ASTM D 3999/D3999M : 2011 : EDT 1

1.1These test methods cover the determination of the modulus and damping properties of soils in either intact or reconstituted states by either load or stroke controlled cyclic triaxial techniques. The standard is focused on determining these properties for soils in hydrostatically consolidated, undrained conditions.

1.2The cyclic triaxial properties of initially saturated or unsaturated soil specimens are evaluated relative to a number of factors including: strain level, density, number of cycles, material type, and effective stress.

1.3These test methods are applicable to both fine-grained and coarse-grained soils as defined by the unified soil classification system or by Practice D2487. Test specimens may be intact or reconstituted by compaction in the laboratory.

1.4Two test methods are provided for using a cyclic loader to determine the secant Young's modulus (E) and damping coefficient (D) for a soil specimen. The first test method (A) permits the determination of E and D using a constant load apparatus. The second test method (B) permits the determination of E and D using a constant stroke apparatus. The test methods are as follows:

1.5The development of relationships to aid in interpreting and evaluating test results are left to the engineer or office requesting the test.

1.6Limitations—There are certain limitations inherent in using cyclic triaxial tests to simulate the stress and strain conditions of a soil element in the field during an earthquake, with several summarized in the following sections. With due consideration for the factors affecting test results, carefully conducted cyclic triaxial tests can provide data on the cyclic behavior of soils with a degree of accuracy adequate for meaningful evaluations of modulus and damping coefficient below a shearing strain level of 0.5 %.

1.7The values stated in either SI units or inch-pound units [presented 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 non-conformance with the standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method.

1.8All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D6026. The procedures in Practice D6026 that are used to specify how data are collected, recorded, and calculated are regarded as the industry standard. In addition, they are representative of the significant digits that should generally be retained. The procedures do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the objectives of the user. Increasing or reducing the significant digits of reported data to be commensurate with these considerations is common practice. Consideration of the significant digits to be used in analysis methods for engineering design is beyond the scope of this standard.

1.9This 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 and health practices and determine the applicability of regulatory limitations prior to use.