35— CURVED COXXRETP: RESERVOIR WALLS AS 

 CONSTRUCTED BY THE PUBLIC WORKS 

 DEPARTMENT OF NEW SOUTH WALES. 



Bv William Craig, A.M. Inst. C.E. 



During a recent visit tu Australia the writer was much impressed 

 with a number of Reservoir Walls which had been constructed on 

 the cur^•ed or arched principle on the designs of Mr. C. W. Darley, 

 M.I.C.E., formerl} Engineer-in-Chief to the Public Works Depart- 

 ment, New South Wale.s, from uho.se valuable paper on this subject 

 -read before the Engineering .section of the Royal Society (if New 

 South Wales in December, J900 -and through the courtesy of his 

 .successors in the Department, the following particulars have been 

 obtained. 



After several Wills had been succe.'--sfully constructed or. gra\ iiy 

 sections by the Department, it became necessary in the case of 

 smaller t(nvns, where the cost of a gravity r>ectioii was prohibitive, to 

 <lesign a more economical f')rm of Re.sen-oir for storage purposes, 

 and. guided by the success which had been attained in America and 

 elsewhere of building Walls <jn the cur\ed principle, the Depart- 

 ment decided to adojA that .sy.stem whether the site selected jjroved 

 favourable for such constructi(Hi. 



The conditions i.ecessar\ for the adoption of the curved wail 

 in place of a gravity section are (r) the selection of a comparatively 

 narrow gorge or river channel, (2) solid rock foundation throughout 

 and (3) rock slopes on either side for abutments. The third condi- 

 tion has not always been found practicable, and in such (-a.ses the 

 arched section abuts on a wall of gravitv section which answers the 

 same purpose. 



There are now seven curved concrete Reservoir walls in New 

 South Wales with radii var}ing from roo feet to 300 feet, all of which 

 have l)een designed on the fr)llowing principles (extract from Mr. 

 Darley's paper) : — 



" A curved dam with solid rock abutments being subject to the 

 " same stresses as a hollow emi)t\- vertical cylinder of the same 

 " radius and surrounded on the outside by water of the same depth 

 " as that impounded by the dam. the formula for ' resistance of 

 ''cylinders to a crushing pressure, viz., V=-\l or ^,;, has been used 

 ** for calculating the thickness of the wall 



where 



P = ^^'aler pressure in tons per square foot. 

 T = Thickness at any point in feet. 

 R = Radius in feet. 



