Standard Test Method for Determining the In Situ Rock Deformation Modulus and Other Associated Rock Properties Using a Flexible Volumetric Dilatometer

Importancia y uso:

5.1 The dilatometer test is usually performed in vertical boreholes. It can be used in inclined or horizontal holes, but the probe would drag along the borehole wall.

5.2 Deformation modulus of rock, creep characteristics, rebound, and permanent set data is obtained and is useful for engineering designs.

5.3 The rock mass discontinuities, in situ stresses, geologic history, crystallography, texture, fabric, and other factors will determine the rock mass properties that laboratory size tests alone may not be able to measure and that the dilatometer test may be better able to measure.

5.4 Determination of rock mass deformability yields a critical parameter in the design of foundations of dams, support of underground excavations, piers, caissons, and stability of rock slopes.

Note 2: Although a rock mass behaves in an anisotropic and inhomogeneous manner, the calculations for a rock mass deformation modulus are based on assumptions of elasticity and homogeneity. However, they still render results that are practical, simple, usable, and not significantly different from those obtained using inhomogeneity and inelasticity.

Note 3: The existing in situ stresses can only be estimated by in situ tests on the rock mass, such as this or other tests.

5.5 In situ tests such as this one provides general information regarding rock mass behavior. Dilatometer tests are advised when designing and constructing specific structures.

5.6 Dilatometer tests can be performed at a reasonable cost and effort. Dilatometer tests are also less expensive and time-consuming compared to other deformability tests like radial jack or flexible plate tests that require underground excavation and access too.

5.7 Dilatometer modulus can be correlated with the moduli obtained by other methods (for example, the plate loading or radial jacking methods). The correlated dilatometer modulus can then be used instead of other more expensive in situ modulus tests.

5.8 Dilatometer tests can provide a qualitative evaluation of a rock mass deformability before performing a large scale deformability test such as a radial jack test.

5.9 Dilatometers are valuable for rapid index logging of boreholes in jointed rocks that yield poor core recovery and inadequate specimens for laboratory testing.

5.10 Pressurization and depressurization of the dilatable membrane in this standard are unique. This is done immediately upstream of the dilatable membrane by a dual-action piston actuated from a manual pump at the surface. This configuration allows the use of the dilatometer at substantial depths and eliminates the parasitic expansion of the tubing and pumping system and forces the membrane to collapse completely regardless of if the drill hole column has fluid or not.

5.11 The results of dilatometer tests may be used to check against the serviceability limit state of spread foundations on rocks through a deformation analysis.

5.12 When performing a deformation analysis the Young's modulus, E, may be taken equal to E_d on the assumption that the rock is linearly elastic and isotropic.

Note 4: 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 facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.

Subcomité:

D18.12

Volúmen:

04.09

Número ICS:

93.020 (Earthworks. Excavations. Foundation construction. Underground works)

Palabras clave:

in situ; borehole; cyclic testing; fracking; rock deformation;