OWNER:
MVV Environmental
ENGINEER:
Doran Consulting, Incico Spa
GENERAL CONTRACTOR:
Kandevia Inova UK LTD
MAIN FIGURES:
c.8,500 CMCs, c.2,700 BMCs
Project Details
The Medworth Energy-from-Waste CHP facility in Wisbech, Cambridgeshire, will convert over 500,000 tonnes of waste into valuable energy each year, producing enough power for around 150,000 homes and supporting local industrial energy needs. Menard entered a joint bid with its sister company Bachy Soletanche, to design and install a fully integrated geotechnical solution, combining their expertise and those of their sister company Dunton Environmental to deliver the scheme. The scope of the works comprised:
• an underground waste bunker formed through the combination of a jet-grouted plug and secant pile wall system, and a Trenchmix® cut-off wall (Bachy Soletanche)
• ground improvement using Controlled Modulus Columns (CMCs) and Bi-Modulus Columns (BMCs) across the wider development area (Menard)
• enabling works, working platform upkeep, and ancillary support services associated with the ground improvement package (Dunton Environmental)
Ground Conditions
Made ground is present in some areas, underlain by weak Cohesive Tidal Flat Deposits, onto loose to medium dense becoming dense silty sands (Granular Tidal Flat Deposits) over Glacial Till comprising stiff clay. The cable percussive boreholes were supplemented by a series of Cone Penetration Tests to provide in-depth geotechnical parameters for detailed ground improvement design.
Solution
Menard provided ground improvement beneath the foundations and slabs of over 25 different structures, including the Tipping, Boiler and Turbine Halls, together with workshops, storage areas, various tanks and crane bases. More than 8,500 CMCs and 2,700 BMCs were constructed over a 4 month period using 3 rigs. These were installed on a tight grid pattern to depths ranging from 5 m to 15 m. BMCs were deployed where deep cut off levels were required in bunkers and crane bases. This innovative solution combines a CMC with a stone column section at the top, meaning there is no need to immediately trim the top (stone) section and facilitating easier follow-on excavations. Quality and verification testing was carried out, comprising regular concrete cube testing and 29 plate load tests. The close coordination between Bachy Soletanche, Menard and Dunton Environmental contributed to a successful delivery programme within a busy, multi-contractor environment.
Sustainable development
Menard's CMCs and BMCs were installed using bespoke displacement rigs, eliminating the generation of spoil. Hydrotreated vegetable oil (HVO) fuel and ultra-low carbon concrete were utilised to further reduce the carbon footprint of the ground improvement works.
