ASTM D8153-22

5.1.1The test method described is useful as a rapid, nondestructive technique for bulk measurements of the water mass per unit volume of soil and soil-aggregate which may, in conjunction with an independent bulk density determination, be used in the determination of dry density.

5.1.2The test method is used for quality control and acceptance testing of compacted soil and soil-aggregate mixtures as used in construction and also for research and development. The nondestructive nature allows repetitive measurements at a single test location and statistical analysis of the results.

5.1.3Volumetric Water ContentThe fundamental assumptions inherent in the test method are that the dielectric constants value measured by the system in a given test site composed of soil or soil-aggregate are directly correlated to the volumetric water content of the soil or soil-aggregate, and that the material is homogeneous. (See 6, Interferences.)

1.1.1For limitations see Section 6 on Interferences.

1.2.1The probe circuit creates an oscillating electric field in the soil. Changes in the dielectric permittivity of the soil are indicated by changes in the circuits operating frequency. Since water has a much higher dielectric constant (80) than the surrounding soil (typically around 4), the water content can be related by a mathematical function to the change in dielectric permittivity, and, consequently, the changes in the circuits operating frequency.

1.2.2The construction, deployment, and operating principle of the device described in this test method differ from other methods that measure the dielectric constant, bulk electrical conductivity, complex impedance, or electromagnetic impedance (see Test Methods D6780/D6780M, D7698, and D7830/D7830M) of the soil and relate the results to water mass per unit volume and/or water content.

1.2.3The water content of the soil measured by the permittivity probe is the volumetric water content, expressed as the ratio of the volume of water to the total volume occupied by the soil. This quantity is often converted, and displayed, by the probe in units of mass of water per volume of soil, or water mass per unit volume. This conversion is performed by multiplying the water content (in volume of water per volume of soil) by the density of water.

1.5.1For purposes of comparing, a measured or calculated value(s) with specified limits, the measured or calculated value(s) shall be rounded to the nearest decimal or significant digits in the specified limits.

1.5.2The procedures used to specify how data are collected/recorded and calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that should generally be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the users objectives; and it is common practice to increase or reduce significant digits of reported data to commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.