JP4762709B2 - Method to reduce liquefaction of foundation ground of existing buildings and prevent uneven settlement - Google Patents

Description

The present invention reduces the liquefaction of the ground supporting the foundation of an existing building with a large planar scale (hereinafter referred to as a foundation ground) constructed on the ground that may be liquefied, such as sandy ground, and is not subsidized . It relates to a method of preventing

Building built on the ground with a liquid layer of sand soil or the like which is saturated with groundwater, liquefaction occurs foundation ground in the event of an earthquake, the structure is subsidence by the volume change of the liquid layer or differential settlement it has been known to result in a great deal of damage, such as a building of inclination or collapse by.
In order to reduce the liquefaction phenomenon as described above and prevent subsidence and uneven subsidence, a ground improvement wall is built in the foundation ground directly under the structure with a closed shape and a grid wall inside. Thus, it is widely used to prevent liquefaction.

  Patent Document 1 discloses a technique for constructing a ground improvement wall under the foundation of a structure and forming a ground improvement wall on the side where the center of gravity is biased thicker than the other side to reduce settlement or non-uniform settlement. Yes.

Further, in Patent Document 2, a ground improvement wall having a layer thickness such that the amount of settlement of the structure due to liquefaction of the liquefied layer is equal to or less than the allowable amount of settlement is provided as the liquefied layer directly below or below the structure. A technique is disclosed in which the structure is stably supported even when the ground is liquefied by partially forming in a region in which the structure is contained in a plan view.
JP 2003-20659 A JP 2005-83174 A

In the conventional liquefaction prevention method using a closed ground improvement wall, the interval between the lattice walls is determined according to the magnitude of the earthquake and the ground conditions assumed. Therefore, although it can be easily implemented for a new building, in the case of an existing building, it is extremely difficult to implement it directly under the building, which requires a great deal of cost.
Therefore, in reality, a ground improvement wall that only surrounds the outer periphery of the existing building is constructed, and the wall thickness is increased considerably to ensure the rigidity of the ground improvement wall, and its out-of-plane deformation is constrained to liquefy. The phenomenon is prevented. However, enormous costs are required to make the wall thickness considerably large, and when the building plane scale is increased, the range of realistic strength and wall thickness is exceeded.

The technique of Patent Document 1 is also a construction method that is carried out on the foundation ground located directly under the structure, and it is extremely difficult to carry out it on an existing building. In addition, the portion where the center of gravity is biased must be thickened, and the workability is very poor and the cost increases. Moreover, even if it is applied to a new building as well as an existing building to reduce the uneven settlement, there is no description or suggestion about a configuration that reduces the fluctuating load caused by the rocking vibration of the existing building due to a strong earthquake.

The technique of Patent Document 2 is also still a method of implementing the foundation ground located immediately below the structure, but it is difficult to implement in existing buildings. Moreover, although it describes that a liquefaction countermeasure is taken only by the ground improvement wall and the structure is supported stably, it does not consider the point which prevents the uneven settlement or corrects the inclination of the building due to the uneven settlement. However, it cannot be expected to reduce rocking vibration during an earthquake.

In short, to reduce the liquefaction building foundation ground, and preferred method to prevent sufficiently supported to differential settlement of the building is still no.

An object of the present invention, Ru der to provide a suitable method as a means of preventing and reducing the liquefaction foundation ground of existing building from the on ground where there is a risk of liquefaction differential settlement. As far Furthermore, in the method that Ru is supported by the same existing building while reducing the rocking vibration of an existing building that occurs at the time of the earthquake, it can be carried out without being affected by the standing elevation of the existing building, thereby shortening the economical construction period, the existing building It is intended to provide a construction method that prevents liquefaction of the foundation ground and prevents uneven settlement.

The next object of the present invention is a method of reducing the liquefaction of the existing building foundation and preventing the uneven settlement by reducing the influence of the uneven settlement by reducing the influence of the uneven settlement by jacking up when the existing building is inclined. It is to provide.

As a means for solving the above-mentioned problems of the prior art, a method for reducing liquefaction of an existing building foundation and preventing uneven settlement according to the invention described in claim 1 is:
A method for reducing liquefaction of the foundation ground 2a of the existing building 1 or 1 ' and preventing uneven settlement,
Constructing a closed ground improvement wall 3 surrounding the outer periphery of the foundation ground 2a of the existing building 1;
A step of constructing a supporting lifting member 4 of reinforced concrete to the upper end surface of the ground improvement wall 3,
Wherein the damper 5 to allow lifting by rocking the existing building 1 on the supporting member 4 is placed, to build the buttresses 6 fixed to the outer peripheral portion of the existing building 1 on the damper 5, the existing building 1 a load characterized in that it consists of the steps of adapted to be transferred to soil improvement walls 3,.

The invention described in claim 2 is a method for reducing liquefaction of the existing building foundation described in claim 1 and preventing uneven settlement,
The retaining wall 6 is fixed to the outer peripheral pillar 10 constituting the outer peripheral portion of the existing building 1 or 1 ′ , and the retaining wall 6 is constructed on the damper 5 .

The invention described in claim 3 is a method for reducing liquefaction of the existing building foundation described in claim 1 and preventing uneven settlement,
The closed ground improvement wall 3 that surrounds the outer periphery of the foundation ground 2a of the existing building 1 or 1 ′ is characterized by being constructed with high strength with cement mixed with a fiber reinforcement.

Invention of Claim 4 is the construction method which reduces the liquefaction of the existing building foundation as described in any one of Claim 1 or 3, and prevents an uneven settlement,
The closed ground improvement wall that surrounds the outer periphery of the foundation ground 2a of the existing building 1 or 1 ' is characterized in that the wall thickness of the portion where the retaining wall 6 is installed is built thick or with high strength.

The invention according to claim 5 is a construction method for reducing liquefaction of the existing building foundation and preventing uneven settlement, as described in any one of claims 1 or 3-4.
If the liquefied layer of the foundation ground where the existing building 1 or 1 'is built is thick , the ground improvement wall 3 penetrates the liquefied layer S to a depth within the allowable range of settlement in the liquefied layer S or through the liquefied layer S. It is characterized by being constructed to a depth reaching the non-liquefied layer H.

The invention described in claim 6 is a construction method for reducing liquefaction of an existing building foundation and preventing uneven settlement, as described in any one of claims 1 or 3-5.
A step of installing a jack between the support member 4 constructed on the upper end surface of the ground improvement wall 3 and the retaining wall 6 in place of the damper and operating the jack to correct the uneven settlement of the existing building 1 or 1 ′ It is characterized by including.

Invention of Claim 7 is the construction method which reduces the liquefaction of the existing building foundation described in any one of Claims 1-6, and prevents the uneven settlement.
The foundation of the existing building 1 or 1 ' is a direct foundation structure or a pile foundation structure.

The construction method according to the present invention that reduces the liquefaction of the existing building foundation and prevents the unsettled settlement has the effects described below.
(1) dampers to build a ground improvement wall 3 of the closed shape surrounding the outer periphery of the large-scale foundation ground 2a of existing buildings 1 reduces the liquefaction of the foundation ground 2a, was placed on top of the soil improvement wall 3 The building wall 6 is built on the ground improvement wall 3 on the material 5 and fixed on the outer periphery (peripheral column 10) of the existing building 1 to transmit the building load. The damper material 5 absorbs the vibration energy to be vibrated, and the ground improvement wall 3 supports all or part of the fluctuating load while allowing vertical displacement, thereby preventing uneven settlement and ensuring the soundness of the existing building 1. Can hold.
The ground improvement wall 3 can be constructed with high reliability as a general-purpose technique and a conventional technique without the need for temporary construction, etc. in advance by the deep mixing treatment method, etc., which has abundant known construction results. all does not adversely affect the existence, it is possible to realize a reduction of the shortening of the construction time and cost.
(2) When the buttress 6 to be fixed on the outer periphery pillar 10 of an existing building 1, except that the variable load caused by long-term vertical forces and Rocking existing building 1 can be effectively transmitted to ground improvement wall 3, the outer periphery the fixing of the pillar 10 as possible out strong by the anchor 7.
(3) If you install a jack between the wall 6 ahead and the supporting member 4 which is constructed on the upper end surface of the ground improvement wall 3, the operation to soil improvement jack be inclined chance existing building 1 by massive earthquake By taking the wall 3 as a reaction force and correcting the existing building 1 to an appropriate original position, it is possible to reliably correct the uneven settlement and maintain the soundness of the existing building 1.
(4) When implementing the existing building 1 'supported on the foundation pile such as a plurality of supporting piles or friction piles the present invention, while soil improvement wall 3 is reduced liquefaction of foundation ground 2a during an earthquake, the pile Since the variable load is partially borne, the seismic performance of the foundation pile can be improved.

The present invention is a method of preventing reduced differential settlement bracketing liquefying foundation ground 2a in ground improvement wall 3 of the closed shape immediately below the existing building 1.
To build a ground improvement wall 3 of the closed shape surrounding the outer periphery of the existing building 1 of the foundation land board 2a.
A support member 4 made of reinforced concrete is installed on the upper end surface of the ground improvement wall 3.
A damper material 5 is installed on the support member 4 and a retaining wall 6 fixed on the outer periphery of the existing building 1 is constructed on the damper material 5 so that the load of the existing building 1 can be transmitted to the ground improvement wall 3 . .

  Hereinafter, an embodiment of a method for reducing liquefaction of an existing building foundation and preventing uneven settlement according to the present invention will be described with reference to the drawings.

1A and 1B show a closed ground improvement wall 3 that surrounds the outer periphery of a foundation ground 2a directly under a large-scale existing building 1 constructed directly on the ground 2 with a liquefied layer S in a basic form. The state where it was constructed to the depth reaching the liquefied layer H was shown.

Construction of soil improvement wall 3, for example, a stabilizer for cement milk or the like is injected into the ground, solidified by stirring and mixing the excavated soil, rigid form as low permeability of the wall in a large, well-known deep It is constructed by the mixed processing method or the soil cement wall method. According to Deep Mixing Method, Figure 1A, as shown in FIG. 1B, constructs a tubular ground improvement wall 3 surrounding the outer periphery of the foundation ground 2a directly below the existing building 1, the continuous state from the surface to a predetermined depth it can. The wall thickness is determined in consideration of the plane scale of the existing building 1 from about 50 cm to nearly 2 m depending on the selection of the outer diameter size of the excavating stirring blade. Moreover, the ground improvement wall 3 which has a water stop continuously in a longitudinal direction can be constructed | assembled by what is called a moderate lapping process.

  It is preferable that the ground improvement wall 3 is constructed with high strength with cement mixed with a fiber reinforcing material that can be expected to have a high tensile force, and the ground improvement wall 3 is made thin to improve workability. Described invention).

Next, the support member 4 is installed on the upper surface of the ground improvement wall 3 constructed in the closed shape. Specifically, a formwork is installed on the upper surface of the ground improvement wall 3, and after placing the reinforcement , concrete is placed and the reinforced concrete support member 4 is constructed. The soil improvement wall 3 is constructed as a solidification agent the cement milk or the like without being perforated rebar. As thus, a large load causes or differential settlement damaged and according to centralized or local. In particular, when the outer peripheral column 10 is arranged on the outer peripheral portion of the existing building 1 and a later-described retaining wall 6 is constructed on the outer peripheral column 10, the building load is concentrated on the ground improvement wall 3 immediately below the retaining wall. . Therefore, the purpose that is transmitting the load of the existing building 1 transmitted through buttresses 6 to reliably and average wide ground improvement wall 3, and the height for the damper installed to be described later to build the support member 4 there is particular to ensure the level. The support member 4 from the above points Ru built thickness to withstand the load of the existing building 1.

Next, install the damper 5 to a predetermined position on the support member 4. As the damper 5 , for example, a ring-shaped rubber having an expansion / contraction function that allows lifting due to rocking vibration of a building is preferably used. The damper 5 is connected to one or both of the support member 4 and the retaining wall 6 described later by attaching a steel material such as an anchor material to the upper surface and / or the lower surface thereof. The said predetermined location is a location where the retaining wall 6 mentioned later is provided.

On the prior SL damper 5, it established the mold in contact with the outer peripheral wall of the existing building 1 performs reinforcement, buttress 6 of reinforced concrete is constructed by Da設concrete. The retaining wall 6 is fixed to the outer peripheral wall of the existing building 1 by a fastening member 7 such as an anchor previously driven into the outer peripheral wall 1 a of the existing building 1 so that the load of the building 1 can be transmitted to the ground improvement wall 3. It is configured.
As shown in FIG. 1B, when the outer peripheral column 10 is arranged on the outer periphery of the existing building 1, it is preferable to fix the retaining wall 6 to the outer peripheral column 10 (the invention according to claim 2).

Further, when the aspect ratio of the existing building 1 is large, the relative axial force variation is large, FIG. 2A, as shown in FIG. 2B, a portion 3 'soil improvement wall 3 which buttresses 6 is installed the thickness District or, it is preferable to strengthen the vertical supporting force by strengthening (invention described in claim 4). Depending on the thickness of the ground improvement wall 3, the sizes of the support member 4, the damper 5 and the retaining wall 6 are also appropriately designed.

If, when the liquid layer S is thick, as shown in FIG. 3, without reaching the ground improvement wall 3 to the non-liquefaction layer H, the subsidence liquefaction to a depth within the range of the allowable subsidence It is also possible to reduce the construction cost by adjusting the construction .

Since the above-described configuration, while absorbing damper 5 vibration energy due to rocking of the existing building 1 during an earthquake, ground improvement wall 3 is supported while allowing all or part of the variable load, the existing The soundness of the building 1 can be maintained.

Although it is omitted FIG Shimesuru, between the wall 6 ahead and the supporting member 4 disposed on the ground improvement wall 1, when installing a jack in place of the damper 5, the existing building by differential settlement or the like 1 when the inclined can hold the integrity of existing buildings 1 and the correction to return the soil improvement wall 3 by operating the jack to the proper height for the reaction force. The jack, implementation of configurations that the shock absorber attached reduce bending moment occurring during an earthquake to the contact surfaces of the upper and lower are preferred.

As shown in FIG. 3 described above, in the case where the ground improvement wall 3 does not reach the non-liquefied layer H , if the liquefaction is completed and the excess pore water pressure in the ground is dissipated, the bearing capacity is restored. In the unlikely event of uneven subsidence, the damper 5 can be removed and a jack can be installed in the same manner as in Example 2 described above, and the subsidence of the existing building 1 can be corrected to the original state by using the ground improvement wall 3 as a reaction force. .

Until 1 to 3 has been described embodiments relate to an existing building 1 was spread foundation. However, the present invention can be carried out without being affected situations how any right under the existing building 1. For example, even with the existing building 1 'supported on pile foundation by friction pile 11 as shown in FIG. 4A, or also for existing buildings 1 "which is supported by the pile foundation by supporting piles 12, as shown in FIG. 4B It can be carried out.
Then the pile foundation structure foundation of an existing building, as described above, ground improvement wall 3 while reducing the liquefaction just below ground 2a during an earthquake, some fluctuating load of piles 11 and 12 located at the outer peripheral portion toward Since it bears ( work of the grid line part 13 ), the seismic performance of the pile can be improved.

Has been described with reference to the drawings the embodiments of the present invention above, the present invention is not name as far as the embodiments of the illustrated examples. It should be noted that it includes a range of design changes and application variations that are usually made by those skilled in the art without departing from the technical idea thereof. For example, it is possible to implement in a similar manner with the new building.

FIG. 2A is an elevation view showing the overall configuration of a construction method for reducing liquefaction of the foundation ground of an existing building and preventing uneven settlement according to the present invention. B is a plan view of A. FIG. A is an elevational view showing an embodiment in which the ground improvement wall in the portion where the retaining wall is installed is thickened. B is a plan view of A. FIG. It is the elevation which showed the example when a liquefied layer is thick. A is an elevational view showing an example in which the present invention is implemented in an existing building supported by a foundation pile made of friction piles. B is an elevational view showing an example embodying the existing building supported by a foundation pile with the present invention to the support piles.

1, 1 ' existing building 2 ground 2a foundation ground 3 ground improvement wall 4 support member 5 damper ( or jack)
6 Retaining wall 7 Tightening member
10 Peripheral pillar
11 Friction pile
12 Instruction pile
S Liquefaction layer
H Non-liquefied layer

Claims (7)

A method that reduces liquefaction of the foundation ground of existing buildings and prevents uneven settlement,
Constructing a closed ground improvement wall surrounding the outer periphery of the foundation ground of the existing building;
Constructing a reinforced concrete support member on the upper end surface of the ground improvement wall;
Wherein on the support member lifting by rocking the existing building and installing a damper to allow, to build the buttresses have settled to the outer peripheral portion of the existing buildings on the damper, transmit the load of the existing buildings to ground improvement wall A process of making possible,
A construction method that reduces liquefaction of existing building foundations and prevents uneven settlement. The liquefaction of the existing building foundation according to claim 1 is reduced and uneven settlement is established, wherein a retaining wall is fixed to the outer peripheral pillar constituting the outer peripheral portion of the existing building, and the retaining wall is constructed on a damper. Method to prevent. The liquefaction of the existing building foundation according to claim 1, wherein the ground improvement wall having a closed shape surrounding the outer periphery of the foundation ground of the existing building is constructed with high strength with cement mixed with fiber reinforcement. A construction method that prevents uneven settlement. Soil Improvement wall of closed shape surrounding the outer periphery of the foundation ground of existing buildings, characterized by constructing a wall thickness of a portion buttress is placed thick or high strength, existing as set forth in claim 1 or 3 A construction method that reduces liquefaction of building foundations and prevents uneven settlement. If the liquefied layer of the ground where the existing building was built is thick , the ground improvement wall is a depth that reaches the non-liquefiable layer through the liquefied layer to a depth within the allowable range of settlement or through the liquefied layer. The construction method which reduces the liquefaction of the existing building foundation described in any one of claims 1 or 3 and prevents uneven settlement. It includes a step of installing a jack instead of the damper between the support member constructed on the upper end surface of the ground improvement wall and the retaining wall, and operating the jack to correct the uneven settlement of the existing building. The construction method which reduces the liquefaction of the existing building foundation described in any one of Claim 1 or 3-5, and prevents an uneven settlement. The construction method for reducing liquefaction of an existing building foundation and preventing uneven settlement, according to any one of claims 1 to 6, wherein the foundation of the existing building is a direct foundation or a pile foundation structure.

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