Table of Contents
In this article, we will discuss boring methods.
The boring methods are utilized for exploration at higher depths where direct methods fail. These help to collect both disturbed as well as undisturbed samples Based on the method of boring.
2. Boring Methods
The following are the methods commonly used;
ii) Auger boring
a. Used in cohesive and soft soils above the water table.
b. Operate either manually or mechanically
c. Hand augers are used up to a depth of 6m and use mechanically operated augers for higher depth
d. The disturbed sample obtained and useful for identification purposes only
ii) Auger and Shell Boring
a. Cylindrical augers and shells with cutting edge or teeth at the lower end.
b. Hand operates rigs are used for depths up to 25 m and mechanized rigs up to 50 m.
c. Suitable for soft to stiff clays, shells for very shift, and hard clays.
iii) Wash boring
a. Wash boring is a fast and simple method
b. It can be used in all types of soils except boulders and rock
c. The method consists of first driving a casing through which a hollow • drilled rod with a sharp chisel. Water is forced under pressure through the drill rod which is alternatively raised and dropped and also rotated.
d. The cuttings are forced up to the ground surface in the form of soil water slurry through the annular space between the drill rod and the casing.
e. The change in soil stratification could be guessed from the rate of progress and the color of wash water.
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iv) Percussion Boring
a. Soil and rock formation are broken by repeated blows of heavy chisel
b. Suitable for all types of soil, boulders, and rock, however, get disturbed by the types of soil.
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v) Rotary boring
a. A very fast method of advancing holes in both rock and soil.
b. A drill bit, fixed to the lower end of the drill rods, is rotated by a suitable chuck and is always kept in firm contact with the bottom of the hole. A drilling mud, usually a water solution of bentonite, with or without other admixtures, is continuously forced down to the hollow drill rods.
c. The muds returning upwards bring the cuttings to the surface.
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