JPS63233121A - Underground vibration-proof wall - Google Patents

Abstract

PURPOSE:To obtain an underground vibration-proof wall having excellent durability by a simplifed work i which a wall made of a swelling material, e.g., bentonite or clay is provided between a vibration-proof body and the vibration source. CONSTITUTION:On an adequate position in the direction of the vibration source 11 from a vibration-proof body 12, a vibration-proof wall 2 made of a swelling material such as bentonite or volcanic clay, having a thickness of about 0.8m, is constructed. An upper cover 3 is attached at almost the same level as the ground's surface 1b to the upside of the wall 2. Waves 13 from the source 11 are partly reflected on the wall 2 and partly absorbed by the inside of the wall 2. Only the remaining weal waves 13a reach the vibration-proof body 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to, for example, a pond wall that blocks vibrations propagating through the ground.

[Conventional technology]

Conventional underground walls for ground vibration isolation (hereinafter referred to as vibration isolation walls)
Some of them are as follows.

(1) A trench with a certain depth and width from the ground surface, (2) A wall filled with foam material such as Styrofoam in this trench, (3)
Concrete wall, (4) Steel wall (including steel sheet pile wall), (5
) Composite wall of foam material and concrete, (61tii! Wall with foam vibration isolation material (including rubber, etc.) attached to sheet pile, (7) Wall using dry sand as vibration isolation material, (8) Air bag This is a wall filled in a hollow trench.

The above-mentioned principle of vibration isolation by vibration isolation walls utilizes the property of wave reflection due to the difference in wave impedance ρ■ (ρ is the density of the medium, and ■ is the vibration propagation speed) of adjacent media.

Therefore, it is better to choose a material and wall thickness that has a large proportion of wave reflection, or in other words, a material and wall thickness that has a small amount of wave transmission.

Waves reflected by vibration isolation walls propagate horizontally or vertically to the ground and are dissipated. Since the width of the vibration isolation wall is finite, some of the waves propagated in the vertical direction will be diffracted at the ground below the lower end of the vibration isolation wall and will go around the vibration isolation wall on the opposite side of the vibration source. There is also a wave component that reaches the ground and reaches the ground surface.

In this way, the waves that propagate to the opposite side of the vibration isolation wall from the vibration source are the sum of the waves that pass through the vibration isolation wall and the waves that go around from the lower end of the vibration isolation wall.

Waves diffracted from the lower end of the vibration isolation wall can be reduced by making the vibration isolation wall as deep as necessary. In other words, by deepening the vibration isolation wall, many of the components of the waves that wrap around from the bottom of the vibration isolation wall are dissipated far below the ground.
It is possible to reduce the wave component that propagates from below near the earth's surface.

[The problem that the invention attempts to solve]

The conventional underground vibration isolation walls as described above have the following problems.

Since there is no medium for transmitting waves other than water and air in the air groove, the waves that pass through the vibration isolation wall are so small that they can be ignored.
This is the most effective anti-vibration wall that utilizes wave reflection. However, if you want to obtain a sufficient anti-vibration effect,
The depth of the vibration isolation wall must be approximately equal to the wavelength of the wave to be blocked. The deeper the wall of the trench, the more likely it is to collapse, making it impossible to maintain the trench for a long period of time. Even if an attempt was made to maintain the hollow groove with sheet pile walls, etc., it would be difficult to construct a hollow (ji), as it would be necessary to insert cross beams due to the tonosho.

In vibration isolation walls made of foamed material such as expanded foam, the specific gravity of the vibration isolation material is much lower than 1, so if there is groundwater, the vibration isolation material will float to the surface due to buoyancy. Even if an anchor is placed in the ground, it is difficult to loosen it due to the strength of the material. Also, as the wall gets deeper. There are many problems in realizing that it cannot withstand the earth pressure.

Concrete walls do not provide the necessary vibration isolation effect because waves pass through the vibration isolation wall.

This can be obtained from the following equation, which calculates the wave transmissibility (τ - amplitude of transmitted wave/amplitude of incident wave) when there is a vibration isolation wall on infinite ground.

τ= 4α/((1+α)'+(1-α)4-2(1-
α2)2cos4 yr flll/v2) l/2-
(1) Here α-ρ2v2/ρ, V, , H vibration isolation wall thickness, f frequency, pl, ground density, Vl, velocity of wave propagating through the ground 5 p2 density of vibration isolation wall material, V2 ・Vibration isolation It is the speed of waves traveling through the wall material.

For example, in the case of a concrete wall with a width of 50 cm and a frequency of 10 Hz, the value is 092.

Since steel walls allow most of the wave motion to pass through them, sufficient vibration isolation effects cannot be achieved. For example, in the case of steel with a width of 5 cm, the transmissibility at 10 Hz is 0.995 according to equation (1).

The composite wall of foamed material and concrete 1.0 was adopted to serve as a weight for the foamed 44 KEI, which has a specific gravity of less than 1. As mentioned above, the anti-vibration effect of concrete cannot be expected. In order to obtain sufficient vibration damping effect, the Young's modulus of the foam material must be small.
At that time, the foam material has the disadvantage of not being able to withstand earth pressure.

The disadvantages of walls made of steel sheet piles with foam vibration isolators are the same as those of foam and concrete composite walls.

In a vibration isolation wall using dry sand for the vibration isolation material, the Young's modulus and density of the vibration isolation material are similar to those of the ground, so the vibration isolation effect due to wave reflection is negligible. This vibration isolation wall seems to use damping due to the internal friction of dry sand as the principle of vibration isolation.

It is a well-known fact that this internal damping changes depending on the magnitude of dynamic strain in the ground.

Generally, as the strain increases, internal damping increases. The dry sand used here as a vibration isolator can be considered to be the same as the ground. Since the strain in the ground during actual ground vibration is extremely small (approximately 10-6 to io-'), the internal damping is also small, and no effective effect of vibration isolation walls made of dry sand can be expected.

A wall filled with air bags in an empty groove has a low density, so
The air bladder will be very light. The vibration isolation wall needs to have a depth of 10 m or more for vibration frequencies that generally cause problems due to vibration pollution, such as traffic vibration. In that case, groundwater will exist within the vibration isolation wall.

If groundwater is present, the air bladder will float due to buoyancy.

If weight is added to overcome the buoyancy, the anti-vibration effect will be lost. Also, due to deterioration of the bag material, even if a hole the size of a bottle pole is made, the air inside will still escape.
There are also problems with durability, such as the lack of anti-vibration effects.

(Means for Solving the Problems) In the underground vibration isolation wall according to the present invention, a wall surface made of a swellable material such as hentonite is provided between the vibration isolation body and the vibration source.

[Function] In the present invention, waves emitted from a vibration source are not only reflected by the vibration isolation wall, but also absorbed by a swelling material such as bentonite that constitutes the vibration isolation wall.

〔Example〕

FIG. 1 is a sectional view of an underground vibration isolation wall according to an embodiment of the present invention. In the figure, 1 is the ground where the vibration source 11 exists, 1a
is the ground where the vibration isolator 12 exists, 1b is the ground surface, and 2 is the hentonite material or polclay with a thickness of 0.8 m (Vol.
13. An anti-vibration wall made of clay;
13a is an arrow indicating the moving direction of the wave.

Next, this operation will be explained. Now, if the vibration isolation wall 2 is provided between the vibration isolation body 12 and the vibration source 11, the waves emitted from the vibration source 11 will proceed in the direction of arrow ]3 and will be partially reflected by the vibration isolation wall 2, while others will be A part is absorbed inside, and the rest weakens and reaches the vibration isolator 12 from the arrow 13a.

FIGS. 2, 3, 2 and 4 are simulation diagrams showing the effect when Hen I Knight is used as the main material of the vibration isolation wall 2. In the figure, the vertical axis is the vibration transmissibility of the vibration isolation wall (π
), and the horizontal axis indicates the vibration frequency (Hz).

Here, the transmissibility is expressed as π-(vibration amplitude after passing through the vibration isolation wall/amplitude of vibration before entering the vibration isolation wall).

The transmissibility shown in FIGS. 2 to 4 was obtained by solving a -dimensional wave equation. Therefore, the depth of the vibration isolation wall 2 corresponds to an infinite case. Does the actual vibration isolation wall 2 have a finite depth?
The depth should be such that the waves traveling around from the lower end of the vibration isolation wall 2 can be ignored.

The ground constant of this real bfU example is Young's modulus E = 7900t
f/m2. Unit volume weight 1. st7m3. Poisson's ratio = 0.494. Attenuation constant h=0.03. The constant of bentonite used as a vibration isolator is E=lOH/m2 (
Figure 2), 100tf/m2 (Figure 3), 200tf
/m2 (Fig. 4), unit volume weight fi+, 65
t; f 7m3 Poisson's ratio ν=0.48. damping constant h
=0.03.

Traffic vibration cylinders generally have a vibration frequency of 3 that causes problems as vibration pollution.
~301-1z. In addition, a minimum amount of vibration reduction of 2 dB (078 in terms of transmission rate) is required. In order to satisfy these conditions, it is necessary that the vibration damping material has a Young's modulus E of 200 tf/m2 or less.

A reduction N of 2 dB or more is absolutely necessary from the human body's senses.

2, 3, and 4 show interesting effects with changes in the transmissibility (π) or frequency (Hz) of P waves (longitudinal waves) and S waves (transverse waves).

From this fact, it is possible to improve the vibration isolation effect by appropriately selecting the thickness of the underground vibration isolation wall 2.

Furthermore, if a deep groove is excavated when installing the vibration isolation wall 2, the wall surface often collapses and underground water infiltrates.Fortunately, hen]-night not only has a waterproof effect, but also has a swelling pressure γ that prevents this. It is possible to take countermeasures.

〔Effect of the invention〕

As explained above, this invention is an underground vibration isolation wall in which a groove is provided between the vibration isolator and the vibration source, and a hentonite phase or a swellable material (Volclay) is inserted into this groove. It has the effect of suppressing the vibration energy that reaches the vibration isolator by reflecting or absorbing harmful vibrations emitted from the source.

[Brief explanation of drawings]

Figure 1 is a sectional view of an embodiment of the present invention, Figure 2 is a simulation diagram showing the vibration isolation effect when Young's modulus E = +Otf/m2 of the vibration isolation wall of this invention, and Figure 3 is A simulation diagram showing the effect when the Young's modulus of the vibration isolation wall of this invention is set to E-100 tf/m2, and FIG. 4 is a simulation diagram showing the effect when the Young's modulus of the vibration isolation wall of this invention is set to E=200 tf/m FIG. 3 is a simulation diagram shown in FIG. In the figure 1. ] a is the ground, 1b is the ground surface, 2 is the underground vibration isolation wall, 3 is the upper cover, 11 is the vibration source, 12 is the vibration isolator, and 13 is an arrow indicating the direction of wave motion. In each figure, the same reference numerals do not indicate the same or equivalent parts.

Claims (1)

[Claims] An underground vibration isolation wall characterized by providing a wall surface made of a swellable material such as bentonite between a vibration isolation body and a vibration source.