JPH053489B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an underground vibration isolation wall that blocks vibration pollution, for example. [Prior Art] Conventional ground vibration isolation walls include the following. (1) A structure with air grooves to prevent the propagation of vibrations, (2) A wall surface made of simply parallel foam materials such as Styrofoam to isolate vibrations, and (3) A concrete wall that blocks vibrations. (4) Vibration isolation by steel walls; (5) Vibration isolation by foam and concrete composite walls.
(6) Vibration isolation walls made of dry sand, (7) Vibration isolation walls made of rubber, (8) Vibration isolation materials attached to steel sheet piles, (9) ) The principle of vibration isolation of these vibration isolation walls is based on the property of wave reflection due to the difference in wave impedance ρV (ρ: density of the vibration medium, V: vibration propagation velocity). This is what I did. Therefore, the underground wall should preferably have a greater amount of vibration reflection, such as wave impedance and wall width, than the ground, or in other words, one that has less wave transmission. In addition, vibrations reflected by one underground wall propagate toward the ground on the side of the vibration source or downward underground. Vibrations that propagate downward through the ground are transmitted through the underground walls by diffraction. The vibrations propagate from below the ground to above, reaching the ground surface. Therefore, the vibration propagating to the opposite side of the vibration isolation wall is the sum of the component that passes through the underground wall and the component of the vibration that wraps around from below the vibration isolation wall. In order to suppress the vibration components that circulate from below the vibration isolation wall to an amount that provides a sufficient vibration isolation effect,
1/2λ of the wavelength λ of vibration propagating through the depth of the vibration isolation wall
It may be λ. [Problems to be solved by the invention] In the conventional underground vibration isolation walls as described above, concrete, which is generally used as the vibration isolation wall material,
Materials that are harder than the ground (have a large Young's modulus), such as steel and wood, have a large vibration-transmitting effect and a small reflection effect, so their anti-vibration effect is extremely small. When using a material that is softer than the target ground and has a smaller Young's modulus, such as expanded polystyrene, the softer the material, the greater the vibration damping effect. However, in order to obtain sufficient vibration-proofing effects, the underground walls must be made deeper. Styrofoam etc. have a specific gravity much smaller than 1.
Since it is 0.02 to 0.1, it tends to float due to the buoyancy of groundwater. Also, because it is light and has a small Young's modulus, its underground walls cannot withstand earth pressure and are crushed. There was a problem that if the Young's modulus was increased to withstand earth pressure, the vibration damping effect would be lost. In addition, because conventional vibration isolation walls use materials that are uniform in the depth direction of the ground, there is the problem that if a hard material that can withstand the earth pressure at the deepest part is used as a wall material, the vibration isolation effect will be lost. It was hot. The purpose of this invention is to develop an underground vibration isolation wall that can withstand earth pressure deep underground and reflect elastic waves. [Means for Solving the Problems] In the underground vibration isolation wall according to the present invention, opposing walls are provided between the vibration source and the vibration isolation body, and there is a structure between the walls that can withstand earth pressure and The members having the smallest possible Young's modulus are arranged so that the Young's modulus of the member gradually increases from the top to the bottom. [Operation] In this invention, elastic waves emitted from a vibration source are reflected by the underground vibration isolation wall. The material with a relatively high Young's modulus provided at the bottom of this underground vibration isolation wall can withstand earth pressure. [Embodiment] FIG. 1 is a sectional view of an embodiment of the present invention.
In the figure, 1 is the ground where the 3Hz vibration source 11 exists, 1a is the ground where the vibration isolator 12 is, 1b is the ground surface, and 2 and 2a are opposing walls made of steel plates, steel sheet piles, reinforced concrete, plywood, etc. , 3 is an upper cover provided astride the walls 2, 2a, 4 to 4h are laminated so that the Young's coefficient E gradually increases as the depth increases, and walls 2, 2a are provided to prevent floating.
10 is an underground vibration isolation wall that can reduce input vibration by 3 to 5 dB, 13, 13
a is an arrow indicating the direction of vibration propagation. Next, this operation will be explained. The vibrations emitted from the vibrating body 11 are mainly P waves (longitudinal waves), S waves (transverse waves),
It contains Rayleigh waves and propagates in the direction of arrow 13, but part of it is reflected by the underground vibration isolation wall 10 (0.5 m wide, 50 m deep, made of polystyrene foam), and the other part propagates in the direction of arrow 13a. The vibration isolator 12 is reached. The reason why the waves are reflected by the underground vibration isolation wall 10 is due to the difference in wave impedance ρV, as described in the description of the prior art. Just to be sure, the physical specifications of the ground 1, 1a, the uppermost Styrofoam 4, and the lowermost Styrofoam 4h are shown in the table below.

〔Effect of the invention〕

As explained above, this invention provides an underground vibration isolation wall with opposing walls between the vibration isolation body and the vibration source, and a member with a small Young's modulus is placed in the upper part between the walls within a range that can withstand earth pressure. In addition to protecting the vibration isolator by reflecting harmful vibrations despite its simple structure,
It has the effect of withstanding earth pressure.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is a simulation diagram for comparing the effects of the present invention. In the figure, 1 and 1a are the ground,
2, 2a are walls, 3 is a top cover, 4 to 4h are polystyrene foam, 10 is an underground vibration isolation wall, 11 is a vibration source, 12
is a vibration isolator, and 13 and 13a are arrows. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Provide an opposing wall between the vibration source and the vibration isolator,
An underground vibration isolation system characterized in that members that can withstand earth pressure and have as small a Young's modulus as possible are arranged between the walls so that the Young's modulus of the members gradually increases from the top to the bottom. wall.