JP4365238B2 - Foundation reinforcement method for structures - Google Patents

Description

  The present invention relates to a structure foundation reinforcing method capable of reliably transmitting a vertical load to an additional pile when the foundation structure of the structure is increased and reinforced by a pile.

For example, when renovating a large structure such as a blast furnace, if the weight of the structure increases and the vertical supporting force of the existing foundation is insufficient, the foundation structure needs to be reinforced.
In other words, when there is no margin in the support capacity of the existing foundation and the occurrence of subsidence is unacceptable, it is necessary to reinforce the foundation structure so that the increase in the upper vertical load can be supported accurately.
For this reason, various measures have been taken for reinforcement of the foundation structure.
One method is to install additional piles adjacent to the existing foundation and expand the foundation.

  By the way, when reinforcing with the additional pile, if the rigidity of the existing foundation and the additional pile is greatly different, how to accurately transmit the load to the additional pile becomes a problem.

For example, Patent Document 1 discloses a method of arranging reinforcing bars and studs for the purpose of securing shear strength at the joint of old and new concrete when an additional pile placed on the outer periphery of an existing foundation is integrated with the existing foundation by concrete. is suggesting.
JP-A-8-296209

However, in the method disclosed in Patent Document 1, when the rigidity of the existing foundation pile and the additional pile is greatly different, the upper vertical load is increased and hardly transmitted to the pile, and most of the load flows to the existing foundation side. A sufficient reinforcing effect cannot be obtained.
Therefore, when there is no margin for the supporting capacity of the existing foundation, there is a risk that the foundation will sink due to an increase in the upper vertical load.

  The present invention advantageously solves the above problem, and ensures that the upper vertical load to be borne by the additional piles is ensured regardless of the rigidity of the additional piles and the difference in rigidity ratio with the existing foundation piles. It aims at proposing the foundation reinforcement method of the structure which can be transmitted.

Now, as a result of intensive research to solve the above problems, the inventors have loaded the desired vertical downward load on the pile in advance by using the weight of the existing foundation (and the mounting equipment) as a reaction force source and increasing it with a jack or the like. In addition, the knowledge that the intended purpose was advantageously achieved by constructing the housing in this state was obtained.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
(1) A method of reinforcing the foundation of the structure by installing additional piles adjacent to the existing foundation of the structure,
A first step of driving an additional pile adjacent to the existing foundation;
A second step of constructing the upper part of the additional foundation integrated with the existing foundation above the additional pile;
A third step of adding a predetermined amount of preload load to the pile by increasing the weight of the existing foundation as a reaction force source through the upper part of the additional foundation;
A method for reinforcing a foundation of a structure, comprising a fourth step of constructing an additional foundation lower portion while maintaining the preload load.

(2) The structure according to (1) above, wherein a reinforcing member having a strength that resists a shearing force and a bending moment generated during preloading is installed at a joint between the upper part of the additional foundation and the existing foundation. Foundation reinforcement method.

(3) At the time of loading the preload load, first, a preload load is loaded on an additional pile by a combination of an oil pump and an insertion jack, and after the preload load reaches a predetermined value, the preload load is replaced with a mechanical jack. The method for reinforcing a foundation of a structure according to (1) or (2) above, wherein the structure is embedded in a housing as it is.

(4) The structure according to (1), (2) or (3) above, wherein a material having no shrinkage specification such as expanded concrete or non-shrinkage grout is used as a material for constructing the lower part of the additional foundation. Basic reinforcement method for objects.

(5) When loading the preload load, by measuring the displacement and strain of the additional pile at the stage where the load load step is increased to the preload load, it is performed while checking the vertical bearing capacity of the additional pile. The method for reinforcing a foundation of a structure according to any one of (1) to (4), characterized in that it is characterized in that

  According to the present invention, when reinforcing the foundation structure of the structure with the additional pile, even if the rigidity of the existing foundation pile and the additional pile of the structure is greatly different, the increase in the upper vertical load is increased by the pile. With proper support, settlement of the existing foundation can be effectively avoided.

Hereinafter, this invention is demonstrated concretely for every process.
As a representative example, the case where the foundation structure of a blast furnace is reinforced is described.
FIG. 1 schematically shows the basics of a blast furnace. In the figure, reference numeral 1 is an existing foundation, and 2 is a reinforcing portion.
In this example, the case where a reinforcement part is provided in four places around the existing foundation is shown.

(First step)
In the present invention, first, the pile 3 is placed on the reinforcing portion 2. FIG. 2 shows the state. About the number of the additional piles 3, what is necessary is just to determine suitably according to the load which should be supported with each additional pile 3 with respect to the reinforcement vertical support force (henceforth only reinforcement strength) which reinforces the vertical support force of an existing foundation.
In this example, the case where five additional piles are laid in each reinforcement part 2 is shown.

(Second step)
Next, as shown in FIG. 3, a so-called drilled reinforcing bar is formed by making a hole in the outer periphery of the footing 4 of the existing foundation 1 and embedding the reinforcing bar 5.
As described above, by using the reinforcing bar 5 as the reinforcing member, it is possible to obtain a strength sufficient to resist a shearing force and a bending moment generated at the time of preload described later. Here, the diameter and the number of reinforcing bars to be embedded may be appropriately determined according to the required reinforcement strength.
Then, this part is solidified with concrete to construct the additional foundation upper part 6. This state is shown in FIG.

(Third step)
Next, as shown in FIG. 5, a jack is inserted into the gap between the above-mentioned additional foundation upper portion 6 and the additional pile 3 that has been placed, and the weight of the existing foundation 1 is increased as a reaction force source and a predetermined amount is added to the pile 3. Load a preload load. Here, the predetermined amount of preload load is a preload load that each additional pile 3 should bear according to the reinforcement strength.
When loading the preload load, the oil pump and the insertion jack are combined to load the preload load to a predetermined value. Thus, after a predetermined amount of preload load is loaded on the additional pile, as shown in FIG. 6, this load is switched to support by a giraffe jack 7 which is a so-called mechanical jack using rotation of a screw, The insertion jack is carried outside.
Thus, the preload load on the additional pile is supported only by the giraffe jack 7.

(4th process)
In this state, that is, in a state where the preload load is supported by the giraffe jack 7, both the giraffe jack 7 and the gap between the additional foundation upper part 6 and the additional pile 3 that has been laid are made of non-shrinkable material such as expanded concrete. Solidify and build the expansion base lower part 8. This state is shown in FIG.

As described above, in the present invention, the preload load is increased by the jack, and the additional foundation lower portion 8 is constructed by solidifying with concrete while being loaded on the pile, but the final preload load support is a mechanical jack. This is done with an inexpensive giraffe jack that uses the rotation of the screw, and expensive oil pumps and insertion jacks can be used repeatedly, so the equipment cost is also minimal.
Here, the mechanical jack refers to a jack using the rotation of the above-mentioned screw that operates by mechanical coupling without using a hydraulic medium such as a hydraulic medium. With these jacks, the support of the preload load is maintained even if it is embedded in concrete. In this respect, the hydraulic jacks are not only expensive, but there is a risk that liquid leakage may cause a problem in sustaining the preload load.

  Moreover, as a material for constructing the additional foundation lower part 8, it is preferable to use non-shrinkable expanded concrete or non-shrinkable grud. This is because the use of such non-shrinkable material advantageously prevents unloading of the preload load and at the same time ensures the integration of the upper part of the additional foundation and the lower part of the additional base.

In the present invention, it is only necessary to load a preload load for the increase resistance, but at the stage of increasing the load load to the preload load, by measuring the displacement and strain of the increase resistance, It is possible to reinforce the foundation while confirming the vertical bearing capacity characteristics.
In other words, because a large amount of equipment costs are required, a load test that can only be performed on a small number of piles is carried out in order to increase the load load up to the preload load. By performing the measurement, it is possible to perform the same loading test for all the reinforcements, and there is an advantage that the reliability of the reinforcement work is increased.
Usually, the pile bearing capacity design is performed by multiplying the load actually applied (design load) by 2 to 3 times the safety factor. This is a safety factor that is adopted because the bearing capacity of the actual piles varies considerably due to deviation from the design conditions of the ground properties and non-uniformity. And for the resistance after construction, the bearing capacity check by a loading test or the like is not normally performed.
In the present invention, since a preload load can be applied between the upper part of the additional foundation and the additional pile, a load test can be easily performed in the process of applying the preload load to the additional pile using the preload load loading equipment. The reliability of the reinforcement work will increase.

  In addition, when the load is increased to the preload load, the measurement of displacement and strain of the additional pile is performed in steps of about 5t to 20t pitch so as to correspond to a general mine loading test procedure. It is to measure the displacement and strain of the additional pile at the necessary part of the process. In a normal loading test, the load is applied to the plastic region of the pile, and the yield load and the ultimate load are obtained, but in the case of the present invention, the purpose is different, so a predetermined amount of preload load necessary for reinforcement is used as the final load. When the pre-load load is reached and the anti-resistance behavior maintains elasticity, it can be confirmed that the base has sufficient reliability.

According to the present invention, when the upper vertical load is increased when renovating a large structure such as a blast furnace, the increase in the upper vertical load can be accurately supported by the additional piles. There are no problems such as sinking.
Further, the present invention is advantageously adapted not only for the renovation of large structures such as the above-described blast furnaces but also for the reinforcement of foundations such as piers, steel towers and tanks.

It is a schematic diagram which shows the foundation of a blast furnace. It is the figure which showed the state which increased the pile in the reinforcement part. It is the figure which showed the state which installed the drilling rebar in the footing part of the existing foundation. It is the figure which showed the state which constructed the extension foundation upper part. It is the figure which showed the state which inserted the jack in the clearance gap between the upper part of an expansion foundation, and the additional pile piled, and loaded the predetermined amount of preload load into the additional pile. It is the figure which showed the state which switched the loaded preload load to the support by a giraffe jack. It is the figure which showed the state which constructed the extension foundation lower part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Existing foundation 2 Reinforcement part 3 Additional pile 4 Footing 5 Reinforcement 6 Upper part of extension foundation 7 Kirin jack 8 Lower part of extension foundation

Claims (5)

A method of reinforcing the foundation of the structure by installing additional piles adjacent to the existing foundation of the structure,
A first step of driving an additional pile adjacent to the existing foundation;
A second step of constructing the upper part of the additional foundation integrated with the existing foundation above the additional pile;
A third step of adding a predetermined amount of preload load to the pile by increasing the weight of the existing foundation as a reaction force source through the upper part of the additional foundation;
A method for reinforcing a foundation of a structure, comprising a fourth step of constructing an additional foundation lower portion while maintaining the preload load.   The method of reinforcing a foundation of a structure according to claim 1, wherein a reinforcing member having a strength that resists a shearing force and a bending moment generated during preloading is installed at a joint portion between the upper part of the additional foundation and the existing foundation. .   When loading the preload load, first, a preload load is loaded on the pile by adding a combination of an oil pump and an insertion jack. After the preload load reaches a predetermined value, the preload load is replaced with a mechanical jack, and the housing is left as it is. 3. The method for reinforcing a foundation of a structure according to claim 1 or 2, wherein the structure is embedded in the structure.   The method for reinforcing a foundation of a structure according to claim 1, 2 or 3, wherein a material having no shrinkage specification such as expanded concrete or non-shrinkage grout is used as a material for constructing the lower part of the additional foundation.   The loading of the preload load is performed while confirming the vertical bearing capacity of the increased pile by measuring the displacement and strain of the pile after increasing the load load to the preload load. Item 5. A method for reinforcing a foundation of a structure according to any one of Items 1 to 4.

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