To ensure the stability of seashore cofferdam in which geotextile is used for filter layer, the following two factors should be considered in design, one is the seepage force caused by different water level between the outer side and inner side of the cofferdam, the other is the weak anti-slide interface between the geotextile and the upper covering gravel.

The new techniques and methods of consolidating soft foundation by geotex-tile, filter layer of geotextile and applying big woven bag filled with mud to mounding rocommended in the design of port engineering in recent years were mainly introduced in the paper.

The paper gives an introduction to the procedure of changing the crushed stone filter layer into the debris one thrown over the rubble -mound behind the caissons of No.

Study on piping and filters : part I of piging;

In this paper, the effect of water scouring to the filter about clay and gravelly soil is analyzed by using the crack scour tests.

An introduction is given to the construction size distribution curve and opening size distribution curve of geo textiles and their correlative probabilistic analysis, and the seepage path m is considered as a notable parameter in filter design.

Because of the mixture of a small amount of silt and high volume of sand in river water, the filtering layer will be blocked after water-intaken project’s long time running.

On the basis of the discussion,the article makes inquiries of the problem of choice of filtering layer.