DEFINITION OF AN IMPACT COMPACTOR PASS
A “pass” for the dual drum 3-sided impact compactor is defined as two runs of the compactor over a 4 meter wide lane such that one drum of the compactor during its second run travels in the middle of the inter-drum space created by the first run of the run of the compactor. Overlapping of drum paths in two consecutive runs (i.e. in one pass) will not be permitted.
TYPICAL PRODUCTION RATES
Note that these are guidelines only and production is dependent on material type and condition.
IN-SITU COMPACTION: 3,500 m2 (38,000 ft2) / shift
PROOF ROLLING: 12,500 m2 (135,000 ft2) / shift
500-650mm (1.5 ft) Layer: 10,000 m2 (108,000 ft2) / shift
650-800mm (2.5 ft) Layer: 6,700 m2 (72,000 ft2) / shift
800-1000mm (3.0 ft) Layer: 5,000 m2 (54,000 ft2) / shift
Typical stanadrds/specifications regarding vibrations on a construction site include the following:
Although these predominantly refer to the driving of piles, vibratory equipment and/or blasting, they do serve as a great guideline for the industry.
Although vibrations are very dependent on the material charateristics/properties and the effect of the vibrations on adjacent structures is very much a factor of the structure itself (building material, foundation type, age, etc), it is very rare that an IMPACT COMPACTOR will generate anything beyond 15mm/s (0.6 in/s). Much of the "fear" is a perception due to the impact on the surface but, according to the governing standards and specifications, very little to no damage will generally be created through the use of an impact compactor.
If there is fear that the effects are greater than one would prefer, then most of the effects can be mitigated by digging a trench between the path of the roller and the structure in question. It is preferable to have the trench dug a little deeper than the foundation depth of the structure in question and, generally, no wider than 500mm (20 in) would be necessary. In this way, the vibration waves would not propogate through the trench, reducing the effects dramatically.
STANDARD STRUCTURES It is reasonable to accept the limits of 19-25.4 mm/s (0.75-1.0 in/s) as the sensible limit range for ground vibrations which cannot damage residential structures due to only direct vibration effects on structures. These criteria are not accepted for resonance structure, soil vibrations, or dynamic settlement. As each construction site is unique, the engineer shall make a decision based on conditions at the specified site. There are no case histories of generation of resonant structural vibrations at large distances from impact pile driving. Therefore, it is reasonable to not consider such effects for practical purposes. Vibratory pile driving and other construction equipment may produce resonant floor vibrations and also resonant vibrations of soil layers. The application of 51 mm/s (2 in/s) limit for measured structural vibrations can help to determine unacceptable vibrations of various structures. What about Liquifaction? Liquifaction can in fact be triggered by very high vibrations and these would typically be beyond 100 mm/s (4 in/s).
HISTORIC STRUCTURES It is generally accepted to restrict vibrations of 2.5mm/s (0.1in/s) on historic buildings.
The noise levels created by construction equipment will vary greatly depending on factors such as the type of equipment, the specific model, the operation being performed, and the condition of the equipment. The equivalent sound level of the construction activity also depends on the fraction of time that the equipment is operated over the time period of construction.
The general guideline, although this may differ from state to state or country to country, is to maintain noise levels in a residential area to 90DBA and in Commercial and Industrial areas to 100dBA. This reduces to 80dBA for a residential area but remains unchanged at 100dBA for Commercial and Industrial areas.
Typical noise levels at 50ft from the source are as follows:
Dozer 85 dBA
Grader 85 dBA
Roller 74 dBA
Scraper 89 dBA
Truck 88 dBA
Generally an Impact Compactor, towed by an agricultural tractor of no less than 400hp, would have a typical noise level of 78-84dBA.
The Federal Highway Administration (FHWA) suggests a method for estimating the construction noise levels and although associated with the construction of a highway, it can be used as a guideline for any project.
Effective identification of isolated weak “spots” on site; eliminating of potential “bridging” effect experienced by conventional smooth drum rollers. Individual heavy roller impact (high amplitude, low frequency) offers a far better opportunity at identifying weaker spots when compared to a wider roller (with lower amplitude) configuration.