ASTM D8359-20 PDF Download

ASTM D8359-20 is a standard test method that provides guidelines, requirements, procedures, and analyses for determining the in situ rock deformation modulus and other associated rock properties using a flexible volumetric dilatometer. The test is typically conducted in vertical boreholes, but it can also be performed in inclined or horizontal holes, although the probe may drag along the borehole wall in these cases.

The deformation modulus of rock, as well as creep characteristics, rebound, and permanent set data, can be obtained through this test method. These data are useful for engineering designs. The test can also provide information on the behavior of the rock mass considering factors such as rock mass discontinuities, in situ stresses, and geologic properties. It is particularly valuable in the design of foundations of dams, support of underground excavations, piers, caissons, and stability of rock slopes.

The test method is cost-effective and less time-consuming compared to other deformability tests like radial jack or flexible plate tests, which require underground excavation and access. The dilatometer modulus obtained from this test can be correlated with moduli obtained from other methods, such as plate loading or radial jacking methods, allowing for substitution of more expensive in situ modulus tests.

Additionally, the test can provide a qualitative evaluation of a rock mass deformability before conducting larger scale deformability tests. Dilatometers are also valuable for rapid index logging of boreholes in jointed rocks where core recovery and laboratory testing may be inadequate. The standard specifies the unique pressurization and depressurization method of the dilatable membrane, which allows the use of the dilatometer at substantial depths and eliminates parasitic expansion of the tubing and pumping system.

It is important to note that the quality of results produced by this standard depends on the competence of the personnel performing the test and the suitability of the equipment and facilities used. Compliance with Practice D3740 is recommended to ensure reliable testing.