Section 7: Setting the Rock Lands
Anchor: #i1007038Introduction
A rock land is the area covered, at the desired aggregate application rate, by one predetermined size truckload of aggregate. The area of the rock land is calculated in advance and marked either on the pavement with paint or on the side of the road with flags. Setting rock lands for strip/spot seal coat work is not necessary if less than one truckload of aggregate will be used in a particular area.
Anchor: #i1007049Purpose
The rock lands are usually set at the start of a project to help the contractor calibrate the spreader box and assure that the correct aggregate rate is being applied. If the aggregate runs out before reaching the marker at the end of the rock land, the rate is too heavy. If there is aggregate remaining at the end of the rock land, the rate is too light. This is based on the assumption that the truck is carrying the predetermined amount of aggregate.
Anchor: #i1007060Calculating the Length of Rock Land
The desired rate of aggregate application is specified as 1 cubic yard of aggregate for a given number of square yards of roadway, such as 1 CY/125 SY.
For example, assume that the lane to be sealed is 12 feet wide, and the haul truck is filled with 14 cubic yards of aggregate. The desired application rate is 1 CY/125 SY.
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Area of Rock Land |
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Length of Rock Land |
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Marking the Rock Lands
Using a calibrated Digital Measuring Instrument, start at the beginning of the first shot with the DMI set at zero. Drive down the roadway until the DMI reads the calculated length of rock land. Stop and mark the end of the rock land. Make certain that the markings for rock lands are a different color or are somehow distinguishable from the markings used for the asphalt shots. Reset the DMI at the end of each rock land, and repeat the process.