Measuring and testing – Testing by impact or shock – Accelerated or decelerated specimen
Patent
1993-06-15
1995-10-03
Chilcot, Jr., Richard E.
Measuring and testing
Testing by impact or shock
Accelerated or decelerated specimen
73 1204, G01N 300
Patent
active
054542642
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns an apparatus for measuring bearing capacity.
It is frequently necessary in connection with the structural courses of roads and streets, of various building foundations and also with the filling of excavations, to measure the bearing capacity of such surfaces. The bearing capacity of roads is commonly measured using an apparatus in which a load is applied on the structure to be measured by a load equivalent to the rear wheels of a lorry (Benkelman beam, Lacroix deflection measuring car), in the form of static loading with the aid of a rigid loading plate (the plate loading test) or in the form of dynamic loading on a rigid plate with the aid of a drop weight (drop weight apparatus).
Existing apparatus have significant drawbacks: they are big, expensive and unwieldy in use, and therefore bearing capacity measurements on smaller objects are not feasible. An object of this kind is encountered e.g. on roads and streets in filling work on various excavations, which could by filling one course at a time, with intervening compaction and measurement using a suitable bearing capacity measuring means, be filled right away in one go in a manner precluding subsequent formation of holes or presence of residual eminences.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the drawbacks mentioned above. It is a specific aim of the invention, to provide a novel, lightweight bearing capacity measuring apparatus which enables bearing capacity measurements to be made rapidly and with adequate accuracy, and which is easily transportable e.g. by carrying, from one point of measurement to another.
The bearing capacity measuring apparatus of the invention comprises a drop weight of suitable size, on the order of magnitude of e.g. 10 kg, holding and releasing members for the drop weight, and a measuring means for measuring the subsidence of the surface under measurement due to dropping the drop weight. As taught by the invention, the apparatus comprises a tubular body inside which a drop weight has been disposed to be substantially free to move in the direction of the tune. Furthermore, the lower end of the body is closed with a loading plate against which the drop weight is flung when it is allowed to drop freely within the body. As taught by the invention, the measuring means comprises an acceleration pick-up, for instance secured to the body, arranged to measure the movement of the tubular body of the apparatus during the impact. When an acceleration pick-up is used, the amount of movement, i.e., the magnitude of subsidence, is found by integrating the acceleration signal to give the velocity and, further, to give the displacement. It is possible of course to use a velocity pick-up or e.g. a seismic displacement pick-up instead of the acceleration pick-up.
The measuring means with its acceleration pick-up is advantageously placed in the upper part of the body, above the upper position of the drop weight, in which case the greater part of the measuring equipment consists of a hollow tube closed at both ends inside which the drop weight can move under gravity effect in one direction or the other, depending on the attitude of the tube.
It is advantageous to provide on the underside of the drop weight an elastic member, e.g. a rubber shock absorber, which prevents excessively abrupt and sharp impacts against the surface under measurement, whereby the impact will more closely correspond e.g. to those loads which cars cause on the road surface.
In an advantageous embodiment of the invention the holding and releasing member belonging in the upper part of the body consists of a magnet, its control, i.e., releasing of the drop weight, being arranged by an apparatus of an electric pulse which is delivered with a release push button external to the body. It is however equally possible to apply mechanical means for releasing/securing the drop weight.
When a magnet is used for releasing member, dropping the drop weight is accomplished with an electric p
REFERENCES:
patent: 3365929 (1965-01-01), Messner
patent: 3425263 (1969-02-01), Elliot et al.
patent: 3453862 (1969-07-01), Elliot et al.
patent: 3888108 (1975-06-01), Brands
Lampinen Anssi
Simomaa Kimmo
Biegel Ronald L.
Chilcot Jr. Richard E.
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