CHAPTER #4 RIGHT-OF-WAY & ROADWAY
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4.1 Introduction
1.
2.
The railway right of way is the area from fence to fence without the track and
structures.
The roadway is considered to be any construction within the right-of-way
except the track, bridge structures, signals and crossings.
The PNR (Philippine National Railway)
right-of-way
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3.
4.
5.
6.
7.
Soil is the main building material for the railway.
Identification and classification of soil
It is essential to identify the various soils and avoiding using those may give
problems, since it is seldom that soil can be processed to improve its
properties.
Environment which is defined as the sum of all the external influences that
act upon the soil can also affect the behavior of a soil.
The identification of materials, analysis of their environment and a
prediction of their behavior is the field of geo-technology.
Problems that geo-technologists dealing with: slope stability, seepage,
track bearing capacity, drainage and settlement issues.
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4.2 Right-of-way
Definition: The railway right-of –way is the land upon which the track and
its supporting features are built.
Strips of land were generally obtained by land grants, purchase outright,
permanent easement, franchise, etc.
The railway right-of-way includes the subgrade
upon which the ballast section and track are
built, along with adjacent improvements and
features to support and maintain the railway
track.
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The right-of-way typically includes ditches
running along the track and related drainage
structures, any embankments and cuts, any
retaining walls or other earth-supporting
structures, fence, signs, utilities, and outlying
structures.
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1.
Right-of-way Width
a.
b.
c.
d.
e.
There’s not a set width to railway right-of-way. Most common width are 100,
200, and 400 feet.
On single track, the right-of-way is measured perpendicular to the centerline of
the track.
On a multiple track railway, the centerline of the right way may be to the center
of two tracks or the center of one of the tracks.
On new lines, the right-of-way must be wide enough for the track, the
embankment blow it, access roads, other structures necessary to operate the
railway and future expansion.
In areas of heavy snowfall, additional right-of-way may be required for snow
plowed from the tracks or the placement of snow fences.
2.
Fences
a.
b.
c.
The edge of the railway’s property is sometimes marked
with monuments, but more often with a fence.
The right-of-way fences for livestock are generally
barbwire fences.
Chain link security fence are used in urban areas.
Chain link security fence
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barbwire fences
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d.
e.
On passenger railways, fencing is often installed through multiple track station
platforms, to prevent passengers from crossing tracks at other than
designated crosswalks.
Fences are installed considering weather conditions.
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3.
Reduce snow accumulation
Prevailing wind
Block blowing sand
Utilities
Railway require permission for
utilities to cross or use their property.
a.
Underground utilities
b.
Fiber optic cable
a.
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4.
Vegetation
Safety issues created by vegetations
a.
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Chocks tracks, ditches, and other facilities create sizeable drainage and track
maintenance problem.
Hazards, which covered by weeds, cannot be readily seen and may become a tripping
hazard.
Creating observing difficulties and may contribute to an accident.
Vegetation control
b.
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Ongoing process
High priority annual budget
Objectives: vegetation must be controlled so that it does not:
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Grow within the ballast section or obstruct ballast drainage.
Interfere with adequate visibility at grade crossings.
Obstruct visibility of location markers, switch position indicators, signs or signals.
Obstruct drainage.
Interfere with the safe operation of trains.
Prevent proper track inspections.
Present a fire hazard to timber structures.
Interfere with railway personnel performing normal track duties.
Brush the side of rolling stock.
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Undesirable vegetation removal means:
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Herbicidal means
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No universal herbicide which will control all species of vegetation.
The vegetation must be identified and specifically dealt with.
Combinations of different chemicals have been found to be the most effective.
Manual means
Licensing
Vegetation planting:
Vegetation may be planted and grown on the slopes of cuts and fills and in other locations within the
right-of-way to prevent erosion.
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4.3 Roadway
1.
Soils
a.
Definition( depends on the discipline or profession being studied)
Geologist
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Agriculturist
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Engineering:
The word soil refers to that portion of the earth’s crush, which is fragmentary,
such that some individual particles may be readily separated by agitation
( in water) of a dried sample.
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b.
Soil Types
The size of particles varies, being large for gravel and microscopic for clay. This
proportion of voids (porosity) is inversely portional to particle size, being
large( nearly 50%) for clay and smaller for gravel.
c.
Major Soil Divisions
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The Unified Soil Classification System defines three principle soil types:
coarse-grained soils (sands and gravels), fine-grained soils (silts and clays)
and organic soils.
The Unified Soil Classification (USC) is based on:
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Texture and composition ( coarse grained vs. fine grained).
Organic vs. inorganic.
Cohesive (plastic) vs. Cohesionless (non-plastic).
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Coarse-grained soils
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Boulders-Particles larger than 12 in. (300mm) in diameter.
Cobbles-Particles between 3 in. and 12 in. (75 and 300mm) in diameter.
Gravel-Particles smaller than 3 in. (75mm) in diameter and larger than the No.
4 sieve (3/16 in. or 4.75 mm).
Sand-Particles smaller than the No. 4 sieve (3/16 in. or 4.75 mm) in diameter
and larger than the No. 200 sieve (.075mm particles smaller than the No.
200 sieve are not visible to the naked eye).
Fine-grained soils
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Organic Soils
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d.
Soil which are mostly organic may be described as organic material.
Partly organic soils, which are largely mineral soil types, are described as
the predominant soil modified by the word “organic,” e.g., organic silt.
Soil Texture and composition
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Soil texture
Composition
2.
Geotechnical Processes
a.
The concept of Stress and Strain
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Stiffness = Stress/Strain
The stiffest possible material is very desirable in a track
subgrade. Stiff materials limit the deflection under load,
reducing track roughness and occurrence of track defects.
The stiffness of a subgrade may be increased by following:
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Replacing clay soils with cohesionless (sand and gravel) soils.
Compaction or densification.
Draining water to reduce positive pore pressure and increase soil
strength.
Vegetation management to include negative water pressures.
b.
Effective Stress
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c.
Soil is comprised of particles.
Cohesion only occurs in clays.
Most soils are a mixture of sand, silt and clay. The
shear resistance of most soils is achieved from a
combination of cohesion and friction which the
relative importance of each component depending on
soil texture.
The effect of Porewater Pressure
Effective pressure =Total pressure (or total stress) –Hydraulic pressure
In case of soils above the water table, the porewater pressure is
usually negative and is termed as soil suction. This negative
value may temporary tough, and may disappear as a result of
thawing, infiltration or pore pressure generated by traffic.
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d.
Clays
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e.
Sand and Gravel
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f.
Lacks cohesion and also lacks the ability to drain quickly.
Soil Behavior Under Rapid Loading
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h.
The ability to drain and rapidly gain strength is why these materials are preferred
for work construction.
Silt
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g.
The strength of clay is dependent both on cohesion and on the effective stress
between soil particles. The “stickiness” in clays results from cohesive bonding that
occurs between clay particles. It results in an “effective cohesion” that contributes
to the soil strength.
Under rapid loading, the strength of clay will remain constant. By contrast, the
strength of a sand or gravel will increase, while a saturated silt will loose strength.
Effect of Shear Strain
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The initial density of a soil will induce dramatic changes in soil strength.
d.
Settlement
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Settlement occurs as water is expelled from the soil pores and the effective stress
increases.
Some rules of thumb are useful in day-to-day maintenance activities.
e.g. It is generally accepted that the magnitude of increased settlement will be less than one inch, except on the most
sensitive foundations, if the increase in effective stress is kept to less than 10% of in situ values.
Some other rules of thumb are:
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Settlement of a well-compacted granular fill-1 to 3% of fill height
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Settlement of a loose rock or granular fill on first wetting -5 to 20% of fill height
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Settlement of a fill on a medium dense granular fill-2 to 4% of fill height
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Settlement of a fill across muskeg -30 to 60% of fill height, depending on construction methods and peat type.
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Foundation settlement for hard, over consolidated clays-less than 0.25% of fill height, if preconsolidation
pressure is not exceeded.
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e.
Total settlement is seldom an issue except where clearances, rather, it is the differential
settlement that causes the greatest concern.
Seepage
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Seepage is the movement of water through the soil from a position of higher total head
to a position of lower total head. By Darcy’s Law, Which states that flow (v) through the
soil is proportional to the soil permeability (k) and hydraulic gradient.
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v= ki
Piping