Ground consolidation is a phrase that you may see more frequently in the future. It is a system used by foundation engineering contractors and seems to be gaining popularity worldwide. Recently in Chilliwick, BC, Canada AMEC Earth & Environmental was retained as a contractor to provide geotechnical consultant services to provide geotechnical consultant services for the design and construction of a fire station hall and office building, with a rectangular footprint of approximately 130 by 262 feet. The fire station hall was two stories high with five apparatus bays and three – storey hose tower. The office building will be four stories high. Rapid Impact Compactors Ltd [agent for BSP International Foundations} was chosen to compact the granular soils as part of the ground – improvement program. They used a rapid impact compactor in the 7 tonne mode, mounted onto a 40 tonne Hitachi 400 H hydraulic excavator. At this site it was the required depth of compaction that was critical.

“We were asked by AMEC to densify the ground to a depth of 14.75 feet,” commented Joe Miller, Managing Director of Rapid Impact Compactors. “AFTER TESTING DENSITIES HAD ACTUALLY BEEN INCREASED TO MORE THAN 29 FEET.” For this kind of compaction [or ground consolidations], BSP’s attachment is mounted onto a suitably sized hydraulic excavator. It is more efficient than suspending a 10 or 15 ton weight from a crane and dropping it from a predetermined height of 15 to 50 feet. The rapid impact compactor’s foot [diameter of 1.5 mt stays in contact with the ground. Energy is imparted by dropping the weight through a relatively small height of up to 4 feet at a rate of between 40 and 60 blows per minute. Although the energy per blow is small in comparison with conventional dynamic compaction, the rapid blow frequency amply compensates and can result in a much greater total energy output per unit area of the site. Quality control Becker Penetration Testing was done after completion of the ground improvement work and it confirmed that the rapid impact compactor’s success in densifying the granular soils to a depth of around 19.5n feet. “The use of this compactor has been very successful,” assets Henrick Kristiansen, AMEC’s project manager, “It is proving to be a very cost-efficient ground improvement method.”

Soils compactors can do more. One common task that we will only mention briefly here is compaction at landfills where space becomes more precious each month.

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