An innovative ground improvement method using controlled dynamic compaction at fast blow rate.
Dynamic soil-compaction methods have historically involved the use of tall cranes and free-falling weights, imposing limitations on the types of sites that can be treated. The Rapid Impact Compactor (RIC) brings to the dynamic compaction industry the ability to carry out soil densification in the upper layers of soil quickly, with fast mobilization and low overheads. Its base carrier is a track-mounted excavator, which provides the dual benefit of allowing improved mobility and site accessibility. BSP can supply a complete rig, mounted on a range of different excavators, or the front end equipment, to mount on a customer’s base machine – subject to it being in good order.
The Rapid Impact Compactor was originally developed in the early 1990's by B.S.P. in conjunction with the British Military as a means of quickly repairing damaged aircraft runways. Dynamic energy is imparted by a falling dropweight dropping from a controlled height onto a patented foot. Energy is transferred to the ground safely and efficiently as the RIC's foot remains in contact with the ground. No flying debris is ejected.
Compaction parameters - Energy, Blow Counts and Soil Penetration are automatically controlled and monitored from the RIC's cab with an on-board data acquisition system.
The Rapid Impact Compactor is a welcome supplement the current suite of ground improvement tools available to the ground engineering community. Its versatility can provide engineers with a more cost effective means of dealing with poorly compacted or loose shallow deposits. The following are some key operational features of the equipment:
- The RIC impacts the soil at a rate of 40-60 blows per minute using a 5, 7 or 9 Tonne dropweight. (Larger models can be designed on request)
- The drop height of the weight can be adjusted using the in-cab computer up to 1.2m,
- Energy is transferred to the soil through a 1.5m diameter steel “foot” that rests on the ground surface.
- Noise levels have been measured of the order of 88 dBA at 6m
On-Board Computer
The Rapid Impact Compactor employs an on-board computer to control impact set termination criteria, and to record critical data. Acquired data at each impact point include: total energy input, total penetration, and penetration of final set.
Ground Vibrations
At 30m the peak particle velocities have been measured to vary from 1.2 to 5mm/sec. Vibrations will vary with material type, and will increase as the degree of compaction achieved increases. Results to date indicate that without site specific testing, a safe working distance to structures can be on the order of 6m.
Versatility
Having the RIC mounted on a tracked machine gives it the versatility to move about in narrow and limited height spaces, such as within existing warehouses.
Mobility
In most countries the RIC is able to be transported as a single unit, with the Impact Foot removed and the front end lowered horizontally on a flat-bed trailer. The machine can be ready to work just a few minutes after off-loading. If road restrictions apply the unit can be easily split into two loads with excavator traveling separately from the hammer. Re-assembly is achieved in less than two hours and done without need of "Helper" cranes or other hoisting devices.
Applications
The versatility of RIC is such that numerous applications are possible. Essentially RIC was designed for compaction of granular soils, but benefits have also been noted in random fills and mine wastes. Compaction of fills and loose natural deposits is the typical objective; however, the RIC equipment can also serve as a diagnostic tool, identifying zones that do not respond well to dynamic compaction. Identification of these zones allows the engineer to accurately localize areas for removal and re-compaction, and can provide superior economy on sites where the only apparent solution is to replace all fills because investigations have indicated the presence of some undesirable soils.
Assessment of compaction achieved in random fills is typically more difficult to test (and hence quantify), the visual aspect of settlement of the surface supports the fact that ground improvement is being achieved. As use of the equipment is expanded so will be the data base of test information.
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