Curved Reservoir Walls. 407, 



Over the whole surface a half-inch layer of mortar is spread, 

 well worked into all corners and recesses, and the first layer of con- 

 crete is deposited thereon while the mortar is still fresh. 



Framing. — The wall is carried up in 3 feet courses, which are 

 deposited in 12-inch layers, each somewhat ahead of the other. 

 The frames used are 10 feet long by 3 feet 6 inches high, and suffi- 

 cient frames are provided to carry a course the full length of the 

 dam. These frames are held in position by profiles, which, as the 

 wall rises, are secured thereto by means of bolts, with nut at each 

 end, built into the wall and spaced at intervals of 10 feet horizontal 

 and 3 feet vertical. When a course is completed the bolts are un- 

 screwed, leaving the inner nut in the wall, and the profiles and 

 frames are lifted 3 feet, leaving a 6-inch overlap on the completed 

 course. The bolt holes in which the nuts remain are filled with 

 mortar as soon as the framing is removed. 



The frames on the uj>.stream side are curved to the mean 

 radius of the face of the wall, while on the down-stream or battered 

 face arrangements have to be made for the increasing radius as the 

 work is carried up. 



The concrete after being mixed is conveyed to the wall on a 

 narrow-gauge tramway, which allows of the skips passing between 

 the mould boards on the thinnest part of the wall, and is dropped 

 therefrom intO' position. 



Materials — The proportions of the ingredients of the concrete 

 used in the body of the wall are as follows : — 



4^ cubic feet of cement. 



12 ,, ,, ,, sand. 



10 ,, ,. „ shivers, ^-inch gauge. 



13 ,, ,, ,, metal, i|-inch gauge. 



On the uj>-streani or water face of the \vall a 6-inch facing is 

 deposited of the following proportions : — 



45 cubic feet of cement. 

 10 ,, ,, „ sand. 

 10 ,, ,, ,. shivers, ^-inch gauge. 



Plumstones to the extent of one-third of the total bulk are used, 

 and in no case does the size exceed that which can be handled by 

 two men. They are bedded in the concrete with their thinnest edges 

 downwards, and the concrete is w^ell rammed in between each stone. 

 The plumstones project above each course as finished, so as to form 

 a key for the next course. 



When the frames are removed from each course, and while the 

 ■concrete is still green, the whole surface is floated over with neat 

 ■cement, which forms an impervious skin on both faces of the wall. 



Scour and Supply Pipes. — A cast iron scour pipe of about 24 

 inches diameter is placed in the lowest portion of the wall controlled 

 iby an ordinaryi .sluice valve. 



