JP5439918B2 - Pier foundation structure and construction method - Google Patents

Description

  The present invention relates to a foundation structure of a pier such as a road or a railway.

  In general bridge construction, temporary steel sheet piles are first driven, then foundation piles are driven, floor digging, pile head treatment is performed and concrete footings are constructed, and bridge piers are constructed on the footings. Is done. Thereafter, the temporary steel sheet pile is removed and backfilled to complete. In this construction process, the work of placing and removing the temporary steel sheet pile is time consuming and costly. Then, the method of utilizing this steel sheet pile effectively is proposed.

  The invention described in Patent Document 1 (Japanese Patent Laid-Open No. 2000-129696) is a pile foundation structure in which a footing construction planned position is closed by a rigid sheet pile and a footing is constructed by coupling with the sheet pile. In this invention, the periphery of the footing is closed with a rigid sheet pile, and the rigid sheet pile is left in the state of being combined with the footing, so even if a horizontal load acts on the footing during an earthquake, the horizontal load Can be received by a sheet pile, and can have a large passive resistance, can reduce the amount of movement of the footing against a horizontal load, and can improve earthquake resistance. Furthermore, the area required for construction can be reduced.

Further, the invention described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-32065) is a pile in which a plurality of piles that support a structure are enclosed, and a partition wall is provided in the ground to partition the piles so as not to contact the piles. It is a pile foundation reinforcement structure in which a solidified body is formed by injecting a chemical into the bulkhead inner ground in the depth direction underground part to connect the piles together. In such a structure, the structure near the ground or near the ground and the solidified body are connected by a steel sheet pile, and the plurality of piles are constrained by the solidified body in the depth direction underground portion, thereby increasing the rigidity of the plurality of piles. For example, even if a liquefaction phenomenon occurs in the ground due to an earthquake or the like, bending strain generated at the joint between the pile and the structure is greatly suppressed.
In addition, it is possible to significantly reduce the construction cost compared to the conventional high-pressure injection method, and it is possible to ensure sufficient quality because the solidified body is built limitedly inside the partition wall in the ground It is going to be.

Moreover, the invention described in Patent Document 3 (Japanese Patent Laid-Open No. 2007-303099) forms a polygonal side between a pile having a vertex arranged on a vertex or a vertex and a side of the polygon, and the arranged pile. And a steel sheet pile having joints arranged in this manner, and a base structure in which a time-curable material is filled inside a polygon formed by fitting a pile and a steel sheet pile by a joint.
According to the present invention, a steel sheet pile is provided between adjacent piles, and the pile and the steel sheet pile are fitted and integrated with the footing through the connecting material, thereby achieving the following effects.
When an earthquake occurs, it is possible to resist the stress generated by the earthquake by the tip support force of the pile, the peripheral frictional force of the pile and the steel sheet pile, and the passive resistance of the pile and the steel sheet pile. In addition, the foundation can be downsized, the required site can be reduced, and the amount of time-hardening material such as concrete placed can be reduced. In addition, it can resist the rotation due to horizontal forces during an earthquake without increasing the number, diameter, and strength of the piles that make up the foundation, and also reduce the stress generated in the piles due to horizontal forces and bending moments. The thickness of the pile can be reduced, and the earthquake resistance with high reliability is demonstrated at low cost.

JP 2000-129696 A JP 2007-32065 A JP 2007-303099 A

The above-mentioned patent documents 1 to 3 have the following problems.
First, in the invention of Patent Document 1, the sheet pile and the reinforcing bar constituting the footing are connected and integrated, but there is no specific description and it is unclear how to do it. Further, in the present invention, the footing itself is not reduced as compared with the prior art. Moreover, since there is no description about the connection method of sheet piles, it is doubtful whether the yield strength as the whole foundation can be improved by using a sheet pile effectively.

  In addition, in the invention of Patent Document 2, the chemical solution is injected. However, when the chemical solution is injected, there are large uncertain factors such as that a predetermined strength cannot be obtained depending on the ground, and the steel sheet pile is not provided with a rib or the like. It is difficult to integrate with the body. In addition, chemical injection causes concerns such as groundwater contamination. Similarly to Patent Document 1, in order to increase the rigidity of the pier base, it is necessary to devise such as increasing the footing.

  Furthermore, in invention of patent document 3, although it is a structure which connects a pile and a steel sheet pile, if a pile cannot be constructed in the position as planned, fitting with a pile and a sheet pile will be very difficult. In general, the pile core position slightly shifts and is difficult to correct even when it is shifted halfway, so it is extremely difficult to directly fit the pile and sheet pile. In this case, it is necessary to prepare a sheet pile that can change the sheet pile width, which causes an increase in cost.

  The present invention has been made to solve such a problem, has sufficient resistance during an earthquake, can prevent an increase in material costs such as piles and the foundation structure, and has excellent workability. The purpose is to provide a foundation structure.

(1) A bridge pier foundation structure according to the present invention is a foundation structure joined to a pier, and has a plurality of piles constructed at a predetermined interval, joints on side surfaces, and a pile head of the pile. An outer pipe installed on each pile so as to cover; and a sheet pile having a joint that fits the joint of the outer pipe; and fitting the joint of the sheet pile to the joint of the outer pipe, Are connected by the sheet pile, and a footing is constructed by placing concrete in a portion surrounded by the sheet pile .

(2) Further, in the above (1), the difference between the outer diameter of the pile and the inner diameter of the outer pipe is 10 cm or more.

(3) Moreover, in the thing as described in said (1), the internal diameter of the said outer tube is 1.2 times-2 times the outer diameter of the said pile, It is characterized by the above-mentioned.

(4) Moreover, the thing in any one of said (1) thru | or (3) WHEREIN: It filled with the sclerosing | hardenable fluid in the clearance gap between the said pile and an outer pipe | tube.
( 5) The construction method of the pier foundation structure according to the present invention is the construction method of the pier foundation structure described in (4) above,
The step of placing a plurality of piles, the step of expanding the ground of the pile heads that have been placed, the step of installing an outer pipe on the pile head, and fitting the joint of the sheet pile to the joint of the outer pipe The sheet piles were sequentially placed in such a manner that all the outer tubes were connected with each other by a sheet pile, the step of filling the gap between the pile and the outer tube with a curable fluid, and the sheet piles surrounded. The present invention is characterized by comprising a step of excavating a portion where the footing is constructed to build a footing and a pier.
(6) Moreover, it is a construction method of the pier foundation structure as described in said (4),
A step of placing an outer pipe, a step of sequentially placing the sheet piles so that a joint of a sheet pile is fitted to a joint of the outer pipe, and connecting all the outer pipes with a sheet pile, and the outer pipe The step of driving the pile so as to penetrate, the step of filling the gap between the pile and the outer tube with a curable fluid, and excavating the part where the footing surrounded by the sheet pile is constructed to make the footing and the pier And a process of building a structure.

  According to the present invention, since the outer pipe is installed on the pile head and the adjacent outer pipes are connected to each other by the sheet pile, any of the construction sequence of the pile construction and the sheet pile construction can be performed first. And even if it is a case where it constructs either first, an outer pipe and a sheet pile can be connected easily and it is excellent in workability.

It is a side view of the pier foundation structure which concerns on one embodiment of this invention. It is a horizontal sectional view which follows the arrow AA line in FIG. It is explanatory drawing of the other aspect of the pier foundation structure which concerns on one embodiment of this invention. It is explanatory drawing of a part of pier foundation structure which concerns on one embodiment of this invention, and is explanatory drawing of the pile head which installed the outer pipe | tube. It is explanatory drawing of a part of pier foundation structure which concerns on one embodiment of this invention, and is explanatory drawing of the connection part of an outer pipe and a steel sheet pile. It is explanatory drawing of a part of pier foundation structure which concerns on one embodiment of this invention, and is explanatory drawing of the other aspect of the connection part of an outer pipe and a steel sheet pile. It is explanatory drawing of the construction method of the pier foundation structure which concerns on this Embodiment. It is explanatory drawing of the other aspect of the construction method of the pier foundation structure which concerns on this Embodiment.

[Embodiment 1]
As shown in FIG. 1, the pier foundation structure 1 according to the present embodiment is joined to a pier 3, and is composed of four piles 5 constructed at a predetermined interval and a joint 7 on a side surface. (See FIGS. 4 and 5), and a sheet pile 13 having an outer tube 9 installed on each pile 5 so as to cover a pile head of the pile 5 and a joint 11 fitted to the joint 7 of the outer tube 9. The joint 11 of the sheet pile 13 is fitted to the joint 7 of the outer pipe 9, and the outer pipes are connected to each other by the sheet pile 13 so as to have a rectangular shape in plan view.
Hereinafter, each configuration will be described in detail.

<Pile>
The piles 5 are constructed at a predetermined interval. In the example shown in FIGS. 1 and 2, the number of piles 5 is four, but the number and arrangement thereof can be appropriately selected such as adapting to footing. The cross-sectional shape of the arrow AA as shown in FIG. For example, as shown in FIG. 3, even if the number of piles 5 is four as in the case of FIG. 2, a curved sheet pile 13 is used, or the joint 11 of the sheet pile 13 is joined at a predetermined angle ( By fitting), it can be made circular in plan view.

  As a support form of the pile 5, the tip may be stopped by a strong support layer or an intermediate layer, or may be stopped by a soft layer as a friction pile. Moreover, as a kind of the pile 5, you may apply what kind of pile, such as a steel pipe pile, a cast-in-place pile, and a ready-made concrete pile.

<Outer tube>
As shown in FIG. 4, the outer pipe 9 is installed so as to cover the pile head 5a of the pile 5, and the pile head 5a and the outer pipe 9 have a double pipe structure. The length of the overlapping portion of the pile head 5a and the outer tube 9 is preferably equal to or greater than the pile diameter d. The pile head 5a may be extended to the footing position by penetrating the outer tube 9, and in that case, the cross-sectional rigidity is increased by the outer tube 9 and the pile 5, which is advantageous for earthquake resistance.

The inner diameter of the outer tube 9 is preferably about 1.2 to 2 times the outer diameter of the pile 5. Alternatively, the difference between the inner diameter of the outer tube 9 and the outer diameter of the pile head 5a is preferably 10 cm or more, and more preferably 20 cm or more.
Thus, by providing a difference between the inner diameter of the outer tube 9 and the outer diameter of the pile 5, or by providing a difference between the inner diameter of the outer tube 9 and the outer diameter of the pile head 5a, the outer tube 9 and the pile head 5a As a result, a predetermined gap is formed between the two outer pipes 9, so that when the sheet pile 13 is connected between the adjacent outer pipes 9, the position can be freely adjusted within the range of the gap, and the workability is excellent. Since the construction accuracy of a general pile is about 10 cm, it is difficult to connect the sheet pile 13 directly to the pile head 5a as in the invention of Patent Document 3, so that the construction accuracy of the pile is managed more strictly. It is necessary and the workability becomes worse. On the other hand, in the present invention, there is a gap between the pile head 5a and the outer tube 9, and this gap has a function of absorbing the pile construction error, and therefore the pile construction accuracy is more than necessary. There is no need to be strict, and the construction is extremely easy and efficient.

The length of the outer tube 9 is about 2D to 10D of the outer tube diameter D.
The outer tube 9 is preferably a steel tube, but may be a steel tube-wound concrete as long as the joint 7 that can be joined to the sheet pile 13 is attached.

The space between the pile head 5a and the outer tube 9 is preferably filled with a curable fluid 15 such as concrete, mortar, or soil cement as shown in FIG. In this case, as shown in FIG. 4, the pile head 5a and the outer tube 9 can be integrated with each other by providing the protrusions 17 on the outer surface of the pile head or the inner surface of the outer tube, thereby facilitating the transmission of the load. be able to.
If the distance between the pile head 5a and the outer tube 9 is reduced and the upper and lower sides are restrained, load transmission is performed using local soil or sand as a filler to fill the gap between the pile head 5a and the outer tube 9. It is also possible to do.
The gap between the outer tube 9 and the pile head 5a may be displaced as one side contacts when the sheet pile 13 is connected. Even in this case, there is no problem in transmission of vertical load or horizontal load. In order to effectively transmit the load to the surface, it is desirable to perform the construction so as to ensure a gap enough to be filled with the curable fluid 15.

  On the outer periphery of the outer tube 9, a joint 7 that fits with the joint 11 of the sheet pile 13 is provided. The type of the joint 7 is not particularly limited, and may be the same as the joint 11 of the sheet pile 13 as shown in FIG. 5, or a pipe joint as shown in FIG. 6 to make a strong joint by mortar injection. May be.

As described above, by installing the outer tube 9 on the pile head 5a, the workability when constructing the sheet pile 13 is improved, and as a result, the workability of the pile 5 is improved. However, the effect of installing the outer tube 9 on the pile head 5a is not limited to this, and the following effects are achieved.
Since the outer tube 9 has a higher bending strength than the pile 5, it has sufficient strength against the horizontal force in the event of an earthquake, and the pile 5 only needs to accept the axial force. The pile diameter can be made smaller.
Moreover, if a high bearing capacity pile (a pile having a large tip support force), which has been actively developed in recent years, is applied, a rational design is possible with the head expansion structure and the tip bottom structure of the outer tube 9.

<Sheet pile>
The sheet pile 13 has a joint 11 fitted on the joint 7 of the outer tube 9 on both sides. Then, by fitting the joint 11 of the sheet pile 13 to the joint 7 of the adjacent outer pipe 9, the outer pipes are connected to each other by the sheet pile 13, and as shown in FIG. 2 and FIG. It is constructed to become.
The length of the sheet pile 13 in the vertical direction may be the same as that of the outer pipe 9, or the sheet pile 13 may be driven longer or shorter than the outer pipe 9 depending on the ground conditions. If the sheet pile 13 is driven long, more circumferential friction force and tip support force of the sheet pile 13 can be expected, so that the pile diameter and plate thickness can be reduced.

In order to connect and integrate the outer tube 9 and the sheet pile 13 with the footing, it is desirable to attach a stud or a gibber to the outer tube 9 or the sheet pile 13. The shape of the stud or gibber is not particularly limited, and any shape may be used.
The outer tube 9 and the pile 5 may be provided not only on the sheet pile 13 but also on the inner surface of the footing according to the load scale. At this time, without using the outer pipe 9, the pile 5 may be connected to the footing, or an outer pipe or a pile having a short length may be used. It is not necessary to provide the joint 7 on the pile or outer pipe provided on the inner surface of the footing.

<Construction method 1>
Next, the construction method of the pier foundation structure 1 comprised as mentioned above is demonstrated based on FIG.
Pile 5 is laid by the pre-boring method. At that time, it is preferable to build up a rooted bulb 19 at the tip to increase the tip support force (see FIG. 7A).
Using the same machine, the ground of the pile head 5a is expanded and dug 21 for constructing the outer tube 9 (see FIG. 7B).
Next, the outer tube 9 is driven on the pile head 5a (see FIG. 7C). At this time, since there is a gap between the pile head 5a and the outer tube 9, there is no problem even if the construction position of the pile 5 is slightly deviated from the planned position. On the other hand, since the outer tube 9 is connected to the sheet pile 13, it is necessary to drive it at an accurate position. However, since the outer tube 9 is short, it is easy to drive it at a predetermined position.

Next, the sheet pile 13 is sequentially driven so that the joint 11 of the sheet pile 13 is fitted to the joint 7 of the outer pipe 9, and all the outer pipes are connected by the sheet pile 13 (see FIG. 7D). The gap between the pile 5 and the outer tube 9 is filled with a curable fluid 15 such as mortar.
The part where the footing surrounded by the sheet pile 13 is constructed is excavated, and the footing and the pier 3 are constructed. Finally, backfilling is completed (see FIG. 7E).

<Construction method 2>
In the construction method 1, an example in which the pile 5 is driven first and then the sheet pile 13 is driven is shown. However, in the present invention, since the sheet pile 13 can be driven first, the construction method in that case is shown in FIG. 8 and described below.

The outer pipe 9 is driven, the sheet pile 13 is sequentially driven so that the joint 11 of the sheet pile 13 is fitted to the joint 7 of the outer pipe 9, and all the outer pipes are connected by the sheet pile 13 (FIG. 8 ( a)).
Next, the pile 5 is driven so as to penetrate the outer tube 9 (FIG. 8B). The pile 5 may be driven to the extent that the pile head 5a overlaps the lower portion of the outer tube 9, or may be driven to the extent that the pile head 5a protrudes above the outer tube 9. The gap between the pile 5 and the outer tube 9 is filled with a curable fluid 15 such as concrete, mortar, or soil cement, so that the pile head 5a and the outer tube 9 are integrated.
Finally, the footing and the pier 3 are built (see FIG. 8C).

  In the description of the construction method 2 described above, the example in which the footing and the pier 3 are constructed after the pile 5 is placed has been shown. However, after the footing and the pier 3 are constructed, the piles are constructed after the steps are reversed. 5 may be cast.

  In the present embodiment, the outer pipe 9 is installed on the pile head 5a, and the adjacent outer pipes are connected to each other by the sheet pile 13, so which is the order of the construction of the pile 5 and the construction of the sheet pile 13? It can also be done first. When constructing the sheet pile 13 first, as described in the construction method 2 above, the outer tube 9 is first placed. However, since the outer tube 9 is short in length, it is necessary to construct it accurately. It is easy and can easily connect the sheet pile 13 to the outer tube 9. On the other hand, even if the pile 5 is constructed first, even if the construction accuracy of the pile 5 is poor and the pile core is slightly displaced, there is a gap between the outer tube 9 and the pile head 5a. The construction error can be absorbed, the sheet pile 13 and the outer tube 9 can be easily connected, and labor required for mutual connection can be saved. In other words, it is not necessary to make the construction accuracy of the pile 5 more strict than necessary just because it is connected by the sheet pile 13, and therefore, the pile 5 is compared with that described in Patent Document 3. This improves the work efficiency of the construction and shortens the construction period.

Moreover, in this Embodiment, the outer pipe 9 is installed in the pile head 5a, the adjacent outer pipes are connected to each other by the sheet pile 13, and the footing is constructed where the outer pipe 9 and the sheet pile 13 are surrounded. Therefore, the footing is smaller than that of the conventional one, and it is easy to secure the site, and the excavation amount and the material cost for placing concrete can be reduced.
When the pile specifications are determined by the horizontal force in design, there is a margin in the tip support force and the peripheral frictional force, and wasteful design occurs. In this respect, in this embodiment, the pile head has a double pipe structure, so that the design can be given freedom, and the material cost is reduced by rational design such as making the shaft portion of the pile 5 thinner. Can be made.
Moreover, since the outer pipe 9 and the pile 5 are separated, the construction position of the sheet pile 13 can be flexibly adjusted by the outer pipe 9 even when the pile 5 is shorter or longer than a predetermined insertion due to a high stoppage or insufficient supporting force. Easy to deal with troubles.

DESCRIPTION OF SYMBOLS 1 Bridge pier foundation structure 3 Bridge pier 5 Pile 5a Pile head 7 Joint 9 Outer pipe 11 Joint 13 Sheet pile 15 Hardening fluid 17 Protrusion 19 Rooted bulb 21 Expansion digging

Claims (6)

A foundation structure to be joined to the pier, a plurality of piles constructed at a predetermined interval, and an outer pipe installed on each pile so as to cover the pile head of the pile, having joints on the side surfaces A sheet pile having a joint for fitting with the joint of the outer pipe, fitting the joint of the sheet pile to the joint of the outer pipe, connecting the outer pipes with the sheet pile, and being surrounded by the sheet pile A pier foundation structure, which is constructed by placing concrete in the raised part and constructing a footing .   The pier foundation structure according to claim 1, wherein a difference between an outer diameter of the pile and an inner diameter of the outer pipe is 10 cm or more.   The pier foundation structure according to claim 1, wherein an inner diameter of the outer pipe is 1.2 to 2 times an outer diameter of the pile.   The pier foundation structure according to any one of claims 1 to 3, wherein a curable fluid is filled in a gap between the pile and the outer pipe. A construction method of the pier foundation structure according to claim 4,
  The step of placing a plurality of piles, the step of expanding the ground of the pile heads that have been placed, the step of installing an outer pipe on the pile head, and fitting the joint of the sheet pile to the joint of the outer pipe The sheet piles were sequentially placed in such a manner that all the outer tubes were connected with each other by a sheet pile, the step of filling the gap between the pile and the outer tube with a curable fluid, and the sheet piles surrounded. A construction method of a pier foundation structure comprising a step of excavating a portion where a footing is constructed to build a footing and a pier. A construction method of the pier foundation structure according to claim 4,
  A step of placing an outer pipe, a step of sequentially placing the sheet piles so that a joint of a sheet pile is fitted to a joint of the outer pipe, and connecting all the outer pipes with a sheet pile, and the outer pipe The step of driving the pile so as to penetrate, the step of filling the gap between the pile and the outer tube with a curable fluid, and excavating the part where the footing surrounded by the sheet pile is constructed to make the footing and the pier The construction method of the pier foundation structure characterized by including the process of building.

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