Maccaferri UK proposes an innovative method for designing working piling platforms by using its geosynthetic reinforced products.
MWH Treatment Ltd, based in Heywood, Lancashire have commissioned a Carbonarious Biomass Facility. The design of this £100M biomass energy plant replaces the previously consented bioethanol plant.
The finished plant will take up to 175,000 tonnes of fuel per annum and use the latest technology to provide enough renewable electricity to meet the average needs of approximately 37,000 households.
The site is located at Ince in Cheshire, on the Ince Marshes, which forms part of the southern flood plain of the River Mersey. It is located about 500 m south of the Manchester Ship Canal, which runs from west to east along the south bank of the river. The area of development is characterised by poor ground condition comprising of soft clay and peat.
The Principle Contractor is MBV Energy, a joint venture between MWH and Black & Veatch. Ward and Burke Construction Limited, based in Bourne End, Buckinghamshire is the Civil’s contractor.
The foundation works, worth approximately £1m with the piles structure for the power plant, were designed and installed by Aarslef Piling, based in Newark (sub-contracted by Ward & Burke). The contract requires the installation of approximately 990 piles – 350mm square and 30-metre average length.
Working platforms are temporary structures that provide a suitable foundation for heavy construction plant and machinery. Modern platforms can weigh up to 200 tonnes and require critical safety measures as bearing capacity failure can cause overturning of large machinery.
Maccaferri proposed an innovative method for designing this type of structure based on applying the load to a defined rectangular area. The size of this area is based on the load data of construction plant to be used. This design methodology is supported by analytics which allows the calculation of the tensile forces in each of the reinforcing geogrid layers generated by several factors: the horizontal thrust due to the self-weight of different soil layers, the wheel or track load of heavy vehicles and the membrane effect at the base or subbase – subgrade interface.
With this information, it is possible to determine the optimum number and mechanical characteristics of the geogrid layers required to absorb the forces as mentioned above to ensure that the platform has the rigidity to prevent catastrophic failure.
This new methodology, which Maccaferri has presented at several international geotechnical and geosynthetics conferences, resulted in an approximate 25% reduction in the amount of granular material required compared to the initial proposed design approach.
In some areas, the platform has a thickness of up to 1.2m of compacted granular material with a combination of four layers of high strength polyester woven MacTex W2 geotextile and MacGrid WG woven geogrids. The working platform for the piling operations has a foot-print area of 24,000 sqm consisting of more than 12,000 sqm of geosynthetic reinforced material culminating in one of the largest applications of this type within the UK.