JP2850187B2 - Vibration control method using buried flat block - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a base structure provided with a press machine or the like, which suppresses the propagation of vibration to the surrounding ground surface, such as a base structure or a railway structure, and which propagates the vibration. TECHNICAL FIELD The present invention relates to a vibration damping method for suppressing a vibration of a structure such as a building or a ground surface thereof.

[0002]

2. Description of the Related Art In recent years, vibrations around a structure have frequently occurred due to mechanical vibrations and traffic vibrations, and measures to prevent the vibrations have been strongly desired. Particularly in the case of a pile foundation on soft ground, the vibration is propagated into the soft layer and greatly affects the surrounding ground surface, and predominant vibration of the surface ground may be induced.

As one method of preventing such a vibration disturbance, there is a case where a trench is provided around a substructure that generates vibration. However, in this method, since it is actually impossible to hold a complete trench, it is necessary to install a soil retaining member and a support member, and the vibration damping effect is reduced by the soil retaining and the like. In addition, land use in the trench portion becomes impossible.

There is also a method of installing a rigid underground vertical wall around a substructure that generates vibration.

[0005]

The problem to be solved by the present invention is to obtain a higher damping effect than the conventional damping method while effectively utilizing land.

[0006]

The features of the present invention are as follows. That is, a flat plate block having higher rigidity than the surrounding ground is provided in the ground under the substructure that emits or receives the vibration or on the ground around the substructure in the horizontal direction.

[0007] Analysis of a certain layered ground by the finite element method while changing the frequency, depth, width, thickness, and rigidity shows that this flat plate block has a width equal to or greater than the foundation width of the foundation structure. , A thickness of about 1/5 or more of the width of the flat plate block, and a rigidity of 3 to 5 times or more of the surrounding ground at the shear wave velocity, α · Vs / 4f (α = 0.5 to
0.8, Vs is the depth of the shear wave velocity of the ground, f is the frequency). It was found that burying a flat plate block in this way is effective for vibration suppression. This was further confirmed by experiments.

[0008]

In the stratified ground, the dominant periods for the layer thickness H for the propagation of the P wave and the S wave of the body wave are defined as follows. For the propagation of the P wave, Tp = 4H / Vp For the propagation of the S wave, Ts = 4H / Vs, where Tp is the P wave period, Ts is the S wave period, and H is the distance from the ground surface to the rigid base. is there.

Assuming that the representative period of loading of the substructure is To, it is expressed as To = λo / V = 1 / f. If Tp / To and Ts / To are taken as analysis parameters, these parameters are as follows: Tp / To, Ts / To = 4H / λo = 4Hf / V = α. λo is the wavelength of the representative wave, V is the propagation speed of the wave, and f is the frequency of the wave.

By changing Tp / To and Ts / To, the relationship between the ratio of the maximum response value A of the foundation obtained analytically to the maximum response value Ao on the semi-infinite ground, and the relationship between Tp / To and Ts / To is shown. As a result of the investigation, when Tp / To and Ts / To = 1, the resonance of the ground is remarkably observed, and A / Ao becomes a peak. Tp / T
In the case of o, Ts / To> 1, a wave propagation phenomenon from the foundation occurs, and approaches the response state of the semi-infinite ground in the order of rocking, vertical, and horizontal with the layer thickness. Tp / To, Ts / To <
In the case of 1, the response state becomes smaller than the response state of the semi-infinite ground, and the response of the foundation has a damping effect.

That is, Tp / To and Ts / To = α are 1
By designing a highly rigid flat plate as a virtual rigid base plate as follows, it becomes possible to provide a foundation vibration control mechanism. That is, by setting the flat plate at a position where α in H = α · V / 4f is 1 or less, a vibration damping effect can be provided.

FIG. 7 shows the result of the above analysis. In the figure, the vertical axis represents the maximum response value ratio A / Ao, the horizontal axis represents Tp / To,
Ts / To is shown, horizontal vibration is indicated by a solid line, vertical vibration is indicated by a chain line, and rocking is indicated by a one-dot chain line.

Next, experimental results show the vibration damping effect of the buried flat block. The experiment site is located in the lower Asahikawa area of Okayama city,
An alluvium composed of sandy soil and a very soft clay layer is distributed at the top, and a gravel layer with an N value of 50 or more is distributed from around GL-18m. As a result of PS logging, the velocity distribution of Vs was 100 to 340 m / sec, which substantially corresponded to the N value.

As shown in FIG. 8, the foundation structure employed in this experiment was a pile foundation made of H-shaped steel 2 having a gravel layer cast on the diagonal of the footing 1 as a supporting ground. Further, as a vibration damping method, the flat plate block 3 is moved in one direction by GL-1.
It was installed at a position of 9 m by a high-pressure injection stirring method, and a vertical wall 4 by a mechanical stirring method was provided in another direction as a comparison object.

The footing 1 has a planar shape of 3000 m per side.
m square, thickness 500mm, H-shaped steel 2 is 350m long
m, 350 mm in width, 19 mm in thickness on both sides in parallel, 12 mm in thickness on both sides, and 17.5 m in length. And the center interval of the H-section steel 2 is 1600
mm, 100 mm at the tip is embedded in the footing 1

The flat plate block 3 has a bottom surface 1100
It has a substantially trapezoidal shape of 0 mm, an upper side of 9200 mm and a height of 5300 mm, and has a thickness of 1000 mm. The vertical wall 4 had a substantially rectangular shape with a plane shape of 750 mm in length and 6350 mm in width, a thickness of 6000 mm, and was provided at a depth of 760 mm from the ground surface.

In the experiment, a free vibration test was employed, and a vertical drop test on the top surface of the footing 1 and a horizontal impact test on the side surface of the footing 1 were performed. FIG. 9 shows the results of the vertical drop test. In a vertical vibration at a frequency of 10 Hz, the horizontal axis represents the distance from the footing 1 and the vertical axis represents the vertical length of the flat plate block 3 and the vertical wall 4 before construction. The ratio of the vertical response value after construction to the response value, that is, the vertical response value ratio is taken. FIG. 10 shows the results of the horizontal impact test. In the horizontal vibration at a frequency of 9 Hz, the horizontal axis represents the distance from the footing 1 and the vertical axis represents the distance before the flat plate block 3 and the vertical wall 4 were installed. The ratio of the horizontal response value after construction to the horizontal response value, that is, the horizontal response value ratio is taken.

From the results of the vertical drop test and the horizontal impact test, the vertical response value and the horizontal response value at the point directly above the flat plate block 3 and at a point 10 m from the footing 1 of the vertical wall 4 are shown. Comparing the ratios of the maximum values before and after the construction of the flat block 3 and the vertical wall 4, the vertical response value is 0.787 for the flat block, 0.670 for the vertical wall, and horizontal response for the vertical excitation. The values are 0.568 for the flat block and 0.740 for the vertical wall. In the horizontal vibration, the vertical response value is 0.263 for the flat plate block and 0.907 for the vertical wall, and the horizontal response value is 0.324 for the flat plate and 0.808 for the vertical wall.

As a result of the above analysis, the test results have revealed that the flat plate block has a higher damping effect than the vertical wall.

[0020]

1 and 2 show a case in which a structure 11 which generates vibration is supported by a caisson foundation 12a. 1
Reference numeral 3a denotes a flat plate block, which is arranged in a disk shape so that the inner peripheral surface thereof does not contact the casing 12a. K
A pile foundation may be used instead of the son foundation 12a.

FIG. 3 shows an embodiment of an embankment foundation 12b on which a railroad track is mounted, for example, as a substructure that generates vibration. In this case, the flat block 13b is installed in parallel with the embankment foundation 12b. Although not shown, in case of direct foundation,
A flat block is installed directly under the foundation with the same width, or the same width around the underground just below it as in FIGS.

The embodiment shown in FIG. 4 shows a case where a building 14 directly erected on a foundation 12c prevents ground vibration. In this embodiment, the flat plate block 13c is installed directly under the foundation 12c. Although not shown, a flat block may be directly installed around the basement immediately below the foundation 12c.

In the above embodiment, B represents the foundations 12a to 12a.
c, W is the width of the flat plate blocks 13a to 13c, and W ≧
1.00B, t is the thickness of the flat plate blocks 13a to 13c, which is 1/5 or more of W. H is the depth of the flat plate blocks 13a to 13c from the ground surface, and H ≒ α. Vs / 4
-It is f. Where Vs = ground shear rate (m / sec)
c), α = 0.5 to 0.8, f = frequency (Hz). The flat blocks 13a to 13c have a rigidity of 3 to 5 times or more the shear wave velocity Vs of the surrounding ground.
And the amount of cement is adjusted to maintain the rigidity.

The flat plate blocks 13a to 13c, for example, 13
When the work space can be taken, as shown in FIG. 5, after the earth retaining work is carried out with the earth retaining sheet pile 15, as shown in FIG. Then, the earth retaining sheet pile 15 and the shoring 16 are removed and buried.

When the work space cannot be secured, the flat plate blocks 13a to 13c are formed by a high-pressure jet stirring method using a ground improvement machine 17 as shown in FIG. According to this method, the flat plate blocks 13a to 13c are formed such that the peripheral portions of the disks overlap each other.

The planar shape of the flat plate blocks 13a to 13c corresponds to the shape of the foundations 12a to 12c. For example, if the planar shape of the foundation is circular or rectangular, when it is provided immediately below, the shape is circular or rectangular, respectively. When it is provided immediately below, the inner peripheral edge is formed in a circular or rectangular shape, and the outer peripheral edge is formed in a circular or rectangular shape. For a linear structure, for example, a railway structure, it is formed directly under the structure or in the surrounding basement in parallel with the structure.

[0027]

According to the present invention, for many foundation structures such as a caisson foundation, a pile foundation, a direct foundation, and an earth foundation such as embankment, a high damping effect can be obtained both actively and passively without hindering land use. Bring. Therefore, it can be expected to prevent passive vibration of the building provided on the super levee.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an embodiment of a caisson foundation.

FIG. 2 is a schematic plan view of FIG.

FIG. 3 is a schematic longitudinal sectional view showing an embodiment of an embankment foundation.

FIG. 4 is a schematic longitudinal sectional view showing an embodiment of passive vibration damping.

FIG. 5 is a schematic longitudinal sectional view showing installation of a flat plate block by excavation.

FIG. 6 is a schematic longitudinal sectional view showing installation of a flat plate block by a high-pressure jet stirring method.

FIG. 7 is an analysis diagram for explaining the principle of vibration suppression of a flat plate block.

FIG. 8 is a schematic longitudinal sectional view of a facility for experimenting a damping effect of a flat plate block.

FIG. 9 is a comparison diagram between an analysis value and an experimental value of an experiment in which a foundation was vertically excited.

FIG. 10 is a comparison diagram between an analysis value and an experimental value of an experiment in which a foundation was horizontally vibrated.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akihiko Nishimura 2-8-8 Hikaricho, Kokubunji-shi, Tokyo Inside the Railway Technical Research Institute (72) Inventor Ryuichiro Naruse 136-1 Sozume, Okayama-shi, Okayama Pref. 56) References JP-A-56-67024 (JP, A) JP-A-53-142010 (JP, A) JP-A-51-31009 (JP, A) JP-A-55-155829 (JP, A) Hei3-500430 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) E02D 31/08

Claims (1)

(57) [Claims] 1. A vibration damping method in which a flat plate block having higher rigidity than the surrounding ground is provided in the ground below a substructure that emits or receives vibration, or in the ground around the substructure. In addition, the flat block has a width equal to or greater than the foundation width of the foundation structure, a thickness equal to or greater than about 1/5 of the width of the flat block, and a rigidity of 3 to 5 times or more of the surrounding ground at a shear wave velocity. Α · Vs / 4f (where α = 0.5-0.
8. Vs is the shear wave velocity of the ground, and f is the frequency of vibration.