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Examoogle • User • info@examoogle.com • EE-2024-8821
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Wash boring cannot be used for _________ type of soil strata.
Cohesive soil
Cohesion less soil
Boulder
All of the mentioned
Boulder
Wash boring is a soil exploration method that utilizes water jetting to erode the soil and bring it to the surface. It is ineffective in strata containing boulders or large rocks because the water pressure is insufficient to displace them, and the boring tool cannot penetrate these hard, massive obstacles.
Wash boring is a soil exploration method that utilizes water jetting to erode the soil and bring it to the surface. It is ineffective in strata containing boulders or large rocks because the water pressure is insufficient to displace them, and the boring tool cannot penetrate these hard, massive obstacles.
vs=AaQ — Represents the upward velocity of water-soil slurry in the annular space, where Q is flow rate and Aa is the annular area.
The method involves a drill rod with a hollow bit at the end through which water is pumped at high pressure. This action causes soil to be loosened and carried to the surface through the annular space between the drill rod and the borehole casing. Since the tool lacks the mechanical strength or percussion capability to crush or bypass boulders, the drilling process ceases upon encountering such obstructions.
Wash boring is best suited for soft to stiff cohesive soils and loose to medium dense cohesionless soils.
It cannot be used for rock drilling or when boulders are present.
The process involves significant disturbance to the soil structure at the bottom of the hole.
It is a quick and cheap method but yields disturbed samples.
Fast and economical method for shallow explorations.
Easily portable equipment.
Cannot penetrate boulders or hard rock.
Provides highly disturbed samples, making it unsuitable for strength tests.
Difficulty in determining accurate changes in soil strata.
Preliminary site investigations.
Exploration in soft alluvial deposits.
In cohesive soils, the water jet facilitates drilling by softening the material.
In clean sands, the water helps maintain the hole stability using a casing until a certain depth.
The method is generally limited to depths of about 20-30 meters.
C is correct — Wash boring fails in boulder-rich strata because the hydraulic jetting process cannot displace or penetrate dense, large-sized rock fragments.
Always remember: if the soil is too hard (boulders/rock) or too sensitive to water (which might cause collapse), wash boring is not the recommended field technique.