JP4713297B2 - Foundation structure and construction method of foundation structure - Google Patents

Description

  The present invention relates to a foundation structure and a construction method of the foundation structure, and more particularly to a foundation structure that supports an upper structure using a pile foundation and a direct foundation in combination, and a construction method thereof.

Conventionally, a foundation structure (a piled raft foundation) using a pile foundation and a direct foundation in combination is known (see, for example, Patent Document 1).
The piled raft foundation supports the load of the superstructure by the bearing force of both the pile foundation stopped by the intermediate layer with a small bearing capacity without reaching the support layer and the direct foundation formed on the ground surface. Is. Then, the pile with the pile tip stopped by an intermediate layer sinks by a small amount due to the vertical load of the superstructure, so that the direct foundation receives ground reaction force, and the bearing capacity and subsidence amount of the pile foundation and direct foundation Is a foundation structure in which the pile foundation and the direct foundation share the load and support the load. In such a piled raft foundation, by sharing the vertical load between the pile foundation and the direct foundation, the number of piles and the pile diameter can be saved and the cost can be reduced compared to the foundation structure of the pile foundation alone. At the same time, it has the advantage that it can be applied to ground where the ground strength is not sufficient and the load cannot be supported directly by the foundation alone, or the subsidence amount becomes too large.

JP 2002-129484 A

However, in the conventional piled raft foundation as described in Patent Document 1, since the pile tip is stopped by an intermediate layer having a small supporting force, it is compared with the pile foundation when the pile tip penetrates into the supporting layer. As a result, the tip support force of the pile is reduced, and even if the support force of the pile foundation and the support force of the direct foundation are combined, a sufficiently large support force cannot be secured, and there is a problem that it can be applied only to small buildings. And in order to secure the bearing capacity of the pile tip, the pile diameter must be increased or the number of piles must be increased, and the cost reduction effect as described above cannot be obtained sufficiently. End up.
Furthermore, with the conventional piled raft foundation, the tip of the pile stops at the middle layer, so when applied to soft ground, it is difficult to control the settlement of the foundation directly with the pile. There is a possibility that the building may be inclined, and there is a problem that it is difficult to apply to soft ground with low earth bearing capacity.

  An object of the present invention is to provide a foundation structure and a construction method of the foundation structure that can secure a sufficient supporting force and can reduce the cost, and can expand the application range regardless of the hardness of the ground. It is in.

The foundation structure according to claim 1 of the present invention is a foundation structure that supports an upper structure using a pile foundation and a direct foundation in combination, and a pile body that penetrates the ground, and a pile body that has penetrated the ground. A bottom plate portion connected to the pile head and formed on the ground, and after confirming that the pile tip of the pile body has reached the support layer, loosen the ground near the pile tip, The support force by the pile body, which combines both the tip support force and the peripheral friction force of the pile body , which is exhibited by sinking a predetermined amount due to the load of the pile, and the subsidence by sinking with this pile body The load of the upper structure is supported by both the supporting force by the bottom plate portion that is exerted by receiving a force, and the pile body is formed in a spiral shape or a plurality of plates at the tip of the pile A steel pipe pile having blades and penetrating into the ground by rotation. Is confirmed that the pile tip has reached the support layer based on the torque value at the time of penetration into the ground, and after confirming the support layer, the depth position of the pile tip is maintained and at least one of the penetration direction and the reverse direction is maintained. The ground near the tip of the pile is loosened by the rotation of the steel pipe pile .

According to the present invention described above, after confirming that the tip of the pile has reached the support layer, the ground near the tip of the pile is loosened, and then the pile body sinks by the amount loosened by applying the load of the superstructure. As a result, the support force at the tip of the pile is exerted, and the ground reaction force acts on the bottom plate part that sinks as the pile body sinks to obtain the support force. The superstructure can be supported. Therefore, it is possible to secure sufficient support force at the tip of the pile and to obtain the support force of the foundation directly, so that the support force of the entire foundation structure can be increased, while reducing costs without increasing the pile diameter and the number of piles. Therefore, it can be applied to a building having a large scale (large column axial force).
Furthermore, since the pile body sinks by the amount that the pile tip ground has been loosened in advance and the bearing capacity is exerted, it is difficult for the pile body to sink further downward than the sinked position, and the surface ground is soft. Even if it exists, unequal settlement can be prevented. Therefore, the foundation structure of the present invention can be applied to soft ground, and the application range of the combined foundation structure of the pile foundation and the direct foundation can be expanded.
Here, the bottom plate portion may be configured in Caps formed pile head portion and being composed of fabric basis along the foundation beams and, withstand voltage plate covering the underlying bottom (solid basis) It may be composed of

Further, as the support layer of the earth plate, ground survey N value obtained by the (boring survey, etc.) a predetermined value (for example, N value 50) or a more formations, the shear wave velocity is a predetermined value (for example, 400m / s) or more, but in such a support layer, the driving torque value in the pile driving machine for rotating and press-fitting increased rapidly, and the pile tip reached the support layer. Has been confirmed.

Furthermore, the foundation structure according to claim 2 of the present invention is the foundation structure according to claim 1 , wherein the ground near the tip of the loosened pile is rooted , and this root-solidified portion together with the pile body supporting force and supporting force by the bottom plate portion by the pile body by subsidence, characterized in that it is exerted.
According to such a configuration, it is possible to stabilize the obtained tip support force and the amount of settlement by injecting a root hardening material such as cement milk into the ground in the vicinity of the loosened pile tip and solidifying the root. In other words, when not rooting, the settlement characteristics (settlement amount, support force, etc.) of the pile tip may change depending on the shape of the blade at the tip of the pile, etc. There is no difference in the pile tip conditions due to the shape of the blades, and stable settlement characteristics can be obtained.

Moreover , the construction method of the foundation structure of Claim 3 of this invention is a construction method of the foundation structure which supports an upper structure using a pile foundation and a direct foundation together, Comprising: Spiral form or several or more at the pile front-end | tip A support layer confirmation procedure for rotating a steel pipe pile having blades made of plates and penetrating into the ground and confirming that the tip of the pile has reached the support layer based on the torque value at the time of ground penetration, and the support layer confirmation procedure Later, while maintaining the depth position of the pile tip, rotate to at least one of the penetration direction and the reverse direction, loosen the pile tip ground, and connect to the pile head of the steel pipe pile after the ground penetration And a direct foundation forming procedure for forming a bottom slab portion on the ground, and the steel pipe pile is sunk by a predetermined amount due to the load of the steel pipe pile and the upper structure constructed above the bottom slab portion. tip supporting force of the steel pipe pile and skin friction A supporting force by the pipe pile that combines both the load of the upper structure by the supporting force of both the supporting force, by the bottom plate portion sinks in accordance with this steel pipe pile is characterized in that it is supported.

According to the construction method described above, as in the case of the foundation structure described above, the support force of the pile tip can be sufficiently secured and the support force of the foundation can be obtained directly. It can be applied to a large-scale building while reducing. Furthermore, it can be applied to soft ground, and the application range of combined foundation structures of pile foundations and direct foundations can be expanded. Further, by idle vanes made of threaded spiral or a plurality of plate at the same depth position, it is possible to easily loosen the pile near the tip of the ground.

Furthermore, the construction method of the foundation structure according to claim 4 of the present invention is the construction method of the foundation structure according to claim 7 or claim 8, wherein after the pile tip ground relaxation procedure, It is provided with a rooting procedure for injecting cement milk into the ground and solidifying it, and by substituting the solidified root-solidified part together with the pile body, the supporting force by the pile body and the supporting force by the bottom plate part are exhibited. It is characterized by that.
According to such a configuration, as described above, by stabilizing the ground in the vicinity of the loose pile tip, it is possible to eliminate the variation in the settlement property due to the blade shape of the pile tip and obtain a stable settlement property. .

  According to the foundation structure and the foundation structure construction method of the present invention as described above, it is possible to reduce the cost by sufficiently securing the supporting force, and it is possible to expand the application range regardless of the hardness of the ground. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a building 1 having a foundation structure according to an embodiment of the present invention. 2A to 2D are diagrams for explaining the construction procedure of the steel pipe pile 2 in the foundation structure of the building 1.
In FIG. 1, a building 1 includes a pile foundation composed of a plurality of steel pipe piles (pile bodies) 2 penetrating into the ground G, and a direct foundation composed of a pressure plate 3 that is a bottom slab formed on the ground G. The base structure which supports the upper structure 4 in combination is provided.
The pressure plate 3 is made of a reinforced concrete structure in which the steel pipe pile 2 is penetrated into the ground G and then the ground surface is excavated, and then connected (integrated) with the pile head of the steel pipe pile 2 via a footing (pile cap) 5. It is a slab. And the pressure-resistant plate 3 can transmit the load of the upper structure 4 to the ground G by receiving the ground reaction force of the ground G from below.

The steel pipe pile 2 has a steel pipe pile main body 2A formed of a circular steel pipe and a spiral blade 2B fixed to the tip (lower end) of the steel pipe pile main body 2A. As shown in FIG. 2, the steel pipe pile 1 is rotated by the rotary press-fitting device C of the pile driving machine M, and the blade 2 </ b> B is screwed into the ground G and penetrates into the ground G.
That is, as shown in FIG. 2 (A), the steel pipe pile 2 is built by the pile driving machine M, and as shown in FIG. 2 (B), the steel pipe pile 1 is set vertically at the pile core position.
Next, as shown in FIGS. 2C and 2D, the steel pipe pile 2 is penetrated into the ground G by rotating the rotary press-fitting device C and screwing the blades 2B into the ground G (rotational press-fitting procedure). .
In addition, although the case where the steel pipe pile 2 is not connected up and down was illustrated in FIG. 2, this steel pipe pile 2 may be used as a lower pile, and an upper pile may be welded and integrated on it, and 3 More than this steel pipe pile 2 may be connected and a lower pile, a middle pile, and an upper pile may be integrated, and even in that case, as a construction method, a substantially similar procedure will be repeated. Further, as the pile driving machine M, a torso gripping type fully swiveling casing jack or the like can be used in addition to the illustrated one.

  In the rotary press-fitting procedure described above, the rotary press-fitting device C of the pile driving machine M is provided with a measuring machine that measures the rotary torque value acting on the steel pipe pile 2 during the rotary press-fitting, and manages this torque value. Thus, it can be determined whether the tip of the steel pipe pile 2 is in the intermediate layer G1 (FIG. 3) in the ground G or has reached the support layer G2. That is, it is known that the torque value acting on the steel pipe pile 2 varies according to the N value of the ground G. When the tip of the steel pipe pile 2 reaches the support layer G2 where the N value increases, the torque value is Since it rapidly rises, it can be determined that the support layer G2 has been reached (support layer confirmation procedure).

Hereinafter, regarding the pile tip ground relaxation procedure performed after the support layer confirmation procedure, the first embodiment will be described based on FIG. 3, the second embodiment will be described based on FIGS. 4 to 6, and the pile tip ground relaxation. A third embodiment will be described with reference to FIGS. 7 and 8 regarding a consolidation procedure performed after the procedure.
In the following embodiments, the same constituent members as those described in the first embodiment and the constituent members having the same functions are denoted by the same reference numerals as those in the first embodiment. The description of is omitted or simplified.

[First Embodiment]
Drawing 3 is a sectional view showing the construction method of the foundation structure concerning a 1st embodiment.
In the above-mentioned support layer confirmation procedure, after confirming that the tip of the steel pipe pile 2 has reached the support layer G2, the steel pipe pile 2 is further rotationally press-fitted by the rotary press-fitting device C of the pile driving machine M to obtain a predetermined depth ( For example, the pile tip is penetrated into the support layer G2 by the diameter of the steel pipe pile main body 2A).
Next, the steel pipe pile 2 is rotated in one of the penetration direction and the reverse direction or alternately in a state in which the position of the penetrated pile tip is maintained. This rotation causes the blade 2B to idle at a certain depth position, thereby loosening the ground G2A in the vicinity of the pile tip of the steel pipe pile 2 (pile tip ground loosening procedure).

After the plurality of steel pipe piles 2 have penetrated into the ground as described above, the footing 5 shown in FIG. 1 is fixed to the pile head of the steel pipe pile 2, and the pressure plate 3 is integrated with the footing 5 in the ground G. It is constructed above and connected to the steel pipe pile 2 (direct foundation forming procedure).
Further, the upper structure 4 is sequentially constructed on the upper side of the steel pipe pile 2, the footing 5 and the pressure plate 3, and the load of the upper structure 4 acts on the steel pipe pile 2 through the footing 5 to loosen the ground G2A. The steel pipe pile 2 sinks according to the height dimension. The ground G2A loosened with the settlement of the steel pipe pile 2 is gradually compacted, and the supporting force RP1 at the tip of the pile is exhibited according to the amount of settlement, along with the supporting force RP2 due to the peripheral friction of the steel pipe pile body 2A. The bearing capacity (RP1 + RP2) of the steel pipe pile 2 is exhibited.

As the steel pipe pile 2 sinks, the footing 5, the pressure plate 3 and the upper structure 4 also sink, and as the pressure plate 3 sinks, the ground G on the bottom surface is gradually compacted, depending on the amount of settlement. Support force RS due to reaction force is exhibited.
After sinking to a position where the support force (RP1 + RP2) of the steel pipe pile 2 and the support force RS of the bottom face of the pressure plate 3 balance with the load of the entire building 1 including the upper structure 4, the settlement stops. As a result, the load of the superstructure 4 is supported by the supporting force (RP1 + RP2 + RS) of both the steel pipe pile 2 and the pressure plate 3, that is, both the pile foundation and the direct foundation.

According to this embodiment, there are the following effects.
(1) That is, after confirming that the pile tip of the steel pipe pile 2 has reached the support layer G2, the ground G2A in the vicinity of the pile tip is loosened, and then the amount loosened by applying the load of the upper structure 4 The steel pipe pile 2 sinks and the support force RP1 at the tip of the pile is exerted, and the ground reaction force acts on the bottom surface of the pressure plate 3 that sinks as the steel pipe pile 2 sinks, resulting in the support force RS. The upper structure 4 can be supported by the supporting force (RP1 + RP2 + RS) of both the steel pipe pile 2 and the pressure plate 3. Therefore, sufficient support force RP1 at the tip of the pile can be secured sufficiently and the support force RS of the foundation can be obtained directly, so that the support force of the entire foundation structure (RP1 + RP2 + RS) can be increased, and the pile diameter and number of piles can be increased. Thus, the present invention can be applied to a large-scale building 1 while reducing costs.

(2) Further, since the steel pipe pile 2 sinks by the amount of loosening the pile tip ground G2A in advance and the supporting force RP1 is exerted, the steel pipe pile 2 is less likely to sink further downward than the sinked position. And since the amount of settlement in a plurality of steel pipe piles 2 can be equalized, even if the surface layer ground is soft, uneven settlement can be prevented. Therefore, the pile foundation and the foundation structure combined with the direct foundation can be applied to the soft ground, and the application range can be expanded.

(3) In addition, by managing the torque value of the steel pipe pile 2 by the rotary press-fitting device C of the pile driving machine M that rotationally presses the steel pipe pile 2, it is easily and accurately determined that the pile tip has reached the support layer G2. The construction can be speeded up and facilitated. Furthermore, the blade 2B is idled at the same depth position without changing the depth position of the steel pipe pile 2 after penetrating into the support layer G2, so that the ground G2A in the vicinity of the pile tip can be easily rotated. Can be loosened.

[Second Embodiment]
FIGS. 4A and 4B and FIGS. 5A and 5B are cross-sectional views showing a construction method of the foundation structure according to the second embodiment, respectively.
In this embodiment, after confirming that the tip of the steel pipe pile 2 has reached the support layer G2 in the above-described support layer confirmation procedure, as shown in FIG. 4 (A), the rotary press-fitting device C of the pile driving machine M is used. Thus, the steel pipe pile 2 is further rotated to penetrate the pile tip into the support layer G2 by a predetermined depth.
Next, the steel pipe pile 2 is pulled up to the position shown in FIG. 4B by rotating the rotary press-fitting device C in the reverse direction from the position where the tip of the pile penetrates the support layer G2 by a predetermined depth. By pulling up the steel pipe pile 2 in this way, the ground G2B for the height dimension in the vicinity of the pile tip of the steel pipe pile 2 is loosened (pile tip ground loosening procedure). And the pile front-end | tip position of the steel pipe pile 2 after raising is located below the support layer G2 upper surface.
On the other hand, in FIG. 5, after confirming that the tip of the steel pipe pile 2 has reached the support layer G2, as shown in FIG. 5 (A), the rotary press-fitting device C without penetrating the pile tip into the support layer G2. Is rotated in the reverse direction and the steel pipe pile 2 is pulled up to the position shown in FIG. 5 (B). That is, the pile tip position of the steel pipe pile 2 after being pulled up is positioned above the upper surface of the support layer G2.

Since the procedure after penetrating the plurality of steel pipe piles 2 into the ground as described above is substantially the same as the procedure of the first embodiment, description thereof will be omitted.
And as shown in FIG. 5, even if it is a case where a pile front-end | tip is located so that it may be located above the support layer G2 upper surface, the front-end | tip of the steel pipe pile 2 is carried out to the support layer G2 in the above-mentioned support layer confirmation procedure. Even if the upper surface of the support layer G2 is uneven and the depth position varies, or the upper surface of the support layer G2 is inclined, as shown in FIG. The distance between the tip of the pile and the upper surface of the support layer G2 can be made constant. This makes it possible to homogenize the strength and rigidity of the ground G2B, which is loosened by pulling up the steel pipe pile 2, and stabilize the amount of settlement due to the load of the upper structure 4 and the tip support force RP1 exhibited after the settlement. Can do.

According to the present embodiment, in addition to the effects substantially similar to the above (1) and (2), there are the following effects.
(4) That is, by managing the torque value of the steel pipe pile 2 by the rotary press-fitting device C of the pile driving machine M that rotationally presses the steel pipe pile 2, it is easily and accurately determined that the pile tip has reached the support layer G2. The construction can be speeded up and facilitated. Furthermore, after confirming the support layer G2 or penetrating the support layer G2, the ground G2B in the vicinity of the tip of the pile can be easily loosened by pulling the steel pipe pile 2 by reverse rotation.

[Third Embodiment]
7A and 7B are a side view and a bottom view showing the steel pipe pile 2 in the foundation structure according to the third embodiment. FIG. 8 is a cross-sectional view showing the steel pipe pile 2 after construction.
In the steel pipe pile 2 of this embodiment, a pipe 2C for cement milk injection, which is a root hardening material, is disposed in the steel pipe pile main body 2A so as to open to the bottom surface of the blade 2B. And this pipe 2C is continuously provided to the ground above the pile head of the steel pipe pile 2, and after penetration of the steel pipe pile 2 into the ground G, cement milk is applied to the pile tip ground from the ground through the pipe 2C. It can be injected.
In this embodiment using the steel pipe pile 2 described above, after loosening the pile tip ground G2A, G2B of the steel pipe pile 2 in the pile tip ground loosening procedure of the first embodiment or the second embodiment described above, the pipe 2C While discharging the cement milk, the steel pipe pile 2 is rotated to fill the periphery of the blade 2B with the cement milk, and the filled cement milk is solidified to form a rooted portion 2D at the tip of the pile (root consolidation procedure).
The root hardening portion 2D may be formed below the upper surface of the support layer G2, may be formed above the upper surface of the support layer G2, and further formed near the upper surface of the support layer G2. May be.

According to the present embodiment, in addition to the above-described effects, the following effects can be obtained.
(5) That is, by stabilizing the loose ground near the tip of the pile with cement milk, variations in the settling property due to the blade 2B shape at the tip of the pile can be eliminated, and a stable settling property can be obtained.

In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.
For example, in the said embodiment, although the steel pipe pile 2 was used as a pile body, and the construction method which penetrates this steel pipe pile 2 to the ground G by rotary press fit, a cast-in-place concrete pile may be used as a pile foundation, and PC pile May be inserted into the ground G by an embedding method or a driving method. At this time, as a method of loosening the pile tip ground, there is a method using water flow or air pressure, or a member that is less rigid than the tip ground such as an elastic material, elastic-plastic material, etc. It is possible to adopt a method of interposing between the two.

In addition, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described with particular reference to certain specific embodiments, but without departing from the spirit and scope of the invention, Various modifications can be made by those skilled in the art in terms of material, quantity, and other detailed configurations.
Therefore, the description limiting the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

It is sectional drawing which shows the building provided with the foundation structure which concerns on embodiment of this invention. (A)-(D) is a figure explaining the construction procedure of the pile in the said foundation structure. It is sectional drawing which shows the construction method of the foundation structure which concerns on 1st Embodiment. (A), (B) is sectional drawing which shows the construction method of the foundation structure which concerns on 2nd Embodiment. (A), (B) is sectional drawing which shows the construction method of the foundation structure which concerns on 2nd Embodiment. It is sectional drawing which shows the said basic structure. (A), (B) is the side view and bottom view which show the pile in the foundation structure which concerns on 3rd Embodiment. It is sectional drawing which shows the pile after construction of 3rd Embodiment.

Explanation of symbols

  2 ... Steel pipe pile which is a pile body, 2B ... Blade, 3 ... Pressure-resistant plate which is bottom plate part, 4 ... Superstructure, G ... Ground, G2 ... Support layer.

Claims (4)

A foundation structure that supports the superstructure using a pile foundation and a direct foundation together,
A pile body penetrating into the ground, and a bottom plate portion formed on the ground connected to the pile head of the pile body after penetrating the ground,
After confirming that the pile tip of the pile body has reached the support layer, loosen the ground in the vicinity of the pile tip, and the tip support of the pile body that is exhibited by sinking by a predetermined amount due to the load of the upper structure Supporting both the supporting force by the pile body that combines both the force and the peripheral frictional force, and the supporting force by the bottom plate part that is exerted by receiving a ground reaction force by sinking with the pile body Supporting the load of the superstructure by force ,
The pile body is a steel pipe pile having a spiral or a plurality of blades at the tip of the pile and penetrating into the ground by rotation, and the steel pipe pile is based on a torque value at the time of the ground penetration. Is confirmed to have reached the support layer, and after confirmation of the support layer, it is rotated in at least one of the penetration direction and the reverse direction while maintaining the depth position of the pile tip. Basic structure characterized by loosened ground . The basic structure according to claim 1,
The ground near the tip of the loosened pile is rooted and supported by the pile body by sinking together with the pile body with respect to the loosened ground below the ground solidified portion. A foundation structure characterized by exerting force and supporting force by the bottom plate part . It is a construction method of a foundation structure that supports a superstructure using a pile foundation and a direct foundation together,
Check the support layer to check that the pile tip has reached the support layer based on the torque value at the time of ground penetration by rotating a steel pipe pile with a spiral or multiple plate blades at the tip of the pile and penetrating into the ground Procedure and
After the support layer confirmation procedure, while maintaining the depth position of the pile tip, rotate in at least one of the penetration direction and the reverse direction, loosen the pile tip ground, and a pile tip ground relaxation procedure,
Direct foundation formation procedure to form a bottom slab part on the ground connected to the pile head of the steel pipe pile after the ground penetration,
The steel pipe pile that combines both the tip support force and the peripheral frictional force of the submerged steel pipe pile when the steel pipe pile sinks by a predetermined amount due to the load of the superstructure constructed above the steel pipe pile and the bottom plate portion. A method for constructing a foundation structure, wherein a load of the upper structure is supported by a supporting force of both a supporting force by a pile and a supporting force by the bottom plate portion that sinks along with the steel pipe pile. In the construction method of the foundation structure according to claim 3,
After the pile tip ground loosening procedure, it is provided with a root hardening procedure in which cement milk is poured into the ground near the loose pile tip to solidify the soil, and the loose ground below the rooted solidified portion is provided . The foundation construction method is characterized in that the supporting force by the pile body and the supporting force by the bottom slab portion are exhibited by sinking the root-solidified portion together with the pile body .

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