At the same time a ditch is prepared and the cut slope smoothed and rounded. The windrow should be compressed and the bottom part embedded 15 cm in the fill slope. Excavators are also more effective at ditching and installing culverts. Forest Service, Region 1 and University of Idaho, Moscow, Idaho. Three basic road prism construction methods.
Adequate compaction cannot be achieved with bulldozers alone. Typically, reference points are placed at points where the center line alignment can be easily re-established, such as points of curvature. Typically lift height should be about 30 cm and should not exceed 50 cm. Lift height should not exceed 50 cm. The road design should attempt to keep the mass balance points within these constraints. Fills across draws or creeks are especially critical since they may act as dams if the culvert should plug up. Actual excavation is started about 10 to 12 meters from the loader by cutting a blade-wide trench and drifting the material towards it.
Working platform or pioneer road just outside of planned road surface width. First pass with excavator, clearing logs and stumps from construction site. In ed Corcoran and Gill C. Plan construction activities for the dry season. This is especially true where organic layers are deep or considerable sidecast embankment or fills are planned.
This material can serve as a sediment filter strip and catch wall see Section 6. Bulldozers are a low-ground pressure machine and therefore are unsuitable for this process. Percent change in haul distance with respect to changes in grade are shown in Table 40. An obvious disadvantage is the potential for erosion of loose, unconsolidated side cast material. The machine starts at the top and in successive passes excavates down to the required grade.
Side cast construction is the preferred construction method for bulldozers. Average production rates for a medium sized bulldozer 12 - 16 tonnes constructing a 6 to 7 m wide subgrade. It is worth noting that production rates of manual labor for excavation work are generally 3. Because of their excellent placement control of excavated material, they are ideal machines for construction under difficult conditions. Costs of erosion control construction measures used on a forest road in the Silver Creek watershed in Idaho. It should be noted, however, that side cast material is not compacted.
Production rates achieved are expressed in percent of production on a 10 percent favorable grade with 30 m haul. A good construction practice to follow is to remove stumps that are within the construction width Figure 105, B to E. Significant quantities of organic materials are removed between B and E. Total cost, however, for a road expressed in cost per unit length may be very similar for side cast embankment and layered placement considering the fact that total excavation volume may be up to 35 percent less for the latter case. If pioneer roads are constructed, they are often built at the top of the construction width and are usually nothing more than a bull dozer trail.
It is unlikely that the travelled road width will be involved in fill failures. Once started, drainage installation should continue until completed. This machine basically operates by digging, swinging and depositing material. A road to be built by an operator whose only equipment is a bulldozer requires a different design than a road to be built by a contractor equipped with hydraulic excavator, scrapers, and bulldozer. Slope stakes are an effective way to insure compliance with the design standards and to keep soil disturbance to an absolute minimum. On steep slopes, bulldozers should only be used in combination with special construction techniques trench excavation, see Section 6. The road design should consider the following points when bulldozers are to be used for road construction.
The economic haul or push distance for a bulldozer with a straight blade is from 17 to 90 meters depending on grade. Only mineral soil, free of organic debris such as stumps, tree tops and humus should be used. In order to keep erosion during the construction phase to an absolute minimum, four elements must be considered. Table 38 lists common road construction equipment and their suitability for the different phases of road construction. Slash should be placed on the fill above the cull log.
Earth is side cast and then wasted rather than used to build up side cast fills. There are now indications that excavator production rates are higher than dozer production rates on slopes steeper than 50 percent. This is often the case when construction activities are under way at several locations. Side cast and wasting traditionally has been the most common construction method. The bucket of the excavator is much more effective at ripping than the dozer blade. Fill slope lengths can be shortened through the possibility of constructing a catch wall of boulders along the toe of the fill. Third pass, finishing subgrade and embankment fill over pioneer road.