A REPERTORY OF
INDUSTRY, SCIENCE, AND ART;
AND A RECORD OF THE
PROCEEDINGS OF THE CANADIAN INSTITUTE.
COUNCIL OF THE CANADIAN INSTITUTE,
AND FOR SALE BY A. H. ARMOUR & Co., TORONTO; JOHN ARMOUR, MONTREAL; PETER SINCLAIR, QUEBEC; JOHN DUFF, KINGSTON; AND A. A. ANDREWS, Jr., LONDON, C. W.
All Communications to be addressed to the Editor of the Canadian Journal, Toronto. Remittances to be sent to the Treasurer of the Canadian Institute.
TORONTO, JUNE 1855
On the Action of the Ice upon the Bridge at Rice Lake
BY T. C. Clarke, C. E.
(Communicated to the Canadian Institute, April 21st, 1855)
The bridge of the Cobourg and Peterboro' Railway over the Rice Lake, in the county of Northumberland, is perhaps the largest Railway bridge on this continent, and one of the largest in the world, --its total length being a trifle over two miles and a half. The Railway crosses from the Cobourg shore to Tic Island by a pile bridge of 3,754 feet in length. Here it curves a little, the deflection being 24°. From Tic Island to the north side of the main channel, a distance of 2,760 feet, there is a succession of wooden cribs 10’ x 20’ in size, sunk eighty feet from centres, filled with stone, and carrying a superstructure of that class of bridge known as "Burr's Truss."
In the channel, there is a pivot draw on a turntable, supported by a pier 20' X 40' in size, and giving two openings of fifty feet each. The bridge is raised on an incline from each end towards the draw, and the spans immediately next to it, give a clear headway of twelve feet, to afford a passage for the cabins built upon the rafts which come down the Lake.
From the end of the truss bridge to the Indian village shore, a distance of 6,728 feet, is a pile bridge, similar to the other, except that it is strengthened every five hundred feet by a crib 10'x 20' in size, loaded with stone. The cross section of Rice Lake accompanying this paper, shows these dimensions of the bridge.
The bottom of Rice Lake is black mud, in a semi-liquid state, and capable of affording no support to piles. This sometimes reaches nearly to the top of the water, and sometimes there is a depth of ten to fifteen feet of water before reaching it. It affords nutrients to the wild rice (Zizania aquatica. L.), from which the Lake takes its name, and which grows in large patches in such luxuriance that it is difficult to paddle a canoe through it. Under this black mud there is a stratum of very hard and compact sand, overlaying the clay.
The depth of water and mud averaged from the low water level, shown in the section, is about fourteen feet south of Tic Island, and sixteen feet between the Truss bridge and the Indian shore. The total rise and fall of the Lake is six and a half feet.
The piles are driven through the sand and a little into the clay, in some instances; generally, however, they are driven an average of ten feet into the sand, which was a difficult process; the pile not going more than two inches at a blow, from rams weighing 18 cwt., falling through forty feet leaders, after it had begun to penetrate this sand.
It will be observed that from Tic Island to the channel, where was evidently the ancient bed of the river, it is deeper than the rest of the Lake, being an average of twenty-eight feet from low water mark. In the channel it is thirty-six feet from low water mark, and forty-two and a half feet from high water mark to the hard bottom. This depth rendered an ordinary pile bridge impracticable, and accordingly the truss bridge, resting on crib piers, as before mentioned, was designed to carry the Railway over this part of the Lake.
The mode of construction was as follows:-Four long piles were driven and capped, to bear the vertical pressure of the bridge until the cribs could sink to their bearings. They alsoserved as guides for the cribs, which were built around them, 10' x 20' in size at top, and battening 2" in 12" at the ends, and 1" in 12" at the sides. They were made of square timber above and round below water. They were sunk to their places through the ice in winter, and then loaded with boulders, collected along the shores.
The construction of the pile bridge will be seen from inspection of the accompanying drawings. The piles, of which the centre pair were white oak, the outside pan and the spur piles in some cases pine or tamarac, were driven, and capped with pine caps 12x12. The spur piles were driven with a leaning machine, so that their tops stood about four feet from the others. They were then drawn up by strong tackle, and secured with 1" round bolts. The corbels are fastened to the caps and piles by 1" square rag bolts three and a half feet long. They are notched an inch on the cape. The stringers of pine, 12” x 18", are secured to the corbels b, 1" round screw bolts. Ties of 3" oak plank connect the stringers together on top.
The quantities of materials in this bridge are as follows:
184,000 lineal feet of piling.
138,000 " " round timber in cribs.
644,000 feet B. M. square " "
1,932,000 “ “ “ “ in bridge.
250,000 Ibs. iron in bridge.
20,000 yards stone in cribs.
The total cost of the bridge bus been not far from $175,000.
It remains now to describe the effect which the ice has already had upon this structure, and to consider what are its future prospects of stability and permanency.
It was predicted by many persons, previous to commencing this undertaking, that no structure could possibly be built which could resist the power of the ice in Rice Lake,--which forms to the thickness of two and a half feet; expands with such force as to "buckle" up into high ridges, from the heat of the noonday sun; and contracting again in the cold nights, cracks and splits with a noise like that of artillery, and with a tremendous power which, as they declared, no artificial structure could resist. Moreover, they said, after the ice has “taken", the Lake rises some two or three feet, and the ice, being frozen to the piles, must inevitably drag them all out.
To these evil forebodings it was replied that it was not supposed that a pile bridge could sustain the thrust of the ice for any length of time; it might be disturbed and thrown out of line and level, but notwithstanding it could serve to carry the trains across the lake until such time as it could be tilled up with a solid embankment. It was not expected that it would last for ever; but if it lasted long enough to form a means of communication across the Lake until it was filled up from dirt wagons, that would be a great advantage,--sufficiently important to justify the cost of the bridge. To be sure, if the Company had plenty of time, and unlimited means, it would be better to till the Lake up as they went along, leaving only a passage for the waters; but, in their circumstances, this was entirely impossible, for it would have required such a large immediate outlay, with so remote a prospect of remuneration, that the project would have been killed.
The bridge was accordingly built, and the result has thus far justified the anticipations of its projectors; while, on the other hand, the prognostications of those who feared danger from the ice have been partially realized. The bridge has been much twisted and shaken, but although its straightness and regularity have been destroyed, it still stands in its place, fully equal to the task of carrying unusually heavy engines over in safety. If the filling in of the Lake is hurried on with as fast as possible, it can be completed before next winter, and then there will be no danger to be apprehended for a long time to come.
The manner in which the ice has affected the bridge is somewhat singular. As was predicted, there has been evidently a raising of the entire field of ice since its formation. The effect of this during the winter of 1853-4 was to draw out a few piles, near the Indian shore, which had been imperfectly driven, and to raise the whole, north of the truss bridge, some six or eight inches, except where it was held down by the cribs, sunk every five hundred feet. This gave it rather an undulating surface, and they were obliged to raise and block up the stringers at these low points. It is proposed to prevent this raising of the ice, by putting flash-boards on the dam at Crook’s Rapids, at the lower end of Rice Lake, and raising it some two or three feet before the ice takes. As more water flows into the Lake it would be necessary to gradually take off the boards, and thus keep it at the same level.
When there is no snow on the ice, the heat of the sun in the middle of the day expands it, and it moves slowly, carrying the bridge with it. When night comes on and the temperature falls, it contracts again, and cracks and splits in a surprising manner.
One of these cracks took place at a very acute angle across the bridge, throwing one portion up stream about eighteen inches, and the other down as much.
The worst injury that the bridge has received was about the1st of January of this year. The weather was particularly trying, the days being warm and the nights very frosty; and this, it must be observed, is the only kind of weather in which the bridge takes injury,-uniformly cold or warm weather not affecting it.
On this occasion there appeared to be an expansion of the ice from the channel towards each shore, and the effect was irresistible. The pile bridge north was thrown towards the Indian shore; but owing to the number of cribs in it, it moved but little. The truss-bridge was pushed towards Tic Island, so that the last span slid four feet upon the solid abutment. South of Tic Island, the pile bridge was crowded over toward the Cobourg shore,--so much, that at the place where it parted, near the Island, the stringers were drawn apart nearly seven feet, so that they fell from the corbels. The piles were leaned over, and where the thrust met the resistance of the shore, it crushed up the solid 12” x 18” stringers, and turned them into splinters, and bent the iron rails double. This has all been since repaired, and the trains are now crossing regularly.
From inspection of the drawing, No. 6., accompanying, it will be seen that nearly three-fourths of the length of the piles are unsupported, and only one-fourth of them is in the solid ground. When the thrust of the ice comes at the water-line, it exerts a very powerful leverage, and it is not strange that the bridge should yield.
The dotted line in fig. 6 shows the outline of the embankment which it is proposed to make. This, it will be seen, will support the piles very much, and render it almost impossible that they should be moved. In course of time, as the piles decay, it will be found necessary to till it up to the level of the track. The embankment must then be protected from washing away by a slope wall of loose stones and brush. Another very ingenious method of protecting it has been proposed, which would be less expensive than a slope wall. This is, to drive piles some twenty feet from the bridge in rows parallel to it on each side, cut them off below the depth to which the ice forms, and chain to them a succession of spars forming a boom along the embankment on each side, and twenty feet from it. It is believed that this would render the water calm enough inside of it to prevent washing away the bank.
The material on the south side of the Lake is admirably adapted for filling, being a tough species of clay, or rather hard pan, which, when thrown into the water, consolidates, and packs around the piles, instead of washing away. A few hundred feet of embankment was made of this material in the summer of 1853, and has stood perfectly well ever since.
The Rice Lake Bridge was designed and built under the immediate superintendence of Ira Spalding, Esq., and reflects great credit on that gentleman’s skill and judgment as an Engineer. The contractor was Mr. Zimmerman, whose well known energy was severely taxed to supply so large an amount of materials, and carry on the work to successful completion, in spite of sickness and scarcity of workmen, in the comparatively short space of eighteen months.
THOS. C. CLARKE
Port Hope, April 2nd, 1855.