OWNER:
MCI Developments
ENGINEER:
Coopers Chartered Consulting Engineers
GENERAL CONTRACTOR:
N/A
MAIN FIGURES:
c.4,100 CMC/BMCs & c.100 VSCs
Project Details
MCI Developments’ original strategy was to dig out the Made Ground and Engineer back in which would be slow and expensive. IGE Consulting approached Menard to find a cost-effective solution for the development of 234 residential dwellings. The site is surrounded by existing residential dwellings and is located at the end of Eldercott Road in Bolton.
Ground Conditions
The site investigation report revealed that the site was a former clay pit that had been subsequently used as a landfill site for domestic refuse. The Made Ground consisted of Silty Clays which reached depths of up to 27.3m to the East of the site underlain by Mudstone. Further investigation with CPT’s showed that the near-surface low strength Clays had a CPT cone resistance of 1.0MPa; the strength of the Clays improved up to 3.5MPa with depth. The use of the CPT testing also helped to delineate the positions of the high walls of the former clay pit.
Solution
Menard offered a solution of Controlled Modulus Columns (CMC) beneath the Residential Dwellings and Bi-modulus Columns (BMC) beneath the highways. To the North West of the site, the depth of the Made Ground is relatively shallow and Vibro Stone Columns (VSC) were utilised to further provide our client with a cost-effective solution. The adoption of these Ground Improvement solutions reduced the residual settlements under exploitation loads to <25mm with relative differential settlements limited to 1/500. The final detailed design comprised c.4,100 CMC/BMC with a diameter of 300mm and c.100 VSC with a diameter of 400mm. The works were completed over 3 No. phases utilising 1 No. CMC rig and 1 No. VSC rig. The works were verified through a thorough quality control comprising plate load tests, compressive strength tests on concrete samples, and drilling/concreting logs from the rig computers.
