Director

Hewson Consulting Engineers

Presentation

Alexei Bond, previously Project Director – Energy & Water, Morgan Sindall Infrastructure; and Andrew Hodgkinson, Director, Hewson Consulting Engineers

Accelerated construction methods for Tideway’s Carnwath Road Shaft

In late 2021 BMB JV faced significant programme challenges in completing the Carnwath Road shaft on Tideway West. The 25m diameter by 40m deep shaft was designed to be lined and finished from the bottom up using traditional methods including the construction of a mezzanine plant room and roof slab as the final steps.  This linear construction sequence was simply too slow, so the JV turned to Hewson Consulting for ideas on how to speed things up. Hewson proposed a radically different top-down method for the upper shaft mezzanine and roof slab structures. This involved the use of massive storey height steel transfer trusses to be hung from the top of the secondary lining walls rather than supported from below. They also recommended using modular precast for the concrete beams and slabs to avoid the need for any falsework support.  This meant that other works in the lower part of the shaft could continue in parallel whilst the upper shaft structures were constructed. This uniquely creative method solved the programme challenge whilst also improving safety and quality. This joint presentation will describe the story of how this design evolved highlighting the design and construction challenges that were overcome to accelerate completion of the shaft