Twin-Wing Tsunami Barrier

Transcription

1 Twin-Wing Tsunami Barrier Developed in the Dutch Water Tradition Award with: the Wall Street Journal Technology Innovation Award 2012 the Silver Edison Award 2013 Technical Descrip/on 1

2 Content Introduction Objective The ultimate solution Company biography pag What is a tsunami? Negative tsunami wave Positive tsunami wave 3. The Twin-Wing Tsunami Barrier Elimination of the negative tsunami wave Reflection of the positive tsunami wave Coastal protection Construction Barrier Walls Foundation Sea bottom conditions Bottom protection Construction cost estimated Patent Contact information Introduction 2

3 The devastations caused by tsunamis in densely populated and industrial coastal regions have been widely documented and their effects witnessed by horrific experiences like in Asia in 2004 and more recently in Japan in On 26th December 2004 a seaquake of the magnitude of 9.3 on the Richter scale, shook the north part of Sumatra in the Indian Ocean at a depth of about 5 km. Distribution of seaquakes off the coast of Sumatra On March 11, 2011 Japan was hit by a tsunami which was triggered by a 9.1 force seaquake at some distance off the coast of Sendai. Distribution of seaquakes off the coast of Japan Objective 3

4 The increasing incidence and frequency of tsunami events, particularly around the Pacific Rim, triggered an urgent need to respond to the challenge of developing a barrier capable to disrupt and neutralise the overwhelming power of a tsunami wave. The objective was to design an innovative barrier to break down the mass of the wave, to neutralise its energy and prevent it from reaching residential and industrial coastal areas, without disturbing shipping or marine life. The ultimate solution After several years of testing, the Twin-Wing Tsunami Barrier could be given full approval to be constructed in any designated tsunami prone area with a rather flat coastal sea bottom. Initially lying passively on the sea bed, it is instantly activated by the approaching water surge of the tsunami wave and is automatically deployed to offer large scale coastal protection. Operating independently from coastal warning systems, it can be positioned across a bay shape or along a coastal stretch. It should be stressed that in its passive resting position it does not interrupt shipping nor marine life. The Twin-Wing Tsunami Barrier has been designed by Van den Noort Innovations BV in the Netherlands. Research and development took several years whilst extensive testing was undertaken by three groups of students and their professors in a water laboratory at the Zuyd-University in Heerlen, in The Netherlands. Leading professor was ir. Bas Ziekenheiner, master of civil engineering. 1.1 Company Biography Van den Noort Innovations BV is an innovative engineering company with a specialist remit to make water related, 'state of the art' inventions their sole business activity in the field of civil technical systems engineering. All inventions are water related and stem from advanced understanding of the water behaviour under critical conditions, with the focus to ensure efficient, environmentally friendly and cost effective solutions. Over the years Van den Noort developed a unique expertise to bring state of the art engineering inventions to market, in collaboration with strategic partners to represent, promote and/or build their stand alone devices like the much acclaimed and awarded Self Closing Flood Barrier (SCFB), the Oil Recovery Vessel, the Floating Rotating Airport, the Water Turbine and most recently the TwinWingTsunami Barrier (see 2. What is a Tsunami? 4

5 A tsunami is a series of rapidly travelling energetic waves generated by sea quakes, volcanic eruptions or massive sub aerial or submarine landslides. In the depths of the ocean, tsunami waves do not dramatically increase in height until they reach the coastline and travel inland getting their energy once more boosted from the diminishing width between the sea level and the uprising sea bottom. The potential energy in the vertical water column on top of the rupture location is then transferred into a horizontal propagation of tsunami waves. Irrespective of their cause, tsunami waves radiate in all directions within minutes. The original tsunami can be described as a direct local wave heading for the nearest coast and a distancial wave that radiates out from the disturbance zone in the deep ocean to travel for thousands of kilometres. The wave magnitude and height of the tsunami at its point of origin is related to the inclination of the fault plane and the degree of vertical displacement of the fault. Depending on the character and magnitude of the oceanic rupture, deep ocean tsunamis travel at a speed of up to 900 km per hour. The local ones slow down to approximately km per hour in shallow waters. In deep water the tsunami is hardly noticeable, but once it starts to run up on the rising sea bottom as it approaches shallow water, the waves dramatically build up in height. Local tsunamis usually arrive too quickly for any formal warning system to be effective. The treacherous December 2004 tsunami in the eastern part of the Indian Ocean struck like a giant breaking surf wave with a peak preceded by a trough or valley known as a negative tsunami wave. A positive tsunami wave type, such as occurred in the Central and Western part of the Indian Ocean, rushed in like a strong and fast moving tide current with a rapidly rising sea level. In both cases, part of the tsunami s energy was reflected back into the open sea after its coastal run-up. The tsunami is a comprehensive phenomenon, which is characterised by its sequence in secondary and tertiary waves, and by its intermediate back and forth rolling waves parallel to the shore line. The first tsunami wave may not always be the largest or strongest in sequence and it is often followed by stronger waves with an even greater destructive power. 2.1 Negative tsunami wave This series of illustrations represent the sequence of a negative tsunami wave build up on the rising sea bed. 1. The front of the tsunami wave meets resistance from the rising sea bottom and vigorously slows down in speed 5

6 2. The retreating water mass is moving at full speed with the effect of pushing the water mass up 3 Pushed by its rear end rolling in onto the shallow coast, the wave rapidly builds up in height approaches the like a wall of water causing massive devastation, particularly to vulnerable costal areas. 4. The wave now builds like a gigantic surf wave from the retreating water mass 5. Once the wave approaches the coast, it rushes in like a wall of water causing massive devastations particularly in vulnerable coastal areas 2.2. Positive tsunami wave The positive tsunami wave is a constantly moving positive volume of water. The positive wave does not build up like a breaker wave. Instead it looks like an upcoming tidal wave and overflows the shore in a continuous stream. At some distance from the shore line, at a depth of some 10 metres, the wave height is only approximately 1,5 metres. 6

7 A positive wave approaching the coast 3. Twin-Wing Tsunami Barrier The Twin-Wing Tsunami Barrier has been developed in order to disrupt and neutralise a tsunami flood wave, in both its negative and positive occurrence. 1. In its resting position, the barrier wings are positioned horizontally on the sea bed, ready to swing up like a wall from their piled foundations as soon as the coastal waters retreat (negative tsunami) or, from the occurrence of a direct positive tsunami wave hit. 2. On either side of the foundation, the barrier wing through its spoiler is instantly pushed up into a vertical position once a strong upcoming onshore or offshore ground stream starts to emerge. During normal flood and even high tides, the wings always remain in their horizontal positions. Should a negative tsunami wave strike, the barrier wing on the shore side is swung into its 7

8 vertical position and it closes off the shore water effectively barring the flood wave. 3. In a positive tsunami run, the wave will be reflected back to the ocean by the diffuser on top of the barrier wing. However, when there will be an overflow of flood water surging towards the shore, the speed of its movement will be greatly impaired by the unmoved coastal water mass which has been blocked by the barrier. The wave impact is thereby neutralised by the stalled coastal water body. Through their hinges, the barrier wings can swing back and forth from their horizontal positions into a vertical position, staying in place like a sluice gate and picking up the impact of secondary waves. 8

9 3.1 Elimination of the negative wave The negative tsunami (1) is characterised by a wave valley. The volume of water is pulled from the coast and joins into the positive tsunami wave (2). Through its additional water volume the positive wave builds up in height. With the negative tsunami wing in vertical position the positive tsunami does not build up by the volume of the negative wave. Now, the positive tsunami will be much lower in height (3). This graph demonstrates the tsunami wave phases. Graphic of the tsunami in the Bay of Nai Harn, Thailand - December 2004 The data illustrated in the above graph shows the situation in the water at a distance of ca. 1,500 metres from the coast line with a water depth of 11.7 m. Without a tsunami barrier the water depth would drop down to 9.0 m during the negative tsunami wave and would rise more than 6.2 m up to 15.2m during the positive wave (see red line). The volume of water in ① is 9,210 m³/m. The volume of water in ② is 13,518 m³/m. In a situation where a Twin-Wing Tsunami Barrier is installed the coastal water would be blocked to ensure little water displacement. The positive wave (green line) would rise up to a maximum of 13.0 m an increase of 1.2 m. The volume ③ of the lower positive wave is 6,771 m³/m (26.5% less than without the barrier). 3.2 Reflection of the positive tsunami wave The lower tsunami wave has much less volume in itself. The speed and length of the wave remain the same. When the positive wave reaches the barrier it will swing up and the water will be reflected back over the top of the Barrier. The same reflection process would occur like an incoming tsunami wave reaches a high cliff face. Conclusion: No matter whether an upcoming negative or positive tsunami wave is striking, the Barrier will automatically block either wave through its upswinging wings to protect they hinterland 9

10 4. Coastal protection In many places around the world, the most populated areas are situated along the coast squatted with urban villages, towns and cities built around the delta areas of rivers. As the illustration below shows, such areas can be effectively protected through the Twin-Wing Tsunami Barrier spanning the estuary opening. Example of coastal protection. The city of Minamisanrika in Japan has been totally destroyed by the tsunami in January By spanning the inlet by the Twin-Wing Barrier, this city can be well protected from future tsunamis. Under normal conditions, the city remains in open reach to all marine traffic from the sea. (The red line indicates the recommended Barrier location). 10

11 5. Construction The Twin-Wing Tsunami Barrier requires a solid foundation to be secured in the ocean floor. This construction occurs in a number of phases (see ). It is essential that a concrete foundation is fixed to the ocean floor. The barrier wings are constructed from steel. The whole construction should be installed at an optimal depth of 10 metres. It is flexible enough to be constructed on a sandy or even a rather flat rocky bottom. Under normal tidal conditions the barrier built on the sea bed is totally invisible and does not disrupt marine life nor shipping. The Twin-Wing Tsunami Barrier as strong as a cliff face 5.1 The Barrier Wings The Twin-Wing Tsunami Barrier is equipped with two wings which are independently activated depending upon the type of a negative or a positive tsunami wave acting on them. The smaller barrier wing protects against the negative tsunami and is located on the shore side, whilst the larger wing is activated by a positive tsunami wave and is located at the opposite side. In non-critical conditions, the wings remain at rest on rubber buffers attached horizontally across the foundation plate. The wings are hinged to the foundation plate. Both wings are equipped with a spoiler to be pushed up into a vertical position once a tsunami wave approaches. The negative wing swings up once the tsunami pulls the water away from the shore. In this upright position, the barrier acts to prevent the water from flowing out to sea. The positive wing is pushed up once the positive tsunami wave reaches the barrier acting as its diffuser and reflecting the upcoming water back into the ocean. 11

12 The two barrier wings in vertical position The wings are prefabricated from steel. Their strong construction is entirely capable to withstand the tremendous forces of the oncoming tsunami waves. The wings are reinforced by vertical and horizontal ribs inside the steel casing. The space between the ribs is filled up with foam impervious to water. In order to keep the wings in a horizontal position on the foundation plate, they are both balanced by concrete weights. Once either wing is activated by an incoming tsunami, their swing into an upright position is protected by the support block and rubber buffers anchored to the foundation at their base and, by the addition of strong anchor cables connected by eyes that are mounted on reinforced plates. On top of the positive barrier a diffuser mounted on hinges acts to reflect the tsunami wave back to the ocean 5.2. Foundation The foundation is a pre-fabricated combination of steel-, pile- and caisson made in 24 metre runs of high volume concrete of 30 metres wide, in a height of 2.5 metres. The elements are sunk into the ocean floor to a depth of 1.5 metres. A 2 metres high caisson contains the natural ballast in the middle of the foundation. The foundation elements are set in steel and containing the four steel foundation push and pull piles, at an angle of 75 degrees in the transverse direction. The foundation piles are hollow tubes filled and top finished with concrete. Together with the weight in the caisson, the total weight of the elements, its width and foundation piles ensure the wings to remain in a horizontal position without turning over. 12

13 5.3 Sea floor conditions The foundation of the Twin-Wing Tsunami Barrier must be laid at a depth of about 10 metres (high water spring tide). In case there is no sand bedding or in case of a rough floor, a sandbank of a minimum thickness of 5 metres is required to obtain an equal level foundation. Examples of sea bottom improvement by sand supply. 5.4 Sea bottom protection It is recommended that a protecting layer of asphalt be used to prevent the erosion of the sand bottom at both the shore and the offshore side of the Barrier. 5.5 Construction cost estimated The estimated cost of construction may vary from location to location depending on the characteristics of the sea bottom and the spanning width of the Barrier; A safe estimated will run between $50,000 and $70,000 per metre. Prior to its construction it is imperative to undertake a research study of its vary sea bed. 6. Patent The Twin-Wing Tsunami Barrier has been patented under PCT nl2012/

14 7. Contact information: Van den Noort Innovations BV Zilverschoon HE Kampen, The Netherlands t: +31 (0) m: +31 (0) e: info@noort-innovations.nl w: Registration No: Engineering Inventions: focusing men environment...future 14