JPH11315544A - Vibration isolation method for structure and construction of vibration isolation of structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damage by a ground liquefaction at the time of an earthquake, to attain base isolation by effectively utilizing the liquefaction and to omit soil improvement after the completion of the earthquake. SOLUTION: An enclosing wall 9 enclosing the outside of the foundation structural section 4 of the structure 1 while boring a liquefaction induction opening 8 is installed, liquefaction accelerating soil 10 is buried into the liquefaction induction opening 8, and the structure 1 is borne to grounds 11, 11a by a plurality of hollow piles 7. Excessively pressed water in the ground 11 causing liquefaction at the time of the generation of an earthquake is introduced into the enclosing wall 9 through the water introducing holes 13 of the piles 7, an internal passage and a communication passage, the liquefaction accelerating soil 10 is liquefied, and the structure 1 is vibration-isolated by the liquefaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic isolation method for a structure and a seismic isolation structure for a structure, and more particularly, to excessively pressurized water generated in the ground at the time of an earthquake by utilizing excess pore water pressure. The present invention relates to a technology for seismically isolating a structure by liquefying soil at least around a basic structure of the structure by guiding the soil upward through a hollow pile.

[0002]

2. Description of the Related Art In the case of soil that supports various structures (various structures such as buildings, piers, abutments, tanks, etc.), if the soil is easily liquefied, the soft ground liquefies when an earthquake occurs. It is known that structures tilt and fall over. The soil that composes the ground contains water and air.Soils with fine particles, soils with high moisture or air content, or soils that are not tight can be affected by repeated vibrations on the ground during an earthquake. Easily liquefies.

[0003] By the way, it is a fact that was observed during the Hyogoken-Nanbu Earthquake. The ground liquefaction was caused by a plurality of seismic waves of about 200 to 300 gal at the beginning of the earthquake, and once the liquefaction occurred, Seismic vibrations are less likely to be transmitted to the foundation structure of the structure, and subsequent vibrations of the structure are reduced.
In other words, liquefaction of the ground has the effect of isolating the structure. Conventionally, sand piles for blowing water from the ground to the ground surface in landfills have been widely put into practical use.However, since the passage resistance in the sand piles is extremely large, the sand piles are used to minimize the water in the ground. It is possible to drain at very low speed. However, it is almost impossible to rapidly drain pressurized water in the ground through a sandpile when an earthquake occurs.

[0004]

[Problems to be Solved by the Invention] In the case of a structure constructed on soft ground such as a landfill, the structure is greatly inclined or the structure falls due to liquefaction of the ground when an earthquake occurs. Cause great damage. Moreover, after the earthquake, it takes a lot of money to repair the ground or make major changes to the foundation of the structure. An object of the present invention is to provide a technology for seismically isolating a structure by effectively utilizing ground liquefaction, to reduce damage due to ground liquefaction, to prevent ground liquefaction during an earthquake, And so on.

[0005]

According to a first aspect of the present invention, there is provided a seismic isolation method for seismic isolation of a structure, wherein an internal passage for guiding water in the ground upward to a pile supporting the structure. It is formed in advance, and pressurized water in the ground is guided upward through the pile and its internal passage using the excess pore water pressure in the ground when an earthquake occurs, and at least the soil at the peripheral portion of the foundation structure portion of the structure. Is liquefied, and the structure is seismically isolated.

The above-mentioned structure means various structures such as buildings, piers, abutments, various tanks, etc., and the water in the ground is moved upward by piles supporting the basic structure of the structure. Since the internal passage for guiding is formed in advance, water pressurized by seismic vibration in the ground can be guided upward through the pile and the internal passage when an earthquake occurs. Then, at least the soil at the peripheral portion of the foundation structure portion of the structure is liquefied by the water guided upward from the ground, and the structure can be isolated. However, in order to promote liquefaction of the soil at least in the peripheral portion of the basic structure of the structure, it is desirable to provide a box-shaped surrounding wall surrounding the soil in the peripheral portion in advance.

According to a second aspect of the present invention, there is provided a seismic isolation structure for seismically isolating a structure, comprising a plurality of hollow piles for supporting a foundation structure of the structure and supporting the structure on the ground. A surrounding wall surrounding the outside of the basic structure of the structure with a liquefaction-inducing gap, a liquefaction-promoting soil embedded in the liquefaction-inducing gap inside the surrounding wall, and an outer wall of the surrounding wall. The pile includes a plurality of water introduction holes formed in communication with the internal passage of the pile, and a communication passage that communicates the internal passage of each hollow pile with the liquefaction-inducing gap, and reduces excess pore water pressure in the ground during an earthquake. Utilized water in the ground is introduced into the liquefaction-inducing gap via multiple piles, and the liquefaction-promoting soil in the liquefaction-inducing gap is liquefied to isolate the structure. .

[0008] The structure is the same as in the first aspect. A plurality of hollow piles support the structure by supporting the foundation of the structure. A surrounding wall surrounds the outside of the basic structure of the structure with a liquefaction-inducing gap, and liquefaction-promoting soil is embedded in the liquefaction-inducing gap inside the surrounding wall. Outside the surrounding wall, each pile is formed with a plurality of water introduction holes formed in communication with the internal passage of the pile, and a communication path is formed to communicate the internal passage of each hollow pile with the liquefaction-inducing gap. .

The surrounding wall is a box-shaped wall made of, for example, reinforced concrete, and has a structure capable of withstanding earth pressure due to liquefaction inside the surrounding wall and earth pressure from the outside of the surrounding wall during an earthquake. Therefore, if the pore water pressure in the ground increases during an earthquake,
The water flows into the internal passage from the plurality of water introduction holes of each pile, rises through the internal passage, flows from the communication passage into the liquefaction-inducing gap inside the surrounding wall, and is filled in the liquefaction-inducing gap. Liquefies the liquefaction-promoting soil, which is seismically isolated.

[0010] Generally, a plurality of 200 to 300
In many cases, a seismic wave of the order of galle propagates and then a larger seismic wave propagates.However, from the observation results of the Hyogoken Nanbu Earthquake, the seismic wave immediately after the occurrence of the liquefaction filled the liquefaction-induced gap. If the accelerating soil can be liquefied, the structure can be isolated from the subsequent larger seismic waves. Since the structure is supported by multiple piles by supporting the foundation structure of the structure with multiple piles, even if the liquefaction promoting soil buried in the liquefaction-induced gap inside the surrounding wall liquefies, The structure does not tilt or fall. In addition, since water having excessive pressure that causes liquefaction in the ground around the pile outside the surrounding wall is discharged to the inside of the surrounding wall, liquefaction of the ground can be reliably prevented. .

The seismic isolation structure of the structure according to claim 3 is provided in claim 2.
In the invention of the above, a metal sliding plate is provided at a position near the top of the pile on the lower surface of the basic structure of the structure, and the sliding plate is supported by the pile via a low friction member. It is characterized by having done. That is, when the liquefaction-promoting soil inside the surrounding wall is liquefied at the time of the earthquake, the plurality of piles and the ground side are displaced relative to the structure, so that the basic structure of the structure is A metal slide plate is provided on the lower surface of the part near the top of the pile, and the slide plate is supported by the pile via a low friction member, so that the relative displacement between the plurality of piles and the structure is reduced. The behavior when performing is smooth, and the seismic isolation performance is enhanced.

A seismic isolation structure for a structure according to claim 4 is provided in claim 2.
In the invention, the laminated rubber seismic isolation bearing is provided between the lower surface of the foundation structure of the structure and the top of each pile, and is connected to the structure and the pile. At the time of the earthquake, if the liquefaction-promoting soil inside the surrounding wall is liquefied, multiple piles and the ground side will be displaced relative to the structure, but when the relative displacement occurs At the end of the earthquake, a plurality of laminated rubber seismic isolation bearings were provided between the lower surface of the foundation of the structure and the top of each pile. Since the structure returns to almost the original position by the elastic restoring force of the device, the relative positions of the structure and the plurality of piles become almost the same as before the earthquake.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings. This embodiment is an example in which the present invention is applied to a seismic isolation structure and a seismic isolation method for a structure that is a middle-rise building of about five floors. As shown in FIGS. 1 and 2, the structure 1 has a high rigid bottom plate 2 at the lower end.
And a ground structure section 5 including a basement section to a fifth floor section. Bottom part 2
Is formed in the form of a high rigid slab made of reinforced concrete,
The outer wall of the first basement 3 is also made of reinforced concrete with high rigidity. The seismic isolation device 6 of the structure 1 includes nine hollow piles 7 that support the foundation 1 by supporting the foundation 4 of the structure 1, and that the outside of the foundation 4 of the structure 1 is liquid. It comprises a box-shaped surrounding wall 9 surrounding the liquefaction-inducing gap 8 and a liquefaction-promoting soil 10 embedded in the liquefaction-inducing gap 8 inside the surrounding wall 9.

As shown in FIGS. 1 and 2, the nine vertical piles 7 are arranged in a matrix of three rows and three columns so that the bottom part 2 of the structure 1 can be uniformly supported. 7 penetrates deeply into the ground 11, and the lower end of the pile 7 reaches a hard ground 11a such as a bedrock. As shown in FIG.
Is a hollow stake made of, for example, reinforced concrete. An inner passage 12 for flowing water is formed in the center of the stake, and an inner passage 1 is formed in the stake 7 outside the surrounding wall 9.
A large number of water introduction holes 13 communicating with the surrounding wall 9 are formed.
Inside the stake 7, a plurality of communication passages 14 are formed in the stake 7 to communicate the internal passage 12 with the liquefaction-inducing gap 8.

The surrounding wall 9 is a rectangular box made of a reinforced concrete wall having a predetermined thickness and resistant to earth pressure due to liquefaction inside the surrounding wall when an earthquake occurs and earth pressure from the outside of the surrounding wall during an earthquake. In the liquefaction-inducing gap 8 inside the surrounding wall 9, a liquefaction-promoting soil 10 mainly containing silt, sand, or a mixture thereof is buried. A sliding plate 15 made of, for example, stainless steel is provided on a portion of the lower surface of the bottom portion 2 of the structure 1 near the top of each pile 7.
A low-friction member 16 made of a solid lubricant such as molybdenum disulfide is fixed to the upper end of each pile 7, and this low-friction member 16 is brought into surface contact with the lower surface of the sliding plate 15, and the structure 1 Are supported by nine piles 7 with low friction.

As shown in FIGS. 1 to 4, during the earthquake, the ground 11 and the surrounding wall 9 are allowed to move horizontally relative to the structure 1 and the pile 7 due to the vibration of the ground 11, 11a. Thus, the pile insertion hole 1 through which the respective piles 7 of the surrounding wall 9 are inserted
7 is predetermined (for example, about 300 mm) between the periphery of the pile 7
Is formed in such a size that a gap 18 is left. As shown in FIG. 3, in order to prevent the water flowing into the surrounding wall 9 from escaping from the pile insertion hole 17 to the outside, the pile insertion hole 1 is used.
Reference numeral 7 denotes a stainless steel cover plate 19 which is fitted over the pile 7 and is closed from above. The cover plate 19 has a larger diameter than the pile insertion hole 17 and is provided so as to be relatively movable with respect to the surrounding wall 9.

The operation of the seismic isolation structure of the structure 1 described above will be described. However, the description of the operation includes the description of the seismic isolation method. Under normal conditions, structures 1 and 9
The piles 7 and the surrounding wall 9 are as shown in FIG. 1, and the structure 1 is supported on the ground 11, 11 a by the nine piles 7. When the pore water pressure in the ground 11 becomes large due to the initial vibration of the plurality of waves of about 200 to 300 gal when the earthquake occurs, as shown in FIG.
The water in the inside is introduced into the internal passages 12 of each pile 7 from a number of water introduction holes 13 formed in the nine piles 7, flows upward through the internal passages 12, and flows from the plurality of communication passages 14 of each pile 7. It flows into the liquefaction-inducing gap 8 inside the surrounding wall 9 and liquefies the liquefaction-promoting soil 10 in the liquefaction-inducing gap 8.

Thereafter, with the liquefaction proceeding,
For example, even if a strong seismic vibration of 600 gal or more propagates, the liquefaction-promoting soil 10 around the basic structure 4 of the structure 1
Is already liquefied, and the liquefied liquefaction-promoting soil 1
Since the seismic vibration hardly propagates through the zero, the structure 1 is effectively isolated. With this seismic isolation,
Damage to the structure 1 itself and damage to equipment and personnel inside the structure 1 are extremely reduced. Moreover, in the event of an earthquake, most of the excessively pressurized water in the ground 11 that causes liquefaction is discharged into the surrounding wall 9 through the nine piles 7. Therefore, the liquefaction of the ground 11 can be reliably prevented. Therefore, there is no need to repair the ground 11 after the end of the earthquake, and civil engineering costs after the earthquake can be reduced.

However, there is a possibility that the surrounding wall 9 and the liquefaction-promoting soil 10 move relatively to the structure 1 due to the earthquake vibration, and the nine piles 7 move relatively to the structure 1. However, since the low friction member 16 at the upper end of each pile 7 and the sliding plate 15 are easily slipped, large horizontal seismic force does not propagate to the structure 1 from the nine piles 7. In FIG. 4, the solid-line structure 1 shows an example before the earthquake, and the chain-line structure 1 shows an example after the earthquake. At the end of the earthquake, the structure 1 has a surrounding wall 9 and nine
May be relatively deviated from

As a countermeasure in such a case, a jack system for moving the structure 1 shown in the dashed line to the position shown in the solid line is provided in advance in the inside of the bottom part 2 or the first basement floor 3, and the jack system is provided. A liquefaction-inducing gap 8 is used to apply a force transmitting member suitable for applying a force to the surrounding wall 9 from the hydraulic jack.
It is desirable to equip it inside. Here, 9 piles 7
Can be reused as long as the internal passage 12 is not clogged with sand or soil. Therefore, in order to suppress the inflow of earth and sand into the internal passage 12, it is desirable to attach a durable wire mesh filter member to all the water introduction holes 13.

A description will be given of a modified example in which the above-described embodiment is partially modified. 1] As shown in FIG. 5, a laminated rubber seismic isolation bearing device 20 is provided between the lower surface of the foundation structure 4 of the structure 1 and the top of each pile 7.
May be connected to the structure 1 and the pile 7. The laminated rubber type seismic isolation bearing device 20 is substantially the same as an existing well-known one, and has a laminated rubber main body 21, a lower connecting portion 24, and an upper connecting portion 26. The laminated rubber main body 21 is formed by alternately laminating a plurality of metal plates and high-damping rubber plates. The lower connecting portion 24 is formed in a cap shape by the cylindrical portion 22 and the lower base 23 and is fixed to the top of the pile 7. The upper connecting part 26 is configured by an upper base fixed to the lower surface of the bottom part 2 by a plurality of bolts 25.

The laminated rubber type seismic isolation bearing device 20 is excellent in vertical load supporting performance, and exhibits a horizontal elastic restoring force while allowing a large relative horizontal displacement between the structure 1 and the pile 7 in the event of an earthquake. Things. Therefore, when the nine sets of laminated rubber seismic isolation bearing devices 20 are applied as described above, the structure 1 does not stop at the position displaced with respect to the pile 7 at the end of the earthquake. Like the solid structure 1, the structure 1 will surely return to the initial position.

2) In the above-described embodiment, the nine stakes 7 are effectively used to form the internal passage therein, but the water in the ground is guided to the liquefaction-inducing gap 8 in the surrounding wall 9. It is also possible to apply a tubular member other than the pile together with the plurality of piles 7. 3) In the above embodiment, nine piles 7 are applied.
Is appropriately set in relation to the size and weight of the structure 1.

4) The pile 7 of the embodiment is provided so as to reach the hard ground 11a such as a bedrock. However, the plurality of piles 7 do not necessarily have to reach the hard ground 11a such as a bedrock. It may be located in the middle of the ground. 5) The seismic isolation device and the seismic isolation method of the present invention can be applied to various structures (piers, abutments, various tanks, towers) other than buildings, and various modifications to the above embodiment can be made. Of course, it can be implemented in a loaded mode.

[0025]

According to the seismic isolation method for a structure according to the first aspect, an internal passage for guiding water in the ground upward is formed in a pile supporting the structure in advance, and an excess passage in the ground when an earthquake occurs. Utilizing pore water pressure to guide the pressurized water in the ground upward through the pile and its internal passage, to liquefy the soil at least in the periphery of the foundation structure of the structure, and to isolate the structure,
Through the simple preparation of forming the internal passage in the pile in advance, it is possible to liquefy the soil at least in the peripheral part of the foundation structure portion of the structure and to surely isolate the structure. When an earthquake occurs, excessively pressurized water in the ground below the structure that causes liquefaction is guided upward through the pile and its water passage, and the pore water pressure in the ground below the structure Because the soil is properly maintained, the ground does not liquefy, there is no need to take measures such as repairing the ground after the earthquake, and equipment is used to effectively use the pile as an internal passage forming member It is cost effective.

According to the seismic isolation structure of the structure of the present invention, hollow piles each having an internal passage are applied as a plurality of piles,
A surrounding wall is provided to surround the outside of the basic structure of the structure with a liquefaction-inducing gap, and liquefaction-promoting soil is buried in the liquefaction-inducing gap inside. With a simple configuration that forms an introduction hole and provides a communication path that connects the internal passage of each pile to the liquefaction-inducing gap, multiple piles and their internal passages are utilized by using excess pore water pressure in the ground during an earthquake. The pressurized water in the ground is introduced into the liquefaction-inducing gap through the liquefaction-inducing gap, and the liquefaction-promoting soil in the liquefaction-inducing gap is liquefied, so that the structure can be substantially isolated.

Since the structure is supported by a plurality of piles by supporting the foundation structure portion of the structure with the plurality of piles, the liquefaction-promoting soil buried in the liquefaction-induced gap inside the surrounding wall is liquefied. However, the structure does not tilt or fall. In addition, excessively pressurized water in the ground outside the surrounding wall that causes liquefaction is extracted to the inside of the surrounding wall and the pore water pressure in the ground can be appropriately maintained, so that the outside of the surrounding wall can be maintained. Liquefaction of the ground can be reliably prevented, and there is no need to repair the ground after the end of the earthquake.

According to the seismic isolation structure for a structure of the present invention, a metal sliding plate is provided at a position near the top of the pile on the lower surface of the basic structure of the structure, and the sliding plate is lowered. Since it is configured to be supported by the pile via the friction member, the behavior of the relative displacement between the plurality of piles and the structure during the occurrence of the earthquake becomes smooth, and the seismic isolation performance is enhanced. The other effects are the same as those of the second aspect.

According to the seismic isolation structure of a structure of the present invention, a laminated rubber type seismic isolation bearing is provided between the lower surface of the foundation structure of the structure and the top of each pile, and the structure, the pile and In the event of an earthquake, even if multiple piles and the ground side are displaced relative to the structure with the liquefaction-promoting soil inside the surrounding wall liquefied during an earthquake, Since the structure returns to almost its original position by the elastic restoring force of a plurality of laminated rubber seismic isolation bearings, the relative positions of the structure and the plurality of piles are almost the same as before the earthquake. Other effects are the same as those of the second aspect.

[Brief description of the drawings]

FIG. 1 is a sectional view of a structure according to an embodiment of the present invention and its seismic isolation device.

FIG. 2 is a plan view of a structure and a seismic isolation device.

FIG. 3 is an enlarged sectional view of a main part of the seismic isolation device.

FIG. 4 is a diagram corresponding to FIG. 1 showing a structure before the start of an earthquake and a structure at the end of the earthquake.

FIG. 5 is a main part side view of a seismic isolation device provided with a laminated rubber type seismic isolation bearing device according to a modification.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Structure 2 Bottom part 3 Basement 1st floor part 4 Foundation structure part 6 Seismic isolation device 7 Pile 8 Liquefaction induction gap 9 Surrounding wall 10 Liquefaction promoting soil 11 Ground 12 Internal passage 13 Water introduction hole 14 Communication passage 20 Laminated rubber type Seismic isolation bearing device

Claims (4)

[Claims] In a seismic isolation method for seismically isolating a structure, an internal passage for guiding water in the ground upward is formed in advance on a pile supporting the structure, and an excessive pore water pressure in the ground when an earthquake occurs. Utilizing the pile and the pressurized water in the ground upward through the internal passage,
A seismic isolation method for a structure, comprising liquefying at least the soil around the basic structure of the structure to seismically isolate the structure. 2. A seismic isolation structure for seismically isolating a structure, comprising: a plurality of hollow piles for supporting a foundation structure of the structure and supporting the structure on the ground; A surrounding wall surrounding the liquefaction-inducing gap, a liquefaction-promoting soil embedded in the liquefaction-inducing gap inside the surrounding wall, and an outer passage outside the surrounding wall formed in each stake in communication with its internal passage. A plurality of water introduction holes, and a communication passage for communicating the internal passage of each hollow pile with the liquefaction-inducing gap, and utilizing the excess pore water pressure in the ground when an earthquake occurs, a plurality of pressurized water in the ground Introduced into the liquefaction-induced gap via a stake,
A seismic isolation structure for a structure, wherein the structure is configured to liquefy the liquefaction-promoting soil in the liquefaction-inducing gap to isolate the structure. 3. A metal slide plate is provided at a position near the top of a pile on a lower surface portion of a foundation structure portion of the structure, and the slide plate is supported by the pile via a low friction member. The seismic isolation structure of a structure according to claim 2, wherein the structure is configured. 4. A laminated rubber seismic isolation bearing device is provided between a lower surface of a foundation structure of the structure and a top of each pile, and is connected to the structure and the pile. Seismic isolation structure of the structure described in.