Electricity: measuring and testing – Of geophysical surface or subsurface in situ – Using electrode arrays – circuits – structure – or supports
Reexamination Certificate
2000-03-16
2002-04-30
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
Using electrode arrays, circuits, structure, or supports
C324S323000, C324S717000, C324S376000, C324S674000, C073S152060
Reexamination Certificate
active
06380745
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to electrical geophysical methods and apparatus for determining the density of porous materials and establishing the porous material geo-electric constants that relate to U.S. Pat. No. 5,861,751.
The objective of the invention is to provide geo-electric density data for construction material that may be used in conjunction with a field method described in U.S. Pat. No. 5,861,751. The combined technique is used for construction quality control and quality assurance (QC/QA), as well as field documentation for submittal to a regulating authority.
Federal, state, and/or local government regulations require a QC/QA program be implemented during the construction phase of building projects that involve compacted fill earthen material. The QC/QA program involves on-site technical or engineering staff that monitor construction activities and prepare certified engineering reports as to the quality of the facility construction compared to the facility design.
In highway construction the in-situ density design specifications are typically dictated by engineering requirements or state/federal regulations. An example of a regulation that calls for a prescriptive compacted fill specification is the Nevada Department of Transportation, Standard Specifications for Road and Bridge Construction, Section 305 Roadbed Modification Subpart 305.03.05. These regulations contain minimum design criteria for the construction of a highway roadbed. The regulation states:
“After the materials have been satisfactorily mixed, the mixture shall be bladed and compacted to a ninety-five (95) percent relative maximum density as determined by Test Method No. Nev. T101. Test Method No. Nev. T102 or T103 may be used to determine the in-place density Test method to be determined by the Engineer.”
BACKGROUND OF THE INVENTION
General: Existing Technologies for Measuring Density of a Porous Medium
The state-of-the art methods for measuring density include, but are not limited to, the Standard Test Method for Moisture-Density Relations of Soil-Aggregate Mixtures Using 10-lb (4.54-kg) Rammer and 18-in. (457-mm) Drop, ASTM 1557-78; or, Standard Test Method for Moisture-Density Relations of Soil-Aggregate Mixtures Using 4.4 lb (2.49-kg) Rammer and 12-in (305-mm) Drop, ASTM D698-78; or ASTM D 2922-81; or ASTM D1556. The existing technologies do not use electrical geophysical methods as a part of the operations and calculations.
Related Patents
U.S. Pat. No. 5,861,751 issued Jan. 19, 1999. The title of this patent is: ELECTRICAL GEOPHYSICAL METHODS AND APPARATUS FOR DETERMINING THE IN-SITU DENSITY OF POROUS MATERIAL. D. M. Anderson and W. J. Ehni are co-inventors for the above-mentioned patent.
U.S. Pat. No. 5,861,750 issued Jan. 19, 1999. The title of this patent is: GEOPHYSICAL METHODS AND APPARATUS FOR DETERMINING THE HYDRAULIC CONDUCTIVITY OF POROUS MATERIALS, D. M. Anderson and W. J. Ehni are co-inventors for the above-mentioned patent. The apparatus and method of acquiring the electrical resistivity field data for determining relative in-situ density of porous material uses portions of the prior art.
Applicable Background Art
Development of an electrical geophysical method and apparatus for determining the in-situ density of porous materials at the earth's surface utilizes two primary principles of applied geophysics. Both of the geophysical principals had their origin in the petroleum industry and were not considered, assessed, examined, or adapted for use for geotechnical engineering until Anderson and Ehni recognized their potential, conducted research to assess adaptation of the principals, and developed the invention that is presented herein.
The first geophysical principal is based on work by Conrad and Marcel Schlumberger (1930) who developed a system of measuring the resistivity of surface rocks with electrodes deployed on the surface. The electrode spacing was typically 10's of 100's of feet and the objective of the investigation was to assess rock formation contact zones or geological structures, such as faulting and folding in deep subsurface zones. They used the subsurface zone variations in resistivity to interpret gross geologic structural phenomena. They later applied this technology to evaluating well bores drilled for petroleum exploration.
The second geophysical principal uses G. E. Archie's 1941 work. Archie presented his work in 1942 in a paper entitled
The Electrical Resistivity Log as an Aid in Determining Some Reservoir Characteristics
. Archie determined porosities of various materials using resistivity measurements. Mathematical formulas that G. E. Archie derived, and other relevant mathematical formulas that have been adapted for use in the invention, are outlined in the DESCRIPTION OF THE PREFERRED EMBODIMENTS.
By combining these two petroleum exploration and production industries principles with modified geotechnical engineering equations for relative density, a new, accurate method has been developed for determining the geoelectric constants of a standard sample of porous materials as geo-electric tested ASTM 698.
Earlier researchers never provided a process or method for developing lab data that relates electrical resistivity to soil density because their focus was directed toward physical soil characteristics, not requiring electrical data for geotechnical engineering measurements and calculations. U.S. Pat. No. 5,861,751 combines the art of electrical geophysics with geotechnical engineering. Prior geophysical art includes the Wenner Electrode Array, which applies the Schlumberger theory by utilizing four electrodes that are spaced on the surface of the earth at equal distances. The distance between each electrode is commonly referred to as the “a” spacing. In general, the depth of investigation is directly related to the electrode separation. J. J. Jakosky, (1950), discusses the depth of investigation, and notes that the theoretical depth of investigation should be equal to the “a” spacing in a Wenner Array for a homogeneous medium.
In other electrode arrays, the depth of investigation can be as low as 20% of the length of the current electrode spacing from one end of the array to the other. The objective of applying the Wenner Electrode Array was to assess gross geologic features in the subsurface. The surface spacing for this purpose is 10's of 100's of feet, and the analysis yields an understanding of geologic structures in the subsurface. The key element in a typical investigation using the Wenner Electrode Array is the variation in the resistivity numbers. A single raw number alone would not allow interpretation of geologic structural phenomena, and is considered useless when out of context. A single resistivity number would not enable the assessment of geologic structural changes in the subsurface.
Anderson and Ehni chose a relatively small distance for the electrode separation in the Wenner Array installed in a nonconductive standard density mold. The objective of Anderson and Ehni's work is to establish a set of geo-electric constants that are unique to a standard sample of material (SSM). These geo-electric constants that were established for the SSM are then used to calculate the in-situ density of the geotechnically similar porous material under test (PMUT). Using unprecedented short electrode separation installed in a standard density mold, Anderson and Ehni were able to measure a unique set of geo-electric properties of soil products.
In-situ density calculations using electrical geophysics were developed by Anderson and Ehni in 1996 and covered under U.S. Pat. No. 5,861,751. They use resistivity measurements and porosity calculations as developed by G. E. Archie, combined with a formation factor or constant. These formation and/or solution factors are empirically derived through experimentation and testing for repeatability.
The following professional papers were considered in the development of the present inventions:
Archie, G. E., The Electrical Resistivity Log as an Aid in Determinin
Anderson Dennis M.
Ehni William J.
Brown Glenn W.
Hamdan Wasseem H.
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