Savannah courier. (Savannah, Tenn.) 1885-1979, 1899-09-08
RAILROADS OVER BOGS,
Devices of Epgineers for Crossing
Dangerous Marshes - Mud
Foundations.


The sinking of section of the main
line of the South Pacific Coast marrow
gauge) railroad short distance south
of the bridge across the entrance to San
Leandro bay opens up new problem In
railroad engineering to be solved. The
roadbed traverses the salt marshes bor-
dering the bay almost all the way from
Alameda to Alviso, and in some parts
these marshes are very soft and cut III
every direction by sloughs. In many
parts the roadbed lies on foundation
of mud, to which there is apparently no
bottom; but so long as there is no room
for the mud to shift or no agent at work
undermining it the roadbed stays in
place. The company has had much trou-
BILE, however. where the recent sub
sidence occurred 1t has subsidized on
more than one occasion before, and It
has taken lot of new material each
time to bring it up to grade. The di1h-
Guilty grows out of the fact that the road
embanllment at that particular point is
swept at its base by swift tidal cur
rent, which undermines the soft mud
stratum and causes the roadbed to slip
in body out of sight, leaving the rails
and ties hanging in the air. The trou-
blesome current is said to have We
locity of IS or 16 miles an hour. 1t is
intended to control it by damming the
source, thus holding the water brought
by the rising tide into the depressed
marsh land in the neighborhood by pre-
venting its outflow.
The marshes in the neighborhood OF
San Francisco and adjacent bays have
perpleXed railroad builders since early
days. In spots the mud is so deep that
attempts to sound it have resulted in
the discovery of no bottom. AT those
points on the north arm of the estuary
OF San Antonia-that is, the arm con
Meeting Oakland creek with Lake Mer
ritt-where the steam railroads serving
Oakland cross, there is at least ITO feet
of soft mud. There the engineers were
forced to rely on suction to support the
trestling, and the spliced piles in TIT
middle of the First street railroad cross
ing are said TO be 40 feet in length ant
are held solely by the suction OF thu
mud itself,
All the piing constituting the foun
dation of the ferry building at th'
| foot of Market street and much OF thu
| piling driven into the made land ol
which the foundations of most of thu
| big buildings in the lower Markc
street building rest are held in place b,
suction. So powerful is this suction o
| the soft mud that a pile driven into j
so far cannot be budged by the stroke
of the heaviest triphammers used in pill
driving, and the end of il will broom un
| der the blows.
The builders of the California Paciii
railroad encountered much trouble will
Il section of soft marsh land adjacent T.
| Suisun. Time after time the entire road
bed sunk not only out of sight but on
of soundings also, and stable founda
ton was only acquired after repeate'
| filling in, the lower stratum of mate
rial being held in suspension, it is he
lieyed, in the body of the mud, suctio
preventing it from subsiding further.
The engineer of the Valley railroa
has made mattress foundation fo
the roadbcd over the Martinez and Sa
Joaquin marshes like the mattres
foundation which Capt. Eads adopte
for the levees constructed by him a
the mouth of the Mississippi river
These mattresses are made of brus
bound together with wire and laid o
the surface of the marsh. Dredger
then lift the mud cut out of tn
trenches on either side and deposit
on these mattresses, thus forming a
embankment that will carry, when thor
oughly settled, many times the weigh
it will ever be required to carry. Thes
mattresses distribute the weight event
over so large an area of the soft mu
underlying the marsh that it does nc
perceptibly affect it, and the embanl
Inent is practically as secure and pei
manent as if it were built on foundi
ton of rock.-San Francisco Chronicle