SPILLWAY DESIGN FOR A COMPOSITE DAM

Transcription

1 Vlume: 03 Issue: 04 April p-issn: SPILLWAY DESIGN FOR A COMPOSITE DAM Arun Jji 1, Nithya Thmas 2, Reshma Jse 3,Yapung Chije 4, Dr. Slly Gerge 5 1Arun Jji, Unde graduate, Dept. f Civil Engineering,MACE Kthamangalam 2Nithya Thmas, Unde graduate, Dept. f Civil Engineering,MACE Kthamangalam 3Reshma Jse, Unde graduate, Dept. f Civil Engineering,MACE Kthamangalam 4Yapung Chije, Unde graduate, Dept. f Civil Engineering,MACE Kthamangalam 5Dr.Slly Gerge,Prfessr, Dept. f Civil Engineering,MACE Kthamangalam,Kerala, India *** Abstract - Spillways are prvided fr strage and detentin dams which may nt fail with slight vertpping fr a dams t release surplus fldwater, which cannt be small perid f time. cntained in the alltted strage space. In this paper we have This dcument is template. We ask that authrs fllw sme designed a spillway fr a cmpsite dam prpsed at simple guidelines. In essence, we ask yu t make yur paper Kanthallr as a part f Pattiserry irrigatin prject. lk exactly like this dcument. The easiest way t d this is Pattiserry irrigatin prject envisages cnstructin f 140 m simply t dwnlad the template, and replace(cpy-paste) lng and 23m high cmpsite dam, earthen bund with the cntent with yur wn material. Number the reference cncrete verflw sectin, acrss the river chengalar a items cnsecutively in square brackets (e.g. [1]). Hwever tributary f Pambar river, lcated in Kanthallr village. The the authrs name can be used alng with the reference prject aims at irrigating 240 Ha f land in Marayr area, number in the running text. The rder f reference in the thrugh 8 km lng unlined canal. The prpsed dam is lcated running text shuld match with the list f references at the 5m dwnstream f the existing weir which is 20m lng and 5m end f the paper. high, cnstructed during The prpsed dam cmprises, 15m lng cncrete verflw sectin at the centre and 25m lng nn-verflw sectin n the right and 15m lng n the left. The cncrete sectin is flanked by earthen dam, 50 m lng 2. FACTORS AFFECTING SPILLWAY DESIGN in the left and 35m in the right. In the prpsed dam spillway is at the cncrete verflw sectin. We chse an gee type spillway fr the dam prpsed. a. Safety cnsideratins cnsistent with ecnmy: Key Wrds: Cmpsite dam, Ogee Spillway, Spillway prfile, Safety against sliding, Trajectry bucket. 1.INTRODUCTION Pambar river basin is faced with severe drught situatin during summer seasn when the crps grwn in Kanthallr village need water fr irrigatin. The sil is highly fertile fr paddy, sugarcane, vegetables and varieties f fruits. In rder t cater t the irrigatin needs, the pssible slutin in this catchment is t stre water during the mnsn mnths and als t facilitate fr strage f water frm rainfall received during summer. This cncept lead t the prpsal f cnstructin f dam at Kanthallr. Spillway is ne f the mst imprtant cmpnent f a dam. Many failures f dams have been reprted due t inadequate capacity r imprper design f spillway, especially fr earthen and rckfill type dams which are likely t be destryed,if vertpped,unlike cncrete Many failures f dams have resulted frm imprperly designed spillway r spillways f inadequate capacity. Prperly designed structure f adequate capacity may be fund t be nly mderately higher in cst than a structure f inadequate capacity. b. Hydrlgical and site cnditins: The spillway design and its capacity depend n Inflw discharge, its frequency, and shape f hydrgraph Height f dam Gelgical and ther site cnditins Imprtant tpgraphical features, which affect spillways design, are Steepness f terrain Amunt f excavatin and pssibility f its use as embankment material. The pssibility f scur Stability f slpes, safe bearing capacity f sils. Permeability f sils. 2016, IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2557

2 Vlume: 03 Issue: 04 April p-issn: c. Type f Dam The type f dam influences the design fld and spillway. Fr earth and rckfill dam gee r chute spillway is preferred. 3. DESIGN OF SPILLWAY Full Reservir Level (FRL) = M Maximum Water Level (MWL)= M Height f Dam=23 m Tp Level= M Crest Level= M Deepest rck level= M Therefre, Head = MWL Crest level = = 4.00 m Maximum fld discharge = m 3 /sec H d (design head) = (IS: ) = 3.6 m P/ H d = (spillway crest level deepest level)/ H d = ( ) = m > Upstream prfile u/s quadrant f the crest may cnfirm t ellipse X 12 /A Y 12 /B 1 2 =1 (IS: 6934, cl ) Fr P/H d > 2, A 1/H d = 0.28 (frm fig 2, IS 6934) B 1/H d = Where, P= height f spillway crest frm river bed H d = Design head A 1 = 0.28 H d = =1.008 m B 1 = = m Therefre, X 12 /A Y 12 /B 2 1 =1 X 12 / (1.008) 2 + Y 12 /(0.5904) 2 = 1 X 12 = {1- Y 1/(0.5904) 2 } X 2 1 = Y 2 1 Table -1: Upstream prfile c-rdinates Y 1 X Dwnstream prfile d/s prfile f the crest may cnfirm t the equatin IS: 6934, cl X = K 2 H 0.85 d Y , IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2558

3 Vlume: 03 Issue: 04 April p-issn: K 2 = 2 (IS 6934, FIG 2) P/H d = > 2 Therefre, X = Y 2 X 2= 2.62 Y Table -2: Dwnstream prfile c-rdinates Y 2 X Figure 1: Upstream prfile 3.3 Tangent pint X = 2.62Y dx/dy = Y = Y Adpt a slpe f 0.75 (slpe varies frm 0.7:1 t 0.8:1) 0.75= dx/dy = Y Figure 2: Dwnstream prfile Y = /0.75 Y = At tangent pint, Y 2 = m X 2 = = m 2016, IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2559

4 Vlume: 03 Issue: 04 April p-issn: Table-3: Frces and Mments Figure 3: Spillway Prfile 3.4 Cmputatin f frces and mments The entire area f spillway prfile was divide int rectangles and triangles numbered frm 1 t 38. Vertical frce = Area x Unit weight f cncrete Mment = Frce x Lever arm 3.5 Water Pressure At MWL all shutters will be pen. Hence the water abve crest i.e, at t MWL(1582) will flw ver the crest. 2016, IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2560

5 Vlume: 03 Issue: 04 April p-issn: Hence, the pressure develped abve the crest will be wh i.e, wh= 1 ( )= 4 Pressure diagram will be rectangle frm base t crest level and triangle frm base f dam up t MWL. a) Water at MWL Table- 4: Frces and Mments Descriptin Frce, KN Lever Arm Mment, KNm Rectangle Triangle Ttal Silt pressure( IS ) Bed level= Silt height is taken as 2m As per IS vertical pressure, r s = =0.925 t/m 3 Hrizntal pressure, r s = =0.36 t/m 3 Vertical frce = 1/ = t Hrizntal frce = /2 = 0.72 t Table-8: Lads/mments at base f te Descriptin Frce, t Lever Arm Mment, tm Vertical b) Water at FRL Shutter clsed Hrizntal Table- 5: Frces and Mments Descriptin Frce, KN Lever Arm Mment, KNm Triangle Uplift Pressure a) Water at MWL Table- 6: Frces and Mments Frce Lever arm Mment, tnne b) Water at FRL Table- 7: Frces and Mments Frce Lever arm Mment, tnne Weight f water Lads/mments f base f te due t water a) Water at MWL Table- 9: Frces and Mments Descriptin Frce, t Lever Arm Mment, tm Rectangle Triangle b) Water at FRL Table- 10: Frces and Mments Descriptin Frce, t Lever Arm Rectangle Mment, tm Triangle , IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2561

6 Vlume: 03 Issue: 04 April p-issn: L O A D 3.9 Lad cmbinatin DESCRIPTION H V M 0 M x A area under cnsideratin F ɸ partial safety factr f reactin F c partial safety factr f chesin P ttal hrizntal frce A Weight f structure B Weight f structure COMBINATION B F = ((w - u) tan ɸ / F ɸ + C A / F c) / P F = ((( ) tan25 ) / / 4.5 ) / Water pressure Uplift pressure Silt pressure Water lad = 2.1 kn>1 Hence safe COMBINATION C F = ((w u ) tan ɸ / F ɸ + C A / F c ) / P = ((( ) tan25 ) / / 4.5 ) / = 2.17 kn>1 Hence safe C Weight f structure Water pressure Uplift pressure HYDRAULIC DESIGN OF TRAJECTORY BUCKET TYPE ENERGY DISSIPATOR ( IS 7365:2010) a) Bucket shape Fr practical cnsideratin, a circular shape f trajectry bucket is prpsed fr the design. Silt pressure Water lad b)bucket invert elevatin Available data Ttal discharge = 88 m 3 /s H- Hrizntal Frce M verturning mment V- Vertical Frce M x resisting mment 3.10 Check fr sliding Factr f safety against sliding F = ((w-u) tan ɸ /F ɸ + CA/F c)/p w ttal mass f dam u ttal uplift pressure tan ɸ cefficient f internal frictin ɸ= 25 Width f bucket = 10 m Max. reservir pl elevatin = 1582 m Crest level f spillway = 1578 m Max. tail water level = 1562 m S assume bucket invert elevatin = m c) Radius f bucket H 1 = reservir pl elevatin bucket invert elevatin = = m 2016, IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2562

7 Vlume: 03 Issue: 04 April p-issn: H = reservir pl elevatin crest level = = 4 m H 5 = reservir pl elevatin jet surface elevatin = = As per IS 7365: 2010 cl: Radius f bucket = 0.6 t 0.8(H.H 5) 0.5 = 0.6 t 0.8(4 x 18.44) 0.5 = 5.15 t 6.87 Prvide radius f bucket as R = 6.00 m d) Lip elevatin and exit angle In rder t minimize the sub-atmspheric pressure n lip prvide a lip angle f 30 R R cs ϕ = 6 6 cs (30) f) Estimatin f scur dwnstream f spillway ( IS 7365:2010) Depth f scur, d s = m (q H a ) 0.5 m = 0.36 (minimum expected scur) q = 17.9 m 3 /s H 4 = reservir pl elevatin bucket lip level = = m Therefre d s = 0.36 ( ) 0.5 = 6.58 m g) The shape and width f lip As per IS 7365:2010,cl ,width f lip is prvided 1/10 f radius f bucket. 6/10 = 0.6 m = S lip level = = m Therefre tail water level is lwer than lip level. Lip shall be made flat. (As per IS 7385:2010, cl:5.2.4) e) Trajectry length Actual velcity f jet at lip f bucket V a = m/s ɣ= Lip level Tail water level = = m H γ = V a2 /2g = / = m X/H γ = sin 2ϕ + 2 cs ϕ sin 2 ϕ+ ɣ/h ɣ X/ = sin cs30 sin (1.304/14.574) X = m Vertical distance f thrw as per IS 7365 cl a= V 2 a sin 2 ϕ /(2g) = sin 2 30/ (2 9.81) = 3.64 m Figure 4: Trajectry Bucket 5. CONCLUSIONS The verflw sectin f the dam is f cncrete where spillway is lcated. S the design f the spillway f cmpsite dam was based n the spillway design criteria f a gravity dam. Ogee type spillway was adpted because f high discharging efficiency. Fr energy dissipatin and the preventin f dwnstream scur, trajectry bucket is als included in the design. REFERENCES [1] IS 6934:1998, Hydraulic design f high gee verflw spillways- Recmmendatins [2] IS 7365:2010, Criteria fr hydraulic design f bucket type energy dissipatrs 2016, IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2563

8 Vlume: 03 Issue: 04 April p-issn: [3] IS 10137:1982, Guidelines fr selectin f spillways and energy dissipatrs [4] IS 6512:1984, Criteria fr design f slid gravity dams [5] United States Bureau f Reclamatin, Design f small dams [6] Dr. P N Mdi, Irrigatin and water pwer engineering [7] S K Garg, Irrigatin engineering and hydraulic structures BIOGRAPHIES 1 B Tech Graduate, Civil Engineering Department, Mar Athanasius Cllege f Engineering, Kthamangalam, Kerala, India, mail2arunjji@gmail.cm 2 B Tech Graduate, Civil Engineering Department, Mar Athanasius Cllege f Engineering, Kthamangalam, Kerala, India, nithyamarythmas@gmail.cm 3 B Tech Graduate, Civil Engineering Department, Mar Athanasius Cllege f Engineering, Kthamangalam, Kerala, India, reshma.k.jse@gmail.cm 4 B Tech Graduate, Civil Engineering Department, Mar Athanasius Cllege f Engineering, Kthamangalam, Kerala, India, yapung2010@gmail.cm 5 Prfessr, Civil Engineering Department, Mar Athanasius Cllege f Engineering, Kthamangalam, Kerala, India, sllygerge@mace.ac.in 2016, IRJET Impact Factr value: 4.45 ISO 9001:2008 Certified Jurnal Page 2564