building

Abstract

This avoids problems caused by structural members left in place to support the foundation. [Solution] When constructing a building consisting of a foundation 1 and a building 2, retaining piles 41 and sheet piles 42 are installed on the side walls of a recessed space 9 formed by excavating the area to be occupied by the foundation 1 to retain the earth. The retaining piles 41 are made of wood, such as logs, and are driven in so that their tips reach a position lower than the bottom of the recessed space 9. The sheet piles 42 are also used as formwork during the construction of the foundation 1 and remain in the ground along with the retaining piles 41 even after the building is completed. The retaining piles 41 are reinforced by beam members 51A, 51B, 52A, and 52B made of buried logs, forming an underground raft 50. Crushed stone is filled behind the sheet piles 42 to form a backfill crushed stone layer 421.

Description

Technical Field

[0001] The invention of this application relates to inventions regarding various buildings.

Background Art

[0002] In recent years, with the progress of urbanization, there have been an increasing number of cases of constructing residential and other buildings on sites with soft ground having weak ground bearing capacity. During construction, the ground bearing capacity of the ground at the site is measured through boring surveys and the like, and ground improvement work is carried out according to the results. After the ground improvement work, the foundation is constructed, and then the building part is constructed on top of it. As ground improvement work, the pile method, the ground replacement method, etc. are known. The pile method involves driving piles down to hard ground such as diluvial layers, and is suitable from the perspective of preventing building settlement, but it is a large-scale and expensive construction method. Moreover, during a major earthquake, the vibration of the earthquake is transmitted to the building by the piles, and there have been cases where it has caused the building to collapse. This problem is described in detail in Patent Document 1. In addition to anchor piles, friction piles are also known for the pile method, but they are similarly costly and have the problem of transmitting vibration during a major earthquake.

[0003] The ground improvement by the ground replacement method is a construction method that does not rely on piles and can be constructed relatively inexpensively. Among these, the construction methods disclosed in Patent Document 2 and Patent Document 3 are construction methods that perform ground replacement by laying resin blocks having openings as structural materials, and have the advantage that there is no problem even if it rains during construction compared to styrofoam ground replacement materials. Moreover, since groundwater can be stored in the resin blocks, there are merits such as the effect of suppressing rainwater runoff during heavy rain or the water stored inside exhibiting a seismic isolation effect during an earthquake. For this reason, the ground replacement method using resin blocks that are not made of styrofoam is being widely adopted. In addition, this type of ground reinforcement technology can be said to be a method of burying members that support the foundation underground.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Patent No. 7454897 [Patent Document 2] Patent No. 5938454 [Patent Document 3] Patent No. 4210312 Publication [Overview of the project] [Problems that the invention aims to solve]

[0005] As described above, the ground replacement method using resin blocks has many advantages and has come to be widely adopted. However, through field surveys and research, the inventor has found that there are phenomena that can reduce the reliability of the ground replacement method using resin blocks. This point will be explained below. Ground improvement methods using resin blocks are carried out prior to foundation construction. Excavation work is performed on the site, digging an area slightly wider than the area where the foundation will be constructed (horizontal area). After that, groundwork such as compaction and laying of crushed stone is carried out at the bottom of the excavated recess (hereinafter referred to as the excavated recess), and then it is covered with a permeable sheet. Numerous resin blocks are laid on top of the sheet in an orderly fashion, forming a resin block layer. The formed resin block layer has sufficient strength to support the load of the foundation and building constructed above it, while being far lighter than the soil of the site, thus achieving ground replacement and providing a settlement prevention effect.

[0006] When forming such a resin block layer (ground replacement layer), retaining walls are formed on the side walls of the excavation recess. Conventionally, retaining walls are formed by driving steel retaining piles, such as H-beams, into the ground at equal intervals and attaching sheet piles between the retaining piles to form bridges. Such retaining walls prevent the walls of the excavation recess from collapsing during the formation of the ground replacement layer and the construction of the foundation.

[0007] Even in construction sites where foundations are being built while retaining the earthworks, the effects of labor shortages and rising material costs are clearly evident. As the workforce ages, transporting and driving heavy steel retaining piles, such as H-beams, has become an increasingly strenuous task. As a result, it is becoming more common to have inexperienced young workers or foreign workers with limited knowledge perform this task instead of skilled older workers.

[0008] However, when inexperienced workers are in charge of the work, unexpected accidents can occur due to insufficient construction of the retaining wall. Specifically, when excavation is carried out to create a recess, the recess becomes a space without soil pressure, which disrupts the balance of soil pressure with the adjacent property. Therefore, it is necessary to ensure sufficient retaining wall strength to adequately counteract the soil pressure of the adjacent land, and for this reason, sufficient backfilling and compaction are required on the back side of the sheet piles (opposite the foundation). However, if inexperienced workers neglect this, accidents may occur such as the retaining wall piles tilting or the soil pressure from the adjacent land being drawn in, causing ground subsidence on the adjacent land. In addition, crushed stone is sometimes filled on the back side of the retaining wall to create a pathway for water when the groundwater level rises, but if workers neglect or do not do this adequately, accidents may occur where groundwater rises to unexpected places and overflows during heavy rains.

[0009] Furthermore, while inexpensive foreign-made steel retaining piles, such as H-beams, are flooding the market, some of them are smaller in size or thinner than standard ones. In order to reduce construction costs, using such inexpensive foreign-made H-beams as retaining piles can result in the inability to achieve the strength that the architect envisioned in the retaining wall design, leading to accidents such as the retaining piles tilting or parts of the retaining wall collapsing. The collapse of the retaining wall can significantly delay the foundation work schedule and often reduces the bearing capacity of the adjacent land, potentially leading to serious accidents such as houses tilting (differential settlement of the ground) on the adjacent property.

[0010] Furthermore, aside from labor shortages and rising material costs, problems can arise that stem from the steel retaining piles themselves, such as H-beams. When retaining piles are driven into the ground, consolidation occurs in the voids around the piles. In the case of steel retaining piles like H-beams, the load is large, and the consolidation disrupts the balance of stress in the ground. As a result, partial settlement may occur even while the ground is being replaced with a resin block layer. In such cases, the settlement is often only a few centimeters to about 10 centimeters and rarely becomes a major problem, but it can reduce the reliability of the resin block layer ground replacement method.

[0011] The above problem becomes particularly serious when retaining piles or sheet piles are left in place even after the construction of a building is completed. In urban areas where building codes (floor area ratio, building coverage ratio) have been relaxed, relatively heavy buildings (such as mid-rise apartment buildings) are often constructed on small plots of land. In this case, the foundation is relatively large, often involving a pit structure, requiring deep excavation and the construction of retaining walls. However, because the plots are small, the distance to neighboring properties is short, and heavy machinery cannot be brought in, which may result in the retaining walls remaining in place even after the building is completed.

[0012] While sheet piles rarely pose a problem among the retaining walls that remain, steel retaining piles such as H-beams can be a factor in ground subsidence over time. In other words, heavy retaining piles can gradually sink, and as a result, the surrounding ground can be dragged down. Urban areas where building codes have been relaxed are often located in alluvial plains with high groundwater levels, making the problem even more serious. Specifically, steel retaining piles, such as H-beams, do not conform well to alluvial clay layers (i.e., have low frictional resistance) and are prone to settling due to their own weight. In addition to the problem of worsening the balance of groundwater distribution due to settlement, there is also the problem of corrosion due to constant exposure to groundwater. When retaining piles deteriorate due to corrosion, voids are created, making the ground even more unstable.

[0013] The present invention was made based on this awareness of the problem, and its objective is to avoid problems caused by the remaining members that support the foundation. [Means for solving the problem]

[0014] To solve the above problems, this specification discloses inventions for construction methods and buildings. The disclosed construction method is a construction method for constructing a building consisting of a foundation and a building constructed on the foundation. This construction method includes an excavation step of excavating an area on the site where the building will be constructed, including the horizontal area to be occupied by the foundation, to form a recessed space relative to the ground surface; a retaining step of reinforcing the side walls of the recessed space formed in the excavation step by installing sheet piles to prevent the side walls from collapsing; a foundation construction step of constructing the foundation in the recessed space formed in the excavation step; and a building construction step of constructing the building on the foundation constructed in the foundation construction step. The earth retention process is, A retaining pile driving process in which wooden retaining piles are driven into the ground so that their tips reach a position lower than the bottom surface of the recessed space formed or created in the excavation process, and a sheet pile installation process in which multiple sheet piles are installed. It includes. The retaining pile driving process involves driving multiple retaining piles at intervals along the edge of the bottom surface of the recessed space formed or created during the excavation process. When the central side of the recessed space is considered the inside and the opposite side the outside, the sheet pile installation process is the process of fixing each sheet pile to the retaining pile so as to bridge the gap between adjacent retaining piles, and is the process of fixing each sheet pile to the inside of the retaining pile. The foundation construction process involves pouring concrete into the sheet piles that were installed during the sheet pile installation process, using them as part of the formwork, and then allowing the concrete to cure to construct the foundation. Furthermore, this construction method involves leaving each retaining pile driven in during the pile driving process and each sheet pile installed during the sheet pile installation process as wooden structures supporting the foundation, remaining in the ground of the site even after the building is completed. Furthermore, this specification discloses a construction method relating to another invention. This construction method relating to another invention is a construction method for constructing a building consisting of a foundation and a building constructed on the foundation, and includes: an excavation step of excavating an area on the site where the building will be constructed, including the horizontal area to be occupied by the foundation, to form a recessed space relative to the ground surface; a retaining step of reinforcing the side walls of the recessed space formed in the excavation step by providing sheet piles to prevent the side walls from collapsing; a foundation construction step of constructing the foundation in the recessed space formed in the excavation step; and a building construction step of constructing the building on the foundation constructed in the foundation construction step. The earth retention process is, A retaining pile driving process involves driving wooden retaining piles into the ground so that their tips reach a position lower than the bottom surface of the recessed space formed or created during the excavation process, The sheet pile installation process involves installing multiple sheet piles. It includes. The retaining pile driving process involves driving multiple retaining piles at intervals along the edge of the bottom surface of the recessed space formed or created during the excavation process. When the central side of the recessed space is considered the inside and the opposite side the outside, the sheet pile installation process is the process of fixing each sheet pile to the retaining pile so as to bridge the gap between adjacent retaining piles, and is the process of fixing each sheet pile to the inside of the retaining pile. This method involves leaving each retaining pile driven in during the pile driving process and each sheet pile installed during the sheet pile installation process as wooden structures supporting the foundation, remaining in the ground of the site even after the building is completed. This construction method involves filling the space between the remaining sheet piles and the foundation with crushed stone or broken rock. The construction methods according to each of the above inventions may have a configuration in which the inner surface of the retaining pile is cut to be flat, and the sheet pile installation process is a process of fixing the sheet pile to this cut surface. Furthermore, in order to solve the above problems, an invention for a building is disclosed in this specification. The building according to the disclosed invention is a building consisting of a foundation and a building constructed on the foundation. This building has a wooden structure buried to support the foundation. The wooden structure consists of sheet piles and retaining piles. The sheet piles are provided along the outer surface of the foundation and cover the outer surface. The retaining piles are provided on the surface opposite to the foundation of the sheet piles, and the sheet piles are fixed to the retaining piles. Also, the sheet piles extend horizontally, and a plurality of retaining piles are provided side by side in the direction in which the sheet piles extend. And the tip of each retaining pile reaches a position deeper than the bottom of the foundation. Also, to solve the above problems, this building each retaining pile has a cut surface that is flatly cut on the side of the foundation, and the sheet pile is fixed to the cut surface of each retaining pile may have such a configuration. Also, to solve the above problems, this building Among the retaining piles, between two retaining piles facing each other across the foundation, a wooden beam is provided on the lower side of the foundation and serves as a strut beam for the two retaining piles. It may have such a configuration. Also, to solve the above problems, this building The strut beam is provided between two retaining piles facing each other in the first direction and is also provided between two retaining piles facing each other in the second direction orthogonal to the first direction, and these strut beams are assembled in a grid pattern under the foundation. may have such a configuration. Also, to solve the above problems, a building according to another invention is disclosed in this specification. The building according to another invention is a building composed of a foundation and a building constructed on the foundation, and a wooden structure for supporting the foundation is buried. The wooden structure is a ground raft provided under the foundation. And in this building according to another invention, the ground raft is composed of logs assembled in a grid pattern. Also, to solve the above problems, the building according to another invention In an underground raft made of logs arranged in a grid pattern, intersecting logs are connected to each other, and the inside of the grid is filled with crushed stone or broken rock. It can have this kind of structure. Furthermore, each of these disclosed inventions shares a common feature: a structure in which a wooden structure supporting the foundation is embedded. [Effects of the Invention]

[0015] As explained below, according to the construction methods or buildings according to the disclosed inventions, when forming retaining walls, wooden retaining piles are used instead of steel piles such as H-beams. This reduces the load on the ground, and minimizes the impairment of the effectiveness of ground replacement materials such as resin blocks when performing ground replacement. Furthermore, wooden retaining piles are less expensive than steel retaining piles such as H-beams, offering a cost advantage. In addition, the man-hours required for removing sheet piles and retaining piles are reduced, providing another cost advantage and shortening the construction period. In this configuration, the inner surface of the retaining pile is cut to a flat surface, and by fixing the sheet pile to this cut surface, it becomes easier to ensure sufficient fixing strength for the sheet pile. Furthermore, in the building according to the disclosed invention, if a configuration is provided in which parallel directional beam members are installed, the retaining piles are reinforced, thereby enhancing the effect of preventing the retaining piles from collapsing during foundation construction, and providing the effect of stabilizing the retaining piles in the ground after the completion of the building. Furthermore, in the building according to the disclosed invention, if a support beam is provided, the retaining piles are reinforced, thereby enhancing the effect of preventing the retaining piles from collapsing during foundation construction, and providing the effect of stabilizing the retaining piles in the ground after the completion of the building. Furthermore, the configuration in which the support beams are assembled in a grid pattern enhances the effect of preventing the collapse of the retaining wall during foundation construction, and after the completion of the building, it provides the effect of stabilizing the retaining wall piles in the ground. In addition, the grid-like support beams act as underground rafts, exhibiting ground replacement, seismic isolation, and ground preservation functions. Furthermore, according to another disclosed invention, the building structure provides the effects of ground replacement, seismic isolation, and ground preservation functions through a grid-like underground raft. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic front cross-sectional view of the building according to the first embodiment. [Figure 2] Figure 1 is a schematic diagram of a partial cross-section of the underground portion of the building. [Figure 3] Figure 1 is a schematic plan view showing the arrangement of each retaining pile and the reinforcing structure in the building shown. [Figure 4] This is a schematic plan and cross-sectional view illustrating the fixing of sheet piles to retaining piles. [Figure 5] This is a schematic diagram showing the main parts of the building construction method of the embodiment. [Figure 6] This is a schematic diagram showing the main parts of the building construction method of the embodiment. [Figure 7] This is a schematic front cross-sectional view showing the positional relationship between the retaining piles and the bracing beam members. [Figure 8] This is a schematic front cross-sectional view of the main part of the building according to the second embodiment. [Figure 9] This is a schematic front cross-sectional view showing another embodiment with a different arrangement of beam members. [Modes for carrying out the invention]

[0017] Next, embodiments for carrying out the invention of this application will be described. Figure 1 is a schematic front cross-sectional view of a building according to the first embodiment. Figure 2 is a schematic partial cross-sectional view of the underground portion of the building in Figure 1. As shown in Figure 1, the building of the first embodiment consists of a foundation 1 and a building 2 constructed on foundation 1. In this embodiment, it is assumed that the building is constructed in an area where urban building codes are relaxed. For this reason, foundation 1 and building 2 are close to the boundary of the adjacent property (for example, about 1 to 2 meters). Foundation 1, in this example, is a raft foundation with a pit structure. Building 2 is envisioned as a mid-rise (approximately 4-8 stories) reinforced concrete building.

[0018] The building in this embodiment is constructed on a site with slightly weak ground strength, and therefore ground reinforcement has been carried out. In this embodiment, the ground reinforcement employs a ground replacement method, and in particular, it is carried out by forming a ground replacement layer 3 using resin blocks. More specifically, as shown in Figure 2, the ground replacement layer 3 is a resin block layer formed by laying a large number of resin blocks 31. Each resin block 31 has many openings to allow water to pass through and to reduce weight. Each resin block 31 is made of a mixture of, for example, polypropylene and high-density polyethylene, with a mixing ratio of approximately 30-50% polypropylene (70-50% high-density polypropylene) by weight. Considering environmental and cost aspects, it is preferable to use recycled materials for both PP and HDPE.

[0019] In this example, the ground replacement is relatively small in scale, and a ground replacement layer 3 with an overall thickness of approximately 10-12 cm is formed by stacking about three layers of thin, plate-shaped resin blocks 31, each about 3-4 cm thick. Each resin block 31 is connected by fitting or other means on the top, bottom, left, and right. For example, a configuration of stacking three layers of Super Geo B ("Super Geo" is a registered trademark of Plant Trees Co., Ltd.) is adopted. The ground replacement layer 3 is covered with a permeable civil engineering stabilization sheet (not shown) to prevent concrete from seeping in during the construction of the foundation 1. The structure and construction of the ground replacement layer 3 are disclosed in Patent Documents 2 and 3, which can be referred to.

[0020] Furthermore, retaining piles 41 and sheet piles 42 are installed around the foundation 1, which is built on top of the ground replacement layer 3. The retaining piles 41 and sheet piles 42 are remnants of those used for retaining earth during the construction of the foundation 1. The sheet piles 42 were used as formwork during the construction of the foundation and remained in place even after the completion of the foundation 1. A key feature of the building in this embodiment is that wooden retaining piles 41 are used instead of steel ones such as H-beams. In this embodiment, the retaining piles 41 are made of logs, and in particular, thinned timber is used as the retaining piles 41. The logs used as retaining piles 41 have a diameter (the diameter of the cross-section perpendicular to the length) of about 15 to 30 cm and a length of about 3 to 6 meters. The tip (lower end) of such logs is tapered (pencil-shaped) to make it sharp, and then used as a retaining pile 41.

[0021] As shown in Figure 1, the retaining pile 41 extends in a vertical position, and its tip (lower end) reaches a position deeper than the bottom of the foundation 1, and even deeper than the bottom of the ground replacement layer 3. The driving depth of the retaining pile 41 relative to the bottom of the foundation 1 (indicated by d in Figure 1) is, for example, about 2 to 3 meters. Furthermore, as shown in Figure 1, the back side of the sheet pile 42 is provided with a layer of crushed stone (hereinafter referred to as the backfill crushed stone layer) 421 that extends vertically. The upper surface of the backfill crushed stone layer 421 is covered with a civil engineering stabilization sheet (not shown), and a thin layer of topsoil is placed on top of the civil engineering stabilization sheet.

[0022] Another significant feature of this embodiment of the building is that each retaining pile 41 is reinforced by beams embedded in the ground. This point will be explained with reference to Figures 1 to 3. Figure 3 is a schematic plan view showing the arrangement and reinforcement structure of each retaining pile 41 in the building shown in Figure 1. As shown in Figure 3, multiple retaining piles 41 are provided at equal intervals in the horizontal direction in which the sheet piles 42 extend. The spacing between the retaining piles 41 is approximately 50 cm to 150 cm. In this embodiment, the entire area where the foundation 1 is constructed is rectangular. Therefore, the shape of the excavation recess 9 formed by excavating the ground is also rectangular in plan view. For this reason, the sheet piles 42 are also constructed so as to form a rectangular perimeter in plan view.

[0023] Figure 4 is a schematic plan view of the fixing of sheet piles to retaining piles. As shown in Figure 4(1), each retaining pile 41 is cut so that a flat surface 411 is formed on the side facing the foundation 1. Hereinafter, this flat surface 411 will be referred to as the cut surface. As shown in Figure 4(2), the sheet piles 42 are fixed to the cut surface 411. The size of the cut surface 411 will be explained in terms of the angle (shown as θ in Figure 4(1)) as viewed from the center of the retaining pile 41. If the angle θ is large, the cut portion becomes large, the cross-sectional area of ​​the retaining pile 41 becomes small, and the strength of the pile decreases. Therefore, it is preferable that θ be 180 degrees or less, more preferably 150 degrees or less, and even more preferably 120 degrees or less. Also, if the angle θ is small, the flat surface that the sheet pile 21 contacts becomes small, and there is a possibility that the fixing will not be sufficient. Therefore, it is preferable that θ be 10 degrees or more, more preferably 20 degrees or more, and even more preferably 30 degrees or more. Furthermore, for the center of the retaining pile 41, it is sufficient to assume a flat plate with the same dimensions and shape as the cross-sectional outline and a uniform density distribution, and to use its centroid as the center.

[0024] Each sheet pile 42 is fixed to such a cut surface 411 with fasteners 43 such as nails or anchor bolts. As shown in Figure 4(2), it is preferable that the fasteners 43 are driven in at an angle rather than perpendicular to the surface of the sheet pile 42, and preferably driven in from both sides relative to a perpendicular line drawn from the center of the retaining pile 41 to the sheet pile 42. Sometimes staple nails are used as the fasteners 43.

[0025] Furthermore, when using thick logs as retaining piles 41, they may be used after being cut in half. For example, in the case of logs with a diameter exceeding 30 cm, even when cut in half, they have sufficient strength and can be used as retaining piles 41. In this case, the cut surface (flat surface) of the cut log will be oriented towards the foundation 1 and the sheet pile 42 will be fixed there. Furthermore, if the height of the retaining wall is not very high (i.e., if the excavation recess 9 is not very deep), thin logs with a diameter of 15 cm or less may be used as retaining wall piles 41. For example, if the depth of the excavation recess 9 is about 0.5 to 1.5 meters, thin logs with a diameter of about 10 to 15 cm may be used as retaining wall piles 41.

[0026] As shown in Figure 3, at the corners where the sheet piles 42 intersect perpendicularly, two retaining piles 41 are installed close together to reinforce the intersection. It is preferable that the retaining piles 41 at this location are installed not too far from the corners where the sheet piles 42 intersect perpendicularly. The distance from the corner in the direction in which the sheet piles 42 extend to the center of the retaining pile 41 (shown as L1 in Figure 3) is preferably 30 cm or less.

[0027] In this embodiment, beam members 51A, 51B, 52A, and 52B are provided as reinforcing members for each of the retaining piles 41, and are buried in the ground. As shown in Figures 1 and 2, the buried locations of each beam member 51A, 51B, 52A, and 52B are below the bottom surface of the foundation 1 (at a position deeper than the bottom surface). As with the retaining piles 41, logs are used for each beam member 51A, 51B, 52A, and 52B (the ends are not sharpened). Similarly, thinned timber can be used for each beam member 51A, 51B, 52A, and 52B, with a diameter of approximately 10 to 30 cm. Multiple beam members 51A, 51B, 52A, and 52B can be connected in the length direction to secure the required length. At the connection points, the end faces are brought into contact with each other and fixed with staples or the like, but fixing may not be necessary in some cases. Furthermore, a structure is sometimes adopted in which a protrusion is provided on one end face and a corresponding recess is provided on the other end face, and the two parts are fitted together.

[0028] In this embodiment, two types of reinforcing beam members 51A, 51B, 52A, and 52B are provided. One type, as shown in Figure 3, is a beam member 51A, 51B that extends along the direction in which each retaining pile 41 is aligned and is provided in contact with the aligned retaining pile 41. Hereinafter, these beam members 51A, 51B will be referred to as alignment-direction beam members. For example, as shown in Figure 3, the first alignment-direction beam member 51A is provided in contact with each retaining pile 41 aligned in the first direction, and the second alignment-direction beam member 51B is provided in contact with each retaining pile 41 aligned in the second direction. Each alignment-direction beam member 51A, 51B is in contact with each retaining pile 41 from the inside (the side on which the foundation 1 is provided in a plan view). Each alignment-direction beam member 51A, 51B is often fixed to each retaining pile 41 with nails or anchors, but in some cases, it is simply in contact without being fixed.

[0029] In addition to the beam members 51A and 51B in each direction, in this embodiment, beam members 52A and 52B are provided that are interposed between two opposing retaining piles 41 like support rods. Hereinafter, these beam members 52A and 52B will be referred to as support rod beam members. The support rod beam member consists of a first support rod beam member 52A, which is positioned along the first direction so as to be interposed between two opposing retaining piles 41 in the first direction, and a second support rod beam member 52B, which is positioned along the second direction so as to be interposed between two opposing retaining piles 41 in the second direction.

[0030] The first support beam member 52A and the second support beam member 52B intersect in a plan view as shown in Figure 3, but are positioned offset vertically as shown in Figures 1 and 2. In this example, the first support beam member 52A is on the upper side and the second support beam member 52B is on the lower side. As can be seen from Figures 1 and 3, the first support beam member 52A and the second support beam member 52B form a grid (a right-angle grid in this example) in a plan view, so to speak, like a raft. The first support beam member 52A and the second support beam member 52B may be tied and fixed together with ropes or the like at the intersection point, but they do not need to be fixed.

[0031] As can be seen from Figures 2 and 3, each first parallel beam member 51A rests on each end of each second support beam member 52B. On the other hand, each first support beam member 52A has both ends resting on each second parallel beam member 51B. The ends of each support beam member 52A, 52B and each parallel beam member 51A, 51B may or may not be fixed by ropes or nails. The structure 50 formed by assembling beam members 51A, 51B, 52A, 52B made of multiple logs in a raft-like manner is called an underground raft, and the underground layer 5 on which the underground raft 50 is installed is called the underground raft layer.

[0032] In the underground raft 50 that forms the underground raft layer 5, crushed stone 53 is filled in the spaces between each beam member 51A, 51B, 52A, and 52B. In the examples in Figures 1 to 3, the underground raft 50 is a single layer, but it is also possible to stack multiple single layers consisting of each beam member 51A, 51B, 52A, and 52B to form multiple layers. Below the underground raft layer 5 is a foundation layer 60 made of crushed stone. The foundation layer 60 is a layer that stabilizes the bottom surface of the excavation recess 9 and prevents heaving when the excavation recess is formed.

[0033] Furthermore, a thin layer of crushed stone 61 is provided at the interface between the underground raft layer 5 and the resin block layer 31 to reduce unevenness. On the other hand, a thin layer of lean concrete 62 is provided between the resin block layer 31 and the foundation 1. As described above, the resin block layer 31 is covered with a civil engineering stabilization sheet (not shown), so the civil engineering stabilization sheet is interposed at the interface between the crushed stone layer 61 and the resin block layer 31, and also between the resin block layer 31 and the lean concrete layer 62.

[0034] The construction of a building according to this embodiment will be described in general terms below with reference to Figures 5 and 6. Figures 5 and 6 are schematic diagrams showing the main parts of the building construction method according to the embodiment. The following description also describes an embodiment of the building method invention. When constructing the building according to this embodiment, an area slightly wider than the area where the foundation 1 and building 2 are to be constructed is excavated on the site. Prior to this, as shown in Figure 5(1), retaining piles 41 are driven in. Each retaining pile 41 is driven in at predetermined intervals along the contour of the area to be excavated. This interval and the depth of driving are values ​​specified in the design of the retaining wall. A pile driver or drilling machine is used to drive in the retaining piles 41 as needed. The retaining piles 41 are pre-cut, and a cut surface 411 is formed.

[0035] Next, as shown in Figure 5(2), the area inside where the retaining piles 41 are lined up is gradually excavated to create the foundation. At this time, once a certain depth is reached, sheet piles 42 are installed to prevent the ground from collapsing as the excavation continues. Then, while installing the sheet piles 42, the area is excavated to the required depth to form the foundation recess 9. Furthermore, as shown in Figure 5(3), a space is created behind the sheet piles 42, and crushed stone is filled into it to form the backfill crushed stone layer 421. In addition, below the lowest part of the sheet piles 42, a temporary board may be placed across the adjacent retaining piles 41, and crushed stone may be filled behind it.

[0036] Subsequently, as shown in Figure 5(4), crushed stone is laid on the bottom surface of the excavation recess 9 to form the foundation layer 60. Then, as shown in Figure 6(1), beam members are placed on top of the foundation layer 60 to form the directional beam members 51A, 51B and the support beam members 52A, 52B. Each beam member is assembled to form an underground raft 50, and crushed stone 53 is filled inside the grid to form the underground raft layer 5.

[0037] Next, as shown in Figure 6(2), a thin layer of crushed interfacial stone 61 is laid on top of the underground raft layer 5, and then a resin block layer 3 covered with a civil engineering stabilization sheet is laid. Furthermore, ready-mixed concrete is poured on top of the resin block layer 3 and cured to form a lean concrete layer 62. Subsequently, the foundation 1 is constructed. At this time, as shown in Figure 6(3), formwork 10 is temporarily erected in the central area, and sheet piles 42 are used as formwork at the outermost points. Once the construction of foundation 1 is complete, as shown in Figure 6(4), the formwork 10 other than that of the sheet piles 42 is removed, and building 2 is constructed on foundation 1, completing the building of this embodiment. The above method involves driving each retaining pile 41 in advance prior to the formation of the excavation recess 9. However, the driving of each retaining pile 41 may occur after the formation of the excavation recess 9, or the excavation and the driving of each retaining pile 41 may occur simultaneously.

[0038] According to this embodiment of the building and construction method, when forming the retaining wall, wooden retaining piles 41 are used instead of steel piles such as H-beams. This reduces the load on the ground and has a positive effect on the bearing capacity of the ground, thus reducing the effectiveness of ground replacement performed by laying ground replacement materials such as resin blocks 31. The adoption of lightweight retaining piles 41 makes them easy to transport and handle even for elderly skilled workers, thus avoiding various problems that may arise when inexperienced workers perform the construction. Furthermore, wooden retaining piles 41 are cheaper than steel retaining piles 41 such as H-beams, and are especially cheap when using unsawn logs. Moreover, when used in a configuration with thinned timber and retaining piles 41, it is extremely inexpensive and contributes to promoting the use of thinned timber, thus contributing to forest conservation and the prevention of landslides. And since there is no need to adopt inferior foreign-made retaining piles to reduce costs, the reliability of retaining and foundation work is increased.

[0039] In this process, each retaining pile 41 is reinforced by a beam, so the collapse of the retaining structure is sufficiently prevented. Furthermore, since wooden beams are used, the load on the ground is reduced, thus preventing a reduction in the effectiveness of ground replacement. In this case, in addition to the parallel beam members 51A and 51B, support beam members 52A and 52B are also provided, significantly increasing the effectiveness of earth retention reinforcement. As a method of reinforcing earth retention with beam-shaped members, a waling is known in which a horizontally extending member is fixed to the sheet pile 42. The parallel beam members 51A and 51B in this embodiment correspond to this waling. Conventionally, when waling alone is insufficient to reinforce earth retention, beam members are provided to cross the opening of the excavation recess 9 for further reinforcement. However, beam members that cross such an opening tend to cause problems during the construction of the foundation 1. In the configuration of this embodiment, each support beam member 52A and 52B is located below the foundation 1, so it does not cause any problems during the construction of the foundation 1. In other words, each support beam member 52A and 52B in this embodiment has significance in providing more sufficient reinforcement of earth retention without causing any problems during the construction of the foundation 1.

[0040] For these support beam members 52A and 52B, the positional relationship with the retaining piles 41 is important. This point will be explained below. Figure 7 is a schematic front cross-sectional view showing the positional relationship between the retaining piles and the support beam members. The support beam members 52A and 52B are intended to support the retaining pile 41 so that it does not tilt or fall over due to external earth pressure. Therefore, as shown in Figure 7(1), it is preferable that they contact the retaining pile 41 at the middle of the pile (center position in the height direction). It is also possible to contact it at a lower position, but if it contacts it too low, the effect of supporting the retaining pile 41 will decrease. As shown in Figure 7(2), if L2 is the distance from the lower end of the retaining pile 41 to the contact position of the support beam members 52A and 52B (distance to the center of the beam members 52A and 52B), it is preferable that L2 not fall below 20% of the total length (height) H of the retaining pile 41, and more preferably not fall below 30%.

[0041] Furthermore, while it is possible to implement the construction even if the contact points of the support beam members 52A and 52B are above the middle of the slope, since the support beam members 52A and 52B are installed below the foundation 1, if they are placed too high, it becomes impossible to secure the area in the height direction for installing the sheet piles 42, or to secure the space for placing the foundation 1. In addition, there is the problem of having to unnecessarily make the retaining piles 41 longer and drive them to a deep position. Therefore, as shown in Figure 7(3), if L3 is the distance from the upper end of the retaining pile 41 to the contact points of the support beam members 52A and 52B, it is preferable that L3 not be less than 20% of the total length of the retaining pile 41, and more preferably not be less than 30%. The same applies to the positions where the parallel beam members 51A and 51B abut each retaining pile 41. It is preferable that these positions be within 30% above or below the mid-slope position (30% of the length of the retaining pile 41), and more preferably within 20%.

[0042] As described above, the construction method of the embodiment is one in which the members supporting the foundation 1 remain in place, and these members remain even after the completion of the building. In other words, the building of the embodiment incorporates the wooden members used during the construction of the foundation 1 as supporting structures. This has many advantages. These points will be explained below.

[0043] First, the configuration in which the sheet piles 42 used for retaining the earth are also used as formwork during the construction of the foundation 1 and left in place along with the retaining piles 41 is suitable as a construction technique for narrow sites and is also advantageous in terms of shortening the construction period. Normally, the H-beams and sheet piles used for retaining the earth are removed after the foundation is completed, and the area around the foundation is backfilled. Heavy machinery is used for removal, such as lifting the H-beams. However, in the case of construction on narrow sites, the distance to the boundary with the adjacent site is short, making it difficult to deploy heavy machinery, and thus it has to be done manually. This work is very difficult and time-consuming. On the other hand, in the configuration of this embodiment, there is no process of removing the retaining earth itself, so there is no need to deploy heavy machinery, and after the completion of the foundation 1, only the formwork of the inner part needs to be removed, which significantly shortens the construction period. This greatly contributes to reducing construction costs.

[0044] Leaving the retaining piles 41 in place is highly significant, but leaving heavy piles like H-beams in place will result in continued adverse effects on the soft ground, thus undermining the effectiveness of the ground replacement. However, the configuration of the embodiment using wooden retaining piles 41 is free from this problem. In other words, the configuration of the embodiment has the significance of allowing the benefits of shortening the construction period (reducing costs) by leaving the piles in place without causing the problems that would arise as a result.

[0045] Furthermore, the beam members 51A, 51B, 52A, and 52B that reinforce the retaining piles 41 serve to reinforce the retaining piles 41 during the construction of the foundation 1, as described above, and are significant in sufficiently preventing the collapse of the retaining structure. However, the configuration in which they remain in place also serves several different important functions. First, the beam members 51A, 51B, 52A, and 52B that remain in the ground forming an underground raft even after the building is completed will exhibit a seismic isolation effect during an earthquake. That is, the underground raft 50 consisting of the beam members 51A, 51B, 52A, and 52B will form layers with different natural frequencies in the ground, thereby preventing resonance and achieving seismic isolation. Furthermore, this effect can be enhanced if the beam members 51A, 51B, 52A, and 52B are not fixed to each other or if the fixing is loose. This is because a so-called deflection effect occurs, making it more difficult for vibrations to be transmitted between the beam members 51A, 51B, 52A, and 52B.

[0046] Furthermore, the underground raft layer 5, consisting of underground rafts 50 and crushed stone 53, also provides a ground preservation function. This structure, in which logs are assembled into a raft shape and filled with crushed stone inside, is often used as a riverbank reinforcement structure. This structure has the function of suppressing soil erosion and preventing flooding damage to the surrounding area even if the quay wall collapses. The underground raft layer 5 of this embodiment also has a similar function. In the event of a large-scale flood that inundates the town, the ground directly beneath the foundation 1 is preserved, thus suppressing damage such as the tilting of the building 2 due to soil erosion. From this perspective, it is preferable that the beam members 51A, 51B, 52A, and 52B are fastened and secured to each other with ropes or the like. Furthermore, it is also possible to obtain a ground replacement effect using the underground raft 50. That is, in the configuration of the embodiment, if the inside of the underground raft 50 is left hollow without filling it with crushed stone, the underground raft layer 5 becomes a lighter layer, and thus a ground replacement effect can be obtained. In some cases, the strength can be improved by laying resin blocks inside the underground raft 50.

[0047] Furthermore, in the configuration of this embodiment, the crushed stone backfill layer 421 behind the underground raft layer 5 and sheet piles 42 has significance in mitigating damage by providing a path for groundwater to rise when liquefaction occurs during a major earthquake, especially if the building is constructed on sandy ground such as reclaimed land or near a port. It also has significance in preventing damage caused by groundwater gushing out in unexpected places during torrential rain.

[0048] Next, the building and construction method of the second embodiment will be described. Figure 8 is a schematic front cross-sectional view of the main part of the building of the second embodiment. In the second embodiment as well, the retaining piles 41 and sheet piles 42 are not removed after the completion of the foundation 1 but remain in the ground. However, unlike the first embodiment, the second embodiment assumes a situation where there is ample space on the site, rather than a confined area. For this reason, the sheet piles 42 are not used as formwork during the construction of the foundation 1. That is, since the foundation 1 is constructed at a distance from the retaining piles, it is constructed using formwork separate from the sheet piles 42, and this formwork is removed after the completion of the foundation 1. Therefore, there is some distance between the remaining sheet piles 42 and the foundation 1. As shown in Figure 8, the space between the remaining sheet piles 42 and the foundation 1 is filled with crushed stone, forming an intermediate crushed stone layer 423. Similar to the first embodiment, a civil engineering stabilization sheet (not shown) is placed on top of the intermediate crushed stone layer 423, and surface soil is provided on top of that.

[0049] In the second embodiment as well, the retaining piles 41 are provided with parallel directional beam members 51A, 51B and support beam members 52A, 52B, and these beam members form an underground raft 50. Crushed stone is filled inside the underground raft 50 to form an underground raft layer 5. As a result, these beam members 51A, 51B, 52A, 52B provide a reinforcing effect on the retaining piles 41 during the construction of the foundation 1, and after the completion of the building, they provide seismic isolation and ground preservation effects. Furthermore, the intermediate crushed stone layer 423 between the foundation 1 and the sheet piles 42 provides a path for groundwater to rise, as in the first embodiment, and has the effect of suppressing damage during liquefaction and heavy rainfall.

[0050] In each of the embodiments described above, there may be different configurations for the arrangement of each beam member 51A, 51B, 52A, and 52B. This will be explained with reference to Figure 9. Figure 9 is a schematic front cross-sectional view showing another embodiment in which the arrangement of the beam members is different. In the embodiments described above, each support beam member 52A, 52B was in contact with each retaining pile 41, but as shown in Figure 9(1), it may also be in contact with the parallel beam members 51A, 51B. In this case, the parallel beam members 51A, 51B are interposed in between.

[0051] Furthermore, as shown in Figure 9(2), short auxiliary piles 53 may be driven into the ground at the intersection of the first support beam member 52A and the second support beam member 52B for reinforcement. The auxiliary piles 53 are located below the foundation 1, which is not shown in Figure 9. The auxiliary piles 53 are located underground, with each of the beam members 51A, 51B, 52A, and 52B in the same location. raft It has the effect of stabilizing 50 as a whole. The intersecting support beam members 52A and 53B are preferably fixed to the auxiliary pile 53 with ropes or the like, but they are not fixed and Auxiliary pile 53 In some cases, it may simply be that it is being held in place, restricting lateral movement. Furthermore, as shown in Figure 9(3), there are also cases where two parallel beam members 51A and 51B are provided above and below the contact points of the support beam members 52A and 52B with the retaining piles 41. In this configuration, the function of the bracing is further enhanced by the two parallel beam members 51A and 51B.

[0052] As mentioned above, the configuration using wooden retaining piles 41 has particular advantages when ground replacement is performed using resin blocks 31, but it also has the advantage of low cost when the ground strength is sufficient and ground replacement is not performed. In addition, although not explained here, in configurations where retaining piles are left in place, corrosion problems are unavoidable with steel piles such as H-beams, but with wooden retaining piles 41, the corrosion problem is significantly smaller. Furthermore, when replacing the ground with resin blocks 31, blocks made of foamed resin may be used instead of non-foamed resin. However, blocks made of non-foamed resin with holes for water permeability have the advantage of not being washed away even in the event of heavy rain during construction.

[0053] Furthermore, while the effects of the underground raft 50 described above are particularly pronounced in the case of wooden retaining piles 41, the effect of reinforcing the retaining wall at low cost can also be obtained when using steel retaining piles such as H-beams. Furthermore, the seismic isolation and ground preservation effects of the underground raft layer 5 can be obtained similarly even if the retaining piles 41 and sheet piles 42 used for shoring are removed without being left in place. Therefore, the same seismic isolation and ground preservation effects can be obtained even when steel retaining piles such as H-beams are used.

[0054] Furthermore, for the retaining piles 41 and the beam members 51A, 51B, 52A, and 52B, sawn timber other than logs may be used. However, as mentioned above, using logs offers cost advantages, and using thinned timber in particular offers not only cost benefits but also the advantage of promoting the use of thinned timber. In the above description, Building 2 was described as a mid-rise building, but the present invention is not limited to this and may be applied to low-rise buildings, detached houses, or high-rise buildings. [Explanation of Symbols]

[0055] 1 Basics 2 buildings 3 Ground replacement layer 31 Resin Block 41 Retaining piles 42 Sheet Pile 421 Backfill crushed stone layer 5 Underground raft layer 50 Underground raft 51A, 51B oriented beam members 52A, 52B Support beam material 60 Land Industry Layer 61 Interfacial crushed stone layer 62. Lean concrete layer 9 Root cutting recess

Claims

1. A building comprising a concrete foundation whose lowest surface is in the ground and a building constructed on the foundation, A wooden structure, which is a separate structure from the aforementioned foundation, is embedded beneath the aforementioned foundation. The wooden structure is an underground raft. An underground raft is made up of logs arranged in a grid pattern. A building characterized in that, in the underground raft made of logs assembled in a grid pattern, the intersecting logs are connected to each other, and the inside of the grid is filled with crushed stone or broken stone.

2. The building according to claim 1, characterized in that a pile material is provided for securing the logs that form the underground raft, and the lower end of the pile material reaches a position deeper underground than the underground raft.

3. A building comprising a concrete foundation whose lowest surface is in the ground and a building constructed on the foundation, A wooden structure, which is a separate structure from the aforementioned foundation, is embedded beneath the aforementioned foundation. The wooden structure is an underground raft. An underground raft is made up of logs arranged in a grid pattern. A building characterized by having a hollow space inside the grid of an underground raft or being filled with resin blocks.

4. The building according to claim 3, characterized in that a pile material is provided for securing the logs that form the underground raft, and the lower end of the pile material reaches a position deeper underground than the underground raft.

5. A building comprising a concrete foundation whose lowest surface is in the ground and a building constructed on the foundation, A wooden structure, which is a separate structure from the aforementioned foundation, is embedded beneath the aforementioned foundation. The wooden structure is an underground raft. An underground raft is made up of logs arranged in a grid pattern. An underground raft is a structure characterized by having a horizontal size greater than that of the aforementioned foundation.

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