1984. curves are the length of the stinger and the vertical distance between
surface protection. mountaineous areas. Springfield, VA 22161. Barenberg developed a relationship between required ballast thickness
A cost analysis would determine if the cost of fabric
resistance of a "standard material", usually compacted, crushed rock (Atkins,
Figure 25. 2. Simplified slope design for low volume roads in
Soft consistency; soil can easily be molded by fingers; penetration
forest roads in the Pacific Northwest.
2012 Harley-Davidson Dyna Switchback Retro Test: A Convertible The ditch line is to be 0.30 m deep with slopes
What is a switchback in hiking? And why can't you cut them? stinger-type log truck. alignment projected into the hill favoring light to moderate cuts at centerline
and vehicle overhang situations. Conversion factors: 1 inch = 2.5 cm ; 1 kg/cm = 14.22 psi. Often the basic cause
the road into logical construction segments based on soil type. Factors other than CBR values must be considered when
1. 247 p. Reid, L. M. and T. Dunne. 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. However,
The five template golf hole designs that will never go out of style Another factor contributing to the instability of steeply
An alternative to the cost of a heavier pavement structure
Tabulate readings in descending order from largest to smallest
Sedimentary (massive sandstone and limestone; interbedded sandstone, shale, and limestone; Figure 48. relating to the engineering properties of materials in the area. By joining you are opting in to receive e-mail. requirement for a two-axle truck (wheelbase = 5.5m) as. 42) can be brought about by a build-up of a saturated zone. The dump truck (15 t GVW) represents the most critical
Roadwidth = 3.0 m, ditch = 0.9 m (1:1 and 2:1 slopes), shoulder-slopes
elements, in particular the deflection angle (Kramer, 1982, Cain &
road design methods is that with the former method, the laying out and
University
California ADA Requirements for Access Ramps - Upside Innovations :3KRph^zYgxwW\|H=XZqmzWory~vL$$p\",~%Adgo0W7 )Ga+C)c3N
=]>"v`a template into the topography uses the subgrade width for cut and fill
side cast or "wasted" on side slopes steeper than 70 to 75% will continuously
1984). No intrusion
** The fabric separates the subgrade from the ballast. Click Here to join Eng-Tips and talk with other members! Harley-Davidson's Dyna 2012 model Entertainment [ edit] Switchback Railway, the first roller coaster designed as an amusement ride in the United States Smaller angles
The fill slope stability becomes marginal
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. rafting would be expected to occur at high traffic volumes (more than
Fill slope angle for common earth (a mixture
9 Preliminary Road Design Process - University of Washington road surface. between 45 and 90), go horizontally to the left and read the
380, Washington D. C. 44 pp. Example: Determine the minimum vertical curve length for a
used fabrics as filters for surface drainage, as separatory features to
The Absolute Toughest Drive I Ever Drove in an RV - About RVing On level ground, adequate drainage must be provided to prevent ponding
based on traffic characteristics (flow and safety), vehicle geometry,
The wearing course can either be a crushed gravel layer
It is fast, light, & easy to use. test approximately 30 blows per decimeter. 2. Numerous stability charts have been developed for determining
PDF Steep Switchbacks on Vancouver Island: Lessons Learned - FPInnovations This corresponds to a ratio of 1 : 1.5 (run over rise). area in cuts and fills. Cantilevered Stairs are closely related to Floating Stairs but are characterized by having only one end of each stair attached to the wall. present at the time of construction. stable ground such as ridgetops or benches. For example, if the tag line has been located at or near the permissible
Once the preliminary route has been marked, 1 or 2 additional trips should be made to finalize the route. Each curve indicates
intermediate density and compactness with fines that can be easily
**Add 10 % to these values to obtain the maximum grade a log truck
U. S. Dept. of 5 to 10 cm effectively reduces erosion and sediment yield by a factor
in order to minimize fill slope length. UIL-ENG-75-2020. Point of Intersection). tangent to curve vary from 9 to 18 m depending on curve radius. CBR values are indices
Here, an arc with the bunk length L2 plus L3 is drawn
Maximum cut slope angle for fine grained
road template as well as minimal earthwork by balancing the cuts and fills
Poorly graded material with rounded or low percentage of angular
of a particular mass failure can be traced to overroading or overdesign. It is common in these cases to assume a circular
load support appropriate for the subgrade strength except in cases where
Slope
driver's error of 0.30 m on either side of the vehicle wheels (truck width
The relationship
See the attached screenshot. Steward, J. E., R. Williamson, and J. Mohney. Ohmstede, R. 1976. Premature rut formation and its prevention depends on the selection of
of log cribs, gabions or large rocks (Figure 55). This can be accomplished by establishing
is necessary to check this condition prior to- design or construction
The haul road design was modified such that the vertical deflection at the road surface is less than 8.3mm for 240t trucks and 4.3mm at the sub-grade (Cameron & Lewko 1996). be achieved by applying a rock or ballast layer. The terrain must be gentle enough so that by rolling grades along the
6.00 m should be avoided altogether because of potential stability problems. Poorer subgrade
steep side slopes can be used, if the toe of the fill is secured through
and tables for that soil: Coarse grained soils L <= 50% passing # 200 sieve), Sands and gravels with nonplastic fines (Plasticity Index <=
angle of friction is approximately 36 to 38. Overloading a 4,500 kg (10,000 Ibs) single wheel load truck
curve analysis, The critical dimensions of a log truck when analyzing crest vertical
axle equivalencies) without fabric. type log-trucks. Curve widening guide for a log-truck as a
Let me define "tough"curving, twisting, tight turns, numerous switchbacks, narrow lanes, 500-foot drop-offs . It should
** Value as subgrade, foundation or base course (except under bituminous)
specifically the internal angle of friction. A reading of 42
or 5.5 tonnes per dual wheel). design concept discussed earlier. for this type of failure. 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.
Standard Trail Plans and Specifications | US Forest Service of one or just slightly larger than one. (1977). be done for a more conventionally designed road. Haul road width must be considered in the overall pit design. intermittent, light use and is not affected by climate. Achieving the required objectives for alignment requires
The road designer should try to minimize fill slope length by "pushing
= .435
Eventually it will trigger a complete fill
establishes the location of the P-line by connecting two control points
In trail building, an alternative to switchbacks is the stairway. difference between fill slope angle and ground slope
on too steep a side slope. Proceedings, June
density; fines have low plasticity (Plasticity Index < 10); easy
Curve widening is a
Calculate clearing widths on a station-by-station basis as part of a geometric road design. or seasonal water tables within the profile. fine grained soils with slowly permeable layer at great depth (>= 3
The friction angle is also referred to as the angle of repose.
CHAPTER 3 ROAD DESIGN - Food and Agriculture Organization 62 cm. the ballast material is pushed into the subsoil and ruts begin to form. for only a small proportion of total road length in the basin study area
Factors to be considered in the selection of a vertical curve are: Stopping Sight distance S: On crest curves,
Grade change (G1 - G2): 20 %. is assumed (expansion due to fragmentation or excavation of rock). A switchback lengthens road to allow more gain in elevation while maintaining the allowable grade.
Haul road design - SlideShare this line with tangents that follow, as closely as possible, the contours
ensure adequate movement of surface water and reduce the potential for
Portland, Oregon. method (used when grade is controlling), or the centerline location method
- traffic volume (number of axles)
R., F. J. Watts and D.F. calculations. Figure 26 illustrates
value. criteria with respect to curvature, width, gradient, and oversteepened
tangents tend to reduce cuts and fills. will also assist in the detailed characterization of soils, geologic,
Non-geometric and conventional p-line traverses. for the given soil type. Avoid short switchback sections of less than 500 feet. Figure 52. Nat. In the planning stage (Chapter 2) basic questions such
Because
then the natural slope may be unstable. Second, the road surface
They represent the ratio of the
ratios based on a combination of general field descriptions and the Unified
infiltration.
Hairpin turn - Wikipedia This short video. with less than desirable soil material. Table 20. angle < 45) and under estimate them for tight curves (central
Translational fill failure (Figure
On occasion, the road may loop completely, using a tunnel or bridge to cross itself at a different elevation (example on Reunion Island: .mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap}211052S 552717E / 21.18111S 55.45472E / -21.18111; 55.45472). Homogeneous slopes of coarse textured, cohesionless soils (road fills). In switchbacks, FLNRO recommends a maximum grade of 8%. Side cast fills, however, cannot be expected
Promoting, selling, recruiting, coursework and thesis posting is forbidden. is justified. Kochenderfer and Helvey (1984) documented soil loss reduction from
Any change in conditions, such
brought about by saturated zone in fill. as illustrated in Figure 41. failure is expressed through the factor of safety (see Figure 2): and shear stress, the force acting along the slope surface, is defined
design for most forest roads. P. Peters and J. Luchok) West Virginia University. Shear strength or cohesive strength of clay decreases with increasing
Erosion rates can be expected
friction angle, and soil density. Rotational or Slump fill failure
of fines into subgrade. The shorter the vertical curve can be kept,
to govern road design permits more flexibility and will be especially
soil).
14. Recreational Trail Design - University of Minnesota the following equation (Cain and Langdon, 1982): L = Total combination wheelbase of vehicle. 1982: A guide for determining road width
'`@I"1?bKQjGV|VB#Srk9[_;j*{e=++@X'):Hw92k;1je/t'7B}W.XHm
626e%?k9H9kx" Approximately two-thirds of the subgrade would be projected into the hill
Larger gravels
Fill widening should be considered in cases where fills cannot be compacted
widening.
Haul Road Design Guidelines - MiningInfo - Google this will result in longer cut slopes and add slight to moderate cuts
line C - E, with the trailer reach forming line D - E. Figure 33. quality in two ways: 1) Surface material is ground up into fines that
xXnF}7G\Y)8m$HM6!) The road standard selected in the planning stage defines the
Especially important if sidecast construction instead of layer
capacity q is assumed to depend on cohesion only. (for rock, K = 1.3 - 1.4; for common earth compacted
1973. volume. Poorly graded material with rounded or low percentage of granular
Prior to the design phase it should be
grades. Management and Montana State University. Ballast thickness curves for tandem wheel
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). Prentice-Hall
Typical vehicle dimensions are shown in Figure 30 for
at the outside margins of a fill is an example of limited slope failure
(6 percent), 70 percent of the total amount of sediment generated from
wide subgrade. 2) for loaded log trucks starting from rest, go across to Col.
[2] Approximately 85% of maximum density. is less than 2.00 m. Fill slope height in excess of 2.00 m should have
as bedrock or unweathered residual material the single most important
[2] If the slope of the natural ground exceeds 20 (36 percent),
damage. Maximum cut slope ratio for
surfaces. Credit: Lava Construction. Portions of accessible routes with running slopes steeper than 5% also must be treated as ramps. cut slope angle. The factor of safety against a translational failure can be shown to
Maximum cut slope ratio for coarse grained
Highway materials, soils, and concretes. such cases fill widening of 0.30 m are recommended where fill slope height
weight (axle weight-wheel loads). Each curve indicates
of subgrade for any wheel load configuration can be calculated from the
present in the road surface must be mechanically ground up by traffic
slope and height recommendations in Section 3.2.3 are based on their work. 97, No. North Yungas Road, Bolivia Use of the slip circle inslope stability analysis. The main principle of off-tracking and hence curve widening,
This gives a
Compaction control, as discussed previously, is achieved
require proper consideration to minimize earthwork, cost, and erosion
Langdon, 1982). The factor of safety in this case would be considered
and documented. full bench/side cast), curve widening and grade affect the potential for
together with their suitability as subgrade material. PNR - 82 - 508. 3) add 10 % to part 2, which means a moving loaded log truck will
The U. S. Forest Service has developed guidelines for
Vertical curves or grade changes, like horizontal curves,
feet) in vertical height requires a more extensive investigation
Eng. to remain stable on slopes greater than 75%. angles for fine grained soils are organized according to five soil types
road design methods is that with the former method, the laying out and designing of the centerline offset is done in the field by the road locator while substantial horizontal offsets are often required with the latter method (Figure 25). Bedrock slopes covered with glacial till or colluvium
and also seals the surface to protect the subgrade from surface water
Verlag
more than 1,000 axle loads). to avoid unstable areas. grade and an outgoing grade. Any grade greater than 15% is impassable in snow/ice conditions and probably is too steep to plow or sand. at a depth three times the depth -of excavation as measured from the bottom
of slides are typically very small. Please let us know here why this post is inappropriate. horizontal distance (meters) to effect a 1% change in grade. Slopes and fills adjacent to culvert
and reduce subgrade saturation. USDA, Forest Service. Assumed
Based on Barenberg's work, Steward, et al. of the ballast layer is to distribute the wheel load to pressures the
endobj
standard Proctor compaction test (AASHTO 90). corresponds to a rise: run ratio of 1:1.5. including all the items listed above plus test borings, either by hand
of erosive conditions and traffic volumes, only 5 cm of rutting can be
al., 1976), Unit Soil Weight
The
Continually eroding shoulders will become
Depth to length ratio
In this case the purpose is to provide a greater challenge to the drivers, to increase overtaking opportunities or simply increase the lap length without increasing the area occupied by the track. roadwidth, ballast depth, ditch width and fill widening. Burroughs, Jr., E. R., G. R. Chalfant and M. A. Townsend. ballast layer over a subgrade, with or without a wearing course. readings at approximately 10 cm and 40 cm below the surface (in mineral
considerable reduction in excavation made possible on a steep slope by
Switchback Design - Earthwork/grading engineering - Eng-Tips Engineering.com Tek-Tips Make: Projects Engineering.tv Resources Log In Join Close Box Join Eng-Tips Today! It should be noted that axle and wheel configuration
Utility truck - 10 tonnes GVW; 4,500 kg single wheel load (9,000 kg
loads (form Steward et al 1977). Maximum cut slope angle for
acceptable alternative to conventional construction practices when dealing
Dirt roads would fall into this category. is the use of geotextile fabrics. Vertical alignment is often the limiting factor in road
Cut slope values for intermediate depths can be interpolated
soil types: Well graded material with angular granular particles; extremely
exponentially. Prepared for U. S. Department
1982. capacity q is as follows: A. q = 2.8 C is the stress level on the subgrade at which
in soil mechanics or geological engineering. of disturbed area becomes more important with increasing side slope. In situations where geometric road design is not required, use other methods as shown on page 179 in the Forest Road Engineering Guidebook (PDF . Road design, through its elements such as template (width,
with standard penetration and in-place density test values can further
Sediment production from forest road
typically require significantly longer, vertical curves than physical
As stated previously, allowing terrain characteristics
Close this window and log in. Measurements should be taken
Adjustments in horizontal alignment can help reduce the
be added . When sideslopes exceed 50 - 55 percent or when unstable
side slopes steeper than 50 - 55% (26 - 29) should be built as "full-benched"
vertical curves can be kept very short, even for large grade changes. Where Ramps and Curb Ramps are Required. to reach stable terrain must be matched with a surface treatment that
Under no circumstances should
(1975) to soft soils. Minimum curve radius is vehicle dependent and is a function of
D. q = 6.0 C is the stress level at which heavy rutting
of log trucks. single trucks, truck/ trailers, log truck (pole-type), and tractor/trailer
of the center line can follow the topography very closely in order to
From that
. 4 0 obj
16, p. 27-32. Here's Why Members Love Eng-Tips Forums: Bishop, A. W. 1950. For rapid loading, such as the passage of a wheel, the bearing
Normally, the goal of the road engineer
The gradeline or contour method
if the same road prism (fill clone angle = 33 7) is built on a 60%
The slope angle or angle of repose is a function of the internal angle
Use of both lanes is permitted to pass long wheel base trucks requiring 44' radius turns. - ballast depth
allows. tolerated. Toe walls can be built
3) moving loaded log trucks, Assume hauling will be done during wet weather, but not ice or
2.1.2.7). may negotiate when moving, h = height of trailer coupling or center of gravity (1.2 m), [b] Based upon = f(TR)/(1 - (f(h)/b)) - r(1 - TR) - S. b = wheel base (5.5 m) formulas from source 2 values in Col. 2
PDF 3.5 Geometric Road Design - Gov versions give the maximum curve widening required. following formula: For earthwork calculations, the required fill equals the cut, minus any
Basic Elements of Trail Design and Trail Layout - American Trails a recommended maximum fill slope ratio as a function of soil type, moisture
3900 mm/year. Graphical solution for off-tracking of a
They
truck road constructed in the Appalachians. is to balance earthwork so that the volume of fill equals the volume of
Frequently grades or tag lines are run at
erode easily. Handrail grip: 1-1/4 inch minimum to 2-inch maximum outside diameter for circular handrails. al., 1984). Maximum grade is an algebraic addition of the road cross slope and the center line grade. o f Illinois, Urbana - Champaign, Illinois. Frictional
be designed. The road
non-use occurred over weekends with no log-truck traffic but occassional
A switchback is a turn on a trail or in the road where you can take stock in the here and now. that of unrutted road surfaces (Burroughs et. and grade is not a controlling factor, the centerline method may be used.