JP2006214201A - Composite foundation of piles and continuous underground wall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite foundation of piles and a continuous underground wall, which efficiently and sufficiently bears axial-force load of a building built on soft ground, according to the ground structure, damps responsive displacement at the time of an earthquake to improve the habitability of the building, brings about upper skeleton reduction and change in structural type by virtue of reduction of input to a superstructure, achieves reduction of a pile cross sectional area and countermeasures against liquefaction, and contributes to total cost reduction and shortening of a construction period even if the continuous underground wall is employed. <P>SOLUTION: The soft ground 12 includes an intermediate layer 32 which is lower in rigidity than bearing ground 22 but higher than an upper layer 30. The continuous underground wall 18 is constructed so as to reach the depth of the intermediate layer 32, and the plurality of piles 16 reach the depth of the bearing ground 22. Then piles 16a at outermost locations out of all the piles 16 are arranged so as to correspond to the location of the continuous underground wall 18, united with the continuous underground wall 18, and each have a diameter larger than the thickness of the continuous underground wall 18. Therefore the piles 16 bear the axial-force load of the building 10, and the continuous underground wall 18 mainly bears only horizontal load at the time of an earthquake. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite foundation of a pile and a continuous underground wall, and particularly to a composite foundation of a pile and a continuous underground wall in soft ground.

  Generally, foundation piles are used to receive the axial force of buildings.

  In soft ground, as a countermeasure when a horizontal load is applied in the event of an earthquake, the pile head is reinforced by increasing the pile diameter by a length equivalent to about 5 times the pile diameter from the top or winding a steel pipe. I am doing so.

  However, when building a high-rise building in a place where soft ground accumulates thickly, the response displacement value of the building increases only by increasing the pile head, so the pile foundation is surrounded by continuous underground wall piles. Things may be done.

  Thus, when using a continuous underground wall as a continuous underground wall pile, the thickness of the continuous underground wall pile is determined by the axial force load, and the thick continuous underground wall pile is made long to the support ground. The amount of excavation and concrete must be increased, which is very uneconomical, the construction period is lengthened, the amount of excavated soil is increased, and the construction soil is increased.

  In addition, if the supporting ground is deep, it is difficult to construct a thick continuous underground wall pile deeply and accurately.

Therefore, the technique which reinforces a building by making a continuous underground wall shallower than a support ground and making a pile integrated with this continuous underground wall into a support ground is proposed (refer to patent documents 1). ).
JP 2001-226987 A

  According to the technique described in Patent Document 1, it is economical in that the continuous underground wall can be shortened, and the construction period can be shortened.

  However, in the technique of Patent Document 1, since the relationship between the thickness of the continuous underground wall and the pile diameter is not specified, a device that does not cause an excessive burden on the continuous underground wall is required.

  For example, if the pile diameter must be increased to support the vertical load of the building, the continuous underground wall only has to bear the horizontal load during an earthquake, but the continuous underground wall Often the thickness must also be increased.

  Therefore, the amount of excavation is large, the amount of concrete used is also increased, the amount of excavated soil is increased, and the economy is not so high, which may be difficult to expect.

  Further, in this technology, since the ground configuration of soft ground is not taken into consideration, an efficient foundation structure corresponding to the ground configuration cannot be obtained.

  The object of the present invention is to consider the ground configuration in soft ground, efficiently support the building's axial load efficiently according to the ground configuration, reduce the response displacement during an earthquake and improve the comfortability. In addition, it is possible to reduce the upper frame by reducing the input to the superstructure, change the structure type, reduce the cross section of the pile and take measures against liquefaction. The purpose is to provide a composite foundation of piles and continuous underground walls that can be shortened.

To achieve the above object, the composite foundation of the pile and continuous underground wall of the present invention is
(1) It has a plurality of piles provided to reach the supporting ground, and a continuous underground wall provided integrally with the pile, and is constructed in a place where the soft ground is accumulated 30 m or more on the supporting ground. A composite foundation of piles and continuous underground walls,
The soft ground includes an intermediate layer that is lower in rigidity than the support ground and higher in rigidity than the upper layer,
The continuous underground wall is formed to a depth to the intermediate layer,
The pile is integrated with the continuous underground wall with the outermost pile located at the same position as the continuous underground wall,
The pile at the outermost peripheral position is a pile diameter larger than the thickness of the continuous underground wall,
Let the pile bear the axial load of the building,
The continuous underground wall mainly bears only a horizontal load during an earthquake.

  According to the present invention, in the soft ground, since the rigidity of the ground is small, it is easy to shake, the habitability is poor, and if the input and displacement to the foundation at this time are large, the foundation member may be damaged, but the soft ground part By forming the continuous underground wall of the base layer to a middle layer that is lower in rigidity than the supporting ground and higher in rigidity than the upper layer and increases the foundation rigidity in the soft part, it is possible to achieve earthquake resistance of the foundation and reduced input to the building Compared with the case where the continuous underground wall is formed up to the supporting ground, it is possible to perform an economical and efficient horizontal load treatment.

  Also, by forming the pile up to the supporting ground integrally with this continuous underground wall, it is possible to reliably support the vertical load of the building, and this pile has a pile diameter larger than the thickness of the continuous underground wall. By doing so, a larger vertical load can be supported, and the thickness of the continuous underground wall can be reduced by that much, and cost reduction steps and shortening of the construction period can be achieved.

(2) In the present invention, in (1),
The intermediate layer has a layer thickness that reaches the support ground at a predetermined depth from the ground surface.

  By adopting such a configuration, it is possible to perform a more economical and efficient horizontal load process by effectively using a rigid intermediate layer.

(3) In the present invention, in (2),
The pile at the outermost peripheral position is characterized in that the upper end extends to the upper end position of the continuous underground wall.

  By adopting such a configuration, when the intermediate layer has sufficient rigidity, by extending the top end of the pile to the top end of the continuous underground wall, the pile is supported by the vertical load, and the continuous underground wall is excessively vertical. It is possible to prevent the load supporting force from being applied.

(4) In the present invention, in (2),
The pile at the outermost peripheral position is characterized in that the upper end extends to a middle position of the continuous underground wall.

  By setting it as such a structure, when the rigidity of an intermediate | middle layer is smaller than the case of (3), a pile upper end can be made into the middle position of a continuous underground wall, and pile length can be shortened.

(5) In the present invention, in (2),
The pile at the outermost peripheral position is characterized in that the upper end is connected to the continuous underground wall at the lower end position of the continuous underground wall.

  By setting it as such a structure, when the rigidity of an intermediate | middle layer is smaller than the case of (4), a pile length can be shortened by setting a pile upper end to the lower end position of a continuous underground wall.

(6) In the present invention, in (1),
The intermediate layer has a layer thickness that does not reach the support ground at a predetermined depth from the ground surface,
The continuous underground wall is formed to a depth that reaches only the corner of the support ground, and the other part is formed to a depth to the intermediate layer,
The pile at the outermost peripheral position is provided except for a corner portion of the continuous underground wall.

  By adopting such a configuration, even when the intermediate layer has a layer thickness that does not reach the support ground at a predetermined depth from the ground surface, the corner portion of the continuous underground wall is extended to the support ground. , The rigidity against horizontal load is increased by the high rigidity at the corner, and the vertical load can be supported, and the pile surrounded by the continuous underground wall only bears the axial force, so the thickness of the pile is reduced Thus, the cost can be reduced.

(7) In the present invention, in any one of (1) to (6),
The intermediate layer is a clay soil having an N value of 10 or more or sandy soil having an N value of 20 or more, and is a ground having a shear wave velocity of 250 m / s or more.

  By setting it as such a structure, a horizontal displacement of a continuous underground wall can be made small by an intermediate | middle layer, and a certain amount of axial load can be borne.

(8) In the present invention, in any one of (1) to (7),
The depth to the intermediate layer is 10 m or more.

  By adopting such a configuration, it is possible to form a continuous underground wall at a predetermined depth and to apply a sufficient load of horizontal force.

(9) In the present invention, in any one of (1) to (8),
The intermediate layer has a thickness of 5 m or more.

  With such a configuration, the horizontal displacement of the continuous underground wall can be reduced by the intermediate layer, and a certain axial force load can be supported.

(10) In the present invention, in any one of (1) to (9),
A lower end of the continuous underground wall is embedded in the intermediate layer.

  By setting it as such a structure, the lower part of a continuous underground wall can be restrained to a rigid intermediate | middle layer, and it becomes possible to bear a horizontal load reliably.

  Embodiments of the present invention will be described below with reference to the drawings.

  1-6 is a figure which shows the composite foundation of the pile concerning one embodiment of this invention, and a continuous underground wall.

  FIG. 1 is a cross-sectional view showing a state in which a building is constructed on a composite foundation of piles and continuous underground walls according to this embodiment, and FIG. 2 is a cross-sectional view of the composite foundation in FIG.

  In this embodiment, the soft ground 12 is accumulated 30 m or more from the support ground 22, and the soft ground 12 has an intermediate layer 32 that is lower in rigidity than the support ground 22 and higher in rigidity than the upper layer 30. Is present.

  The intermediate layer 32 has a property as shown in FIG. 5 and a layer thickness reaching the support ground 22 at a predetermined depth, for example, 10 m or more from the ground surface 12a.

  The intermediate layer 32 is a clay soil having an N value of 10 or more or sandy soil having an N value of 20 or more, and has a shear wave velocity of 250 m / s or more.

  The layer thickness of the intermediate layer 32 is 5 m or more.

  The composite foundation 14 in the soft ground 12 having such an intermediate layer 32 allows a plurality of piles 16 that are bottom-pile piles to reach the support ground 22 from the foundation bottom of the building 10 and to be embedded, and on the outer periphery of the building 10. A continuous underground wall 18 is formed along the intermediate layer 32 along the depth.

  The lower end of the continuous underground wall 18 is in a state of being rooted in the upper part of the intermediate layer 32.

  In this way, by supporting the lower end of the continuous underground wall 18 on the intermediate layer 32, a certain amount of axial load is supported on the continuous underground wall 18, and the lower part of the building 10 continues to the intermediate layer 32. Since it is enclosed by 18 and supported by the intermediate layer 32, the response displacement at the time of an earthquake can be reduced and the comfortability can be improved.

  Further, the plurality of piles 16 are arranged at a predetermined interval in the lower part of the building 10, and the outermost piles 16a thereof are continuously arranged at the same position as the continuous underground wall 18 as shown in FIG. It is in a state integrated with the underground wall 18.

  Further, the plurality of piles 16 are all the same diameter, and the diameter is a pile diameter d larger than the thickness t of the continuous underground wall 18.

  This is because, since the thickness of the continuous underground wall 18 mainly handles horizontal force, the thickness of the pile 16 is generally about 120 cm as the thickness with sufficient horizontal rigidity and withstanding vertical load. This is because it is often made larger than that due to the bearing capacity.

  In this case, only the outermost pile 16a is set to a pile diameter d larger than the thickness t of the continuous underground wall 18, and the other inner pile 16b is set to a thinner pile diameter so as to reduce the cost. Good.

  Thus, by forming the outermost pile 16a integrally with the continuous underground wall 18, the vertical load of the building 10 can be reliably supported, and at least the outermost pile 16a is connected to the continuous underground wall. By making the pile diameter d larger than the thickness t, the larger vertical load can be supported, and the thickness t of the continuous underground wall 18 is reduced by that much, thereby achieving cost reduction and shortening the construction period. be able to.

  Further, as shown in FIG. 3, the amount of swallowing of the outermost pile 16 a with respect to the continuous underground wall 18 is changed according to the rigidity of the intermediate layer 32.

  For example, FIG. 1A shows a case where the intermediate layer 32 has sufficient rigidity. In this case, an excessive support force may be applied to the continuous underground wall 18, and therefore the upper end of the pile 16a is connected to the continuous ground. By extending to the upper end of the middle wall 18, the pile 16 a is supported with a vertical load, and an excessive vertical load supporting force is prevented from being applied to the continuous underground wall 18.

  In particular, when the thickness of the continuous underground wall 18 is reduced, it is important to adopt this structure in order to reduce the stress load in the vertical direction of the continuous underground wall 18.

  The construction in this case is a normal continuous underground wall in which the continuous underground wall 1 unit 20 is first constructed with a gap s between the diameters of the piles 16a, and then the piles 16a are constructed at the intervals s. It can be done with the construction procedure.

  Furthermore, when the axial diameter of the pile 16a is large, the axial strength of the continuous underground wall material is taken into consideration, and the lower end of the continuous underground wall 18 has an axial diameter d1 as shown in FIGS. The shaft diameter d2 that increases the diameter of the shaft and reduces the shaft load can be economical.

  FIG. 2B is a case where the rigidity of the intermediate layer 32 is smaller than in the case of FIG. 1B. In this case, the load applied to the continuous underground wall 18 is smaller than that in the above case. The length of the pile 16a is shortened to the middle position of the continuous underground wall 18.

  In this case, the pile 16a can be largely formed by expanding the head of the excavator.

  Further, (3) in the figure is a case where the rigidity of the intermediate layer 32 is further smaller than in the case of (2). In this case, the load on the continuous underground wall 18 is smaller than that in the above case. The upper end is extended to the lower end position of the continuous underground wall 18, and the length of the pile 16a is made shorter.

  In this case, the pile 16a can be formed by increasing the bottom of the continuous underground wall 18 and enlarging it.

  Next, the result of having examined the intermediate layer shown in FIG. 6 about the property at the time of an earthquake is shown.

  As shown in FIG. 1 (1), the ground structure is a shear wave velocity of 120 m / s at 0 to 20 m, 250 m / s at 20 m to 40 m, 300 m / s at 40 m to 50 m, 350 m / s at 60 m to 60 m, and 60 m. The depth is 450 m / s (equivalent to supporting ground).

  Here, as shown in Fig. 2 (2), two types of seismic waves, a notification wave and a coastal wave, which are often used in architectural design studies, are set up to image a high-rise building, and a primary natural period of 0.27 Hz (3 .8 seconds) dynamic response calculation was performed using a one-mass model.

  For the foundation, two types of foundations were installed: one with an outer peripheral pile for support, up to 20 m up to the middle layer, and a foundation with only a pile.

  When we compared the maximum response acceleration and maximum response displacement of the building, the maximum response acceleration and maximum response displacement of the foundation, which are important for seismic design, a pile that does not use a continuous underground wall by making a 20m continuous underground wall It is reduced by 50% depending on the response value with respect to the foundation, which is much better in all items than the pile foundation.

  FIG. 7 shows a composite foundation of piles and continuous underground walls according to another embodiment of the present invention.

  In this embodiment, the soft ground 12 has an intermediate layer 34 that is lower in rigidity than the support ground 22 and higher in rigidity than the upper layer 30, and has a predetermined depth from the ground surface 12 a, for example, 10 m or more, It has a layer thickness that does not reach the supporting ground 22, for example, 5 m or more.

  The intermediate layer 34 is a clay soil having an N value of 10 or more or a sandy soil having an N value of 20 or more, and has a ground having a shear wave velocity of 250 m / s or more.

  The composite foundation 14 provided on the soft ground 12 having such an intermediate layer 34 reaches an inner pile (not shown) from the foundation bottom of the building 10 to the support ground 22 among the plurality of piles 16 that are bottom-up piles. In addition, only the corner portion 36 of the continuous underground wall 18 is formed to a depth reaching the support ground 22, and the wall portion 38 between the other portion and the corner portion 36 is formed to the depth to the intermediate layer 34. ing.

  Further, the pile 16a at the outermost peripheral position is disposed at the same position as the continuous underground wall 18 except for the corner portion 36, and is provided integrally with the continuous underground wall 18.

  The lower end of the wall portion 38 of the continuous underground wall 18 is in a state of being embedded in the upper portion of the intermediate layer 34.

  In this way, the continuous underground wall 18 is formed to a depth reaching the support ground 22 at the corner portion 36, and the other portion is formed to a depth to the intermediate layer 34, so that the lower side of the intermediate layer 34 is soft. Even if the lower layer 40 continues, the corner portion 36 of the continuous underground wall 18 is extended to the supporting ground 22 to ensure sufficient rigidity against the horizontal load at the corner portion, and the axial load is substituted for the pile outside the corner. Can be omitted, and the pile outside the corner can be omitted, and since the inner pile bears only the axial force, it is possible to reduce the thickness of the pile and reduce the cost.

  In addition, the lower part of the building 10 is surrounded by the continuous underground wall 18 up to the intermediate layer 34, and the continuous underground wall 18 is supported by the intermediate layer 34. Can be improved.

  Other configurations and operations are the same as those in the above embodiment, and a description thereof will be omitted.

  The present invention is not limited to the above-described embodiment, and can be modified into various forms within the scope of the gist of the present invention.

  In the said embodiment, although the height of a building is 150 m, it is not limited to this example, The height of a building can be changed arbitrarily.

It is sectional drawing which shows the state which built the building on the composite foundation of the pile which concerns on one embodiment of this invention, and a continuous underground wall. It is a cross-sectional view of the composite foundation in FIG. It shows the swallowing amount of the pile with respect to the continuous underground wall according to the rigidity of the intermediate layer, (1) is a sectional view when the rigidity is the highest, (2) is a sectional view when the rigidity is lower than that, ( 3) is a cross-sectional view when rigidity is the lowest, (4) is a cross-sectional view with high rigidity and a large pile diameter, and (5) is a flat cross-sectional view with high rigidity and a large pile diameter. It is explanatory drawing which shows the construction state of a continuous underground wall and a pile. It is a figure which shows an example of the intermediate | middle layer of FIG. It shows the response calculation result at the time of the earthquake when it has the intermediate layer of FIG. 1, (1) is a diagram showing the ground conditions to be targeted, (2) is a diagram showing the ratio of the pile foundation of each part is there. It is sectional drawing which shows the composite foundation of the pile which concerns on other embodiment of this invention, and a continuous underground wall.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Building 12a Ground surface 14 Composite foundation 16 Pile 16a Outermost pile 18 Continuous underground wall 22 Support ground 30 Upper layer 32, 34 Middle layer 36 Corner part 40 Lower layer

Claims (10)

It has a plurality of piles that are provided to reach the supporting ground, and a continuous underground wall that is provided integrally with the pile, and is continuous with a pile that is constructed in a place where the soft ground has accumulated 30 m or more on the supporting ground. A complex foundation of underground walls,
The soft ground includes an intermediate layer that is lower in rigidity than the support ground and higher in rigidity than the upper layer,
The continuous underground wall is formed to a depth to the intermediate layer,
The pile is integrated with the continuous underground wall with the outermost pile located at the same position as the continuous underground wall,
The pile at the outermost peripheral position is a pile diameter larger than the thickness of the continuous underground wall,
Let the pile bear the axial load of the building,
A composite foundation of a pile and a continuous underground wall, wherein the continuous underground wall mainly bears only a horizontal load during an earthquake. In claim 1,
The intermediate layer has a layer thickness that reaches the support ground at a predetermined depth from the ground surface, and is a composite foundation of a pile and a continuous underground wall. In claim 2,
The pile at the outermost peripheral position has an upper end extending to an upper end position of a continuous underground wall. In claim 2,
The pile of the outermost periphery position is a composite foundation of a pile and a continuous underground wall, wherein an upper end extends to a midway position of the continuous underground wall. In claim 2,
The pile at the outermost periphery position is connected to the continuous underground wall at the lower end position of the continuous underground wall, and the pile and continuous underground wall composite foundation. In claim 1,
The intermediate layer has a layer thickness that does not reach the support ground at a predetermined depth from the ground surface,
The continuous underground wall is formed to a depth that reaches only the corner of the support ground, and the other part is formed to a depth to the intermediate layer,
The pile at the outermost peripheral position is provided except for a corner portion of the continuous underground wall, and is a composite foundation of a pile and a continuous underground wall. In any one of Claims 1-6,
The intermediate layer is a viscous foundation having an N value of 10 or more or a sandy soil having an N value of 20 or more, and is a ground having a shear wave velocity of 250 m / s or more. In any one of Claims 1-7,
The composite foundation of a pile and a continuous underground wall, characterized in that the depth to the intermediate layer is 10 m or more. In any one of Claims 1-8,
A composite foundation of a pile and a continuous underground wall, wherein the intermediate layer has a thickness of 5 m or more. In any one of Claims 1-9,
A composite foundation of a pile and a continuous underground wall, wherein a lower end of the continuous underground wall is embedded in the intermediate layer.

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