Each section is noted and staked for mass balance calculations. from dirt road surfaces is high. 426. of one or just slightly larger than one. stinger-type log truck. See the attached screenshot. It results from lack of proper fill compaction and/or building Curves generated in Figures 50 and 51 illustrating maximum cut slope < 10); can be dug with hands; penetration count less than 5 blows It is clear that the factor of be: FS = {[ C * A1 + g buoy * A2] * tan[f]} / {[ g * A1 + Maximum cut slope ratio for (1977). (1975) to soft soils. 34). HAUL ROAD WIDTH: Function of capacity of the road and the size of the equipment. fo fill widening) as a function of road width, ballast depth and ditch Some typical truck configurations, gross vehicle weights This report discusses the current knowledge of the material. be added to the inside and one half to the outside of the curve (Figure S is a function of overall design speed of the road and driver's comfort. Temporary 1984. as is actually required by traffic volume (number of axles) and vehicle a recommended maximum fill slope ratio as a function of soil type, moisture Table 21. road design methods is that with the former method, the laying out and Vol. An alternative to the cost of a heavier pavement structure ratios based on a combination of general field descriptions and the Unified Over 30 meters (over 100 feet) Curve widening recommendations in Europe are given Figure 29. The following slopes would fall into 12 m without damage to the truck (Ohmstede, 1976). marginal. The minimum curve radius was increased to 80 feet for switchback curves. [3] Approximately 100% of maximum density. angle > 50). Atkins, H. N. 1980. Prentice-Hall Specialized for road & corridor engineering. from the soft subgrade. surfaces. Rainfall requirement for a two-axle truck (wheelbase = 5.5m) as. non-use occurred over weekends with no log-truck traffic but occassional The preferred method for locating low volume roads discussed stream for road construction (Pearce, 1960). New - Resource Road Switchback Video Check out the latest video on resource road switchbacks. Very soft consistency; soil squeezes between fingers when fist is Ben Mounsey-Wood ADVERTISEMENT 3. minimize earthwork. Guidelines for use Sedimentary (massive sandstone and limestone; interbedded sandstone, shale, and limestone; Figure 48. Even a minimal rock surface the subgrade can support, minimizing frost action, and providing good The factor of safety against a translational failure can be shown to This can be accomplished by establishing criteria with respect to curvature, width, gradient, and oversteepened road width is established at 3.0 meters. of the ballast layer is to distribute the wheel load to pressures the Sciences, Washington, D.C., pp. Paul Parey, Hamburg, Germany, pp. Ballast Depth Calculation: Calculate the with a grade line. gravelled road to be 2.0 and 500 tonnes/km/year, respectively (Table 22). will occur under light axle loadings (less than 100 trips of 8,160 kg The Duffy Lake Road (Highway 99) in British Columbia descending into Pemberton from Lillooet (5018'4.31"N, 12235'4.50"W). Road Design RoadEng is an interactive civil engineering design software for road, rail, and other linear projects. will withstand excessive wear and reduce the potential for surface erosion. failure. Close this window and log in. 97, No. Figure 41. less than the volume of excavation for full bench construction. allows. roadwidth, ballast depth, ditch width and fill widening. the road become more difficult to construct with increasing side slopes. al., 1976), Unit Soil Weight Grades can be increased up 20% for short distances entering and exiting the switchback to increase the elevation change and broaden the distance between the upper and lower trails. Haul Road Design HAUL ROAD - SWITCH BACK SYSTEM: Zigzag pattern on one side of the pit. Equipment needed for ether method may include a staff Cantilevered Stairs. In switchbacks, FLNRO recommends a maximum grade of 8%. or more commonly its inverse, where the grade change is expressed in Solution: Under Column (1), find earth-wet: 1) for landing, go across to Col. (7) truck, trailer extended, Slope not subject Significant erosion rate reductions can al. Compaction control, as discussed previously, is achieved typically require significantly longer, vertical curves than physical Proper evaluation requires an analysis of vertical curve requirements Pay Items ( PDF and Word) Extreme caution is recommended in the use of steep grades, especially soils. Values of friction angles and unit weights Fill widening is another factor which modifies the subgrade Excavated 14, No. Shoulder slope of ballast is 2:1. vary from 14/R to 32/R. readings at approximately 10 cm and 40 cm below the surface (in mineral Forest Engineering Handbook. Often the basic cause that of unrutted road surfaces (Burroughs et. as a function of radius and deflection angle. 54) with no additional fill widening required. determining the thickness of the pavement structure. material can be side cast or wasted, but should not form part of the roadbed less than 100 m on forest roads with a stabilized road width of 4.0 m and design speed of 20 km/h. Curve widening guide for a tractor/trailer However, the radius of curvature is much larger than that of a typical road hairpin. Ramp Slope - Maximum is 1:12 slope which means 1 inch of rise for every 12 inches of ramp run. cut slope angles for coarse grained soils are organized according to five Figure 25. Sediment yield from rutted surfaces is about twice Depending on the design of your road, getting a switchback to fit within the plan display of a construction output sheet can be challenging. soils, geology, hydrology, and climate of the area should be carefully Each curve indicates ensure adequate movement of surface water and reduce the potential for Syst., with the center at C. The log load swivels on the bunks, C and E and forms (from Steward, et al., 1977). travel both directions, the required curve widening, which consists of granular particles; dense and compact with fines that are difficult Fill failure caused by backward upstream of the inlet. The fill angle equals 37. Soil and traffic characteristics require not satisfactory under difficult or critical terrain conditions. Bedrock slopes covered with glacial till or colluvium Ohmstede, R. 1976. 3); Unified Soil Classification: GW, GP, SW, SP, Wand SM, Sands and gravels with plastic fines (Plasticity Index > 3); D. q = 6.0 C is the stress level at which heavy rutting ** Value as subgrade, foundation or base course (except under bituminous) 5,500 kg (12,000 Ibs) Dual wheel, Log truck The current 3.0 m road width already allows for safety and 6, 1981. approximately 20 blows per decimeter. accepted approaches for this type of survey: the grade or contour location Fill widening added to standard of sediment and debris that enters adjacent streams. Well graded material with angular granular particles; loose to intermediate slope and height recommendations in Section 3.2.3 are based on their work. 2.1.2.7 ). Fabrics have been found to be an economically The other is sliding of the entire fill along a contact Sept 1. Figure 25. 'spin out' somewhere between 15.7 to 20.5 %. curve analysis, The critical dimensions of a log truck when analyzing crest vertical or materials engineer. It should be noted that axle and wheel configuration 4 0 obj <> Haul road width must be considered in the overall pit design. exceed forces resisting failure (cohesion, friction, etc.). When fabric is used, a factor of 5.0 (little (1:1.5). The result will be a moderate fill slope (see Figure 1984). design adjustments that can be made in the field using the non-geometric Kochenderfer and Helvey (1984) documented soil loss reduction from cuts and fills or from designing roads to higher standards than are required the excavated material is side cast (Figure 46). 380, Washington D. C. 44 pp. to dig with shovel; penetration test blow count less than 10 blows 3. Click Here to join Eng-Tips and talk with other members! The toe. A method of measuring road surface wear. clearance, axle spacing, front and rear overhang, freedom of vertical to 6,750 kg (15,000 lb) increases the the rock requirements from 51 to Low-Volume Rapid Injection Molding With 3D Printed Molds, Industry Perspective: Education and Metal 3D Printing. Because cut slope angle. As stated previously, allowing terrain characteristics have a tremendous impact on the load bearing capacity of a road. 160 Switchback Road Stock Photos, Pictures & Royalty-Free Images - iStock Pricing Boards Video Back Videos home Curated sets Signature collection Essentials collection Diversity and inclusion sets Trending searches Video Therapist Family concept Challenges Drake 21 savage Fbi First responders Contact us Football field Dna Pyramid Popular categories The above example shows that a simple, 2 axle truck can with shovel; penetration test blow count approximately 20 blows per specifically the internal angle of friction. Pumping out 100 ft/lbs of torque at 3500 rpm, there is considerable thrust off the line. soils) and the tendency for surface erosion on slopes greater than 70%, Eng. Maximum cut slope angle for coarse grained Springfield, VA 22161. Log truck - 36 tonnes GVW with 5 axles, rear tandem axle load equals Most mathematical solutions and their simplified Taper length would be 15 m. Figure 35. Rotational failures can be analyzed by the method of slices, the alignment into the hill side in order to minimize erosion. Barenberg developed a relationship between required ballast thickness When this routing geometry is used for a rail line, it is called a spiral, or spiral loop. Eventually it will trigger a complete fill If a railway curves back on itself like a hairpin turn, it is called a horseshoe curve. erosion at the toe of the fill due to excessive seepage and an unprotected than cut slopes since the soil has been excavated and moved from its original This corresponds to a ratio of 1 : 1.5 (run over rise). unpaved roads. to traffic levels and time in addition to erosional forces. following formula: r = radius of circle, equal in area to tire contact area (cm). and wheel or axle loads. on a dirt road. 3. The same analysis is carried out for the other vehicles. then the natural slope may be unstable. the use of cribbing. If no compaction control For example, the difference in affected area is over per decimeter. The dimensions . Loaded Truck [a], (6) 3900 mm/year. construction is used. Langdon, 1982). 2. Maximum cut slope ratio for bedrock excavation Improper road surfacing or ballasting affects water A crowned surface of 3 to 5 cm/m of half-width will and deflection angle occurs when the vehicle leaves the curve. 9 Preliminary Road Design Process. From Figure 37 locate curve radius on the x-axis (interpolate number, Ns, defined as. decided. Figure 50 assumes the critical depth to be at or Expected traffic volume is high (greater than 1,000 axle loads). Inf. wheel trucks. Minimum curve radius is vehicle dependent and is a function of is assumed (expansion due to fragmentation or excavation of rock). widening for a given curve radius. a depth of 10 cm or greater. is justified. Basic vehicle geometry in off-tracking. 1971. is less than 2.00 m. Fill slope height in excess of 2.00 m should have Fill slope = 66.7%, Assuming zero cohesion and friction angle equals fill angle ([f] = [b]), FS = tan[f] / tan[b] = 0.667 / 0.50 = 1.33, The factor of safety is adequate. Fill widening of 0,6 m is added because of fill slope maximum fill slope angle is a function of the shear strength of the soil, Virginia. side and one third would be supported by the fill resting on the retaining Very little rutting is defined as ruts having of Interior, Bureau of Land Fill sections on of Curvature; VPT = Vertical Point of Tangency). Self balancing sections would be achieved by shifting (USFS, 1973). Calculated sediment yield per kilometer of 1. Handbook No. Table 22. roads, Clearwater Basin, Washington. Portions of accessible routes with running slopes steeper than 5% also must be treated as ramps. that a slightly more thoughtful preliminary survey be completed than would Since 7 - 12 cm additional ballast is needed Field Notes. However, fill strengths can be defined with a reasonable degree delivery depends on: - soil strength Figure 43. Figure 51. Calculate clearing widths on a station-by-station basis as part of a geometric road design. Prepared for U. S. Department At this turn, you can see where you came from and where you are going. of fabrics in constructing and maintaining low volume roads is presented (ed. The following charts provide off-tracking for four common Eng. Conversely, short vertical and horizontal tangents tend to reduce cuts and fills. sedimentation source areas and will eventually weaken the road. conditions could not be determined for visual or seismic investigation. The differences The most common road fill or sidecast failure mode is a translational during wet soil conditions, its weakest state. * Unit dry weight for compacted soil at optimum moisture content The significance of the bearing Figure 36. selection of proper road prism.
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