JP2010133206A - Structure and construction method for newly-built structure using existing pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To construct a newly-built structure as a spread foundation structure on ground where an existing pile remains. <P>SOLUTION: An existing structure, which is supported by the existing pile 12 buried in the ground G, is removed except for the existing pile 12. The upper end of the existing pile 12 is cut off by performing the pit excavation of the ground G on the periphery of the upper end of the existing pile 12. Subsequently, the newly-built structure 10 is constructed on the composite ground G1 which is formed by making a backfill material 2 arranged in a pit-excavated part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structure and a construction method for a new structure using an existing pile remaining in the ground.

Conventionally, when dismantling an existing structure supported by a pile and constructing a new structure, the existing pile is removed from the existing structure, and the new pile is constructed. The construction method and the method of constructing a new structure with the existing pile remaining in the ground and constructing the new structure using only the new pile as the foundation of the pile are performed.
However, with the method of removing existing piles and constructing new piles, the cost and labor required to remove existing piles are large, especially when existing piles are cast-in-place concrete piles, the removal requires enormous costs and labor. . Also, the ground around the existing piles sometimes loosened after the existing piles were pulled out. In addition, in the method of constructing a new pile with the existing pile remaining in the ground, the installation position of the new pile is restricted, so the construction of the new pile is difficult or the design of the new structure is restricted There was a thing.

Therefore, existing piles are left in the ground, and the existing piles are reused as pile foundations. When the proof strength is insufficient, new piles are also constructed, and new structures supported by these piles are constructed. The way is done.
According to Patent Document 1, an existing structure is removed while leaving an existing pile supporting an existing structure, a mat foundation such as a thick reinforced concrete slab is provided on the existing pile, and a new structure is provided on the mat foundation. A method of construction has been proposed. In the method according to Patent Document 1, the vertical load of the new structure can be sufficiently supported by the existing pile and the mat foundation, and by reusing the existing pile, it becomes unnecessary to remove and backfill the existing pile. Since construction may be performed as necessary, the cost and labor required for constructing a new structure can be reduced.
According to Patent Document 2, a method is proposed in which a new pile is placed avoiding an existing pile, a mat foundation is provided on the existing pile and the new pile, and a new building is constructed on the mat foundation. ing. Existing piles that have reached the supporting ground do not settle with the mat foundation, but mainly bear the vertical force received from the mat foundation, and the new pile is integrated with the mat foundation by rigid joints, and the earthquake horizontal that is received from the mat foundation. Since the force is borne, the new pile need only have a length that can resist horizontal force and does not necessarily have to reach the supporting ground. In the method according to Patent Document 2, since existing piles can be reused and construction of new piles can be reduced, costs and labor required for constructing a new structure can be reduced.
JP 2002-146809 A JP 2003-96794 A

However, the existing piles according to Patent Documents 1 and 2 are reused as pile foundations, and the method for constructing a new structure has the following problems.
In the state where the existing structure exists, it is impossible to confirm whether the actual situation and the installation position of the existing pile coincide with the drawing. After the existing structure is removed, for example, if the existing pile is insufficiently proof as a pile foundation due to deterioration of the existing pile, or the installation position of the existing pile is different from the drawing, the new structure There is a problem that the design of the new structure must be changed, and the design, construction period, and cost of the new structure are changed.

  The present invention has been made in view of the above-mentioned problems, and the newly constructed structure is not a structure that uses an existing pile as a pile foundation, but is constructed directly on the ground where the existing pile remains as a foundation structure. The purpose is to provide a structure and construction method for new structures using existing piles.

In order to achieve the above object, the structure of the new structure using the existing pile according to the present invention is to remove the existing structure, leaving the existing pile supporting the existing structure, on the remaining ground of the existing pile. The structure of a new structure to be constructed, where the ground around the upper end of the existing pile is dug and the upper end of the existing pile is excised, and the new structure is placed above the ground where the backfill material is arranged Is constructed.
Moreover, in the construction method of the new structure using the existing pile according to the present invention, the existing structure is removed while leaving the existing pile supporting the existing structure, and the ground around the upper end of the existing pile is dug. Then, the upper end of the existing pile is cut off, and a new structure is constructed on the ground where the backfill material is arranged.
In the present invention, the new structure is constructed by digging the ground around the upper end of the existing pile, excising the upper end of the existing pile, and constructing the new structure on the ground where the backfill material is disposed. It can be built on the ground where existing piles remain as a direct foundation structure rather than a structure based on existing piles.
Moreover, since the existing pile removes only an upper end part and reuses, the cost and labor concerning removal of an existing pile can be reduced.

Moreover, in the structure of a new structure using the existing pile according to the present invention, it is preferable that the backfill material is a material having lower rigidity than the ground around the ground dug.
In the present invention, the backfill material is made of a material having lower rigidity than the ground around the ground excavated, thereby reducing the concentration of stress acting on the foundation slab of the new structure from the existing pile, and the new structure The amount of sinking of objects can be made uniform.

Moreover, in the structure of the new structure using the existing pile which concerns on this invention, it is good also as a structure by which a new pile or a ground improvement body is arrange | positioned in the ground where the existing pile remains.
In the present invention, by installing a new pile or ground improvement body on the ground where the existing pile remains, the ground can be reinforced even when the ground support is insufficient, and the amount of settlement of the new structure is evenly distributed. Can be made. The new pile or ground improvement body may be placed in the existing area of the existing pile on the ground and mixed with the existing pile, and the existing area of the existing pile on the ground is placed under the new structure. It may be installed, and may be arranged under the existing structure pile of the ground and under the new structure outside the area.

  According to the present invention, since the ground around the upper end of the existing pile is dug and the upper end of the existing pile is excised, and the new structure is built on the ground where the backfill material is arranged, the new structure Does not use the existing pile as a pile foundation, but can construct a new structure directly on the remaining ground of the existing pile as a foundation structure.

Hereinafter, the structure of the new structure using the existing pile according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4.
FIG. 1 is a diagram illustrating an example of an existing structure supported by an existing pile, FIG. 2 is a diagram illustrating excision of the existing pile, FIG. 3 is a diagram illustrating backfilling of the excised portion of the existing pile, and FIG. It is a figure which shows an example of the new structure using the existing pile by 1st embodiment of this invention.

  The structure of the new structure using the existing pile according to the first embodiment is that the existing structure 11 supported by the existing pile 12 embedded in the ground G as shown in FIG. As shown in FIG. 2, the ground G around the upper end 12a of the existing pile 12 is excavated and the upper end 12a of the existing pile 12 is excised as shown in FIG. As shown in FIG. 4, the new structure 10 is constructed on the composite ground G <b> 1 formed by arranging the backfill material 2 on G.

The existing structure 11 is a structure such as reinforced concrete, and is supported by an existing pile 12 such as a columnar ground improvement body or a cast-in-place concrete pile.
The length L of the upper end portion 12 a of the existing pile 12 to be cut is set to a length of about 1 to 3 times the pile diameter D of the existing pile 12.
The backfill material 2 is made of a material having lower rigidity than the ground G around the ground G excavated, and for example, sand, clay, in-situ generated soil, fluidized soil, and the like are adopted.

  The new structure 10 is a structure such as reinforced concrete and is a direct foundation structure that does not use the existing pile 12 as a pile foundation. The new structure 10 and the existing pile 12 are structures in which the backfilling material 2 is disposed between them and is not connected. When the new structure 10 is designed, the bearing capacity and sinking amount of the composite ground G1 on which the new structure 10 is built are calculated, and there is no variation in the bearing capacity deficiency and the sinking amount of the new structure 10. Do a review.

Regarding the predicted calculation of the subsidence amount of the composite ground G1, it can be easily calculated using, for example, the following equivalent stiffness evaluation method.
The composite ground G1 in which the existing piles 12 are arranged is an aggregate of unit periodic structures having a predetermined area made up of the existing piles 12 and the surrounding raw ground. The composite with the pile 12 is regarded as a single homogeneous body having rigidity that can be regarded as equivalent to the rigidity of the entire composite (hereinafter referred to as equivalent rigidity). Moreover, let the ratio of the area of the existing pile 12 with respect to the area of a unit periodic structure be an improvement rate.

  Then, the relationship between the equivalent stiffness and the improvement rate is simplified with the aspect ratio of the unit periodic structure, the stiffness of the existing pile 12 and the stiffness of the original ground as parameters, and based on this, the improvement rate and the equivalent stiffness corresponding thereto And the equivalent rigidity of the composite ground G1 is calculated based on the equivalent rigidity and the external force acting on the entire composite ground G1 in which the existing piles 12 are disposed. The amount of settlement can be calculated by finite element analysis or a beam spring model using the equivalent rigidity.

Next, the construction method of the new structure using the existing pile according to the first embodiment described above will be described with reference to the drawings.
The existing structure 11 shown in FIG. 1 is removed leaving the existing pile 12, and the ground G around the upper end portion 12a of the existing pile 12 is dug as shown in FIG. 2, and the upper end portion 12a is cut off. . And as shown in FIG. 4, the backfill material 2 is arrange | positioned in the ground G excavated, and the composite ground G1 is formed. And the new structure 10 is constructed | assembled on this composite ground G1.

In the construction method of the new structure using the existing pile according to the first embodiment described above, the ground G around the upper end portion 12a of the existing pile 12 is dug and the upper end portion 12a is excised and buried in this portion. Since the new structure 10 is constructed on the composite ground G1 in which the return material 2 is disposed, the new structure 10 is not a structure based on the existing pile 12 but a direct foundation constructed on the composite ground G1. Can be designed as a structure. And the investigation and application regarding the existing pile 12 can be reduced or omitted.
Moreover, since the existing pile 12 cuts only the upper end part 12a and reuses others, the labor and cost concerning removal of the existing pile 12 can be reduced.

Moreover, since the backfilling material 2 is made of a material having lower rigidity than the ground G around the upper end portion 12a of the existing pile 12 that has been cut off, the foundation slab of the new structure 10 from the existing pile 12 via the backfilling material 2 is used. It is possible to alleviate the stress concentration acting on the, and make the amount of settlement of the new structure 10 uniform.
Moreover, since the prediction calculation of the subsidence amount of the composite ground G1 is performed based on the equivalent stiffness evaluation method, the subsidence amount can be easily calculated, and the new structure 10 can be designed by regarding the composite ground G1 as a homogeneous ground. it can.

Next, the second embodiment will be described with reference to the accompanying drawings, but the same or similar members and parts as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted. A configuration different from that of the embodiment will be described.
FIG. 5 is a diagram showing an example of a new structure using an existing pile according to the second embodiment of the present invention.

The structure of the new structure using the existing pile according to the second embodiment is the structure of the new structure using the existing pile according to the first embodiment in which a new pile that reinforces the ground is arranged. is there.
As shown in FIG. 5, the new structure 20 is a structure such as reinforced concrete, for example, and is constructed by grounding the ground G in a wider range than the area where the existing pile 12 remains. Similar to the first embodiment, the supporting force and the amount of settlement of the ground G on which the new structure 20 is constructed are calculated, and the portion where the supporting force of the ground G is insufficient and the amount of settlement are varied. The composite pile G2 is formed by arranging the new pile 3 in the portion.

  The new pile 3 is, for example, an on-site concrete pile or a columnar ground improvement body, and is disposed as a ground reinforcing material. The new pile 3 is not connected to the new structure 20, and the location, shape, and quantity of the new pile 3 are appropriately set according to the strength of the ground G. And in the structure of the new structure using the existing pile by 2nd embodiment, while the new pile 3 is mixed with the existing pile 12 in the area | region where the existing pile 12 of the ground G remains, ground G The existing pile 12 is disposed under the new structure 20 outside the remaining region.

  In the structure of the new structure using the existing pile according to the second embodiment, the new pile 3 is disposed as a reinforcing material in the ground G, so that the supporting force of the ground G is insufficient and the amount of subsidence varies. Since this can prevent the formation of a homogeneous composite ground G2, as in the first embodiment, the new structure 20 is not a structure based on the existing pile 12 but a structure on the composite ground G2. Can be designed as a direct substructure.

Here, the foundation slab of the new structure constructed on the ground where the existing piles remained and the amount of settlement for each floor were measured.
FIG. 6 is a plan view and a cross-sectional view showing the remaining ground of the existing pile and the new structure, and FIG. 7 is a basic slab of the new structure along the AA, BB, and CC survey lines shown in FIG. It is a figure which shows the amount of subsidence for every floor.

As shown in FIG. 6, the new structure 30 is constructed over the composite ground G1 in which the existing pile 12 remains and the original ground G3 in which the existing pile 12 is not embedded, and the first structure of the present invention described above. It is a 5-story direct foundation structure of the structure of a new structure using the existing pile according to the embodiment.
The existing pile 12 is a cast-in-place concrete pile supporting an existing structure (not shown), and the pile diameter D is 1.0 m. The length L of the upper end 12a of the existing pile 12 to be cut is 1.0 m, and the backfilling material 2 is disposed in the portion where the upper end 12a of the existing pile 12 is cut.
In constructing the new structure 30, the amount of subsidence and bearing capacity of the composite ground G1 and the original ground G3 were calculated, and it was determined that it was not necessary to add new piles or ground improvement bodies.

  As shown in FIG. 7, the subsidence amount of the new structure 30 is not significantly different between the composite ground G1 where the existing pile 12 remains and the original ground G3 where the existing pile 12 is not buried, and the subsidence amount over the whole. It can be seen that there is little variation in.

As mentioned above, although the structure of the new structure using the existing pile by this invention and embodiment of the construction method were demonstrated, this invention is not limited to said embodiment, In the range which does not deviate from the meaning It can be changed as appropriate.
Moreover, in said 2nd embodiment, although the new pile 3 is arrange | positioned inside and outside the area | region where the existing pile 12 of the ground G remains, the new structure 20 is constructed | assembled in this ground G, The new pile 3 may be arranged in the region where the existing pile 12 of the G remains, and a new structure may be constructed in this region, or the existing pile of the ground G without the new pile 3 being arranged. A new structure may be constructed over the inside and outside of the region where 12 remains.
In short, it is only necessary to obtain the desired function in the present invention.

It is a figure which shows an example of the existing structure supported by the existing pile. It is a figure which shows excision of the existing pile. It is a figure which shows the backfill of the part which the existing pile was excised. It is a figure which shows an example of the new structure using the existing pile by 1st embodiment of this invention. It is a figure which shows an example of the new structure using the existing pile by 2nd embodiment of this invention. It is the top view and sectional drawing which show the ground with which the existing pile remains, and a new structure. It is a figure which shows the amount of subsidence for every foundation slab and floor of a new structure in the AA, BB, CC line shown in FIG.

Explanation of symbols

2 Backfill 3 New pile 10 New structure 11 Existing structure 12 Existing pile G Ground

Claims (4)

The existing structure is removed by leaving the existing pile supporting the existing structure, and is constructed on the ground where the existing pile remains,
The ground around the upper end of the existing pile is dug up, the upper end of the existing pile is excised, and the new structure is constructed on the upper part of the ground where the backfill material is disposed. Structure of a new structure using existing piles.   The structure of a new structure using an existing pile according to claim 1, wherein the backfill material is a material having lower rigidity than the ground around the ground that has been dug.   The structure of the new structure using the existing pile according to claim 1 or 2, wherein a new pile or a ground improvement body is disposed on the ground where the existing pile remains.   The existing pile is removed leaving the existing pile supporting the existing structure, the ground around the upper end of the existing pile is dug, the upper end of the existing pile is excised, and backfilling material is disposed The construction method of the new structure using the existing pile characterized by constructing the new structure on the ground.

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