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Last Updated: May 15, 2020
ASTM D6286/D6286M-20
Standard Guide for Selection of Drilling and Direct Push Methods for Geotechnical and Environmental Subsurface Site Characterization
Significance and Use
4.1 The 1998 edition of this standard was written solely for selection of drilling methods for environmental applications and specifically for installation of groundwater monitoring wells. The second revision was made to include geotechnical applications since many of the advantages, disadvantages, and limitations discussed extensively throughout this document also apply to geotechnical design use such as data collection (sampling and in-situ testing) for construction design and instrumentation. Besides installation of monitoring wells (D5092/D5092M, D6724/D6724M), Environmental investigations are also made for sampling, in-situ testing, and installation of aquifer testing boreholes (D4044/D4044M, D4050).
4.2 There are other guides for geotechnical investigations addressing drilling methods such as in Eurocode (1, 2)5, U.S. Federal Highway Administration, (3, 4), U.S. Army Corps of Engineers, (5), and U.S. Bureau of Reclamation (6, 7). An authoritative Handbook on Environmental Site Characterization and Ground-Water Monitoring was compiled by Nielsen (8) which addresses drilling methods in detail including the advent of Direct Push methods developed for environmental investigations. Two other major drilling guides have been written by the National Drilling Association (9) and from the Australia Drilling Industry Training Committee (10) and these guides are user for the drillers.
4.3 Table 1 lists sixteen classes of methods addressed in this guide. The selection of particular method(s) for drilling/push boring requires that specific characteristics of each site be considered. This guide is intended to make the user aware of some of the various drilling/push boring methods available and the applications, advantages, and disadvantages of each with respect to determining geotechnical and environmental exploration.
(A) Actual achievable drilled depths will vary depending on the ambient geohydrologic conditions existing at the site and size of drilling/push boring equipment used. For example, large, high-torque rigs can drill to greater depths than their smaller counterparts under favorable site conditions. Boreholes drilled using air/air foam can reach greater depths more efficiently using two-stage positive-displacement compressors having the capability of developing working pressures of 12 to 17 kPa [250 to 350 psi] and 14 to 21 m3/h [500 to 750 cfm], particularly when submergence requires higher pressures. The smaller rotary-type compressors only are capable of producing a maximum working pressure of 6 kPa [125 psi] and produce 14 to 34 m3/h [500 to 1200 cfm]. Likewise, the rig mast must be constructed to safely carry the anticipated working loads expected. To allow for contingencies, it is recommended that the rated capacity of the mast be at least twice the anticipated weight load or normal pulling load.
(B) Soil = S (Cuttings), Rock = R (Cuttings), Fluid = F (some samples might require accessory sampling devices to obtain).
(C) I = Incremental sampling, C = continuous sampling.
4.3.1 On Table 1, practically all methods allow for coring, but some are much more efficient than others. Some drilling systems such as hollow-stem augers or wireline coring allow for practically continuous coring with minimal time for switching barrels while other drilling methods require the whole drilling equipment be removed from the hole. A prime example is the rate of rock coring using fluid rotary and conventional core barrels versus wireline rock coring. Wireline line rock coring is fast with long continuous runs whereas fluid rotary requires more “trip time” to add and remove shorter length core barrels using drill rods. Table 1 delineates methods where coring is possible, and in general, by either continuous (c) or incremental (i) sampling.
4.3.2 Sampling for environmental contaminants in soil, unconsolidated formations or groundwater often requires special considerations. In many environmental applications the use of drilling fluids (air, water, mud or foam) is often discouraged or even prohibited as these fluids may dilute the analytes of interest or even introduce analytes of concern not previously present (see 5.4).
4.4 This guide is most often used in conjunction with Guide D6169/D6169M on soil and rock sampling because sampling is the primary activity during drilling/push borings. There are several guides that deal with individual drilling methods (see Guides D5781/D5781M, D5782, D5783, D5784, D5872, D5875/D5875M, and D5876/D5876M) and how to the complete them for water quality monitoring well installations (see Practice D5092/D5092M). Practices on hollow-stem auger (D6151/D6151M) and sonic drilling (D6914/D6914M) were written for both geotechnical and environmental purposes and address sampling methods. Practice D2113 on rock core drilling includes sampling methods.
4.4.1 This guide covers direct push methods that are only used to make open holes for testing and sampling. This most often accomplished using dual tube systems and using the tubes for access of the subsurface for water sampling, D6001, soil sampling (D6282/D6282M), well installation (D6724/D6724M, D6725/D6725M) and aquifer testing (D7242/D7242M).
4.5 Predominant or Typical Drilling/Push Boring Methods Used for Geotechnical and Environmental Applications:
4.5.1 Geotechnical Investigations in Soils (unconsolidated deposits)—The most commonly used drilling methods for geotechnical exploration are fluid rotary drilling when groundwater is present. Hollow-stem auger drilling is also frequently used especially in arid regions where introduction of fluids is to be avoided in unsaturated soils.
4.5.2 Environmental Investigations in soils (unconsolidated deposits)—Most of these investigations are focused on soil contamination or, groundwater quality investigations so introduction of drilling fluids is not desirable and methods which generate minimal waste are highly favored. Direct Push methods were developed because they develop minimal investigative derived waste (IDW). Sonic methods are frequently used and generate minimal IDW but large cores. Hollow-stem augers and fluid rotary are used yet they generate large amounts of IDW.
4.5.2.1 At most environmental sites hazardous contaminants are present in the subsurface. Because of this fact any drill cuttings or drilling fluids returned to the surface should be properly handled, contained and stored (drums or roll-off bins, etc.) for sampling and laboratory analysis. Laboratory analyses may be required to verify that hazardous contaminants are not present above regulatory action levels prior to proper disposal. If concentrations of hazardous chemicals in cuttings or waste drilling fluids exceed regulatory action levels the waste may require treatment before disposal or may need to be properly disposed in a hazardous waste landfill. Review pertinent regulations before drilling/push boring to maintain compliance. The generation of contaminated waste drill cuttings and fluids significantly increase the potential for worker exposure to hazardous contaminants. Review pertinent regulations (such as OSHA 1910.120, etc.) to maintain compliance with worker safety and monitoring requirements.
4.5.3 Rock, Weathered Rock, and Coarse Cobble Boulder Drilling—Wireline rock coring is used in competent rock and results in the best core recovery. For coarse grained unconsolidated deposits and weathered bedrock samples are very difficult to recover and, rotary air drill through drive casing advancers are often used and require larger drills. Larger sonic drills can also drill and recover rock and boulder formations.
4.5.4 Sonic drilling methods have increased in use for both geotechnical and environmental explorations. The method offers very rapid continuous coring with the ability to drill difficult formations with large diameter equipment.
4.5.5 Shallow hand auger (D4700) is used for both disciplines but in most cases hand applications are used as part of initial site surveys prior to drilling/push boring or just for characterization of shallow soil sampling. Hand auguring is very labor intensive and has almost been abandoned in favor of using direct push equipment.
Note 1: The reliability of data and interpretations generated by this practice 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 generally are considered capable of competent testing. Users of this practice are cautioned that compliance with Practice D3740 does not assure reliable testing. Reliable testing depends on several factors and Practice D3740 provides a means of evaluating some of these factors.
Practice D3740 was developed for agencies engaged in the testing, inspection, or both, of soils and rock. As such, it is not totally applicable to agencies performing these field practices. Users of this test method should recognize that the framework of Practice D3740 is appropriate for evaluating the quality of an agency performing drilling. Currently, there is no known qualifying national authority that inspects agencies that perform this test method. There is training and certification for drillers that are normally required for critical installations such as water well drilling (NGWA, NDA).
Scope
1.1 This guide provides descriptions of various methods for site characterization along with advantages and disadvantages associated with each method discussed. This guide is intended to aid in the selection of drilling method(s) for geotechnical and environmental soil and rock borings for sampling, testing, and installation of wells, or other instrumentation. It does not address drilling for foundation improvement, drinking water wells, or special horizontal drilling techniques for utilities.
1.2 This guide cannot address all possible subsurface conditions that may occur such as, geologic, topographic, climatic, or anthropogenic. Site evaluation for engineering, design, and construction purposes is addressed in Guide D420. Soil and rock sampling in drill holes is addressed in Guide D6169/D6169M. Pertinent guides and practices addressing specific drilling methods, equipment, and procedures are listed in Section 2. Guide D5730 provides information on most all aspects of environmental site characterization.
1.3 The values stated in either SI units or inch-pound units (given in brackets) are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.4 This guide does not purport to comprehensively address all methods and the issues associated with drilling for geotechnical and environmental purposes. Users should seek qualified professionals for decisions as to the proper equipment and methods that would be most successful for their site investigation. Other methods may be available for these methods and qualified professionals should have flexibility to exercise judgment as to possible alternatives not covered in this guide. The guide is current at the time of issue, but new alternative methods may become available prior to revisions. Therefore, users should consult with manufacturers or producers prior to specifying program requirements.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5.1 Drilling operators generally are required to be trained for safety requirements such as those of construction and environmental occupational safety programs dictated by country, regional, or local requirements such as the US. OSHA training programs. Drilling safety programs are also available from the National Drilling Association (NDA4U.com) or other country drilling associations.2
1.6 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education and experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.