JP5896351B2 - Foundation structure and foundation construction method - Google Patents

Description

  The present invention relates to a foundation structure and a foundation construction method, and in particular, a foundation provided with a foundation main body connected to an upper structure of a building, and an underground wall provided to extend from the foundation main body into a lower ground. The present invention relates to a structure and a foundation construction method related to the foundation structure.

  Conventionally, as a foundation of a relatively small detached house as a building, a direct foundation placed directly on the ground such as a solid foundation, a cloth foundation, and an independent foundation has been generally used. In the case of such a direct foundation, if the ground on which it is placed is a soft ground or a ground that may cause liquefaction in the event of an earthquake, the ground itself loses its supporting force, and the foundation and the building are inclined. May end up. If the entire building including the foundation inclines in this way, the repair becomes large and the repair cost becomes large, so a foundation structure that can handle soft ground and liquefied ground has been proposed ( For example, see Patent Documents 1 and 2).

  The foundation structure described in Patent Document 1 is supported by being connected to a support body (pile part) that penetrates into the ground from the bottom plate of a building (structure), a buoyancy body provided on the support body, and the support body. An anchor body provided in the layer. In this foundation structure, even if the ground is liquefied and the bearing capacity is reduced, and groundwater rises due to excessive pore water pressure, the buoyancy due to this groundwater acts on the buoyant body to obtain the bearing capacity, and the anchor body tilts the building. It is a technology that tries to prevent.

  The foundation structure described in Patent Document 2 includes a foundation that supports a building, a sheet pile that surrounds the side of the foundation and penetrates into the ground, and a lightweight material that is provided in an area surrounded by the sheet pile below the foundation, Is provided. In this foundation structure, when the ground is liquefied and the bearing capacity is reduced, the foundation and the sheet pile are made to behave in an integrated manner, thereby suppressing the inclination of the foundation and the building. It is a technology that tries to secure the supporting force by acting on the foundation of the buoyancy of groundwater.

JP-A-6-240694 JP 2008-101379 A

  However, as in the foundation structure described in Patent Document 1, in order to construct a buoyancy body and an anchor body in the ground, the construction becomes very large, and an increase in cost is inevitable. It is difficult to apply to small-scale detached houses. Moreover, like the foundation structure described in patent document 2, when a foundation is enclosed with a sheet pile and a lightweight material is provided in the enclosed area, groundwater will always stay, and the retained groundwater will rot or May deteriorate. In addition, the buoyancy of the groundwater when the ground is liquefied and the buoyancy of the fluid in which the groundwater and sandy soil are turbid are not mechanically stable. In addition, since the buoyancy varies depending on the planar position of the building, it is difficult to effectively suppress the inclination of the entire building.

  Therefore, an object of this invention is to provide the foundation construction method and foundation construction method which can suppress the inclination of the whole building, even when the ground is liquefied.

In order to achieve the above object, the foundation structure according to claim 1 includes a foundation body connected to the upper structure of the building, and an underground wall provided to extend from the foundation body into the ground below. A foundation structure, wherein the foundation body includes a foundation rise provided along an outer periphery of the upper structure, and a foundation bottom plate integrally connected to a lower end portion of the foundation rise, the foundation body and the ground The underground wall is made of reinforced concrete wall or soil cement wall, and the first wall portion along the first direction in two horizontal directions orthogonal to each other, and the second wall in the second direction. has a second wall portion along the horizontal cross section formed by said first and second wall portion is a cruciform opening cross-section integrally and continuously, and, said first and second The upper part of the wall is connected to the foundation bottom plate, and the underground wall and the foundation body are integrated. The aquifer comprises a first permeable layer is provided along the lower surface of the base bottom plate, anda second permeable layer provided along the outer surface of said base rising, said first and second Each of the water permeable layers is formed by laminating a plurality of sandbag materials, and the sandbag materials are configured by packing granular materials in bags of a predetermined size having water permeability.

The foundation structure according to claim 2 is the foundation structure according to claim 1, wherein the underground wall has the same length as the entire width along the first direction of the foundation bottom slab. A wall portion is formed, and the second wall portion is formed to have substantially the same length as the entire width along the second direction of the foundation bottom plate .

  The foundation structure according to claim 3 is the foundation structure according to claim 1 or 2, wherein a weight ratio of the upper structure, the foundation body, and the underground wall is 1: 1: 1.5. It is characterized by being set to about 2.0.

  The foundation structure according to claim 4 is the foundation structure according to any one of claims 1 to 3, wherein the permeable layer is provided between a side surface of the underground wall and the ground, and the sandbag material. The third water permeable layer is connected to the first water permeable layer.

  The foundation construction method according to claim 5 is a foundation construction method according to any one of claims 1 to 4, wherein the ground is excavated according to the dimensions of the underground wall. And constructing the underground wall, providing a connecting material for connecting the underground wall and the foundation body, and laminating the plurality of sandbag materials on the ground in the area where the foundation bottom plate of the foundation body is constructed. Forming the first water permeable layer, constructing the foundation bottom plate above the first water permeable layer, forming the foundation rising integrally with the foundation bottom plate, and connecting the connecting member to The second water-permeable layer is formed by stacking the plurality of sandbag materials along the outer surface of the foundation rising.

  The foundation construction method according to claim 6 is the foundation construction method according to claim 5, wherein after the underground wall is constructed, the plurality of foundations are provided between a side surface of the underground wall and the excavated ground. A third water-permeable layer is formed by laminating the sandbag materials.

  According to the invention described in claim 1, by providing an underground wall extending from the foundation body into the ground, the ground is liquefied during an earthquake, and even when the building is shaken by the seismic force, After the earthquake, the weight of the underground wall acts as a counterweight, so that the inclination of the entire building can be suppressed. In addition, since the horizontal section of the underground wall is formed as an open section, the underground wall and the liquefied ground do not behave integrally, that is, the underground wall resists the fluidized ground. It becomes a plate (braking plate) and can be expected to have a vibration control effect that suppresses the shaking of the building. Furthermore, since the underground wall has an open cross section, the groundwater does not stay and can be prevented from decaying or deteriorating.

  Furthermore, since the first and second permeable layers were constructed by laminating a plurality of sandbag materials, even when excess pore water pressure was generated due to liquefaction of the ground during an earthquake, the groundwater level was increased. It can be drained from the permeable layer to the ground. Therefore, it is possible to prevent excessive buoyancy due to groundwater from acting on the foundation bottom slab, and to suppress the inclination of the building due to uneven buoyancy. In addition, a sandbag material is configured by packing a granular material in a bag having water permeability, and the first and second water permeable layers are configured by stacking a plurality of such sandbag materials. Even if it is buried with earth and sand, water permeability can be ensured by the bag of sandbag material and the internal granular material, and the groundwater can be drained more reliably. Note that the sandbag material is not limited to soil, sand, crushed stone, etc., but may be glass pieces, resin pieces, etc. Those excellent in loadability are preferred.

In addition , the underground wall is made of reinforced concrete wall or soil cement wall, and its horizontal section is symmetrical with respect to two vertical planes, so that the underground wall acts as a braking plate for fluidized ground. In doing so, the braking force can be exerted in a balanced manner in the plane direction of the entire building. Here, the sectional shape of the underground wall formed in plane symmetry with respect to the vertical plane along the horizontal two directions, cross can be exemplified. Also, for example, a shape having rib-like portions protruding from the tip and middle portions of the first and second wall portions intersecting in a cruciform shape, such as a square shape, with respect to two vertical surfaces Even if the horizontal cross section is not completely plane symmetric, the horizontal cross section constituted by the first and second wall portions, which are the main portions of the underground wall, may be formed plane symmetric.

  According to the invention described in claim 3, the center of gravity of the entire building is lowered by setting the weight ratio of the superstructure, the foundation main body, and the underground wall to about 1: 1: 1.5 to 2.0. It is possible to reduce the shaking of the building at the time of an earthquake and to more effectively suppress the inclination of the entire building. As a matter of course, the weight ratio may include some errors, and an error of ± 20% of the ratio is within the scope of the present invention, and is set within ± 10% of the ratio. Preferably it is.

  According to the invention described in claim 4, by providing the third permeable layer between the side surface of the underground wall and the ground, and connecting the third permeable layer to the first permeable layer, The groundwater at the side surface position can be reliably drained to the ground through the third permeable layer, the first permeable layer, and the second permeable layer. Therefore, the inclination of the building can be suppressed well and reliably without causing excessive and non-uniform buoyancy to act on the foundation bottom plate.

  According to the invention described in claim 5, the first permeable layer is formed after the underground wall is constructed, and then the second permeable layer is formed after the foundation bottom plate and the foundation rising are formed. In addition, the underground wall and the foundation body can be reliably connected and integrated with a connecting material, and the sandbag material can be easily and reliably stacked in the first and second permeable layers. Can be improved.

  According to the invention described in claim 6, when the third permeable layer is formed after the construction of the underground wall, the sandbag material is thrown from the ground surface between the side surface of the underground wall and the excavated ground and laminated. Such a construction procedure can be adopted, and the third water permeable layer can be easily formed without using heavy machinery or the like. Therefore, since the third permeable layer can be formed without excavating the ground over a wide area, it is only necessary to excavate a limited area around the underground wall, so the amount of soil discharged can be reduced, and the construction labor and construction can be reduced. Cost can be reduced.

It is a perspective view which shows the foundation structure of the building which concerns on one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the lower part of the said building. It is the cross-sectional view which looked up at the foundation part of the building from the lower part. It is a perspective view which shows the construction procedure which builds the foundation of the said building. It is a perspective view which shows the construction procedure of the said foundation following FIG. It is a perspective view which shows the construction procedure of the said foundation following FIG. It is a perspective view which shows the construction procedure of the said foundation following FIG. It is a perspective view which shows the construction procedure of the said foundation following FIG. It is a perspective view which shows the construction procedure of the said foundation following FIG. It is a longitudinal cross-sectional view which shows the modification of the said foundation structure .

  Hereinafter, the basic structure concerning one Embodiment of this invention is demonstrated based on FIGS. 1-3. The foundation structure according to the present embodiment supports a building body 2 as an upper structure of the building 1, and the building 1 is used for a detached house, an apartment, or the like. The building body 2 is a relatively small and light 2-3-story building such as a wooden structure or a lightweight steel structure, and has a rectangular shape along the X and Y directions which are two horizontal directions as shown in FIG. It has a well-shaped planar shape. Here, a rectangular area L1 indicated by a one-dot chain line in FIG. 3 indicates a construction area in the site for constructing the building 1, and a rectangular area L2 indicated by a two-dot chain line indicates a planar shape of the building body 2. . The building 1 is constructed on the ground G, and this ground G is excavated from the ground surface GL downward in the Z direction, which is the vertical direction, to construct a foundation body 3, an underground wall 4 and a permeable layer 5 described later. .

  The foundation body 3 includes a foundation rise 31 provided along the outer periphery of the building body 2, a foundation bottom plate 32 that is integrally connected to a lower end portion of the foundation rise 31 and extends in a horizontal plane, and faces above the foundation bottom plate 32. And a foundation slab 33 connected to the foundation rising 31. A foundation pit for arranging equipment piping and the like is formed between the foundation bottom slab 32 and the foundation slab 33, and a foundation beam 34 for connecting the foundation bottom slab 32 and the foundation slab 33 to an appropriate position in the foundation pit. Is provided. The depth of penetration of the foundation main body 3, that is, the distance from the ground surface GL to the lower surface of the foundation bottom slab 32 is set to about 800 mm to 1 m, for example. Moreover, the thickness dimension of the foundation rising 31 and the foundation bottom slab 32 is about 200 mm, for example, and the thickness dimension of the foundation slab 33 is set to about 120 mm to 150 mm, for example. The foundation rising 31 protrudes upward from the ground surface GL by about 500 mm to 800 mm, and the base of the building body 2 is connected to the upper end of the foundation rising 31 via an anchor bolt and a joint hardware. The depth of penetration of the foundation body 3 (distance from the ground surface GL to the bottom surface of the foundation bottom slab 32) is, as will be described later, together with buoyancy acting on the bottom surface of the foundation bottom slab 32 due to groundwater pressure generated during liquefaction. Considering the weight ratio of the main body 2, the foundation main body 3, and the underground wall 4, if the buoyancy is predicted to be large, the depth of penetration is reduced, and if the buoyancy is small, the depth of penetration is It is possible to set appropriately such as deepening the depth.

  The underground wall 4 is a reinforced concrete wall, extends from the lower surface of the foundation bottom slab 32 into the ground G below, and is connected to the foundation body 3. Specifically, a reinforcing bar R (see FIG. 6), which will be described later, is provided extending upward from the inside of the underground wall 4, and this reinforcing bar R is fixed inside the foundation bottom slab 32 and the foundation beam 34. Yes. The underground wall 4 is not limited to reinforced concrete, but may be a soil cement wall (SMW) constructed by stirring and mixing the soil and cement of the ground G using an excavating stirrer such as an auger. . Even when the underground wall 4 is an SMW, the underground wall 4 and the foundation main body 3 can be connected by providing a connecting material such as a reinforcing bar or an anchor between the inside of the SMW and the inside of the foundation main body 3. The underground wall 4 has a first wall portion 41 along the X direction (first direction) and a second wall portion 42 along the Y direction (second direction), and has a substantially cross-shaped plane. In other words, the horizontal cross-sectional shape of the underground wall 4 is an open cross-section opened to the ground G on the side. Further, the underground wall 4 is formed to have a horizontal section that is plane-symmetric with respect to each of the XZ plane and the YZ plane, which are vertical planes along two horizontal directions (X direction and Y direction). ing.

  The first wall portion 41 and the second wall portion 42 are each formed with a wall thickness of about 200 mm and a depth of 4 to 8 m from the foundation bottom plate 32 to the lower edge of the wall. The first wall portion 41 has a horizontal length dimension substantially the same as the X-direction length of the building body 2, and the second wall portion 42 has a horizontal length dimension substantially the same as the Y-direction length of the building body 2. Is formed. The total weight of the underground wall 4 including the first wall portion 41 and the second wall portion 42 is about 1.5 to 2.0 times the weight of the building body 2, and the foundation body 3 The weight is set to about 1.5 to 2.0 times the weight. That is, the wall thickness of the underground wall 4 is set so that the weight ratio of the building body 2, the foundation body 3, and the underground wall 4 that is the upper structure is about 1: 1: 1.5 to 2.0. The depth dimension and the horizontal length dimension are set. In addition, when the underground wall 4 is a soil cement wall, the wall thickness is about 400 mm to 600 mm, and the specific gravity is different from that of the reinforced concrete wall. Therefore, the depth dimension and the horizontal length dimension are appropriately adjusted. What is necessary is just to set a weight.

  The water permeable layer 5 is formed by laminating a plurality of sandbag materials 5A. As the sandbag material 5A, for example, a bag made of a woven cloth having water permeability such as polyethylene is used as a glass piece or Those filled with granular materials such as glass particles can be used. As such a sandbag material 5A, if the dimension is about 400 mm × 400 mm × 100 mm and the weight is about 5 kg to 10 kg, it is preferable in terms of workability related to conveyance and lamination. In addition, since the sandbag material 5A allows both the bag and the granular material to pass water, the sandbag material 5A itself has water permeability, and an appropriate gap is formed between the stacked sandbag materials 5A. The water permeability can be obtained.

  Such a water permeable layer 5 is provided between the foundation main body 2 and the ground G. Specifically, the first water permeable layer 51 provided along the lower surface of the foundation bottom slab 32 and the outer surface of the foundation rising 31. And a second water permeable layer 52 provided along. The 1st water permeable layer 51 is provided in the range of the rectangular area L2 according to the planar shape of the building main body 2, or the range of the rectangular area L1 which is a construction area which excavates the ground G, The underground wall 4 is included in the said range. The sandbag material 5A is arranged and stacked in the removed portion without gaps. The second water permeable layer 52 was laminated from the depth continuous to the first water permeable layer 51 to the vicinity of the ground surface GL in a range excluding the rectangular region L2 from the rectangular region L1, that is, in an annular range along the outer periphery of the base body 3. It is comprised by the sandbag material 5A.

  The construction procedure of the foundation structure as described above will be described with reference to FIGS. First, as shown in FIG. 4, in a rectangular region L <b> 1 that is a construction area in the site, the ground G is excavated into a plane cross shape according to the shape of the underground wall 4 to form a excavation groove D. This excavation is performed, for example, using a heavy machine such as a small backhoe, and in some cases, the excavation may be performed manually. Next, as shown in FIG. 5, the formwork K is built in the excavation groove D, and concrete is placed after reinforcing bars are arranged inside the formwork K. The underground wall 4 made of reinforced concrete thus constructed is a three-dimensional wall having an integral structure with a horizontal cross section as shown in FIG. Further, a reinforcing bar R as a connecting member is projected upward at the upper end of the underground wall 4, and the underground wall 4 and the foundation main body 3 are connected via the reinforcing bar R.

  Next, as shown in FIG. 7, the sandbag material 5 </ b> A is arranged and stacked in the range of the rectangular region L <b> 1 to form the first water permeable layer 51. This stacking operation may be performed manually, or may be performed using an appropriate apparatus or heavy equipment. Next, as shown in FIG. 8, the foundation body 2 is constructed on the upper side of the first water permeable layer 51. At this time, as a method for constructing the foundation bottom plate 32, concrete may be directly placed on the upper side of the first permeable layer 51, or crushed stones, lightweight aggregates, and the like are laid on the upper side of the first permeable layer 51. Concrete may be placed on the wall. Moreover, the underground wall 4 and the foundation main body 3 are integrated by fixing the reinforcing bar R projected from the underground wall 4 to the concrete inside of the foundation bottom plate 32 and the foundation beam 34. Next, as shown in FIG. 9, the sandbag material 5 </ b> A is laminated on the upper side of the first permeable layer 51 along the outer surface of the foundation rising 31 of the foundation body 3 in the rectangular region L <b> 1 to form the second permeable layer 52. Form. When the construction of the foundation structure is completed as described above, the building body 2 is constructed on the foundation rising 31 and the foundation beam 34 to complete the building 1.

  According to the present embodiment, since the underground wall 4 is formed integrally with the foundation main body 3, even if the ground G is liquefied and the supporting force is reduced during an earthquake, the underground wall 4 is countered. Since the underground wall 4 acts as a braking plate for the fluidized ground G as well as acting as a weight, the shaking of the building 1 is suppressed, and the building 1 returns to the initial state after the earthquake and the entire Tilt can be suppressed. In addition, since the underground wall 4 is formed in an open cross section and the ground G is not surrounded by the underground wall 4, the ground water does not stay in the ground G below the building 1 and prevents corruption and deterioration of the ground water. can do. Furthermore, since the permeable layer 5 is provided between the foundation body 3 and the ground G, groundwater generated by liquefaction can be drained from the permeable layer 5 to the ground, and excessive buoyancy due to the groundwater is caused by the foundation bottom plate 32. It is possible to prevent the building 1 from tilting due to non-uniform buoyancy. Moreover, since the water permeable layer 5 is configured by laminating sandbag materials 5A packed with granular materials in a bag having water permeability, groundwater is more reliably secured by the gap between the sandbag materials 5A and the water permeability of the sandbag material 5A itself. Can be drained.

  In addition, embodiment mentioned above only showed the typical form of this invention, and this invention is not limited to embodiment. That is, various modifications can be made without departing from the scope of the present invention.

  For example, in the said embodiment, although the water permeable layer 5 was comprised by the 1st water permeable layer 51 and the 2nd water permeable layer 52, in addition to the 1st water permeable layer 51 and the 2nd water permeable layer 52, as shown in FIG. The water permeable layer 5 may include the third water permeable layer 53. The third water permeable layer 53 is configured by laminating a sandbag material 5 </ b> A between the side surface of the underground wall 4 and the ground G, and an upper portion thereof is connected to the first water permeable layer 51. Therefore, groundwater generated at a deep position in the ground G is also permeated upward from the third permeable layer 53 and can be drained to the ground via the first permeable layer 51 and the second permeable layer 52. The third water permeable layer 53 is formed by constructing the underground wall 4 as described above and then introducing the sandbag material 5A from the ground surface GL into the excavation groove D along the underground wall 4. . The third water permeable layer 53 is not limited to being provided along the entire length in the depth direction of the underground wall 4, and may be provided from the first water permeable layer 51 to a predetermined depth.

1 Building 2 Building body (superstructure)
DESCRIPTION OF SYMBOLS 3 Base body 4 Underground wall 5 Water permeable layer 5A Sandbag material 31 Foundation rise 32 Foundation bottom plate 41 First wall part 42 Second wall part 51 First permeable layer 52 Second permeable layer 53 Third permeable layer

Claims (6)

A foundation structure comprising a foundation body connected to the upper structure of the building, and an underground wall provided extending from the foundation body into the ground below,
The foundation main body has a foundation rising provided along the outer periphery of the upper structure, and a foundation bottom plate integrally connected to a lower end portion of the foundation rising, and a water permeable layer between the foundation main body and the ground. Is provided,
The underground wall is a reinforced concrete wall or a soil cement wall, and has a first wall portion along a first direction and a second wall portion along a second direction in two horizontal directions orthogonal to each other. And the horizontal cross section formed by the first and second wall portions is an integrally continuous cross-shaped open cross section, and the upper portions of the first and second wall portions are connected to the foundation bottom plate. And the underground wall and the foundation body are integrated,
The water permeable layer includes a first water permeable layer provided along a lower surface of the foundation bottom plate, and a second water permeable layer provided along an outer surface of the foundation rising, and the first and second water permeable layers. Each layer is composed of multiple sandbags,
The said sandbag material is a foundation structure characterized by packing granular material in the bag of the predetermined dimension which has water permeability. The underground wall has substantially the same length as the entire width along the first direction of the foundation bottom slab, and the first wall portion is formed, and substantially the same length as the entire width along the second direction of the foundation bottom slab. The foundation structure according to claim 1, wherein the second wall portion is formed with a thickness .   The weight ratio of the upper structure, the base body, and the underground wall is set to about 1: 1: 1.5 to 2.0. Foundation structure.   The water permeable layer is provided between a side surface of the underground wall and the ground, and has a third water permeable layer in which the sandbag material is laminated, and the third water permeable layer is connected to the first water permeable layer. The foundation structure according to any one of claims 1 to 3. It is the construction method of the foundation which concerns on the foundation structure as described in any one of Claims 1-4,
Excavating the ground according to the size of the underground wall, constructing the underground wall, and providing a connecting material for connecting the underground wall and the foundation body,
The first water permeable layer is formed by laminating the plurality of sandbag materials on the ground in the area where the foundation bottom plate of the foundation body is constructed,
Constructing the foundation bottom plate on the upper side of the first water permeable layer, forming the foundation rising integrally with the foundation bottom plate and connecting the connecting material to construct the foundation body;
A foundation construction method, wherein the second water permeable layer is formed by laminating the plurality of sandbag materials along the outer surface of the foundation rising.   6. The third water permeable layer is formed by laminating the plurality of sandbag materials between a side surface of the underground wall and the excavated ground after the underground wall is constructed. How to build the foundation of

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