OWNER:
Chancerygate and Bridges Fund Management
ENGINEER:
I & L Consulting Limited
GENERAL CONTRACTOR:
Harmonix Construction
MAIN FIGURES:
739 Controlled Modulus Columns
384 Vibro Stone Columns
Project Details
It was proposed to construct a large industrial development (Units 1-9) at a site off Red Lion Road in Tolworth, London. The original design was based on a pile solution for all the units and Harmonix Construction approached Menard UK to advise them if it was technically viable to offer an alternative full ground treatment design on all the units in lieu of traditional piles. Menard UK saw benefit in offering a hybrid solution of Vibro Stone Columns in the more competent soils and Controlled Modulus Columns in the weaker soil areas, thus offering Harmonix a consistent foundation solution of traditional pads and strips and a fully ground bearing slab across all Units.
Ground Conditions
Ground conditions on site were split between areas with a thin mantle of made ground directly underlain by soft/firm becoming stiff clays (at about 3-4m) of the London Clay Formation beneath Units 6-9, to soils within a former landfill area, containing deep uncontrolled made ground consisting of layers of soft and very soft clays to depths of 7-8m beneath Units 1-5. The made ground landfill was underlain by soft/ firm becoming stiff London Clays. The site was predominantly flat as and such only needed a modest amount of cut/ fill in the range of – 0.4m to +0.5m to establish a working platform level of 300mm below FFL’s for all the units.
Solution
Menard UK provided a combined solution of 384nr Vibro Stone Columns (VSC) each between 400-500mm diameter to depths of 3-4m on Units 6-9 (1,500m2 plan area) and 739 nr Controlled Modulus Columns (CMC), 320mm diameter installed to depths of between 4m and 12.5m across the Units 1-5 (3,240m2 plan area). The foundations were designed to a bearing pressure of 150kPa on the VSC units 6-9 and 200kPa on the CMC units 1-5. Slabs on the units 1-4 and 6-9 were designed to 37.5kPa and Unit 5 to 50kPa. Settlements on all units were limited to 25mm long term total settlement with a relative differential settlement of 1/500 maximum. During the design process the CPT undertaken prior to the ground treatment operations allowed for an optimisation of the design. This allowed the project being carried out ahead of schedule.
