Canadian engineer . i 31st February 22, 1912. THE CANADIAN ENGINEER 313 12 29 4 5 6 22 23 January 1911. 3rd 3rd 5th 6th loth 13th 15th —59-64—57—59—62—64—60 TJie only remarkable or unique feature of this job wasthe number of times the caissons ran away—or got beyondcontrol an-a sank in the silt up to the deck. This happenedso often that whenever a caisson was undermined, ready forsinking-, the entire gang came out instead of staying in theair chamber as usual. Otherwise there would have beenmuch loss of life. This resulted in a loss of about 8 or 10 hours each time,as it, of course, took time
Canadian engineer . i 31st February 22, 1912. THE CANADIAN ENGINEER 313 12 29 4 5 6 22 23 January 1911. 3rd 3rd 5th 6th loth 13th 15th —59-64—57—59—62—64—60 TJie only remarkable or unique feature of this job wasthe number of times the caissons ran away—or got beyondcontrol an-a sank in the silt up to the deck. This happenedso often that whenever a caisson was undermined, ready forsinking-, the entire gang came out instead of staying in theair chamber as usual. Otherwise there would have beenmuch loss of life. This resulted in a loss of about 8 or 10 hours each time,as it, of course, took time to send a man down the shaftwith a pail to clear away enough material to makQ room forthe bucket and gang. The following are the caissons that ran away: —Caisson No. 33—Dec. ist, igio6th 34343426 3410243028II28 Qthloth15th15th15th17th27th28th28th30th (Broke 35 ft. above ) Full of water. Dropped five feet. 29—Jan. 3rd, 1911. Dropped five feet. 12 3rd Dropped five feet. 4 5th Dropped five Fig. 5. On December 21, 1911, showing grillage concretein place. Caisson No. 34 on December loth sank suddenly whilean inclined timber brace was in position. This brace toedagainst Caisson No. 30 and was acting against the top ofNo. 34. The result was that No. 34 was broken in twoabout 8 feet below the ground, or 35 feet above the cuttingedge, requiring the removal and rebuilding of the upperportion which was, of course, then as good as the original;the cost of the accident being borne by the contractor, as amatter of course. A new method of filling the working chamber was pro-posed and adopted by the writer in view of his experience inremoving caissons already sunk where he had found ihatconcrete benched and therefore iput in rather dry wasvery poor, and concrete put in very wet was apt to shrink from one-half to one inch leaving a space between the (W ^and concrete. This shrinkage appears to go on for 12 to 18 hours whilethe concrete is setting and drying, so on
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