The Examination of the Auger Hole Method for the Project of Tile Drainage

Abstract

The authors examined the availability of the auger hole method for measuring the field permeability for tile drainage projects. The results were compared with the values of permeability calculated from tile drainage tests in the same test field and also with those obtained from the data of laboratory test.
From the point of view of the permeability, the soil texture of tested field was separated into two strata at the depth of 65cm. So two series of auger holes were dug, 50 cm and 80 cm deep respectively, and the layered analysis was applied.
It was found that Hooghoudt's fomula gave smaller values than other fomulas by two orders. It may be owing to the unreasonableness of Hooghoudt's formula which was based on horizontal flow into the hole.
In the case of the monolayer anlysis of upper layer, Ernst's and Kirkham's formulas nearly coincided with each other, and for lower layer, a little smaller values were obtained in comparison with the values of permeability obtained by laboratory tests. The values inversely calculated from the tile drainage formulas nearly corespond to those for the lower layer obtained by the auger hole method. This is pretty guessed from the fact that the water percolating into tiles passes through the upper and lower layers, and it was understood that the auger hole method is practically adoptable as the permeability test for tile drainage projects.