To rebuild a collapsed section of masonry dock wall, and cast concrete bases to the dock wall corners at the inner end of the lock pit entrance to Millbay Docks.
Kaymac Marine & Civil Engineering Ltd were commissioned to rebuild a collapsed section of masonry dock wall, and cast concrete bases to the dock wall corners at the inner end of the lock pit entrance to Millbay Docks in Plymouth.
As the dock was being renovated, it was necessary to carry out at total rebuild to the 26m long collapsed section of grade II listed masonry wall. In addition, brick and masonry repairs were required to the corners of the lock entrance.
Prior to this, the concrete bases had to be cast at the low water mark to the main wall section and to each corner to allow a sound foundation for the reconstruction works.
The concrete was placed within formwork constructed below water by divers and secured to the existing structure with mechanical anchors. The concrete was a pump mix with an underwater additive to prevent washout of the cement from the affected areas. The lock gates and other machinery for operating the gates and levelling sluices had been removed in the prior to the works commencement.
With the foundation works completed, the masonry and brick walls were reconstructed from the water level upwards and the original masonry blockwork from the collapsed main section of wall was recovered from the dock bottom by a dredger. Any shortfall in masonry was made up using similar masonry provided by the client and approved by Plymouth City Council’s heritage department.
The ground behind the new walls was filled with no-fines concrete, which allowed drainage of the tidal water from behind the walls via weep-holes constructed in the mortar joints to prevent Hydrostatic loading during ebb tides.
The works above water were carried out using Kaymac Jetfloat pontoons, and included bedding in new masonry blocks to suit the existing and replacement brickwork. Finally, all four of the dock walls were mechanically repointed using hydraulic lime mortar. The project was delivered to specification and within budget.