Soil and Rock SamplingSoil and Rock Sampling

Environmental Site Environmental Site CharacterizationCharacterization

• Number of samples taken depends on the size of the site

• Hollow stem auger normally used for environmental work

• Usually sample every 5ft in depth or at every change in formation

Sample ExaminationSample Examination

• Samples are examined in field for physical characteristics– Grain size, color, degree of sorting, and

moisture content– Visually present contamination– Usually screened in field using

• FID (flame ionization detector)• PID (photoionization detector)

– for volatile organic compound (VOCs)

Sample Examination Cont’d Sample Examination Cont’d

• A selected number of samples are sent to the lab– Usually one per soil boring– Shipped in jars to off-site lab for chemical

analyses– Waiting period of 6 to 10 weeks

Sample Examination Cont’dSample Examination Cont’d

• Drill cuttings– Stored in drums– Potentially contaminated– Approx. 1 drum for every 17ft of drilling in a

hole drilled with a 4.25 ID hollow stem auger– Analyzed to determine proper disposal

Detection ProbabilityDetection Probability

• A soil or core sample may only be representative of a limited area surrounding the hole– Fractures, bedding planes, solution cavities,

bedrock channels, sand lenses, and permeable zones can be missed be borehole programs

Types of SamplesTypes of Samples

Bulk SamplesBulk Samples

Shovelful or handful of drill cuttings from Shovelful or handful of drill cuttings from borehole borehole

Provides generalized picture of Provides generalized picture of formations cut by drillingformations cut by drilling

Formations are mixed together in this Formations are mixed together in this type of sampletype of sample

Least accurate of four typesLeast accurate of four types

Representative SamplesRepresentative Samples

Generally taken in some sort of drive or Generally taken in some sort of drive or push tubepush tube

Represent a specific depth interval in a Represent a specific depth interval in a boreholeborehole

Chemical constituents present but not Chemical constituents present but not necessarily undisturbednecessarily undisturbed

Undisturbed SamplesUndisturbed Samples

Physical and chemical disturbances Physical and chemical disturbances minimizedminimized

All parts of formation sampled without All parts of formation sampled without altering presampling relationshipaltering presampling relationship

Required for hydraulic conductivity Required for hydraulic conductivity testingtesting

Composite SamplesComposite Samples

Combination of discrete samples from Combination of discrete samples from different intervals in the same borehole, different intervals in the same borehole, mixed to represent the entire boreholemixed to represent the entire borehole

Combination could be from same Combination could be from same formation in different boreholesformation in different boreholes

Represents similar formation materials Represents similar formation materials across siteacross site

Types of Soil SamplersTypes of Soil Samplers

Solid Barrel SamplerSolid Barrel Sampler

• Consists of steel tube attached to a Consists of steel tube attached to a connector head at top and drive shoe at connector head at top and drive shoe at bottombottom

• 12-60in long, 1-6in wide12-60in long, 1-6in wide

• Sampler made of steel or stainless steel Sampler made of steel or stainless steel with brass, stainless steel or plastic linerwith brass, stainless steel or plastic liner– Liner material determined by specific Liner material determined by specific

applicationapplication

Split-Barrel SamplersSplit-Barrel Samplers

• Tubular section is split longitudinally into Tubular section is split longitudinally into two semi-cylindrical halvestwo semi-cylindrical halves

• Made from high strength or stainless steelMade from high strength or stainless steel

• Driven in 2ft incrementsDriven in 2ft increments

• Most commonly used sampler in geo-tech Most commonly used sampler in geo-tech and environmental workand environmental work

• Samples are often physically disturbed, Samples are often physically disturbed, but are suitable for soil chem testingbut are suitable for soil chem testing

Thin-Wall Tube SamplersThin-Wall Tube Samplers

• Consists of a connector head and a length Consists of a connector head and a length of thin-wall steel brass or stainless steel of thin-wall steel brass or stainless steel tubetube

• Usually 30in tube for 24in sampleUsually 30in tube for 24in sample• Sharpened at cutting end and crimped to Sharpened at cutting end and crimped to

1% of its inside diameter to allow free 1% of its inside diameter to allow free movement of the sample into the tubemovement of the sample into the tube

• Primarily used in cohesive, soft, or clayey Primarily used in cohesive, soft, or clayey formations where a relatively undisturbed formations where a relatively undisturbed sample is requiredsample is required

Continuous Tube SamplerContinuous Tube Sampler

• Used exclusively with a hollow-stem augerUsed exclusively with a hollow-stem auger• 5ft long split-barrel sampling tube, cutting shoe at 5ft long split-barrel sampling tube, cutting shoe at

bottom, head at topbottom, head at top• The head connects in a way that allows the The head connects in a way that allows the

sampling tube to remain stationary while the sampling tube to remain stationary while the auger turnsauger turns

• Works well in clays and other cohesive soils and Works well in clays and other cohesive soils and in granular material above the water tablein granular material above the water table

• Material inflow may occur when the water table is Material inflow may occur when the water table is encounteredencountered– This makes it very difficult to recover samplesThis makes it very difficult to recover samples

Rotary SamplersRotary Samplers

• Pitcher or Denison sampler, or the Pitcher or Denison sampler, or the Geo-barrelGeo-barrel

• Requires circulation fluidsRequires circulation fluids

• Useful for Geo-tech work, not Useful for Geo-tech work, not environmentalenvironmental

• Retrieves disturbed and undisturbed Retrieves disturbed and undisturbed samplessamples

Piston SamplersPiston Samplers

• Consists of a thin-wall tube, a piston, and Consists of a thin-wall tube, a piston, and mechanisms for regulating movement mechanisms for regulating movement between the tube and the pistonbetween the tube and the piston

• Specifically for use in soft formationsSpecifically for use in soft formations• Some physical disturbance of samplesSome physical disturbance of samples• The sampler is flush with the end of the The sampler is flush with the end of the

fixed piston, lowered into hole on drill rodfixed piston, lowered into hole on drill rod• Hydraulic fluids force the tube into the soil Hydraulic fluids force the tube into the soil

while the fixed piston remains stationarywhile the fixed piston remains stationary• Sampler then pulled back by hydraulic Sampler then pulled back by hydraulic

fluidsfluids

Methods of SamplingMethods of Sampling

Environmental samples are generally Environmental samples are generally taken from the bottom of the taken from the bottom of the boreholeborehole

Bulk samples are generally taken Bulk samples are generally taken from the cuttingsfrom the cuttings

DrivingDriving

Most common method for obtaining Most common method for obtaining split barrel samplessplit barrel samples

Uses 140lb safety hammerUses 140lb safety hammer Hammer sits at ground levelHammer sits at ground level Back-hammering or hydraulic fluid Back-hammering or hydraulic fluid

used to lift the samplerused to lift the sampler– Back-hammering may result in loss of Back-hammering may result in loss of

samplesample

Driving Cont’dDriving Cont’d

The number of hammer blows made The number of hammer blows made to drive the sampler is recorded for to drive the sampler is recorded for every 6in every 6in – This provides useful information about This provides useful information about

the type of material being penetratedthe type of material being penetrated– If the sampler reaches 50 blows in 6in If the sampler reaches 50 blows in 6in

interval, refusal is metinterval, refusal is met– Excessive hammering may result in drill Excessive hammering may result in drill

rod failurerod failure

PushingPushing

Uses a hydraulic feed system on a drill Uses a hydraulic feed system on a drill rig to press the sampler into the soilrig to press the sampler into the soil

The drill rod string should be connected The drill rod string should be connected to the drill so hydraulic retract can be to the drill so hydraulic retract can be used to withdraw samples from the used to withdraw samples from the boreholeborehole

Normally used for thin-wall tube samplersNormally used for thin-wall tube samplers Occasionally used for split-barrel or solid-Occasionally used for split-barrel or solid-

barrel samplers in soft soilsbarrel samplers in soft soils

Rotation While PushingRotation While Pushing

Denison or Pitcher samplers or Denison or Pitcher samplers or continuous tube samplerscontinuous tube samplers

Sampling barrel is suspended from a Sampling barrel is suspended from a bearing inside the barrel so the bearing inside the barrel so the sampler remains stationary while the sampler remains stationary while the auger drills into the formationauger drills into the formation

Sampler barrel is connected to the Sampler barrel is connected to the drill rods or a wire line system for drill rods or a wire line system for retrieval from the bottom of the retrieval from the bottom of the boreholeborehole