JP5041223B2 - Reinforcement method and structure of existing structure foundation - Google Patents

Description

  The present invention relates to a method for reinforcing an existing structure foundation and a foundation reinforcing structure.

In recent years, pile foundation structures such as footings such as bridges and viaducts have been increasing in size, and the number of cases with an important position in urban functions is increasing. Therefore, in order to prevent damage and destruction of the pile foundation structure due to a large-scale earthquake, the outer foundation steel pile supporting the existing pile structure is reinforced by winding an externally wound steel pipe or added to the pile structure. By doing so, a method of making a structure capable of withstanding the horizontal force of the ground caused by a large-scale earthquake has been performed (see, for example, Patent Documents 1 and 2).
JP 63-11720 A JP-A-10-131176

However, the conventional method for reinforcing a pile foundation structure has the following problems.
In other words, when constructing an outer foundation pile that supports an existing structure by wrapping an externally wound steel pipe or adding an additional pile, for example, the existing foundation pile is excavated to the extent that the pile head of the existing foundation pile is exposed and the existing foundation pile is exposed. It was necessary to refill the pile after reinforcing it, but it was necessary to refill it while compacting it to ensure a predetermined strength. In particular, the work space under the existing structure has a drawback that the reinforced piles are arranged, the work space is narrow, and the work efficiency is lowered. And if the compaction at this time is insufficient, the reinforced pile and the existing structure may not be integrated, and there is a possibility that a reliable structure capable of withstanding the horizontal force caused by a large-scale earthquake may not be obtained. Therefore, there is a need for a construction method that does not require time and effort for backfilling, can simplify the construction, and can reliably reinforce the existing structure foundation, and there remains room for improvement in that respect.

  The present invention has been made in view of the above-described problems, and can reduce the construction cost by simplifying the construction, and can reinforce the existing structure foundation and the reinforcing structure. The purpose is to provide.

In order to achieve the above object, the existing structure foundation reinforcement method according to the present invention is a method of reinforcing an existing structure foundation supported by a pile, and includes a step of excavating the ground below the existing structure foundation, The excavation space formed by excavating the ground is used to construct a reinforcing pile that supports the existing structure foundation, and to backfill the excavation space with a solidified material, below the existing structure foundation In the present invention, the reinforcing pile and the solidified material are applied only to the outer peripheral portion, and liquefaction of the ground inside the outer peripheral portion is prevented .

Further, in the reinforcement structure of the existing structure foundation according to the present invention, the reinforcement structure of the existing structure foundation formed using the excavation space formed by excavating the ground below the existing structure foundation, and reinforcing piles supporting the existing structure foundation, so as to be integrated to the reinforcing pile and existing structures foundation, a solidifying material comprising backfilled excavation space, Ri Tona, solidifying material, the existing structure foundation It is formed only in the lower outer peripheral portion, and is characterized in that it has a structure that can prevent liquefaction of the ground inside the outer peripheral portion.

In the present invention, a excavation space is formed below the existing structure foundation, and after the reinforcement pile supporting the existing structure foundation is constructed using the excavation space as a work space, the excavation space is backfilled with a solidified material. The pile head of the reinforcing pile can be strengthened to ensure lateral resistance against the ground. And since the backfilled solidified material solidifies itself and develops strength, compaction can be simplified, and reinforcement in which the reinforcing pile and the existing structure foundation are integrated can be performed. Therefore, it is possible to realize a reinforcing structure that can reliably withstand horizontal force (earth pressure acting in the lateral direction) generated by a large-scale earthquake.
In addition, since the reinforcing pile is a reinforcement that resists the moment at the time of the earthquake, efficient reinforcement can be performed by constructing only the outer peripheral portion. And even if the upper ground layer is a sand layer with loose ground strength, the sand layer inside (center part) of the outer peripheral part is free from liquefaction and does not liquefy. It can be a structure that does not need to be performed.

Moreover, in the reinforcement method of the existing structure foundation which concerns on this invention, it is preferable to construct a ground side pressure resistance body to the position deeper than the depth of the excavated excavation space outside the existing structure foundation.
In the present invention, since the earth pressure of the ground can be borne by the ground side pressure resistor, the burden on the ground of the solidified material and the reinforcing pile located inside the ground side pressure resistor can be reduced. . In other words, the structure can withstand a larger earthquake. In addition, by constructing the ground side pressure resistance body before excavation below the existing structure foundation, the excavation space and the excavation space for approaching from the ground toward the excavation space are basically minimized. Therefore, the construction can be simplified.

In the method for reinforcing an existing structure foundation according to the present invention, in excavation below the existing structure foundation, the excavation space preferably has an outer excavation depth deeper than an inner excavation portion.
In the present invention, in the state where the excavation space below the existing structure foundation is backfilled with the solidified material, the strength of the outer portion of the excavation space is greater than that of the inner excavation portion, and the resistance in the height direction is increased. Therefore, the reinforcement structure can withstand a large-scale earthquake.

  Moreover, in the reinforcement method of the existing structure foundation based on this invention, it is preferable that a solidification material is fluidization processing soil.

  According to the reinforcement method and the reinforcement structure of the existing structure foundation of the present invention, after constructing the reinforcement pile using the excavation space formed below the existing structure foundation, the excavation space is backfilled with the solidified material and reinforced. While a pile and an existing structure foundation can be integrated, the pile head of a reinforcement pile can be strengthened and it can be set as the reinforcement structure which can ensure lateral resistance with respect to the ground reliably. And since the solidification material that backfills the excavation space is a material that simplifies compaction and secures strength, it can be simplified with less labor for construction, and residual soil generated at the site can be used. The construction cost can be reduced, and in that case, the construction cost can be reduced.

Hereinafter, the reinforcement method and reinforcement structure of the existing structure foundation by 1st embodiment of this invention are demonstrated based on FIG. 1 thru | or FIG.
1 is a sectional elevation showing a reinforcing structure of a footing according to the first embodiment of the present invention, FIG. 2 is a sectional elevation of a pile head of the existing foundation pile shown in FIG. 1, and FIGS. ) Is a cross-sectional view taken along line AA shown in FIG. 2, and is a view showing a joint structure of an outer winding reinforcing pipe, FIGS. 4A to 4C are process explanatory views showing a footing reinforcing method, and FIG. Fig. 6 is a vertical sectional view showing the press-fitted state of the externally wound reinforcing pipe, and Fig. 6 is a view showing a connection structure between the externally wound reinforcing pipe and the footing.

The code | symbol 1 shown in FIG. 1 is the reinforcement structure for reinforcing the footing 2 (existing structure foundation) of the reinforced concrete structure constructed in the ground.
In the reinforcing method of the footing 2 according to the first embodiment, the work space R1 (excavation space) is formed by excavating the ground below the footing 2, and the work space R1 is used to position the footing 2 in the excavation region. The pile heads 3a of a plurality of existing foundation piles 3, 3,... Are exposed, the outer foundation reinforcement piles 4 are wound around the existing foundation piles 3, 3,. The completed work space R1 is backfilled with fluidized soil 6 (solidifying material).

Here, the reinforcing structure of the footing 2 will be described more specifically.
As shown in FIG. 2, the reinforcing structure of the footing 2 includes the outer foundation reinforcing pile 4 having a larger diameter than the existing foundation pile 3 provided on the outer periphery of the existing foundation pile 3 that supports the footing 2 from below, From a filling material 5 such as mortar filled in a gap between the outer winding reinforcing tube 4 and a fluidized soil 6 provided integrally with the pile head 3a in a predetermined region (work space R1) below the footing 2. It is configured. Here, the existing foundation pile 3 around which the outer winding reinforcement pipe 4 is wound via the filler 5 corresponds to the reinforcement pile of the present invention. Moreover, in the following description, the existing foundation pile 3 reinforced in the state where the outer winding reinforcement pipe 4 is wound is simply described as “existing foundation pile 3” as necessary.

  As shown in FIGS. 3 (a) to 3 (c), the outer-wrapped reinforcing pipe 4 is provided on the existing foundation pile 3 by combining a pair of reinforcing pipes 41 and 42 that are divided into half cracks in the longitudinal direction. It is. And in this 1st embodiment, the outer winding reinforcement pipe | tube 4 is installed in the upper part to which bending acts largely in the length direction of the existing foundation pile 3. As shown in FIG. Here, as a joint for connecting the half cracked reinforcing pipes 41 and 42, as shown in FIG. 3 (a), a welded joint (welded joint 4A) is used, and as a joint 4B shown in FIG. 3 (b). For example, a mesh joint 4C formed by engagement between engagement portions formed in a substantially key shape can be employed.

  As the fluidized soil 6 shown in FIG. 1, for example, treated soil fluidized by kneading muddy water containing a large amount of water and sand and a solidifying material such as cement can be used. Such fluidized soil 6 has high fluidity, can be backfilled without being compacted, and can secure a predetermined strength, so that the construction can be simplified ( Will be described later). And as the fluidization processing soil 6, the processing soil generated on-site can be used.

  In the reinforcing structure 1 of the footing 2 configured as described above, a work space R1 is formed below the footing 2, and the outer reinforcement pipe 4 is attached to the existing foundation pile 3 that supports the footing 2 using the work space R1. After winding, by refilling the work space R1 with the fluidized soil 6, the pile head 3a of the existing foundation pile 3 can be strengthened to ensure lateral resistance against the ground.

  Since the fluidized soil 6 that has been backfilled has high fluidity as described above and can secure a predetermined strength with almost no compaction, the existing fluidized soil 6 can be obtained by a simplified and simple construction. It has a structure capable of performing reinforcement by integrating the foundation pile 3 and the footing 2. For this reason, a reinforcing structure that can reliably withstand horizontal force (earth pressure acting in the lateral direction) generated by a large-scale earthquake can be obtained.

Next, the procedure of the reinforcing method of the footing 2 will be described in more detail with reference to FIG.
As shown to Fig.4 (a), the process of excavating the ground below the footing 2 is performed first so that the pile head 3a of the existing foundation pile 3 may be exposed. Specifically, it accesses from the ground and excavates the periphery of the footing 2 and the ground below. The excavation area at this time is an excavation space indicated by a symbol T shown in FIGS. 1 and 4A.

  And the pile head 3a of several existing foundation piles 3, 3, ... is exposed by excavation, and working space R1 (two-dot chain line in a figure) for performing reinforcement construction is ensured. The size of the work space R1 is a space where a press-fitting work (described later) for reinforcing the existing foundation pile 3 in a state where an outer-wrapped reinforcing pipe 4 described later is buried in the ground is possible. The bottom board 7 is formed in the.

  Next, as shown in FIG.4 (b), using the work space R1, the process of winding the outer winding reinforcement pipe | tube 4 around several existing foundation piles 3, 3, ... is performed. Specifically, in the work space R1, the outer periphery of the existing foundation pile 3 is sandwiched between half-strength reinforcing pipes 41 and 42 (see FIG. 3) having a predetermined height, and both the reinforcing pipes 41 and 42 are shown in FIG. ) To (c) are joined by any of the joints, and the joined outer winding reinforcement pipe 4 is press-fitted along the existing foundation pile 3 into the ground below the bottom board 7 of the work space R1.

  As shown in FIG. 5, the press-fitting method at this time is such that a flange 43 projecting radially outward along the circumferential direction is fixed to the upper end portion 4 a of the outer winding reinforcing tube 4, and the flange 43 and the footing 2 are A plurality of hydraulic jacks 8, 8,... Are interposed therebetween, and a reaction force is applied to the footing 2 to extend the hydraulic jack 8 to press-fit the outer winding reinforcing pipe 4 toward the ground. Then, the externally wound reinforcing tube 4 press-fitted into the ground and the externally wound reinforcing tube 4 to be press-fitted next are added and press-fitted by the above-described procedure. And the outer winding reinforcement pipe | tube 4 is arrange | positioned in the upper part to which the bending of the existing foundation pile 3 located in the ground from the bottom board 7 acts largely, repeating these press injection work. In addition, at the time of press-fitting work, the earth and sand in the gap between the existing foundation pile 3 and the outer winding reinforcing pipe 4 is cut and removed by using a jet (not shown) that jets high-pressure water.

  And as shown in FIG.4 (b), after pressing the outer winding reinforcement pipe | tube 4 in the underground part of the existing foundation pile 3, the outer winding reinforcement pipe | tube 4 is wound around the pile head 3a exposed to work space R1. And the filler 5 is inject | poured into the clearance gap between the existing foundation pile 3 and the outer winding reinforcement pipe | tube 4 (refer FIG. 6). Thereby, the existing foundation pile 3 is reinforced by being integrated with the outer winding reinforcement pipe 4.

  Further, as shown in FIG. 6, a fixing bracket 44 is fixed along the circumferential direction on the upper side surface of the constructed outer winding reinforcing tube 4, and the fixing bracket 44 and the lower surface 2 a of the footing 2 are fixed by an anchor 9. Thereby, the outer winding reinforcement pipe 4 wound around the existing foundation pile 3 is fixed to the footing 2.

Subsequently, as shown in FIG. 4 (c), a process of refilling the working space R 1 below the footing 2 with the fluidized soil 6 is performed. In the first embodiment, as shown in FIGS. 1 and 4C, the fluidized soil 6 is backfilled in the entire area of the excavation space T including the work space R1.
Thereby, since the pile heads 3a of the existing foundation piles 3, 3,... Are buried in the fluidized soil 6, the lateral resistance of the pile heads 3a can be increased. Then, the pile head 3a and the footing 2 are integrated by the fluidized soil 6, so that the ground resistance in the reinforcing structure 1 can be expected.

As described above, in the reinforcement method and the reinforcement structure of the existing structure foundation according to the first embodiment, the outer reinforcement pipe 4 is wound around the existing foundation pile 3 using the work space R1 formed below the footing 2. The existing foundation pile 3 and the footing 2 reinforced by backfilling the work space R1 with the fluidized soil 6 can be integrated and the pile head 3a of the existing foundation pile 3 is strengthened. Thus, a reinforcing structure capable of reliably ensuring lateral resistance to the ground can be obtained.
And since the fluidized soil 6 that refills the work space R1 is a material that has high fluidity and simplifies compaction to ensure a predetermined strength, it is simplified with less labor for construction. In addition, it is possible to perform construction using the remaining soil generated at the site, and the construction cost can be reduced.

Next, a modification of the first embodiment of the present invention and the second and third embodiments will be described with reference to FIGS. 7 to 12, which are the same as the first embodiment described above. Alternatively, the same reference numerals are used for the same members and parts, and the description thereof is omitted, and a configuration different from the first embodiment will be described.
FIG. 7 is an elevational cross-sectional view showing a footing reinforcement structure according to a first modification of the first embodiment, FIG. 8 is an elevational sectional view showing a footing reinforcement structure according to the second modification, and FIG. FIG. 10 is an elevational sectional view showing a footing reinforcement structure according to a fourth modification, and FIG. 10 is a vertical sectional view showing a footing reinforcement structure according to a fourth modification.

  As shown in FIG. 7, in the first modification, a steel sheet pile 10 that forms a ground lateral pressure resistor is constructed outside the footing 2 to a position deeper than the depth of the excavated work space R2 (excavation space). It is. That is, the steel sheet pile 10 is arranged so as to surround the side periphery of the footing 2 continuously or at a predetermined interval. The other structure, that is, the structure in which the existing foundation pile 3 is reinforced by winding the outer winding reinforcement pipe 4 and the fluidized soil 6 is backfilled in the work space R2 is the same as that of the first embodiment. It is the same.

  Further, in the second modified example shown in FIG. 8, instead of the steel sheet pile 10 of the first modified example in FIG. 7, a ground improvement body 11 (a ground side pressure resistor) is formed continuously or at a predetermined interval. The ground improvement body 11 is constructed to a position deeper than the depth of the excavated work space R3 (excavation space) so as to surround the outside of the footing 2. As the ground improvement body 11, a material having higher rigidity than the surrounding ground such as a material obtained by mixing and solidifying an improvement material such as a cement-based solidification material is used.

In the 1st modification and the 2nd modification, since the earth pressure of a ground can be borne by the steel sheet pile 10 or the ground improvement body 11, the fluidization processing soil located inside the steel sheet pile 10 or the ground improvement body 11 6 and the load on the ground of the reinforced existing foundation pile 3 can be reduced. In other words, the structure can withstand a larger earthquake.
Further, by excavating the steel sheet pile 10 or the ground improvement body 11 before excavating the lower part of the footing 2, excavation for approaching from the ground toward the work spaces R2, R3 and the work spaces R2, R3 basically. Excavation may be performed with a minimum space (not shown), and the construction can be simplified and the construction period can be shortened.

  Next, in the 3rd modification shown in FIG. 9, the outer winding reinforcement pipe | tube 4 is attached to the upper part to which bending of the existing foundation pile 3 acts largely in 1st Embodiment mentioned above and a 1st and 2nd modification. Although the wound reinforcement is performed, it has a reinforcing structure in which the outer winding reinforcement pipe 4 is wound only on the pile head 3a exposed by excavating the work space R1. In the case of the third modified example, it is applied to a case where the resistance to the ground is larger than a predetermined value for the existing foundation pile 3 that is not reinforced, and the existing foundation pile 3 that is located in the ground from the bottom 7 of the work space R1. On the other hand, since the outer winding reinforcement tube 4 is not wound, the press-fitting work performed using the work space R1 can be omitted.

Next, as shown in FIG. 10, the fourth modification is a structure in which the outer winding reinforcement pipe 4 (see FIG. 1) is not wound around the existing foundation pile 3, and the existing foundation piles 3, 3 adjacent to each other are not wound. This is a reinforcement structure in which an additional pile 3 ′ (reinforcement pile) is placed between the two. This additional pile 3 'is constructed by a method in which a work space R1 excavated in advance is used and a pile having a predetermined length is press-fitted and installed in the same manner as the press-fitting method described above. And after giving additional pile 3 ', work space R1 is backfilled with the fluidization processing soil 6. FIG. That is, in the fourth modified example, the existing foundation pile 3 and the additional pile 3 ′ have a reinforcing structure integrated with the footing 2 by the fluidized soil 6.
In addition, in 1st embodiment of this invention and each modification, the outer winding reinforcement pipe | tube 4 (reinforcement pile) is installed in the upper part of the existing foundation pile 3 from which a bending will act largely by a horizontal direction force. However, the present invention is not limited to this, and if it is installed over the entire length of the existing foundation pile, the vertical support force will increase. For example, when the weight of an existing structure increases due to refurbishment, Can be considered.

Next, FIG. 11 is an elevational sectional view showing the reinforcing structure of the footing according to the second embodiment of the present invention.
As shown in FIG. 11, the reinforcing structure 1 of the footing 2 according to the second embodiment is such that, in excavation below the footing 2, the work space R4 has the excavation depth of the outer peripheral portion R ′ of the other excavation part. The structure is deeper than the depth. In other words, the backfilled fluidized soil 6 has a structure in which the height direction of the outer peripheral portion 2b is larger than that of the other excavated portions.
In the second embodiment, in the state where the work space R4 below the footing 2 is backfilled with the fluidized soil 6, the strength of the outer peripheral part of the work space R4 is greater than the other excavation parts, Since the resistance in the height direction can be increased, a reinforcing structure that can withstand a large-scale earthquake can be obtained.

FIG. 12 is a vertical sectional view showing a footing reinforcing structure according to the third embodiment of the present invention.
As shown in FIG. 12, in the third embodiment, a work space R <b> 5 is formed only on the outer peripheral portion R ′ below the footing 2, and external winding reinforcement is performed on the existing foundation pile 3 via the filler 5. The tube 4 is wrapped and reinforced, and the work space R5 is backfilled with the fluidized soil 6 to provide a reinforced structure.
In the third embodiment, the existing foundation pile 3 reinforced at the outer peripheral portion R ′ serves as a reinforcement that resists the moment at the time of the earthquake. Therefore, efficient reinforcement can be performed by constructing only the outer peripheral portion. it can. Even if the upper ground layer is a sand layer with a loose ground strength (two-dotted line indicated by reference numeral 12 shown in FIG. 12), the sand layer on the inner side (center part 13) of the outer peripheral portion R ′ is free of pore water. Since it is eliminated and liquefaction does not occur, a structure that does not require ground improvement or the like can be obtained.

As mentioned above, although the 1st thru | or 3rd embodiment and the 1st-4th modification of the reinforcement method of the existing structure foundation and reinforcement structure by this invention were demonstrated, this invention is limited to said embodiment. It can be changed as appropriate without departing from the scope of the invention.
For example, in the present embodiment, the outer foundation reinforcing pile 3 is wound around the existing foundation pile 3 as the reinforcing pile, or the method of constructing the additional pile 3 ′ is not limited to these. For example, the reinforcement pile by the ground improvement body formed by stirring the ground may be sufficient. In short, the existing structure foundation such as footing 2 is added and reinforced with a reinforcing pile including a pile, and the reinforcing pile and footing 2 are integrated by fluidized soil 6 backfilled in the work space. It only has to be constructed. In other words, the piles may be appropriately reinforced according to the construction conditions such as the shape and size of the footing 2, the number of existing foundation piles, the external dimensions, the geology of the ground, and the ground strength.
The approach method from the ground for excavating the work space, the size of the excavation area at the time of the approach, and the like are also arbitrary.

  Moreover, about the ground side pressure resistance body (steel sheet pile 10 and ground improvement body 11) in the 1st modification and 2nd modification of 1st embodiment of this invention, it is 3rd of 1st embodiment. In addition, the present invention can be applied to the fourth modified example and the second and third embodiments, and further, the existing structure is not excavated or backfilled with a solidified material. The ground side pressure resistor may be applied alone to the outside of the foundation. Then, as the solidifying material in each embodiment, in addition to fluidized soil, poor blended concrete, poor blended mortar, soil cement, and the like can be considered.

It is an elevation sectional view showing the reinforcement structure of the footing by a first embodiment of the present invention. It is a vertical sectional view of the pile head of the existing foundation pile shown in FIG. (A)-(c) is the sectional view on the AA line shown in FIG. 2, Comprising: It is a figure which shows the joint structure of an outer winding reinforcement pipe | tube. (A)-(c) is process explanatory drawing which shows the reinforcement method of the existing structure foundation. It is an elevation sectional view showing the press fit state of an outer winding reinforcement pipe. It is a figure which shows the connection structure of an outer winding reinforcement pipe | tube and a footing. It is an elevation sectional view showing the reinforcing structure of the footing by the 1st modification of this 1st embodiment. It is an elevation sectional view showing the reinforcement structure of the footing by the 2nd modification of this 1st embodiment. It is an elevation sectional view showing the reinforcement structure of the footing by the 3rd modification of this first embodiment. It is an elevation sectional view showing the reinforcement structure of the footing by the 4th modification of this 1st embodiment. It is an elevation sectional view showing the reinforcement structure of a footing by a second embodiment of the present invention. It is an elevation sectional view showing the reinforcement structure of the footing by a third embodiment of the present invention.

Explanation of symbols

1 Reinforced structure 2 Footing (existing structure foundation)
3 Existing foundation pile 3 'Additional pile (reinforcement pile)
3a Pile head 4, 41, 42 Outer winding reinforcement pipe 5 Filler 6 Fluidized soil (solidified material)
10 Steel sheet pile (Ground side pressure resistor)
11 Ground improvement body (ground side pressure resistance body)
R1-R5 work space (excavation space)

Claims (5)

A method for reinforcing an existing structure foundation supported by a pile,
Excavating the ground below the existing structure foundation;
Using the excavation space formed by excavating the ground, constructing a reinforcing pile that supports the existing structure foundation;
Backfilling the excavation space with a solidified material ,
Under the existing structure foundation, the reinforcing pile and the solidified material are applied only to the outer peripheral portion thereof, and liquefaction of the ground inside the outer peripheral portion is prevented . Reinforcement method.   2. The reinforcement of an existing structure foundation according to claim 1, wherein a ground side pressure resistor is constructed outside the existing structure foundation to a position deeper than a depth of the excavated space excavated. Construction method. 2. The existing structure foundation according to claim 1, wherein in the excavation below the existing structure foundation, the excavation space has an outer excavation depth deeper than an inner excavation portion. Reinforcement construction method.   The reinforcing method for a foundation of an existing structure according to any one of claims 1 to 3, wherein the solidifying material is fluidized soil. A reinforcement structure for an existing structure foundation formed using an excavation space formed by excavating the ground below the existing structure foundation,
A reinforcing pile supporting the existing structure foundation;
The reinforcing pile and so as to be integrated into the existing structure foundation, a solidifying material comprising backfilled into the excavation space, Ri Tona,
The reinforcing structure of the existing structure foundation, wherein the solidifying material is formed only in an outer peripheral portion below the existing structure foundation and has a structure capable of preventing liquefaction of the ground inside the outer peripheral portion. .

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