In this paper the piping and filter

two correlative topics

are stated and the background of studying development is reviewed. Meanwhile our studied results are also given for comparison. This is part I about piping topic which is an important phenomenon of seepage deformation and related to the foundation destroying caused by seepage. Firstly

the inherent meaning of piping and the present studying situation with its developing direction are discussed and criticized. Secondly

our experimental data in past about piping and the studied results with formulas

including the discriminating method of piping soil and non-piping soil and the piping critical gradients for seepage flow upward and horizontal

are introduced. Then the published experimental data in references up to date are cited to verify the writer’s formulas once again that shows reliable after verification. Also it shows that the method of piping study based on the soil grain size grading curve is the latest studying trend. Therefore publishing those past studied results for comparison and discussion is beneficial.