JP6497659B2 - Foundation structure of new structure using existing pile and its construction method - Google Patents

Description

  The present invention relates to a foundation structure of a new structure using existing piles remaining in the ground and a construction method thereof.

  Conventionally, when a new building is constructed on the ground with existing piles, a structure as shown in FIG. 5 may be adopted. In this structure, a part of the soft layer G2 around the existing pile 1 driven to reach the supporting ground (good quality layer G1) is replaced with a columnar ground improvement body 2, and then a foundation for building (new construction) This is a new foundation 3). In such a structure, the settlement rigidity of the existing pile 1 is larger than that of the surrounding ground composed of the ground improvement body 2. For this reason, a large stress is generated in a part of the new foundation 3 due to the difference in the settlement rigidity, and the foundation may have to be reinforced.

  For example, a structure as shown in FIG. 6 (see Patent Document 1), a structure as shown in FIG. 7 (see Non-Patent Document 1), and the like have been proposed as existing structures for solving such problems. The structure shown in FIG. 6 is less rigid than the surrounding ground G after excavating the ground G around the upper end (existing pile head) of the existing pile 1 and excising the upper end of the existing pile 1. The material 4 is backfilled to relieve the stress concentration that the existing pile 1 gives to the new foundation 3. Further, the structure shown in FIG. 7 is the stress that the existing pile 1 gives to the new foundation 3 by sandwiching a low-rigidity material 5 such as Styrofoam (registered trademark) between the upper end of the existing pile 1 and the new foundation 3. It eases concentration. In addition, the codes | symbols 6a, 6b, and 6c in FIG. 7 represent the abandoned concrete, the shingle gravel, and mountain sand, respectively.

  However, because the settlement rigidity changes depending on the cutting conditions of the existing pile pile head and the construction conditions such as what kind of material is backfilled at what density, it is difficult to clearly define the settlement rigidity and it is difficult to consider in the design There was a problem. In addition, depending on the settlement rigidity ratio of the surrounding ground and existing piles, it is necessary to largely cut the pile head, and depending on the ground conditions, construction may be difficult.

  It is very difficult to apply the ground material in a controlled manner so as to have a specified soft rigidity, and the reliability is low. For this reason, in general, there are many cases in which the ground reaction force of the existing pile portion subjected to such a treatment is not expected. When the existing pile 1 is unevenly present under the new foundation 3 as in the example of FIG. 5, if the existing pile 1 is not used and only the new ground improvement body 2 is to be supported, the existing pile 1 and its pile Since the ground cannot be improved in the vicinity, the supporting force is insufficient. Therefore, as shown in FIG. 8, it is necessary to widen the ground improvement area by the ground improvement body 2 and the width of the new foundation 3 to compensate for the lack of support power and to support the building. In this case, since the amount of bar arrangement of the new foundation 3 increases as the width of the new foundation 3 increases, it becomes uneconomical.

JP 2010-133206 A

“Guide for using existing piles”, Japan Association of Building Industry, February 2003

  For this reason, when constructing a new structure such as a new foundation for a building on the ground where the existing piles remain, excessive stress is not concentrated on a part of the new foundation. There was a need for technology that did not require reinforcement.

  The present invention has been made in view of the above, and does not require excessive stress concentration on a part of the new structure, and does not require widening or reinforcement of the new structure. It aims at providing the basic structure of a structure, and its construction method.

  In order to solve the above problems and achieve the object, the foundation structure of the new structure using the existing pile according to the present invention is the foundation structure of the new structure constructed on the ground where the existing pile remains. The upper end of the existing pile is replaced and adjusted in order to change and adjust the settlement rigidity with respect to the settlement of the existing pile, and the new structure has a horizontal sectional area different from the horizontal sectional area of the existing pile. A pile head that can transmit a load from an object to the existing pile is provided.

  Moreover, the foundation structure of the new structure using another existing pile according to the present invention is the above-described invention, wherein the horizontal cross-sectional area of the pile head replaces the upper end portion of the existing pile with the pile head. Therefore, the settlement rigidity of the existing pile is set so as to match the settlement rigidity of the surrounding ground.

  Moreover, the foundation structure of the new structure using the other existing pile which concerns on this invention is further provided with the new pile or the ground improvement body in the ground around the said existing pile in the above-mentioned invention.

  Moreover, the foundation structure of the new structure using the other existing pile which concerns on this invention is the diameter (d) of the said existing pile, and the said pile head as for the said pile head in the invention mentioned above. It is characterized by comprising a disk having a length (D + 2h) or more obtained by adding twice the height (h) of the part.

  Moreover, the construction method of the foundation structure of the new structure using the existing pile according to the present invention is a method of constructing the foundation structure of the new structure using the existing pile described above, After excavating the surrounding ground and excising the upper end of the existing pile, the excised part can be replaced with the pile head, and the new structure can be constructed on the pile head and the surrounding ground It is characterized by that.

  According to the foundation structure of the new structure using the existing pile according to the present invention, the foundation structure of the new structure constructed on the ground where the existing pile remains, the subsidence rigidity with respect to the settlement of the existing pile In order to change and adjust, the upper end of the existing pile is replaced and has a horizontal cross-sectional area different from the horizontal cross-sectional area of the existing pile, and the load from the new structure can be transmitted to the existing pile. Since the pile head is provided, the existing pile can be handled in the same manner as the surrounding ground if the horizontal sectional area of the pile head is adjusted to match the settlement rigidity of the existing pile with that of the surrounding ground. Thereby, there is an effect that excessive stress is concentrated on a part of the new structure constructed on the ground, and it is not necessary to widen or reinforce the new structure.

  Moreover, according to the foundation structure of the new structure using the other existing pile which concerns on this invention, the horizontal cross-sectional area of the said pile head is the said by replacing the upper end part of the said existing pile with the said pile head. Since the settling rigidity of existing piles matches the settling rigidity of the surrounding ground, it is possible to handle existing piles in the same way as the surrounding ground, and a new structure built on the ground There is an effect that excessive stress is concentrated on a part of the object and it is not necessary to widen or reinforce the new structure.

  In addition, according to the foundation structure of a new structure using another existing pile according to the present invention, the ground around the existing pile is further provided with a new pile or a ground improvement body. The subsidence rigidity can be adjusted, and the degree of freedom in designing the new structure and the foundation structure can be increased.

  Moreover, according to the foundation structure of the new structure using the other existing pile which concerns on this invention, the said pile head has the diameter (d) of the said existing pile and the height of the said pile head. Since it consists of a disc with a length (D + 2h) or more that is twice the length (h), the top of the existing pile is excised, and when the pile head is provided in the excised part, the necessary pile head What is necessary is just to excise the upper end part of the existing pile only by the height h which can ensure horizontal cross-sectional area of this, and there exists an effect that the excised depth for every existing pile can be clarified.

  Moreover, according to the construction method of the foundation structure of the new structure using the existing pile according to the present invention, it is a method of constructing the foundation structure of the new structure using the existing pile, and the upper end of the existing pile After excavating the ground around the part and excising the upper end of the existing pile, the excised part is replaced with the pile head, and the new structure is constructed on the pile head and the surrounding ground Since it was made possible, if the horizontal cross-sectional area of the pile head is adjusted to match the settlement rigidity of the existing pile with that of the surrounding ground, the existing pile can be handled in the same way as the surrounding ground. Thereby, there is an effect that excessive stress is concentrated on a part of the new structure constructed on the ground, and it is not necessary to widen or reinforce the new structure.

FIG. 1 is a side cross-sectional view showing a first embodiment of a foundation structure of a new structure using the existing pile according to the present invention and a construction method thereof. FIG. 2 is a diagram showing a second embodiment of the foundation structure of a new structure using the existing pile according to the present invention and the construction method thereof, (1) is a plane sectional view, and (2) is a side sectional view. is there. FIG. 3 is a view showing Embodiment 3 of a foundation structure of a new structure using the existing pile according to the present invention and a construction method thereof, (1) is a plan sectional view, and (2) is a side sectional view. is there. FIG. 4: is a sectional side view which shows Embodiment 4 of the foundation structure of the new structure using the existing pile which concerns on this invention, and its construction method. 5A and 5B are schematic views of structural damage caused by conventional liquefaction. FIG. 5A is a plan sectional view, and FIG. 5B is a side sectional view. FIG. 6 is a side sectional view showing an example of a conventional reinforcing method. FIG. 7 is a side sectional view showing an example of a conventional reinforcing method. FIG. 8 is a side sectional view showing an example of a conventional reinforcing method, and is a view when the existing pile pile head is backfilled with a soft material and a new foundation is widened.

  Below, an embodiment of the foundation structure of the new structure using the existing pile concerning the present invention, and its construction method is described in detail based on a drawing. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
First, the first embodiment of the present invention will be described.
As shown in FIG. 1, the foundation structure 100 of a new structure using the existing pile according to the first embodiment is a new foundation 12 for building (new installation) constructed on the ground G where the existing pile 10 remains. It is a foundation structure that supports a structure), and includes a pile head 16 that replaces the upper end portion 14 of the existing pile 10. In the example of FIG. 1, a layout is shown in which a new foundation 12 is installed on the ground G where an existing pile 10 having a single circular cross section remains so that the center of the plane coincides with the axis of the existing pile 10. .

  The pile head 16 is a disk having a diameter d and a height h that is coaxial with the axis of the existing pile 10 and larger than the diameter D of the existing pile 10, and can transmit the load from the new foundation 12 to the existing pile 10 below. It is. As a constituent material of the pile head 16, for example, a material having sufficient rigidity and strength with respect to the design load of the new foundation 12 such as concrete or soil mortar can be used. Since the horizontal cross-sectional area of the pile head 16 is larger than that of the existing pile 10, by providing the pile head 16, the upper end portion 14 of the existing pile 10 is replaced with the pile head 16. The apparent settlement rigidity can be changed and adjusted small.

Next, an example of the construction method of the pile head 16 will be described.
First, the ground G around the upper end portion 14 of the existing pile 10 is dug, and the exposed upper end portion 14 of the existing pile 10 is cut by a predetermined depth h. And it is enough for the design load of the new foundation 12 such as concrete and soil mortar so that the cut part becomes a disk with a length D + 2h that is the diameter D of the existing pile 10 and twice the cut depth h. Backfilled with a material with sufficient rigidity and strength. By doing so, the upper end portion 14 of the existing pile 10 can be replaced with a disk-shaped pile head portion 16. Thereafter, the new foundation 12 may be installed on the pile head 16 and the surrounding ground G. The cutting depth h corresponds to the depth from the bottom of the new foundation 12 or the height of the pile head 16. Moreover, you may set the diameter d of the pile head 16 so that it may become D + 2h or more.

  Since the existing pile 10 bears a structural load acting in a circle having a diameter d (= D + 2h) of the pile head 16, the apparent settlement rigidity is reduced. The cutting depth h is calculated in advance from the settlement stiffness of the existing pile 10 and the surrounding ground G (if there is a new ground improvement body or pile in the ground G, the settlement stiffness). It is desirable to determine to be approximately equal.

  For example, in the foundation structure having the existing pile 1 and the newly installed ground improvement body 2 as shown in FIG. 5, the settlement rigidity of the existing pile 1 is twice the settlement rigidity of the newly installed ground improvement body 2. 1, the depth h corresponding to about 20.7% of the diameter D of the existing pile 10 is cut so that the horizontal cross-sectional area of the pile head 16 is twice that of the existing pile 10 as shown in FIG. Then, a disk-like pile head 16 can be constructed by placing a material such as concrete or soil mortar in the excised portion so as to be twice or more the horizontal cross-sectional area of the existing pile 10.

  When the excised part is replaced with a pile head 16 having a horizontal cross-sectional area twice that of the existing pile 10, it is horizontal in a side view connecting the outer edge of the upper end surface of the existing pile 10 and the outer edge of the upper end surface of the pile head 16. In contrast, it is considered that the ground pressure in the range surrounded by the 45 ° diagonal line acts on the existing pile 10, so the existing ground 10 has twice the average ground pressure of the new foundation 12, and the same ground pressure Since the subsidence amount is doubled, the subsidence rigidity of the existing pile 10, that is, the subsidence rigidity of the existing pile 1 in FIG. 5 is substantially equal to that of the ground improvement body 2 newly installed around the existing pile 1.

  Thus, according to this Embodiment, the horizontal cross-sectional area of the pile head 16 is adjusted by expanding the diameter (head expansion) of the upper end part 14 of the existing pile 10 by the pile head 16, and subsidence of the existing pile 10 is carried out. By combining the rigidity with that of the surrounding ground G, the existing pile 10 can be handled in the same manner as the surrounding ground G. Thereby, it is not necessary to concentrate excessive stress on a part of the new foundation 12 constructed on the ground G, or to widen or reinforce the new foundation 12.

  Moreover, the pile head 16 is made of a disk having a diameter d equal to or greater than the diameter D of the existing pile 10 and twice the height h of the pile head 16 (D + 2h). When the upper end portion 14 is excised and the pile head 16 is provided in the excised portion, the upper end portion 14 of the existing pile 10 may be excised by a height h that can ensure the horizontal cross-sectional area of the required pile head 16. Therefore, the cutting depth for each existing pile 10 can be clarified. Moreover, if the difference of the settlement rigidity of the existing pile 10 and the surrounding ground G is not very large, the cutting depth h can be suppressed small.

  Further, since materials such as concrete or soil mortar having high rigidity can be used for backfilling when the pile head 16 is constructed, management in construction and the like is facilitated.

  As described above, according to this embodiment, the processing when the existing pile 10 remains on the ground G is clear, and the influence on the new foundation 12 constructed on the ground G is minimized. Is possible.

(Embodiment 2)
Next, a second embodiment of the present invention will be described.
In the second embodiment, the present invention is applied when existing piles are close to some newly-provided ground improvement bodies.

  As shown in FIG. 2, the foundation structure 200 of the new structure using the existing pile according to the second embodiment is an aspect in which the existing pile 10 is close to some of the newly installed ground improvement bodies 18. In such a case, since the installation space for the pile head 16 provided in the upper end part 14 of the existing pile 10 becomes small, a horizontal cross-sectional area required when the pile head 16 is designed with a complete disk cannot be secured. There is a fear. Therefore, the pile head 16 is not a complete disk, for example, the outer edge 16a (the outer edge on the right side in the figure) on the side close to the newly installed ground improvement body 18 is connected to the new ground improvement body 18 so that a part of the disk is The chip has a chipped shape and a necessary horizontal sectional area A is secured. In this case, it is preferable to determine the height h of the pile head 16 so that the horizontal sectional area A can be secured.

  Even if it does in this way, there can exist an effect similar to said Embodiment 1. FIG. That is, by adjusting the horizontal cross-sectional area of the pile head 16 and matching the settlement rigidity of the existing pile 10 with that of the new ground improvement body 18 in the vicinity, the existing pile 10 is handled in the same manner as the new ground improvement body 18. It becomes possible. Thereby, it is not necessary to concentrate excessive stress on a part of the new foundation 12 constructed on the ground G, or to widen or reinforce the new foundation 12.

(Embodiment 3)
Next, a third embodiment of the present invention will be described.
The third embodiment corresponds to the application of the present invention to the conventional structure described with reference to FIG.

  As shown in FIG. 3, the foundation structure 300 of the new structure using the existing pile according to the third embodiment has the upper end portion 14 of the existing pile 10 driven so as to reach the supporting ground (good quality layer G1). While replacing with the pile head 16 of the present invention, a part of the soft layer G2 around the existing pile 10 is replaced with a columnar new ground improvement body 20, and the new foundation 12 is constructed thereon.

  Also according to the present embodiment, the same effects as those of the first embodiment can be obtained. That is, by adjusting the horizontal sectional area of the pile head 16 and matching the settlement rigidity of the existing pile 10 with that of the surrounding new ground improvement body 20, the existing pile 10 is handled in the same manner as the new ground improvement body 20. It becomes possible. Thereby, it is not necessary to concentrate excessive stress on a part of the new foundation 12 constructed on the ground G, or to widen or reinforce the new foundation 12.

  In addition, according to the present embodiment, since the ground improvement body 20 newly provided on the ground G around the existing pile 10 is provided, the settlement rigidity of the ground G around the existing pile 10 can be adjusted, and the new foundation 12 and the foundation can be adjusted. The degree of freedom in designing the structure 300 can be increased.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described.
In the fourth embodiment, the present invention is applied when the settlement rigidity of an existing pile is smaller than the settlement rigidity of a newly installed pile.

  As shown in FIG. 4, the foundation structure 400 of the new structure using the existing pile according to the fourth embodiment is such that the settlement rigidity of the existing pile 10 is the settlement rigidity of the new pile 22 provided in the surrounding ground G. Is smaller than the diameter D of the existing pile 10, the diameter d of the pile head 16 provided on the upper end portion 14 of the existing pile 10 is set. In this case, the cutting depth h of the upper end portion 14 of the existing pile 10 can be set to an arbitrary size. By adjusting the horizontal cross-sectional area of the pile head 16 so that the diameter d of the pile head 16 is smaller than the diameter D of the existing pile 10, the settlement rigidity of the apparent existing pile 10 can be increased. It is possible to match the settlement rigidity of 10 with that of the new pile 22.

  In this manner, the horizontal cross-sectional area of the pile head 16 is adjusted by reducing the diameter of the upper end portion 14 of the existing pile 10 by the pile head 16 (head reduction), and the settlement rigidity of the existing pile 10 is set to a new pile around the periphery. By combining it with 22, the existing pile 10 can be handled in the same way as the newly installed pile 22. Thereby, it is not necessary to concentrate excessive stress on a part of the new foundation 12 constructed on the ground G, or to widen or reinforce the new foundation 12.

  Moreover, according to this Embodiment, since the new pile 22 is provided in the ground G around the existing pile 10, the settlement rigidity of the ground G around the existing pile 10 can be adjusted, and the new foundation 12 and the foundation structure 400 can be adjusted. The degree of design freedom can be increased.

  As described above, according to the foundation structure of the new structure using the existing pile according to the present invention, the foundation structure of the new structure constructed on the ground where the existing pile remains, In order to change and adjust the settlement rigidity of the existing pile, the upper end of the existing pile is replaced, and has a horizontal sectional area different from the horizontal sectional area of the existing pile, and the load from the new structure is Since the pile head that can be transmitted to the existing pile is provided, if the cross-sectional area of the pile head is adjusted to match the settlement rigidity of the existing pile with that of the surrounding ground, the existing pile can be handled in the same way as the surrounding ground. It becomes possible. Thereby, it is not necessary to concentrate excessive stress on a part of the new structure constructed on the ground, and to widen or reinforce the new structure.

  Moreover, according to the foundation structure of the new structure using the other existing pile which concerns on this invention, the horizontal cross-sectional area of the said pile head is the said by replacing the upper end part of the said existing pile with the said pile head. Since the settling rigidity of existing piles matches the settling rigidity of the surrounding ground, it is possible to handle existing piles in the same way as the surrounding ground, and a new structure built on the ground It is not necessary to concentrate excessive stress on a part of the object or to widen or reinforce the new structure.

  In addition, according to the foundation structure of a new structure using another existing pile according to the present invention, the ground around the existing pile is further provided with a new pile or a ground improvement body. The settlement rigidity can be adjusted, and the degree of freedom in designing the new structure and foundation structure can be increased.

  Moreover, according to the foundation structure of the new structure using the other existing pile which concerns on this invention, the said pile head has the diameter (d) of the said existing pile and the height of the said pile head. Since it consists of a disc with a length (D + 2h) or more that is twice the length (h), the top of the existing pile is excised, and when the pile head is provided in the excised part, the necessary pile head What is necessary is just to excise the upper end part of the existing pile only by the height h which can ensure horizontal cross-sectional area of this, and the excision depth for every existing pile can be clarified.

  Moreover, according to the construction method of the foundation structure of the new structure using the existing pile according to the present invention, it is a method of constructing the foundation structure of the new structure using the existing pile, and the upper end of the existing pile After excavating the ground around the part and excising the upper end of the existing pile, the excised part is replaced with the pile head, and the new structure is constructed on the pile head and the surrounding ground Since it was made possible, if the horizontal cross-sectional area of the pile head is adjusted to match the settlement rigidity of the existing pile with that of the surrounding ground, the existing pile can be handled in the same way as the surrounding ground. Thereby, it is not necessary to concentrate excessive stress on a part of the new structure constructed on the ground, and to widen or reinforce the new structure.

  As described above, the foundation structure of a new structure using the existing pile according to the present invention and the construction method thereof are used for constructing a new structure such as a new foundation for a building on the ground where the existing pile remains. In particular, it is suitable for preventing excessive stress from concentrating on a part of the new structure and not requiring widening or reinforcement of the new structure.

10 Existing piles 12 New foundation (new structure)
14 Upper end 16 Pile head 16a Outer edge 18, 20 New ground improvement body 22 New pile 100, 200, 300, 400 Foundation structure of new structure using existing pile G Ground G1 Good quality layer G2 Soft layer D Existing pile Diameter h Cutting depth (pile head height)
d Pile head diameter A Horizontal cross-sectional area

Claims (5)

The basic structure of the new structure built on the ground where the existing piles remain,
In order to change and adjust the subsidence rigidity of the existing pile, the upper end of the existing pile is replaced, and has a horizontal cross-sectional area different from the horizontal cross-sectional area of the existing pile. A foundation structure of a new structure using an existing pile, comprising a pile head capable of transmitting a load to the existing pile.   The horizontal cross-sectional area of the pile head is set so that the settlement rigidity of the existing pile resulting from replacing the upper end of the existing pile with the pile head matches the settlement rigidity of the surrounding ground. The foundation structure of the new structure using the existing pile of Claim 1 characterized by the above-mentioned.   The foundation structure of the new structure using the existing pile according to claim 1 or 2, further comprising a new pile or a ground improvement body on the ground around the existing pile.   The pile head is composed of a disk having a diameter (d) of a length (D + 2h) or more obtained by adding the diameter (D) of the existing pile and twice the height (h) of the pile head. The foundation structure of the new structure using the existing pile as described in any one of Claims 1-3 characterized by the above-mentioned. A method for constructing a foundation structure of a new structure using the existing pile according to any one of claims 1 to 4,
After excavating the ground around the upper end of the existing pile and excising the upper end of the existing pile, the excised part is replaced with the pile head, and the pile head and the surrounding ground are A method for constructing the foundation structure of a new structure using existing piles, which is characterized in that a new structure can be constructed.