JP4749858B2 - Method for enhancing bearing capacity in extension or reconstruction of superstructures of existing buildings - Google Patents

Description

  The present invention belongs to the technical field of a method for increasing the bearing capacity when an upper structure is extended or reconstructed to an existing building having a pile foundation structure. It is related to the method of building a piled raft foundation with existing foundation slabs and increasing the bearing capacity.

  Conventionally, it is necessary to increase the bearing capacity when extending or remodeling an upper structure in an existing building having a pile foundation structure. In that case, the following methods are generally considered.

As shown in FIG. 2 , a plurality of new piles 43 are placed around an existing pile 41 that supports the existing building 40 and under the existing foundation slab 42, and the new pile 43 and the existing pile 41 are integrated by footing. In the existing building 50 having the existing pile 51 shown in FIG. 3 and the existing pile 51 shown in FIG. 3 , the foundation is excavated to the supporting ground that can support the entire load of the building, and the newly installed foundation slab 52 is directly placed on the bottom As shown in FIG. 4 , when it can be confirmed that the entire load of the existing building 60 supported by the existing pile 61 can be supported by the foundation slab 62, the foundation slab 62 is strengthened and the like. There are piled raft basic types using 62 support resistances, etc.

  By the way, in Patent Document 1, an existing building supported by an existing pile is removed leaving the existing pile, a mat foundation is provided on the upper side of the existing pile, and the mat foundation is used as both the existing pile and the direct foundation. A so-called piled raft-based method of supporting is disclosed.

  Moreover, the method of connecting the some existing piles which support an existing building each by the ground improvement body of predetermined thickness, and ensuring a supporting force is disclosed by patent document 2 or patent document 3, and is well-known. .

JP 2002-146809 A Japanese Patent No. 3213240 Japanese Patent No. 3,385,876

In the method shown in FIG. 2 , in order to perform extension or reconstruction without changing the foundation type, a new pile 43 that reinforces the vertical support force for the extension or reconstruction must be newly placed. However, under the existing foundation slab 42, the construction space is narrow, the machines that can be used are limited, and it is difficult to carry in the machines themselves. In addition, there is a problem that work efficiency and safety are poor because complicated and dangerous work is required. Not only that, construction costs and material costs due to the construction of the new piles 43 increase.

The method of finally changing the pile foundation structure directly to the foundation structure shown in FIG. 3 is not rational because the use of the existing pile 51 is only temporary. Moreover, in order to build the foundation form directly, it is necessary to lower the lower end of the foundation to a stratum that is within the allowable range of reinforcement and subsidence. Therefore, the foundation slab 52 must be constructed to have a thickness sufficient to withstand the load, and the applicable ground is also limited.

The method shown in FIG. 4 is a construction of a piled raft foundation type using the support resistance of the existing foundation slab 62 by reinforcing the existing foundation slab 62, and therefore, the existing foundation slab 62 There is a problem that it cannot be implemented when the ground support is insufficient, such as the ground is soft.

  Since the method described in Patent Document 1 is a method for constructing a mat foundation on the upper side of an existing pile, the mat foundation is arranged between the existing pile and the upper structure. Therefore, as described above, this method cannot be carried out in the case where the ground supporting force cannot be expected, such as the ground of the mat foundation is soft.

  Moreover, the technique described in the said patent document 1 or 2 is not the content which construct | assembles a pile foundation finally to a piled raft foundation, and reinforces a supporting force, or the content which suggests it. Moreover, it is very troublesome to connect adjacent existing piles in the ground by improving the ground, and high technology is required, and the construction is prolonged and the cost is increased.

  The purpose of the present invention is to construct a piled raft foundation that strengthens the bearing capacity by connecting the existing pile and the newly-founded foundation slab when adding or remodeling the superstructure to the existing building supported by the pile. There is no need to construct piles or new pillars, and it is a rational and economical method to increase the bearing capacity in the extension or reconstruction of the superstructure of an existing building.

  The next objective of the present invention is to construct a rational piled raft foundation that enhances the bearing capacity with existing foundation slabs and existing foundation slabs through ground improvement bodies even when the depth to the formation with less subsidence is deep. Thus, it is an object of the present invention to provide a method for enhancing the supporting force in the extension or reconstruction of an upper structure of an existing building that is not affected by the ground.

As a means for solving the above-described problems of the prior art, a method for enhancing the supporting force in the extension or reconstruction of an upper structure of an existing building according to the invention described in claim 1 is:
In the method of increasing the bearing capacity when extending or remodeling an upper structure to an existing building supported by piles,
The ground under the existing foundation slab of the existing buildings, the axial force of existing buildings existing pile while receiving temporary drilling through work holes just below ground provided in the existing foundation slab to less formation and depth of subsidence Process,
Constructing a new foundation slab on the bottom of the excavation and constructing a piled raft foundation by binding the existing pile and the new foundation slab;
It is characterized by comprising.

The method for enhancing the supporting force in the extension or reconstruction of the superstructure of the existing building according to the invention described in claim 1 has the following effects.
(1) After excavating the existing foundation slab of the existing building supported by the piles to the formation or depth with less subsidence, and constructing the new foundation slab, the existing pile and the newly established foundation slab are tightly connected. Since the piled raft foundation is constructed, even if the ground of the existing foundation slab is weak, the vertical axial force of the existing building can be reasonably supported and the extension or reconstruction of the superstructure can be carried out.
(2) Since existing piles are used effectively, dismantling of existing piles, carrying-in work, and installation work of new piles can be dispensed with, improving work efficiency and reducing costs.
(3) Since the existing foundation slab is not excavated and excavated from the ground below it, the existing foundation slab is dismantled and carried out to improve work efficiency, and the foundation slab functions as a beam during excavation. Demonstrate.

The present invention is a method for enhancing a supporting force when an upper structure is extended or remodeled to an existing building 1 supported by an existing pile 4.
First, the existing building 1 Ground B under the existing foundation slab 3, the existing pile 4 axial forces existing pile 1 to a temporary supporting state, the existing foundation slab 3 just below ground to less subsidence strata H Drilling through the work hole provided in
Thereafter, a new foundation slab 5 is constructed on the bottom of the excavation, and an existing pile 4 and the new foundation slab 5 are joined together to construct a piled raft foundation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for enhancing a supporting force in extension or reconstruction of an upper structure of an existing building according to the present invention will be described below based on the drawings.
The existing building 1 which implements this invention is constructed | assembled on the pile foundation structure which consists of the existing pile 4 and the existing foundation slab 3, as shown in FIG. If the foundation ground B is soft and weight is added by extension or reconstruction of the superstructure, the direct foundation structure will not be subsidized and will not be established. To be implemented.

In the method of the present invention, first, the foundation ground B under the existing foundation slab 3 provided as the bottom slab of the existing basement 2 of the existing building 1 is temporarily received by the existing pile 4 with the axial force of the existing pile 1. Then, excavation is performed to the formation H where the subsidence amount is small, and to a depth where the extension or reconstruction can be sufficiently supported in the ground H.

As an excavation method, for example, although illustration is omitted, a work hole is opened in the existing foundation slab 3, an excavator is inserted through the work hole, and the ground under the slab 3 is sequentially excavated. Therefore, since the existing basement 2 and the existing foundation slab 3 are not dismantled, there is no need for extra preparation and work efficiency is high, and the existing basement 2 and the existing foundation slab 3 function as a retaining beam. There is an effect to demonstrate. In addition, there is an effect that the support force of the existing pile 4 can be effectively used during excavation.
Of course, the method is not limited to this method, and a method may be used in which a vertical hole reaching a predetermined depth is provided along the outer wall of the existing building 1 and then excavation is performed from the lateral direction.

  When the excavation of the direct foundation to the formation H with a small amount of subsidence is completed as described above, reinforcement is placed on the bottom of the excavation, and concrete is cast to build a new foundation slab 5. The newly-founded foundation slab 5 is constructed to a thickness sufficient to increase the insufficient supporting force for the extension. In the figure, an example is shown in which the upper and lower plates are implemented as two plates.

  After that, the existing pile 4 and the newly established foundation slab 5 are joined together to construct a piled raft foundation structure. As a binding method, a method of placing an anchor on the existing pile 4 or a method of sticking the main reinforcement of the existing pile 4 to the newly-founded foundation slab 5 is carried out. At this time, the newly established foundation slab 5 and the foundation beam (not shown) are also tightly coupled. In this way, since the supporting force of the existing building 1 is enhanced by both the newly-founded foundation slab 5 and the existing pile 4, it is possible to carry out a reasonable and economical extension or reconstruction of the superstructure.

  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.

It is an elevation view which shows an example of the piled raft foundation which implemented the supporting force reinforcement method in the extension or reconstruction of the superstructure of the existing building which concerns on this invention. It is a reference figure which shows a prior art example. It is a reference figure which shows another prior art example. It is a reference figure which shows another prior art example.

1 Existing building 2 Existing basement 3 Existing foundation slab 4 Existing pile
5 New foundation slab 6 Through hole 7 Ground improvement body

Claims (1)

In the method of increasing the bearing capacity when extending or remodeling an upper structure to an existing building supported by piles,
The ground under the existing foundation slab of the existing buildings, the axial force of existing buildings existing pile while receiving temporary drilling through work holes just below ground provided in the existing foundation slab to less formation and depth of subsidence Process,
Constructing a new foundation slab on the bottom of the excavation and constructing a piled raft foundation by binding the existing pile and the new foundation slab;
A method for enhancing bearing capacity in the extension or renovation of an upper structure of an existing building, characterized by comprising:

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