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** ·t::•***"'*"'**-**:'ii:=f::f'******** * * *** * * * * UNITED STATES * * DEPARTMENT OF THE INTERIOR * * BUREAU OF RECLAMATION * * * * * * * HYDRAULIC LABORATORY REPORT NO. 159 .. * * * * * HYDRAULIC MODEL STUDIES F0R THE GLORY-HOLE SPILLWAYS * .. AT * OWYHEE DAM - OWYHEE PROJECT, OREGON-IDAHO * * * ;.\ND * * * GIBSON DAM - SUN RIVER PROJECT, MONTtNA * * * * By * * * F. C. LOWE, ASSISTANT ENGIHEER * * "' * * Denver, Colorado, * Nov. 15, 1944 * * * * * * **** * * ****"'************ ****** u
CHAR LES W. THOMA�
LJ @HARLE S " ' (':... . �. ·, ; ,-, ,, if .·.
UNITED STATES n- r, . DEPARTMENT OF THE INTERIOR LJ BUREAU OF RECLAMATION
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HYDRAULIC LABORATORY REPOO.T NO. 159 Li SUBJECT, HYDRAULIC MODEL STUDIES FOR THE GLORY-HOLE SPILLWAYS AT
LJ OWYHEE DAM - OWYHEE PROJECT, OREGON-IDAHO
LJ GIBSON D.A.M - SUN RIVERAND PROJECT, MONTANA
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L.J By F. C. LOWE, ASSISTANT ENGINEER
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Under Direction of J. E. WARNOCK, SENIOR ENGINEER a.nd R. F. BLANKS, SENIOR ENGINEER
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,-, Denver, Colorado, Nov. 15, 1944
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F O R E W O R D u Studies on the model of the glory-hole spillway for
LJ Owyhee Dam were made by the Bureau of Reclamation person-· nel under the direction of E. Lane, Hydraulic Research r, w. Engineer, in the hydraulic laboratory on the campus of the Colorado State College of Agriculture and Mechanic Arts, at Fort Collins, Colorado.
Model tests in connection with spillway alterations at Gibson Dam were irade by T. G. 0Wen 1 Assistant Engineer, uLJ under the direction of J. E. Warnock, Senior Engineer, at the Bureau of Reol8lllation hydraulic laboratory, now aban LJ doned, which we.a located in the basement of the Old Customhouse at 16th and Arapahoe Streets, in Denver, Colo u rado.
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LJ r,,-, •. CONTENTS LJ Foreword
Section No. Page No. w 1. Introduc tion ...... OWYHEE...... DAM ...... 1 LJ 2. The floating-ring gate and glory-hole spillway at Owyhee Dam •••••• , • • • • • • • • • • • • • • • • • • • , • • , , •• 3. The Owyhee Dam spillway model •••••••••••••••••• 4. Summary of tests on Owyhee spillway •••••••••••• 1 6. ·s\.lmmary of results on Owyhee spillway •••••••••• 4 u 6. The prototype spilt way at Owyhee Dam ••••••• , • , , 13B 9 GIBSON DAM LJ . 7. The spillway alterations at Gibson Dam •• , , , ••• ,. 16 a. The Gibson Dam model spillway •••••••••••••••••• 16 9. The original design of the Gibson Dam spillway- gate structure .....•... , ...•...... , , ...... 19 10. Pres au res on crest •.•••..•...••...... •.. , . 23 11. Cause of surging at maximum disc harge •••••• , •• , 23 u, 12. Air 1 n the shaft •. , •.. , .•• , , .... , ...... •.. 24 13. The final design of Gibson Dam spillway with radial gates faced downstream ,.,,.,, •• ,, •••••• 25 u REFERENCES TO OTHER GLORY-HOLE SPILLWAYS
14. The Davis Bridge Dam spillway •••••••••••••••••• 2,7 15. Model experiments by British Engineers ••••••••• 27 16. Bibliography of additional literature ...... 35
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LJ UNITED STATES DEPARTMENT OF THE INTERIOR LJ BUREAU OF RECLAMATION
Branch of Design and Construction Laboratory Report No. 159 LJ Engineering and Geological Control Hydraulic Laboratory and Research Division Compiled by, F, C, Lowe Denver, Colorado Reviewed bys J.E. Warnock and u November 15, 1944 J. N. Bradley Subjects Hydraulic model studies for the glory-h ole spillways at Owyhee Dam - Owyhee project, Oregon-Idaho, and Gibson Dam - Sun River LJ project, Montana.
L_J 1, Introduction, A series of tests on a model of the glory-hole
r7 spillway at Owyhee Dam were made in 1930-31. In 1936, model studies were LJ made in connection with alterations t o the gl ory-hole spillway at Gibson Dam, As no formal reports on these studies have been prepared, ,--, the purpose of this memorandum is to describe these studies and the re sults obtained, and to present a review and bibliography of available :7 literature upon the subject. L1
,---, OWYHEE DAM
LI 2, The floating-ring gate and glory-hole spillway at Owyhee Dam.
,---, The Owyhee Dam (figure 1) is located in the Owyhee River 21 miles south
LJ west of Nyssa, Oregon. The spillway is a vertical shaft, 309 feet deep, connecting with the former diversion tunnel at a point 240 feet down stream from the tunnel inlet (figure 2). This vertical shaft is bell LJ mouthed, or trumpet-shaped, at the entrance, having a circular crest 60 feet in diameter at elev. 2658.0 flaring inward, to a diameter of 30.75 LJ feet at elev, 2633,0 and to a diameter of 22.6 feet below elev, 2513,0. To control the flow into this shaft a 60-foot diameter ring gate, 12 LJ feet high, was installed in the crest. The ring gate is a hollow annu lar drum, seated wi.thin an hydraulic chamber located in the crest , The
LJ ring gate is thus a floating type of' crest similar in operation to a drum gate, such as is used at Shasta Dam, but designed for flow into a
LJ vertical, circular, spillway shaft.
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LJ FIGURE. r1 .. -······ Top of Dam El. ?675.0 .... -Normal Water Surface El 2670.0·: . .. -= = - . · . r7 -L - ( <·-- : f:if Axis of Dam-. ..; 1' t ,, . -3 · ..,' ," .merqencC" y Gates , ' : : :��---{ - j El 2600· El 2600: 0:; -· · •feed!� '.'a!ve .. : : · r7 • �f: .. Trash Rack.. .--3- 48 Balanced , , ; -.. •::·r:. ,,. ..·.ir.·.-.-.- . �:, · : Needle Valves ·;. El . 2'70�- i.. , -··-- l, :::: :, Sluice Gate � r1 �1....,,.1:ItJ(• .._. ... � Trash Rack··. ; El.2370··, 1· .u c.___; PENSTOCK SECTION :i[)t:.·.::·.�::.:_:_._;:�
•·:.:·,1''!1':::.· ....--' r7 =� · •'rfTj-.�,T,�· �,T1�,�\ -1_ NEEDLE VALVE SECTION !J? SLUICE GATE SECTION r1 ·.,:: l.2150!: };� E_ 60 ', 12' Spi!lwoy Rinq Gafe . Perrnanen f Crest El. 2658.- . N WS. El 2670 · r1 r MAXIMUM SECTION
_j FAULT PLA/1/E:
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...... ,,iil].i.E/. 2675.0 P-- N.W.S. El 2670.�-� >.: C \ r;,.. >- 1 r ·---R•500 -;J� :,,;,,J.� ·=·-·· f.<.';.··.······,---···-·· '<:i·\1 '. --a; .. " 7 � ... L;,.., .... -.... ------�-iTTf,"·f,j,�.:-�--=:=:-L,,.. .. 1.rt.,.-, -� --· C C .; _J -� AND SPILLWAV TUNNEL CREST OF DAM �--��-·� - i�� .,. _.,,,. _,,...· . .. :-;s PLAN
·· Top of Para�!_ El. 26!8.67·· SECTION A-A SECTION B-B SECT(ION C-C � J.....
,:.··Penstock Trash Rack _ _ _ _ 2700 0
2600 5. ... Oriqinal Rock Surface z -LOCATION MAP 0 Sluice Gate Trash Rack DEPMffMENT OF THE INTERIOR ·. ,·Spillway Tunnel BUREAU OF RECLAMATION �.J. > \\ UJ OWYHEE PROJECT- OREGON·JOAH.Q. �.t . ··: �_,;;: ...J 0 LLJ ,, ,•rs"-r:.. -·· t. '!'I'"/'�,. ,, \ . '2400 ! _L... I � OAM AND SPILLWAY LAYOUT ':;-Fault Plane V I I 1 I I I I I I I I n\ " _,.,,,,,.' h ::: DRAWN .f?-."!�
> r r7 I, I ·.lve. ------.� T l�' I? >- M,n. at Rock, I 6 O' .ii- °' Poinfs 21:'' z, ..
SECTION B- B
•: 50 100 · 150 --, :,"1.-_j_' -·· . · Scale of Feet M-:i r7 RING G Normal -.A• ATE_�·r___ _ l_ WSEI. ZG?0.0, ______·----, - ____ -·-··--1. LJ - -·· -- . -�-----";------...•··-·-·: : t'Crest -·- -El···---- 2658.0 ··- .. ---· -- - -- : : - u.J'2450 , 11-t - ri:, /3[ ------�; ·+r·1· f r7 C RDINATES i-·7, Or01noqe Gallery_ �. . - t L-L 5 10 IS 'l.0 '25 10 20 30 4C' DISCHARGE IN THOUSANDS OF SECOND_ FEET DISCHARGE IN THOUSl!.NOS OF SECOND H.E.T -.(. CAPACITY CURVE-D1\IERSION TUNNEL CAPACITY CURVE-$PILLWAY ,0 G_ Trans1t1on r,,Y _;;d ·,' -� - .L- a � 1)_--EI 2513 ri i; I .if' �" rs s, : 11 1.= rs 1 l J :·,:: ::�-- --·DrainHoles IRl5'C GroutHoles0!5'C - .·.)::- Br 7-B ·, 'i' I SECTION C-C ·- IL --22.6'0,arr; '" NOTE LJ ,r : The Government reserves :lhe riqh/- fo chanqe fhe Tunnel 5ecfion from a 22' liorseshoe a 22.6' Secf,on 1s sfarfecl. 1 C,rcular Shaft before Consfrucfion , 1,.f /: :E -l -24103 to C,rcular L .. ; DEPARTMENT 01" THE INTERIOR 1\ BUREAU OF RECLAMATION .75·· � c,.. C � OWYHEE PROJECT.- OREGON-IQAHO I -- I . . , r> < - , . ·\ ,.) . . I . I� __:..:t-.� J·\�l-�l r . "' - _ _- . _:�-- . ��J../>,./0,1I ./ I , -·- ..... ���� ·� I /\ / \.t�/2,,/� I · ' � �L:l..J.�r.�� ! . r--: OWYHEE DAM ! I 22.6' C,r·cu/or l'-,, 22.6' Circular L). Ei.ZJso Tunnel CT _ _ Tunnel' RING · ' - '\ · - · -,· .'·- GATE SP!LLWA L��?U7: h. -� ·,-, i.fsh,' ,--.I·"<-r�- . - -,------:c=J!-::f{_?.J.!,_9:.--- -,_ -� -- . - -- -.,.-,-- - ·--- :,z--:.:=::. . -,-:..:....:.;_._-,--,-. -.-,-,...: . .c.. . . . - .. ..------·. ·.---.. . - -- .. �- --.-- · - - - ·r ···-J_ --_____,,_:.,.---.,.. · -r;-,rv- .,.,/11. '·' ,7Y?,r,t ' -----. ------.-,-·-- ______, ______�I � -� I =-TJJ 1-f )� _ - · � In 1928, when des ir,ns for the Owyhee Da.m were under way, the re were 1--e..J few installations of verti cal shaft or glory -hole spillways , and, aside ,--, from studies by Ford Kurtz in connection with the design of the shaft LJ spillway at Davi s Bridge Dam , the re was little information available which wou ld a.ssi st in the design of the Owyhe e Darn spi llwa.y . The ring ·U gate had no precedent whatsoever . Therefore, hydrau lic model studies were made in connection with the design of the glory-hole spillway at L.J Owyhee Dam to check pre ssures, di scharges, and to ascertain, in so far as possible, that no adverse events would occur in the operation of the prototyp e. LJ 3. The Owyhee Dam spillway model. A 1148 scale mo del was bui lt r-i. u which inc luded the topography surrounding the spillway, the spillway and ring-gate control, and the dis charge tunnel below the spillway (figures ,1 3, 4, and 5). The topography was made from 3/4-inch layers of treated lumber, as shown on figure 4. The spillway inlet between elevations 2600 and 2658 was made of laminated wood - 3/4-inch segments of white LI pine cut radially, treated with clear lacquer, and assembled so that th e segmental joints overlapped alternately. After ass embly the inlet was L, machined to size, with a slot at the crest to accommod ate the ri ng gate . The ring gate oonsisted of a crest of cast type metal and a galvanized LJ iron cylinder or ring attached to the crest at the outer circumferenc e of the gate proper . Two crest designs were studied. The ori ginal de sign of the crest was symme-tri cal, with overhanging lips at both the up ,- L.J . stream and the downstream edges . In the fina l des ign the lip at the up strewn edge was removed so tha t the crest was tlush with the outer cir u aumference of the cylinder . This gate, which fits snugly in the slot on the orest of the spillway inlet, was operated manually . Three push rod s, LJ equally spaced , were fastened to the bottom of the cylinders and pro truded below the floor of the model. The gate was po siti oned from below LJ by raising or lowering the se push rod s and fastening them in place wi th adjusting screws. Forty-eight 1/16-inoh ho le s equally spaced around the oircumferenc e of the lower crest served as air vents to aerate the crest LJ 4 FIGU.R E 3 ,7 ,--7 y ,--L/x4' ,,-- 2"x4' --2 'x4' Tank wall �� / - �·' · . ------. -- -. r7 . 1 ...... ___ -. ;, � ·ri/ <$ ' j) ) ;- r1 2'x 4 !/ '--- j I to I (7 ', ,-----, ',,, Level at , - ,\ ,·-- / -- ,,, \ �- P.5 "6 17 \ ..... _, u '(P. 6 \ : \ I _..,.....___\-' .,\.-Rinq qafe model, seei {),J.f:;. n �--', \ 4.8-D-279 for details. : 1 Joint ! /5 1--- -;; _____ ,;, '' J·\·P. d '--� earonce -� ti'�- ,' ------t' z r l Flo or Elev. 4"x 4'--, 2600 ' 7 L . ..J ,7 � L__ _j NOTE: Lefter P. denotes piezomefers- 0. D. copper fubin q. Contours made out of f white ,i'pine. Alf joints in contours ff/fed with oakum Alf piezometers were connected to qlass qaqe tubes LJ by rubber tubinq. L) - 7 LJ PLAN MODEL LAYOUT DEPA RTMENT OF TH E: INTE:R/QR 0 2 BURl!:A U OF" RECLAMATION OWYHE:E: PROJE:CT - ORE::.-/DAHO LJ Model Scale in Fe et OWYHEE DAM 0 10 1.0 30 40 50 60 10 80 90 100 PLAN Or SPILLWAY MODEL LJ Prololype Scale in Feet DRAWN: F J_. T_ SUBMITTED: . .•. TRACED:. C. t:;.M. ..RE:COMME:NDE:D: CHECKED' . _R_. R, R, .. . APPROV ED: . 01!:NVE:R, coLo. Sl!:PT 17, ,.., Model Ratio 1 : 48 1 4a--�o-z1a·- uLJ FIGURE.Lt Elev. 2678 ']__ """" r r1 7' - -- r-, Stereotype metal cast rinr; � ·· -- - n{'Dia. qate crest- tiqhf fi t info ·-··· - -·f62'Dia. J : - ,.: � · · ·· · 16 :- l thick rinq qate cylinder.------· ·/6f Dia. ... -- -·- -�-)��� . I l 1 1 l "I l I l 1 .l 48 -Air vents ,f Dia. '":" at inlet, to f af A------f :.::r (2- , Dia. piezomefers r l EI. 2645-,i 1 2i,.?"i,-'R·,.__,,.!. • I - J _ I ., , .. I � _ _,,:: '� ::i !..::1 i: .._. ·=/=.·: = = = -=-__- -_- -- t!I I ,� f 0'I,/c:-�" � I I , ,- -1 -'ll I I .. I '° ' I I J .. �--?'··"7E' • ' JI · t• • /• .s_• 5 · ··· · ·>t< · · ··3 - - -�{, ,� - --· 3 --··,..z :--l,0 >: n,- - · - · · · · · · - I Sil,"'4-- - · · - · · · · · r,· · · · · · · · · · ..: � PIER PLAN · ,.,r ·1 �- 't Crest = . u---I--fnside fonk waif � J :rs:�-.:,------tX 2�-- �-,,- ---4 ·s r i FLOW 8 1 clearance r, lf clearor.;ce for l Top artank floor. : rubber qaskefs t===,..li�-t-ti:l!:=--...... ,,:-::ie�r."9 ORIGINAL DESIGN -�')'S;,j-,.. --�-r-��- and while lead. -_ ------Collar supportmq qlory �:OF CRE:.ST;;i;:,,:i;;,,_ �· · · I: I I -;- · hole shafl transition r7 : Ga/vamzeId t· m No. z4 , : ·_/ _, ,, , � 1 ' butt joirt soldered: _/:tf Lj . , :-i"iron screwsm j, IJ : 1 1 anqle Dia. hole 16- 16 0. 0. copper : _ .. I 1 TI 6153.' ,a· . :.f !S '_Dia. . - ..- ....- ....,J fubinq piezometers------.-;:-.'.__ 1-cal/ar with thru model Cast stereotype metal---, - . ------..,.; I :7 ·- set screw D and floor I3,fDia. i to main --·3-fx 20{ qafe :.. p:ezomelers ,_ ..J 2sf Dia. air re ed. push rods. I :· Push rod -,.., - -- -_g) · :7 - - · 13{Dia. -cv Galvanized �:t t- 1 c:,'. . NOTS : · IS{Dia. 0- SECTION THRU CENTER LINE PIER AND GLORY HOLE iron cylinder--/ -,� (:,Ii! � Each seqmenf was qiven three coats ------of clear lacquer, and each joint . ¥------Push rod set s¢rew holes------welf filled with lacquer. � :7 �- --�. ���� w .- · · - t6{Dia. · ": 10 equal seqmenfs on each layer, with alternate joints ,. RING GATE AND CREST ASSEMBLY e ------1-L �· Counfersun -+ ! ; ' !�- � 0 1 48 air v�� ::::�j.;;�_ - - --"---��----�-���- - .. l l .::t 'f 'tT down t o, l'x .i' qroove -. ______'¢� \ ... --·· ____ .t -:.-' _- .. rn �J .,0 l' 168 outside D10. : ' Mo . . -�- s - - e-i' ·- t cylinder rinq qate-�- �� · Y "'\� " MATERIAL del Scale 'in Feet ;;�. 7 ews ---, -•,,._- "s /\ / -" e I No. flat head s cr - e Contours -----···· -White pin 0 10 stov bolf----·- ' · 5 15 10 -··-c/ ft Spillway model- ----White pine 10 25 30 35 L .A.PPROV£D: DENVER, COLO. SEPT. 18, J9J J 46 -D-1..79 �J ._J Figure 5 A. SPILLWAY CREsr WITHOUT RING GATE B. MODEL COMPLEl'E WITH TOPOClRAP!lY, PIER AND RING GATE IN PLAOB:, C_•. GATE .AT ELEV, 26�8,0· D. GATE AT ELEV, · 2667 .O PONDELEV. 2670,0 POND ELEV. 2679.,0 DISCHARGE = 31,100 C,F,S, DISCHARGE = 32,500 C.F.S, THE 1: 48 HYlRAULIC MODEL OF THE OWYHEE DAM SPILLWAY LJ when the gate was raised. The vertical shaft of the spi l lway below the inle t sec tion was made of 24-gage galvanized iron, formed as the frustrum ,---,, of a cone for the transition seotion and as a cylinder for the circular , ___j shaft. The tunnel pr oper and the 90-degree elbow connecting the shaft to . -, the tunnel were made of transparent pyralin tubing • , __j To measure pre ssures in the model, 14 pie zometere were placed in t."'1 e � topography at various point s. Four piezometers we re also placed on the out side walls of the spil lway and twelve inside the spillway - four at elev. 2660.5, four at elev. 2638.5, and four at elev . 2626.5 (figures 3 .o, I I and 4). Two piez ometers were located on the pier at elev. 2668 the normal crest elevati on with the ring gate seated. Pressure measurements were made on a manomete r board, and the head or water su rface was meas L_J ured with a hook gage. Discharge was measured over a calibrated weir wh ich was pa rt of the pe nnarnmt equipment of the Fort Collins laboratory. (_j 4. Summary of tests on Owyhee sp illway. Thirteen tests were made on the model. In tests l to 6, inolusivE!,, the original design was stud ied . In test 7 the ups tream lip of the ore st _and the access pie� were removed . Tests 8 to 12, inclusive, were studies of the final design; and test 13 l.__ _J was made by removing all topog raphy to study the flow into the entrance with a perfectly symmetric al approach. The procedure for ea ch test was LJ similar . The gate was set at a definite elevati-on, and four or fivi runs wer e then made by varying the head and the discharge . Tests 8, 9, and 10 were run twice, once with th e air vents closed and onoe with them operi. In ea.ch te st one runwa s made at maximum capacity when the inlet was. sub merged, that is, with the vertical shaft flowing full of water. The other LJ runs were made with the spillway in normal operation - the water fallin g over the circular weir into the shaft without filling the shaft. In ea.oh LJ run the discharge, the water su rface elevations, and the piezometric i'"1' pressures were measured ; the flow into the ou tlet was studied, and photo LJ graphs were taken . An analysis of the results included the conversion of pressure and L_j dischar ge measurements to prototype by the laws of hydraulic similitude 8 LJ LJ ,_j c_J -----. . zometers 1 to 18, inclusive, and 31 and 32. The se piezometers are located L,__j upstre�� from the contr ol at the crest, in regi ons of low velocity1 con sequently, in every instance pressures were equal or nearly equal to the ·l.._.J head above the crest. Originally they were located to determine differ ent velocities of' approach due to the configuration of the topography , but 1_J the resultinr; difference in head was too sma ll to me asure accurately. Pressures in the spillway inlet, piezometers 19 to 30, inclusive , were general ly slightly negative1 but no ne gative pressures were recorded which L.J would indicate the pr esence of cavitation in the prototype. In gen eral, pre ssures for the ori ginal and the final de signs were the same , indioating [_J that there was little basic diffe renc e in the two designs. The final crest design, tests 8 to 12, inclusive, was made by remov ;___J ing the lip at the upstream edge of the crest of the original de sign, tests 1 to 6, inclusive , and by opening the air vent s under the lower nappe of _ __j the overfall. The removal of the lip at the upstream edge of the crest was to simplify construction in the prototype . L__j A comp ari son of pressures for te sts l to 6, inclusive, wi th those for tests 8, 9, and 10 indicated that remova l of the lip had no appreciable L._J . effect upon the performance of the spillway. A comparison of tests 8. 9, and 10 with tests 8A, 9A, and lOA revealed that the action of the air vent s had little effect upon the spillway performa nc e. In the model the she et of water flowing ove r the spillway wa s usually not symme trical, with fins and troughs ne ar the pierJ so it wa.s possible to provi de aerati on to the lowe r nappe of the overfall wi thout vents. Such a condition may not occur in the prototype . The re the flow wou ld be mu ch smoothe r, and with a Li jet several feet thick it wou ld be difficu lt to provide aeration withou t vents. In test 6 . run 2, such a cond ition actually occurredJ the und er LJ nappe failed to aerate, producing undesirable flow conditions. The refore, air vent s were included in the final design. L-1 As may be seen by the rating curves ( figure 6), the flow over the spillway increased with head unti l a discharge of about 40,000 second-feet l_J wa s reached under a 14-foot head. The vertical shaft of the spillway then 10 LJ L. j :-, 'l'ABLI l \._j S111111ARY 0 F VOD!L TSST S 0 N OWTRl'I DAII SPILLW A Y J__j D;.TA IR PROTOTYPE lfoad .1 G•ta ProHUNa la sptll.., ctnaoe Rua onet n .. Pi•aomteN at a. 2650-'i Plaa-tera at u. P:leaomtan at 11. 2626.,lii q .....5 -.u .... .-u1- lloo .1... lloft. .... -n. 1' 211 Ill 22 25 24 25 29 LJ .,, l l 2d,i8.0 5.82 ,.a, • DJ. • 0.1 • -2 • + 1. _, 10.2110 • o.6 0.5 1.7 • 2.1 - 2., •0.9 + 1.0 3 + 0.6 Ill all teale '11• wrU•l a.ta 2 .18 21,000 • . - - + 9 3.99 1.7 • 0.1 l.B • 1.9 5 1 - 3.7 • 5.0 • 5 .6 • o.a + ...L6 1.0 + o.a att nu. ud ,u tRl.el 11.12 J0,500 - ,.2 - 2.B • 5.5 • 7.2 - 2.B - 5- 5 • 1.7 • 1.0 + J.9 + loll + 7.B r""\ 1 • o.a nbarpe at dlaoldl.rpe 5-JJ loD,100 • l.B + 6.9 + L7 • 3.7 -12.5 -1.a -10.a -a.i. • 5.0 - e.1 - l&.7 peeler lbQ co,ooo l5A .....20.10 lal,500 DI.•- +11.2 +11.J. +11.7 • 9,J. - 6.J - J,3 -1&.5 • 1.1 - l.B - L J ...., -�,�ti2Ji4 "-" =� •GDDll-hel • \_j 2 ...l 26(,0.0 5-81 10.000 5.19 + 1., + l.J + 1.1 • 1.i. • 2,5 • 2 .1 - 2.0 - L2... • ...,1.0 • ll.6 + 1., + l,J Oata 2 20,000 .,_IO + 1,5 + 1.9 + 1.2 + 1.i. -1&.5 - l&.8 • 5,1 • 6.5 + o.a. + o.a rataed u.,a 30,ooo 4.15 + o.a + ,.2 + 0.9 • 0.1 -5-"• 7.9 - 1&.5 • 7.0 - 1., • o.J + + 0,6 2_...-, 11&.36 lio,100 + 4.B +10.6 + 4.1, • 8,7 -10.i. • 7.9 - a.a -1&.6 - a.1 -t-4 6 - 7.6 -, l5 17.65 lol,500 J.00 +12.2 +11&.6 +12.5 • 51,6 • 608 - 3.9 - - - 2.8 - 1.6 • 1.9 -2 ,.78 1&.9 6.J ...., THU l lo ia 1Acl. Orlcl.aal. CHlca 3 l 2662.o 5-0b 10,,00 4.112 + 2.3 + 5.B + 2.5 • 2,1 • 2.7 • 2.1 - 2.2 - 2.i. • o.a + 1.7 + 1.i. + 1.0 a. .. 2 8.Jl 20,100 4.31 + J.9 + l&.J +l&.6 + J - 5-4 - ti.6 - 4.6 • 5.3 • 0.2 + 2-4 + 0,9 + 0.5 LJ n.iaod .4 •• Lip oa apaveu Np ot 11.00 29,900 l&.36 - 0.1 + a.o +Ll -2 • 7.2 - 1&.8 - 6.0 • 0.7 + 2.5 + 0.3 + 2.9 ar!'al · · 4 11&.'9 loD,100 ,.�l + 5-1 +lJ.J + 6.5 +10� -10,3 - 6.5 - 5.6 - a.6 - 5.7 - 6,1 - J,J b. Pter 1D poal\tan.. 4 'l l!ollko 5.31 10,200 ,.� + 5- 3 + 6.2 + 5 .5 • 5,2 • 2.6 - Ll - 1.9 - 2.2 • 0.9 + 1,9 + 1.5 + o.a e. to•r aappa at offrtaU a.ta 2 a.21, 1',900 4-37 + 5.8 + 9,5 + c,,,9 + 5 .2 • 5.3 • l&.9 - 4.7 - 0.5 • 2,2 + 1.0 �tl+ O.J 1101 aeraled - na\a rahed -· - 5.2 6,16 19,800 4.1,6 - 0.9 - o.6 - o.9 - o.9 • 1.9 - 4.3 • 1.7 - 1.2 - 1.0 • 2.3 -0.5 - 0.9 p1_.i. 6 roe, 4 10.92 29,600 4.J6 + 0,5 - o.i. • 0.9 - J,2 - 6,8 -5-J - 6.1 - 6.7 - O.l • :,.o ... o., + 0.6 5 13.u '9,100 4.-JB + 1.9 +llo.O + 5.5 ,12.7 9.J. - 6.1 • 7.6 - 6.2 - 2.J • l&.9 ' - -4.2 -a.a i.-5 , l 2666.0 5.25 10.200 l&.50 - 0.2 - 0.2 - 0.2 - 2.6 • 2.1 -· 6ll.B - 11, J + 0.7 + 1.5 + 0,6 0.ta 2 5,65 10.,l,oo 4.11 -• a.a0.5 - 0.2 - o.6 - 1.0 - ,.a - J.l • 2.7 - J,l - o.i. • 0.5 - 0,2 "b•d a.{6 20,000 l&.17 - ,.1 • 1,9 • 2.5 • 2.6 - 4.0 - 4.6 • 1.7 - 1.a • 11,8 •O - 2.2 w 8�� 4 11.15 J0,000 Ii.al - 3.0 • 2.7 � LB - L6 - 4.1 - J.7 • 2.7 -2 - 2.6 • L6 -2t - a.a 6 l 26(,B,o 5.70 10.,l,oo 4.05 + 0.1 -t 0.1 + + 0.1 • 0,1 • 0.1 • 0.1 - o • ;_j 0.1 • 0.1 .0,2 .i. • 0.1 0.1 a.ta 2 8.$ 20,000 4.18 + 1.5 + 0.7 • 0.2 -1&.6 • l&.7 - 4.2 • Q,2 • 2., + 0.9 + 0.1 rahed a.66· 20,100 4.20 • 0,9 • 1.1 • 1.0 • l.l - 1.2 • ls.1 • 1.1 - 1.0 - i.i. - a.6 -1.5 • 1.1 ST 10 he\ l 7.32 15,100 4.05 - o.6 - 0,2 + o.o • 0.1 .• o.i. - o .a - 0,2 • 0 ,3 - o.a !tl+ 0.1 • 0,7 - o., 1 l' 2(>!ill.o 5.15 i...200 J,97 • 0.1 • 0.5 • 0.1 • o.i. - 0.9 • 1.2 • 1.1 • o.a • 0.1 • 0.1 • 0.1 0 Oata 2 6.11 11,&io l&.06 • o.i. � 0.3 - o.i. • 0.1 • 2.7 - ,.o • 2.9 •- 2�,9 • 0.1 + 1.0 - o.6 - 1.0 9.00 20,800 li.07 • 0.9 - o.6 • 1.1 • 1.7 - 5,J - 4.6 - 5 - 5 • 0.5 • 1.e • 1.0 - 0.6 ft ,J. LJ u.a5 Jl,700 4.12 - o.a • 0.5 • 2.2 • 2.6 - 1.a - 4.8 - 6.6 - t2 - o.6 + a.a • 0.5 • 6.6 l5 17-58 lal,ooo L95 + 9.B +11&.2- +10.2 + a.1 -1&.6 - 2.8 - 3.9 - 1&.7 - L5 - o., • O.J - 0 ,2 - la Hal fl, NII i, lbe Wldff 8 l w.;a.o 2.87 3,600 3,91 • 0.1 • 0.5 • 0.1 - 0.5 • 0.9 - 1.3 - 1.0 • 0.7 - o., - 0.3 - 0.3 • 0,1 u.ppe ftlled la Hn.h. r�1 Oatlo 2 6.01 11.000 J.96 + 0.7 - 0.2 - 0,2 - a., - 2.i. • 2.2 • 2.5 • 2.5 - 0.5 • 1.0 - 0.5 - 0.2 la oU.r nu Ibo uader 8,99 20,200 J.96 • 0.7 • Ool - 1,6 • 1 .7 - 4.7 - 4.o • 5.0 - o.i. • 1.5 • 1.0 • 0 .7 Dappe ...... u .. en.194 • 4 12.02 4.11 - o.6 + 1 .6 - 2.0 • 7.1 • o.i. • 300 - 6.9 • ,.a O,J • lo.la ...... 5 15-87 �-,100 • 7,4 +U.2 + 7.5 + I.a - 6.0 • 3 - 5-0 • 1.0 - 4.7 • 2.5 - ' ,.i.i. -lo.la=� - la.a a,. l 2{68.0 2.87 3,600 3.� • o.i. - o., - 2.9 • 0.1 • 2.1 ·• 0.' 7 - o.6 • 0.5 • 0,9 +o,4 + 0.7 - 1,3 a. .. 2 5,96 11,JOO 4.12 + o., • 0.1 - 2.9 • 0,1 • 2.7 • 2.1t •LO - 1.t -1.0 + lJ + 1.4 - 1,5 8.89 20,(,oo 4.12 • 1.3 • 1.0 • o.6 - 1.3 • 5.0 - 3.B - la.a • 1.1 + 1.7 • 0.6 - l.B + - 4.2 - • la \HI 7, lbe pier •• re- t ll,o6 Jl,100 4.IJ • 2 .9 0.6 - 2-4 - 3.0 • 7.5 ,.1 - 6.1 i..1 - 1.5 1.7 + 1,0 - 1.J mncl, ud Up oa upatnaa ... 41,100 J.85 + ,.1 + 7.a + 3.1 + 5.1 • 7,5 • 3.2 - 5-9 -1&.o - 6.J - 0.1 - 3.5 - J.7 s 11&.7' odp at areal out; ott, -,., lPer 111ppe onrtall LJ ot - IIOI HNW. (Air Wall 9 l 2661.0 Lil!I J,900 li.07 • 0 .5 - 0,3 - o.a • 0.7 -o.a - l.J - 0.7 - o .6 • 0,2 + 1.1 + 0.1 • O.J olaood. l O..tlo 2 6.07 U,(,oo lo.Ila - 1.2 • 1.1 - 1.2 • 1.1 - i..a -L9 • 2,7 • 1+6 - 0.1 + 1.1 - 0.5 rau+d 9.01 21,(,oo - L5 •10.J •Ll - L6 - 5.0 • O - o.i. -1&.6 - o., • 1.a • 1.1 - 1 ...... U,90 '2,900 - ,.1 + 9.1 + l.B -1&.1 - 6.8 - t9 • 7.1 - li.5 - 1,3 + 2.7 + 0.5 t5 15.20 lal, � +14.6 +11.1 - • 1,7 -i.. - 300 +12.6 +lJ.2 3.B 1 L5 -1.9 • 0.2 • 2+7 6 18.l,4 lal,800 2.IIO +17.B +18.0 +11., +lJ,1 - 1.0 + 0.5 - o.a - 1,0 + l.J + 2.7 + 0.5 +-o.i 0.1 c_J ,_ 9A l 2661.o ,.u li,200 Ii.IO - o.i. - o.6 - 0,7 -0.1 • I.O - 5.6 .4.9 • o.i • 0,1 + 1+5 + 0.5 - o.i. a.ta 6.08 11,700 ,.79 - o. • 1.0 - 1.0 • 1. - 2.i. - - 0 • 1. • 0.1,., - o h•u a 1a lZ lllol. 2 l&.IJ J 5 1.9 ,8 - o.a 7 .a Plllol l:eolp raia+d 9.00 21.,l,oo l&.20 • 1.7 + 1.1 - 2.2 - l • 2.0 - 4.2 - l.B - i.i. - 1.B + 2.1 • 1.5 • 1.6 I& 11.87 '2,600 l&.Z! - 3.6 +10., - 3.7 - ,.2 - 3,J. - 3.7 -1&.5 - ,.2 - ,.1 • J,7 • 2.6 - J,4 5 IS.S, lal,l,llo +12.1 +11&.J +1,.0 +11.B - 2.6 + 0.1 • 1.6 - o .6 • LO • o.6 - 1,.,.i. • 1.6 6 17,111 +16.a +lJ,O • 0 • l.B + 0 a. �al u ation la,700 L95 +17.2 +16.1 ,3 ,8 + 1.0 +1.2 + J,2 +- 1.6 + 1,3 b. Pier nplaoed. , 10 l 266,.o 2.1} ,600 • - • - 0 - a. la '8•1• e. ,. aad 10 3 4.22 - 2.0 - L5 - 1.3 2.0 • 1.6 • 1.0 1., 1.0 .2 1., - 1.i. - 1., air wall olooed. Ia a.ta 2 6,,lJ 12,200 4.21,,.10 • 2.0 • 2.5 • 1.3 • LO - 2.0 -a.1 • 2.0 • 1.6 - o.i. • o.J - 2.0 •. 1.3 32 IHI• 8A, 9A , lOA , U 9.a, 22,100 4. • 1,6 • 2.7 - 2.2 • 1.5 - 2., • 2.1 - a.a -2.0 • 2.1 + 1.0 - 2,J - 1,5' aDd U, atr wale opea. 6- 4' 12.0, JJ,700 - ,.i. • LO • 3.5 -i..e °:Z - ,.2 - L9 • 3.6 • 5.9 - 3 + 2.1 - 3,J ,.1 .... 4-29 -4 - lOA l 2(,64.,o 12,36 ,i..100 4.21, - J.b - 3.8 - i..o ,. 3,8 • 3.9 + 1-4 - ,.1 - 1.i. fl.OW-•• Ooto '2 8,99 21,600 • 2.6 - o.a - ,.o - Z.5 - 2.0 • 1.7 - o. s - 1.8 - 2.5 n1aN c,.OII 11.aoo 4.18 • 0.7 • 0.9 • 0,9 - o.a - 0.6 • 2 .1 • D,9 - o.6 - 0.5 + 1.1 - 0.1 • 0.5 " 6-• L98 4,000 4.18 - o.6 - o.6 - o.6 - o. s - o.a • o.� - 0.5 • 0,5 • 0.1 • 1,2 • 0 .1 - 0. LIP 4 - ,., - '"" 5 CUT 1/ _ ... OFF•� l 2t47,0 -t 0.7 + o.i. •- '""1.0 - 0.5 - 0.6 - o - 0,2 - Ci • • l - 11 . J,900 J.!111 - o.s .,: .a lJ .B 0.7 Gata 2' 5.99 11, + 0.3 -0.1 - • 0,7 - 0,6 • 0.7 • 0. · • 0. - 300 4.o9 1.1 7 5 • 1.1 o., • 1.0 - 0.7 � ST raia+d 9.00 111,200 l&.17 • o.a • 1.1 • I,6 - 1., • 1.7 - 1.a • 1.7 - 1.a - 2.2 • 1,7 • 2.0 � toet 11.Bl.. '2,500 lo.a, - J.6 -lo.la- ,.s -:tl2.8 • 3.5 -,., • J.I - LJ ;ti - J,9 rt: ]8 '.__) 12 l 2670.0 J. i...200 + 0.7 + o.o - 1.3 - 0.3 - 0.4 - o.i. •5-J - 5,0 - o.: - 0.3 • 0.7 - o.6 a..tio 2 6.14 11,800 + 0.3 - o.6 • 0.5 • o.6 •- o.i. • 0.7 • o.a - 0.6 - 1. • 0.1 • 0.9 -oa raind e.si. a,l,llo 4-2' - 1.2 - 1.7 - J.O • M • 2.1 •- Ll-,.a - 1,8 - LJ - 2,3 12- , .- lJ l 116,t.o 3.111! 3,900 • 0.1 - 0.2 -0.1 • Ool • 1.1 - 0,2 • 0.1 • o � 0,2 • 0.1 • 0.5 - 0.1 2 ,.. ..., �, l 6,27 12,000 • ,.,1.7 • 0.1 • 0.6 + 0.1 - ,.,3.1 • LB • LO -1:l • o.a + 1.0 • 0.1 - 0.1 a.77 20,600 4.19 • 1.6 - o.a + 1.1 - o.a - ,.a - 1&.7 - 5.9 - 1.6 - 1.a + I,1 - o.8 - 1.8 ha, lJ , \apcllll'llpbJ ud pier 4 u.94 700 4.19 - 1., + 1.1 • 0.5 - 2.7 • 7,8 - 6.6 - 6.7 • 5,7 - 2.2 + 1.9 - 1.3 • lo8 l"HOnd , 1111rnea 1o sln ... 5 15.,a �-,500 4.18z:: + 8.9 •L0.2 + a.1 + 5.8 - 4.3 - 2,J -6.1 + 0., •-•rlNl 6 -a.o 19,97 "2,900 2.55 +lJ,8 +15.a +11&.o +12.- J + 0.1 - Ll + 1.0 + o.a - 2.8 + 5,6 • 3 + sJo ' - -�1 Hou r-, . -- llota, (l) ..., - n. -m.am or diaobuge 1a - - tllo1. .. -1... C Z:� C• ri1]I" ·- LJ ( Q • dbobarg•, I• bNd abow onat aa4 J. • olroatenaoe ot 60-toot. 41-ter on1t .(Ja.5 feet,) ._o11.-,. LJ -.. •. - LJ r -I . . r 7; 1 .J L l . ·• [_ L L l . [ :J ')j I J C [ [ [ [_ [ J [ J [ [ [ .t '] l J. ' 1-· r J 2680 I .,·a. .I: ,. f I,,"' ' EXPLANATION (f)--- C) I 2678 � 1:) ' o . r Gate seated . ...._ E Gate ro ised 12 ft. x 3 .._ '< 0 J<�-- (fl ---- Ga t e r a i s e d ft. ,--- C) Q. (.'.) � 0 ;!· /J.. Gate ra ised 6f1. 26 76 � z + Gate - 1-- / i.,;,- ' C raised 9ft_ (J) '- }(! �Gate ra 1sed V I z <> Gate ra is ed 12ft. I- y w 9t Q_ LL V ..,.v/4 / ...... When head approximately- C) - 2 6 74 :s: ,,,,.. 0 16 �o· z V / 14 ft. above crest, the Gate ra ise V / _j 0 ,_ � _J ·, Spillway In let ---- 0 / / i �� 0 .,,k, 6 f x i:> 2660 2 .L______··------·- ··-- .. -- .. t- - - ... - �------· - - -�- ·-- ---. -···------i --- -...J. i 2658 0 0 10 20 30 4 0 3. 0 3.5 4.0 4.5 Q D ISCHARGE IN THOUSANDS OF SECOND-Ff;::ET COE FFICIENT OF DISCHARGE C= 3 LH /2 �- C) OWYHEE DAM -GLORY HOLE SPILLWAY C: ::0 RELATION OF DISCHARGE TO WA TER SURFACE ELEVATION FOR VA RIOUS .,,-IT) RING-GATE POSITIONS ANO COEFFICIE NT OF DISCH ARGE OF RING GATE. CJ') �' j LJ filled, and the inlet was submerged and choked. A furthe r in c rease in head increased the di scharge only slightly. This cond ition was reflected in the discharge-coefficient curves. The coefficient remai ned nearly constant to a head of 14 feet but ra pidly decreased with an increase of head . LJ , As the head increased to the point where the shaft fille d, an un stable condi tion was observed. The verti cal shaftwou ld fill , then u empty, followed by a refil ling and a repetiti on of the oycle. This surg ing action would be undesirable in the prototype, but no practical remedy was suggested . However, the spillway would fill in such manner only dur l_j in� a maximum flood, which wou ld be a rare oc currence of short duration; so this surging sho uld have little opportu nity to inflict too severe dam age on the spillway. u The object of tests 7 and 13 was primarily to see whether removal LJ of the pier (test 7) or all of the surrounding topo�raphy (test 13) would change flow cond itions to produc e effects other tha n those observed in t-:lsts 1 to 6 and 8 to 12 , inclusive , especially the formati on of a vortex in th e spillway inlet, A vortex was reoognized as undesirable becau se the dischar ge rating would be re duced, No appreciable differencesfr om the other tests were ob served, and, in test 13 , when attempts were JDade to induce a. vortex, the flow qu ic kly re 'tllrne d to its nonne.l radial pat tern . This did not preclude the possibility of a vortex forming at greater heads than tested; and during an abnormal flood, should a vortex form in th� prototype and resu lt in an app reciable drop of spillway capac ity, the ring gate should be rai sed to a point where the fl ow again be comes radial, for by doing so it will be possible to increase the capacity of the spil lway. 6. The prototype spillwa.y at Owyhee Dam. The ope ration of the pro ,--, totype spillway has been de scribe d in an artic le, "Floating-Ring Gate and L.i Glory-Hole Spillway at Owyhee Dam," by Lewis G. Smith, Assis tant Engineer, Reclamation Era, August 1940, and also in an hydraulic laboratory report, ·�_J HYD-37, "Rep ort on Inspection Trip to Correlate Present Hydraulic Design 13 LJ LJ L.J Practic e and the r) perati. on of Str11ctures in the Field,"' by J. E. Warnock, L-.J SeP.ior En1::ineer. In desc ri'bi::6 the flow over the spillway , Lewi s G. Sm� th quotes the Owyhe e monthl:i,· report dated May 5, 1936, which states I__ / that the ring gate war ked perf'ectl:,' after a few mi nor adjustments to the -'-,. controls. After passing ap proximate ly 55 , 000 acre-feet of wate r with a maximum flow of 9,300 second-feet, inspection of the spillway shaft and L..J diversion tunnel revealed no indicati ons of erosion. The fl ow over th e spillway was described in the Smith report as f'ollows 1 LJ "During flow a.round 1-1/2 feet in dep th ove r the cre s t, the water fal ls in a so lid sheet toward the center of the spillway shaft and apparently entrains ai r faster than it can be released at the outlet end of the spillway tunnel, causing tne air pressure to build up unti l great enough to 're gurgitate ' or break through the sheet of overflowing water . I__ } This air oome s through with enou�h force to c arry spray 50 or 60 feet abo ve the level of the gate crest, as m.ay be seen in ] LJ figure 8 [smith report . This phenomenon occurs some times as often as once every 15 seconds and sometime s only once in 5 minutes, depending upon the tai l-water elevati ons , which are influenoed, also by the water released throu gh needle -valve outlets at the dam. For flow less thanab ove-stated, excess entrained air is apparently ab le to work back unhampered. r-. For flows greater than the 1-1/2 feet over the crest, such as shown in fi gure 9 [ Smith report] , the air pressure is not. suf ficient to break back and is forced out through the outlet b.J end . It i s believed tha.t a suppleme ntal air duct could be readily provided for air escape near the bottom of the shaft, which should prevent this regurgitation." Warnock al so observed the flow into the spillway, and, in additi on, .. h..! he described a conditi on at the exit whi ch wa s not anticipated. ttwith the 1,800 second-foot discharge , the fl ow into the .,-'.� sti lling pool below wa s undisturbed, but as the flow increased r 14 L. : L-- ' L-· - j ____ \ an unexpected disturbance ocourred which, so far as is lmown , ,,_ .I wa s not detected in the model. The stream of water from the spillway tunnel created waves on the surface of the stilling L.J pool. These waves traveled across the canyon, refle cted, and retu rned. As they struckth e o ncoming hith-velocity stream LJ fro� the tunnel an inc ident occurred wh ich, for lack of a better term, is called an 'explosion.' With this par ticular flow (3,000 second-feet) the spray from the explo sion was thrown two -thirds the distance up the adjacent cliff. The caretaker said that with larger di scharges this s pray was thrown to the top of the cliff.It ,--.._ i', . Evidently the air drawn into the spillway entrance wasej ected as a strong LJ wind . This has been observed at other spillways of this time ; but when the reflected waves reach the tunnel portal, they are great enoug,h to seal the exit for a short time and the air is qu ickly compressed to the extent tha.t an explosion results from the release of the air . LJ u u . LJ LJ 1' LJ Lj 15 L. ,_ J LJ L.J . GIBSON DAM 7. The spil lway alterations at Gibson Dam. Gibson Dam , completed l...,J in the fall of 1926, is located on the north fork of the Sun River a bout 60 mi le s west of Great F'a lls, Montana . The spillway wa s of the vertical shaft or glory-hole type, ha.vinr; an eccentric crest 100 feet in diameter at elev. 4711.5 (figure 7) . T his shaft flared inward to a die.meter of ,··-----i 61.6 feet at elev. 4704.2, 36 .0 feet at elev. 4676 .0, and 29 .5 feet be low elev . 4623.75. At· elev. 4623.75 the shaft tu rned through 90 degrees on a 59-foot radius to a circular tunne l 29.5 feet in diameter with the floor at elev . 4550.0. 'f here being no gate s on this spillway to hold the water level above elev. 4711.5, the storage capacity above the crest Li could not be utilized. After several years of operation it became appar ent that the extra storaGe which might be realized by holding the water above elev. 4711.5 would become necessary as the water use in the valley increased; therefore, in 1935 , designs for spil lway alterations were be g:un which involved placing piers and gate s around the sp illway to make possible storage up to elev. 4724.0 (figure 8). ,--, . _- An hydrau lic model was used, in connection with the se alterations , to study the flow into the spillway with the gates in operation and to compare different designs and arr angements of the gates and the piers . 8. The Gibson Dam model spillway. A 1163 .6 scale model was built which inc luded the topography surroundin� the spillway, the proposed piers and the p;a.tes, and the spillway and the di scharge tunnel below (figures 9 and 10) . The topography wa s ma.de of wire lath and plaster. LJ The spillway entrance, between elev. 4712.0 and elev . 4676 .0, was made of concrete, poured with base s on which to set the piers, and with piezome ters in place . The transition section between elev. 4676 .0 and 4623. 75 was mil.de of 1/10-inch pyralin in the form of a frustrum of a. cone tu permit obse rvati on of the Clow in that region. A pyra.lin elbow L.J below this tra.r.csi tion connected the vertical shaft to the di scharg;e tun nel. Ht�vi nc, been used in the previou s Owyh\'Je model, this elbow was not LJ entirel/ to scale in the Gibson model in that the radius of the bend L..J FIGU � ,. > . 7'25 / / :;-f!CAT.IONS No � 0 - ° :i J OJ ,\ \' ..l \ ·· .:, ..-,::; .. '·• " '!l'o · .- -- ,, IJ ' 'j.---- .,.,. � ;/ \J .J' /; 3o', ·t ·,,· j{ 1 ·,:;-,· / " I �-ll'''I -}. /-� 1,. · "'� · Con,ca! 3ur-facP. 1 I " t -ti Ii/' -� ve ,, 1 .-,. - ' ' � l } .· 5 · O \ ' i : . I .:..,. 7 ------_...... _ •1 _,e · ') • ., ..l, �. i q .>- 9"A1m "--�-. J- -:- •; 9...... --,1 - 1 , "'.\.,. ... /;'"; c:< _· . Ji 0 ,· ,:",,: /5 l !_r: ·J r-:<::· " i,: _ , -·. , _ :,- ·,-' -"°, _,---, ·. ,I . '' 1 o , . - . 1/ :\' • - ,. ,>, '.J :;,_ . /. - s - -!;,... : ; j >,_·,.x�·; · ·., ) '•• .-> - . ,. . ----- 8 . ,' I · Conirac+ lion joml I �9, · / · .�. I �---- ' "�i .. ' ' ; · ·. :- �:i ...... 45.1. t flJ . � 1 OnS t 1 -ra ' "':si. ·'E_Cr es 1 (' ., ..{ /; \ '1:" 0 1 -�18 . 8 ,.,' 3 -; ,8 ,;j -�- .11"15 ·-1--� "· ., ?4"x 74Oin·' Monhof /e .'.?' · ,Y . UL_ J ...,, . -- - -- ,_ f _;,�-/ 1 4'.:��',; ', V I ...:i-- -- f,.;( ���,-· , ! , ., : :1i-� o;-f :'2-' "· /,:._' ' -, [XP_I fOn 'oin/ 11,, - .._ ,<)f ·' rc, ._ . ·•>· '--.._l.,·< - - O\ ., I·- - ?'O'' .... ,- ./ . -r , ,- Z? ·J0' . ··Wa ll cfa� . \ �l:,f _,-_ · ,.'.: o (er /; i f. ,, / ' � ':" fi/ .;,.,. :B·a· - 1// i 'kJ , , ,{ I I� - - 8 · .. · -::t;I _·:::.:I _.:�.--_) ..... � 'i'· c rk 0 Confracf,o n J J � o -· .\�• ; \ ...J. I � -:. �- � ' .: i: .... r o' I // 24"x 24" Man hole� :.: .� ·.: : : :,: j \ 1- ·{or Cr,:s.t n / ,1 "f! 1 ..L) ·-.Y-- . ... L. _ • 1{;.- - , , 1 ..;- -- \x .r "'·1 ;Pr" _. - i- :-;' - : .,,·15': .. ,- s·,. --- L l :1' · ·------:....___ -.1 ,. ��• '.;!§'.( , "• . , . , -< -- • " :1� �pa sion JOmls .:, r- : - . _ _, : � . ,' E; . I '_ c,; }' / o;' · · . ' If 11 II. 8 Ta rp ap ar JOtnls i 8 ._ 0 .. 1 .,.: ' I PIER,.,:., ,,/ \ .s... 45' .,,-" I �if'.O" ,, .11, . 6'.0" . "' :·1' P ICAL·l? ·O ,j.c · · B'· O" . ·" / f' SEC TIONA L PLAN PLAN · -<£.Cres t, TYPICAL 4-n- ABUTMENT ?'' •/ d .n ---:-:-:! 0 i �- -- ·· Conlracl ion _ioin t [/ 4738 50·· £.'. ..,. 738 50�-- �> - - - - •.car rai s .\ "·:-�"��- �-- Contrnc!,on JDinf--···- Co1./racfian Joint-- ···· abcut JS ' crs r 8 - f [ xpansicn join ts . I // 4sbestos sheet packinq · II Tarpaper jo int_.- I / \ - ···-Expansion join ls I · · 8"x fd·O' Slee/ ,'a /�s ·· PL AN ,o ,o '?.0 30 40 p Tarpa per join / \.... .:.· Scale of Feet £1 4730-. ?0- - -··---· ·., >- £1 4 7 30. 00 · recess \-_;,· 4'' Sq. air venf-. .. 1--7" r7 �LOW :2 24 "x 24" Te mporar4721. 00-··y _hole·-. .,····'Na ll pla le oo \_ J - .for gate p,n inslal!C11ion ,:·.·.·: Top a( gale El. 4 7 24 P,n fl . Gen era/or house ·.:-�Graul recesses far -:- f; t1- 75B.5C ,i.-- -·· wall plate lugs · /, · _.. .. .::-P 4729.00 or ,· ,' _ .,. · J · -...... ,....,..,,. _ Pier nose _ . ... .- � . ._ . _ · I 1... i . . . , . 7( J . ----. ?;�:-: I recess qafe- -;·:i>� . 47':!t1 00 ' C1·esl U 4112.00 : ') ><,�/'-�-- , , El 4709. 84·: ._,_ 6ro uf for __ �' , w I - ut, '.- 4" Sq. holes--· �: gale sea! -- -- ·,, El. 47 � ", 06.00 ·_:_ :.:s l:lli\ ·· x .dl ,\;,,,n, ,! SECTION A-A .-<·- ' ..., ff_4_7J L.; :, ,, 18- . A•1e C-C of new CDnCre u :5"Min. TYPICAL ABUT····MEN.4" TDrain DE TA inIL porous con e_f : I �:_ �_ i e 'Chip_ lo allow 6' TYPICAL PIER S £CTION v Ji,· -·. ; .· .. -·· ,, m, oo. •, · SEC T ION B-B a ,a 2 "GI : . sld p2 "'·p handrai/· ;;�--. 0/) ·_:--·····2 • r ; : -,.h- L so-· i/:---r:.,_-.- ._ '- "" . J:J0 DE TAILS , i,, . , NO T£ u ···M·n. . ·_,· 1· ; _.- Crest . Otn 5 . !:�------� fca le of Feet r--�------;� l"Hil 12 " e. ,<.O. 1 · 2 �, @ 18" b. f :- -(: .. A < Rein forcement in piers not shown I , - , -->- ·' Cresl , . . - " I . 5 ::J � @36 f.f ., .•I,, ' ,.· .> : .-. Confrac-N!ian J· I . I : / , � r _ 4-;·. � ,.,,,· . r �� · .·, �-- 4-��->� t·· . 12"Ave . ,'0 _..,__._, . i "' DEPARTMENT OF THe INTERIOR !i!: /� :';' /11 l .' :..IN � . ' SURE'.AU L, ·'9'' M1n . " 1e r--- .· Y; o .. � � I OF RECLAMATION 'I � ,.0 � 4130 Afe/al seal .... . I -� L_L . .t. ===-r:::1 . L L .1 L J SUN RIVER PR Ol./ECT-MONTANA ." • I . . - - ft@ 12"8o lh ways ' I" >m r ; 12"Ave. r, p · ,< -� A :· i --Crimp each side � "-1?0 1 Ii · I§ Anchor bars abauf ·, 9"M1n. 1 : · · 2 I �4 : F I- I "' 1-T l l --r,,.v1 ! I N / �8,' 5'crs 4' m,n ,nlo roe A. u -- O ··-20 Gage metal To la! w_:dtn .J ,.. GAGITEBSON DA M ·. 2 · lif Anchor bars af each 0 "' Chip lo allo w m1n1mum or sh e f !3 " > butf.ress. 4" min. in fo roe" � ,... .J.SPIrlC LLWAY ALTE RATI ONS or &" or new concrete 5'·6"Ave. ' .., DRAWN SUBMIT TED ,'?'WY� £-£ ... J: STR UCTURE �s;·3"tviiri � o ,a io i ;o �a so .. TRAC£0 F, t1C R£ COMMEND�lJ . . ,�j · · · L.,. 1;;tin9 concrele 10 15 CHECK O O V CB. � APPRO,;£ O � VE. � SPI. 015CHALLWAYRGE DIS-THpUCHA5Atl0RGE SEC. CUR fT, SECTION SE C TION F-F · DETA IL OF METAL I-SEA L -�/-.fAN. , /� . .,;_O· . Sff/ECScaTIONle Fe D-Det i W � :::: v1--F1 t I :r-r:� LJ -1- 1--=I � 'Z.B99 I ornvc•.�ocoR,oo. .,on of ?- � 1\..JUK::_ ri \ ", .. �=I ., .\:."'- fl I\ L ·' . n � '(///. '1 / . : \ (( 1 f,.; / • I / • \, \ � 11 I ' . \, \ ' .·.(. : J'. , ' r1 C //4 ' ·-·-- � ,(1.ri� ·t"------.::-,· · \ - '. \ \ \ ,· , · · I . ·o \ . \ "',- ' 0 17 FOREST SERVICE L , PACK TRAIL·., '?"'� cl 0 "'p. 17 l.- j ·,·,. L .• \l INDEX MAP >: \ .''--- _j' ', ·:::--.."''------,, \ a L , ! -t' I_.,-· -- 1 ,, r )- Foundation rock ,�· ' , I ,, as excavated------· ' . I i· j,/ :::.�oriqina/ LJ ,/,,-, /' qround surfa ce I Bottom of ---��'- I . � .J< 'l·,,, ,, uJ> 4-6501-----t---J., cut-off trench---·· '- '� I Power J[g][g]f , ,, J.- ·,:___ Top of con ere te outlet.. : .... '- ' I / backfill u ' ', ',k < '-.....: ',. , f ' ! Tr ashrack --. ::v ', i '-,,, I _ ,I,.) �"' "6001 / n;z: I I . , r, a: .. Et__i.t-_�_'+-.?.§'· \ I ______j ______LJ [/. 4 711. 5 I-... '- ', / - .J _, ',, b- =r:===::'.:'.:4 ' ------e '-,", ',, .. ,{ • I , � ---- .L ____ ....,J__ ,,, \\\LL co=--...J.7J.. ______..,_ __ --- L. ..- .. :),,._"{-:").._ - "· {)� 1�� . \, ,\ '- ---- NEEDLE VALVE DISCHARGE - HUNBREDS Of' SEC. F'T. •. . ·1- 5 10 l5 7.0 7.5 ' ., ...,___ . J'+ - 0 10 '20 30 40 so -- D£.VEL0PED UPSTREAM £LE.V- AT/ON ' SPILLWAY OISCHARGE · THOUSANOS Of' SEC. f'T. --"= ' AREA-CAPAC ITY- DISCHARGE CURVES LJ 10 0 ' 0 15 .Sca50 le 10of0 ---fe15--0et O�PARTMENT OF THE INTERI Olt }. BUREAU OF RECL..AMATION SUN RIVER PR Ot.JECT-MOOTAHA L� GI BSON OAM SPI LLWAY ALTERATI ON S LO CATION MAP GENERAL PLAN-DClSTING STRUCTURE L..1 - £t. 4550.0 ------S E C TION THRU SPILLWAY TUNNEL �t��;-��� I 0£HV£R , �O=;_ -.,�_,;:?Z:L:... - . __ 1 L.J "' \._) LJ LI was 12 .28 inche s when it should have been 11.12 inche s. The sheet-metal LJ discharge tunnel connected to the down stream side of the elbow wa s thus placed 1.18 inches too low. However, such a discrepancy was not con L.J sidered important because it did not affect the flow past the gates and into the spl 11wa.y. 'u The piers, bobtail in the original des i gn,were made of treated ,� redwo od he ld in position by an angle frame joining them together at the top. The radial gates, of sheet me tal , were fitted into slots between tr1e piers on the original de slgns, but were pivoted on hinge s in the final de signs . ,L_j ·r--,.-. To me asure pressures in the model, piezometers were placed in the LJ spil lway entrance, as shown in figure llA. Other piez.ometers in the transiti on and the elbow were avai lable but not used, except for quali tative observations. The discharge wa s me asured over a V-notched weir and was brought to the model through a flume . 9. The original design of the Gibson Dam spillway-gate structure . L_J Tests were divided into two groupsi in the fir st, or origi na l desi gn, the radial gates fac ed upstream, and in the second, or fina l des ign, the gates were reversed and fa.cad downs tream . Ra.dial gates of the type used a.t Gibson Dam are ordinarily swung faoing upstream with the hinge LJ pins swung downs tream. Thus, th ey a.re accessible for maintenance at all times. However, during the course of the studies on the spillway 1 L;,I·.· ._ for Gibson Dam, it was found that a mo re compa.ot arrangeme nt wou ld be possible if the gates we re reversed from their conventional positi on. Only visual tests were ma.de on the origi na l des.ign because several adverse features ware apparent immediately. The bobtai l piers ca.used la r;e fins downstream. ���� ilp:(e :ir§ ,i;:��i.i'UlA-�vfs/d/vffi&� Severe ne Eative pressures occurred in the spillway entranc e below the break in profile at elev. 4704.2. There was an unstable flow c ondition Li at the maximum discharge, causing a. surging action where the spi llway shaft alternate ls filled and emptie d, as was ob served in the Owyhee \_... I model , The orit�i nal design wa s the refore revised. By e.ddint-:; pie r ta.i ls. 19 \__ ,- FIGURE 9 ,, -< - - =rr--_:__�1L_'nq poo ,-1I -- 0.30'>' I;. 34' · - ...... ,,- .. -x+ -,c-- • 335" ---;,-- -- · 1 - - /� 7 __ : 1: I . . - 11 -<- I. 6'.J".,- ·E/ 4-735 0 -4.�----�----· -- Same ([------I 4735. 0- . See De tail A :... I . cr -:,-Ar� i 1x 1x8 An1.,: :rG�t? r-,- -'-= ·1-:---1, .. !: ·, t117-c ' \ _-,;_. Flum;: Pie.-. E/_ 0:34"R. El 4724. 0 \ 1 ._ , ·._ _ PIER A � 1 El 47 2/. 5· -/ I I (E: 4 :38 so on final, des,q,, ' ,-731- 1 - -:. '•Q° 6 I l.I -... . .\ n :_ I I tI . ., -'. I • / f n! li ' Cres t. El 47!Z O -'i . - - -· ')------'---',.______I , ,' - u -- _\- ·.-, -<.- ·-1 -----=------1. !__ ' 7,_ _ [7, ·· El 4-704.2 No re 1i/ S1ons o ab1Jtment ; ,· oie." ·-- , . ., S, ,n oriq,no; des,qn. 1�I ..1ii > '----' ,:,: ,; '.�7Zr-I, ��! : .. , l: / _ _ _ _ L_t -b 1 --�So -��,!hd I/' _..-This surface _worpedy.--.,..- ---;--�---- Topoqr.;,p hy def a, I-s lc,cco ··Et. 4676. 0 ./ ·-· r- I · I . I to fd to sp,lfway · -�_ J on metal lath -_,_· . J. PIER F . '.I .Trans/ti,Jn sec. < : crest ond i,p __ /.· ABOUT �------FINAL OESIGN - - -: · -:------;- · · ------· - '' - - - - - ;, x.: 1 I I ' Walkway ___ _ _ .,, , I · -I;'Pyra lin 'I-- - - - (Elevation similar tc I , tI · Ix " ."rarre @ 8"-- --- [_ ---i Crest- El 4712.00 /SPILLWAYSYMMETR 1!1 II f 6 ·. 6.88· - . - . , 1 ii j . ·El. 4623.7S Pier G) ------� 1 0. 9/"r-< I _ _ _ - ,_J Figure 10 A. REVISED ORIGINAL· "l'JESIOW PLASTICENE FILLET IN CREsr B. REVISED ORIGINAL DESIGN AND PIER TAILS ADDED DISCHARGE = . 30 ,000 C.F.S. o C. FINAL DESIGN - 22½0 PIERS D. DESIGN USING ·45 PIERS GATES OPEN GATES RAISED 3 FEEr DISCHARGE = 35 ,000 C.F.S. DISCHARGE = 13,000 C.F.S. THE 1: 63.6 HYDRAULIC MODEL OF THE GIBSON D.AM SPILLWAY FIGURE. II _.-Q• 1;9,000 C.F.S. , Q• 20,000 CFS -<--- r Cest,,,-"·-'------ r-. A ,' _.--'-Piezo:nefer !ocaf10ns '-�')_j SECTION A·A SECTION B-B NOTES Pressure measured on revised crest of oriqinal design, which is similar to crest of finalde sign ,--, A. APPROXIMATE PRESSURE DISTRIBUTION ON SPILLWAY CREST NOTE S LJ The discharge curve is forfre e flow over crest that is with the gates wide open_ Z. The coefficient of discharge "C' is obtamed from .-Without restrict the relationship Q= CLH3!z where Q=discharqe L•lenqfh � ion in funne I LJ of crest at crest 't and l-f head above crest. = I ,-With restriction I · : in funnel to LJ 1 47Z8 16 ,), orevent unstable · .• I�,, flow Not used -- ..,, ;f' in f, naI des iqn -- \__ _J 14 I /!' -- I I 41 l4 12 y I ....1- uJ / u_ 1- uJ uJ � 10 / / \._I 1 z � ;: I- <( VI '/I :;, . uJ uJ a:: 4720 u 8 .;j I uJ uJu > Ois charqr -�-� 1-<�-Coeffic f·en :I y / l a: � 6 j uJ I uJ :c --·------· ----- 47 16 4 /" /1 '2 I II ' - 47 1 '2 0 2.S 3.0 3.5 COEFFICIENT Of DISCHARGE 'u 0 iO 20 30 40 50 DISCHARGE IN THOUSAND SECOND FEE.T RELATION OF HEAD TO DISCHARGE L__/ GIBSON D_A M - SPILLWAY ALTERAT IONS HYDRAULIC MODEL STUDIES J:63.6 PRESSB. URE AND DISCHARGE CURVES FOR FINAL DESIGN !,____i _ the fi ns downstream from the piers were reduced; by rounding the crest LJ wi th a plasticine fi llet, negative pressures ca.used by the break in the crest profi le at elev . 4704 .30 were eliminated; and by plac ing a. block u in the tu rme l near the exit, the su rging fl ow at maximum discharge wa s avoided (figure 9 E and F, revi sion 1). LJ. 10 . Pre ssure s on cres t. As thi s revised crest design appeared satisfactory, detailed pressure measurements were made (figure 11) . LJ Pressure curves for discharges of 20,000 and 49 ,000 second-feet, respec tively, shown in this fi6ure, are typical of pressure measurements at other di scharges, A maximum negative pressure of 5.8 feet was recorded LJ ., at the spillway entranc e. It is possible tha t more severe negative pressu res, and even cavitati on, mi ght exist in the prototype below the spillway entrance sh ould the spillway become subme rged . Howeve r, as this would be a rare occurrence of relatively short durati on , no great damage should result. ,"', 11, Ca.u se of surging at max imum di scharge . A study wa.s made to determine the cause of surging a.t maximum dis char ge when the shaft alternately filled and emptied. It was found experimental ly that a b lock, or a choke , near the tunne l exit wou ld effectively redu ce or eliminate this action. The explanati on seemed to lie in the fac t that the re wa s a change in flow regimen a.nd a shift of controls when the shaft fi lled. Actually, the control may be located at three points. At normal di scharge , the control was at the circular crestJ but , a.s the head i. ncreased, e. flow was reached when the crest subme rged and the con trol shifted, either to an orifice near the top of the shaft, the loca ti on dependin� upon the sh ape of the inlet, or to a control at the bot tom of the shaft . This third co ntro l wa s really hypothetical and in cluded the resi stance and the obs tructions in the tunnel, the elbow, and the verti cal shaft , For moderate di scharges when the control wa s at the crest, the control at the bottom of the sh.aft would also back L.1 water up the shaft some height, dependi ng upon the di scharg;e . As the head increased, iY1c reasi:i.g; the di s char 6e, water wou ld back up the shaft "7 LJ \ _ _J and it wa s af)pe.rent that eventually the shaft wou ld be fi lled and th e LJ crest submerged. However, before the shaft filled , a head wa s reached r-,_ at which the contro l shifted from the crest to the orifice at the top Ld of the spillway , submer;;in,:, the crest before the shaft below was fi lled. When this occurred, pressure s at the orifice were negative as soon as LJ the crest submerted , The ne gative pressures acted to increase the 1----i velocity and the dis charge in the shaft, and to lower the head; so the control shifted back to the crest, whereupon the shaft emptied and the LJ neg;ative pressures were relieved by an inhalation of air. Then, with ,-, less discharge in the sha ft, the contr ol again shifted to the orifice, w the cre st subme rged, and the cJrc le was repeated . As the experiments indicated, it wa s possible to avoid this un LJ favorab le condition by placinG a re stricti on in the tunnel near the exit to increase the re sistanc e of the control at the bottom of the shaft . The water rising in the shaft would then submerge the crest before th e head was sufficient to cause the contro l to shift from the crest to the \.. j ori fi ce. However, such a restriction not being a practical solution, nothing wa s done to alleviate this unfavorable condition at the Gibson spil lway, In future designs of gl ory-hole spillways , the shaft might -- be so proporti oned that the combined resistance in the tunnel. e.nd the _., -,: _ shaft would be sufficient to fill the shaft before the control could L...... J sh ift from the crest to the orifice. 12 . Air in the shaft . Anothe r method of eliminatin� surgin� flow at maximum discharge wou ld be to provide air vents in the shaft to re lieve ne iative pressures. The use of air vents was not considered be U_ cause the events tha.t might occur in the prototypa are extremely un certain as far as the inhalation and the ejection of air are concerned . LJ Air bubbles that were drawn into the mo de l were compressed at the bot tom of the shaft and in the tunnel and then ejected from the tunnel in ;____, �i ch manner as to SUf,gest that if similar bubble s exi sted in the proto type, they wou ld virtually explode at the exit. Nothing could be done L . J to prevent the entrainment of air in the prototype ; but a flood great 24 ./,___ > Le \ ) __ enou g;h to cause a surging flow, wi th the inhalation of air in large LJ gulps, would be a rare occurrence of short du ration . So any damage that mi ght result shou ld not be extensive . ld Since the mo del studie s on the Gibson spillway ( 1936) , this condi tion, explosion of air bubbles at the tu nnel exit, actually occurred in (_J a similar type of sp illway at San Pablo Dam in California. Intense vi bration resulted, and the tunnel lining at the exit portal was ru ptured. A comple te revision of the San Pablo spillway was necessary to prevent recurrence of damage. At other spillways , however,· it has been observed that the action of air is not always the same , it may be ejected as a strong windJ it may be mixed with water to form foam1 as observed at Owyhee, it may regurgitate from the entrano eJ or, as also observed at Owyhee , it may cause an exp losion when reflected waves seal the entranc e, as described in section 6. �n the case of the San Pablo Dam, the fact that the exit was submerged may have been the cause of the trouble . However, this is not certain. To understand, to predict, and to control \.... J the action of air in a glory-hole spillway is a problem for the future. The use of air vents in the bottom of the tunnel hasbe en suggested; but 'L.J they may not be completely effective . If the air ia mixed with the water, only a small porti on may be vented, or, if the air is compressed a s bubble s, the relief into the vent may cause vibration in the same L,...i. ma.:nner as would the dis charge from the tunnel exit . 13 . The final de sign of Gibson Dam spillway with radial gates :�J ,·_·:_ : faced downstream. As far as the hydraulic s were concerned, the revise4 original de sign was satisfactory; however, a more compa ct arrangement 1...,.1. was desirable. This wa s accomplished by reversing the gates so th at they faced downstream. The final crest design was similar to the crest 1-,._J _ ,' of the revi sed original design, but much shorter . The piers were laid out in a more symme trical pattern than before, although the ir general '\,_j loc ation was the s ame (figure 9K) . Two type s of piers were proposed, a 22-1/2-degree pier a nd a 45-de�ree pier. The 22-1/2 -degree pier was tested fir st and selected as the final desi gn when no rna.rked improvements 25 L_ J 1.-.., �--, . i.__J c ould be seen in later tests on t>.e 45-derree piers . Four tests on thi s \_ _J final arrangement were ma.de. In test l, 22-1/2-degree piers e.nd abut ments were used ( piers F and (} , fi :Y re 9G ). Runs we re made e.. t discharge s LJ of 11,100 , 15,200, 25, 200 , 35 , 000, 45,300, and 50, 100 second-feet, re spectively . A run wa s also ma de e.t maximum discharge with a block in the ILJ turme l to staLilize t:10 flow. No detai le d pressure mea surements ware me.de in this test. Test 2 wa s similar to test l except that a 30-degree fillet wa s placed at the upstream edEe of the crest to improve the fl ow over the crest . The fillet, howeve r, was not very effective . Test 3 wa s simi lar to te st 2 except that 45-degree piers and abutments were used instead of the 22-1/2 -degree piers ( piers E and F, figure 9G) . No marked improveme nt of the flow conditions wa s observed . Test 4 wa s similar to L.J te st 3 except that the fillet at the upstream edge of the oreat was re . -, moved • Test l wa s selected for the final design. No pressure measurements were made, as the crest wa s similar to the revi sed crest of the original '-· f design and it wa s considered thut those pressure measurements would suf fice (figure 11) . A discharge rating curve and a discharge-coefficient curve, with the gates raised, is shown for the fi nal design on figure 11. The dis charge rating curve shows a maximum stable flow of 45, 000 second feet _wi th a 15-foot head over the crest . The coefficient of discharge , _L .;_ which is about 3.4 for thi s head , wa s based upon the relati on 3 2 Q = CL (H) / , whe re L is the total c r est length between the piers . Thi s coefficient cannot be compa red with the coefficient for the Owyhee spillway, or others, because, as alre ady mentioned, the coefficient of 1...._ .I• . a glory-hole spil lway is not an index of the spillway capac ity. To conc lude tests on the Gibson spil lway, a series of runs were ma.de wi th the g;ates at partial openin1;s, varying; the di scharge and the head .' From all appearances, the operation of the prototype would be satisfactory under all conditions . 1.-J 25 �J L.J REFERENCES TO OTHER GLORY-HOLE SPILLWAYS LJ 14. The Davis Bridge Dam spi llway. The widespread use of earth- fill dams at looa.ti ons not su itable for masonry dams was largely responsible ,---, for the introduction of shaf t spillways . When a masonry da.m is located.in J a. narrow valley wi th steeply rising hills on both sides, a bypass for the L spillway is not feas ible and the spillway is incorporate d in the da.m. In the case · of an earth-fill dam at a. simi lar location, a spillway over the \_./ dam itself wo uld not always be safe, and one solution is to use a shaft spillway . An attractive des ign was the vertical-shaft or glory- hole spill LJ way because of the economy of construction, especial ly -when a diversion tunnel was necessary, fo r, in suoh oiroumstanoes, the shaft could be joined LJ with the diver sion tunnel. However, many engineers were rel uctant to use glory-hole spillways as there were several apparent disadvantage s . For instanoe, the discha rge ca pacity was limited; also, the· water falling into the shaft would act as LJ an air pump, compressing lar ge quantities of air in the shaft, with uncer tain resu lts. Prior to 1924 there were very few spi llways of thi s type in existance, and practically no informtion concerning their de s ign was avai lable. A paper by Ford Kurtz, "The Hydrau l ic Design of the Shaft Spi ll way for the Davis Bridge Dam and Hy draulic Tests on Working Models, " Trans. \_ ( A.S .C.E. , vol . 88, 1925, was one of the first comprehensive treatments of the subject. To this paper were added the dis cussions of several prominent �J . engineers, Mucl1. of their criticism wa.s adverse. Nevertheless, the use of this type of'· spillway has increased, and the re is now more literature upon the sub ject covering prototype installations, model studies, and basio in r-, vestigations. The Davis Bridge Dam, an -earth-fill structure 200 feet hi�h, is located on the Deerfield River a bout three quarte rs of a mi le south of' Whiti ngha.m, LJ Vermont. This dam is situated in the neck of a narrow valley with high, surrounding hills , making the use of an overfl ow type of spillway impr ao tica.l. A glory-hole or shaft spillway wa s both practical and economical . L . ./ The entraitce of the vertical shaft, 22 . 5 feet in diameter, was placed on a 27 �J \. r shelf above the diversion tunnel and connected to the tunnel by a 90- LJ degree elbow. The basis of the theoretical design was to reke the entrance circu L.J lar and reduce it to a uniform diameter of 22.5 feet as soon as the water falling over the lip could be accelerated to the required velocity . To accomplish thi s, the desi gn was separated into four distinct parts 1 ,-. (a) A circular, broad-crested weir wa s used at the up , __j stream edgs of the entrance, with the coefficient assume d to be the same as tha t for a similar rectilinear weir. L_J (b) Below the downstream edge of the weir the re was an open section which was designed to fit the nappe of the freely falling jet. The shape of the nappe was determine d by assuming '-. .. J the path of the wa.te r a t the center line of the jet to be a pa rabola . This section continued unti l the jet closed upon itself, L.J (c) The closed porti on of the fr eely falling jet. This section continued unti l the required velocity throuGhout the Li remainder of the shaft wa s reached. (d) The remainder of the design involved the closed ver \..... ) tical shaft, the elbow, and the diversion tunne l. These sec tions were desi gned from regular formula e for pipes and bends. l ,{ To check th is theoretical design, a model wasbu i lt on a scale of 1 to 36 and te sted at tho Alden Hydraulic Laboratory of the Worcester l,.___ ...J . Polytechnic Institute at Worcester, Mass. Later, the model was moved to the testing flume of the Power Constructi on Company on Sada.wga Brook, near Whitingham, Vermont. LI The Worcester tests were to ascertain the capaci ty of the spil lway and to observt:i the manner in wh ich the water entered the spillway. No topography was inc luded in these tests, so the flow was symmetrical. Ti1e d.is cha:r1c,e capacity checked the theoretical ce.paci t;r, and the fl ow ·.::ondi tiona were as aEt:,. cipa. ted exct:Jpt tha t a mushroom of Wi:i. Cer a.p;,:iea.red where the jet car.Ia tof�ethe r. This mushroom ha d no effect U.i)On the flow L_ .i ir,to the spillway . Nega ti ve pressu!"es were observed on several sec tions "...... •. J \_ .I- of t.ie spillway entrance. LJ In the Whitingham tests the effect of the topography, a spiral approach to the spi llway , and the effect of piers and fla shboa.rds set LJ between the piers we re studied. The capacity was the same as before. The piers were use£'u l in forcing the water to fl ow into the spillway (_j in a :norc symme trical pattern . 15. Model experiments by British engineers . The glory-hole or LJ shaft spillway has been used in England as far back as 1896. Although ,c-', it is doubtful that nodel studie s were made in connection with the de LJ sign of the earl ier spillways , at more recent installation s modt11l studies ha ve been used . or pa. rticu lar importanc e are investigati ons which have been described in a series of papers by W . J. E. Binnie , G. M. Binnie , A, M, Binnie, and R. K, Wright , In "Bel lmouthed We irs and Tunnel Outlets for the Disposal of Flood iiate r,11 by Vi. J. E, Binnie, Transactions of the Institution of Wa ter Zn�ineers, vol , XLII, 1937, there are descripti ons of seven bellmouthe d or g, lory-hole spi llwa.y s in the British Empire and in the Uni tad Sta.te s , followed by a resumb and results of model studies involved in the de \_/ sicns of some of the se struc tures. The spillways described we re 1 \_ J· . ( l) The spi llway for the Taf Feehan Re sarvoi r in Wal es, de• signed in 1912 . The bellmouthe d entranc e of this sp i llway flared inward from a 66-foot dia..�e ter crest to a 16-foot di ameter sh�ft 30 feet below the cre st. The shaft was conne cted to a 13- foot diameter tunnel 93,7 feet below the crest . The capacity was 3,040 second-feet, To prevent the fo rmation of a vortex , four fins , 9 inche s wide, were placed on the bellmouth ent rance. (2) A simila r spil lway for the Silent Valley Reservo ir in Ireland , des igne d in 1926, wh ose entrance flared inward from an 80-foot diiw.eter crest to a 16-foot di ameter shaft 27 .5 be l__ J feet low the crest . The shaft was conne cted to a 16-foot diameter tun�e l 4G .6 feet t,elow the crest. The capac ity wa s 2,600 second feet. Four fi.ns were used to prevent tl: e formation of a vortex . ( 3) Tr�e spi l lwa.:.· f;)r tne Pontian Ketohil Reservoir at Sin;e.pore, desi,�ne d i:J U27, :1a d a.n entrance wnich flared inward frorn a 50-foot diameter cre;;t to a 13-foot diame ter shaft 23 feet 29 l__ i LJ Li below the crest. The shaft wa s connected to a 13-foot dia meter tunnel 53 feet below the crest. The maximum cap acity was 2,700 second-feet. To prevent the formation of a vortex , 15 re.dial piers were placed on the crest ins tead of using LJ fins in the bellmouth entrance. This des ign resulted from model tests of the Davis Bridge Da.m spillwayw hich indicated that piers imp roved the f'low into the spillway. /.__J ( 4 ) The shaft spillway at D·avis Bridge Dam, which was discussed in secti on 14 . u (5) The spillway for the Burnhope Re servoir in England , designed in 1932-34 . The entrance fl ared inward from a 50- foot diame ter crest to a 12-foot diameter shaft 25 feet below L.J the _crest. The shaft was connected to a 12-foot diamete r tunnel 97 .6 feet bel ow the c rest. The capacitywa s 2,630 I,.____, , second-feet. A curtain wall and two fins were used to prevent LJ the formation of a. vortex, as the results of tests on a mo del of the Manuherikia Falls spil lway indicated that a curtain wall was the best device for vortex prevention . LI (6) The spi llway for the Manuherikia Falls Dam in New Zealand , designe d in 1932. The entrtnc e flared inward from a. 102-foot diameter crest to a 17-foot diameter shaft 55 feet L.1 below the crest. This shaft connec ted to a 17-foot diameter tunnel . The cap acity was 19 ,400 second-feet. Six piers were used to prevent the fo�tion of a vo rtex. (7) The spillway for the Jubi lee Reservoir at Hong KonG, China, de signedabou t 1933 . The entranc e differed from other spillways in that it consisted or a conical shaft instead of L-1 <· : - � bell�o�th, This conical entrance tapered inward from a 74- foot diameter crest to a 25-foot diameter shaft 37 fe et below _...-.., _· the crest. This shaft, only 3 feet 2-1/2 inche s lonr,, imme diately connected with a sloping tunnel 15 feet in diame ter . · , ..-� and several hundred feet long,. A curtain wal l was used to pre vent the formation of a vortex . The capacity of this spillway :---t . wa s 11, 300 second-feet. _ ...... :.., The model experiments by the Briti sh considered first the reliabi L.J lity of the model results applied to the prototype . For the Jubilee Reservo ir, experiments ma.de wi th mod els constructed to scal es .of 1119, 1124, 1129.4 1 and 1143 .5 indicated that the model would predict closely L.) the pe rformance of the prototype, To study the effect of entrained air, · - !-----, . me asurerr,ent s were made on a 1124 scale mo del of the Burnhope spillway . L.J The results demonstrated that entrained air had no effect upon the L . .i 30 ,--.. [..._) LJ di scha rge at maxir.1um cape.city, a.nd tha t a.t lesser dis charges th e effect and the vo lume of the entrai ned air was immaterial. A large number of expe riments we re made to study the fo rms.ti on and the prevention of vor· LJ tex flow in the spillways. The importanc e of preventing vortex flow is emphasized in the Jubilee expe riments where the fo nnation of a vortex LI decreased the discharr,e from 14 , 000 to 9,000 second-feet. Model experi ments showed tha.t the depth at which a. vortex forms is not constant and tha t it is influenc ed by the surrounding topography. other conditions L.J which may cau se tangential velocities, and the fonn of the spil lway itself . Tne use o·r fi ns in the bel lmouth, radial piers, and curtain LJ wa lls wi ll delay the tormation of a vortex, the cu rtain wall being the ,ri mo st effec tive device . The ou rta.in wa ll divides the bellmouth into two LJ semicircu lar we irs. Tests were made to find the optimum depth that the ,-.. curtain wal l shou ld extend into the entrance . LJ This article describes the experiments on the fo ur models of the Jubilee He servoir . At the othe r spillways described , the like lihood of flood s gre9.t enow,:, h to choke the spi llways wa.s remote . However, in the region of China , where the Jubilee Reservo ir is located , rains torms occur s o severe that the p�ssibil ity of the inle t becoming gor ged is one of maj or concern . � his necessi tated, first, an auxi liary spillway oon sisti nr, of six siphons capable of discha rging 6,000 sec ond-feet. A more w careful considerati on of the conditi ons occurrinr in the bel lmouth spillway at maxi mum capac.ity wa s also necessary. The bellmouth ent rance µ. of the original desi6n wa s shaped simi la r to tho se previously oonstruo ted . A curtain wall wa s used to prevent the formation of a vortex , and air L-1 vents we re used to relieve negative pressures below the bellmouthed entrance . 'Ni thout a.ir ven ts, a l':8.ximura di scharge of 15,000 second-feet wa � reached; bu t at a discharge of 9,700 second-feet, violent suriing LJ of tne wa ter level in the entrance took place (such as was observed in ,,-, the Owyhee an:i th e Gibson motl� ls). i1. S this surging was caused by vacu L.J ums below the a·,·�.,ance , ti,e tt ir vent s eliminated th is conditi o,1; but the diso hur:�e wa s co1�siderably reduced, e.nd uns table , varying from 11, 300 31 . \,__ __ ) \_J to 9,000 second-feet. LJ A theore tical design was proposed to elimina te ne gntive pressures LJ in the shaft. This de sign consisted of a oonioal shaft tapered inwa rd to a minimum di ameter at the bottom so that there cou ld be no control exoept at the bottom. Such a de si gn could not be used in the prototype , LJ for it requi red a ho rizontal tunnel , whereas the in clined tunn el in th e Jubilee Reservoir spil lway was nearly completed at the time of the ex periments. Nevertheless, the entrance section of the final design was modified by using a conical shaft instead of the bellmou thed shape as u · used in the previous installa tions . This revision conside rably improved the perfo rmance of the spillway by reducing the vacuums, increasing the u di scharge from 11,300 to 14,000 second -feat (with air vents), and by greatly reducing the degree of surging in the entrance . There we re neg ative pressures in the sloping tunnel, so air vent s we re used to avoid \__ J the possibility of ab solute vacuums in the prototype . A hood was placed ove r the spillway entrance to form a siphon LJ bellmouth ove rflow. The siphon primed successfully, and the scheme offered possibilities although it _was not ad opted at the Jub ilee Re ser L..J voir. The oonolusions from these experiment s were , LJ �(a) That model experiments, provided the model rati o is not too small, oan be used to predict approximately the relation between � and H for the prototype. "(b) That the rate of discharge obtained with the prototype wi ll be better at corre spondi ng depths than predicted by the model. •(o) That a steadier flow at high rates of di s charge is ob tai ned by using a conical shaft rather than the type of bellmouth LJ hitherto adopted. "(d) That better results , as far as reduction of vacuums is concerned, are obtai ned with a. nearly horizontal tunnel rather than with one which is steeply inclined. LJ 32 LJ LI "(e) That a curtain wall, extendin� across th e waterway so as to divid e the bellmouth into two semi-c irc ular weir s, is the be st ant i-vortex dev ice . u "(f) That the oross-seotional area of the channel of LJ approach should be such as to limit the tange ntial veloc ity to 3.5 feet per second at any cross section. L.J "(g) That the tunnel should be made of suc h cross sectional area as to prevent the formation of considerable va.ouwns. "(h) That the radius of the bend where the shaft joins the tunnel should also be such as to prevent the setting up of an appreciable vacuum at the maximum rate of discharge." r'·= 7. · In "Model Experiments of Bellmouth and Siphon-Bellmouth Overflow Spillways ," Insti tution of Civi l Engineers, vol. 10, November 1938- Je.nua�y 1939, G. M, Binnie describes in greater detail th e experiments on the Jubilee Reservoir sp illway. L..J In a paper, "The Use of a Vertical Pipe as an Overflow for a Large Tank, " Proo . Royal Soci ety of London, Series A, vol. 168, 1938, p. 219, LJ A, M. Binnie describes an investigation concerned mainly with the be havior of vertical pipes of uniform diameter. A few exper iment s were l_j performed with bellmou ths of different shapes for purpo ses of compari �· · son . In the se tests it was demonstrated th.at the re was a definite \. ...,.j· limit to the discharge through the over flow. Above a certain head, de pending upon the form of the inle t and the tailpiece, the outlet vir tually refused to pass mo re water . 1 In 'Le.bora.tory Experiments on Bellmouth Spi llways, " by A , M. c_J Binnie and R. K. Wright, Institution of Civil Engi neers, vol. 15, November 1940-February 1941, there are descrip tions of fu rthe r studie s. The apparatu s was a circular tank with an overflow pipe in the center LJ whose inside diameter wa s 1 ino h. Different types of bel l�outh en trances could be plac ed on this overflow pipe, and different types of LJ ta ilpi eoes could be used bel ow it . Water flowed int,, the tankin a radial manner, so the stream fi laments avproaching the entrance were re.::l.l.al and L_ .i 33 ;_J '.___ ] there were no tangenti al velocities which could cause vortex flow. An L..J apparatus wa s deve loped for measuring air. The tests studied two types of bellmouth entrances; one , a shallow L ... J bel lmou�1 , and the other, a deep , conical bel lmouth su ch as was used at the Jubilee Reservoir spillway . Seven tests were ma.de, with each en ,.,.-1 trance, by changing the tailpiece, or exits ( 1) The ta.ilpiece was � 1-inch vertical pipe 5 feet long, unobstructed. L.. .J ( 2) The same as (1), with an orifi ce 0.880 inch in dia- 1 ·· , meter at the exit . LI (3) The same as (1), with an ori fice 0.687 inch in dia- me ter at the exit. (4) The same as ( 1), with a horizontal pipe 20 feet long \_j added, being connected to the verti cal pipe with a 90-degree bend havi ng a radius of 3.15 inche s . (5) The same as (4), but with an orifice 0.880 inch in diameter at the exit. (6 ) The same as (4), but with an orifice 0.687 inch in diameter at the exit . L..J (7) The same as (4), but with the exit connected to the suction side of a pump . The results of the experiments we re 1 "(a) Whatever the arrangement of the bellmouth and tail piece that wa s te.sted with rising head under ideal oondi ti ons , the re wa s at fi rst a. qu iet stage with no important entrai nment of air. This was followed by a noisy phase when the air in ·,L..J the form of bubbles wa s drawn down ; but the air flow diminished as the head increased further. Above a sharply marked critical head , the bel lmouth and pipe ran full and the water flow re L..J mained almost constant at its critical value. Below the crit ical head the bellmouth acted a.s a we ir; the water flow was not reduced by the entrainment of air. "(b) At he ads above critical, no pe rmanent vortices were formed. Transient vortices were more common with bellmouth B (a shallow, curved trumpet) than wi th bellmouth A (a deep cone ). This re sul L is attri butable to the la. rse negative pressures cene rated in bel lmouth B near its crest, "I� C} , All of the critic11l heads and water flows for the \...... J LI LJ vari ous tai lpieoes attached to either bellmouth lay on the head-discharge curve OQtainod with the tai lpiece that caused the greatest flow. This result can be utilized when the dis charge through a new tailpiece is to be' predicted. "( d) Owing to the better form of the crest. the coeffi cient of dischar ge of bellmouth A was considerably higher tha.n that of bellmouth B. An improved and practicable form of bell mouth could therefore be designed, combining the upper part of the forme r with the lower pa rt of the latter. "(e) When a small tangential velocity was imparted to the water entering the bellmou th B, the coe fficients of discharge were practically unaltered but the critical head and fl ow were reduced considerab ly. At heads above criti cal , a permanent vor tex was formed.• It was pointed out that the model tests were on suoh a small soale it would be unwise and unfai r to attempt to app ly the resu lts to a larger structure quantitatively, especially for mea surements of air, \.__ j Discussi ons of this paper are given in the Instituti on of Civil Engineers, vol. 16 , Maroh-Ootober, 1941, pp. 451-469 . LJ 16 . Bibliography of additional literature . l. Anonymous, LJ "Calaveras Dam Rai sed with Dry Fill and Puddled Core." Engineering News-ijeoord , vol. 90, No. 3, Jan , 18, 1923, pp. 117-18 . Additional material brings total hei ght to 176 feet J ooncirete L. ...1 spillway and new out let tunnel providedJ this outlet tunnd of a glory-hole type . :'.__J ' 2. Connor , A, P. "Glory-Hole Spillway. " Power Plant Engineeri ng, November 1933. Description of control at Owyhee Dam , Oregon, by ring gate, vertical sp illway intake into a horizontal tunnel. 3. Jaeger, C. L-' "Notes sur le caoul des deversoirs de aeuila," Bul . Technique de la Sui sse Romande, v. 59 , n 13 an d 14, June 24 , 1933, pp. 163•56, and Ju ly 8, pp. 166-69, LJ Theoretical study of rounded c rest spillways and weirsJ compari son of theoretical formu las with results obtained by Esoande, Rehbock , and other European e�perimenters in hyd rau lic s. 35 LJ L-1 L.J 4. Van Norman, H. A . LJ "Bouquet Canyon Reservoir a.nd Dam ," Civil Engineering, vol . 4, No . 8 , August 1934, pp. 393-97, A general description of the oonstruotion of Bouquet Canyon Dam, L.J an earth-fill dam looated about four miles east of Los Angeles, California, and used to store water from the Owens Valley Aque duct. For a spillway, this dam uses a vertical shaft, or glory hole , having an inside diameter of 8 feet, a drop of 163 feet, i__J and design ed for a maximum flood of 7,200 second-feet. 5. Anonymou s. "Tests of Shaft Spillway Models ." Engineering News-Reoord, Oot. 17, 1935 . \_ __J An outline of results of teats on a shaft spillwayfo r the pro posed Suls.k Re servoir in northern Cauoasia, U.S,S.R., and for a smaller shaft spillway for the Sion Reservoir. The shaft spill way for the Sulak Reservoir, 31 feet in diameter, with a vertioal LJ drop of 656 feet, wa s designed to passa diaoharge of 60,000 second-feet. Air inlets were used to relieve negative pres sures in the shaft . The smaller shaft, for the Sion Reservoir, had a capacity of 14,400 second-feet when the des ign was mod ifi ed along the lines of the Owyhee shaft spil lway in Oregon. Training walls were found ne ces sary to prevent vortex acti on. LI 6. Akhutin, Prof . A·. N . Artiole on above subject, title not known . Hydrotechnioheskoye ·L__} Stroielstvo, April 1936 . (Russian) 7. Park, A, G. '\!odel Tests for Bell-Mouth Shaft Spillway." New Zealand I nst. Engineers, Proo . 1937-1938, vol. 24, Part 1, 1938 , pp . 139-45 . Report on tests of spillway for Manuherikia rook-fi ll dam , New . ',L-,/ . Zealand . Designed, in aooordano e with theory developed for Davis Bridge Dam spillway in the United States, for a fl ow of · ,.----,_ 1 3 , 500 second-feet, with head over crest of 6 feet •. \___) 8. Jorissen, A. "Le Dersoir Circulaire in mince Paroni . " Revue Universelle des .Mines, vol. 14 ,· No. 13, Cec 1938 , PP • 823-32. Study of circular, thin-walled, overfall weirs, with special reference to causes of variation of coefficient of discharge. L__j 36 __ \.._J L-1 L..J 9. Bu z z e 11, D • A • "Keystone Dam Spillway Model." Engineering News-Record, vol. 120, No . 15, April 14, 1938 , p. 542. LJ Description of 1132 model "morning glory" spillway with flow of 50,000 second-feet, under construction for Keystone Dam in Nebraska. Crest of overflow weir is 101 feet in diameter; die.me ter of spi 11- wa.y tube is 28-1/2 feet. 10. Camp, C, s., and Howe , J. w. \ } "Tests of Circ ular Weirs." Civi l Engineering (NY) , vol . 9, No. 4, April 1939, pp. 247-48 . Results of laborat ory tests by Iowa Ins titute of Hydraulic Research LJ__ for determinati on of location of upper and lower profiles of nappe of vertical, sharp-crested weir, circular in plan; empirical dis charge formula for ci rcu lar weir. · 11. Cannell, P, J. "Me thod of Determining Lip of Circular Pipe Spillway." Civil Engi LJ neering (NY), vol. 10, No . 7, Ju ly 1940, PP • 450- 5 1. Description of me thod for determining curve for circular or morning glory type of spillway by modification of coordinates of rectangu \_J lar spil lway; test on circular model spillway. 12 . Smith, L. G. "Floating-Hing Gate and Glory-Hole Spillway a.t Owyhee Dam." Recla�ation Ere., vol . 30 , No . 8, August 1940, pp . 226-31. Description of glory-hole type of spillway at Owyhee Dam in Oregon, LJ noted for its unprecedented height of 309 feet, with 60-foot crest die.meter, ha.vine; 12-foot ov erflow height controlled with steel ring iate1 de scri pti on of gate controls and performance . \___J . ·. 13 . Verwoerd, A. L . "Capa.citeis.tbepa. ling van Volkomen en onvolaomen overlaten me t LJ . afgerond.e kr'uimen ." Ingenieur in Nederla.ndsch-Inde , vol . 8, No . 7, July 15, 1941, pp . I I-65 - II-78 . Determination of capacity of weirs with fu lly rounded and partially L.J round ed orests 1 formula and values of discharge coefficient appear ing in Rehbock equation; mathematical and graphical me thod of cal culati on . . L._J ,� LI LJ L. J LJ LJ 14 . Traheru , J. W. L..J "Design of Circular Spillway Modified to Cure Pulsating Disoharge .w Engineering News-Record, vol, 131, July 1, 1943, pp . 25 -27. Air was entrapped, with destructive results, in a ver tical-shaft LJ wasteny at the San Pablo Reservoir in Cal if orniaJ changes in de sign to prevent free fall of water in air a.re expected to end trouble, an expectation confirmed by tests on a mo de l of the re L. ..J vi sed de sign. (Air was ejected as exploding bubbles from the - submerged exit portal and caused sufficient vibration to rupture the tunnel lining at the portal.) LJ LJ LJ L.J LJ LJ LJ LJ · L./- . : --: '; ., c... J -0.66�- ·; ·Rev1s1on !-Or,qina/ des,qn- ' rj1' ,f -- I aF e !:ow , El 4-735o ··· I r -- , - -. - - -_a Pier fail V - .: ·-1" !I 90° Elbow· py,c;/1n 1 - ,:; ·-. - added '-, .. 1 7 I I � o , , 1S3,;. -� t, 0 ,_ 8- '7,wi !i-c_¼C. : I 5r!Ll- Pipe '.. l - -�,_-- .;.. /--'-II ... i. t "'� I -- - 1----...------r1 ::· ---Face of dam -, Note: qadius of elbow no t to · - - - . * I - n"3o·_ [�-- -. · --� �o --- - - ; I o.94-'R� I PIER B - · scale, the dimen. 1-Z}i' should be /1./2'' / ------',----f- I . ""'-.- I t,E: ,, \ / , '. ,.?,11 '-.... .-·Flume " 9' Pier symmetrical abouf <£ _/ ,.. \,.,... o .. - I . 3S------'& ,' � . c:: 12.1: - >: - _ C...... -�..;,· ..,._- I I 'O _\ _.·Sp;l/way /1� :'I-__ u .,, I cj f- ...,_. ------,, "' I COORDINATES FOR ' , / • o _.\ \.· El. 47/0'i. 2/ ·�s� I "'�