JP2007170099A - Method for preventing differential settlement by reducing liquefaction of existing building foundation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing differential settlement by reducing the liquefaction of the foundation ground of an existing building of large plane scale built on the ground with a risk of liquefaction such as the sandy ground. <P>SOLUTION: A soil improving wall of closed shape surrounding the outer periphery of the existing building is constructed in the outer peripheral ground of the existing building. Support members are constructed at the upper end face of the soil improving wall, and dampers are installed on the support members. Buttresses anchored to the outer peripheral part of the existing building are constructed on the dampers, and load of the existing building can be transmitted to the soil improving wall. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for reducing liquefaction of a foundation ground of an existing building having a large planar scale, which is constructed on a ground that may be liquefied, such as sandy ground, and preventing uneven settlement.

Buildings built on ground that has a liquefied layer such as sand ground saturated with groundwater cause a liquefaction phenomenon on the foundation ground when an earthquake occurs, and the volume of the liquefied layer changes, causing the structure to sink or dissipate. It is known to cause great damage such as the inclination and collapse of buildings.
In order to reduce the liquefaction phenomenon as described above and prevent subsidence or uneven subsidence from occurring, a ground improvement wall having a closed shape and a lattice wall inside is constructed in the ground directly below the structure. 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 implemented on the foundation ground located directly under the structure, and is difficult to implement 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 unsettled settlement, there is no description or suggestion about a configuration that reduces a fluctuating load caused by rocking vibration caused by a strong earthquake.

  The technique of Patent Document 2 is also implemented on the foundation ground located directly under the structure and is difficult to implement on an existing building. 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, there is still no suitable method for reducing the liquefaction of the building and sufficiently supporting the building to prevent uneven settlement.

  An object of the present invention is to provide a suitable method for reducing the liquefaction of the foundation ground of an existing building built on the ground where there is a risk of liquefaction and preventing uneven settlement. A construction method that supports structures while reducing rocking vibrations that occur occasionally, can be carried out without being affected by the existence of existing buildings, and prevents liquefaction of existing building foundations that prevent economic settlement and shorten the construction period, thereby preventing uneven settlement. Is to provide.

  It is another object of the present invention to provide a construction method for reducing liquefaction of an existing building foundation and preventing uneven settlement by reducing the influence of uneven settlement by reducing the existing building to an appropriate position when the existing building is inclined. .

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 that reduces liquefaction of the foundation ground of existing buildings and prevents uneven settlement,
In the outer peripheral ground of the existing building, building a closed ground improvement wall surrounding the outer periphery of the existing building;
Building a support member on the upper end surface of the ground improvement wall;
Installing a damper on the support member, constructing a retaining wall fixed on the outer periphery of an existing building on the damper, and allowing the load of the existing building to be transmitted to the ground improvement wall;
It is characterized by comprising.

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,
It is characterized in that a retaining wall is fixed on the outer peripheral column of an existing building.

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

Invention of Claim 4 is the construction method which reduces the liquefaction of the existing building foundation described in any one of Claims 1-3, and prevents the uneven settlement,
The closed-shaped ground improvement wall is characterized in that a portion where the retaining wall is installed is constructed thick or with high strength.

Invention of Claim 5 is the construction method which reduces the liquefaction of the existing building foundation described in any one of Claims 1-4, and prevents an uneven settlement,
The ground improvement wall is characterized in that it is constructed to a depth within an allowable range of settlement within the liquefied layer, or to a depth that penetrates the liquefied layer and reaches the non-liquefied layer.

Invention of Claim 6 is the construction method which reduces the liquefaction of the existing building foundation described in any one of Claims 1-5, and prevents the uneven settlement.
It includes a step of installing a jack between the support member and the retaining wall and operating the jack to correct the uneven settlement of the existing building.

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 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 uneven settlement has the following effects.
(1) In the foundation ground of a large-scale existing building, a closed ground improvement wall that surrounds the outer periphery of the foundation ground is constructed to reduce liquefaction, and a retaining wall fixed on the outer periphery of the existing building is installed on the damper material Because the load is transmitted to the ground improvement wall, even if the building has a large aspect ratio, the damper material absorbs the vibration energy due to rocking vibration during an earthquake, and the ground improvement wall allows vertical displacement for all or part of the fluctuating load. However, it is possible to reliably prevent uneven settlement and maintain the soundness of the structure. The ground improvement wall can be implemented with high reliability as a general-purpose technology and conventional technology without the need for temporary construction, etc. in advance by the deep mixing treatment method that has abundant known construction results, and has no adverse effect on the existence of existing buildings. Therefore, the construction period can be shortened and the cost can be reduced.
(2) Since the retaining wall is fixed to the outer peripheral column of the existing building, the fluctuating load caused by the long-term vertical force or rocking vibration of the existing building can be effectively transmitted to the ground improvement wall and can be firmly fixed.
(3) Since the jack is installed between the support member placed on the upper end surface of the ground improvement wall and the retaining wall, even if the building tilts due to a huge earthquake, the jack is operated to counter the ground improvement wall. By correcting the structure to an appropriate position using force, it is possible to reliably correct the uneven settlement and maintain the soundness of the existing building.
(4) When the present invention is applied to an existing building supported by a plurality of support piles or foundation piles such as friction piles, the ground improvement wall reduces liquefaction during an earthquake and reduces the fluctuation load of the piles on the outer periphery. Because it bears the burden, the seismic performance of the foundation pile can be improved.

The present invention is a method of reducing liquefaction of the foundation ground 2 directly under the existing building 1 and preventing uneven settlement.
A closed ground improvement wall 3 surrounding the outer periphery of the existing building 1 is constructed in the outer peripheral ground (2) of the existing building 1.
A support member 4 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 5 so that a load 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.

  FIG. 1A and FIG. 1B show the outer periphery of the direct ground base 2a of the existing building 1 in the outer peripheral ground (2) of the existing large building 1 constructed in the basic form directly on the ground 2 with the liquefied layer S. The closed ground improvement wall 3 that surrounds is shown in a state where it is constructed to a depth that reaches the non-liquefied layer H.

  The construction of the ground improvement wall 3 is performed by, for example, injecting a stabilizer such as cement milk into the ground, stirring and mixing with the excavated soil and solidifying it to form a wall having a high rigidity and a low permeability. It is constructed by the mixed processing method or the soil cement wall method. According to the deep mixing method, as shown in FIG. 1A and FIG. 1B, the cylindrical ground improvement wall 3 surrounding the outer periphery of the direct foundation board 2a of the existing building 1 can be constructed continuously from the ground surface to a predetermined depth. 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 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.

  Preferably, 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, thereby making the ground improvement wall 3 thin and improving workability. invention).

  Next, the support member 4 is installed on the upper surface of the closed ground improvement wall 3. Specifically, the support member 4 is constructed by placing concrete on the upper surface of the ground improvement wall 3 and then placing concrete. Since the ground improvement wall 3 is constructed of cement milk or the like that does not have a reinforcing bar, if a large load is intensively applied, it will be damaged or cause uneven settlement, and columns are arranged on the outer periphery of the existing building 1 in particular. The load is concentrated on the ground improvement wall 3 immediately below. Therefore, the purpose of constructing the support member 4 is to ensure that the load of the existing building 1 is transmitted to the ground improvement wall 3 reliably and on average, and to secure a height level for installing a damper described later. is there. From the above points, the supporting member 4 needs to be constructed to have a thickness sufficient to withstand the load of the existing building 1.

  Next, the damper 5 is installed at a predetermined location 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 or the like is preferably used. The damper 5 is connected to either 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.

Then, a formwork and bar arrangement are performed on the damper 5 so as to be in contact with the outer peripheral wall of the existing building 1, and concrete is placed to construct the retaining wall 6. The retaining wall 6 is fixed to the existing building 1 by a fastening member 7 such as an anchor previously driven into the outer peripheral wall 1a of the existing building 1 so that the load of the building 1 can be transmitted to the ground improvement wall 3. .
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).

  In addition, when the aspect ratio of the existing building 1 is large, the axial force fluctuation is relatively large. Therefore, as shown in FIGS. 2A and 2B, the ground improvement wall 3 thickens the part where the retaining wall 6 is installed, It is preferable to increase the vertical support force by increasing the strength (the invention according to 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 the liquefied layer S is thick, as shown in FIG. 3, the ground improvement wall 3 does not reach the non-liquefied layer H, and the subsidence due to liquefaction is reduced to a depth within the allowable subsidence amount range. Adjustments can also be made to reduce costs.

  Because of the above configuration, the damper 5 absorbs vibration energy due to rocking vibration during an earthquake, and the ground improvement wall 3 supports all or part of the fluctuating load and supports the soundness of the structure. It can be held.

  Although not shown in the figure, a jack is installed instead of the damper 5 between the support member 4 and the retaining wall 6 arranged on the ground improvement wall. When the existing building 1 is inclined due to uneven settlement or the like, the sound of the existing building 1 can be maintained by operating the jack and correcting the ground improvement wall 3 to an appropriate height position for the reaction force. The jack preferably has a shock absorbing material attached to the upper and lower contact surfaces to reduce a bending moment generated during an earthquake.

  When the ground improvement wall 3 shown in FIG. 3 is not allowed to reach the non-liquefied layer H, the supporting force is restored if the excess pore water pressure in the ground is dissipated after the liquefaction is finished. Even if this occurs, the damper 5 can be removed and a jack similar to that of the second embodiment described above can be installed to correct the settlement of the building using the ground improvement wall 3 as a reaction force.

  Although the case where it implements to the existing building 1 based directly on FIGS. 1-3 was demonstrated, since this invention can be implemented without being influenced by the condition under the foundation of the existing building 1 at all. For example, even in an existing building 1 ′ supported by a pile foundation as a friction pile as shown in FIG. 4A, it can also be implemented in an existing building 1 ″ supported by a pile foundation as a support pile as shown in FIG. 4B. When the foundation of the existing building is a pile foundation structure as described above, the ground improvement wall 3 reduces the liquefaction during the earthquake and partially bears the fluctuating load of the outer peripheral pile (grid line part). The seismic performance can be improved.

  The embodiments have been described with reference to the drawings. However, the present invention is not limited to the illustrated embodiments, and design modifications and application variations that are usually made by those skilled in the art are within the scope of the technical idea of the invention. I will add a note to include the range. For example, the same method can be applied to a new building.

FIG. 3A is an elevational view showing an overall configuration of a construction method for reducing liquefaction of an existing building foundation and preventing uneven settlement according to the present invention. B is a plan view of A. FIG. A is an elevation view showing an example in which the ground improvement wall on which 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 elevation view showing an example implemented in an existing building supported by a foundation pile having the present invention as a friction pile. B is an elevation view showing an example implemented in an existing building supported by a foundation pile having the present invention as a support pile.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Existing building 2 Ground 2a Direct ground base 3 Ground improvement wall 4 Support member 5 Damper (jack)
6 Retaining wall 7 Tightening member

Claims (7)

A method that reduces liquefaction of the foundation ground of existing buildings and prevents uneven settlement,
In the outer peripheral ground of the existing building, building a closed ground improvement wall surrounding the outer periphery of the existing building;
Building a support member on the upper end surface of the ground improvement wall;
Installing a damper on the support member, constructing a retaining wall fixed on the outer periphery of an existing building on the damper, and allowing the load of the existing building to be transmitted to the ground improvement wall;
A construction method that reduces liquefaction of existing building foundations and prevents uneven settlement.   The method for reducing liquefaction of an existing building foundation and preventing uneven settlement according to claim 1, wherein a retaining wall is fixed on an outer peripheral column of the existing building.   The construction method for reducing ground liquefaction and preventing uneven settlement according to claim 1 or 2, characterized in that the ground improvement wall is constructed with high strength with cement mixed with fiber reinforcement.   The closed ground improvement wall reduces the liquefaction of the existing building foundation according to any one of claims 1 to 3, characterized in that the part where the retaining wall is installed is constructed thicker or with higher strength. A method to prevent uneven settlement.   The ground improvement wall is constructed at a depth within the allowable range of settlement in the liquefied layer, or at a depth that penetrates the liquefied layer and reaches the non-liquefied layer. A construction method that reduces liquefaction of existing building foundations and prevents uneven settlement.   The existing installation according to any one of claims 1 to 5, further comprising a step of installing a jack between the support member and the retaining wall and operating the jack to correct the uneven settlement of the existing building. A construction method that reduces liquefaction of building foundations and prevents 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 structure or a pile foundation structure.

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