JPH11247203A - Reinforcing method of existing building foundation by inclined shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reinforcing method of an existing building foundation in future by using an inclined shaft firmly resistant to horizontal force such as earthquake force. SOLUTION: An inclined shaft 1 is arranged in the ground near the foundation of an existing building and the pile head of the inclined shaft 1 and the foundation of the existing building are connected together so that load is transmissible. In this case, inclined shaft construction work is attended with such process as excavating the ground with a casing pipe 11 provided with a digging pit 12 on its end periphery by intruding it into the ground by inclining it by the angle of the inclined shaft 1 with respect to the vertical line, sliming the interior of the excavation hole after excavation, erecting a ready-made pile in the interior of the casing pipe 11, filling the interior of the casing pipe 11 with a filler 15, pulling up the casing pipe 11 to the top of the anchoring portion and pressurizing the filler 15 on the anchoring portion, pulling up the casing pipe 11 to the ground and removing it, and curing the filler 15 until its specific strength is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a method for reinforcing an existing building foundation with a so-called slanted pile in which a pile is inclined with respect to a vertical line. The present invention relates to a method of subsequently reinforcing a foundation of an existing building by using a slanted pile which exerts an axial resistance and strongly resists a horizontal force such as an earthquake force.

[0002]

2. Description of the Related Art In the case of a pile foundation building, it is necessary for a pile to bear both a vertical load (building weight) and a horizontal load (seismic force). The pile foundations of buildings built after the mid-1980s were designed structurally taking into account both loads, but the pile foundations of buildings constructed before then were not designed for horizontal loads. General, low seismic performance.

[0003] A loose sandy ground with a shallow groundwater level may cause liquefaction. When liquefaction occurs,
Since the resistance of the ground to the pile is extremely small, the resistance to the load in the horizontal direction is sharply reduced. Regarding this liquefaction phenomenon, the stability is generally not examined until the 1990s. Therefore,
Existing buildings before the age mentioned above are strongly required to reinforce their foundations from the viewpoint of seismic performance against seismic force and stability against liquefaction.

On the other hand, the present applicant has devised an inclined pile construction method in which a pile is inclined with respect to a vertical line and strongly resists horizontal force such as seismic force, and is disclosed in JP-A-7-90830 and JP-A-7-90.
JP-A-860 and JP-A-8-170346 each disclose a slanted pile artificial ground. In particular,
In this publication, the technical idea of a group pile capable of fully exerting the effect of the inclined pile is disclosed. As shown in FIG. 6, the set pile has an axial resistance (R) of each inclined pile a, a = F
Horizontal resistance (F) determined by the formula 2R sin θ
It is an application of what can be expected. Since the two slant piles a, a constituting the set pile are arranged symmetrically in plan view, the vertical forces of the pair of slant piles a, a are offset in opposite directions, and structurally. Form a stable frame. Also,
The stress generated in each of the slant piles a is mainly a tensile stress or a compressive stress, and has an advantage that a bending moment (approximately M ≒ 0) and a shear stress are small due to the structural characteristics of the pile group.

Conventionally, a slanted pile is constructed by using a leader (pile driving device) of a construction machine used in a method of constructing a straight pile such as a driving pile method, an embedded pile method, a cast-in-place concrete pile method, etc. It was constructed by inclining by the angle (θ).

[0006]

[Problems to be solved by the present invention] The piles composed of slanted piles are constructed under and around the foundation of an existing building to share the horizontal force due to the earthquake, thereby improving the seismic performance of the existing building foundation. The method of making this can be easily analogized. However, if the slanted pile by the conventional method is applied to the existing building foundation as it is, there are the following problems.

As can be seen from the above equation of F = 2R sin θ, in order to obtain a large horizontal resistance (F), an inclined pile having a large inclination angle (θ) and a large axial resistance (R) is required. However, in the conventional method of constructing a slanted pile by simply inclining a leader of a construction machine with respect to a vertical line, it is difficult to construct a slanted pile according to the above-mentioned requirements for the following reasons. I) In the method of installing ready-made piles, such as the driving pile method and the embedded pile method, the inclination of the leader decreases the stability of the construction machine itself. There was a risk that the construction machine would fall. II) In the cast-in-place concrete pile method, in addition to the above I), the hole wall after excavation is inclined, so that the hole wall is likely to collapse. In addition, misalignment (center misalignment) was apt to occur when the reinforcing bar was built. It was also difficult to cast concrete using tremy tubes. Therefore, poor quality slant piles were easily constructed, and construction of slant piles with large axial resistance could not be expected at all.

Accordingly, an object of the present invention is to provide the above-mentioned I),
In order to eliminate all II), the ground was excavated by inclining the casing pipe, and after the excavation was completed, slime treatment was performed inside the borehole, and then a ready-made pile was built inside the casing pipe,
Another object of the present invention is to provide a method of reinforcing an existing building foundation with a slanted pile having a large circumferential frictional resistance and exhibiting a high proof axial resistance by injecting and filling an injection material. Also,
An object of the present invention is to provide a method of reinforcing an existing building foundation with a slanted pile having a large inclination angle with respect to a vertical line while maintaining the stability of a construction machine by adding a casing pipe or a ready-made pile in an extended manner.

[0009]

As a means for solving the above-mentioned problems of the prior art, a method of reinforcing an existing building foundation with a slanted pile according to the first aspect of the present invention is to provide a method for reinforcing an existing building in the ground near the foundation of the existing building. Placing a pile, connecting the pile head of the slant pile and the foundation of the existing building so that the load can be transmitted, the slant pile is constructed by the following process, and a drill bit is provided at the tip edge. Provided casing pipe, in the ground, excavating the ground by inclining by the angle of the inclined pile with respect to the vertical line, excavating the ground, after the end of the excavation, slime processing in the borehole, inside the casing pipe Building a ready-made stake, filling the inside of the casing pipe with an injection material, pulling up the casing pipe to the upper end of the anchoring portion, and pressing the injection material at the identification attachment portion, And removed by pulling upward, the grout is respectively characterized step, of curing until expressing a predetermined strength.

According to a second aspect of the present invention, there is provided a method for reinforcing an existing building foundation with a slanted pile, wherein the slanted pile is arranged in the ground near the foundation of the existing building, and a pile head of the slanted pile and the existing building are mounted. The slanted pile is connected to the foundation so that the load can be transmitted, and the slanted pile is constructed by the following process. Excavating the ground by inclining by inclining only at the angle of
A step of filling an injection material into the inside of the casing pipe,
Building a ready-made pile inside the casing pipe,
Pulling up the casing pipe to the upper end of the fixing portion, pressing the injection material in the identification attachment portion, pulling out the casing pipe to the ground and removing, curing the injection material until the injected material develops a predetermined strength, Each feature.

According to a third aspect of the present invention, there is provided a method for reinforcing an existing building foundation with a slanted pile, wherein the two slanted piles according to the first or second aspect are turned by approximately 180 degrees in plane one by one. It is characterized by being constructed in a symmetrical arrangement in order, and connecting pile heads of the same slant pile to form a group pile. According to a fourth aspect of the present invention, there is provided a method of reinforcing an existing building foundation with a slanted pile, wherein fresh water is injected into the ground by the casing pipe according to the first or second aspect.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A method for reinforcing an existing building foundation with slanted piles according to the present invention is generally performed on a pile foundation 3 of an existing building 2 including a pile 4 as shown in FIGS. home,
The footing 3a on the outer peripheral portion of the existing building 2 is suitably implemented. However, the implementation location is not limited to the footing 3a on the outer peripheral portion, but the foundation beam 3b on the outer peripheral portion of the existing building 2.
Can also be suitably carried out similarly. As shown in FIG. 2, the piles A and B composed of two inclined piles have a direction in which the resistance in the vertical plane where the piles are inclined is very large. Are arranged in two orthogonal directions of X and Y.

Next, the construction steps for implementing the reinforcing method of the present invention will be described. The ground 5 near the outer surface of each footing 3a located on the outer peripheral portion of the existing building 2 is excavated, and the two inclined piles 1 and 1 are arranged in the ground in a symmetric arrangement in which the orientation is changed by approximately 180 degrees in a plane. To construct. And two slant piles 1, 1
A new footing 6 that connects the pile heads of the pile group consisting of Thereafter, the newly installed footing 6 and the footing 3a of the existing building 2 are connected so that the load can be transmitted. Thus, a set pile A consisting of the two slant piles 1, 1
B is disposed so as to surround the existing building 2 when viewed in plan (FIG. 2).

FIGS. 3A and 3B and FIGS. 4A and 4B show the steps of constructing the slant pile 1 constituting the piles A and B. First, FIG. 3A
As shown in the figure, the casing pipe 11 provided with the excavation bit 12 at the tip edge penetrates into the ground 5 at an angle of about 10 to 30 degrees with respect to the vertical line to inject a ground stabilizing liquid such as bentonite. While excavating, the ground 5 is subjected to slime treatment after the excavation.

Next, as shown in FIG. 3B, a prefabricated pile 14 such as a steel pipe pile protruding above the ground at an angle substantially equal to the inclination angle of the casing pipe 11 is provided inside the casing pipe 11. Build. Thereafter, an injection material 15 such as cement milk or the like is injected into the gap between the inside of the casing pipe 11 and the ready-made pile 14 and the inside of the ready-made pile by using a grout hose or the like up to a ground level and filled. In addition, a procedure of reversing the construction procedure, injecting the filling material 15 first and filling the same, and then building the ready-made pile 14 can also be performed.

FIG. 4 shows details of the step of injecting the injection material 15.
As shown in A, the casing pipe 11 is pulled up at once or stepwise to the upper end of the fixing portion T between the ready-made pile 14, the injection material 15 and the ground 5, and the injection material 15 at the identification attachment portion T is pressurized. Injection is used to increase the fixing power as much as possible. Finally, as shown in FIG. 4B, the entire casing pipe 1 is pulled out to the ground and removed.
The curing process of one slanted pile 1 is completed by curing until the infused material 15 exhibits a predetermined strength.

The inclination angle of the casing pipe 11 is not limited to the above, but is designed within a range capable of sufficiently resisting a horizontal force. Further, since the hole wall after excavation is supported by the casing pipe 11, the risk of collapse of the hole wall is eliminated, and the hole wall can be implemented even at a large inclination angle. When the designed inclination angle of the casing pipe 11 is large and the stability of the construction machine itself is feared, a refill-type casing pipe is suitably implemented.

The ready-made pile 14 includes a steel pipe or a steel pipe concrete pile (SC) capable of sufficiently resisting a compressive force and a tensile force.
Pile) is suitably implemented. The method of filling the filling material 15 is not limited to the above, and the filling material 15 may be filled by pressurizing only the fixing portion T with the ready-made pile 14. In this case, the cavity above the fixing portion T is filled with sand, gravel or the like.

When the fixing portion T is set long,
The lifting of the casing pipe 11 is divided into a plurality of times, and the injection material 15 is pressurized each time. Therefore, one slanted pile 1 formed through the above-described construction process can be constructed at a desired inclination angle capable of sufficiently resisting a horizontal force as compared with the conventional slanted pile, and the prefabricated pile 14 and the injection material 15 can be formed. And the ground 5 are firmly fixed at the fixing portion T, so that the peripheral frictional resistance is large and the axial resistance with high proof stress can be exhibited. Therefore, when the new footing 6 provided on the pile head of the piles A and B composed of the slant pile 1 and the footing 3a of the existing building 2 are connected so that the load can be transmitted, for example, from the right side in FIG. The set pile A composed of the two slant piles 1, 1 arranged in the X direction effectively resists the horizontal force F acting in the X direction acting in the left direction, and is advantageous in that the bending moment is reduced. Develop support state. In addition, the set pile B installed in the Y direction effectively resists the horizontal force F ′ acting in the Y direction in FIG. 2, and thus the X, Y 2 acting on the entire existing building 2 is effective.
Two types of piles A and B opposing each other against horizontal force in the direction
, The seismic performance of the existing building 2 against the seismic force of the foundation 3 can be improved later. Similarly, stability against the liquefaction phenomenon can be maintained permanently.

In the above embodiment, the new footing 6 provided on the pile heads of the piles A and B and the foundation 3 of the existing building 2 are used.
Is connected to the footing 3a on the outer peripheral portion of the existing building as a means for connecting the load so that the load can be transmitted. However, the present invention is not limited to this. In addition, the present invention is not limited to the case where the present invention is applied to the outer peripheral portion of an existing building. In a building having a courtyard or the like, the present invention can be applied to the inner peripheral portion. Further, the piles A in the X and Y directions in FIG.
The number of B is the length and the pile diameter of the slant pile 1 that composes the group pile, the slant pile 1
The number may not necessarily be the same by suitably setting the inclination angle and the like for each direction.

In another embodiment, the casing pipe 11 eliminates the risk of collapse of the hole wall after excavation, and instead of the ground stabilizing liquid (bentonite stabilizing liquid) normally used at the time of excavating the ground, fresh water is used. And excavate the ground. When the bentonite stabilizing solution is used, a bentonite film is formed on the hole wall, and this forms a bentonite film on the outer periphery of the slanted pile 1. However, if Shimizu is used instead of bentonite, as shown in FIG. 5, it is possible to construct a slanted pile exhibiting an ideal peripheral friction resistance. Therefore, the seismic performance of the existing building foundation against the seismic force can be further improved, and the stability against the liquefaction phenomenon can be maintained permanently.

[0022]

According to the method of the present invention for reinforcing an existing building foundation with a slanted pile, the construction of the slanted pile eliminates the risk of collapse of the hole wall by the casing pipe supporting the hole wall after excavation. Therefore, it can be implemented even with a large inclination angle. In addition, all operations such as erection of a reinforcing steel cage and casting of concrete can be omitted, and it is only necessary to inject and fill the injectable material with a grout hose, so that no work is required for the construction. In addition, there is no risk of misalignment (center misalignment) due to the erection of the reinforcing cage, and the ready-made pile, the injection material and the ground are securely and firmly fixed at the fixing portion, so that the peripheral surface friction resistance is large and the high proof stress is high. A slanted pile having the axial resistance described above can be realized. As a result, if the pile head of the group pile composed of the inclined piles and the existing building foundation are connected so that the load can be transmitted, the seismic performance against the seismic force of the existing building foundation can be improved later, and It is possible to maintain the stability to the phenomena permanently.

In addition, the stability of the construction machine can be maintained by adding the casing pipes and the ready-made piles together.

[Brief description of the drawings]

FIG. 1 is a front view schematically illustrating a method of reinforcing an existing building foundation with a slant pile according to the present invention.

FIG. 2 is a plan view schematically showing a method of reinforcing an existing building foundation with a slant pile according to the present invention.

FIG. 3A is a cross-sectional view showing a step of excavating the ground with a casing pipe, and FIG. 3B is a cross-sectional view showing a step of installing a ready-made stake and filling an injection material.

FIG. 4A is a cross-sectional view showing a stage in which an injection material at a fixing portion is pressed, and FIG.

FIG. 5 is a graph showing a comparison of the surface friction resistance between a case where the ground is formed by excavating the ground with a bentonite stable liquid and a case where the ground is formed by excavating the ground with fresh water.

FIG. 6 is a schematic view showing the function of a set pile composed of two inclined piles.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oblique pile 2 Existing building 3 Foundation 3a Footing 3b Foundation beam 4 Pile 5 Ground 6 New footing 11 Casing pipe 12 Drilling bit 14 Precast pile 15 Injection material A Pile pile B Pile pile

Claims (4)

[Claims] 1. A slant pile is arranged in the ground near a foundation of an existing building, and a pile head of the slant pile and a foundation of the existing building are connected so that a load can be transmitted. The following steps (a) to (e) are to be carried out. (A) A casing pipe provided with a drill bit at the tip edge is penetrated into the ground at an angle of a slant pile with respect to the vertical line. Excavating the ground, slime-treating the inside of the excavation hole after the excavation, (b) embedding a ready-made pile in the casing pipe, and (c) filling the injection material in the casing pipe. (D) pulling up the casing pipe to the upper end of the fixing portion, and pressing the injection material at the identification attachment portion; (e) pulling the casing pipe to the ground and removing it, the injection material exhibits a predetermined strength Curing process until A method of reinforcing existing building foundations with slanted piles, each of which features: 2. A diagonal pile is arranged in the ground near a foundation of an existing building, and a pile head of the diagonal pile is connected to a foundation of the existing building so that a load can be transmitted. The following steps (a) to (e) are to be carried out. (A) A casing pipe provided with a drill bit at the tip edge is penetrated into the ground at an angle of a slant pile with respect to the vertical line. Excavating the ground, slime-treating the inside of the excavation hole after excavation, (b) filling the inside of the casing pipe with an injection material, and (c) embedding a ready-made pile inside the casing pipe. (D) pulling up the casing pipe to the upper end of the fixing portion, and pressing the injection material at the identification attachment portion; (e) pulling the casing pipe to the ground and removing it, the injection material exhibits a predetermined strength Curing process until A method of reinforcing existing building foundations with slanted piles, each of which features: 3. The two slanted piles are approximately 180 in plane one by one.
An existing building foundation with slant piles according to claim 1 or 2, characterized in that the piles are constructed by connecting the heads of the slant piles in a symmetrical arrangement by changing the orientation in order, and connecting the pile heads of the slant piles. Reinforcement method. 4. The method for reinforcing an existing building foundation with slanted piles according to claim 1, wherein fresh water is injected through a casing pipe to excavate the ground.