پديد آورندگان :
مطلبي زاده، محمدرضا دانشگاه تربيت مدرس - دانشكده مهندسي عمران , شفيعي فر، مهدي دانشگاه تربيت مدرس - دانشكده مهندسي عمران و محيط زيست , قدسيان، مسعود دانشگاه تربيت مدرس - پروهشكده مهندسي آب - دانشكده مهندسي عمران و محيط زيست
كليدواژه :
سواحل ماسه اي , ناحيه سواش , روش سطح پاسخ , مدل آزمايشگاهي , موقعيت شروع رسوبگذاري سواش
چكيده فارسي :
ناحيه سواش، بعنوان محدوده ي انتهايي ناحيه داخلي شكست، مناطق و سازه هاي ساحلي را تحت تاثير قرار مي دهد. عملكرد سواش تحت تاثير امواج ورودي از ناحيه شكست، هندسه بستر ساحلي و اندركنش سفره زيرزميني- دريا است. در تحقيقات گذشته براي طراحي آزمايش ها از روش «هر بار يك عامل» استفاده شده است و تاثير كيفي پارامترهاي ارتفاع و پريود موج منظم، تراز آب سمت دريا، تراز سفره زير زميني، و شيب ساحل بر تغيير شكل ساحل مورد بررسي قرار گرفته است. در تحقيق حاضر، براي ساحل ماسه اي انعكاسي با قطر متوسط mm0/8، آزمايش ها به روش «سطح پاسخ مركزي» طراحي شده اند و تاثير كمي و متقابل پارامترهاي ارتفاع و پريود موج نامنظم، ترازهاي آب سمت دريا و پشت ساحل، و شيب ساحل؛ بر موقعيت شروع رسوب گذاري سواش بررسي شده است. نتايج حاصل از روش سطح پاسخ مركزي نشان داد تراز آب زير زميني در ساحل، تاثير معناداري بر موقعيت شروع رسوبگذاري سواش ندارد و افزايش ارتفاع موج منجر به جابجايي سريع اين موقعيت به بالاي ساحل مي شود. موقعيت شروع رسوبگذاري سواش با زياد شدن شيب ساحل به بالاي ساحل حركت مي كند و برعكس با بالا آمدن تراز آب سمت دريا اين موقعيت به سمت پايين ساحل جابجا مي شود. اندركنش قابل توجهي بين ميزان تاثير ارتفاع و پريود موج بر موقعيت شروع رسوب گذاري سواش وجود دارد. در ضمن بين تراز آب سمت دريا و ارتفاع موج اندركنش كمي وجود دارد.
چكيده لاتين :
The Swash zone, as extreme area of inner surf zone, influences coastal area and coastal structures. It is defined as the part of the beach between the minimum wave run-down and maximum wave run-up. It constitutes a beach area where waves dissipate or reflect their remaining energy after traveling towards the shore. The role of Swash zone is influenced by incoming waves from surf zone, the geometry of beach face and the interaction between beach groundwater and surf zone. The review of Laboratory researches indicated that wave height and period, beach slope, grain size distribution of beach material, still water level (SWL), beach groundwater level, the hydraulic conductivity of beach influence on the evolution of sand beaches. In a few laboratory researches, experiments are designed with One Factor at a Time method (OFAT) and the qualitative effect of parameters of regular wave height and period, SWL and beach groundwater level, and beach slope are investigated on nearshore evolution.
In this research, experiments are designed using Central Composite Design (CCD) of Response Surface Method (RSM). CCD is a type of response surface design that present very good predictions in the middle of the design space. Important properties and features of CCD are orthogonality, rotatability and uniformity. The quantitative effects and interactions of irregular wave height and period, beach groundwater level and SWL, and beach slope on beach profile evolution is examined in a sandy beach by 50 experiments designed with CCD. The experiments were carried out in a wave flume with a length of 16 m and width of 1 m at Hydraulic laboratory of Tarbiat Modares University. The experimental setup is designed to simulate varying beach groundwater level and SWL, and course sand (d50=0.8mm) is selected for beach material. Analysis of hydrodynamic data of the experiments indicated that the type of breaking waves is plunging wave and the hydrodynamic status of the swash zone is intermediate condition. The starting point of swash sedimentation (SWS) is extracted from the mean of the beach profiles evolution.
By analyzing experiments' SWS using CCD, a cubic model is suggested with 95% of confidence level and predicted R-squared of 0.86. The results of model revealed that groundwater level has no significant effect on SWS. Wave height is the most influential factor affecting SWS. Increasing wave height results in the rapid movement of this position to upper beach.
By increasing wave period, SWS got away from coastline in small wave heights, and conversely SWS came close to coastline in high wave heights. This indicates that there is a significant interaction between wave height and period. By increasing water depth flume, SWS came close to beach in small wave heights and it got away from beach in high wave heights, which indicates that there is a mild interaction between wave height and still water level. According to the results, increasing of wave period and still water level increase and decrease the rate of wave height effect, respectively. When the beach slope was 12.5%, SWS got away from the sea and came close to the coastline.
