Wash Boring

Published: June 17, 2020 | Last updated: July 5, 2023

What Does Wash Boring Mean?

Wash boring is a method for advancing boreholes for site exploration and geotechnical investigation in most types of soil except gravels and boulders. The method is fast and simple to carry out and utilizes inexpensive, easily portable handling and drilling equipment.

By observing the change of color in the slurry flowing out of the hole, it is possible to determine certain soil characteristics. Since the sample obtained is completely disturbed, it is not suitable for very soft soil, fine to medium-grained soil, or in cemented soils and is valueless for interpreting the exact geotechnical properties of the soil.


Trenchlesspedia Explains Wash Boring

The wash boring process begins by first excavating an open hole on the ground to carry out the drilling operation. A piece of casing of a diameter of 50 to 100 mm and depth of 1.5 to 3 m is driven into the hole. The casing is fitted with a chopping bit fastened at the lower end of a wash pipe to help remove the soil inside the casing. Water is forced through the wash pipe and exits the chopping bit through a small opening at high velocity and fragments the soil.

The slurry created by the water exits the casing through the annular space between the wash pipe and the casing. As the borehole deepens, additional casings are attached and the process is continued to the desired depth. It is possible to guess the change in soil certification by the rate of penetration and the color of the water.


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