Mahvin Ebadi - MSc Student, Department of Civil Engineering, University of Guilan, Rasht, Iran
Ahmad Lashteh Neshaei - Associate Professor, Department of Civil Engineering, University of Guilan, Rasht, Iran

Today, using geotextile in engineering has become prevalent, owing to some of their features such as: durability, resistance, permeability and incorruptibility against destructive factors within soil. Whereof geotextiles work simultaneously as a water drainage and a soil conservator against being washed up, it is allowed to use them as a filtering material. Geotextiles are also very easy to carry, simple to use and reasonable in a matter of price [1].The most common types of breakwaters are the rubblemound breakwaters with a long lifespan which can moderate wave energy very well. For a better and more efficient use of these types of breakwaters, some important properties must be optimized, for example reducing the amount of pore water pressure in core layer [2].Since pore water pressure is related to permeability, it can be reduced by a better replacement of filtering materials in breakwaters. To improve the efficiency of this process, the material of the filter layer can be changed. In this study, it has been tried to use a number of geotextiles as the filter layer to find out their effect on the reduction of the pore water pressure of the core layer of breakwaters.