THE IRRIGATION AGE. 



185 



SHOOTING CEMENT LININGS INTO DITCHES 



By CARL WEBER, C. E. 



President Cement Gun Construction Co., Chicago 



THE amount of water lost by 

 absorption and seepage in 

 irrigation canals and ditches 

 varies with soil conditions and 

 construction details. It may be 

 an exceedingly small amount in 

 old, well silted canals built in 

 loamy soil, and it may amount 

 to 100 per cent in pervious sand 

 and gravel. Very often the loss 

 is so great as to demand the lin- 

 ing of the canal with some suit- 

 able material, and although clay- 

 puddle, wood planking and ma- 

 sonry have been used for this 

 purpose, the adoption of concrete 

 for canal linings has become gen- 

 eral practice at the present day. 



A concrete lining is also used 

 frequently for old canals to in- 

 crease the carrying capacity of 

 the same and to prevent damage 

 by gophers and other burrowing 

 animals. 



The construction of concrete 

 linings is done by a variety of 

 different methods, depending upon 

 the materials available for this 

 purpose, the cross section and 

 general conditions of the ditch 

 and the experience and skill of 

 the builder. The thickness of 

 concrete linings varies from 3 to 

 10 inches. For concrete aggre- 

 gates sand, gravel, crushed stone 

 and stone screenings are used. The 

 proportions of the concrete mix- 

 ture vary widely, and in some 

 cases steel reinforcement has 

 been used in these linings. 



Before the concrete lining is placed it is neces- 

 sary to trim the slopes and bottom of the ditch so 

 that even surfaces are obtained. Then forms for 

 the pouring of the concrete for the slopes must be 

 provided and erected. These forms must be left in 

 place from 24 hours to three days after the concrete 

 has been poured, and therefore if any rapid progress 

 is to be made the cost of the forms is a large item 

 of expense. 



After removal of the forms the surface of the 

 lining must be plastered by hand or given a heavy 

 cement grouting to obtain smoothness and fill the 

 surface voids. As a rule expansion joints are pro- 

 vided in the lining at certain intervals in order to 

 guard against cracks, and different types of such 

 joints Ifave been tried with more or less success. 



A well constructed concrete lining admirably 

 fills the purpose for which it is made. However, 

 owing to the great cost of such work the tendency 

 has been to reduce the thickness of the lining, the 

 quantity of cement used in the mixture and other 

 details to such an extent that a large amount of ex- 



Fig. 1 The cement gun ready to fire. 



A cross-section of the nozzle. 



tremely poor work has been pro- 

 duced in recent years. A good 

 lining must be amply strong to 

 withstand occasional impact of 

 driftwood, etc., and must be so 

 dense as to prevent percolation. 

 Special care must be taken to 

 produce a dense concrete wher- 

 ever alkali is present, for the rea- 

 son that porous concrete easily 

 deteriorates through the action of 

 the alkali salts. It is extremely 

 difficult to obtain a dense con- 

 crete lining on the slopes. The 

 thin layer of concrete poured 

 behind the forms has a tendency 

 to become honeycombed, and in 

 order to prevent this, an excess 

 of water is used in the mixture 

 to produce a sloppy concrete, 

 which pours well but requires 

 very tight and expensive forms. 

 It is a well known fact that an 

 excess of water greatly reduces 

 the strength and quality of con- 

 crete and results in a spongy ma- 

 terial quite different from what 

 constitutes an ideal canal lining. 

 Within recent years great 

 progress has been made with 

 cement mortar linings applied 

 with compressed air by the Ce- 

 ment-Gun process. These linings 

 are, as a rule, reinforced with a 

 woven steel wire mesh of suffi- 

 cient strength to counteract ex- 

 pansion stresses, and therefore a 

 continuous lining without any 

 expansion joints becomes pos- 

 sible. Owing to this reinforcement the lining also 

 possesses a large amount of elasticity and will allow 

 a considerable amount of settlement and deflection 

 without apparent cracks. This is of greatest im- 

 portance for canal sections along hillsides and in 

 filled ground. 



The material is blown, or shot, against the 

 slopes, no forms of any kind are required, and by 

 the force of impact all superfluous air, water and 

 sand are expelled. The result is an absolutely 

 dense and waterproof lining of extreme strength 

 and durability. Large water reservoirs which 

 caused considerable expense on account of leakage 

 have been waterproofed by this process, which is 

 also extensively used for the encasing of steel work 

 for rust prevention and for the fireproofing of 

 wooden structures. 



This work is all of recent origin, and although 

 very little effort has been made so far to introduce 

 the same for canal linings in the United States, a 

 large amount of this work has been done in the 

 1 fawaiian Islands with great success. 



The first of this work was done during the 



