RIC is a technique allied to Dynamic Compaction that can be used to increase the bearing capacity of soils through controlled impact.
This treatment is effective in the top layers of earth typically up to 6m depth, though improvements up to 9m have been seen in some conditions. A dropweight of 5 to 16 tonnes (depending on size) is dropped onto a special foot assembly 40-60 times a minute. The foot remains in contact with the ground at all times.
Control: The machine is accurately controlled from the excavator cab with the degree of compaction electronically monitored.
Safety: The impact foot is in contact with the ground at all times, eliminating the risk of flying debris. Unlike conventional DC; other activities can take place in close proximity.
Quality: The impact energy and soil deflections are recorded by the onboard computer for presentation of compaction data. The information can highlight weak zones where extra fill is required or zones where underground obstructions are present (i.e. previously hidden old foundations).
Speed: The unit is mounted on standard excavators, typically in the 40-90 tonne class and can be mobilised in minutes from arrival on site.
The method for efficiently covering the ground varies from country to country. A common pattern used to cover a track in three passes [see diagram below]. The outer points (black) being compacted first, followed by the intermediate (orange) and lastly the infilling positions (blue). This has the effect of achieving the best depth of influence. The first pass affecting the ground to a deeper level than the latter.
Most granular fills and some silts are compactable, the best results being achieved where the fill is a well-graded particle size. An area of 800m² -16000m² can be covered in an average day (depending on the ‘blow-per-position’ setting.) This also allows time for routine maintenance and rotation of the special dolley pads located in the foot assembly, which transfers the force of the blow through to the ground.