60 



BULLETIN 120, U. S. DEPARTMENT OF AGRICULTURE. 



Asphalt 



Mortar. 



coated with asphalt "before being inserted it may prevent leaks. The 

 device likewise secures a fairly good bond. 



(4) A pliable metal sheet protected from rust, of the form shown in 

 figure 3, d, has also been used for such purposes. When section A is 

 being laid the metal assumes the form of a right angle, the vertical 

 part being placed against the form. Before section B is laid the 

 upper portion of the vertical is bent down to a horizontal position, as 

 shown. 



(5)|pn the Ridenbaugh Canal of the Xampa and Meridian irrigation 

 district, Idaho, tar paper was inserted between the abutting joints, 

 which are spaced 16 feet 3 inches apart, and a good bond between the 

 sections was secured by short ^--inch steel rods (fig. 3, e). 



(6) To overcome the objection of projecting rods in laying by the 

 method just described, the plan of bonding shown in figure 3,f, has 



been devised. A socket is formed in sec- 

 tion A by means of a short ^-inch pipe, 

 and into this is inserted one end of a steel 

 rod five-sixteenths inch in diameter and 

 double the length of a pipe. This con- 

 trivance adapts the joint to the alternate 

 method of laying, as illustrated in fig- 

 ure 3, a. 



(7) The form of joint used by the writer 

 on the Snake Ravine retaining walls of the 

 Turlock irrigation district of California is 

 shown in figure 3, g. In laying the lining 

 in alternate sections the joint with its con- 

 cave surface ma)' be coated with hot asphalt or fined with tar paper 

 before the adjacent section is laid. 



(8) In lining the Davis and Weber Counties Canal in Utah, a thin 

 strip of wood coated with asphalt was placed in each joint and ex- 

 tended through about two-thirds the thickness of the fining. The 

 specifications called for the withdrawal of these strips and the filling 

 hi of the spaces with hot asphalt, but this was not done. As a result, 

 many of the wooden strips became loose and project more or less 

 above the surface of the lining, thus retarding the flow of water. In 

 other respects the joint has proved satisfactory. (See fig. 3, Ti.) 



(9) A somewhat similar joint (fig. 5) was used by the engineers 

 of the Patterson Land & Water Co. and the East Contra Costa 

 Irrigation Co. On both canals, to which references are made else- 

 where, the wooden strips were removed and the spaces filled with 

 hot asphalt to within three-eighths inch of the surface, the re- 

 maining space being filled with cement mortar. When inspected 

 by the writer during construction he questioned the advisability of 

 so wide a joint, and was advised that a smaller joint could not well 

 be filled with asphalt. 



Fig. 5. — Sketch of joint used for 

 concrete lining, Patterson Land 

 & Water Co., Patterson, Cal. 



