Evening star. [volume] (Washington, D.C.) 1854-1972, 1885-02-21

SKILL
When Congress, In 1876, under the influence
of the patriotic inspiration OF the centennial
year. made an appropriation for carrying on the
long delayed work upon the Washington ma
tiOnal monument there appeared, to the ordi-
nary observer at least. nothing remaining to be
done but tOquarry the stone and continue build
ing slyward from the point where the maSons
had stopped work twenty years before. Doubts
however. existed. in the minds of engineers as
To the stability of the structure, and provision
was made for an examination to ascertain
whether the foundation sufficient to sus-
tain the weight of the completed structure. AT
the request of the monument commission, the
Secretary of War detailed Lieut. Coils. kurtz,
Duane and Gilmore as a board of engineer Off
GERS TO make the necessary examination. These
officers reported that the foundation was insult
hcient. and IL would be inadviSable to proceed
with the work of construction until it was prop
erly strengthened. The suspension of the work,
h. 1856 may. in the light of the representations
Of these officers. be considered providentiaI. III
money had flowed into the treasury of the Mon
ument society, and the work had been prose
cuted steadily. il appears not only probable, but
almost certain, from the calculations mace py
the engineers. that the structure would nave
So instead Of building skyward 1t was apparent
to the engineers that the first step to be taken
was to build downward
THE OLD FOUNDATION
Z feet s inches below the general level of the
ground about the structure This foundation
% feet inches in thickness and was car
ried up from bottom to top in eight offsets or
steps % about feet rise each, the upper course
being 5S feet Is inches square, 1t was built OF
large pieces of biue>tone gneiSs, put in the ma
sonny a. they came rom the quarry, the inter
sticeS between the ms.-seS being filled with
spawls and n mortar composed largely of fat
lime and Sand. No cement used in the
construction OF the foundation, and no attempt
seems to have been made to give parallel beds
and builds to the pieces of stone used. The
stones were laid as compactly as possible with
the shape they had as they came from the
quarry, large and small being packed in indis
criminately- \ well-hOle feet square passed
down through the center of this foundation but
did not, when the work was resumed, extend
below the bottom of the foundation. though it
had at some time probably been deeper The
weight of the shaft was found by measurement
To- be 23,194 tons, the weight of the foundation
S.139 tons and the weight of earth on the foun-
dation 243 tons, making a total weight of
32.1.6. distributed over foundation bed 6 400
square feet in area. giving pressure upon each
square foot of soil under the foundation of
6.O2I tons of 2,24O pounds.
COL. CAsEY's CALCULATIONS.
When Col. Casey took charge of the work at
the monument the plan which was eventually
adopted had not been decided upon. 1t was
then expected that the obelisk would be carried
only TO the height of 525 feet. In his first re-
port to the joint commission for the completion
Of the monument, he said:
SHOULD the obelisk be carried to the height of
52o feet and the earth filed upon the founda-
ton 10 the level of the bottom of the shaft, the
pressure upon the bed of the foundation would
be as follows:
Weight of shaft ---....... .........4 ,421 tons.
Weight of foundation ..........-.......... S,139
W eight of roof and stairs .--..--......-.. $50 4"
Weight OF earth on foundation....... o,2S3 d"
Total .................... 1O93
Dr. S.452 tons per square foot OF area OF bed of
foundation Surprising the shaft to be acted upon
by q Wind-preSSure of 80 pounds to the square
loot the pressure along the outer edges of the bed
OF the foundation would be increased to 9.941
tons per square foot There are far greater pres
sufe> per square foot than the Kind of material
pressed has been know TO sustain. and il is not
believed that the monument could be carried To
the desired height upon foundation of no
ent one'
THE PROBLEM GIVEN To COL. CASEY.
After the board of engineers had made its
report, Lieut.. Col. Casey was on June %, 1873,
directed to report to the joint commission. and
since that date has had charge of the work at
the monument. The task before Col. Casey was
one that might well have appalled, the stOutest
hearted engineer. Practically q founda-
ton had % be built under a huge stone struc-
ture 156 feet high and weighing 81. 900 tons.
The structure had TO be undermined and the
earth upon which ii rested replaced to a consid-
eraoie extent with substantial masonry. Mem
bers OF the Senate committee on public build
1ngS and grounds expressed doubts as to the
possibility of accomplishing this feat and some
Of them even apprehended that the whole struc-
ture would tumble over Congress authorized
the expenditure of $4,000 upon the work of
strengthening the monument, as that was the
sum asked TO carry out plan which some per-
son had presented to- Congress- contemplating
the building of a series of horizontal arches.
Col Caseys first work was to make careful
measurements and calculations. so as to deter
mine what was needed He experimental to
see now much more weight could safely be
added To the structure as it then existed, and
came to the conclusion. on account of the nature
of the foundation and the character of the soil,
he INN Sn6
The board of engineer officers who had previ-
ouSly examined the monument concluded that
the structure had settled some. The first builders
OF the monument had used bench mark
which the engineers assumed to be the stone
near the monument, known as the Meridian
stone. Measurements made from that showed
that the structure had settled. Members of the
Monument society, however, contended that
that was not the right stone. As the old records
were lost, the point could not be definitely de-
cided. When Col Casey assumed charge of the
work all the plans for strengthening the founda-
suggested for securing the foundation are COM
Prised under two general classes, one proposing
TO hoop In the earth beneath the foundation, so
as to prevent the lateral displacement under
the additional load to be brought upon the bed
OF the foundation; the other TO underpin and
extend the surface Of the base of the foundation
90 as 10 distribute the load over a greater area
within the limits Of resistance Of the soil to be
pressed.
THE PLAN ADOPTED.
Col. Casey after carefully examining all the
plans proposed rejected all. He began work at
once upon new plan, and in less than a month
had worked out all the details. His plan fell in
the second Of the two classes named, contem-
plating the extension of the foundation so as to
widen the area OF pressure or the bearings of
the structure. The work upon the foundation
commenced In 1873, was pushed to success
1ul completion In May, 1880, at net cost OF
S99,913. Though Congress had at first author
Ned the expenditure of $50, 600 upon this work
Col Casey's plans, involving a larger expendi-
sure, were subsequently approved.
HOW THE WORK WAS DONE
Briefly, IL may be said, that the foundation
was deepened Is feet inches, and extended In
all directions % feet inches. Seventy per
centum OF the earth under the old foundation
was dug away and replaced with a mass con-
crete extending g feet within and % feet 8 in
ches without the line OF the outer edges of the
old foundation. This mass of concrete extended
B feet under the outer face of the shaft at Its
lowest Joint, where il rests upon the foundation
This gave new foundation 126 feet inches
square, and enlarged the area OF the foundation
nom 6,4OO square feet To 10, 900 Quare feet To
distribute the pressure of the shaft over the new
foundation, the old rubble-stone base was torn
Prom under the walls OF the shaft and replaced
the new concrete slab. In doing this 81 per
cent OF the cubical contents of the old stone
foundation was removed and 4 3 per cent of the
area OF the shaft undermined. The foundation
as completed extends 50 feet 10 inches below
the shaft and inches below the permanent
level OF water at the site of the monument The
weight OF the completed structure is as follows:
weight or foundation and earth
upon .S6 OIL TONS
UEiO m - par oil