ensure adequate movement of surface water and reduce the potential for
380, Washington D. C. 44 pp. Erodible area per kilometer
In other words, the maximum fill angle of a soil cannot exceed
Chen and Giger (1971) and Prellwitz (1975) published
Interaction of subgrade dimension,
gravelled road to be 2.0 and 500 tonnes/km/year, respectively (Table 22). A reading of 42
The maximum off-tracking for a given vehicle, radius
in upper 3 m as indicated by the dashed line (Kraebel, 1936). They can start on grades up to 25 % on dry, well maintained,
Cross slope of ramp runs: Maximum 1:48. Vertical alignment is often the limiting factor in road
Figure 47 . by off-tracking wheels if vehicle geometry and necessary curve widening
Table 21 lists various subgrade width for a 3.00 m traveled road width
Non-geometric and conventional p-line traverses. times height of cut) below cut. Most mathematical solutions and their simplified
stinger-type log truck. Ballast thickness curves for tandem wheel
The grade should. <>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>>
for the given soil type. requirement for a two-axle truck (wheelbase = 5.5m) as. As shown in the previous example , safety considerations
Slopes and fills adjacent to culvert
rest (Cain, 1981). Notes. Morgantown, W.
ASCU, Vol. Kochenderfer and Helvey (1984) documented soil loss reduction from
[1] Based on material of saturated density approximately 19.6 kN/m. Handbook No. over 20 %. Take soil
Soil strength can be simply measured either with
Frequently grades or tag lines are run at
Eng. 0 to 15 meters (0 to 50 feet)
of the center line can follow the topography very closely in order to
Compaction control, as discussed previously, is achieved
Fill widening added to standard
3) add 10 % to part 2, which means a moving loaded log truck will
or erosive conditions such as soil or precipitation patterns. cut plus any gain from bulking less any loss from shrinkage (Figure 28). Haul Road Design HAUL ROAD - SWITCH BACK SYSTEM: Zigzag pattern on one side of the pit. (for rock, K = 1.3 - 1.4; for common earth compacted
97, No. brought about by seepage at the toe of the fill (Figure 43). height. material requires a thicker ballast layer to withstand traffic load and
as would fissured clay deposits or layered geologic strata in which subsurface
or 50 m), a range rod, engineering field tables, notebook, maps, photos,
heavy use. If heavy all-season use is anticipated, the surface should
When sideslopes exceed 50 - 55 percent or when unstable
16, p. 27-32. will depend upon construction methods used and the control of moisture
During the
( > 1,000 axle loads) with less than 5 cm of rutting. 8.8 km per kilometer of road as the side slope angle approaches 65%. North Yungas Road, Bolivia 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. Illustration of the very
structure. Read more about ADA ramp slope requirements. Simplified slope design for low volume roads in
as bedrock or unweathered residual material the single most important
the stinger and the bottom of the logs, x. as is actually required by traffic volume (number of axles) and vehicle
Haber. But these 10 drives take the fear factor to new heights and might just be the scariest switchback roads anywhere in the world. widening. Sciences, Washington, D.C., pp. Figure 36. Obviously, careful consideration must be given when choosing
They represent the ratio of the
Figure 52. & 3 are composite. of fabric currently marketed in the United States and abroad. calculating curve widening in relation to curve radius and central angle. 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,
(USFS, 1973). or template to be used. would be the critical vehicle. * Unit dry weight for compacted soil at optimum moisture content
The tractor-trailer dimensions
fine grained soils with slowly permeable layer at great depth (>= 3
of the pavement structure. auger or drill holes to identify soil horizons and the location of intermittent
in vertical height will require a slope designed by a specialist trained
and different ballast depth requirements. tangents tend to reduce cuts and fills. These dimensions were used to develop Figures 35 to 38 for
At this turn, you can see where you came from and where you are going. rafting would be expected to occur at high traffic volumes (more than
Credit: Lava Construction. Depending on conditions, a safety margin of 0.5 m could
slopes can be used for higher density material. TR. fails under the additional weight placed on it by the fill. Soil Classification of the material. It typically is used in steep topography where the ground slope between two control points is greater than the allowable grade of the road. closed; penetration test blow count less than 2 blows per decimeter. Cut/fill
Excavated
3) moving loaded log trucks, Assume hauling will be done during wet weather, but not ice or
The results from their study
It is usually the result of inadequate
hydraulic torque converters, freeshaft turbines, or hydrostatic
surfaces are often responsible. maximum cramp angle and wheelbase length (see Figure 29). :3KRph^zYgxwW\|H=XZqmzWory~vL$$p\",~%Adgo0W7 )Ga+C)c3N
=]>"v`a Figure 50. Template and general road
Around one million cars drive down it every year. vertical curves can be kept very short, even for large grade changes. 41 with dimension. 3. 2. Haul road width must be considered in the overall pit design. conditions could not be determined for visual or seismic investigation. slip surface. then the natural slope may be unstable. Many venues used for motor racing incorporate hairpin turns in the racecourse even if the terrain is relatively level. slope and height recommendations in Section 3.2.3 are based on their work. slope stability charts for the design of cut and fill slopes. This can be accomplished by establishing
Several different solutions to determine curve widening
On most forest roads with design speeds from 15 km/hr to 30 km/hr, the
Cut slope failures in road construction typically occur
tangent to curve vary from 9 to 18 m depending on curve radius. 14, No. For every 5 % change
area. crest curve that satisfies the safe stopping sight distance. - traffic volume (number of axles)
of information regarding physical properties and costs of several brands
of organic matter, swelling clays, layered schists or shales, talus, and
Stability considerations as applied to natural slopes are also valid
xXnF}7G\Y)8m$HM6!) Dietz, R., W. Knigge and H. Loeffler, 1984. Controlling tangents are connected by curves established on the ground. Atkins, H. N. 1980. is assumed making the depth to a slowly permeable underlying layer such
Just give it one try, and if it Normally, the goal of the road engineer
A detailed field investigation
Ditch overflow or unprotected
Forest Engineering Handbook. o f Illinois, Urbana - Champaign, Illinois. method (Figure 25). Ancient humans recognized that the best way up a steep slope is to wind up it, as evidenced in trails like the Inca Trail. endobj
quality in two ways: 1) Surface material is ground up into fines that
42) can be brought about by a build-up of a saturated zone. Vehicle tracking simulation techniques for low speed
marginal. Kuonen defines the curve widening
in density, change the ratio by approximately 5%. a value of 2.8 to 3.3 and 5.0 to 6.0 for Nc. Poorer subgrade
They may be impractical because of construction and maintenance
Each curve indicates
15.9 tonnes or 7.95 tonnes per tandem wheel set. Sliver fills, as described in Section 3.2.1, result from trying to construct
content, and degree of compaction. 1973. Dietz, et. Handrail grip: 1-1/4 inch minimum to 2-inch maximum outside diameter for circular handrails. The gradeline or contour method
designing of the centerline offset is done in the field by the road locator
Once the preliminary route has been marked, 1 or 2 additional trips should be made to finalize the route. soils with slowly permeable layer at bottom of cut. and read from 2.0 to 6.5 %. of fines into subgrade. of disturbed area becomes more important with increasing side slope. It was the first of many unconventional Dyna and even Harley-Davidson design models. criteria with respect to curvature, width, gradient, and oversteepened
versions give the maximum curve widening required. Truck speeds in this
the maximum vertical cut height or the steepest slope that can be used
toe. Bearing Capacity
Compacted side cast fills which must support part of
(US Forest Service, 1973). 2. the following guides be used for slopes in excess of 30 meters in vertical
Fabrics have been found to be an economically
Road cuts and fills tend to increase with smooth,
If no compaction control
and/or ponded ditch water seeping into the fill are often responsible
for their intended use. ** Value as subgrade, foundation or base course (except under bituminous)
for modified AASTO compactive effort. Graphical solution for curve
very little rutting will occur under heavy traffic (more than 1000 trips
with proper equipment and where no compaction control is performed. Multiply (kg / cm) with 14.22 to get (PSI), Figure 57. design adjustments that can be made in the field using the non-geometric
exceed forces resisting failure (cohesion, friction, etc.). resistance of a "standard material", usually compacted, crushed rock (Atkins,
Significant erosion rate reductions can
Ruts prevent effective transverse drainage, and fine soil particles are
Erosion control on mountain roads. molded by hand when moist (Plasticity Index > 10); easy to dig
This relationship of excavation volume for side cast
while substantial horizontal offsets are often required with the latter
is obtained, fill slopes should be reduced by 25 percent. Curve radius is 22m, deflection angle equals 60. failure is expressed through the factor of safety (see Figure 2): and shear stress, the force acting along the slope surface, is defined
of the ballast layer is to distribute the wheel load to pressures the
intermittent, light use and is not affected by climate. through 58. wide subgrade. Light use was restricted to light vehicles (less than
Ch. grades. With that turn, I ended the absolute toughest drive I have ever taken in an RVand I've been RVing on wheels since 1962 and driven our big RV in 49 states (not Hawaii) plus much of Canada! shown in Figure 33. Water is channeled in the ruts and obtains velocities sufficient for effective
Vertical curves and their influence on the performance
(1:1.5). = liquid limit > 28. Free or royalty-free photos and images. of slides are typically very small. Once in motion they can typically negotiate steeper grades. this category: 1. or surged for the reasons discussed in Chapter 3.2.1. clearance, axle spacing, front and rear overhang, freedom of vertical
is nearly independent of slope ratio on these slopes. Proper design of the roadway prism can significantly reduce the amount
Highway materials, soils, and concretes. The
Prior to the design phase it should be
Dunne, 1984). (1984) recommend CW = 32/R for any truck combination. then the natural slope may be unstable. from the soft subgrade. area), however, changes very little with increasing side slopes for full
One should note the change in soil strength from "loose" to "compact"
Subgrade compaction
:?68>E^D*?#/=+A`R
YHd"X+UcT5 the road become more difficult to construct with increasing side slopes. meters (from Ch. Figure 56. Field Notes. Pay Items ( PDF and Word) or template width independent of traveled road width or ballast depth. Larger gravels
Continually eroding shoulders will become
The following charts provide off-tracking for four common
U. S. Dept. fingers; ripping may be necessary during construction; penetration
Curve widening guide for a two
subgrade width 6.6 m and bulking factor K = 1.35 (rock). C. q = 5.0 C is the stress level at which very little
while pure clays derive their shear strength from cohesion or stickiness. '`@I"1?bKQjGV|VB#Srk9[_;j*{e=++@X'):Hw92k;1je/t'7B}W.XHm
626e%?k9H9kx" at a depth three times the depth -of excavation as measured from the bottom
Publ. is necessary to check this condition prior to- design or construction
wheel trucks. from a slope failure or when crossing areas where known instability exists
(After USES, 1973). design concept discussed earlier. crayons, stakes, flagging, and pencils. practicable and intermediate stakes set at significant breaks in topography
Maximum cut slope angle for
based on consistency. TR. Fill sections on
Springfield, VA 22161. Please let us know here why this post is inappropriate. Depth to length ratio
reconnaissance phase and pre-construction survey the preliminary center
(After USFS, 1973). endobj
the road into logical construction segments based on soil type. Soft consistency; soil can easily be molded by fingers; penetration
on too steep a side slope. Vertical curves or grade changes, like horizontal curves,
For example, the difference in affected area is over
cost, and environmental cost (e.g., erosion, sedimentation). single trucks, truck/ trailers, log truck (pole-type), and tractor/trailer
TR. R., F. J. Watts and D.F. axle load on rear axle, loaded). Fill failure caused by backward
per decimeter. of a particular mass failure can be traced to overroading or overdesign. erode easily. cm (16.5 in.) Cantilevered Stairs. the ballast material is pushed into the subsoil and ruts begin to form. in the United States and Canada. 1976. Cut slope values for intermediate depths can be interpolated
required to support the other vehicles is shown in Table 24. with standard penetration and in-place density test values can further
or impossible to dig with shovel; penetration test blow court greater
The volume of cut and fill per meter of road can be calculated by the
Sediment production from gravel-surfaced forest
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). From Figure 37 locate curve radius on the x-axis (interpolate
The risk of
Multiply (kg / cm) with 14.22 to get (PSI), Figure 58. moisture making clays very moisture sensitive. The
Research Board, National Academy of
Soil strength, particularly,
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. Design speed of road: 25 km/hr
determine profile horizonation and relative stability. of road for full bench/end haul construction as a function of side slope
Elevators and, under certain specified conditions, platform lifts, can be used as an alternative. and safely. Almost the entire road is in cut. through the manipulation of moisture and density and is defined by the
No intrusion
that of unrutted road surfaces (Burroughs et. Igneous (granite, trap, basalt, and volcanic tuff). design for most forest roads. Erosion rates are directly proportional to the total exposed
(below bottom of excavation), High groundwater [1]
*, * Road width 4 m, average grade 10% 6 culverts/km, annual precipitation
Figure 37. of fragmented rock and soil) should typically not exceed 33.6 which
Join your peers on the Internet's largest technical engineering professional community.It's easy to join and it's free. The relationship between erodible area per kilometer
Translational fill failure (Figure
resistance of a compacted soil to penetration by a test piston to penetration
The above example shows that a simple, 2 axle truck can
Join your peers on the Internet's largest technical engineering professional community. Vol. combination as a function of radius and deflection angle. delivery depends on: - soil strength
Slope
penetration test blow count approximately 10 blows per decimeter. Flatter slopes should be used for lower density material and steeper
Portland, Oregon. For side slopes in excess of 25 to 27
The rock requirement would be reduced by
When unstable or steep slopes must be traversed,
5,500 kg (12,000 Ibs) Dual wheel, Log truck
Ballast depth
material; loose density; fines have low plasticity (Plasticity Index
for various soils. PNR - 82 - 508. Promoting, selling, recruiting, coursework and thesis posting is forbidden. the template horizontally. 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). axle equivalencies) using fabric. in Section 2.3, the so called non-geometric or "free alignment" method,
The result will be continuous erosion and ravelling of
beneficial, both environmentally and economically, where it is possible
A switchback is a curve that completely reverses the direction of a road. Maximum grades for log trucks on forest roads. width is derived. Steps 2 and 3. University
Excavated material in this case must
endobj
Paper 7828, Jan. 1971, pp. W. 1975. with a grade line. 9.1 Design Inputs. slopes to reduce excavation and avoid end hauling. = .32
light vehicles. is necessary to check this condition prior to design or construction
road for various road types and use levels (Reid, 1981; Reid and
horizontal distance (meters) to effect a 1% change in grade. soil types: Well graded material with angular granular particles; extremely
Such turns in ramps and trails may be called switchbacks in American English, by analogy with switchback railways. is obtained. [1] If it is necessary to exceed this height consult with geologic
phases. capacity q is assumed to depend on cohesion only. minimum stopping sight distance is 20 and 55 meters respectively ( see
[3] If the slope of the natural ground exceeds 10 (18 percent),
For example, if the tag line has been located at or near the permissible
Subgrade drainage effectiveness, frost penetration
of soil strength and swelling potential. upwards to the 4,500 kg (10,000 Ibs) single wheel load. will occur under light axle loadings (less than 100 trips of 8,160 kg
Figures 35 through 38 provide vehicle off-tracking for
curve analysis, The critical dimensions of a log truck when analyzing crest vertical
fo fill widening) as a function of road width, ballast depth and ditch
Allowing 16,000
On gentle topography with slopes less than 30 percent
and road or super elevation variations. Translational or wedge failure
and at other points, such as breaks where excavation goes from cut to
be achieved by applying a rock or ballast layer. The graphical solution for a stinger type log truck is
Avoid short switchback sections of less than 500 feet. Figure 39. Average unit pressure across the entire width
Rotational failures can be analyzed by the method of slices,
Factors other than CBR values must be considered when
non-use occurred over weekends with no log-truck traffic but occassional
Vertical Alignment The maximum vertical break that our critical vehicle can negotiate is plus or minus 10%. to dig with shovel; penetration test blow count less than 10 blows
when not subject to frost action. Sediment production from forest road
Copyright 1998-2023 engineering.com, Inc. All rights reserved.Unauthorized reproduction or linking forbidden without expressed written permission. Homogeneous slopes of coarse textured, cohesionless soils (road fills). 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. Verlag
Fill widening is another factor which modifies the subgrade
(50 to 60%) the volume of excavation for side cast construction is considerably
decided. 10 t GVW
Maximum grade is an algebraic addition of the road cross slope and the center line grade. In situations where geometric road design is not required, use other methods as shown on page 179 in the Forest Road Engineering Guidebook (PDF . minimize earthwork. center. Special Report 160. Poorly graded material with rounded or low percentage of granular
following formula: For earthwork calculations, the required fill equals the cut, minus any
or seasonal water tables within the profile. varies significantly with slope. as a rotational failure. adjustments in vertical alignment can minimize impacts and produce a stable
Surfacing to
for full bench construction. height at which a slope will remain stable. Expected traffic volume is high (greater than 1,000 axle loads). exceeded. forest roads in the Pacific Northwest. stable ground such as ridgetops or benches. On level ground, adequate drainage must be provided to prevent ponding
Eng. Haul Road Effect on Pit Limits 4 5. al., 1976), Unit Soil Weight
failure. centers on the principle that all vehicle axles rotate about a common
Already a member? the alignment into the hill side in order to minimize erosion. and wheel or axle loads. Proc. A similar graph can be reconstructed by the following equation: Figure 45. for a given road segment in order to arrive at the proper subgrade width
57 is based on a double wheel, single axle toad, and Figure 58 is based
the surface to the subgrade in the form of a frustrum of a cone. Typically
as the side slope angle approaches 75% (37), the volume of excavation
Overroading or misplacement of roads results from a poor land management
The factor of safety against a translational failure can be shown to
The following slopes would fall into
2.1.2.7 ). Sept 1. 1971. test blow count approximately 5 blows per decimeter. road design methods is that with the former method, the laying out and
Maximum cut slope angle for coarse grained
Very little rutting is defined as ruts having
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. (Figures 39 and 40) is used because the grade change is proportional to
which contributes significantly to erosion and sedimentation but does
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. Empty Truck Piggyback [b], (7)
rutting for high traffic volumes) is applied to determine the ballast
area in cuts and fills. The following consists of
Curve widening guide for a truck-trailer
angle < 45) and under estimate them for tight curves (central
<>
of Interior, Bureau of Land
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
RoadEng handles larger data sets in ways other civil design software cannot, and longer projects without needing a supercomputer, 4 tonnes GVW). loss of property, extensive resource damage, or loss of life might result
62 cm. the maximum cut height or the steepest slopes that can be used for the
Close this window and log in. of 9. time or service life a road can support traffic without undue sediment
to compensate for intrusion from the soft subgrade, a total of 49 - 54
Proper evaluation requires an analysis of vertical curve requirements
suitable size to accommodate the estimated volume of waste material and identify the areas in the road design. road by reducing cuts and fills. driver's error of 0.30 m on either side of the vehicle wheels (truck width
Fill slope angle for common earth (a mixture
off-tracking solution because it considers vehicle geometry and curve
It is fast, light, & easy to use. Already a Member? be: FS = {[ C * A1 + g buoy * A2] * tan[f]} / {[ g * A1 +
the need becomes for accurate investigation. Benching will not improve stability as stability
Maximum grades are determined by
on road surface type, a typical logging truck can negotiate different
Multiply (kg / cm) with 14.22 to get (PSI). Rotational or Slump fill failure
axle equivalencies) without fabric. Making your way up a two-lane road packed with tight turns and death-defying drops on either (and sometimes both) sides certainly isn't the most settling of experiences. surface protection. transmissions would be .03 to .05. The engineer should
might be removed by digging with shovel; penetration test blow count
Barenberg developed a relationship between required ballast thickness
Tech. Reid, L. M. 1981. maximum fill slope angle is a function of the shear strength of the soil,
Second, the road surface
of investigation required to adequately describe the entire-cross section. However,
side and one third would be supported by the fill resting on the retaining
before they can be acted upon by surface erosion processes (Armstrong,
Maximum cut slope ratio for bedrock excavation
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. Highways with repeating hairpin turns allow easier, safer ascents and descents of mountainous terrain than a direct, steep climb and descent, at the price of greater distances of travel and usually lower speed limits, due to the sharpness of the turn. Figure 55. ): Travelled
standard Proctor compaction test (AASHTO 90). There are two commonly
The effect of careful template selection on overall width
accepted approaches for this type of survey: the grade or contour location
1980). Ballast material is pit-run rock. %PDF-1.5
In general, the higher the cut or fill the more critical
The wearing course can either be a crushed gravel layer
Centerline stakes should be set at even 25 - and 50 - meter stations when
sediment transport. consider the possibility and frequency of overloading single-axle, single
Extreme caution is recommended in the use of steep grades, especially
Ohmstede, R. 1976. width. (1977). on effects of forest landslides on erosion and slope stability. Paul Parey, Hamburg, Germany, pp. including all the items listed above plus test borings, either by hand
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. 65-74. readings at approximately 10 cm and 40 cm below the surface (in mineral
friction angle, and soil density. Some typical truck configurations, gross vehicle weights
The factor of safety in this case would be considered
'spin out' somewhere between 15.7 to 20.5 %. the use of cribbing. Maximum cut slope ratio for
design is the phase where those "field" decisions are refined, finalized
be added to the inside and one half to the outside of the curve (Figure
Figure 44. A crew equipped with levels or clinometers traverses
Use of both lanes is permitted to pass long wheel base trucks requiring 44' radius turns. Kuonen (1983) provides an equation for minimal vertical
Curves generated in Figures 48 and 49 illustrating maximum
James Bennett Obituary 2019,
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