Background

TBT Engineering Limited was retained by the client to carry out a geotechnical investigation for the proposed bio mass conversion project at the Ontario Power Generation (OPG) Station.

Project Highlights

A sub-surface investigation for the proposed project was completed and a report documenting the findings of the field investigation for the proposed facility was submitted.

TBT Engineering’s Role

Fieldwork was carried out utilizing a geotechnical drill rig and excavator.  In consultation with the client, the majority of the borehole and test pit locations were altered in the field to accommodate required service setbacks. Test pits were located outside of the proposed structure footprint to avoid excessive disturbance of the existing subgrade.

Boreholes were advanced using hollow stem augers to auger refusal.  Certain Boreholes were advanced past auger refusal using diamond drilling techniques.  Twelve test pits were excavated – termination occurred either due to excavation caving, refusal or due to the limitation of the excavator.

During the drilling operations, soil samples were obtained from the auger flights and using the techniques of the standard penetration test (SPT). This involved driving a 51 mm diameter thick-walled sampler into the soil under the energy of a 63.5 kg weight falling through 760 mm. The number of blows required to drive the sampler 0.3 m is known as the standard penetration blow count (N) which provides an indication of the condition or consistency of the soil. Following completion of the test, a representative soil sample was obtained from within the sampler. Soil samples were also collected from excavated material within the test pits. In addition, hand operated cone penetration testing (CPT) was carried out at selected locations.

Result Reporting

In addition to investigation procedures and a description of sub-surface conditions, the final report centered on recommendations and discussions for the following topics

–   Suitability of existing fill materials for foundation support

–   Raft foundation – discussion on raft foundation on existing fills

–   Shallow footings on soil – discussion on shallow footings over existing fills

–   Bearing capacity of bedrock

–   Rock socketed piles – lateral capacity of rock socketed piles

–   Compacted engineering fill

–   Rock anchors

–   Lateral earth pressure coefficients

–   Slabs on grade

–   Frost Protection – penetration, heave, jacking – adfreeze

–   Subgrade preparation

–   Seismic site classification

–   Excavations