12

THE CAIRO BRIDGE.

gust 17. It was towed to wharf boat, where concreting was com-menced. On September 30 the caisson was placed in its proper positionand sinking commenced on October 8. The crib with its concretefilling was finished October 15 and the masonry commenced October 16.Sinking was suspended during the month of November, but resumedon the 1st of December, and the caisson reached its final elevation onthe 3rd. Sealing was finished on the 6th, the building of masonry re-sumed on the 18th and the pier completed February 19, 1889.

PIER IX.

Framing of timber for this caisson was commenced September 10,1887 ; cutting edge was placed October 6, and the caisson launchedDecember 1. On the 5tli it was placed in position and concreting com-menced on the 11th. Sinking was commenced December 17. On Jan-uary 4 the river commenced to rise very rapidly and by the next day theconcrete in the crib was submerged. At the same time the sand at thebottom of the river scoured away from the caisson so it became neces-sary to use sand bags. On the 7th the scour had reached two feet be-low the cutting edge at the north-east corner and this scouring con-tinued during the 8th, but was finally stopped by the use of sand bags.On the 10th an attempt was made to pump out the water, and some con-crete was placed in the crib the next day. On the 12th, however, thewater came over the top of the crib. A temporary protection was builtfor the shafts and sinking was continued till the 17th, when the boilersof the pneumatic outfit gave trouble, and the work was stopped. Somerip-rap was placed about the pier at this time. Sinking was resumed onFebruary 9, 1888 ; it was again abandoned on the 18th and no morework was done until August 4. The temporary protection was thenremoved, the mud dredged out of the pockets, and the building of thecrib resumed. Timber work was finished on the 9th of August andconcreting was resumed next day and finished on the 13th. On the14th the masonry was begun, and on September 3 sinking was re-sumed. On the 22nd the pier reached its final elevation and sealing ofthe working chamber was completed on the 26th, on which day themasonry was at once resumed and continued without intermissionuntil October 26, 1888, when the pier Avas completed.

pier x.

The framing of timber for this caisson Avas commenced August 15,1887, cutting edge Avas placed on the 27th and the caisson launched

October 3 and tOAved to place on the 16th. On the 21st concreting Avasbegun. This caisson Avas the second one completed and, like the firstone, Avas built Avith a false bottom. The removal of this caused a greatdeal of trouble and in subsequent caissons the false bottom Avas omitted.The pier Avas not gotten into exact position until the 20th of October.Sinking Avas commenced November 16. On December 6, the criband concrete filling Avere finished and on the 8th masonry Avascommenced. Sinking Avas completed December 26 and the Avorkingchamber sealed January 2, 1888. The masonry Avas at once re-sumed and the pier nearly finished by February 29, Avlien Avork Avassuspended until August 1. The last stone was placed August 14,1888.

PIER XI.

This Avas the first pier to be commenced. The first framing of timberAvas done July 1, 1887. The cutting edge Avas placed on the launchingAvays July 11 and building of the caisson begun July 21. The caissonAvas launched August 20 and placed in position on the 24th. On the26tli concreting was commenced and on September 3 air pressure Avasfirst put on. On October 6 the timber Avork of the crib Avas completedand concrete filling AA'as finished on the 10th. Masonry Avas com-menced on October 11. With the exception of an intermission of oneday, Avhich occurred in taking out the false bottom from Caisson Xsinking Avas carried on AA r ithout intermission until November 10, Avhenthe caisson reached its final elevation. Sealing of the Avorking cham-ber Avas completed November 16. The masonry Avas carried up a shortdistance, after Avhich it Avas built intermittently and finished August 9,1888.

PIER XII.

Excavation for this pier Avas commenced on the 18th of November,1887. Driving of piles Avas begun January 23, 1888, concreting offoundation on the 16th of February, and completed on the 18th. Themasonry Avas begun March 3, and the pier completed on the 19th, thisbeing the first pier to be completed.

PIER XIII.

The excavation for the foundation of this pier Avas commenced May25. On the 5th of June the first pile Avas driven. On the 18th con-creting Avas commenced, and finished three days later. The masonry

Avas commenced on June 25 and finished July 9, this being the secondpier completed.

The full details of the thirteen piers and their foundations aregiven on Plates 5 and 6. The rate of progress of sinking the caissonsis illustrated graphically on Plate 7. Full records of the progressin detail of sinking the pneumatic foundations are given in Appen-dix I.

The concrete used Avas manufactured in a mixer, consisting of a long

1 O o

box of square section, revohdng on an axis passing through the centerof the section. The sand, cement and crushed stone Avere mixed on aplatform and passed into one end of this box through a hopper.The Avater aatis introduced about midAvay of the length of the boxby a pipe running in from the discharge end; after being placedin position, the Avhole Avas thoroughly rammed. The proportionof cement, sand and stone varied from one cement, tAvo sand andtAvo stone, to one cement, three sand and four and eight-thirteenthsstone.

The stone in the piers is all from Bedford, Indiana, exceptthe nose stones, from the starling coping to Ioav Avater, Avhich are ofgranite.

The amount of material in the substructure of the bridge proper isas folloAvs:

1.. ..

11.. .hi ..

iv. .

v. ..

VI ..

VII .

VIII

IX ..

X ...

XI ..

XII .

XIII

Piers.

Total,

Piles,lineal feet.

2 422

2 0652 208

6 695

Timber,feet, B. M.

Iron andsteel, lbs.

Concrete,cub. yds.

Masonry,cub. yds.

91.6

327.7

264 640

120 721

2 052.7

2 579.7

264 640

120 022

2 056.2

2 682.2

264 640

124 644

2 059.8

r-

GO

264 640

129 822

2 029.2

2 875.2

264 640

121 518

2 055.6

2 884.6

264 640

126 570

2 052.1

2 884.3

264 640

127 884

2 070.8

2 891.6

330 990

140 611

2 864.6

3 796.6

330 990

136 031

2 875.9

3 819.9

330 990

134 260

2 845.3

3 801.5

91.6

447 1

91.6

403.5

2 845 450

1 282 083

23 237.0

32 265.6

The specifications for the substructure are printed in Appendix G.