WALLS ON TRIUNE CYLINDER FOUNDATIONS. 133 



Describing the course pursued in constructing the walls of 

 the Queen's Dock at Glasgow, Mr. Deas says, "In proceeding 

 with the substructure, a trench was cut in the line of the quay 

 wall; the bottom of this trench was about 12 inches below low- 

 water mark, when it was made 21 feet wide with the sides 

 sloping upwards with a batter of 1J horizontal to 1 vertical, 

 and over it was erected the necessary staging to carry the 

 travelling-cranes and digging apparatus. 



On the bottom of this trench the shoes were placed exactly 

 in the line of the quay wall, and the space between the outer 

 and inner plates filled up with concrete. The corbelled ring is 

 placed on this shelf, to which it is secured by thirteen IJ-inch 

 bolts; on the top of this ring a wrought- iron washer-band 

 5 inches by inch was sunk into a groove formed in the 

 concrete to take the heads of the bolts. 



The remaining rings forming the complete cylinder are then 

 set one above the other in Portland cement, in three and four 

 pieces alternately, so as to break joint. 



The cylinders being triune, or in groups of three, are placed 

 so as to dovetail into each other, one in front and two behind, 

 and two in front and one behind alternately. The groups where 

 they come together are flattened for a length of 5 feet so as to 

 ensure a good bearing. 



On the completion of the rings forming one group of 

 cylinders, the sand and gravel was dug out simultaneously 

 from within each of the three cylinders by means of excavators 

 especially designed for the purpose, and the sinking proceeded 

 with. From 300 to 400 tons of cast iron weights of the same 

 shape as the rings were generally required to force each group 

 of cylinders down to the required depth of 48 feet 6 inches 

 below the coping level. The average rate of sinking was 12 

 inches per hour. In good working sand, however, as much as 

 3 feet per hour was attained. 



When the group was sunk with the top 9 inches below 

 low-water mark, it was cleaned out to the level of the bottom 

 of the shoe, and each well was filled to the top with Portland- 

 cement concrete. 



To effectually close the apertures formed by the joining of 

 each two groups of cylinders, a timber choke-pile 9 inches square 

 was driven behind anglewise so that a sharp corner bore hard 

 against each of the cylinders. 



