers on site required up to 50m of piping to reach the area of the works.
The pneumatic blowing delivery of Leca LWA speeded up the delivery process significantly, with up to 1 m3 of Leca LWA being delivered per minute. Due to the height differentials and access obstacles leading to the area of the works including an up-pedestrian ramp/Steps and grass verge.
The pneumatic delivery also posed no problem as the blowing facility can be blown up to 20m vertically, where it has be used for roofs and down into basement structures.
For this project, permission was granted to stockpile the Leca LWA outside the castle on the local car park. From this stockpile, the Leca LWA could be easily loaded up on the pneumatic delivery truck.
Natural Properties of Leca® LWA
A fill structure produces additional loads when it is placed and compacted on a landscape environment; the effects of the additional load are typically most pronounced in the locations of the landscape containing a soft soil subgrade. The load magnitude depends on the fill material density and thickness, and the effect of the additional load produces long term settlement of the landscape embankment or structure. Magnitude of the load affects settlement sensitive soil in proportion of the softness of the soil, with impacts ranging from high total settlement to unacceptably high differential settlement or tilting of the structure.
By using Leca LWA as a fill material within landscapes, the impact of additional loads produced by the soil layers on the subgrade can be reduced significantly and long term settlements decreased. Differential settlements created by loads or soil conditions can also be compensated with the help of a transitional lightweight structure.
When the groundwater or surface water level is high, it can also be good practice to partially reduce the weight of the fill structure to ease the pressure on the surrounding area. This structure was designed with consideration to buoyancy connected with rising water levels within structures located in vicinity of a water body or flood area.