types of samplers

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Geotechnical Engineering Laboratory

Assignment

Types of Samplers

Submitted to: Engr. Jahanzaib

Submitted by: Shay haq

2010-civ-33

Department of Civil Engineering

University of Engineering and Technology Lahore.


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Types OF Samplers:

Split Spoon Sampler

Standard Split spoon sampler is the most commonly used sampler for obtaining a disturbedsample of the soil.

Characteristics:

the inside diameter of the split spoon sampler is 38mm and outside diameter is 50mm. the

coupling head may be provided with a check valve and 4 venting ports of 10mm diameter toimprove sample recovery.

This is driven into the ground at the bottom of a borehole by blows from a slide hammer with aweight of 63.5 kg (140 lbs.) falling through a distance of 760 mm (30 in). The sample tube isdriven 150 mm into the ground and then the number of blows needed for the tube to penetrateeach 150 mm (6 in) up to a depth of 450 mm (18 in) is recorded. The sum of the number ofblows required for the second and third 6 in. of penetration is termed the "standard penetrationresistance" or the "N-value". In cases where 50 blows are insufficient to advance it through a150 mm (6 in) interval the penetration after 50 blows is recorded. The blow count provides anindication of the density of the ground, and it is used in many empirical geotechnical engineeringformulae. After the borehole has been made, the sampler is attached to the drilling rod andlowered into the holes. The sample is collected by jacking of forcing the sampler into the soil byrepeated blows of a drop hammer. The sampler is then withdrawn. The split tube is separatedafter removing the shoe and the coupling and the sample is taken out. It has been placed in acontainer, scaled and transported to the laboratory.

If the soil encountered in the borehole is fine sand and it lies below the water table, the samplerecovery becomes difficult. For such soils the spring core catcher is used to avoid recovery. Asthe sample is lifted, the spring close and form a dome and retain the sample.

While taking samples, care should be taken to ensure that the water level in the hole is

maintained slightly higher than the piezometric level at the bottom of the hole. It is necessary toprevent quick sand conditions.

The split tube may be provided with a thin metal or plastic tube liner to protect the sample and tohold it together. After the sample has been collected, the liner and the sample it contains areremoved from the tube and ends are scaled


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Split spoon sampler is basically a thick walled steel tube, split length wise. A drive shoeattached to the lower end serve as the cutting edge. The sample head is screwed at the upperend of the split spoon. The standard size of the split spoon sampler is 35mm internal and50.8mm external diameter. The sampler is lowered to the bottom of the borehole by attaching itto the drill rod. The sampler is then driven by forcing it to the soil/ground by blows from ahammer. The assembly of the sampler is then extracted from the hole and the cutting edge andcoupling at the top are unscrewed. The two halves of the barrels are separated and the sampleis thus exposed. The sample may be placed in a glass jar and sealed after visual examination.For determining penetration resistance (N value) of soil which can be related to unconfined

Compressive strength, Penetration resistance (N value) of soil is determined by giving a numberof blows with a 65 kg. Weight falling through a given distance of 75 cm required to penetrate.


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Components:

It consists of three components:


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1) Driving shoe, made of tool steel, about 75mm long.

2) Steel tube about 450mm long, split longitudinally in two halves

3) Coupling at the top of the tube about 150mm long.

Advantages:

With the help of the split spoon sampler it is easy to obtain samples in unconsolidatedmaterials above 100ft.

It produces good-quality samples for both description and chemical analysis.

It is relatively efficient and inexpensive at shallow and intermediate depths.

Disadvantages:

Split spoon sampler provides disturbed samples and cannot be used in soils where water tableis present.

Shelby Tube Sampler:


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Shelby tubes are thin wall tube samplers made of stainless steel. The outside diameter of thetube may be between 40 to 125mm. the commonly used samplers have outside diameter ofeither 50.8mm or 76.2 mm. the bottom of the tube is sharpened or beveled, which acts ascutting edge. The area ratio is less than 15% and the inside clearance is 0.5% to 3%. For sandysoils the length of the tube is between 5 to 10 times the diameter and for clayey soil the lengthof the tube is between 10 to 15 times the diameters. The diameter generally varies between 40and 125mm and thickness varies from 1.25 to 3.15mm.

The sampler tube is attached to the drilling rod and lowered to the bottom of the borehole. It isthen pushed into the soil. Care shall be taken to push the tube into the soil by a continuousrapid motion without impact or twisting. The tube should be pushed to the length provided forthe sample. At least 5 minutes after pushing the tube into its final position, the tube is turned tworevolutions to shear the sample off at the bottom before it is withdrawn. The tube is taken outand its ends are sealed before transportation. Shelby tubes are used to obtain the undisturbedsample of clay.


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Shelby tube samplers consist of a one-piece, thin-walled, hollow steel tube with an open-endthat has been honed to a cutting edge. The main purpose of the Shelby Tube sampler is torecover relatively undisturbed soil samples suitable for laboratory tests of engineering propertiessuch as strength, compressibility, permeability, and density. They are very useful for collectingsoils that are particularly sensitive to sampling disturbance, including fine cohesive soils andclays, provided that the soil has not been disturbed by sinking the borehole and are free fromlarge particles.


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Specification of sizes:


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Benefits:

Thin walledtubes of the samplers are made of steel or of brass. Steel is less liable to buckle whenpressed into the stiffed soils. But may corrode. Brass is easier to handle in laboratorywhen it is necessary to cut off part of the tube and sample for testing while preservingthe remainder.

By means of Shelby tube sample we can collect good quality, virtuallyundisturbed samples for description and chemical analysis

Shelby tube samples is effective in fine, cohesive soils

2" samplers are ideal for use through 3 1/2" geotechnical direct push systems(dual tube) and 2 1/4" ID hollow stem augers

3" samplers are ideal for use through 4 1/2" ID hollow stem augers

Not recommended for drilling through gravel or hard clay.

Draw backs


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Shelby tube sampler is used for normally consolidated clays and over-consolidated clays. It is not suitable for non-cohesive or granular soils

Shelby tube sampler has an open end no cutting edge so it is necessary to startfrom the ground level or pre drill a bore hole

The sampler tubes are fabricated from the cold formed seamless steel tubing. Amajor disadvantage of the use of steel for the sampler is the danger of corrosion.

Hydraulic Piston Sampler:

The piston consists of a thin walled tube with a piston inside. The piston keeps the lower end ofthe sampling tube closed when sampler is lowered to the bottom of the hole. After the samplerhas been lowered to the desired depth, the piston is prevented from the moving downward by asuitable arrangement, which differs in different types of piston samplers. The thin tube sampleris pushed past the piston to obtain the sample. The piston remains in contact with the top of the

sample.

The presence of the sample prevents rapid squeezing of the soft soils into the tube and reducesthe disturbance of the sample. A vacuum is created on the top of the sample, which helps inretaining the sample, during the withdrawal of the sampler. The piston provides protectionagainst the water pressure which otherwise would have occurred on the top of the sampleduring withdrawal of the sampler. Piston samplers are used for getting undisturbed soil samplesfrom soft and sensitive clays.

Piston samplers are a reliable and effective option where dual tube sampling is not possible dueto depth, below groundwater, or difficult lithologys. The center rod and tip will displace thecaving soils and the tip will keep the caving soils from entering the sampler preventingpremature sample collection and minimizing the chance for cross-contamination. When thepiston sampler is used in conjunction with the AMS dual tube system, it can be very efficient fordifficult lithologys and is ideal for sampling below groundwater and in caving soils. The designemploys a basket retainer in the drive tip so that an optional core catcher may be used toprevent sample losses in fine/sandy soils or saturated soils.

Hydraulic piston sampler is designed for taking the undisturbed samples in low strength finesoils such as silt and soft to stiff clays. The necessary hydraulic load is generated from thehydraulic power unit on a drilling rig, or by using a purpose built hydraulic power pack. An

operating pressure of 1200 psi is usually sufficient for taking samples in soil conditions for whichthe unit is designed.

The piston sampler is of the stationary type. The entire unit is rigid and fixed length 2850mmfrom the drilling rod connection at the top head to the piston head at the bottom. The onlymoving part is the hydraulic cylinder which slides up and down the central rods. The strokelength is exactly 1m.


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The sample tube is attached to the lower end of the hydraulic cylinder by means of 3 screws.Hydraulic oil flowing through the piston sampler causes the cylinder with attached sample tubeto move downwards into the soil. At the end of the stroke the apparatus is lifted out of theground and the full sample tube is removed, replacing it with an empty one.

The direction of flow of hydraulic oil is then reversed, causing the cylinder with attached sampletube to move upwards. When the cylinder has moved to its highest extent, the piston head isvisible at the bottom end of the sample tube. The apparatus is then lowered into the groundready for taking the next sample. To ensure a good seal against the bore of the sample tube,the pressure exerted by the piston seal can be adjusted by tightening or loosening the screwson the back-plate of the piston head. (The back plate compresses the seal when it is tightenedup).The standard sample tube is 4" bore (101.6 mm) made from aluminum and is 1000 mmlong. With a wall thickness of just 1.75 mm, these tubes produce a soil sample with minimumdisturbance. The area ratio is just 7%.


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Characteristics of Piston Sampler:

Sample flowing/heaving sands, swelling clays and soils belowgroundwater.

Sample through caving soil.

Eliminate prep robing with use of Dual Tube System.

Recover samples consistently.

Variety of sample sizes available.

Specifications of Piston Sampler:

The outfit consists of sampling tube, 550 or 580mm effective lengthpiston, one piston connecting rod 1 meter long

And a drive head with check valve and adaptor for drill rod.

Comparison

PROPERTIES SPLIT

SPOON

SAMPLER

SHELLBY

TUBE

PISTON

TUBE

PRICE $ 99 $ 312 $ 260

DESCRIPTION Tubesampler

Density tubesampler

Dryingpiston tube

MODEL C3125 S3757 10305-2

ASTM C-183 D-2937 -

AASHTO T-127 T-20 209-99

MANUFACTURER hogentogler hogentogler hogentogler

types of samplers

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