Wave Transmission on Submerged Breakwater with Interlocking D-Block Armor

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1 International Referee Journal of Engineering an Science (IRJES) ISSN (Online) X, (Print) Volume 4, Issue 6 (June 2015), PP Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor Hamani 1, Bambang Trihatmojo 2, Suharyanyo 3 1 Post-grauate stuent at the Faculty of Civil Engineering, Diponegoro University, 2 Civil Engineering Gajah Maa University, 3 Civil Engineering Diponegoro University ABSTRACT:- Breakwater is a construction to reuce the effect of ocean wave that causes erosion/abrasion in coastal areas. The stuy is aime at etermining the stability of the interlocking D-block armor in breakwater. Laboratory experiment to confirm the finings uses variations of water epth, (), wave perio(t), topwith(b) an thewave height(h). The breakwater type use in this researchis the submerge breakwater with the interlocking D-block armor that results in regular waves in the 2D glass channel (waveflame). To etermine the parameters that influence the transmission wave, the breakwater here is esigne to represent actual behaviors. Observations an measurements in the stuy was the effect of wave height(h), wave perio(t) before an after passing the breakwater structure in the wave channel. Results show that wave transmission through the breakwater structureis strongly influence by the water level above the top(h), structural height(-h) an water epth() as well as the ratio of wave steepness Hi gt 2 with regression parameter obtaining the formula for transmission coefficient of Kt = 1, ,012 ( gt 2 B )-1,376( h)- 1,970 Hi gt 2. Results also inicate that the higher the structure above water top(h), the bigger the transmission coefficient is, an the lower the value(h, the smaller the transmission coefficient. The parameters above top height(h) an top with(b) greatly affect the transmission coefficient(kt) an breakwater performance in reucing wave height. Keywors:- breakwater, transmission coefficient(kt), interlocking D-block I. INTRODUCTION Inonesia is an archipelago with the secon longest shoreline in the worl. This shoreline also provies livelihoo for many of its citizens. Therefore, the nee for a efense against erosion/abrasion of the shoreline is of utmost importance. This significant efense against waves requires the proper techniques to minimize risks of erosion/abrasion. Breakwater is an off-shore construction esigne to break incoming waves into smaller waves. Base on its relative position to sea level, three types of breakwater are available: conventional breakwater, lower limit breakwater, an submerge breakwater. They are epicte in Fig Figure 1.1 Conventional (A), lower limit, (B), an submerge breakwater (C). 35 Page

2 Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor This research is aime at unerstaning the wave transmission on the breakwater structure that uses Interlocking D-block layer. Interlocking D-Blok layer is a concrete protective layer that interlocks to improve the stability of the armor units of the breakwater. No earlier stuy has reporte the use of interlocking D-block as the layer for breakwater. The avantages of interlocking D-block over available armors are: - The stacking is in an orerly manner, in contrast to the current ranom placement of armor units. - Stability at each armor unit oes not epen on the weight of the unit. - It has higher stability as it has better homogeneity. - Unit weight is lower in its usage. - It is environmentally frienly as it is well-stacke an is porous. - The construction costs are more efficient. An the isavantages inclue: - The installation can be quite a challenge as they must be stacke orerly. - It is mostly suitable for beaches with relatively flat bathymetry an high erosion/abrasion levels. - It therefore not suitable for steep, muy, an rocky beaches as they hamper proper installation of the breakwater. 1. Theory 1.1 Wave Characteristic Ocean wave has some categories epening on the force that causes it, an it can be enigmatic for coastal engineers. Shore erosion/abrasion is becoming serious nowaays as it enangers people, properties, an natural resources, an also commercial activities own the shores. The wave theories commonly use to explain the working of ocean wave are, among other things: The Airy wave theory The Stokes theory The Coniial theory The Solitary theory The parameters commonly use to explain ocean wave are: Wave perio (T); the time it takes for two wave peaks to travel certain points. Wavelength (L); the horizontal istance of two wave peaks. Wave velocity (C); the ratio of wavelength an wave perio. Amplitue (a); the istance of a wave peak or a wave valley to the water level (H/2). 1.2 The Airy Wave Theory It is also known as the small amplitue wave theory or linear wave theory. Airy (1845) evelope an approach for the wave movement by escribing it in a simple way or sinusoial. This theory is base on the equations of continuity an momentum conservation put forwar by Laplace an Bernoulli. This theory applies for a wave where H < an H < L. The equation for the wave front is: = cos (kx - t) Where : = wave amplitue (aroun half the wave height) k = wave number (2 π/l) = 2 π/t (wave frequency) For shallow waters, /L < 1/120 Wave velocity : C = L = g T wavelength : L = CT = T g Horizontal particle velocity : = H g cos[kx t] 2 Vertical particle velocity : w = πh T (1 + 2 )sin[kx t] 36 Page

3 For meium waters, 1/120 </L< ½ Wave velocity: C = L = g.tanh k T Wavelength: L = tanh. k 2π Horizontal particle velocity : = H 2. gt cos h [k(z + )]. cos[kx t] L Cosh K Vertical particle velocity : Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor w = H 2. gt L sin h [k(z + )]. sin[kx t] Cosh K For eep waters, /L < ½ Wave velocity: C = L = T 2π Wavelength: L = =1,56 T2 2π Horizontal particle velocity: = πh T ekz cos[kx t] Vertical particle velocity: w = πh T ekz sin[kx t] Measurements of wave height in the laboratory use the followings: Hi = Hr = Ht = Hmaks +Hmin 2 Hmaks +Hmin 2 Hmaks t+ Hmin t Wave Transmission The ratio of incoming wave (Hi) reflecte by the breakwater is state as the transmission coefficient (Kt) as follow: Kt = Ht Hi This research is foune on earlier research on breakwater, incluing: Sila D-arma (1994) foun the wave transmission coefficient for artificial reef: Kt = exp [ Ln ( h Hi )-1.32( B ) Armono (2004) gaine the formula for transmission coefficient (Kt) from submerge Breakwater mae of hollow hemispherical shape of artificial reef (HSAR): Kt = 1,616-31,322. Hi -1,099 h + 0,265h B Seeling (1980) got the formula for transmission coefficient from the effect of breakwater on the wave transmission of Rabble Moun Breakwater: Kt 0 = C (1 - F ) not submerge Ru Kt 0 = C (1 - F Ru where: F Ru < 0, C = 0.24 ) C (1 - F Ru ) submerge where: F = Freeboar R = Run up Kt 0 = Transmission coefficient 37 Page

4 Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor II. METHODOLOGY This research was carrie out at Balai Pantai, Gilimanuk Singaraja street km. 122 Gekayak Bali using 2D wave tunnel of 40 m height, 60 cm with, an 110 cm length, an a wave maker to vary the perio an height. An each set of the sensor is equippe with 4 wave probes to measure wave height, both in front of an behin the structure. The measurement result is save using the HR Dag Suite software as epicte in the following figure: Figure 3.1. Wave probes connecte to a computer. Figure 3.2. Wave probe instrument calibration. The breakwater moel is mae of concrete. An its imension is as follow: Concrete specific weight = 2000 t/m 3, V=B 2 xe Figure 3.3. Interlocking D-block, Scale 1: Page

5 Details of the moeling are epicte below: Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor Figure 3.4a. Moel of D-BI scenario Figure 3.4b. Moel of D-BI scenario Figure 3.4c. Moel of D-BI scenario Figure 3.5. Moel position before running. 39 Page

6 Kt Kt Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor Structure parameter variation is base on the ratio of structure height (-h) an water epth (), for h = 0.65, 0.79, 0.88 an 1.0. Wave parameter variation base on perio (T) with Stroke (S) T=1.6. Stroke (C) T=2.0. Stroke (B) T=2.5. Stroke (A) for each h, a running of 15 times ensues.to figure out the effect of topwith (B) on transmission, the top with (B) is mae into three variations; B=0.50, 0.80 an 1.15 cm with the fixe structure height (-h). the h III. RESULT AND DISCUSSION The effect of breakwater height (-h) on water epth () in Kt vs Hi, can be seen in Fig.4.6. The greater Hi, the less the transmission coefficient (Kt) is. An the smaller the, the higher the transmission coefficient will be. They are epicte in the following(4.6,4.7,4.8) figures Kt vs Hi/ paa (-h)/b 0, Hi/ Figure 4.6.The relationship of Hi/gT 2 an transmission coefficient Kt in B 50 D-BI. Kt vs Hi/ paa (-h)/b 0, Hi/ Figure 4.7. The relationship of Hi/gT 2 an transmission coefficient Kt in B 80 D-BI 40 Page

7 Kt Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor Figure 4.8.The relationship of Hi/gT 2 with transmission coefficient Kt in B 115 D-BI Base on figures 4.6, 4.7, 4.8, it can be inferre that the effect of wave steepness Hi as a horizontal variable an the transmission coefficient as the vertical variable is; the higher the value of Hi, the lower the transmission coefficient is. Therefore, wave transmission is influence by the height of breakwater (-h), water epth (), an wave steepness ( Hi ), wavelength () an top with (B). This can be mathematically written as: Kt = Ht = f = Hi (, h, Hi ) B An a multi parameter regression results in: Kt = ( Hi ) ( h) ( B Comparison with Earlier Research 1. Armono HD (2004) Kt vs Hi/ paa (-h)/b 0, Hi/ ). Figure 4.9.The relationship ofk T an Hi gt 2 inh (Armono, 2004) 41 Page

8 Kt Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor Kt vs Hi/gT 2 paa (-h)/b 0, Figure The relationship ofk T an Hi gt 2in h B B 0.32 Hi/gT 2 2. Seeling (1980) Figure 4.11.Transmission coefficient of submerge breakwater (Seeling, 1980) Kt y = 100.9x x R² = h/ = 0, Hi/gT 2 Figure The relationship of Hi/gT 2 an Kt in B=50 (=0,47) 42 Page

9 Kt 3. Sila D-arma, IGB, (1994) Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor Figure The relationship ofk T an h h by Sila D-arma Kt vs h/(-h) paa B 0,8 Figure The relationship ofk T an h h B 0.8 m T 1,6 T 2,0 T 2, h/(-h) Comparisons with earlier results also reveal the same behavior that bigger value of Hi transmission coefficient. results in lower IV. CONCLUSION Results on the research on wave transmission coefficient (Kt) in the breakwater structure that uses interlocking D-block show that: The most influential parameters on the wave transmission for submerge breakwater that uses interlocking D-block are; structure height (-h) compare to water epth (), wave length (gt 2 ) compare to top with (B), an the wave steepness Hi. An the resulting formula for transmission coefficient (Kt) with the multi parameter regression analysis is: Kt = ,012 ( Hi ) ( h) ( ) B This result can further be use in consiering the use of interlocking D-block as armors for breakwater. 43 Page

10 Wave Transmission on Submerge Breakwater with Interlocking D-Block Armor BIBLIOGRAPHY [1]. Armono, HD. An Hall, K.R., 2003, Wave Transmission on submerge Breakwater Mae of Hollow Hemispherical Shape Artificial reef, 1 st Coastal Estuary an Offshore Engineering Specialty Conference of the Canaian Society for Civil Engineering (4 7 Juni 2003), Moncton Canaa. [2]. BambangTriatmojo, 1999, Teknik Pantai, Beta Offset, Yogyakarta. [3]. D angremon, K., Van er Meer, J.W., an e Jong, R.J., 1995, Wave Meaurement an Analysis, San Fransisco, USA. [4]. Dean, Robert G. An Dalrymple, Robert A., 1984, Water Wave Mechanics for Engineers an Schaintists (Avances Series on Ocean Engineering Volume 2), Prentice Hall,Inc. [5]. Dean, Robert G. An Dalrymple, Robert A., 2004, Coastal Processes with Coastal Engineering Applications, Cambrige University Press, Cambrige, Unite Kingom. [6]. NurYuwono, 1992, Dasar-asarPerencanaanBangunan Pantai, Lab HiraulikanHirologi, Pau IT UGM, Yogyakarta. [7]. NurYuwono, 1992, PeomanTeknikPerencanaanpantaiBuatan (San Nourishment), Lab HiraulikanHirologi, Pau IT UGM, Yogyakarta. [8]. Paotonan, c., NurYuwono, Raiantatriatmaja, anbambangtriatmojo, 2011, Two Dimensional Physical Moeling of Seiment Loss Through a Submerge Coastal Structure, Proceeings : International Seminar on Water Relate Risk Management, HATHI, Jakarta. [9]. Sila D-arma, I GustiBagus, 1994, UnjukKerjaTerumbuKarangBuatan (Artificial Reef) sebagaipereamenergigelombang, Thesis S-2, UniversitasGajahMaa, Yogyakarta. [10]. Van er Meer, J.W & I.F.R Daement. 1994, Stability an wave transmission at low Creste Rubble- Mpun Structures. J. Waterway, Port, Coastal, an Ocean Engineering, 120(1): 1-19 [11]. Van er Meer,J.W. 1988, Stability of Cubes, Tetrapos an Accropoe. Breakwater 88. Ithomas Limite, Lonon p24: [12]. Goa, Y., Re-Analysis of Laboratory Data on Wave Transmission Over Breakwater, Rep. Port harbor, res. Inst. 44 Page