ASTM D4971-08

Results of this test method are used to predict displacements in rock mass caused by loads from a structure or from underground construction. It is one of several tests that should be performed.

Because the jack can apply directed loads, this test method can be performed to provide an estimate of anisotropy.

In theory, the analysis of test data is straight forward; the modulus estimate requires a record of applied hydraulic pressure versus borehole diameter change, and a knowledge of the rock's Poisson's ratio. In practice, the above procedure, using the original theoretical formula, frequently has resulted in computing a material modulus that was demonstrably too low.

For analyzing the test data it is assumed that the rock mass is linearly elastic, isotropic, and homogeneous. Within these assumptions, this test method can provide useful data for rock masses for which equivalent continuous properties can not be found or estimated.

Note 1—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. Users of this test method are cautioned that compliance with Practice D 3740 does not in itself assure reliable testing. Reliable testing depends on many factors; Practice D 3740 provides a means of evaluating some of those factors.

1.1 This test method covers the estimation of in situ modulus of a rock mass at various depths and orientations. Information on time-dependent deformation may also be obtained.

1.2 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D 6026.

1.2.1 The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to the accuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this standard is beyond its scope.

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.

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.