Measuring and testing – Specimen stress or strain – or testing by stress or strain... – Earth stresses
Reexamination Certificate
2000-05-02
2003-08-12
Moller, Richard A. (Department: 2856)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
Earth stresses
C073S594000
Reexamination Certificate
active
06604432
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the measurement of the properties of soil and more particularly to apparatus for measuring the shear modulus of soil to determine the extent of compaction.
As is understood, soil is an important building material. It serves as the base for virtually all pavements, tunnels and buildings, and thus, can be thought of as an element used in construction. In construction, soil will typically be specified to have certain minimal mechanical properties, e.g., dry density, resilient modulus and strength. While some testing can be conducted in a laboratory, e.g., to determine the suitability of a raw material or blend of materials, it is also typical to perform field tests to monitor both the soil selection or composition and also the compaction which affects mechanical properties of interest, typically a specified void ratio or resilient modulus.
The present field test procedures are typically sand cone or nuclear densitometric measurements. The sand cone requires substantial elapsed time while the nuclear densitometric measurement is often not considered sufficiently reliable and also raises radiation concerns. Accordingly, there exists a need for an ability to do rapid, low cost field tests which will reliably indicate the mechanical properties of the soil. As is understood by those skilled in the art, soil used to fill or level a construction site must be compacted, typically by the application of vibratory energy and weight, in order to obtain the requisite density and modulus. Typically, contractors are forced to over-compact soil as each of successive layers are added in order to insure that the result will meet the requisite specification when completed. The ability to quickly and reliably test soil properties could significantly reduce costs by eliminating the practice of over-compacting so as to provide a large margin over the specification.
While it has previously been proposed to measure soil properties by dynamic impedance measurements, no such prior system has found acceptance since the readings have been found to be inconsistent and not generally repeatable.
Among the several objects of the present invention may be noted the provision of novel apparatus for the insitu measurement of soil properties; the provision of such apparatus which will allow accurate measurement of the shear modulus of a surface layer of soil; the provision of such apparatus which provides accurate and repeatable measurements; the provision of such apparatus which will provide measurements reliably indicative of the state of compaction of soil; the provision of such apparatus which may be easily and quickly operated; the provision of such apparatus which can be easily transported to a construction site and easily moved between successive measurement positions at the site; the provision of such apparatus which is highly reliable and is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.
SUMMARY OF THE INVENTION
The apparatus of the present invention is adapted for the in-situ measurement of the shear modulus of soil and employs a contact foot for engaging a defined area of a region of soil to be measured. A pre-selectable downward bias force is applied to the contact foot which is designed to minimize variability in the foot's coupling to soil surfaces which typically are not perfectly flat, uniform, or which lack cohesion. A drive transducer is provided for shaking the contact foot vertically in response to drive signals applied thereto, preferably through a calibrated spring. Sensing transducers detect the force applied to the foot and the movement or acceleration of the foot and generate corresponding first and second output signals. The drive transducer is preferably driven by an a.c. drive signal which progressively varies in frequency over a pre-selected band with the rate of change also varying with frequency so that, for constant force amplitude, the force spectral content is greater at frequencies which would otherwise have a poorer signal-to-noise ratio, typically the lower frequencies. The in-phase component of the second output signal is analyzed in relation to the first output signal to obtain a measurement which is representative of the shear modulus.
REFERENCES:
patent: 1871756 (1932-08-01), Spath
patent: 3224253 (1965-12-01), McKay
patent: 3362216 (1968-01-01), Hardin et al.
patent: 3427877 (1969-02-01), Swift et al.
patent: 3481183 (1969-12-01), Swift
patent: 3643498 (1972-02-01), Hardin
patent: RE27875 (1974-01-01), Swift
patent: 3795286 (1974-03-01), Meyer
patent: 3813929 (1974-06-01), Hardin et al.
patent: 3863202 (1975-01-01), Landrum, Jr.
patent: 3924451 (1975-12-01), Drnevich
patent: 3946598 (1976-03-01), Towne et al.
patent: 4127351 (1978-11-01), Vural
patent: 4149253 (1979-04-01), Paar et al.
patent: 4348901 (1982-09-01), Vural et al.
patent: 4382384 (1983-05-01), Mitchell et al.
patent: 4445378 (1984-05-01), Zuckerwar
patent: 4467652 (1984-08-01), Thurner AB et al.
patent: 4594899 (1986-06-01), Henke et al.
patent: 4655082 (1987-04-01), Peterson
patent: 4738138 (1988-04-01), Redman-White
patent: 4750157 (1988-06-01), Shei
patent: 4912979 (1990-04-01), Sondergeld et al.
patent: 4918988 (1990-04-01), Ebihara et al.
patent: 4995008 (1991-02-01), Hornbostel et al.
patent: 5105650 (1992-04-01), Atkinson et al.
patent: 5398215 (1995-03-01), Sinha et al.
Berkman Frank
Hamblen William R.
Watters Bill
BBN Corporation
Moller Richard A.
Suchyta Leonard Charles
Weixel James K.
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