Ground vibration properties detection method and equipment thereof

The present disclosure concerns a ground vibration properties detection method by generating a specified vibration load equal to the actual load generated by traffic vehicles on a paved road or by generating a specified vibration load corresponding to a seismic intensity of earthquake on a ground and measuring the vibration load as a vibration level induced by the vibration load and equipment thereof.

BACKGROUND OF THE INVENTION 
1. Field of the invention 
This invention relates to a detection method of vibration properties of a 
ground, for instance, a road pavement construction or a cushion course of 
an architecture construction foundation and equipment thereof. 
2. Description of the Prior Art 
Design of a road pavement or an evaluation method after the road pavement 
constructed has been based on the number of vehicles passed on the road or 
an impact load which is not the real vibration load but an assumption. 
The design of a pavement is being made as per the methods shown in "Asphalt 
Pavement Guideline" and "Cement Concrete Pavement Guideline" published by 
The Japan Highway Association. 
Basically, a destructive load to a road is given in terms of the member of 
passed heavy vehicles each giving 10,000 times the action by an ordinary 
car and the road load classes (Designed Traffic Classification) are 
classified as shown in Table 1 (L to D Traffics). 
Generally, the pavement thickness is determined by a graph (allegedly based 
on the result of AASHO Road Test conducted in California approximately 50 
years ago) experimentally prepared from the relationship between the 
classification and the supporting force (K.sub.30 value of CBR and Flat 
Plate Loading Test) of the road bed (base ground supporting the pavement). 
TABLE 1 
______________________________________ 
Designed Traffic Classification and the Corresponding 
Designed Wheel Loads 
Designed Traffic 
Heavy Vehicles Designed Wheel 
Class Traffic (No./Day) 
Load 
______________________________________ 
L Traffic Below 100 2 tons 
A Traffic Above 100 Below 250 
3 tons 
B Traffic Above 250 Below 1,000 
5 tons 
C Traffic Above 1,000 Below 3,000 
8 tons 
D Traffic Above 3,000 12 tons 
______________________________________ 
The designed wheel loads in Table 1 were obtained by conversions calculated 
from the total traffic loads into a wheel load based on which it is 
theoretically possible to design an economical pavement structure suitable 
for a road bed supporting force by calculating physically the deflection 
of or strain generated by asphalt or concrete plate. However, the 
supporting force is not always uniform over the traffic road and the 
properties assumed for the calculation of the pavement construction 
materials do not conform to the actual values. 
The wheel loads are supported 3-dimensionally and the deflection is 
variable depending on the part or the distance from the loading point. 
Further the calculation must be made under such a difficult condition as 
continuous vibration load. Therefore, if no confirmation is made by 
experiment, any values obtained even from such a complex calculation 
should be adapted only for reference. 
The vibration damping function of pavement is variable depending on the 
materals of the ground including improved road bed and the construction 
technology and is an important factor for the counter-measures to traffic 
road vibration. 
The vibration damping function can be evaluated by giving a specified 
dynamic load to a road surface and by measuring each vibration level at 
each specified point spaced from the vibration origin. Conventional 
methods for measuring vibration by giving an impact to road surface are as 
follows: 
The Japan Highway Public Corporation uses a method having a large dump 
truck loaded full of mud run onto a pile of square lumbers and stoping the 
truck to drop the tires from the lumbers to give an impact to the road 
surface and measuring the vibration thereof. 
FWD pavement checking system (Falling Weight Deflectometer (FWD) Deflection 
Measuring Unit) is to give an impact to the surface of the pavement by 
dropping a heavy weight by means of a load plate of 30 cm diameter and 
measure the deflection generated on the road surface by a sensor located 
on a half diameter from the load center to learn the properties of the 
pavement construction. The method of giving an impact by dropping the 
tires from the square lumbers on the road surface is only a single impact 
load and is not the number of vehicles passed (not a load) or the actual 
vibration load for designing the road pavement or for assumption of the 
evaluation after the pavement. Therefore, there is a problem that the 
loading load is rather less than the designed wheel load and is not the 
actual traffic load given by continuous vibration load. The single load is 
unable to give a load corresponding to the designed wheel load shown in 
Table 1 and is also unable to generate a vibration load identical to the 
actual load generated by the traffic vehicles. In addition, the traffic 
vehicles are given with a forced vibration resulted from uneven road 
surface and as the reaction the vibration and the impact load are 
transferred to the road surface through the tires and a large dynamically 
added load is generated. This is the origin of the traffic vibration on 
the roads. 
The FWD impact load of FWD Deflection Measuring Unit described above is 
against a static load (ground contact pressure) and not for a dynamically 
added load. 
In the case that the ground is a cushion course of architecture 
construction foundation, there was no way to generate a vibration level 
corresponding to an earthquake amplitude and therefore it was impossible 
to detect the actual vibration properties. 
SUMMARY OF THE INVENTION 
An objective of this invention is to provide a method of detecting a 
vibration properties of ground by generating a specified vibration load 
equal to the actual load generated by traffic vehicles on the ground of a 
road pavement construction and by generating a vibration load 
corresponding to the seismic intensity of earthquake and detect the 
vibration level induced by the vibration load on the ground of a cushion 
course of architecture construction foundation and equipment thereof. 
In order to meet the above objective, the present invention is, in the case 
that the ground is a road pavement construction, to drop vertically a 
heavy weight having a specified head on a road pavement once or 
continuously every unit time to give a dynamically added load 
corresponding to the designed wheel load generated by the traffic vehicles 
on a standard flat road surface and to measure the vibration generated 
therefrom as a vibration level at each distance from the vibration origin. 
In the case that the ground is a cushion course of architecture 
construction foundation, the heavy weight having a specified height is 
dropped vertically on the ground once or continuously every unit time to 
give to the ground a load corresponding to a seismic intensity of 
earthquake and to measure the vibration generated therefrom as a vibration 
level at each distance from the vibration origin. The equipment of 
performing the above method comprises a vibrator and a measuring unit of 
vibration level, the vibrator comprising a driving motor, a driving 
sprocket wheel mounted on output shaft of the driving motor, a driven 
sprocket provided in spaced relationship with the driving sprocket, a 
first roller chain provided between the driving sprocket and the driven 
sprocket, a driving sprocket wheel lifting a heavy weight transmitting a 
rotating force of the driven sprocket, a driven sprocket wheel mounted on 
the upper portion of the sprocket wheel lifting the heavy weight lifting 
the heavy weight, a second roller chain provided between the driving 
sprocket wheel lifting the heavy weight and the driven sprocket wheel 
lifting the heavy weight, an electro-magnetic clutch provided between the 
driven sprocket wheel and the driving sprocket wheel lifting the heavy 
weight to put off or put on the rotating force by a signal from each limit 
switch at a predetermined upper position and lower position, a wire rope 
fastening fitting mounted on the second roller chain and traveling 
vertically between the lower area of the driving sprocket wheel lifting 
the heavy weight and the upper area of the driven sprocket wheel lifting 
the heavy weight, a lifting rope an end of which is connected with the 
wire rope fastening fitting and hanging via a wire rope guide roller and a 
heavy weight hung on the other end of the lifting wire rope. Said 
vibration level measuring unit is comprised of a sensor to detect the 
vibration level at each distance from a place where the heavy weight of 
the vibration generating unit is dropped, a vibration level meter 
connected with the sensor to measure the vibration level and a vibration 
level recorder connected with the vibration level meter to record the 
vibration level measured.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of this invention are described hereunder with 
reference to the accompanying drawings: 
Skeltons of a vibration generating unit 100 and a vibration level measuring 
unit 200 according to the present invention are shown in FIG. 1(a) and 
FIG. 1(b) to describe an evaluation method of vibration damping function 
of pavement. 
The construction of the vibration generating unit 100 is shown in FIG. 
1(a), FIG. 2 and FIG. 3. A supporting stand 1 is positioned on a paved 
road surface 3 by means of at least three supporting legs 2, 2 and 2 
having an installation level adjustable cushion each provided on bottom 
thereof. A driving motor M is mounted on the middle of the supporting 
stand 1 and a driving sprocket wheel 11 is installed on output shaft 
thereof. A driven sprocket wheel 12 is provided underneath the driving 
sprocket wheel 11 and a first roller chain 14 is provided between both 
sprocket wheels 11 and 12. The output of the driving motor M is 
transferred to the driven sprocket wheel 12, then to the driving sprocket 
wheel 16 lifting the heavy weight via a power transfer sprocket wheel 13 
and an auxiliary roller chain 15. An electromagnetic clutch 10 is provided 
between a shaft 12a of the driven sprocket wheel 12 and a shaft 13 of a 
shaft 13a of the power transfer sprocket wheel 13 to turn off or turn on 
the coupling between both shafts 12a and 13a. 
A driven sprocket wheel 17 for lifting the heavy weight is provided above 
the driving sprocket wheel for lifting the heavy weight and a second 
roller chain 18 is provided between both sprocket wheels 16 and 17. 
A wire rope fastening fitting 20 is mounted on the second roller chian 18 
at a specified position and one end of the lifting wire 22 is tied with 
the wire rope fastening fitting 20. The lifting wire rope 22 is hung by 
means of wire rope guide rollers 24 and 24' with a heavy weight 5 hung 
from the other end of the rope. The wire rope fastening fitting 20, which 
is mounted on the second roller chain 18, moves vertically between the 
lower area close to the driving sprocket wheel 16 for lifting the heavy 
weight and the upper area close to the driven sprocket wheel 17 for 
lifting the heavy weight by the action of the electromagnetic clutch 10 
which transfers the driving force of the driving motor M in response to a 
signal from limit-switches 26 and 28 defining the lower limit and the 
upper limit as described hereunder. 
The electromagnetic clutch 10 is turned on when the heavy weight is to be 
lifted and is turned off from nearly starting of the heavy weight dropping 
until the next lifting thereof to generate a vibration force when dropped 
from a specified lifting height with a specified interval by regulating 
the times of the turning-on or turning-off. 
As shown in the enlarged view in FIG. 4 both sides of the heavy weight 5 
are provided with projected splines 5a and 5b. 
A heavy weight guide mechanism 30 having receiving slots 30a and 30b formed 
along the direction of heavy weight dropping is provided on the supporting 
stand 1 to secure a stable dropping of the heavy weight 5 with the 
projected splines 5a and 5b engaged in the receiving slots 30a and 30b 
respectively. A shock absorber 32 is provided on both sides around the 
lifting wire rope 22 above the wire rope fastening fitting 20 so that the 
lifting rope 22 may not be slackened by a shock of inertia expected to be 
caused when the heavy weight 5 is dropped on the ground. 
FIG. 5 shows the heavy weight 5 which is mounted with a load cell L by 
means of a plurality of fastening bolts 36 on the lower end thereof and a 
cylindrical inclusion part 42 is engaged thereon externally and a shock 
plate 38 is fastened underneath thereof by screwing into a screw-in 
portion 40 formed in the center of the load cell L. The output from the 
load cell L is taken as an electric signal and modulated to show on a 
digital display of the impact load of the heavy weight 5 on a strain type 
indicater 46 (refer to FIG. 1) for a sensor. 
FIG. 6(a) and FIG. 6(b) are the front elevation and the side elevation 
showing the structure of a base board 6 of the supporting stand 1 
respectively. The supporting stand is positioned on the paved road surface 
by means of at least 3 supporting legs 2, 2 and 2 having an installation 
level adjustable cushion, each provided on the bottom thereof. 
The supporting leg 2 is of an electric worm adjusting jack construction and 
a jack 50 shown in FIG. 7 and FIG. 8 is mounted on a frame (not shown) 
provided on the lower portion (3 points) of the supporting stand 1. The 
jack 50 is comprised of a 3-phase AC induction motor 52 the output shaft 
52a of which is mounted with a bevel gear 54 with which a level gear 58 
fastened on a shaft end of a worm gear 56 is engaged. The worm gear 56 is 
engaged with a worm wheel gear 60 as shown in FIG. 8 through which the 
supporting leg 2 is axially inserted. The worm wheel gear 60 is provided 
with an internal teeth 60a which is engaged with an elevating screwed 
shaft 2a of the supporting leg 2. Hence, revolution of the output shaft of 
the 3-phase AC induction motor transfers the output to the worm wheel gear 
60 via the worm gear 56 to move the supporting leg 2 vertically. 
As shown in FIG. 6(a) and FIG. 6(b) the supporting table is provided on the 
4 corners with a wheel mounting fitting 62 each on which a wheel is 
rotatably mounted. Each wheel mounting fitting 62 is connected with each 
other by means of a shaft 66 passing through therein and is axially 
rotatable with regard to the shaft 66 and a wheel 64 can be fastened 
either at the position indicated by a solid line or at the position 
indicated by a dotted line as shown in FIG. 6(a). 
This unit is operated by extending the supporting legs 2, 2, and 2 from the 
present position to position A as shown in FIG. 7 by means of the jack 50 
to float up the wheel 64 and the wheel mounting fitting 62 is swung up as 
indicated by arrow to inverse the wheel 64. Under this condition, the 
supporting legs 2, 2 and 2 are moved backward to the position B as shown 
in FIG. 7 to act the vibration. In additon to the supporting legs 2, 2 and 
2, manual auxiliary jacks 2' and 2' are installed on both sides 
symmetrically to make a 5-point supporting as indicated in FIG. 3 in order 
to secure the stability when the impact is given. 
After the evaluation test is completed with this equipment, the supporting 
legs 2, 2 and 2 are again extended to the position A by the jack 50 as 
shown in FIG. 7 to return the wheel 64 to the position shown by the solid 
line from the position on the dotted line. Then, the supporting legs 2, 2 
and 3 are moved backward by the jack 50 to the position C in FIG. 7 to 
land the wheel 64 and now this equipment can be moved freely on the paved 
road. 
As shown in FIG. 2, a longitudinal scale plate 70 is mounted on the front 
side of supporting stand 1 and a lower limit switch 26 is installed 
underneath thereof. A height adjusting chain 72 is provided in parallel to 
the scale plate 70 on which an upper limit switch 28 is installed for 
reading the position indicated by a pointer 70a on the scale plate 70. 
The height adjusting chain 72 is provided endlessly by means of guide rolls 
74a, 74b and 74c. The height of the upper limit switch 28 can be adjusted 
by turning a handle 76 rightward or leftward. The electromagnetic clutch 
10 transfers or shuts the driving force of the driving motor M by means of 
a signal from the lower or the upper limit switches 26 and 28. 
When a signal from the lower limit switch 25 is detected, the 
electromagnetic clutch 10 is turned on to connect a shaft 12a of the 
driven sprocket wheel 12 with a shaft 13a of the power driving sprocket 
wheel 13 to have the second roller chain 18 move the wire rope fastening 
fitting 20 downward from the upper area close to the sprocket wheel 16 for 
lifting the heavy weight and lift the heavy weight 5 by means of the 
lifting wire rope 22. When the heavy weight 5 is lifted to a specified 
height and the upper limit switch 28 works, the electromagnetic clutch 10 
is turned off and the driving force of the driving motor M is shut off to 
drop the heavy weight 5 freely. The lower limit switch 26 works just 
before the heavy weight 5 reaches the road surface and the above operation 
is repeated to put approximately one load per second on the road surface. 
A tachometer 80 is connected with a shaft end of the driven sprocket wheel 
17 for lifting the heavy weight 5 to measure the dropping height of the 
heavy weight 5 by converting the rotation angle of the driven sprocket 
wheel 17 to the lifting distance by means of an additional unit which is 
not shown. 
FIG. 9(a) and FIG. 9(b) are the top view and the sectional side elevation 
of the uneven road surface correction mechanism 90 respectively. The 
uneven road surface correction mechanism 90 has a larger diameter than 
that of the heavy weight 5 and comprises a cylindrical frame 92 the upper 
and lower ends of which are open and filled with a plasticized material 94 
and a sound absorbent 96 (synthetic fiber, etc.) is placed thereon. The 
frame 92 is placed so as to coincide its center with the center of the 
heavy weight 5. 
The plasticized material 94 is to absorb the undulation of the ground 
surface and flattens the working surface of the ground to which the 
vibrating force is acted. 
The frame 92 prevents the plasticized material 94 from deforming and 
stabilizes the vibrating force acted. The sound absobent 96 reduces the 
impact sound generated when the vibrating force is acted. 
FIG. 1(b) is a perspective drawing of a vibration level measuring unit 200 
to measure each vibration level at each distance from the position where 
the heavy weight of the vibration generating unit drops. 
The vibration level measuring unit 200 comprises a vibration sensor 110 
placed at a separate distance from the position where the heavy weight 
drops, a vibration level meter 120 connected with the vibration sensor 110 
and to measure a low frequency vibration level and a vibration level 
recorder 130 to record the vibration level measured. 
The vibration level meter is to have the performance equal to or more than 
that specified in Japanese Industrial Standard C 1510 and the (JIS) 
vibration level recorder is also equal to or more than that specified in 
JIS C 1512. 
The measuring method is in accordance with "PAVEMENT TEST HANDBOOK 7-6". 
EXAMPLE 
The examples of a vibration generating unit and a vibration level measuring 
unit are described hereunder. 
In the case that the ground is of a paved road construction, a load given 
to the ground can be shown in terms of a wheel load. While vehicles are 
traveling on a road, a dynamic total load, which is the wheel load plus a 
dynamic added load generated depending on both of the flatness of the road 
surface and the travelling velocity of the vehicles corresponding to the 
wheel load, is actually given to the road surface. Table 2 shows a dynamic 
added load and a dynamic total load corresponding to a designed wheel load 
where vehicles are traveling on a road having a standard flatness at a 
standard velocity (40 km/H). 
TABLE 2 
______________________________________ 
DYNAMIC TOTAL LOAD CORRESPONDING TO 
DESIGNED WHEEL LOAD 
(Standard Flatness: 3.5 mm, Standard Velocity: 40 km/H) 
Designed 
Designed Dynamic Dynamic Dynamic 
Traffic Class 
Wheel Load 
Coefficient 
Added Load 
Total Load 
______________________________________ 
L Traffic 
2 ton 0.42 0.84 ton 
2.84 ton 
A Traffic 
3 ton 0.42 1.26 ton 
4.26 ton 
B Traffic 
5 ton 0.42 2.10 ton 
7.10 ton 
C Traffic 
8 ton 0.42 3.36 ton 
11.36 ton 
D Traffic 
12 ton 0.42 5.04 ton 
17.04 ton 
______________________________________ 
The dynamic coefficient(iFm) = Dynamic Added Load(Fm)/Designed Wheel 
Load(Fs) is variable depending on the road surface flatness and the 
traveling velocity. 
FIG. 10 shows dropping heights of a heavy weight (a column of 30 cm dia. 
and 63 cm high) made of iron (density:7.86 kg/cm.sup.3) weighing 350 kg 
dropped freely and measured the maximum loads generated. A asphalt mixture 
having an average 1.5 cm thickness was laid on an asphalt paved road 
surface to correct the slope and the uneven road surface and a rubber mat 
having a 1.5 cm thickness was further laid thereon as a cushion. Then, the 
load generated was measured by means of a load cell provided on the bottom 
of the heavy weight. 
Therefore, the dropping height of the heavy weight can be obtained from 
formula (1) to generate each dynamic added load corresponding to each 
wheel load in the case that the traveling is made on a road surface having 
a standard flatness (3.5 mm) as shown in Table 2 at a standard velocity on 
a general road as follows: 
EQU y=1.7198.times.-0.111 (1) 
herein, y: dropping height (cm) 
x: maximum generated load (ton) 
According to the formula (1), the dropping height of the heavy weight 
necessary to generate each dynamic added load corresponding to each wheel 
load listed in Table 2 can be obtained as shown in Table 3. 
TABLE 3 
______________________________________ 
Dropping Height of Heavy Weight to Generate Dynamic Added 
Load Corresponding th Designed Wheel Load 
(Asphalt Covering: 1.5 cm, Rubber Mat Thickness: 1.5 cm) 
Designed 
Designed Dynamic Dynamic Heavy Weight 
Traffic Class 
Wheel Load 
Added Load 
Total Load 
Dropping H. 
______________________________________ 
L Traffic 
2 ton 0.84 ton 2.84 ton 
4.90 cm 
A Traffic 
3 ton 1.26 ton 4.26 ton 
7.30 cm 
B Traffic 
5 ton 2.10 ton 7.10 ton 
12.20 cm 
C Traffic 
8 ton 3.36 ton 11.36 ton 
19.50 cm 
D Traffic 
12 ton 5.04 ton 17.04 ton 
29.30 cm 
______________________________________ 
As shown above, any loads required can be set and generated by varying the 
dropping height of the heavy weight or the weight of the heavy weight. The 
dynamic added loads generated corresponding to the designed wheel loads on 
a road surface having a standard flatness are obtained as described above. 
Thus, the induced ground vibration level is measured at the road side by 
giving a specified dynamic added load to the paved road surface. The load 
giving position is generally at the outer wheel traveling portion of the 
outer lane and each measuring position of the vibration level is located 
at 2 m, 5 m, 10 m, 15 m and 20 m from the central point of the load giving 
place (vibration origin) in the direction of a right angle from the 
vibration origin and a curved line connecting each maximum value of the 
vibration level wave at each measuring point. The vibration level at the 
above each distance from the vibration origin is compared with a standard 
value of the vibration level measured separately and the vibration 
properties of paved road construction or the pavement damping function of 
the pavement can be calculated therefrom for evaluation. 
On the other hand, in the case that the ground is a cushion course of 
architectural construction base, the load corresponding to the seismic 
intensity is to be given to the ground and the vibration generated is 
measured as the origin of the vibration in terms of vibration level at 
each distance as described above. The measured vibration level is compared 
with a standard vibration level measured separately and the vibration 
properties of the cushion course of the architectural construction base 
can be calculated therefrom. 
As described above, in the case that the ground is a paved road 
construction, a heavy weight is fallen on the paved road surface from a 
specified height vertically, and any designed wheel loads corresponding to 
the L to D Traffics listed in Table 1 may be acted on by varying the 
falling height and the mass of the heavy weight according to the present 
invention. 
The dynamic added load generated corresponding to the designed wheel load 
while vehicles are traveling on a road surface having the standard 
flatness can be acted on the road surface. In this case, when one vehicle 
is traveling, the heavy weight is acted on only once. When a plurality of 
vehicles are traveling, the heavy weight is acted on once per unit time 
continuously, for instance, once per about a second repeatedly. Then, the 
vibration generated is measured as a vibration level at each distance from 
the vibration origin and the vibration properties of pavement can be 
calculated from the measured values. 
In the case that the ground is a cushion course of architectural 
construction base, the load corresponding to a seismic intensity of 
earthquake can be acted on a ground by dropping a heavy weight vertically 
by means of the vibration generating equipment and by changing the 
dropping height or the mass of the the heavy weight. Then, the vibration 
properties of the ground can be calculated from the measured values 
obtained by measuring the vibration generated as a vibration level at each 
distance from the vibration origin.