Measuring and testing – Hardness – By penetrator or indentor
Reexamination Certificate
2000-06-14
2001-06-12
Williams, Hezron (Department: 2856)
Measuring and testing
Hardness
By penetrator or indentor
C073S078000, C073S081000, C073S784000, C073S594000
Reexamination Certificate
active
06244102
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process and a system for examination and optimal compaction of single- or multi-layered soil embankments before constructing roads, railways and the like.
BACKGROUND OF THE INVENTION
A number of systems are known in the prior art which are capable of compacting soil during construction of automobile roads, railroads, airfields, etc. The proper compaction of the soil base is intended to ensure that the mentioned constructions will reliably withstand loads of various kinds, including non-uniform, non-periodic and extremely high surface pressures. Methods and systems for evaluating soil compaction are also known, but generally, they are only capable of evaluating the compaction of an uppermost layer in a soil base. Further, even for the uppermost layer in a soil base, these methods are not capable of deriving both the compaction and the thickness of the single layer. Where these methods and systems work with compaction machines, they also cannot control the depth at which the compaction will take place.
U.S. Pat. No. 5,426,972 describes a method and an apparatus for determining whether soil is satisfactorily compacted. An operator delivers impact energy to the soil, and the amount of impact energy transmitted through the soil is repeatedly sensed and stored. A modeling formula, which approximates the variation of the stored amounts of impact energy, is used to generate current and target values for the level of compaction; if the current value equals or exceeds the target value, the soil is considered to be satisfactorily compacted. The target value is considered to be one common parameter of the soil regardless whether it comprises many different layers.
SU 717623 teaches a method of controlling the degree of compaction of soil embankments by transmitting into the embankment a vibratory signal with an adjustable frequency close to its calculated resonant frequency and estimating the compaction degree based on the real resonant frequency of the soil.
Commercially available modern systems for soil compaction are manufactured by a widely known German company BOMAG and a Swedish company GEODYNAMIK and are adapted for continuously measuring in situ the degree of compaction of a layer currently undergoing treatment, namely detecting the condition of the upper layer of the construction. Such systems are suitable for successively (i.e. layer by layer) forming the multi-layered base for a road or the like.
However, if any multi-layered base already exists, no means for examining the compaction degree thereof are available in these systems. It should be emphasized that constructing a road or the like on a non-explored and/or improperly compacted base is likely to result in serious problems during further use of the road.
An approach to the compaction of existing multi-layered soils is suggested in SU 763506, which is incorporated herein by reference. According to the approach described therein, different layers of any existing soil base which are exposed to vibrations created by any particular compaction instrument, can be represented as a number of differential equations reflecting free oscillation of a mechanical system disposed between the compaction instrument and the immovable bottom of the base, wherein each of the equations has its own static and dynamic parameters reflecting the layer's characteristics. The method suggests generating and solving a system of equations for a particular multi-layer base, for determining resonant frequencies of different layers of the base, and further performing the compaction of the base using the minimal resonant frequency which has been determined for the system, thus obtaining the maximal deformation and compaction of the soil.
However, it has been found and proven by the inventor that compacting each and every layer of the base maximally may not always produce optimal compaction results.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and an appropriate system for effective soil compaction having improved performance over hitherto-proposed systems. Other aspects of the invention concern a method of computerized examination of the existing soil base and a system for accomplishing the mentioned methods. A further object of the present invention is to provide a method for evaluating the compaction of a soil base using a vibrator compaction device.
In the description, the term “layer” is used in the meaning of any kind of geological or artificially created massive body of soil, rock, pebble, limestone, sand, clay, waste (compacted or non-compacted), etc. which is generally horizontally disposed on top of an adjacent layer in an existing or artificially created base or embankment. The term “hard bottom layer” should be understood as an immovable ground layer, such as a rock bed.
There is thus provided, in accordance with an additional preferred embodiment of the present invention, a method for evaluating the compaction, by means of a vibrator compaction device having mass M
vib
and a bearing area F, of a preselected soil layer, for which a predetermined degree of compaction is desired, at a preselected depth l in a soil base having at least one layer disposed between an exterior upper surface and a hard bottom layer, thereby defining a vibrator-soil-base system, which includes the steps of:
evaluating a desired volumetric mass &ggr;
st
of the preselected soil layer corresponding to the desired degree of compaction, which may be performed by measurement or by calculation using standard soil data;
calculating a mass per unit area m
soil
of the preselected soil layer as a function of the desired volumetric mass, using the formula:
m
soil
=&ggr;
st
*l;
calculating the effective vibrating mass M of the vibrator-soil-base system as a function of the mass per unit area of the preselected soil layer and the mass of the vibrator, using the formula:
M=M
vib
+⅓(
m
soil
*F
);
determining the natural oscillation frequency &ohgr;
o
of the vibrator-soil-base system when the preselected soil layer is at the desired degree of compaction as a function of its effective mass, using the formula:
&ohgr;
o
=(
C/M
).
wherein C is the stiffness coefficient of the soil of the preselected soil layer;
measuring the forced oscillation frequency &ohgr;
res
of the vibrator-soil-base system for frequencies close to the natural oscillation frequency &ohgr;
o
;
deriving the volumetric mass &ggr; of the preselected soil layer as a function of the desired volumetric mass of the preselected soil layer and of the natural oscillation frequency and the forced oscillation frequency of the vibrator-soil-base system, using the formula:
&ggr;=&ggr;
st
*(&ohgr;
res
/&ohgr;
o
)
2
; and
determining compaction degree K of the compacted preselected soil layer.
The step of determining the compaction degree K of the compacted preselected soil layer may be performed using the formula:
K=&ggr;/&ggr;
st
;
or alternatively, if suitable measurements have been taken and the required parameters are known, using the formula:
K=(&ohgr;
res
/&ohgr;
o
)
2
.
Operation of the dynamic and the technological optimization models will be further explained in the specific description of the preferred embodiments.
REFERENCES:
patent: 3323352 (1967-06-01), Branson
patent: 3778177 (1973-12-01), Haker et al.
patent: 4348901 (1982-09-01), Vural et al.
patent: 5105650 (1992-04-01), Atkinson et al.
patent: 5337601 (1994-08-01), Becker et al.
patent: 5426972 (1995-06-01), Heirtzler et al.
patent: 5952561 (1999-09-01), Jaselskis et al.
patent: 717623 (1980-02-01), None
patent: 763506 (1980-09-01), None
Browdy & Neimark
Dynasens Ltd.
Loo Dennis
Williams Hezron
LandOfFree
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