a. In a sidehill cut, the roadbed surface lies partly below and partly above the normal
level of the ground. The earth which must be removed in making this cut may generally be
dropped over the other side of the proposed track line to provide fill material.
b. In a through cut, the entire roadbed lies beneath the normal surface of the ground.
c. In a fill, the entire roadbed lies above the normal surface of the ground. Fills are
used to avoid building bridges over ravines and other low areas.
d. Slopes are inevitable wherever there are cuts and fills. And wherever there are slopes,
you can expect to have erosion and stability problems. Although the design of cuts, fills, and
slopes is a construction problem that does not come within the scope of this text, the track
supervisor who is well informed on design can prevent the necessity of major repair work and
can make minor repairs that poor design creates. Design of slopes as used in cuts and fills
depends upon a knowledge of soil stability and rock formation. A few simple rules to guide the
track supervisor are given below.
(1) Ordinary stable soil may be sloped at a ratio of 1 1/2 horizontal to 1 vertical (1
1/2:1) without danger of sliding. Rock may be sloped at a ratio of from 1/8 to 1/2 horizontal to
1 vertical, depending on the formation and composition of the rock.
(2) Cuts are sometimes made through combinations of rock and soil. When this
occurs, the slope changes at the point where rock changes to soil in the cut, as shown in part C
of figure 2.2. The rock is at the lower section of the cut.
e. Erosion is one of the things that the track supervisor must constantly guard against.
Unprotected slopes in a cut may wash away in heavy rainfall and cover the track with dirt.
Operations must be halted until it is removed. On a fill, a washout may leave the track
unsupported, again bringing operations to a standstill until repairs are made. Commercial rail
lines rely to dependability for business, and military lines, being main supply routes, must be kept
open. Therefore, such occurrences as washouts must be avoided.
Three ways of preventing erosion of slope walls are intercepting ditches and dikes,
inducing plant growth on the slopes, and building retaining walls.