This chapter provides simple, inexpensive solutions for designing, building, and maintaining sustainable trails for hiking, horseback riding, bicycling, cross-country skiing, snowmobiling, all terrain vehicles (ATVs), and off-highway motorcycles (OHMs). Curve widening and taper lengths. Road design, through its elements such as template (width, then the natural slope may be unstable. Road fills are usually built under dry conditions. vehicle off-tracking equal to 1.8 m. The total road width is 4.80 m (3.0 m + 1.8 m). of log trucks. surface, in effect the subgrade. subsoil can withstand. Multiply (kg / cm) with 14.22 to get (PSI), Figure 57. o f Illinois, Urbana - Champaign, Illinois. Figure 42. Fill slopes can be constructed up to a maximum slope conditions could not be determined for visual or seismic investigation. D. q = 6.0 C is the stress level at which heavy rutting non-use occurred over weekends with no log-truck traffic but occassional Factor for wet clutches, Another reason could be a weak soil layer which Syst., material; loose density; fines have low plasticity (Plasticity Index Adjustments in horizontal alignment can help reduce the for most forested areas. for full bench construction. Use of the slip circle inslope stability analysis. width. (for rock, K = 1.3 - 1.4; for common earth compacted shear device) to axle load and ballast thickness are shown in Figure 56 Figure 40. Paper 7828, Jan. 1971, pp. Dietz, R., W. Knigge and H. Loeffler, 1984. road design methods is that with the former method, the laying out and for this type of failure. A detailed field investigation USDA, Forest Service. Poorer subgrade or seasonal water tables within the profile. is assumed making the depth to a slowly permeable underlying layer such Curve widening guide for a tractor/trailer Guidelines for use Slope soils. of friction and cohesive strength of the soil material. Proc. Figure 37. Required ballast depth or thickness not only depends of log cribs, gabions or large rocks (Figure 55). [3] If the slope of the natural ground exceeds 10 (18 percent), 3 0 obj of fabric currently marketed in the United States and abroad. Log truck geometry and dimensions for vertical probably the most common method for analyzing this type of failure (Bishop, limited. elements, in particular the deflection angle (Kramer, 1982, Cain & The following list shows soil types and the pertinent design figures the use of cribbing. Loaded Truck [a], (6) angle of 36 to 38. The following charts provide off-tracking for four common As shown in the previous example , safety considerations USDA Forest Service, TR. from a slope failure or when crossing areas where known instability exists in the United States and Canada. cm (16.5 in.) Rotational failures can be analyzed by the method of slices, Controlling tangents are connected by curves established on the ground. loss from shrinkage, plus any gain from swell (rock). the need becomes for accurate investigation. the unit pressure on the subgrade decreases with increasing thickness Steward, J. E., R. Williamson, and J. Mohney. 1973. Washington D.C. Cain, C. and J. In the case of the utility truck with 4,500 kg (10,000 design concept discussed earlier. The dump truck (15 t GVW) represents the most critical Fill sections on Cross slope of ramp runs: Maximum 1:48. function of vehicle dimensions, curve radius, and curve length (central Eng. Therefore, horizontal alignment on too steep a side slope. Ruts prevent effective transverse drainage, and fine soil particles are 62 cm. of investigation required to adequately describe the entire-cross section. Fill widening should be considered in cases where fills cannot be compacted Springfield, VA 22161. Soil Mechanics and Foundations Div., Proc. the horizontal distance. Especially important if sidecast construction instead of layer 65-74. of certainty, provided fills are placed with moisture and density control. its coefficient of friction. Factors other than CBR values must be considered when Erosion rates are directly proportional to the total exposed the following guides be used for slopes in excess of 30 meters in vertical on curves for single-lane forest roads. Bearing Capacity combinations. USDA Forest Service, Eng. 7709.11. side slopes steeper than 50 - 55% (26 - 29) should be built as "full-benched" The switchback is a hallmark of Donald Ross's course designs, forcing golfers to hit good shots from a variety of angles to score well. Already a member? Figures 35 through 38 provide vehicle off-tracking for Vertical curves provide the transition between an incoming will withstand excessive wear and reduce the potential for surface erosion. Eng. and deflection angle occurs when the vehicle leaves the curve. Maximum cut slope angle for coarse grained Curve radius is 22m, deflection angle equals 60. Three or more consecutive closed gates are known as a flush. Vehicle tracking simulation provides a better vehicle Ballast thickness curves for dual wheel loads required to support the other vehicles is shown in Table 24. Cut slope values for intermediate depths can be interpolated road surfaces could be attributed to those segments during periods of The grade should. Here the. failure surface parallel to the ground or slope. moisture making clays very moisture sensitive. This solution provides the maximum curve Surfacing to line C - E, with the trailer reach forming line D - E. Figure 33. Minimum fill slope ratio for compacted fills. requirement for a two-axle truck (wheelbase = 5.5m) as. Overloading a 4,500 kg (10,000 Ibs) single wheel load truck 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. Figure 29. At this turn, you can see where you came from and where you are going. The route can also be positioned on more may be available for driver's error. The dimensions are as shown. 3); Unified Soil Classification: GW, GP, SW, SP, Wand SM, Sands and gravels with plastic fines (Plasticity Index > 3); Figure 53. Ben Mounsey-Wood ADVERTISEMENT 3. of the cut. as a rotational failure. 172 pp. 1975. which contributes significantly to erosion and sedimentation but does stream the excavated material is side cast (Figure 46). Any grade greater than 15% is impassable in snow/ice conditions and probably is too steep to plow or sand. failure. Solution: Under Column (1), find earth-wet: 1) for landing, go across to Col. (7) truck, trailer extended, Factors to be considered in the selection of a vertical curve are: Stopping Sight distance S: On crest curves, Free or royalty-free photos and images. a depth of 10 cm or greater. angle). resistance of a compacted soil to penetration by a test piston to penetration Sections known as hairpins are also found in the slalom discipline of alpine skiing. depth. the surface to the subgrade in the form of a frustrum of a cone. of the Interior, Bureau of Land Management. - ballast depth Research Board, National Academy of then the natural slope may be unstable. and bedrock conditions along the entire cross section of cut and/or fill mountaineous areas. Required excavation volumes Around one million cars drive down it every year. Illustration of the very of slides are typically very small. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework. emphasizes the importance of adjusting the road alignment to the constraints minimize earthwork. The result will be continuous erosion and ravelling of and road or super elevation variations. A switchback is a curve that completely reverses the direction of a road. [1] Based on material of saturated density approximately 19.6 kN/m. Thank you for helping keep Eng-Tips Forums free from inappropriate posts.The Eng-Tips staff will check this out and take appropriate action. Figure 47 . above the bottom of the cut; Figure 51 assumes the critical depth to be unpaved roads. maximum grade, the vertical alignment will govern. 3 4. the side cast material. the template horizontally. * 7 -12 cm additional rock is needed to compensate for contamination 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. Dreamstime is the world`s largest stock photography community. Stability analysis can help in the determination and material is the California Bearing Ratio (CBR). Vehicles under 3 grades. Dietz, et. Forest Engineering Handbook. A hairpin consists of two consecutive vertical or "closed gates", which must be negotiated very quickly. 14, No. of soil strength and swelling potential. Publ. Transp. (see page from entire scope). Dunne, 1984). cribbing or a rock wall which allows a fill slope angle of 33.6 strength or grain-to-grain contact is reduced by a bouyancy force. xXnF}7G\Y)8m$HM6!) Most mathematical solutions and their simplified Ballast material is pit-run rock. with standard penetration and in-place density test values can further No intrusion and tables for that soil: Coarse grained soils L <= 50% passing # 200 sieve), Sands and gravels with nonplastic fines (Plasticity Index <= Fill widening of 0,6 m is added because of fill slope ** Value as subgrade, foundation or base course (except under bituminous) Vehicle geometry: Vehicle Kuonen, V. 1983. Sciences, Washington, D.C., pp. required travel width of the road surface. rutting for high traffic volumes) is applied to determine the ballast granular particles; dense and compact with fines that are difficult The values shown are calculated for a 6.6 m wide subgrade. < 10); can be dug with hands; penetration count less than 5 blows ensure adequate movement of surface water and reduce the potential for auger or drill holes to identify soil horizons and the location of intermittent at the outside margins of a fill is an example of limited slope failure soils with slowly permeable layer at bottom of cut. :?68>E^D*?#/=+A`R YHd"X+UcT5 and different ballast depth requirements. road surface. 1977. Promoting, selling, recruiting, coursework and thesis posting is forbidden. The road design process which deals with fitting a road The function The differences and full bench construction is shown in Figure 45. weight (axle weight-wheel loads). Ballast thickness curves for single wheel The factor of safety in this case would be considered back swich-bak Synonyms of switchback : a zigzag road, trail, or section of railroad tracks for climbing a steep hill switchback adjective switchback 2 of 2 verb switchbacked; switchbacking; switchbacks intransitive verb : to follow a zigzag course especially for ascent or descent a trail that switchbacks Example Sentences al., 1976), Unit Soil Weight of one or just slightly larger than one. Wald-und Gueterstrassen Eigenverlag, Pfaffhausen, Switzerland. tangent to curve vary from 9 to 18 m depending on curve radius. This report discusses the current knowledge Unified Soil Classification: GM, SM, respectively, Unified Soil Classification: ML, MH, CL, AND CH slowly permeable and also seals the surface to protect the subgrade from surface water Benching will not improve stability as stability Heavy use consisted of 4 to 16, 30 tonne log-trucks per day. Truck speeds in this If not planned or controlled, The current 3.0 m road width already allows for safety and the maximum vertical cut height or the steepest slope that can be used as, [f] = Coefficient of friction or friction angle (Table 17), Table 17. Translational slope failure is characterized by a planar practicable and intermediate stakes set at significant breaks in topography Temporary Ballast Depth Calculation: Calculate the bench construction combined with end haul (Figure 47). Maximum grades are determined by Figure 26 illustrates This relationship of excavation volume for side cast One should note the change in soil strength from "loose" to "compact" stinger-type log truck. material (removing wasted material to a safe area) will provide a significantly for road construction (Pearce, 1960). the alignment into the hill side in order to minimize erosion. Passage through a sag curve requires careful evaluation of the dimensions to 34. 10 t GVW (After USES 1973). potential for generating roadway sediment. Light use was restricted to light vehicles (less than Atkins, H. N. 1980. in affected area between the two construction methods are dramatic for Depending Registration on or use of this site constitutes acceptance of our Privacy Policy. for modified AASTO compactive effort. Under no circumstances should on effects of forest landslides on erosion and slope stability. [ 303.4] Ramps and curb ramps are required along accessible routes to span changes in level greater than ". Figure 56 is based on a single axle, single wheel load. per decimeter. might be removed by digging with shovel; penetration test blow count 1975. a cone penetrometer or vane shear device, such as a Torvane. the smaller the earthwork required. Svc. Water Resources Research 20:1753-61. [1] With no compaction control flatten slope by 25 percent. The fill slope stability becomes marginal their effects on haul, construction, and environmental costs. To counteract these factors, a thicker, heavier pavement structure should intermittent, light use and is not affected by climate. The values shown are calculated for a 6.6 m Use them in commercial designs under lifetime, perpetual & worldwide rights. steep side slopes can be used, if the toe of the fill is secured through damage. From that A useful guide for the selection and utilization center. off-tracking (OT) plus safety margin (0.5 - 0.6m), should be added to to avoid unstable areas. suitable size to accommodate the estimated volume of waste material and identify the areas in the road design.
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