Target GATE & ESE 2022 (Geotechnical Engineering)

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👉 For a good quality soil sampler all the parameters mentioned below should be low.

            Area ratio                       10% or less

           Inside clearance              0.5-3%

           Outside clearance           0-2%

👉 For soft sensitive clays, an area ratio of 10% or less is preferred.

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• Chunk samples are considered as undisturbed samples.
• Remoulded sampler tends to disturb the soil structure completely
• Split spoon sampler is a thick tube type of an open driven sampler with an area ratio around ratio 30%, so the samples collected are of the disturbed type 
•  Piston sampler is a thin tube type sampler and excellent tool for obtaining very fine undisturbed samples, especially in soft sensitive clays.      

👉 Split Spoon sampler: Used in all types of soil. It gives disturbed but representative sample.

      

👉 Rotary Sampler: It is double walled tube sampler. The outer tube (rotating barrel) is having a cutting bit so they can be used in hard cohesive soils and rocks.

👉Stationary piston sampler: Very much suited for sampling in soft soils and saturated sands.

👉Recovery Ratio(R.R): Ratio of recovered length of sample to penetration length of sampler.

         If           R.R = 1   Good recovery

         If           R.R <1   soil in sample is compressed

         If           R.R >1   soil has swelled

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