Design and Analysis of Seawall

Abstract

Coastal erosion has become a serious problem in recent times. The problem has become acute particularly in view of the encroachment by man of the coastal areas for development. Erosion of coastal line is continuous, causing loss of valuable land at the rate of 3 m to 6.5 m per year. During the past 20 years, various types of coastal works have been tried to evolve a satisfactory design which will withstand the severity of the waves and storms. A popular method of combating coastal erosion is construction of seawalls. These seawalls are generally of rubble mound type. Rubble mound seawall is the cheapest mode of construction compared to other types of seawall construction. The present cost of protection of one meter is Rs. 1, 00, 000/-. In the absence of any specific design method, Hudson's formula is generally used to arrive at the size of stones to be used for seawall. In practice, it is generally observed that seawalls have failed more often, giving room to doubt whether Hudson's formula is applicable to the design of seawalls or whether the failure mechanism is something else which is overlooked in design. The present investigation deals with the experimental studies conducted to investigate these aspects.So seawall design for 1:3 and 1:5 seaward slopes are made and tested in the wave flume. It is found that the scour at the toe is the main reason for failure. So it is proposed to add an apron of 2 m long extending from the toe of the seawall which is found to be the best as per the model studies.