This project comprised a comprehensive ground investigation for a large-scale residential development on a greenfield site in East Cork. The proposed development includes over 250 dwellings, a crèche, and a community building.
Scope of Works
The investigation included the following:
- Role of Project Supervisor Construction Stage (PSCS)
- 16 cable percussive boreholes
- 7 rotary core boreholes
- 7 trial pits
- Soil and rock laboratory testing
- 14 Plate Load Tests
- 35 dynamic probes
- Preparation of both factual and interpretative reports
Ground Conditions & Findings
The site was underlain by soft to stiff glacial till, typically increasing in consistency with depth, overlying sandstone bedrock. Key geotechnical findings included:
- A characteristic undrained shear strength (cu,k) of 160 kPa, derived from a characteristic SPT N-value of 29.
- Plate Load Test results confirmed that a ground-bearing slab would be sufficient.
- Laboratory testing indicated that no special precautions were required to protect concrete elements from chemical attack.
As expected with glacial deposits, the rockhead varied across the site. Combined with site topography, this required a cut-and-fill approach, with the potential need for significant lean mix.
As ground investigation only addresses a minute sample of the ground conditions and as glacial till can vary substantially both horizontally and vertically, the final phase of Controlling and Monitoring by competent persons is key to ensuring quality and safety during excavations and pouring of foundations.