By definition the tensile strength is obtained by the direct uniaxial tensile test. But the tensile test is difficult and expensive for routine application. The splitting tensile test appears to offer a desirable alternative, because it is much simpler and inexpensive. Furthermore, engineers involved in rock mechanics design usually deal with complicated stress fields, including various combinations of compressive and tensile stress fields. Under such conditions, the tensile strength should be obtained with the presence of compressive stresses to be representative of the field conditions. The splitting tensile strength test is one of the simplest tests in which such stress fields occur. Since it is widely used in practice, a uniform test method is needed for data to be comparable. A uniform test is also needed to ensure that the disk specimens break diametrally due to tensile pulling along the loading diameter.

Note 2—Notwithstanding the statements on precision and bias contained in this test method; the precision of this test method 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 D 3740 are generally considered capable of competent and objective testing. Reliable testing depends on many factors; Practice D 3740 provides a means of evaluating some of these factors.

1.1 This test method covers testing apparatus, specimen preparation, and testing procedures for determining the splitting tensile strength of rock by diametral line compression of a disk.

Note 1—The tensile strength of rock determined by tests other than the straight pull test is designated as the “indirect” tensile strength and, specifically, the value obtained in Section 9 of this test is termed the “splitting” tensile strength.

1.2 The values stated in SI units are to be regarded as the standard. The values in parentheses are mathematical conversions and are provided for information only.

1.3 All dimension and force measurements, and stress calculations shall conform to the guidelines for significant digits and rounding established in Practice D 6026.

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