Ongoing maintenance and restoration of canals

British Waterways have an ongoing program of maintenance for existing canals and a restoration program for closed sections of the network. Across a number of canals, a program of reinforcement of bridges is being undertaken.

The contractor required the 31/15 mm tubes into 50 mm diameter holes in the arch stone block on either side of each bridge, including the keystone block.

Seven bolts were used on each bridge, four and three installed from opposite sides respectively. Each bolt was positioned equidistant around the periphery of the bridge-arched section, to overlap the bolts installed from the opposite side, giving an interlocked finger like construction. The rockbolt lengths varied according to the width of each bridge and ranged between 3.5 and 4.5 metres long, terminating in the opposite side arched block.

Each nail head assembly had a 130 mm diameter non-metallic end plate and high-load glass reinforced nylon nut with a threaded end capacity of 200 kN. The nail head assemblies were recessed into the bridge arch by over-coring the rockbolt holes. The over-cored sections were 200 mm deep by 150mm diameter.

All the bolts were fully grouted with cementitious material, which was pumped through each tube, filling the pre-drilled holes and any voids in the brickwork. To maintain the aesthetics of the bridge structure, the over-cored section of each stone block was replaced after bolt installation. To validate the integrity of the reinforcement system, each rockbolt was pull tested to 25 kN, which was 150 % of the working load.

Condor carry out many different types of work on canals, bridges and locks including the cutting and fitting of new lock ladders, pressure grouting to prevent leaks and pressure pointing, particularly in locks as shown in the photograph above