Daily camera., 1899-08-16
OVER THE MARSHES.
How Engineers Build Railroads O
Mud FoundatioaA
Desso0less Dogs Are DstAGeA Over ~
The Use Of Brush Mattresses
SAne Di0salt UaAss-
Hrr1 tAkin4s.


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 in
every direction by sloughs. In many
parts the roadbed lies on foundation
Of mud. to which there is apparently no
bottom: but 80 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
time to bring il up to grade. The diff
Guilty grows out of the fact that the road
embankment at that particular point is
swept at its base by a 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 ve-
locity of IS or l6 miles an hour. II is
intended TO control ii by damming the
source, thus holding the water brought
by the rising tide into the depressed
marsh land in the neighborhood by pre-
venting it's outflow. -
The marshes in the neigh borhood of
San Francisco and adjacent bays have
days. In spots the mud is SO deep that
attempts TO sound II have resulted in
the discovery Of no bottom. Al those
points on the north arm of the estuary
OF San Antonia-thnt is. the arm con-
Meeting Oakland creek with Lake Mer-
ritt-where the steam railroads serving
Oakland cross, there is at least 1l0 feet
OF soft mud. There the engineers were
forced to rely on suction TO support the
tres,line. and the spliced piles in the
middle of the First street railroad cross
ing are said to be ITO feet in length and
are held solely BY the suction of the
mud itself.
All the piling continuing the foun-
dntion Of the ferry building at the
foot of Market street and much of the
piling driven into the made land on
which the foundations of most of the
big buildings in the lower Market
stree, building rest are held in place by
suction. So powerful Is this suction of
the soft mud that pile driven intait
SO far cannot be budeed by the strokes
Of the heaviest triphammers used in pile
driving. and the end Of II will broom un-
der the blows.
The builders OF the California Pacific
railroad encountered much trouble with
n section of soft marsh land ad jaccnt to
Suikun. Time after time the entire road
bed sunk not only out of sight but out
Of soundings also, and a stable founda-
ton. was only acquired after repeated
filing In. the lower stratum of mate
rial being held in suspension. it is be-
lieved. in the body OF the mud. suction
preventing il from subsidinR further.
The engineer of the Valley railroad
has made a mattress foundation for
the roadbed over the Martinez and San
joaquin marshes like the mattress
foundation which Capt, Eads adopted
for the levees constructed by him at
the mouth OF the Mississippi river.
These mattresses are made of brush
bound together with wire and laid on
the surface Of the mArsh. DrcdHers
then lift the mud cut out of the
trenches on either side and deposit it
on these mattresses, thus forming an
embankment that will carry. when thor
huNhly settled. many times the weight
II will ever be required to carry. These
mattresses distribute the weight evenly
over 40 large An area of the soft mud
underlying the marsh that it does not
perceptibly affect ii, and the embank-
nsent is practically as secure and per
manent Is IL it were built on founda-
ton Of rock.-San Francisco Chronicle.