Standard Practice for Sampling of Soil Using the Hydraulically Operated Stationary Piston Sampler

Importancia y uso:

5.1 Hydraulically operated stationary piston samplers are used to gather soil samples for laboratory or field testing and analysis for geologic investigations, soil chemical composition studies, and water quality investigations. The sampler is sometimes used when attempts to recover unstable soils with thin-walled tubes, Practice D1587/D1587M, are unsuccessful. Examples of a few types of investigations in which hydraulic stationary piston samplers may be used include building site foundation studies containing soft sediments, highway and dam foundation investigations where softer soil formation need evaluation, wetland crossings utilizing floating structures, and hazardous waste site investigations. Hydraulically operated stationary piston samplers provide specimens necessary to determine the physical and chemical composition of soils and, in certain circumstances, contained pore fluids (see Guide D6169/D6169M).

5.2 Hydraulically operated stationary piston samplers can provide relatively intact soil samples of soft or loose formation materials for testing to determine accurate information on the physical characteristics of that soil. Samples of soft formation materials can be tested to determine numerous soil characteristics such as; soil stratigraphy, particle size, water content, permeability, shear strength, compressibility, and so forth. The chemical composition of soft formation soils can also be determined from the sample if provisions are made to ensure that clean, decontaminated tools are used in the sample gathering procedure. Field-extruded samples can be field-screened or laboratory-analyzed to determine the chemical composition of soil and contained pore fluids. Using sealed or protected sampling tools, cased boreholes, and proper advancement techniques can help in the acquisition of good representative samples. A general knowledge of subsurface conditions at the site is beneficial.

5.3 The use of this practice may not be the correct method for investigations of softer formations in all cases. As with all sampling methods, subsurface conditions affect the performance of the sample gathering equipment and methods used. For example, research indicates that clean sands may undergo volume changes in the sampling process, due to drainage.5 The hydraulically operated stationary piston sampler is generally not effective for cohesive formations with unconfined, undrained shear strength in excess of 2.0 tons per square foot, coarse sands, compact gravelly tills containing boulders and cobbles, compacted gravel, cemented soil, or solid rock. These formations may damage the sample or cause refusal to penetration. A small percentage of gravel or gravel cuttings in the base of the borehole can cause the tube to bend and deform, resulting in sample disturbance. Certain cohesive soils, depending on their water content, can create friction on the thin-walled tube which can exceed the hydraulic delivery force. Some rock formations can weather into soft or loose deposits where the hydraulically operated stationary piston sampler may be functional. The absence of groundwater can affect the performance of this sampling tool, and since this sampling method can introduce water to the borehole, it may not be suitable for sampling above the groundwater table when water is utilized as the activation fluid. As with all sampling and borehole advancement methods, precautions must be taken to prevent cross-contamination of aquifers through migration of contaminates up or down the borehole. Refer to Guide D6286/D6286M on selecting drilling methods for environmental site characterization for additional information about work at hazardous waste sites.

Note 1: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this practice are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.

Practice D3740 was developed for agencies engaged in the laboratory testing and/or inspection of soil and rock. As such, it is not totally applicable to agencies performing this practice. However, user of this practice must recognize that the framework of Practice D3740 is appropriate for evaluating the quality of an agency performing this practice. Currently, there is no known qualifying national authority that inspects agencies that perform this practice.

Subcomité:

D18.02

Referida por:

D2937-24, D2166_D2166M-24, D2166_D2166M-24, D4648_D4648M-24, D5092_D5092M-16R24

Volúmen:

04.09

Número ICS:

13.080.01 (Soil quality in general)

Palabras clave:

hydraulically operated; piston sampler; soil sampling; stationary piston; thin-walled tube;