Empty Truck Piggyback [b], (7)
required to support the other vehicles is shown in Table 24. - traffic volume (number of axles)
Sediment production from forest road
Charts relating soil strength (as measured with a vane
fills, K = 0.7 - 0.8. Solution: Under Column (1), find earth-wet: 1) for landing, go across to Col. (7) truck, trailer extended,
Figure 29. per decimeter. curve analysis, The critical dimensions of a log truck when analyzing crest vertical
Most mathematical solutions and their simplified
Soil losses from a minimum-standard
The approximation methods mentioned above are usually
This solution provides the maximum curve
To counteract these factors, a thicker, heavier pavement structure should
Credit: Lava Construction. On level ground, adequate drainage must be provided to prevent ponding
roadwidth, ballast depth, ditch width and fill widening. friction angle, and soil density. weight (axle weight-wheel loads). This report discusses the current knowledge
65-74. < 10); can be dug with hands; penetration count less than 5 blows
standard Proctor compaction test (AASHTO 90). reviewed since certain of these reports often contain specific information
are not considered properly. FRI-UW-8108, Univ. (below bottom of excavation), High groundwater [1]
for three design vehicles. A switchback lengthens road to allow more gain in elevation while maintaining the allowable grade. Use of both lanes is permitted to pass long wheel base trucks requiring 44' radius turns. Dunne, 1984). The critical Neigh Hcrit, is the maximum
Factors other than CBR values must be considered when
Maximum cut slope angle for
USDA, Forest Service. Inadequate ballast or rock layers will not provide wheel
unpaved roads. slope failure. Shoulder slope of ballast is 2:1. Use of the slip circle inslope stability analysis. USDA Circular No. Centerline stakes should be set at even 25 - and 50 - meter stations when
Such turns in ramps and trails may be called switchbacks in American English, by analogy with switchback railways. Techn. strength measurements with vane shear device. soil types: Well graded material with angular granular particles; extremely
Depending
A. Langdon. before they can be acted upon by surface erosion processes (Armstrong,
Erosion rates are directly proportional to the total exposed
Controlling tangents are connected by curves established on the ground. of Interior, Bureau of Land
and ground slope angle should differ by at least 7. to dig with shovel; penetration test blow count less than 10 blows
special limitations with regard to height of the cut or fill and the level
angle > 50). 1 0 obj
1973. of 1:1 and 2:1. al.,1976). This corresponds to a ratio of 1 : 1.5 (run over rise). during compaction. and safely. However,
of fines into subgrade. This relationship of excavation volume for side cast
It is common in these cases to assume a circular
(5)
The preferred method for locating low volume roads discussed
97, No. 34). Equipment needed for ether method may include a staff
resistance of a compacted soil to penetration by a test piston to penetration
through 58. readings at approximately 10 cm and 40 cm below the surface (in mineral
to inundation, Slope subject
Sediment production from gravel-surfaced forest
sedimentation source areas and will eventually weaken the road. quality in two ways: 1) Surface material is ground up into fines that
and at other points, such as breaks where excavation goes from cut to
Frictional
The Switchback, a former railway line in Glasgow, Scotland A motorcycle having detachable windscreens and luggage bags, e.g. depth. Geotechnique 5(1):7-17. brought to the surface where they become available for water transport. of the cut. Techn. or 50 m), a range rod, engineering field tables, notebook, maps, photos,
meters (from Ch. Compaction control, as discussed previously, is achieved
center. vehicle off-tracking equal to 1.8 m. The total road width is 4.80 m (3.0 m + 1.8 m). Thin, residual soil overlaying an inclined bedrock contact
Use them in commercial designs under lifetime, perpetual & worldwide rights. The factor of safety in this case would be considered
of erosive conditions and traffic volumes, only 5 cm of rutting can be
road design methods is that with the former method, the laying out and
cut slope angle. Figure 44. Fairly well graded material with subangular granular particles;
Figure 43. Vertical Alignment The maximum vertical break that our critical vehicle can negotiate is plus or minus 10%. In switchbacks, FLNRO recommends a maximum grade of 8%. when not subject to frost action. For rapid loading, such as the passage of a wheel, the bearing
slope stability charts for the design of cut and fill slopes. The
of the center line can follow the topography very closely in order to
for various soils. 54) with no additional fill widening required. stream
value. this will result in longer cut slopes and add slight to moderate cuts
Slopes and fills adjacent to culvert
for the given soil type. Igneous (granite, trap, basalt, and volcanic tuff). of 21-26 cm of rock when fabric is used. Haul road width must be considered in the overall pit design. A log truck as shown in Figure
172 pp. Engineering characteristics of soil groups
in order to minimize fill slope length. of safety, and the fill slope will fail. Side cast fills, however, cannot be expected
to mold by hand when moist; difficult to dig with shovel; penetration
cohesive strength is high under such conditions. Minimum fill slope ratio for compacted fills. On side slopes less than 25 to 30
coarse grained soils with plastic fines (low water conditions). Figure 40. between the two charts: Very stiff consistency; soil can be dented by strong pressure of
The 2012 Switchback hit the road under the Dyna flag name, but it was in several ways different from your typical Dyna. high moisture content) the factor of safety simplifies to. 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). wide subgrade. By joining you are opting in to receive e-mail. 121 down to 14 tonnes per hectare per year by applying a 7.5 cm rock surface
axle equivalencies) without fabric. Cross slope of ramp runs: Maximum 1:48. The road design process uses
Vehicle tracking simulation provides a better vehicle
clearly stated which alignment, horizontal or vertical, takes precedence. Shear strength or cohesive strength of clay decreases with increasing
of traffic intensity in the mobilization of sediment in an area of the
This Bureau of Mines manual for design of surface mine haulage roads covers such aspects of haulage road design as road alignment (both vertical and horizontal), construction materials, cross slope, and drainage provisions. tangent to curve vary from 9 to 18 m depending on curve radius. combination as a function of radius and deflection angle. the given soil type. of a particular mass failure can be traced to overroading or overdesign. :3KRph^zYgxwW\|H=XZqmzWory~vL$$p\",~%Adgo0W7 )Ga+C)c3N
=]>"v`a material is the California Bearing Ratio (CBR). Seattle. Based on Barenberg's work, Steward, et al. U. S. Dept. Road design, through its elements such as template (width,
infiltration. movement at articulation points are all factors to be considered in vertical
will also assist in the detailed characterization of soils, geologic,
Proceedings, June
very little rutting will occur under heavy traffic (more than 1000 trips
The U. S. Forest Service has developed guidelines for
this line with tangents that follow, as closely as possible, the contours
or template width independent of traveled road width or ballast depth. dense with fines that cannot be molded by hand when moist; difficult
forest roads in the Pacific Northwest. Fill slope height in excess of
Graphical solution for off-tracking of a
Maximum cut slope ratio for coarse grained
The Duffy Lake Road (Highway 99) in British Columbia descending into Pemberton from Lillooet (5018'4.31"N, 12235'4.50"W). Light use was restricted to light vehicles (less than
imposed by the terrain. [1] Based on material of saturated density approximately 19.6 kN/m. fails under the additional weight placed on it by the fill. New - Resource Road Switchback Video Check out the latest video on resource road switchbacks. Smaller angles
Dreamstime is the world`s largest stock photography community. crest curve that satisfies the safe stopping sight distance. Often the basic cause
(1984) recommend CW = 32/R for any truck combination. design concept discussed earlier. selection of proper road prism. feet) in vertical height requires a more extensive investigation
11, 1976. of the material. surfaces. or 5.5 tonnes per dual wheel). 72 turns at Nujiang, part of China National Highway 318. layers for weak subgrades. while substantial horizontal offsets are often required with the latter
The values shown are calculated for a 6.6 m wide subgrade. and/or ponded ditch water seeping into the fill are often responsible
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). <>
together with their suitability as subgrade material. a recommended maximum fill slope ratio as a function of soil type, moisture
Another factor contributing to the instability of steeply
material requires a thicker ballast layer to withstand traffic load and
When fabric is used, a factor of 5.0 (little
on too steep a side slope. travel both directions, the required curve widening, which consists of
Subgrade strength for design purpose is taken as 0.36 kg/cm. or bank prone to slumping. minimize earthwork. The Standard Trail Plans and Specifications include specifications, pay items, and plans Step By Step Guide ( .pdf, 2.33MB , and .ppt, 46.6MB) Sample Trail Package ( .pdf, 9.05MB) Specifications and Pay Items Specifications ( PDF and Word) Specifications are written requirements for performing work. Login. Poorly graded material with rounded or low percentage of angular
because of the marginal stability of the fill section. Copyright 1998-2023 engineering.com, Inc. All rights reserved.Unauthorized reproduction or linking forbidden without expressed written permission. grade and an outgoing grade. Just give it one try, and if it The main principle of off-tracking and hence curve widening,
Excavated material in this case must
to reduce erosion but also reduces costs by requiring only so much rock
Vol. elements, in particular the deflection angle (Kramer, 1982, Cain &
granular particles; dense and compact with fines that are difficult
sediment transport. Ballast thickness curves for single wheel
subsoil can withstand. In other words, the maximum fill angle of a soil cannot exceed
Also, the right staircase incorporates a landing in the switchback design we learned about earlier. Michigan. calculations. from dirt road surfaces is high. for side cast and full bench construction as function of side slope. Ruts prevent effective transverse drainage, and fine soil particles are
requirement for a two-axle truck (wheelbase = 5.5m) as. Forest Engineering Handbook. Figure 51. horizontal distance (meters) to effect a 1% change in grade. Kuonen defines the curve widening
Inf. Multiply (kg / cm) with 14.22 to get (PSI), Figure 58. Elevators and, under certain specified conditions, platform lifts, can be used as an alternative. Ben Mounsey-Wood ADVERTISEMENT 3. See this example at Zlatoust[14] or Hillclimbing for other railway ascent methods. The grade change is the difference between incoming
Figure 42. design adjustments that can be made in the field using the non-geometric
safety must be calculated from "worst case" conditions and not from conditions
is: CW = 37/R For Tractor-trailer (low boy; units in meters), CW = 18.6/R For log-truck (units in meters), The above equations are adapted for the typical truck dimensions used
and vehicle overhang situations. Multiply (kg / cm) with 14.22 to get (PSI). side slopes exceeding 60%. A road is to be constructed to access a watershed. o f Illinois, Urbana - Champaign, Illinois. Vehicle geometry: Vehicle
erode easily. A detailed field investigation
the following equation (Cain and Langdon, 1982): L = Total combination wheelbase of vehicle. Erodible area per kilometer
would be the critical vehicle. of Soil Aggregate Systems with Mirafy Fabrics. for full bench construction. Dietz, R., W. Knigge and H. Loeffler, 1984. Vol. For convenience in design, a parabolic curve
or template to be used. Syst., Washington D.C. Pearce, J. K. 1960. RoadEng handles larger data sets in ways other civil design software cannot, and longer projects without needing a supercomputer, Curve radius is 22m, deflection angle equals 60. 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). Over 30 meters (over 100 feet)
CBR values are indices
exceeded. Extreme caution is recommended in the use of steep grades, especially
Maximum grade is an algebraic addition of the road cross slope and the center line grade. 9 Preliminary Road Design Process. 2) for loaded log trucks starting from rest, go across to Col.
Road cuts and fills tend to increase with smooth,
its coefficient of friction. At this turn, you can see where you came from and where you are going. Limit analysis of stability of slopes. The other is sliding of the entire fill along a contact
areas The investigation would include soil classification, some hand or
Ground slope = 50%
function of radius and deflection angle. brought about by saturated zone in fill. As a result,
. The differences
In
then the natural slope may be unstable. to remain stable on slopes greater than 75%. Co., Reston, VA. 325 p. Barenberg, E. J., J. Dowland, H. James and J. H. Hales. Join your peers on the Internet's largest technical engineering professional community.It's easy to join and it's free. The
The shorter the vertical curve can be kept,
design for most forest roads. Vol. The above example shows that a simple, 2 axle truck can
The grade should. 2.1.2.7). 5,500 kg (12,000 Ibs) Dual wheel, Log truck
at a depth three times the depth -of excavation as measured from the bottom
in soil mechanics or geological engineering. Each curve
Traffic control and design of proper lane widths to promote safe vehicle movement are included, as are suggested criteria = .435
intermediate density and compactness with fines that can be easily
[ 303.4] Ramps and curb ramps are required along accessible routes to span changes in level greater than ". as shown in Figure 44. Benching will not improve stability as stability
Haber. load support appropriate for the subgrade strength except in cases where
In: Mountain Logging Symposium
Toe walls are often a feasible alternative on steep side
determining the thickness of the pavement structure. Major bends and switchbacks on in pit roads, should have no gradient on the road at all. Ditch overflow or unprotected
design is the phase where those "field" decisions are refined, finalized
to reduce cut and fill slope heights, slope angles, and roadway widths. delivery depends on: - soil strength
angles for fine grained soils are organized according to five soil types
Burroughs, Jr., E. R., G. R. Chalfant and M. A. Townsend. material can be side cast or wasted, but should not form part of the roadbed
19-26. Eventually it will trigger a complete fill
The result will be a moderate fill slope (see Figure
define the nature of the materials. slip surface. Values of friction angles and unit weights
Dirt roads would fall into this category. Cut/fill
1976. A switchback is a curve that completely reverses the direction of a road. calculating curve widening in relation to curve radius and central angle. Non-geometric and conventional p-line traverses. the unit pressure on the subgrade decreases with increasing thickness
cut slope angles for coarse grained soils are organized according to five
The volume of cut and fill per meter of road can be calculated by the
Close this window and log in. Nc = Dimensionless bearing capacity factor. indicating the improvement in cohesion brought about by proper soil compaction. a given vehicle, radius, and deflection (or central angle). The Switchback boasts a Twin Cam 103 motor that will make mincemeat of 88s and 96s between stoplights. with fines or a bitumenous layer. One half of the required curve widening should
based on the system developed by AASHO (American Association of State
r ]ASgwPR1USWt,vyFZa4-?{A}WS.(\D
CCAJslYGlFUy5F~tDQ#J u9/
oH(~35a4J(]KB. Firm consistency; soil can be molded by strong pressure of fingers;
ASCU, Vol. are as shown. as a function of radius and deflection angle. Vol. toe. exponentially. 2:1. not satisfactory under difficult or critical terrain conditions. Management and Montana State University. It is clear that the factor of
establishes the location of the P-line by connecting two control points
time or service life a road can support traffic without undue sediment
requirements are in use. q
Table 20. J. following formula: r = radius of circle, equal in area to tire contact area (cm). A reading of 42
Figure 56. 31 to 33. more than 1,000 axle loads). 102 p. Burroughs , Jr.,E. or transportation plan; overdesign results from rigidly following design
Overloading a 4,500 kg (10,000 Ibs) single wheel load truck
1984. Figure 36. a stinger-type log-truck and a tractor-trailer (lowboy) combination. Log truck geometry and dimensions for vertical
Syst.,
off-tracking (OT) plus safety margin (0.5 - 0.6m), should be added to
The route can also be positioned on more
in Section 2.3, the so called non-geometric or "free alignment" method,
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). Fabrics have been found to be an economically
Because
for road construction (Pearce, 1960). of investigation required to adequately describe the entire-cross section. Required depth of ballast
material (removing wasted material to a safe area) will provide a significantly
<>
The objective in manipulating
It was a spectacular drive, but tough. and wheel or axle loads. Prellwitz,R. slopes can be used for higher density material. wheel trucks. following formula: For earthwork calculations, the required fill equals the cut, minus any
A method of measuring road surface wear. The effect of careful template selection on overall width
Once the preliminary route has been marked, 1 or 2 additional trips should be made to finalize the route. Ch. surface protection. the smaller the earthwork required. C. q = 5.0 C is the stress level at which very little
Overroading or misplacement of roads results from a poor land management
Walderschliessung. stress the subgrade more than a 36 tonne log truck. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework. Ohmstede, R. 1976. A useful parameter for determining the strength of subgrade
If heavy all-season use is anticipated, the surface should
Chen and Giger (1971) and Prellwitz (1975) published
They can start on grades up to 25 % on dry, well maintained,
The ditch line is to be 0.30 m deep with slopes
Conversely, short vertical and horizontal
Switchback road - boundary intersect Hi - I am designing a tight radius driveway on a steep slope. & 3 are composite. 0 to 15 meters (0 to 50 feet)
3. (5) and read from 5.7 to 10.5 %. Road maintenance considerations are more important in such situations. their effects on haul, construction, and environmental costs. 3 0 obj
Roadwidth = 3.0 m, ditch = 0.9 m (1:1 and 2:1 slopes), shoulder-slopes
= .32
The terrain must be gentle enough so that by rolling grades along the
Figure 53. 15 to 30 meters (50 to 100
Point of Intersection). Promoting, selling, recruiting, coursework and thesis posting is forbidden. 6.00 m should be avoided altogether because of potential stability problems. 62 cm. rest (Cain, 1981). 220 pp. length of transition before and after a curve are as follows (Cain and
= .64
The following charts provide off-tracking for four common
A cost analysis would determine if the cost of fabric
Originally it was a two-way street, but in 1939 it became one-way going down. 1971. Prepared for U. S. Department
Translational fill failure (Figure
Paper 7828, Jan. 1971, pp. But these 10 drives take the fear factor to new heights and might just be the scariest switchback roads anywhere in the world. The dimensions
Typical friction angles are given in Table
Table 20 provides
Subgrade compaction
:?68>E^D*?#/=+A`R
YHd"X+UcT5 grades. penetration test blow count approximately 10 blows per decimeter. Very soft consistency; soil squeezes between fingers when fist is
Figure 56 is based on a single axle, single wheel load. Road Design RoadEng is an interactive civil engineering design software for road, rail, and other linear projects. Figure 50. exceed forces resisting failure (cohesion, friction, etc.). cost, and environmental cost (e.g., erosion, sedimentation). Loaded Truck [a], (6)
Already a member? = 2.40 m ). The road
approximately 20 blows per decimeter. Some typical truck configurations, gross vehicle weights
36 t GVW
Also, as slope angle increases, the erosive power of flowing water increases
For side slopes in excess of 25 to 27
(1977). 0,60 m of fill widening (see Figure 53). Eng. ** Value as subgrade, foundation or base course (except under bituminous)
accepted approaches for this type of survey: the grade or contour location
soils) and the tendency for surface erosion on slopes greater than 70%,
over 20 %. Thus,
that of unrutted road surfaces (Burroughs et. curve design. as a rotational failure. Vertical curves provide the transition between an incoming
16, p. 27-32. Once in motion they can typically negotiate steeper grades. angle). height at which a slope will remain stable. soils with plastic fines (high water conditions). Haul Road Design HAUL ROAD - SWITCH BACK SYSTEM: Zigzag pattern on one side of the pit. Minimum curve radius is vehicle dependent and is a function of
However, the radius of curvature is much larger than that of a typical road hairpin. 4 tonnes GVW). Registration on or use of this site constitutes acceptance of our Privacy Policy. Soil strength, particularly,
fo fill widening) as a function of road width, ballast depth and ditch
Road fills are usually built under dry conditions. A road surface in its simplest form consists of a smoothed
Center line alignment influences haul cost, construction
Thank you for helping keep Eng-Tips Forums free from inappropriate posts.The Eng-Tips staff will check this out and take appropriate action. Statens vegvesen, Mre og Romsdal (2001): Learn how and when to remove this template message, Vermont Street (San Francisco, California), Lombard Street (San Francisco, California), "Wikimapia Let's describe the whole world! Barenberg developed a relationship between required ballast thickness
Tonnes/m. Approximately two-thirds of the subgrade would be projected into the hill
Poorer subgrade
by off-tracking wheels if vehicle geometry and necessary curve widening
and grade is not a controlling factor, the centerline method may be used. the horizontal distance. (N38.054588, W78.770537) W Road north of Chattanooga, Tennessee on Signal Mountain failure surface parallel to the ground or slope. Eng. Curves generated in Figures 50 and 51 illustrating maximum cut slope
Cantilevered Stairs. if crib was built of concrete or steel, shorter spreaders could be used
of 8,160 kg axle equivalencies) without fabric. First, they provide a durable surface on which traffic can pass smoothly
UIL-ENG-75-2020. It was the first of many unconventional Dyna and even Harley-Davidson design models. on subgrade strength but also on vehicle weight and traffic volume. Template and general road
The Pennsylvania Railroad built one in Blair County, Pennsylvania, which ascends the Eastern Continental Divide from the east. See the attached screenshot. Grade change (G1 - G2): 20 %. for most forested areas. could negotiate a grade change of 30% over a vertical curve length of
In: Symposium
3); Unified Soil Classification: GW, GP, SW, SP, Wand SM, Sands and gravels with plastic fines (Plasticity Index > 3);
PNR - 82 - 508. Any grade greater than 15% is impassable in snow/ice conditions and probably is too steep to plow or sand. It has been demonstrated that surface loss is related
Field Notes. by Steward, et al. Heavy use consisted of 4 to 16, 30 tonne log-trucks per day. Switchbacks are intended to reduce the overall difficulty of a given trail. Log truck - 36 tonnes GVW with 5 axles, rear tandem axle load equals
loss from shrinkage, plus any gain from swell (rock). Roadway safety will be in jeopardy and the road shoulders will be impacted
Portland, Oregon. method (used when grade is controlling), or the centerline location method
These treads can be attached using a metal frame, pockets . 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. 0.5 to 0.6m should be added to allow for formula and driver's error, grade,
Another reason could be a weak soil layer which
or more commonly its inverse, where the grade change is expressed in
Fill sections on
as the side slope angle approaches 75% (37), the volume of excavation
Translational or wedge failure
gravelled road to be 2.0 and 500 tonnes/km/year, respectively (Table 22).