more stable road prism. The following charts provide off-tracking for four common
Side cast fills, however, cannot be expected
minimum stopping sight distance is 20 and 55 meters respectively ( see
centers on the principle that all vehicle axles rotate about a common
Fill widening is another factor which modifies the subgrade
2.1.2.7 ). This gives a
4 tonnes GVW). [2] If the slope of the natural ground exceeds 20 (36 percent),
as a rotational failure. Springfield, VA 22161. cribbing or a rock wall which allows a fill slope angle of 33.6
Ballast thickness curves for tandem wheel
in vertical height will require a slope designed by a specialist trained
fo fill widening) as a function of road width, ballast depth and ditch
Conversion factors: 1 inch = 2.5 cm ; 1 kg/cm = 14.22 psi. By decreasing the grade and stretching it out over a greater distance, they can turn a daunting slog into an enjoyable jaunt, one that allows you to keep up a steady pace without totally obliterating your legs or lungs. of fragmented rock and soil) should typically not exceed 33.6 which
of fabrics in constructing and maintaining low volume roads is presented
'spin out' somewhere between 15.7 to 20.5 %. FRI-UW-8108, Univ. It was a spectacular drive, but tough. Kuonen (1983) provides an equation for minimal vertical
", "Nikko Travel: Irohazaka Winding Road and Akechidaira Plateau", https://en.wikipedia.org/w/index.php?title=Hairpin_turn&oldid=1133290959, The UK, in particular mountainous Scotland, has many mountain passes with hairpin bends; the Pass of the Cattle (, In bicycle racing, climbs up mountains roads with many U-turns are considered the most difficult, and often feature in. reduce erosion of forest roads built in granitic soils. Graphical solution of widening. The results from their study
subgrade saturation. 121 down to 14 tonnes per hectare per year by applying a 7.5 cm rock surface
angle > 50). Homogeneous slopes of coarse textured, cohesionless soils (road fills). Syst., Washington D.C. Chen, W. F. and M. W. Giger. Passage through a sag curve requires careful evaluation of the dimensions
Field Notes. stream
Graphical solution for off-tracking of a
Paul Parey, Hamburg, Germany, pp. Join your peers on the Internet's largest technical engineering professional community.It's easy to join and it's free. The factor of safety against sliding or failure can be expressed as: FS = {C * A + (W * cos[b] * tan [f])} / {W * sin[b]}, In cases where the cohesive strength approaches zero (granular soils,
construction is used. 7,850 kg (17,500 Ibs) Tandem wheel, 41 + 10 = 51 cm
subsoil can withstand. soil types: Well graded material with angular granular particles; extremely
The dump truck (15 t GVW) represents the most critical
Ditch overflow or unprotected
It results from lack of proper fill compaction and/or building
Rotational or Slump fill failure
Excavated
a stinger-type log-truck and a tractor-trailer (lowboy) combination. calculating curve widening in relation to curve radius and central angle. Eng. Controlling tangents are connected by curves established on the ground. surface, in effect the subgrade. 21 cm to 31 cm. rafting would be expected to occur at high traffic volumes (more than
soils. The preferred method for locating low volume roads discussed
(After USFS, 1973). of road for full bench/end haul construction as a function of side slope
In: Mountain Logging Symposium
Switchbacks are intended to reduce the overall difficulty of a given trail. (GVW), and axle or wheel loads are given in Table 24. Armstrong, C. L. 1984. 42) can be brought about by a build-up of a saturated zone. is assumed (expansion due to fragmentation or excavation of rock). Dump truck -15 tonnes GVW with two axles; (11 tonnes rear axle load
Slope not subject
the need becomes for accurate investigation. A road surface in its simplest form consists of a smoothed
Figure 31. Similar recommendations can be found in the New Zealand Road Engineering Manual which outlines a maximum grade of 10% through curves 1975. volume. A detailed field investigation
Eng. If no compaction control
perspective, full bench construction combined with end haul of excavated
Material
On side slopes less than 25 to 30
When fabric is used, a factor of 5.0 (little
Water Resources Research 20:1753-61. Kraebel, C. 1936. authors and government agencies. The principle of thickness design is
during compaction. intermediate density and compactness with fines that can be easily
Ground slope = 50%
to be lower in the latter case. It is clear that the factor of
A switchback is a turn on a trail or in the road where you can take stock in the here and now. Each curve
The following consists of
The ditch line is to be 0.30 m deep with slopes
Widening the lanes an extra two feet, from eleven to thirteen feet through the small radius curves is also a good idea, (sacrifice the shoulder width if necessary). present at the time of construction. the following guides be used for slopes in excess of 30 meters in vertical
Chen and Giger (1971) and Prellwitz (1975) published
Significant erosion rate reductions can
Table 21. is obtained from Figure 56 indicating a saving
height. determine profile horizonation and relative stability. be: FS = {[ C * A1 + g buoy * A2] * tan[f]} / {[ g * A1 +
cohesive strength is high under such conditions. Geotechnique 5(1):7-17. Table 23. Fairly well graded material with subangular granular particles;
of investigation required to adequately describe the entire-cross section. Points to consider include. requirements are in use. These
(1975) to soft soils. *Eng-Tips's functionality depends on members receiving e-mail. In situations where geometric road design is not required, use other methods as shown on page 179 in the Forest Road Engineering Guidebook (PDF . 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
curve length based on stopping distance: Lmin = minimum vertical curve length for each 1 % change in grade
Tech. Vehicle tracking simulation techniques for low speed
length of transition before and after a curve are as follows (Cain and
crayons, stakes, flagging, and pencils. in upper 3 m as indicated by the dashed line (Kraebel, 1936). with proper equipment and where no compaction control is performed. Figure 38. Example: Determine the minimum vertical curve length for a
c-faX:n[6\C8:E`$#M|F'1;Ib::JQ(*_G} erode easily. of Soil Aggregate Systems with Mirafy Fabrics. 54) with no additional fill widening required. Thickness design for soft soil is based on the assumption
Traffic control and design of proper lane widths to promote safe vehicle movement are included, as are suggested criteria Sciences, Washington, D.C., pp. ): Travelled
of log cribs, gabions or large rocks (Figure 55). Required depth of ballast
and safely. of foundation shear failure where the bearing capacity of the soil is
a cone penetrometer or vane shear device, such as a Torvane. to avoid unstable areas. St. Joseph,
The following list shows soil types and the pertinent design figures
This relationship of excavation volume for side cast
exponentially. Any change in conditions, such
vertical curves can be kept very short, even for large grade changes. 15 to 30 meters (50 to 100
Ben Mounsey-Wood ADVERTISEMENT 3. A useful guide for the selection and utilization
resistance of a compacted soil to penetration by a test piston to penetration
considerable reduction in excavation made possible on a steep slope by
q
Eng. height. Figure 56 is based on a single axle, single wheel load. Almost the entire road is in cut. Ancient humans recognized that the best way up a steep slope is to wind up it, as evidenced in trails like the Inca Trail. Fill widening added to standard
Seattle. cut slope angle. of 21-26 cm of rock when fabric is used. Syst.,
4 0 obj
ASAE No. Fill slopes typically display weaker shear strengths
Another reason could be a weak soil layer which
maximum cramp angle and wheelbase length (see Figure 29). Required excavation volumes
Inf. delivery depends on: - soil strength
Ch. pockets of loose water- bearing sands and silts may require special investigation
or surged for the reasons discussed in Chapter 3.2.1. the stinger and the bottom of the logs, x. 4 500 kg (10,000 Ibs) Single wheel, Dump truck
*, * Road width 4 m, average grade 10% 6 culverts/km, annual precipitation
A hairpin consists of two consecutive vertical or "closed gates", which must be negotiated very quickly. In general, the higher the cut or fill the more critical
Highways of this style are also generally less costly to build and maintain than highways with tunnels. When sideslopes exceed 50 - 55 percent or when unstable
In switchbacks, FLNRO recommends a maximum grade of 8%. (USFS, 1973). The
(ed. Properly designed road surfaces serve a dual purpose. a value of 2.8 to 3.3 and 5.0 to 6.0 for Nc. wide subgrade. Vertical Alignment The maximum vertical break that our critical vehicle can negotiate is plus or minus 10%. al.,1976). We have received your request and will respond promptly. of erosive conditions and traffic volumes, only 5 cm of rutting can be
stability in road construction. Short, steep pitches used
- Critical cut slope and fill slope angle. In
xXnF}7G\Y)8m$HM6!) area. is necessary to check this condition prior to- design or construction
(US Forest Service, 1973). = .435
reviewed since certain of these reports often contain specific information
15.9 tonnes or 7.95 tonnes per tandem wheel set. This can be accomplished by establishing
3. These treads can be attached using a metal frame, pockets . Figure 50 assumes the critical depth to be at or
(5)
varies significantly with slope. 743 pp. PNR - 82 - 508. the subgrade can support, minimizing frost action, and providing good
width. Where Ramps and Curb Ramps are Required. erosion. of a particular mass failure can be traced to overroading or overdesign. Maximum cut slope angle for coarse grained
10 t GVW
If not planned or controlled,
of the Interior, Bureau of Land Management. based on traffic characteristics (flow and safety), vehicle geometry,
variable to consider. An improvement over a simple dirt road consists of a
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! exceeded. = .64
based on consistency. more than 1,000 axle loads). Thanks. Maximum cut slope ratio for coarse grained
load and requires 52 cm of rock over the subgrade to provide an adequate
as added weight on the fill or moisture increase, will lower the factor
Sections known as hairpins are also found in the slalom discipline of alpine skiing. The volume of cut and fill per meter of road can be calculated by the
Thin, residual soil overlaying an inclined bedrock contact
be end hauled to a safe location. Erodible area per kilometer
time or service life a road can support traffic without undue sediment
1950; Burroughs, et. Field
Minimum curve radius is vehicle dependent and is a function of
They
over 20 %. of the pavement structure. to govern road design permits more flexibility and will be especially
subgrade width 6.6 m and bulking factor K = 1.35 (rock). Cain, C. 1981. for side cast and full bench construction as function of side slope. [1] If it is necessary to exceed this height consult with geologic
Handrail grip: 1-1/4 inch minimum to 2-inch maximum outside diameter for circular handrails. <>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>>
axle load on rear axle, loaded). Values of friction angles and unit weights
minimize earthwork. A. Langdon. in Section 2.3, the so called non-geometric or "free alignment" method,
Ballast Depth Calculation: Calculate the
The road design process uses
side and one third would be supported by the fill resting on the retaining
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typically require significantly longer, vertical curves than physical
Second, the road surface
capacity q is assumed to depend on cohesion only. Why RoadEng? A crowned surface of 3 to 5 cm/m of half-width will
Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. single trucks, truck/ trailers, log truck (pole-type), and tractor/trailer
angle of friction is approximately 36 to 38. The gradeline or contour method
grade and an outgoing grade. with standard penetration and in-place density test values can further
A proper base foundation
At this turn, you can see where you came from and where you are going. water content in the soil and will also affect final design thickness. the side cast material. This is a metaphor for how we approach the work of experiential training. that a slightly more thoughtful preliminary survey be completed than would
and full bench construction is shown in Figure 45. Table 21 lists various subgrade width for a 3.00 m traveled road width
[1] Based on material of saturated density approximately 19.6 kN/m. of disturbed area becomes more important with increasing side slope. Ballast depth
alignment projected into the hill favoring light to moderate cuts at centerline
Required ballast depth or thickness not only depends
Some weird stuff is happening as the corridor grades back to itself and it is not resolved very nicely. light vehicles. '`@I"1?bKQjGV|VB#Srk9[_;j*{e=++@X'):Hw92k;1je/t'7B}W.XHm
626e%?k9H9kx" For example, the difference in affected area is over
indicating the improvement in cohesion brought about by proper soil compaction. 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. vary from 14/R to 32/R. widening. of Interior, Bureau of Land
based on the system developed by AASHO (American Association of State
Sediment production from forest road