Monitoring of soil

Details Monitoring of soil Monitoring of soil

1992-09-29

1995-04-04

Noland, Tom

Measuring and testing

Testing by impact or shock

Specimen impactor detail

73594, 73866, G01N 2918, G01N 3324

Patent

active

054026679

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to monitoring systems and more particularly to methods and apparatus for monitoring soil such as compaction of backfill for utility excavations and the like.
Excavations such as utility trenches, foundations and the like are generally backfilled in layers, termed lifts, with each lift of backfill material be compacted prior to the addition of the next lift. If backfill material is improperly compacted, or if an unsuitable backfill material is used, the backfilled excavation may subside. Subsidence in foundations, roadways or other structures due to improper backfill compaction can necessitate costly and disruptive repairs.
In the proper compaction of backfill in an excavation, each backfill lift should be properly compacted prior to the addition of the next lift; and after all lifts are in place and compacted, the complete backfilled excavation should be proofed to verify that there are no voids, soil bridges, or layers that are not fully compacted. Current monitoring methods such as drop hammer penetration probes, nuclear densitometry and the sand cone method are typically used only to check each lift for proper compaction, and such methods are expensive, time-consuming and cannot be performed in real time.
Tests for acceptable compaction of soil material such as Proctor or California Bearing Ratio (CBR) require specialized equipment and significant amounts of time to perform, and accordingly are usually performed in a laboratory rather than in the field.


SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, there is provided apparatus for monitoring the compaction of soil material in a defined region such as a chamber or an excavation that includes hammer structure for delivering impact energy to soil material in the defined region, sensor structure for disposition at the bottom of the defined region that includes a transducer for developing an electric signal in response to energy transmitted through soil material from the hammer structure, and a control module responsive to electric signals from the sensor structure for providing an indication of the quality of compaction of soil material in the defined region.
In a preferred embodiment for providing an indication of the quality of compaction of backfill material in an excavation, the apparatus includes a sensor module with a compliant base member of area at least about one-half the area of the base of the excavation to be backfilled. The base member is of electrically-insulating material such as rubber, synthetic rubber, paper, styrofoam or similar polymeric material on which a plurality of piezoelectric transducers are secured in spaced array, together with an overlying protective sheet member, an array of first piezoelectric transducers disposed along the perimeter of the base member being connected in parallel to a first output conductor and a second piezoelectric transducer generally at the center of the base member being connected to a second output conductor, the output conductors being connected to the control module for transmitting electrical signals to the control module.
Supplemental proofing apparatus includes a hammer and a third piezoelectric transducer for placement on the top of the backfilled excavation. The control module includes accumulator circuitry for accumulating output signals from the sensor array for providing an indication of the quality of compaction of each lift of backfill material in the excavation, and verifying circuitry responsive to the second and third transducers for providing a transit time (dependent on seismic velocity) indication of impact energy propagation between the third transducer at the top of the backfill material and the second transducer at the bottom of the excavation.
In a particular embodiment, the control module includes peak detection circuitry for sampling electrical signals received from the array of first piezoelectric transducers, circuitry for storing indications of the peak amplitude of signals received during a sequ

REFERENCES:
patent: Re31195 (1983-04-01), Thurner
patent: 2284707 (1942-06-01), Wilson
patent: 2336500 (1943-12-01), Osterberg
patent: 2624251 (1953-01-01), Porter
patent: 3286514 (1966-11-01), Anderson
patent: 3372577 (1968-03-01), Bates et al.
patent: 3456496 (1969-07-01), Heller
patent: 3492859 (1970-02-01), Dodge
patent: 3529468 (1970-09-01), Carlson
patent: 3537541 (1970-11-01), Desai et al.
patent: 3641811 (1972-02-01), Gnaedinger, Jr. et al.
patent: 3998090 (1976-12-01), Wislocki
patent: 4149253 (1979-04-01), Paar et al.
patent: 4348901 (1982-09-01), Vural et al.
patent: 4398427 (1983-08-01), Pan
patent: 4495434 (1985-01-01), Diepers et al.
patent: 4524626 (1985-06-01), Pabst et al.
patent: 4543820 (1985-10-01), Handy et al.
patent: 4590802 (1986-05-01), Furmanski
patent: 4614110 (1986-09-01), Osterberg
patent: 4662226 (1987-05-01), Wang
patent: 4802371 (1989-02-01), Calderara et al.
patent: 4856318 (1989-08-01), Hogan et al.
patent: 5024090 (1991-06-01), Pettigrew et al.
patent: 5054490 (1991-10-01), Rossmon et al.
patent: 5105650 (1992-04-01), Atkinson et al.
patent: 5247937 (1993-09-01), Ophir et al.
Database WPI, Week 8842, Derwent Publications Ltd., London, GB; AN 88-299228 & SU-A-1 388 799 (Ind Build Res Inst) 15 Apr. 1988 (Abstract).
Database WPI, Week 8926, Derwent Publications Ltd., London, GB; AN 89-191447 & SU-A-1 449 864 (Urals Rail Transp Inst) 7 Jan. 1989, (Abstract).

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