The Hurst Brook which carries water from the Pennine hills passes through Glossop town centre.
During the construction of the Town Hall, in the 18th Century, it was decided to Culvert a length of the river to extend the market place and provide a space for parking. The Culvert was constructed using masonry sidewalls with a brick arch crown section. The structure was then backfilled.
Subsequent to this a sewage pipe was placed in the river channel with manhole connections in two places along the culvert length. During a recent storm one of these manholes, in the centre of the culvert, became dislodged bringing with it a section of the masonry sidewall. This instability lead to an area of the car park being fenced off and a requirement for a repair to the culvert lining.
- Pollution of the watercourse
- Problems with access
- Lack of details of the existing structure
- Changes to the river flow
- Risk of further collapse
High Peak Council asked Derby City Council Water Management Engineers to prepare a scheme for the remedial works. The final solution was a team effort involving input from the following parties:
- Whitehouse Construction, as Facility Managers and Main Contractor Specialist Engineering Services Contracting Division, as specialist Sub-Contractor
- Natural Cement Distribution, as specialist material supplier.
The key features included:
- The use of natural material avoiding the use of potentially harmful construction chemicals
- The use of bagged materials, which could be easily stored on site and transported to the job site
- A flexible approach to specification, method and risk allowing important decisions to be made on site in conjunction with the engineers. A material which avoided the use of blockwork or shuttering and quickly reached its final set.
- A material which would provide immediate support to the area having removed the existing displaced blockwork.
A brief description of the method was as follows. SES formed a project team involving John Shone as Project Engineer and Colin Cook as Site Manager. Access was made to the culvert by forming a ramp at the downstream end. Bunds were also formed in the river channels.
A temporary island was formed adjacent to the damaged section using stone filled IBC bags. The dry shotcrete machine was placed onto this island and bagged NATCEM 430F transported to the site in dump trucks. The blockwork was removed from the top working downwards. As each section was removed the area was secured with a layer of NATCEM 430F. This material contains Bekaert Dramix 30.5 steel fibres at the rate of 30kgs per cubic metre.
This provided initial primary support to the lining above and prevented any unravelling of the loose fill behind. On completion the secondary lining was sprayed back to the original tunnel profile.
The work was safely completed and the car park fully re-opened ready for the Christmas Market.