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Examoogle • User • info@examoogle.com • EE-2024-8821
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Auger boring is used in __________ type of soil.
Cohesion less soil
Cohesive soil
Coarse-grained soil
Pervious soil
Cohesive soil
Auger boring is a method of sub-surface soil investigation primarily used in cohesive soils that possess enough internal strength to maintain the stability of the borehole walls. In non-cohesive or loose soils, the borehole typically collapses upon withdrawal of the auger due to lack of inter-particle bonding.
Auger boring is a method of sub-surface soil investigation primarily used in cohesive soils that possess enough internal strength to maintain the stability of the borehole walls. In non-cohesive or loose soils, the borehole typically collapses upon withdrawal of the auger due to lack of inter-particle bonding.
c>0 — Requirement for cohesive soils to maintain hole stability
Cu=pacu — Undrained shear strength ratio relevant to soil consistency
The principle involves the rotation of a spiral or helical blade (auger) which cuts into the soil and carries the loose material to the surface as it is extracted. In cohesive soil, the adhesion and cohesion forces hold the soil together within the auger flights, allowing for the extraction of representative samples without the need for casing or stabilizing drilling mud.
Auger boring is a shallow investigation method, typically limited to 5-10 meters depth.
It is most effective in stiff to very stiff clays.
It is unsuitable for saturated cohesionless sands below the water table.
Disturbed samples obtained are suitable for classification and index property tests.
Quick and economical
Minimal disturbance to the site
Requires simple equipment
Limited depth of investigation
Not suitable for rock or very hard strata
Borehole wall collapse in loose cohesionless soils
Highways and road construction site exploration
Shallow foundation investigations
Borrow pit identification
In very soft soils, a post-hole auger is preferred.
In cohesionless soils, shell and auger or wash boring is generally required to maintain borehole stability.
B is correct — Auger boring is specifically effective in cohesive soils because the soil's inherent cohesive property ensures the stability of the borehole wall during the drilling process.
Always remember: If the soil is cohesionless (c=0), the stability depends entirely on friction; auger boring will fail to keep the hole open without casing.