In 4.1.0 Right of Way I discussed how a railroad company got the land that it operates on. In 4.1.1 Roadway Roadway is planned and constructed based on the roadway engineering plan. The plan identifies all the issues involving construction, to include:
1) Geography: that is the roadbed, embankment, cuts and fills, drainage, and
2) Track structure: Ballast, Ties, Rails, Turnouts, Track crossings (Special works), and other associated materials.
On this page we will discuss roadway engineering and construction of embankments.
Prototype Information
Formation of Embankments.
Embankments are made of local materials and built in layers. Generally, stone and heavy material should form the slopes and finer material be placed in the center of the embankment. The more solid and compact the roadbed is made, the more impervious it will be and the better it will drain water and support the loads brought upon it by traffic.
- On the Great Northern Railway all single track roadbed was 14 foot wide on tangents and 16 foot wide on curves.
- On the Northern Pacific Railway all single track roadbed was 16 foot wide.
- On the Milwaukee Road all single track roadbed was 18 feet wide.
- On the Union Pacific the width is differentiated based on main or branch line and the standard changed over the years. In 1906 - all roadbed on embankments were 16 foot wide. In 1927 the main line was 18 foot wide, a branch line was 17 foot wide - with a caveat that when embankments greater than 10 foot in height the roadbed would be 24 foot width. In 1967 the main line was 28 foot wide, the branch line was 20 foot wide.
Slope of embankment
The slope of railway embankments varies from 1 (horizontal) to 1(vertical) for rock fills to 11 to 1 for ordinary earth, and easier slopes for soft material like clay soil, when such must be used. By building up a rough dry wall on the exterior of a rock fill it may be made to stand at a slope somewhat steeper than 1 to 1. Ordinary earth will stand for a time at a slope steeper than that, but under the action of the rains, the winds and frost it will gradually wear down to about 11 to 1.
Excavation slopes. The Union Pacific has listed four generic excavation slopes ratios based on slope materiel
- 0.5:1 for solid rock
- 1:1 for fractured rock
- 2:1 for common materiel
- 3:1 for sand
The WWSL
There is three true embankment on the WWSL:. 1) the Smith Canal embankment, 2) the Polson Canyon embankment and 3) the Satsop River Bridge South river bank.
Project Process
Smith Canal Embankment
Modeling Information
Smith Canal is located in the Chehelis River floodplain just south of the Demaine Yard. (Section 4 - Chehelis River Section).
The Smith Canal right of way is double track - one track for the 2nd Division main line and the second track to be a DCC programming track (the DCC control center being located directly below this section). As such, the roadway will conform generally to the right of way indicated below.
Due to right of way constraints, the outside (aisle side)
portion of the embankment will be to engineering specification, ending
at the fascia. The inside curve of the embankment will be sloped 1 to 1,
indicating that there has been some shrinkage of the embankment over
time and the relaxed engineering standards of the WWSL.
Construction
The basic structure of the embankment is a standard module construction minus the two 1"x 3"s. (The embankment height is approximately 4 inches high).
The roadbed template is laid out on the extruded styrofoam with the outermost track tie line at the 4 inch mark and the main line track at the 6 inch mark. The interior embankment slope is WWSL Common Standard (1.5:1). The slope is calculated and layed out ready for cutting.
I clamped the foam panel to the section, and temporarily secured the fascia. I used a wire saw from my Boy Scout camping days to cut the profile on the outside (aisle) edge. One hand followed the roadbed line, the other hand followed the vertical line of the fascia board.
The inner slope (and outer embankment slopes not located along the fascia panel) were cut with a hot foam cutter to the masonite sheet. The masonite sheet exposed by the foam cutting is cut away with a saber saw.
The resulting embankment module subset is
permanently to the base panel. Open areas under the masonite are filled
with additional extruded styrofoam and hot wire profiled as necessary in
preparation for laying track and scenic development.
Polson Canyon Embankment
Modeling Information
Polson Canyon is located on the WWSL 1st Division (Section 13 - Polson Canyon Section).
The Polson Canyon right of way is a single track main line.
Construction
The basic structure of the roadway is the alternate module construction.
The interior embankment slope (1.5:1) is calculated and layed out ready for cutting. The roadbed template is laid out on the extruded styrofoam.The inner embankment was cut with a hot foam cutter and masonite sheet exposed by the foam cutting is cut away with a saber saw. Open areas under the masonite are filled with additional extruded styrofoam and profiled as necessary for scenic development.
Project Process
Satsop River Embankment
Modeling Information
Satsop River is located on the WWSL 1st Division (Section 14 - Satsop River Section).
The Satsop River right of way is a single track main line. The main line was extended in 1931 to access new logging areas. An embankment was necessary to cross the Satsop River.
Engineering
The approach to the Satsop River from Polson Canyon required the construction of a bridge embankment. That embankment was built along WWSL Common Standard.
The basic structure of the embankment is standard module construction minus the two 1"x 3"s.(The embankment height is approximately 4 inches high).
The embankment template is laid out on the extruded styrofoam with the main line track at the 12 inch mark, and the abutment face aligned with the point of tangentcy. .
The hidden embankment slope (not observable from the fascia) were selectively compressed vertically. The inner embankment was cut with a hot foam cutter and the masonite sheet exposed by the foam cutting is cut away with a saber saw. Masonite sheet exposed by the foam cutting are cut away with a saber saw. Open areas under the masonite are filled with additional extruded styrofoam and profiled as necessary in preparation for laying track and scenic development.
See 5.5.3 Embankments for additional information and scenic development.
Reference
UP Double Track Common Standard
UP Rip Rap Protection Common Standard
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