Measuring and testing – Vibration – Hardness or compliance
Patent
1982-07-23
1984-08-28
Gill, James J.
Measuring and testing
Vibration
Hardness or compliance
73594, 73 78, 404133, G01N 352, E02D 3046
Patent
active
044676522
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL AREA TO WHICH THE INVENTION RELATES
The present invention refers to a procedure and a device for measuring the degree of compaction achieved when compacting a foundation by means of a vibrating compaction tool. The compaction tool may be a roller with at least one cylindrical drum which is caused to oscillate by means of an eccentric weight rotating inside it.
BACKGROUND TO THE INVENTION AND TECHNICAL STANDPOINT
If the degree of compaction achieved with a vibrating compacting tool can be measured simply and continuously, and if the frequency and amplitude of the vibration of the compaction tool, as well as the speed with which the tool is moved across the foundation, can be varied, it would be possible to control the compaction tool with the aim of attaining optimal compaction. The danger of terminating compaction before a sufficient degree of compaction has been attained, or continuing compaction although a sufficient degree of compaction has already been attained, could be minimized. There has therefore long existed a need for a simple, inexpensive and reliable continuously measuring compaction degree meter for vibrating tools. In the patent literature there are many more or less different proposed designs of compaction degree meters. Among those that may be of interest as a background to the present invention, the ones described in British Pat. No. 1,372,567 and U.S. Pat. Nos. 3,599,543 and 4,103,554, for example, may be mentioned.
BRIEF DESCRIPTION AND SUMMARY OF THE INVENTION
The invention is based on sensing at least the vertical component of the movement of that part of the compaction tool which rests on the foundation and carries out compaction. If the compaction tool is moved across a flat, homogeneous, extremely soft and completely resilient foundation, the aforementioned vertical component of the movement would be a purely sinusoidal movement with respect to time for the majority of conventional compaction tools. On the other hand, if the compaction tool is moved back and forth across a stretch of the foundation consisting of soil or asphalt then at least initially a gradual increase in rigidity would be achieved in the foundation. Owing to the dynamic interaction between the compaction tool and the foundation, the aforementioned vertical movement would increasingly deviate in shape from the purely sinusoidal form with increasing rigidity of the foundation. This deviation from a sinusoidal form is--if all parameters in the compaction tool remain constant--directly related to the dynamic characteristics of the foundation and primarily its rigidity.
Through the aforementioned U.S. Pat. No. 4,103,554 it is already known that from the output signal of a transducer which senses the aforementioned movement it is possible to filter out sub-signals, the frequency of which essentially coincides with the basic frequency of the vibration and its harmonics. According to the aforementioned patents there exists a relationship between the amplitudes of these sub-signals and the degree of compaction.
Even though compaction meters according to U.S. Pat. No. 4,103,554 often work well, at least in certain connections, they do have certain disadvantages. For example, if it is desired to vary the vibration frequency of the compaction tool it is necessary to have either exchangeable band-pass filters or band-pass filters with controllable pass-band frequencies, which renders the meter more complicated and more expensive. Another drawback is that it is based on the concept that the basic frequency of the vibration is the lowest frequency in the movement performed by the vibrating and compacting part of the compaction tool.
The present invention is based on the insight that the relative magnitudes of the time intervals between at least certain successive passages through the zero point of the said movement, or signals from the transducer sensing the movement, display a relationship with the degree of compaction of the foundation. The invention is also based on the insight that the basic frequency of th
REFERENCES:
patent: 3599543 (1971-08-01), Kerridge
patent: 3775019 (1973-11-01), Konig, et al.
patent: 4103554 (1978-08-01), Thurner
Sandstrom Ake
Thurner AB Geodynamik H.
Geodynamik H. Thurner AB
Gill James J.
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