4 COLLECTION TOOLS

4.2 POWER-DRIVEN SOIL SAMPLERS

4.2.1 Split and Solid Barrel

Description:

Split spoons are tubes constructed of high strength alloy steel with a tongue and groove arrangement running the length of the tube, allowing it to be split in half. The two halves are held together by a threaded drive head assembly at the top, and a hardened shoe at the bottom, with a beveled cutting tip. The sampler is driven by a 140-pound weight dropped through a 30-inch interval. When the split spoon is brought to the surface, it is disassembled and the core removed. Barrel samplers are similar to split spoons except they can not be taken apart. A core extruder might be required to remove the core from the barrel.

A series of consecutive cores may be extracted with a split-spoon sampler to give a complete soil column profile, or an auger may be used to drill down to the desired depth for sampling. The split spoon is then driven to its sampling depth through the bottom of the augured hole and the core extracted. The following procedure for split-spoon sampling describes the collection and extraction of undisturbed soil cores 18 or 24 inches in length:

1. Assemble the sampler by aligning both sides of the barrel and then screwing the drive shoe on the bottom and the head piece on top.
2. Place the sampler in a perpendicular position on the sample material.
3. Using a well ring, drive the tube. Do not drive past the bottom of the head piece or compression of the sample will result.
4. Record in the site logbook or on field data sheets the length of the tube used to penetrate the material being sampled, and the number of blows required to obtain this depth.
5. Withdraw the sampler and open by unscrewing the bit and head and splitting the barrel. The amount of recovery and soil type should be recorded on the boring log. If a split sample is desired, a cleaned, stainless steel knife should be used to divide the tube contents in half, longitudinally. This sampler is typically available in 2- and 3-1/2-inch diameters. However, in order to obtain the required sample volume, use of a larger barrel may be required.
6. Without disturbing the core, transfer it to appropriate labeled sample container(s) and seal tightly.

Analytes:

Media:

Some models have a liner that allows removal of the sample with minimum contact to air. A basket or spring retainer can be placed inside the tube near the tip to reduce loss of sample material. Disturbance of core samples prevents use for laboratory measurements of formation properties. The collection of soil samples using a split spoon is usually ineffective in sediments containing large cobbles and/or boulders. Measurement of soil compaction is not always consistent usually due to outside influences. Sample retention is often less than 100%, primarily for fine, dry soils.

Limitations:

• Not for use in consolidated formations.
• Split spoons are ineffective in cohesionless sands.
• Solid barrels have questionable recovery and quality below the water table.

ASTM Standards: