OWNER:
Mr & Mrs Clegg
ENGINEER:
Springett Associates
GENERAL CONTRACTOR:
SGD Building Ltd.
MAIN FIGURES:
53 Vibro Stone Columns
Project Details
The owners of a single dwelling initially intended to renovate the existing structure. However, following a detailed assessment, it became evident that the building was largely beyond repair. As a result, they opted to demolish the property and construct a new home on the original footprint. Seeking a more cost-effective alternative to mini piles, an independent builder approached Menard for a solution. Menard recommended Vibro Stone Columns as an efficient ground improvement method to enhance the soil’s bearing capacity and minimise settlement under structural loads.
Ground Conditions
A ground investigation was carried out comprising four boreholes, one dynamic probe, and four trial pits. Each borehole was preceded by a shallow trial pit to assist with initial observations. The exploratory works revealed a layer of low-strength, very sandy, slightly gravelly clay extending to approximately 3.2 metres depth. This was underlain by a stronger stratum of very sandy, gravelly clay with significantly higher strength characteristics.
Solution
Menard installed a total of 53 Vibro Stone Columns (VSCs) beneath the 0.6 m wide strip footings, reaching consistent depths between 3.1 and 3.4 metres. The ground improvement was designed to support the strip footings with a required serviceability limit state (SLS) bearing capacity of 125 kPa, while controlling total settlement to less than 25 mm and limiting differential settlement to a ratio of less than 1:500. To verify the effectiveness of the ground improvement, one plate load test and one dummy footing test were conducted. All works were successfully completed within a two-day period.
Sustainability
Menard proposed a Vibro Stone Column (VSC) solution as a sustainable alternative to the originally specified mini pile scheme, significantly reducing the project’s carbon footprint. The aggregate used to form the VSCs was locally sourced, further minimising environmental impact by reducing transportation emissions and supporting regional supply chains.
