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Collaborating Authors
Experimental Study On the Artificial Beach Stability Under the Action of Wave
Lian-cheng, Sun (Tianjin Research Institute for Water Transportation, Ministry of Communications, Key Laboratory of Engineering Sediment of the Ministry of Communications) | Feng, Gao (Tianjin Research Institute for Water Transportation, Ministry of Communications, Key Laboratory of Engineering Sediment of the Ministry of Communications) | Ting, Xu (Tianjin Research Institute for Water Transportation, Ministry of Communications, Key Laboratory of Engineering Sediment of the Ministry of Communications) | Yi-feng, Huang (College of Water Conservancy, Changsha University of Science & Technology)
ABSTRACT: Based on the design of artificial beach, the artificial beach erosion stability experiments was test in the flume with different particle sizes of sediment and different wave factor value. This paper put forward the erosion area, loss and particle size of the beach under the action of different wave conditions, provide scientific basis for the construction of artificial beach. INTRODUCTION A site for artificial beach project is located in Tianjin Dongjiang Port. The artificial beach planned for the use of water recreation is going to be protected by the double-arc breakwater as shown in Fig.1. As there might be artificial beach erosion due to wave actions with tide after the project, it is necessary to carry out a physical model test to investigate the sediment motion under the action of waves. For the physical model test we introduced a 2D flume with two different sand sources based on similarity criterion. Flume test will be made on the beach profile under different wave conditions with normal and extreme cases). In order to determine the stable profile of the beach, a series of flume test were analyzed and discussed. EXPERIMENTAL CONDITION Selection of the prototype sand The sands for the flume test are taken from the actual beach and classified into 3 prototypes form coarse to fine (CS, FMS, FMS). Determination of the Wave factors For the physical model test the ordinary large wave and storm wave were adapted for a year and 50-year return period, respectively. 50-year return period wave factors. Select from the project closer to near-3m wave contour corresponding to a 50-year return period wave elements Ordinary wave. Ordinary waves direction is ESE~S, S at the most. In summer the main strong wave direction is NNW~E, Ordinary waves direction is ESE~SSW, the most.
- Research Report > New Finding (0.51)
- Research Report > Experimental Study (0.51)
ABSTRACT: The nonlinear shallow water equation is used for simulate the wave run-up on Phuket beaches due to the 2004 Indian Ocean Tsunami. Compared with field survey reported and data published in the literatures, the results of the developed numerical model shows good agreement in wave run-up heights, wave velocity, and inundation distances. INTRODUCTION In December 26, 2004, an earthquake on the Richter scale of 9.3 occurred in the Indian Ocean off the west coast of Northern Sumatra near the Aceh province, Indonesia. Tsunami waves were generated and attacked the villages and resorts along shorelines of many countries including Thailand. Field data of wave characteristics and damage were collected by many governmental and private agencies. Siripong et al. (2005) analyzed recorded water levels from 7 gauging stations along the Andaman coast of Thailand as shown in Fig. 1. They found that those waves propagated to the gauging stations with trough leading, which was called as "N wave" type. However, before attack shoreline, the crest or trough of wave varies depending on the bathymetry of the region, displacement of the ocean floor, etc. In their report, details of the flooding areas along 6 provinces in Thailand were presented. Maximum tsunami water levels are summarized in Table 1. Grilli, et al. (2005) also collected field data of tsunami run-up along the Andaman coast of Thailand and collected data are shown in Fig. 2. To understand the tsunami wave characteristics such as wave generation, wave propagation, wave velocity and wave transformation, it is necessary to observe the wave profiles using buoys and water level station. In Thailand, there are 8 water level stations along the Andaman coastline, i.e. Ranong, Kuraburi, Phuket, Krabi, Trang, Tarutao, and Satun. The locations of these tidal gauging stations are shown in Fig. 1 as solid circles.
Profile Evolution Analysis of Gravel Beach
Li, Bin (The State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Fang, Kezhao (The State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology) | Sun, Jiawen (National Marine Environment Monitoring Center, State Oceanic Administration) | Liu, Zhongbo (Center for Ports and Maritime Safety, Dalian Maritime University) | You, Zaijin (Center for Ports and Maritime Safety, Dalian Maritime University)
ABSTRACT Gravel beaches are often made artificially to protect coastal beaches from erosion as they are of high permeability and excellent ability in dissipating wave energy. In this study, a laboratory experiment has been undertaken to investigate physical processes of gravel beach profile under different irregular waves. The initial beach slope is 1:7 and the scaled gravel diameter D50 is 2 mm. The laboratory data on the gravel beach profile under different wave conditions were collected and then analyzed. It is found that: the equilibrium beach profiles observed are reflective and stepped profiles; the beach surface above the average low tidal level is net siltation and underwater found to be eroded obviously, while the sediment in the upper beach surface is shown to accumulate continuously; a combination of different water levels and waves has been shown to result in different transport rates of the gravel beach. INTRODUCTION The coastlines of many countries around the world confront risk of erosion. At present, there are mainly two ways to prevent coastal erosion. The first is the โhardโ protection approach, such as building underwater embankment or concrete seawall along coast. The benefit of this method is to directly protect the coastline from retreating any more, however the disadvantage is that the coastline landscape is greatly affected. The second method is the โsoftโ coastal protection approach, such as beach nourishment with sand, which can create a beautiful beach with the beach sediment property unchanged. Beach nourishment is usually adopted with the combination use of building hard coastal structures (seawalls, groins, breakwaters, etc.), but scouring nearby the structure toes commonly occurs due to sharp change of local hydrodynamics. Hypothetical we purely use sand to nourish the beach, then an extremely large amount of sand is needed to this end and local governments perhaps can not afford it (Pierluigi, 2003). Alternative โsoftโ coastal protection is to use gravel sediment instead of sand as the nourishing sediments on the beach. The gravel beach, generally found near the bedrock coast, is a typical coastal morphology formed under the action of waves. Though not widely distributed in the world's coastal zones, yet they are extremely stable coastal morphological type. Gravel is defined as sediment with a diameter between 2 and 60 mm by the category of Udden-Wentworth (Udden, 1914; Wentworth, 1922), and its shape is uneven (Carter, 1988; King, 1972; Zenkovich, 1967). Generally speaking, there are four feasible sources of material in a gravel beach: erosion from sea cliffs, river input, seabed erosion and longshore transport. Wave breaking occurs when waves reach shore, which can lift coarse-grained seabed sediments and push them toward shore. When reaching the bottom of a beach slope, large-particle sediments accumulate at the water edge due to the decay of wave energy, while smaller ones continue to be transported to the beach; however, under the condition of storm surge, the large particulate sediment is quickly lifted and run to the top of the gravel beach, forming a tall gravel embankment and a morphological system with alternating grooves on the top of the gravel embankment. In addition, due to the limited scope of the ordinary wave and tide current, the upper part of the high-water line of the spring tide formed a steep ridge; after a storm, intertidal gravel changes as it is moved back and forth by wave currents (Carr, 1971, 1969). Due to the unique characteristics of gravel sediment, such as hydraulic roughness and permeability (Kobayashi, 1989; Van, 2000), the ability to dissipate a lot of wave energy naturally(Pierluigi, 2003), gravel beach is also an important form of coastal natural defense (Lรณpez, 2018; Poate, 2013). Therefore, beach managers tend to use coarse sand or gravel as a substitute for sand to regenerate eroded beaches, beach nourishment with coarse-grained material or gravel is thus becoming more and more frequent (Mason, 2007). Previous practice has shown that gravel beach has a very positive effect in coastal protection work, however, there are few studies on the profile morphology of gravel beach (Lรณpez, 2016). In the preliminary work, according to the Dean (1977) equilibrium profile principle and the profile analogy method (Cai, 2015), we carried out profile design for a gravel beach restoration project, and determined design parameters such as median grain size (D50=20 mm), beach slope (1:7), front elevation of beach berm (+3.8 m) and width of beach berm (10 m) (Fig.1). In this paper, a laboratory physical experiment has been undertaken to investigate the shape stability of the profile, and to study the shape evolution processes of gravel beach profile under different irregular waves and water levels.
Cross-shore Change of Beach Profile In Two Shapes of Beach Slope Breakdown
Cho, Won Chul (Department of Civil and Environmental Engineering, Chung-Ang University Dongjak-gu, Seoul, Korea) | Kim, In Ho (Department of Construction Disaster Prevention Engineering, Kangwon National University Samcheok-si, Gangwon-do, Korea)
ABSTRACT A numerical analysis is performed to predict actual change of beach profile due to cross-shore sediment transport during severe storm. In the existing cross-shore beach erosion studies, calculation of crossshore sediment transport includes only continuous process of beach erosion but stability of beach slope which predicts time of beach breakdown during erosion is not considered. In this study, the process of cross-shore beach erosion and beach profile change are simulated by various shapes of sand covering over the beach after breakdown. The stability of beach slope using the critical equilibrium analysis is analyzed on every changing beach profile in every given time to predict the actual change of cross-shore beach profile. The measured crossshore beach profile, storm surge level and wave height in Florida in U.S.A. are used for the numerical analysis and various values of soil modulus based on the existing studies are applied in the stability analysis of beach slope. INTRODUCTION Recently, Korea coastlines and beach profiles have been variously changed due to indiscreet coastal development, construction of coastal structures and unexpected super typhoons. Change of coastline and beach profile results in change of wave height, wave breaking, wave driven-current and so on, and it causes some coastal problems, such as coastal erosion and accretion, coastal structure damage and so on. Since continuous retreat of coastline and loss of beach sand due to coastal erosion causes geotechnical problems and eventually affects stability of coastal structures and houses adjacent to coastline, it is crucial to predict erosion process and stability of beach slope to protect coastal structures. Sediment transport, generally, is divided into longshore sediment transport and cross-shore sediment transport. Longshore sediment transport is driven primarily by an alongshore wave-induced current produced by waves approaching at an angle to the shore. Cross-shore sediment transport is considerably generated during storm.
Abstract State-of-the-art beach profile data sets including field measurements and laboratory experiments are applied to investigate the predictions of beach-face slope. Field measurements of beach profile and sediment characters yield a logarithmic-type of model to link beach-face slope and sediment grain size, while a series of laboratory experiments data sets which contains hydrodynamic forcing are compared with formula suggested by Sunamura (1984), and certain discussions and improvements are proposed regarding to the quantitative predictions of beach-face slope. Introduction Coastal areas have become a major issue among both the researchers and government during the last century due to its predominant importance in scientific regimes and economic reasons. But since the coastal regions usually subject to a highly dynamic processes, our understanding of the whole processes is still limited, especially in the swash zone where sediment experiencing uprush and backwash periodically. Besides, there are several factors that are responsible for the swash zone sediment transport, including beach materials and hydraulic factors, like wave height, wave period and wave direction. During the last century, researchers are paying more and more attention to the sandy beach protections not only because sandy beach accounting for a large part of tourism economic growth among coastal countries but also due to the prevailing of the engineering work such as beach nourishment. And one of the most important issues involved is the property of the sandy beach especially the swash zone slope, i.e. beach-face slope, which determines the scale of the available areas that can be used for recreation by human. Since the 1930s, a variety of scientific studies have been carried out by many researchers concerning the slope of the beach-face by means of both field measurements conducted by Bascom (1951), Emery and Gale (1951) King (1953) and laboratory experiments like Meyers (1933), Bagnold (1940). Since the swash zone is a complicated area affected by various factors, it is essential to select major controlling factors that are responsible for the variations of the beach. According to Sunamura (1984), controlling factors that are responsible for affecting beach-face slope are:beach sediment characteristics such as grain size, degree of sorting, size distribution, and specific gravity; wave properties such as wave height and wave period; ground-water-level; tidal stage; longshore current. And the first two factors are most crucial, although, our capacity of predicting beach-face slope is still limited. For example, Mclean (1968) analyzed two sand-shingle beaches and suggested that size verse slope curves for the studies beaches seems to contain two "plateaus" of almost constant slope angles and two areas of almost linear increase in slope with size. Dean (1977) hypothesized that equilibrium beach profile is directly related to the sediment size and proposed an equation of exponential type by the analysis of more than 500 beaches along the America and Gulf coasts, which is not available in the swash zone due to its exponential type of equation. King (1972) analyzed 27 beaches of different conditions and revealed the relation between beach slope and sediment size and wave energy, which did not take wave steepness into consideration.
- North America > United States (0.46)
- Asia > China > Shandong Province (0.46)