محمدرضا مطلبی زاده

The Toe is a structure with the function of supporting the armor layer and preventing scouring of the substrate. Due to the location of the toe under water, the safe design of this layer is important. Experiments have been conducted in order to investigate the parameters of wave period, water depth, nominal stone diameter, toe width and berm height. Based on the results of the experiments, the wave period has a great effect on the stability of the Toe. In the next step, the depth of the water above the Toe is important in the amount of damage caused to the Toe. By increasing the nominal diameter of the Toe stone, no significant reduction in the amount of damage was observed. Decreasing the front slope of the toe from 1:1.5 to 1:3 was a solution to achieve stability. By reducing the front slope, the overall width of the berm increases; Therefore, it was decided to implement the Toe with a front slope of 1:1.5 and the width of the berm to be two nominal diameters. In this case, due to the collision of waves; The front slope of the toe is changed and becomes stable.

Reflective beaches requires a combination of lower waves, longer periods and particularly coarser sands. They are typically steep in beach profile with a narrow shoaling and surf zone, composed of coarse sediment. Coarser sediment allows percolation during the swash part of the wave cycle, thus reducing the strength of backwash and allowing material be deposited in the swash zone
The Swash zone, as extreme area of inner surf zone, influences coastal area and coastal structures. It 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 is 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 are carried out in laboratory flume in Faculty of Civil and Environmental Engineering, Tarbiat Modares University with high accuracy. 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 position of swash sedimentation (SWS) is extracted from mean of the beach profiles evolution.
By analyzing of experiment's SWS using CCD, a cubic model is suggested with %95 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 and increasing wave height result to this position moves to upper beach rapidly. In addition, increasing beach slope causes the movement of SWS toward the beach. Increasing sea level lead to the displacement of SWS toward the sea.
This model indicated that the effect of wave height on SWS depends on wave period strongly and there is significant interaction between them. In addition, there is slightly interaction between the SWL and wave height and these variables influence on the role of each other in SWS.