JP2008196255A - Pile foundation reinforcing structure and pile foundation reinforcing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mainly enhance the earthquake resistance of an existing pile foundation without increasing piles or improving soil. <P>SOLUTION: A foundation 2 supported on piles 1, sheet piles 3 continuously inserted underground in at least a partial section in the circumferential direction of the foundation 2, and a structure 5 constructed in a foundation 2 side region of a sheet pile bulkhead 4 formed of the continuous sheet piles 3 on the foundation 2, are added to the existing pile foundation. The sheet pile bulkhead 4 and the structure body 5 are joined so that both can act integrally. The structure 5 is integrated with the foundation 2 according to circumstances. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reinforcing structure for a pile foundation and a reinforcing method for the pile foundation which are implemented mainly for the purpose of improving the earthquake resistance of an existing pile foundation.

  The pile foundation supported by the pile is basically designed on the condition that the pile shares the vertical bearing capacity and the foundation excluding the pile shares the horizontal force. Often not. For this reason, a pile cannot resist the bending moment by the horizontal force which acts on a foundation at the time of a big earthquake, and it can happen that it leads to destruction. Destruction is likely to occur at the head where the bending moment is maximized.

  In addition to the method of adding piles (see Patent Document 1), there are methods for improving the ground below the bottom of the foundation (see Patent Document 2). Since the structure of the existing foundation will be radically changed, it must be a large-scale construction.

JP 2005-180079 (Claim 1, paragraphs 0019 to 0020, FIGS. 4 to 7) JP 2004-124493 A (Claim 1, paragraphs 0022 to 0024, FIGS. 1 to 3)

  In the method of adding piles as in Patent Document 1, since a new pile cannot be installed under the existing foundation, the foundation is extended after the pile is installed around the existing foundation. Therefore, the size of the foundation to be completed becomes very large. In this case, since the vertical load share ratio between the existing pile and the new pile is unknown, the design tends to be uneconomical considering the safety side.

  In the method of improving the ground below the bottom surface of the foundation as in Patent Document 2, the ground improvement material is injected into the ground by injection while loosening the original ground soil below the bottom surface of the foundation. Meanwhile, the support capacity of the foundation may be reduced. Therefore, it may be impossible to carry out the construction while the superstructure on the foundation is left in use.

  Moreover, in the existing foundation, since the stirring device cannot be inserted vertically into the ground below the bottom surface of the foundation, it is necessary to use a method of injecting high-pressure water. However, in the method using high-pressure water, it is difficult to improve only the ground in a specific area to be improved, and thus it is difficult to efficiently improve the target ground below the bottom of the foundation.

  Based on the above background, the present invention proposes a reinforcing structure for a pile foundation and a reinforcing method for the pile foundation that make it possible to enhance the earthquake resistance of an existing pile foundation without relying on the expansion of the pile and the ground improvement.

  The pile foundation reinforcing structure according to the first aspect of the present invention includes a foundation supported by the pile, a sheet pile continuously inserted into at least a part of the circumferential direction of the foundation, and the foundation A structure constructed in the region of the foundation side of the sheet pile wall composed of the continuous sheet piles, and the sheet pile wall and the structure are joined together so as to be able to behave integrally. To do.

  For example, when the plane of the foundation is rectangular, the sheet pile is inserted continuously on at least one side on the plane of the foundation, and continuously inserted on two opposite sides or two orthogonal sides. , Orbiting the entire foundation, sometimes completely surrounding the foundation. A sheet pile wall forms a sheet pile wall by continuing on this one side. Whether the sheet pile is inserted along which side, or whether the depth of the sheet pile wall tip at each side is aligned is determined by the ground conditions and the like.

  As a general rule, the sheet pile is inserted to a depth deeper than the bottom surface of the foundation, but as described below, the sheet pile wall as a whole is deeper than the bottom surface of the foundation so that it receives horizontal force from the ground at the surface of the sheet pile wall and protects the pile head. Therefore, it is not always necessary to insert all the sheet piles to the depth of the bottom surface of the foundation.

  The sheet pile forms a sheet pile wall continuously in the circumferential direction of the foundation, and acts to reduce the bending moment due to the horizontal force that the pile bears by resisting the horizontal force received from the ground during an earthquake. In addition, the sheet pile should be inserted so that these functions can be fully demonstrated because it works together with the structure built on the foundation side of the sheet pile to prevent the foundation from falling. A section around the foundation is determined.

  The present invention is mainly implemented for the purpose of seismically reinforcing an existing pile foundation, but is also implemented when a new pile foundation is constructed. For existing pile foundations, the pile foundation is seismically reinforced by adding a sheet pile wall continuous in the circumferential direction of the foundation and a structure constructed on the foundation on one side of the sheet pile wall. In the case of new construction, a sheet pile wall is formed around the pile foundation, and a pile foundation that is seismically reinforced is constructed by constructing a structure inside thereof, but the foundation and the structure are substantially integrated.

  When the sheet pile wall and the structure are joined together so that they can behave integrally, the resistance moment that prevents rotation from the structure to the foundation is generated against the moment that is generated during an earthquake and tries to rotate the foundation. Works. In addition, the sheet pile wall is inserted to a depth deeper than the bottom surface of the foundation as a whole, and a reaction force opposite to the direction of rotation acts on the ground below the foundation bottom surface from the inner peripheral surface (surface on the foundation side) of the sheet pile wall. Therefore, the rotation of the foundation is suppressed.

  When the foundation is about to rotate, friction force acting in the direction opposite to the direction of rotation acts on the inner and outer peripheral surfaces of the sheet pile wall to prevent rotation, so the foundation is rotated by the structure and the sheet pile wall due to the earthquake. Stable against.

  In principle, the supporting force for the vertical load received by the foundation is borne by the pile supporting the foundation, and the increase in the vertical load accompanying the addition of the structure is borne by the frictional force acting on both sides of the sheet pile wall. Since the sheet pile wall is formed so as to surround the structure, for example, so as to surround the structure, the structure of the sheet pile wall is not necessarily limited to the structure. There is no need to be united with the foundation.

  The sheet pile wall also receives resistance from the ground in the direction opposite to the direction of movement when the superstructure on the foundation tries to move in the horizontal direction due to the earthquake, thus stabilizing the foundation against horizontal movement due to the earthquake. It works to make it.

  In existing pile foundations, the newly added sheet pile wall and structure behave integrally with the load such as bending moment that acts on the foundation in the event of an earthquake. Therefore, it is not necessary to add new piles or improve the ground below the bottom of the foundation.

  When there is no sheet pile wall, the side of the foundation and the side of the pile resist the horizontal force that the foundation receives from the surrounding ground, so an excessive bending moment acts on the pile head. On the other hand, in claim 1, since the tip of the sheet pile wall is inserted to a depth larger than the depth of the foundation bottom surface, the outer peripheral surface of the sheet pile wall resists horizontal force from the ground, so that the horizontal force received by the side surface of the pile Is reduced. As a result, since the bending moment acting on the pile head is reduced, the pile head is protected and the pile can be kept healthy.

  Since the bending moment acting on the pile head is reduced with respect to the horizontal force received from the ground, it is not necessary to make the cross-section of the pile larger than necessary when newly constructing the pile foundation. It becomes possible to design with a simple cross section.

  In existing pile foundations, it is not necessary to improve the ground below the bottom of the foundation to protect (restrain) the pile head, so construction is simple and the upper structure on the foundation remains in use. It is possible to carry out the construction.

  In the case of existing pile foundations, the ground on the top surface of the foundation will be removed when constructing the structure, but it is sufficient to drill from the ground surface to the top surface of the foundation, and the ground below the bottom surface of the foundation may be loosened. As a result, a decrease in the support capacity of the foundation is avoided. When constructing the structure, if necessary, it is possible to reinforce the superstructure such as piers built on the foundation at the same time, and it can be performed in parallel with the construction of the existing foundation. The efficiency of construction can be improved.

  The invention according to claim 2 is characterized in that, in claim 1, the structure is integrated with the foundation. As described above, it is not always necessary to integrate the structure with the foundation, but when they are integrated, the structure becomes a part of the foundation, resulting in an increase in the horizontal section or height of the foundation. As a result, the stability against the moment of rotation of the foundation during an earthquake is improved. When a pile foundation is newly established, the structure is constructed in an integrated form with the foundation.

  The pile foundation reinforcement structure according to claim 1 or claim 2 is constructed mainly by the method according to claim 3. The method for reinforcing a pile foundation according to claim 3 includes a step of inserting a sheet pile into the ground continuously in at least a part of the circumferential direction of the foundation in the foundation supported by the pile; And a step of constructing a structure in the region of the foundation side of the sheet pile wall made of the continuous sheet piles, and a step of joining the sheet pile wall and the structure so that they can behave integrally. As a requirement.

  Although the method of Claim 3 is mainly implemented with respect to the existing pile foundation, it is implemented also when constructing a new pile foundation. However, in the new case, the foundation and the structure are substantially integrated.

  By integrating the sheet pile wall built around the pile foundation and the structure built on its inner periphery, the pile and foundation can be applied to vertical and horizontal loads in addition to bending moments acting on the pile and foundation. Can be integrated and resisted, so it is possible to seismically reinforce the pile foundation without adding piles or improving the ground.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 includes a foundation 2 supported by a pile 1, a sheet pile 3 inserted continuously into at least a part of the circumferential direction of the foundation 2, and a continuous sheet pile 3 on the foundation 2. An example of a reinforcing structure of a pile foundation including a structure 5 constructed in a region on the foundation 2 side of the sheet pile wall 4 and in which the sheet pile wall 4 and the structure 5 are joined so as to be able to behave integrally is shown. The drawing shows an example of seismic reinforcement of an existing pile foundation, but the pile foundation may be constructed as a new construction. 2- (a) and (b) show the plane and the elevation in FIG. 1, respectively.

  Adjacent sheet piles 3 and 3 are connected to each other by engagement or the like, or are linked to each other so as to form a sheet pile wall 4 by being continuously inserted into the ground in the circumferential direction of the foundation 2. Although the drawing shows the case where the sheet pile wall 4 circulates around the foundation 2, the sheet pile wall 4 is formed so as to be in contact with at least one side surface of the foundation 2. Although the steel sheet pile is mainly used for the sheet pile 3, other sheet piles are also used. In the drawing, a steel sheet pile having a grooved cross section having a web and a flange is used, and adjacent sheet piles 3 and 3 are overlapped and joined to each other in the flange.

  The tip (lower end) of the sheet pile 3 is inserted to a depth deeper than the depth of the bottom surface of the foundation 2 so as not to apply excessive stress to the head of the pile 1 with respect to the horizontal force from the ground. However, it is not necessary for all the sheet piles 3 to be inserted to a depth below the bottom surface of the foundation 2, and it is sufficient that the sheet pile wall 4 as a whole can exhibit a function of reducing stress on the head of the pile 1. When the structure 5 is made of concrete, the sheet pile 3 also serves as a formwork for placing the concrete. Therefore, the upper end of the sheet pile 3 is aligned with the top end face of the structure 5 constructed on the foundation 2 or more. Located at the height of

  When the pile foundation already exists and the discarded concrete exists below the bottom surface of the foundation 2, the sheet pile 3 is inserted around the discarded concrete. In that case, a clearance is formed between the inner peripheral surface of the sheet pile wall 4 and the peripheral surface of the foundation 3, but the peripheral surface of the discarded concrete comes into contact with the inner peripheral surface of the sheet pile wall 4 together with the structure 5. In order to maintain the space between the sheet pile wall 4 and the foundation 2, the presence of the clearance does not deform the sheet pile wall 4 when the structure 5 and the sheet pile wall 4 are integrated.

  The structure 5 is constructed on the upper surface of the foundation 2 and is integrally joined to the sheet pile wall 4. The structure 5 may or may not be integrated with the foundation 2 depending on whether or not it behaves integrally with the foundation 2. When the pile foundation is newly installed, the structure 5 is constructed integrally with the foundation 2. When the structure 5 is integrated with the existing foundation 2, for example, a post-construction anchor is driven into the foundation 2 and then the construction anchor is fixed to the structure 5, or the foundation 2 is turned over from the upper surface side. The reinforcing bars are exposed and the reinforcing bars are fixed to the structure 5.

  The structure type of the structure 5 is not limited, and any structure of reinforced concrete, steel frame, steel reinforced concrete, or a combination thereof is used. The reinforced concrete structure includes a structure in which a tension material 7 such as a PC steel material is disposed in unreinforced concrete.

  FIGS. 1 and 2 illustrate a case where the structure 5 is integrated with the sheet pile wall 4 by connecting the tension member 7 disposed in the structure 5 to the sheet pile wall 4 when the structure 5 is reinforced concrete. An example is shown.

  Since the pier and other upper structures 6 as shown in the figure are connected to the foundation 2, reinforcing bars, steel materials, or tension members 7 are arranged around the upper structure 6 in at least two directions. The reinforcing bars and the tension members 7 are arranged in one or more stages in the height direction according to the height of the structure 5. FIG. 1 shows a case where two stages are arranged. Steps are attached to the tendons 7, 7 that intersect at the same level.

  In the case of FIGS. 1 and 2, the concrete 5 a constituting the structural body 5 is struck in the region surrounded by the sheet pile wall 4, which is the region on the foundation 2 side of the sheet pile wall 4, after the reinforcing bars or the reinforcing bars and the tension members 7 are arranged. Established. The surface of the tendon 7 may adhere to the concrete 5a or may adhere to the concrete 5a. When the adhesion breaks, there is an advantage that prestress can be introduced from the sheet pile wall 4 toward the center side of the foundation 2 to the concrete 5a using the sheet pile wall 4 as a bearing plate. The end of the tendon 7 penetrates the sheet pile 3 and protrudes outside the sheet pile wall 4.

  After the concrete 5a is hardened, the structure 5 and the sheet pile wall 4 are integrated by applying a tension force from the end to the tension member 7 protruding to the outside of the sheet pile wall 4. Prestress is introduced into the concrete 5a depending on the degree of tension applied to the tension member 7, but when the structure 5 and the sheet pile wall 4 are integrated, the tension is such that prestress is not necessarily introduced into the concrete 5a. Need not be applied to the tendon 5.

  In the case of FIG. 1, the sheet pile wall 4 is also used as a fixing plate for fixing the tension material 7. However, if the end of the tension material 7 is fixed, the sheet pile wall 4 is fixed to the side surface of the structure 5. Since a board should just be arrange | positioned, it is not necessary to construct the sheet pile wall 4 over the full length of the side surface of the foundation 2. FIG. Therefore, the sheet pile wall 4 may be constructed on one side across the foundation 2, and the sheet pile wall 4 may not be constructed on the other side facing it.

  FIG. 3 shows that a reinforced concrete structure 5 is integrated with the sheet pile wall 4 using a reinforcing bar 8 in which the structure 5a is arranged in at least two directions and a perforated steel sheet 9 protruding from the inner peripheral surface of the sheet pile wall 4. An example in the case where 4 (a) and 4 (b) show the plane and elevation of FIG. 3, respectively.

  In this case as well, the reinforcing bars 8 are arranged around the upper structure 6. The perforated steel sheet 9 is a steel material having a hole or a slit through which a reinforcing bar 8 can be inserted in a portion perpendicular to the surface of the sheet pile wall 4 such as a plate, T-shaped steel, and the reinforcing bar 8 is inserted into and engaged with the hole. Thus, the tensile force from the reinforcing bar 8 is transmitted to the sheet pile 3. The compressive force from the structure 5 is transmitted from the concrete 5a to the sheet pile 3. The perforated steel sheet 9 is fixed to the surface of the sheet pile 3 on the base 2 side in advance or after insertion of the sheet pile 3 by welding, bolts or the like.

  FIG. 5 shows an example in which a steel-framed concrete structure or a steel-framed reinforced concrete structure 5 is integrated with the sheet pile wall 4 by using a core material 10 made of a steel material arranged in at least two directions in the concrete 5a. 6 (a) and 6 (b) show the plane and elevation of FIG. 5, respectively. In FIG. 5, a support material 11 that supports the core material 10 is installed on the upper surface of the foundation 2 at an end position of the core material 10 in order to arrange the core material 10 in the intermediate portion in the height direction of the foundation 2. .

  The core material 10 may constitute the structure 5 alone, and in that case, the structure 5 becomes a steel structure. When the reinforcing bar 8 is arranged in the concrete 5a together with the core material 10, the structure 5 becomes a steel-framed reinforced concrete structure.

  The core member 10 is also disposed around the upper structure 6, and the end portion contacts or approaches the inner peripheral surface of the sheet pile wall 4 for joining with the sheet pile wall 4. The end of the core member 10 is joined to the inner peripheral surface of the sheet pile wall 4 by welding or bolts. When bolted, a metal fitting such as an end plate is welded to the end of the core member 10 in advance. A plate or the like may be provided on the inner peripheral surface of the sheet pile 3 for bolting the core member 10.

  Also in the examples of FIGS. 3 and 5, the sheet pile wall 4 may be constructed on one side across the foundation 2, and the sheet pile wall 4 may not be constructed on the other side facing it.

It is the perspective view which showed the example at the time of integrating a sheet pile wall and a structure by tension | tensile_strength of a tension material. (A) is a top view of FIG. 1, (b) is an elevational view of FIG. It is the perspective view which showed the example at the time of integrating a sheet pile wall and a structure using a reinforcing bar and a perforated steel plate. (A) is a top view of FIG. 3, (b) is an elevational view of FIG. It is the perspective view which showed the example at the time of integrating a sheet pile wall and a structure with a core material. (A) is a top view of FIG. 5, (b) is an elevational view of FIG.

Explanation of symbols

1 ……… Pile 2 ……… Foundation 3 ……… Sheet 4 ……… Sheet Wall 5 ……… Structure 5a …… Concrete 6 ……… Superstructure 7 ……… Strength 8 ……… Rebar 9… ...... Perforated steel sheet 10 ... Core material 11 ... Support material

Claims (3)

  A foundation supported by a pile, a sheet pile continuously inserted into the ground in at least a part of the circumferential direction of the foundation, and the foundation side of the sheet pile wall made of the continuous sheet pile on the foundation. A pile foundation reinforcing structure comprising: a structure constructed in a region, wherein the sheet pile wall and the structure are joined together so as to be able to behave integrally.   The reinforcing structure for a pile foundation according to claim 1, wherein the structure is integrated with the foundation. In a foundation supported by a pile, a step of continuously inserting a sheet pile into the ground in at least a part of the circumferential direction of the foundation, and the foundation side of the sheet pile wall made of the continuous sheet pile on the foundation A method for reinforcing a pile foundation, comprising: a step of constructing a structure in the region of the step; and a step of joining the sheet pile wall and the structure together so that the structure can behave integrally.

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