JP2007169879A - Pile foundation structure for restraining unequal settlement and its construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pile foundation structure for restraining unequal settlement of a structure, that is, the pile foundation structure belonging to a technological field of its construction method, in other words, restraining the unequal settlement by controlling settlement rigidity by peripheral surface friction by securing bearing power of a pile against overturning in an earthquake, and also to provide its construction method. <P>SOLUTION: Among foundation piles supporting the structure, a foundation pile arranged in an outer peripheral part is constituted for reducing rigidity of the peripheral surface friction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention belongs to the technical field of a pile foundation structure and its construction method that suppresses the uneven settlement of structures, and more specifically, it secures the support force of the pile against overturning during an earthquake and reduces the settlement rigidity due to circumferential friction The present invention relates to a pile foundation structure that suppresses uneven settlement at all times and a construction method thereof.

  Conventionally, a plurality of foundation piles that support a structure have a so-called group pile effect in which the settlement of the foundation pile 200 at the center of the structure 100 increases as shown in FIG. 5 even when the load per one is equal. Since P (lower in FIG. 5) is generated, problems such as a large deformation angle of the foundation beam 300 and the foundation pile 200 and damage such as cracks are known.

In order to suppress the uneven settlement of the structure having the pile foundation as described above, the following measures are taken.
For example, as shown in FIG. 6, the foundation beam 300 is increased in width or warp, or the main reinforcement is increased to be reinforced, or as shown in FIG. 7, a foundation with large settlement located in the central portion C of the structure 100. There is a method of making the pile 200 thick or adding the foundation pile 200 as shown in FIG. 8 to make the normal settlement uniform (suppressing the uneven settlement).

  In Patent Document 1 below, after a tension material is inserted into a drilling hole for pile driving formed in the ground and fixed to the lower end, concrete is placed in the drilling hole to form a pile body. A pile foundation structure is disclosed in which a predetermined load is applied to the pile body in advance with a tension material to cause the pile body to sink to a predetermined depth, and then the tension material is removed to suppress uneven settlement.

  In Patent Document 2, a long friction pile is used in the central portion where the amount of subsidence and distribution load of the structure is large, and a short friction pile is used in the outer peripheral portion where the amount of subsidence and distribution load is small. A foundation structure for controlling the uneven settlement is disclosed.

JP 7-324330 A Japanese Patent Application No. 2002-61203

  The method of reinforcing the foundation beam 300 shown in FIG. 6 can certainly equalize the group pile effect P (bottom of FIG. 6) (normally sink) and suppress uneven settlement. However, an increase in the amount of excavation due to a decrease in the level of the foundation beam 300 and an increase in the material of the foundation cause an economic burden, and an environmental load that increases the excavation residual soil of the structure becomes a problem. In addition, when an earthquake occurs, a high axial force is applied to the foundation pile 200 located at the outer peripheral portion of the foundation of the structure 100 as compared with the central portion (lower side in FIG. 6 (sinking during an earthquake)). Therefore, the axial force is redistributed to each pile by increasing or increasing the number of the foundation piles 200 at the outer peripheral portion, and the respective foundation piles 200 arranged at the outer peripheral portion and the central portion are uniformly subsidized. The design must be cumbersome so that the distribution is achieved. Even if the subsidence distribution is made uniform and the uneven subsidence is suppressed, the weight of the foundation beam 300 increases because the weight of the foundation pile 200 at the outer peripheral portion is increased.

  The reinforcing method for increasing or increasing the number of foundation piles 200 arranged in the central portion C shown in FIGS. 7 and 8 is also uniform because the group pile effect P (below FIGS. 7 and 8) is made uniform (always sinks). Settling can be suppressed. However, the bearing capacity that is secured is a normal one, and the bearing capacity against a fall during an earthquake is not taken into consideration. In order to secure the bearing capacity at the time of an earthquake, as described above, the foundation piles arranged at the outer peripheral part must be reinforced, but the structure is not able to suppress the uneven settlement.

  Although the technique described in the said patent document 1 is the pile foundation structure which suppressed the uneven settlement, it is the description content for one foundation pile, and as mentioned above, the several foundation pile which supports a structure It does not consider the group pile effect that the settlement of the central part of the area becomes large. Therefore, it cannot be expected to secure the bearing force against the fall during an earthquake and to prevent the group pile effect.

  The technique described in the said patent document 2 adjusts the length etc. of a friction pile according to the amount of settlement of a structure, or a distributed load, and the point which suppresses non-uniform settlement is recognized. As described above, when an earthquake occurs, a higher axial force is applied to the foundation pile located at the outer peripheral portion of the foundation of the structure than the foundation pile at the center. Then, since the foundation pile of the outer peripheral part with little subsidence is shortened, the supporting force sufficient to prevent the fall at the time of an earthquake cannot be demonstrated. That is, there is a problem that the support force cannot be secured although the uneven settlement is suppressed.

  In short, none of the above-described conventional technologies has yet been provided with a pile foundation structure and a construction method thereof that suppress the unsettled settlement while ensuring a supporting force against a fall during an earthquake.

  An object of the present invention is to provide a pile foundation structure that sufficiently secures the bearing capacity of a pile against overturning during an earthquake, and that reliably suppresses uneven settlement by reducing settlement rigidity due to peripheral friction of the pile, and a construction method thereof There is to do.

As a means for solving the above-described problems of the prior art, a pile foundation structure for suppressing uneven settlement according to the invention described in claim 1 is:
In pile foundation structure that suppresses the uneven settlement of structures supported by multiple foundation piles,
Among the foundation piles that support the structure, the foundation piles arranged at the outer peripheral portion have a configuration in which settlement rigidity due to circumferential friction is reduced.

The invention described in claim 2 is a pile foundation structure for suppressing uneven settlement according to claim 1,
In pile foundation structure that suppresses the uneven settlement of structures supported by multiple foundation piles,
Of the foundation piles that support the structure, the foundation piles that are arranged on the outer periphery are provided with elastic bodies up to a certain length in the depth direction of the outer periphery of the piles to secure the support force of the foundation piles. The structure is characterized in that the settlement rigidity due to surface friction is reduced.

The construction method of the pile foundation structure which suppresses the uneven settlement according to the invention described in claim 3 is:
In the construction method of a pile foundation structure that suppresses the uneven settlement of the structure supported by multiple foundation piles,
Of the multiple foundation piles that support the structure, the foundation piles arranged at the outer periphery form a pile hole that excavates the foundation ground to the ground with less subsidence, and injects cement milk into the root consolidation part and shaft part After that, a ready-made foundation pile made by attaching an elastic body in a certain length range in the depth direction of the outer peripheral surface is dropped into the pile hole and constructed as a foundation pile with a reduced settlement rigidity due to peripheral surface friction It is characterized by that.

The construction method of the pile foundation structure which suppresses the non-uniform settlement according to the invention described in claim 4,
In the construction method of a pile foundation structure that suppresses the uneven settlement of the structure supported by multiple foundation piles,
Of the multiple foundation piles that support the structure, the foundation piles arranged at the outer periphery form a pile hole excavating the foundation ground to the ground with less subsidence, and deepen the elastic body through spacers on the outer periphery. A steel pile that has been wound to a certain length in the longitudinal direction is dropped into the pile hole, and concrete is placed from the inside of the reinforcing bar into the pile hole to construct a foundation pile with reduced circumferential friction rigidity. And

Invention of Claim 5 is the pile foundation structure which suppresses the uneven settlement described in any one of Claims 1-4, and its construction method,
The rigidity of circumferential friction is controlled by the length of the elastic body provided in the depth direction of the outer circumferential surface of the foundation pile.

Invention of Claim 6 is the pile foundation structure which suppresses the non-uniform settlement described in any one of Claims 1-5, and its construction method,
The elastic body is characterized by being rubber or rock wool.

The pile foundation structure which suppresses the uneven settlement described in claims 1 to 6 and the construction method thereof have the following effects.
1) Since the elastic body is provided on the outer peripheral surface of the foundation pile located at the outer peripheral part of the structure, the central part can be increased by reducing only the rigidity of the peripheral surface friction of the foundation pile at the outer peripheral part and increasing the settlement amount. The amount of subsidence of the foundation pile located in is equalized, so that the non-uniform subsidence can be rationally reduced to ensure the safety of the foundation structure, and it does not affect the bearing capacity of the pile foundation structure at all. Sufficient support for falling over during an earthquake can be secured.
2) Since the rigidity of the peripheral frictional force of the foundation pile is controllable, it is possible to design a settlement rigidity adapted to the scale of the superstructure and the ground condition.
3) Since it is not necessary to reinforce the foundation pile such as increasing the diameter of the foundation pile or increasing the number of piles, and increasing the width and the width of the foundation beam, increasing the amount of main reinforcement, etc. Costs can be reduced and the amount of soil remaining due to reinforcement work can be reduced, improving the environmental load.

The present invention is a pile foundation structure that suppresses the uneven settlement of a structure supported by a plurality of foundation piles.
Of the plurality of foundation piles 2 that support the structure 1, the foundation pile 2 disposed in the outer peripheral portion S has a configuration in which settlement rigidity due to circumferential friction is reduced.

  Hereinafter, an embodiment of a pile foundation structure and its construction method for suppressing uneven settlement according to the present invention will be described based on the drawings. The pile foundation structure of the present invention is implemented in the foundation pile 2 that is configured to be able to sufficiently support the falling force at the time of an earthquake.

The pile foundation structure shown in FIG. 1 is the depth of the outer peripheral surface in the foundation pile 2 arrange | positioned in the outer periphery site | part S among the several foundation pile 2 ... casted to the support layer H which supports the structure 1. FIG. The elastic body 3 is provided in the direction up to a certain length range to secure the supporting force of the foundation pile, and only the rigidity of the circumferential friction is reduced. As a method for appropriately controlling the rigidity of the peripheral surface friction (also referred to as settlement rigidity), it is possible to change the length range of the elastic body 3 in the depth direction.
As shown in the drawing, the length range of the elastic body 3 in the depth direction is the longest foundation pile 2 in the outer peripheral portion S where the support force is the longest, and is designed to shorten toward the center C in order to balance the entire pile. It is preferable.

  The elastic body 3 is, for example, rubber or rock wool (the invention according to claim 5). Both are strong, but less rigid than the ground, and follow the deformation.

  In the above configuration, as shown in FIG. 1B, the settlement amount of the foundation pile 2 arranged in the outer peripheral portion S is increased by the amount of settlement of the foundation pile 2 arranged in the central portion C having the largest settlement amount. Uneven settlement is suppressed by making it uniform. That is, while maintaining the supporting force against the fall of the conventional pile foundation structure during an earthquake, only the rigidity of the peripheral friction of the foundation pile 2 of the outer peripheral portion S with less subsidence is reduced, and the foundation pile 2 of the central portion C is reduced. The difference in subsidence (dissimilar subsidence) is made uniform (suppressed).

The above action is shown in the graph of FIG. FIG. 2A shows the relationship between the normal load and settlement of the foundation pile 2 located in the central portion C. FIG. The subsidence amount X of the central portion C is a value obtained by adding the tip support force X1 and the peripheral friction force X2, and the angle indicates rigidity.
FIG. 2B shows a comparison between the normal load and settlement of the foundation pile 2 arranged in the outer peripheral portion S and the amount of settlement X. The sinking amount Y of the outer peripheral portion S is also a value obtained by adding the tip support force Y1 and the peripheral surface friction force Y2, and the angle is rigid. It can be seen that only the rigidity of the circumferential frictional force Y2 is reduced as shown. Therefore, even if the supporting force against the overturn at the time of the earthquake is the same, the settlement amount Y of the foundation pile 2 at the outer peripheral portion S is less than the settlement amount X of the foundation pile 2 at the center C. The settlement amount of the entire foundation pile is made uniform. Uniformity, in other words, suppresses uneven settlement.

Next, a method for constructing the pile foundation structure of Example 1 using embedded piles will be described.
Of the foundation piles 2 that support the structure 1, the foundation piles 2 arranged in the outer peripheral portion S are first provided with a pile hole in which the foundation ground is excavated to the ground H with a small amount of subsidence by an excavator or the like, and then solidified. After injecting cement milk into the part and the shaft part, the ready-made foundation pile 2 formed by attaching the elastic body 3 to a certain length range in the depth direction of the outer peripheral surface is dropped into the pile hole, and by the peripheral friction force It is constructed as a foundation pile with reduced settlement rigidity (the invention according to claim 3).

  As a method of constructing the foundation pile 2 by the cast-in-place pile, as shown in FIG. 3, after providing the pile hole 4 on the foundation ground with an excavator or the like, the elastic body 3 is formed on the outer periphery of the foundation pile 2 to be constructed. In such a case, the reinforcing bar 5 in which the elastic body 3 is wound to a certain length in the depth direction via the spacer 5a is dropped into the pile hole 4, and the pile hole 4 is inserted from the inside of the reinforcing bar 5 It is good also as a method of constructing the foundation pile 2 by placing concrete into the heel. Moreover, as shown in FIG. 4A, instead of the reinforcing bar 5, a steel pipe 6 to which the elastic body 3 is attached up to a certain length range in the depth direction of the outer peripheral surface is dropped into the pile hole 4, and the hollow portion of the steel pipe 6 And the concrete pile is cast in the pile hole 4, and the foundation pile 2 is constructed. Conversely, as shown in FIG. 4B, the elastic body 3 is attached to the inner peripheral surface of the steel pipe 6, and the hollow portion of the steel pipe 6 and the pile A method of placing concrete into the hole 4 is also conceivable. The steel pipe 6 does not need to have a length over the entire length of the pile hole 4 and can be implemented with substantially the same length and the same arrangement as the elastic body 3 as illustrated.

  The method of attaching the elastic body 3 to the inner peripheral surface of the steel pipe 6 is the construction of a core pile 7 to which the elastic body 3 is attached to the outer peripheral surface of a concrete pile manufactured by concrete placement, and inserting the core pile 7 into the steel pipe 6. The foundation pile 2 is constructed by placing concrete between the core pile 7. In this case, the steel pipe 6 conceptually acts the same as the ground surface. Therefore, there is no change in the technical idea that the elastic body 3 is attached to the outer peripheral surface of the foundation pile 2.

  The present invention reduces the settlement rigidity of the outer peripheral portion by reducing the rigidity of the peripheral surface friction of the pile while sufficiently securing the support force of the pile against the fall during an earthquake, and rationally suppresses the uneven settlement. .

  The embodiments have been described with reference to the drawings. However, the present invention is not limited to the illustrated embodiments, and design modifications and application variations that are usually made by those skilled in the art are within the scope of the technical idea of the invention. I will add a note to include the range.

A is an elevational view showing an example of a pile foundation structure for suppressing uneven settlement according to the present invention. B is the figure which showed the relationship between the change of the settlement amount of the whole foundation pile in A, and a group pile effect. A is the figure which showed the relationship between the settlement of the foundation pile arrange | positioned in the center part of a structure, and a load. B is the figure which compared the relationship between the settlement of the foundation pile arrange | positioned in A and the outer peripheral site | part of a structure, and a load. It is one Example which shows the outline | summary of the construction method of the pile foundation structure which suppresses the uneven settlement according to this invention. A and B are other examples which show the outline of the construction method of the pile foundation structure which controls the uneven settlement according to the present invention. It is the reference figure which showed the amount of settlement applied to a foundation pile at the time of an earthquake and the group pile effect which acts on a structure. It is the reference figure which showed the prior art example which reinforces a foundation beam and suppresses non-uniform settlement. It is the reference figure which showed the prior art example which thickens the foundation pile arrange | positioned in the center part of the foundation of a structure, and suppresses uneven settlement. It is the reference figure which showed the prior art example which arrange | positions a several foundation pile in the center part of the foundation of a structure, and suppresses uneven settlement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Existing building 2 Foundation pile 3 Elastic body 4 Pile hole 5 Reinforcement rod 6 Steel pipe

Claims (6)

In pile foundation structure that suppresses the uneven settlement of structures supported by multiple foundation piles,
The pile foundation structure which suppresses uneven settlement, wherein the foundation pile arranged in the outer peripheral part among the foundation piles supporting the structure has a structure in which settlement rigidity due to circumferential friction is reduced. In pile foundation structure that suppresses the uneven settlement of structures supported by multiple foundation piles,
Of the foundation piles that support the structure, the foundation piles that are arranged on the outer periphery are provided with elastic bodies up to a certain length in the depth direction of the outer periphery of the piles to secure the support force of the foundation piles. The pile foundation structure for suppressing uneven settlement according to claim 1, characterized in that the settlement rigidity due to surface friction is reduced. In the construction method of a pile foundation structure that suppresses the uneven settlement of the structure supported by multiple foundation piles,
Of the multiple foundation piles that support the structure, the foundation piles arranged at the outer periphery form a pile hole that excavates the foundation ground to the ground with less subsidence, and injects cement milk into the root consolidation part and shaft part After that, a ready-made foundation pile made by attaching an elastic body in a certain length range in the depth direction of the outer peripheral surface is dropped into the pile hole and constructed as a foundation pile with a reduced settlement rigidity due to peripheral surface friction A method for constructing a pile foundation structure that suppresses uneven settlement. In the construction method of a pile foundation structure that suppresses the uneven settlement of the structure supported by multiple foundation piles,
Of the multiple foundation piles that support the structure, the foundation piles arranged at the outer periphery form a pile hole excavating the foundation ground to the ground with less subsidence, and deepen the elastic body through spacers on the outer periphery. A steel pile that has been wound to a certain length in the longitudinal direction is dropped into the pile hole, and concrete is placed from the inside of the reinforcing bar into the pile hole to construct a foundation pile with reduced circumferential friction rigidity. The construction method of the pile foundation structure which suppresses uneven settlement.   The stiffness of peripheral friction is controlled by the length of an elastic body provided in the depth direction of the outer peripheral surface of the foundation pile, and the uneven settlement according to any one of claims 1 to 4 is suppressed. Pile foundation structure and its construction method.   The pile foundation structure which suppresses the uneven settlement according to any one of claims 1 to 5, and the construction method thereof, wherein the elastic body is rubber or rock wool.

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