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ASTM D6066_D6066M-24
Standard Test Method for Measuring Normalized Standard Penetration Test (SPT) Value, N60, of Sands
Standard Test Method for Measuring Normalized Standard Penetration Test (SPT) Value, N60 , of Sands
D6066_D6066M-24
ASTM|D6066_D6066M-24|en-US
Standard Test Method for Measuring Normalized Standard Penetration Test (SPT) Value, N60 , of Sands
Standard
D6066_D6066M Standard Test Method for Measuring Normalized Standard Penetration Test (SPT) Value, N60 , of Sands>
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Significance and Use
5.1 This standard is used to obtain more reliable SPT N-values than those that can be obtained using Test Method D1586/D1586M, which allows greater variability in equipment, calibration requirements, and hammer operation. The method described herein requires automatic or trip hammers, energy measurements, and borehole quality checks, and it restricts drilling methods to assure more repeatable N-values. Rope and cathead hammer operation is not allowed. This test method should be specified when N Values are used for geotechnical design purposes.
5.2 SPT N-values are used to estimate engineering properties of strength and compressibility of soils. The test is more useful in sands where recovery of intact samples for laboratory testing is difficult. SPT can be used in clays but is unreliable in soft clays. Reliable design requires N-values adjusted to a 60 % drill rod ETR, N60, due to the wide variability of hammer systems. An ETR of 60 % is representative of the average ETR used to develop many soil property correlations. Design for sand liquefaction evaluation requires further normalization of N-values to a reference stress level (see Appendix X1).
5.2.1 SPT is used in a wide variety of soils from sand to clays both above and below the water table (refer to 4.3 D1586/D1586M) but is generally not applicable to gravels and cemented or partially lithified soils that result in refusal. This test method requires use of fluids for drilling of loose sands below water table as they become unstable. This test can be applied to unsaturated soils with other drilling methods that have a stable borehole and fluid drilling requirements waived. When applying SPT to unsaturated soil the user must consider any changes to properties if the soil becomes saturated during drilling or after construction.
5.3 This test method requires measurement of the drill rod energy, EFV, and determination of the energy transfer ratio, ETR, using Test Method D4633. This measurement is performed by instrumenting drill rods just below the impact anvil at the surface. A hammer system may be adjusted to any desired ETR depending on project requirements by changing hammer drop height. For example, many automatic hammers run at fast rates of 50 BPM (blows per minute) and deliver high energy. The speed may be reduced to allow for detailed recording penetration rates or to meet other project requirements.
5.3.1 It may not be practical to measure EFV continuously, in which case hammer systems are measured periodically either onsite at critical projects or on a regular schedule (see 10.2). Once ETR is known for a specific hammer, it is possible to check hammer performance by monitoring blow count rates and hammer impact velocities to verify they are operating consistently.
5.4 Use of this practice provides a disturbed soil sample for identification and for laboratory testing such as water content (Test Method D2216) and Soil Classification (Test Methods D2487, D2488). The classification information is commonly used to develop site stratigraphy.
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 facility used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some, but not all, of those factors.
Practice D3740 was developed for agencies engaged in laboratory testing, inspection, or both, of soils and rock. As such, it is not totally applicable to agencies performing this field test. Users of this test method should recognize that the framework of Practice D3740 is appropriate for evaluating the quality of an agency performing this test method. Currently, there is no known qualifying national authority that inspects agencies that perform this test method.
Scope
1.1 This test method provides a procedure to normalize the Standard Penetration Test (SPT) N-value obtained from Test Method D1586/D1586M to standard energy for estimating engineering properties of sands. To reduce the inherent variability of the SPT, this test method requires energy measurements and restricts hammer systems and drilling methods. Refer to Standard Test Method D1586/D1586M on Penetration Test (SPT) and Split-Barrel Sampling of Soils for detailed information cited throughout this standard. Standard Guide D6286/D6286M provides additional information on drilling methods.
1.2 This test method requires the use of automatic hammers and the determination of the energy transmission, EFV, using Test Method D4633 to correct the SPT N-value and normalize it to N60 at 60 percent ETR (see 3.3).
1.3 The previous version of this standard was developed specifically for liquefaction evaluation of sands to provide an SPT (N1)60 value normalized to overburden stress of one-atmosphere pressure. Evaluation of liquefaction resistance requires qualified professional judgment, and (N1)60 corrections are now given in Appendix X1. Cone Penetration Testing (Test Method D5778) is also used for liquefaction evaluations as it is economical and provides detailed stratigraphic data.
1.4 Units—The values stated in either inch-pound units or SI units 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 non-conformance with the standard. Reporting of test results in units other than inch-pound units shall not be regarded as nonconformance with this practice. SI equivalent units shown herein are in general conformance with existing international standards.
1.4.1 For overburden stress pressure correction calculations methods in Appendix X1, common units are ton/ft2, kg/cm2, atm, and bars. Since these units are approximately equal (within a factor of 1.1), many users prefer the use of these units in stress correction calculations. For those using kPa or kN/m2, 100 kPa is approximately equal to one ton/ft2. The stress exponent, n, is approximately equal for these units.
1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.
1.6 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.
1.7 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.