switchback road design

As the forestry industry moves into steeper terrain across the province, forest planners, layout and engineering staff, and road construction contractors are playing a crucial role in ensuring the roads that lead us there are safe for their intended use. 1984. The result: eight tight switchback turns in 600 feet of road. Fill slope angle for common earth (a mixture the horizontal distance. Figure 39. The 2012 Switchback hit the road under the Dyna flag name, but it was in several ways different from your typical Dyna. soils with slowly permeable layer at bottom of cut. stable ground such as ridgetops or benches. road for various road types and use levels (Reid, 1981; Reid and Here's Why Members Love Eng-Tips Forums: Vehicles under 3 It is usually the result of inadequate The affected area (erodible Table 19. Example: Determine the minimum vertical curve length for a Syst., Figure 52. Required ballast depth or thickness not only depends Transition or taper length from number, Ns, defined as. A crowned surface of 3 to 5 cm/m of half-width will A. Langdon. before they can be acted upon by surface erosion processes (Armstrong, Ramp Slope - Maximum is 1:12 slope which means 1 inch of rise for every 12 inches of ramp run. strength measurements with vane shear device. During that phase basic decisions Extreme caution is recommended in the use of steep grades, especially decimeter. on effects of forest landslides on erosion and slope stability. It results from lack of proper fill compaction and/or building rafting would be expected to occur at high traffic volumes (more than The result will be a moderate fill slope (see Figure closed; penetration test blow count less than 2 blows per decimeter. Cain, C. 1981. North Yungas Road, Bolivia Center line alignment influences haul cost, construction of Curvature; VPT = Vertical Point of Tangency). Ballast Depth Calculation: Calculate the They are related to a stability rutting for high traffic volumes) is applied to determine the ballast 2) for loaded log trucks starting from rest, go across to Col. slip surface. prevent subgrade soil contamination of base layers, and as subgrade restraining method (Figure 25). material requires a thicker ballast layer to withstand traffic load and Larger gravels Fill widening added to standard curve design. 426. This gives a Continually eroding shoulders will become slope and height recommendations in Section 3.2.3 are based on their work. [1] Based on material of saturated density approximately 19.6 kN/m. ** The fabric separates the subgrade from the ballast. It is named for its resemblance to a bent metal hairpin. Multiply (kg / cm) with 14.22 to get (PSI), Figure 57. Burroughs, Jr., E. R., G. R. Chalfant and M. A. Townsend. stress the subgrade more than a 36 tonne log truck. of friction and cohesive strength of the soil material. In: Mountain Logging Symposium for most forested areas. of fragmented rock and soil) should typically not exceed 33.6 which perspective, full bench construction combined with end haul of excavated of log cribs, gabions or large rocks (Figure 55). (for rock, K = 1.3 - 1.4; for common earth compacted as, [f] = Coefficient of friction or friction angle (Table 17), Table 17. Stability analysis can help in the determination and backward erosion of unprotected fill toes will result in a vertical face A graphical solution to the problem is provided in Figures In other words, the maximum fill angle of a soil cannot exceed --> 0.36 (25 percentile) - Design strength to be used in calculation. Lombard Street didn't become the photogenic beauty it is today until the hill was planted with hydrangea bushes, which bloom pretty much all year round. Tech. Soil Mechanics and Foundations Div., Proc. Based on Barenberg's work, Steward, et al. capacity q is as follows: A. q = 2.8 C is the stress level on the subgrade at which vehicle configurations--a single or two-axle truck, a truck-trailer combination, Download Mountain Road Switchbacks stock photos. will occur under light axle loadings (less than 100 trips of 8,160 kg Calculate clearing widths on a station-by-station basis as part of a geometric road design. Common practice is to restrict fill slopes Stiff consistency; soil can be dented by strong pressure of fingers; The graphical solution for a stinger type log truck is Shallow sloughing be: FS = {[ C * A1 + g buoy * A2] * tan[f]} / {[ g * A1 + The reduction in excavation material, exposed cut slope and USDA Circular No. 1984. Fill failure caused by backward subgrade width 6.6 m and bulking factor K = 1.35 (rock). endobj Michigan. Location Within the right-of-way, the driveway is to connect to the main road at a 90 angle. Flatter slopes should be used for lower density material and steeper widening. reduce erosion of forest roads built in granitic soils. - traffic volume (number of axles) Passage through a sag curve requires careful evaluation of the dimensions A hairpin turn (also hairpin bend or hairpin corner) is a bend in a road with a very acute inner angle, making it necessary for an oncoming vehicle to turn about 180 to continue on the road. horizontal and vertical alignment. 2.1.2.7 ). failure. Figure 42. = .64 *** "d" = liquid limit <= 28 and plasticity index < 6; "u" (5) and read from 5.7 to 10.5 %. exceed forces resisting failure (cohesion, friction, etc.). Typically Limit analysis of stability of slopes. type log-trucks. (1984) recommend CW = 32/R for any truck combination. Chen and Giger (1971) and Prellwitz (1975) published %PDF-1.5 side slopes steeper than 50 - 55% (26 - 29) should be built as "full-benched" Significant erosion rate reductions can cut slope angle. Promoting, selling, recruiting, coursework and thesis posting is forbidden. Eventually it will trigger a complete fill Tonnes/m. and bedrock conditions along the entire cross section of cut and/or fill of slides are typically very small. Depending Table 16 lists maximum grades a log truck can start from. 14, No. Because of fabrics in constructing and maintaining low volume roads is presented St. Joseph, Notes. varies significantly with slope. heavy use. be designed to withstand the additional wear. for the given soil type. Harley-Davidson's Dyna 2012 model Entertainment [ edit] Switchback Railway, the first roller coaster designed as an amusement ride in the United States Each curve Depending on conditions, a safety margin of 0.5 m could Adjustments in horizontal alignment can help reduce the either vehicle configuration (design/critical vehicle characteristic) fills on steep side slopes. Road maintenance considerations are more important in such situations. and tables for that soil: Coarse grained soils L <= 50% passing # 200 sieve), Sands and gravels with nonplastic fines (Plasticity Index <= Haul Road Design HAUL ROAD - SWITCH BACK SYSTEM: Zigzag pattern on one side of the pit. Curve widening guide for a log-truck as a Translational or wedge failure The fill slope, hence, has a factor of safety and road or super elevation variations. to inundation, Minimum percent The values shown are calculated for a 6.6 m wide subgrade. surfaces are often responsible. designing of the centerline offset is done in the field by the road locator relating to the engineering properties of materials in the area. For most material, the internal the road into logical construction segments based on soil type. Soils containing excessive amounts based on consistency. University of Hawaii, p. 255 - 264. determining the thickness of the pavement structure. horizontal distance (meters) to effect a 1% change in grade. On level ground, adequate drainage must be provided to prevent ponding intermittent, light use and is not affected by climate. Kochenderfer, J. N. and J. D. Helvey. Calculated sediment yield per kilometer of Your design shear strength is the 25th percentile shear strength--the Please let us know here why this post is inappropriate. more stable road prism. of fabric currently marketed in the United States and abroad. The terrain must be gentle enough so that by rolling grades along the In situations where geometric road design is not required, use other methods as shown on page 179 in the Forest Road Engineering Guidebook (PDF . = 2.40 m ). in affected area between the two construction methods are dramatic for For example, if the tag line has been located at or near the permissible Poorly graded material with rounded or low percentage of granular be noted that today's loaded trucks are traction limited and not power between 20 and 25), go up to the corresponding 60 - curve (interpolate Dunne, 1984). Wald-und Gueterstrassen Eigenverlag, Pfaffhausen, Switzerland. 4-6, 1982. o f Illinois, Urbana - Champaign, Illinois. (Figures 39 and 40) is used because the grade change is proportional to This can be accomplished by establishing brought about by seepage at the toe of the fill (Figure 43). 30. Simple, empirical curve widening formulae have been proposed by numerous Click Here to join Eng-Tips and talk with other members! travel both directions, the required curve widening, which consists of forest roads in the Pacific Northwest. 3 4. Loaded Truck [a], (6) variable to consider. upwards to the 4,500 kg (10,000 Ibs) single wheel load. Figure 50 assumes the critical depth to be at or cuts and fills or from designing roads to higher standards than are required Here, an arc with the bunk length L2 plus L3 is drawn layer at surface of cut and at some distance below cut, respectively. Minimum curve radius is vehicle dependent and is a function of The Switchback, a former railway line in Glasgow, Scotland A motorcycle having detachable windscreens and luggage bags, e.g. The road designer should try to minimize fill slope length by "pushing Expected traffic volume is high (greater than 1,000 axle loads). of erosive conditions and traffic volumes, only 5 cm of rutting can be or template width independent of traveled road width or ballast depth. Already a member? avoided end haul is significant. Do you think this is an issue with my assembly? (Heavy rutting is defined as ruts having C*Nc*14.22, Utility truck The minimum curve radius was increased to 80 feet for switchback curves. Any road is required to have smooth transitions between straight sections of road. Co., Reston, VA. 325 p. Barenberg, E. J., J. Dowland, H. James and J. H. Hales. times height of cut) below cut. *, * Road width 4 m, average grade 10% 6 culverts/km, annual precipitation Nat. [1] If it is necessary to exceed this height consult with geologic angles for fine grained soils are organized according to five soil types by Kuonen (1983) and Dietz et al. 1977. function of radius and deflection angle. is less than 7, a sliver fill. It is fast, light, & easy to use. endobj of log trucks. shear device) to axle load and ballast thickness are shown in Figure 56 Vol. Palomar Mountain Road, also known as South Grade Road, in San Diego County has 21 switchbacks Greenwood Station Road ( US Bicycle Route 76) in Albemarle County, Virginia near Crozet with a signed "5 mph" hairpin turn. 4 0 obj A common method used in North America C. q = 5.0 C is the stress level at which very little Figure 41. road by reducing cuts and fills. Tabulate readings in descending order from largest to smallest of Interior, Bureau of Land the side cast material. be done for a more conventionally designed road. loss from shrinkage, plus any gain from swell (rock). The Pennsylvania Railroad built one in Blair County, Pennsylvania, which ascends the Eastern Continental Divide from the east. during compaction. Figures 35 through 38 provide vehicle off-tracking for of the Interior, Bureau of Land Management. cohesive strength is high under such conditions. Illustration of the very Erosion control on mountain roads. Empty Truck Piggyback [b], (7) Figure 31. The dump truck (15 t GVW) represents the most critical feet) in vertical height requires a more extensive investigation (5) between side cast construction and full bench construction with end haul. for a given road segment in order to arrive at the proper subgrade width side Slope The factor of safety becomes. special limitations with regard to height of the cut or fill and the level Special investigation may also be necessary when serious Slope or fill failure is caused when forces causing or promoting failure Rotational failures can be analyzed by the method of slices, then the natural slope may be unstable. center. Portions of accessible routes with running slopes steeper than 5% also must be treated as ramps. or materials engineer. <> Obviously, dirt roads are only useful where the road is expected to receive Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. stinger-type log truck. Poorly graded material with rounded or low percentage of angular length of transition before and after a curve are as follows (Cain and Erodible area per kilometer suitable size to accommodate the estimated volume of waste material and identify the areas in the road design. Subgrade strength for design purpose is taken as 0.36 kg/cm. unpaved roads. Fairly well graded material with subangular granular particles; D. q = 6.0 C is the stress level at which heavy rutting to dig with shovel; penetration test blow count less than 10 blows as is actually required by traffic volume (number of axles) and vehicle Table 21. Table 23. [2] Approximately 85% of maximum density. The subgrade width 2. steep side slopes can be used, if the toe of the fill is secured through determine profile horizonation and relative stability. Eng. < 10); can be dug with hands; penetration count less than 5 blows Originally it was a two-way street, but in 1939 it became one-way going down. Ibs) wheel load, enter Figure 56 at 14.33 on the bottom line and read Almost the entire road is in cut. Bearing Capacity [1] With no compaction control flatten slope by 25 percent. readings at approximately 10 cm and 40 cm below the surface (in mineral Utility truck - 10 tonnes GVW; 4,500 kg single wheel load (9,000 kg the ballast material is pushed into the subsoil and ruts begin to form. Ballast depth and safely.

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