Construction methods and buildings

Abstract

Avoid problems caused by remaining members to support the foundation. [Solution] When constructing a building consisting of a foundation 1 and a building 2, earth retaining piles 41 and sheet piles 42 are installed on the side walls of a recessed space 9 formed by digging down the area that the foundation 1 will occupy. The earth retaining piles 41 are made of wood such as logs, and are driven into the ground so that their tips reach a position lower than the bottom of the recessed space 9. The sheet piles 42 also serve as formwork when constructing the foundation 1, and remain in the ground together with the earth retaining piles 41 after the building is completed. The earth retaining piles 41 are reinforced by beams 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 various buildings and methods for constructing them. [Background technology]

[0002] In recent years, with the progress of urbanization, there has been an increase in the number of cases where residential and other buildings are constructed on sites with soft ground that has low bearing capacity. When building, the bearing capacity of the ground on the site is measured by boring surveys, etc., and ground improvement work is carried out based on the results. After the ground improvement work, the foundation is constructed, and the building portion is then constructed on top of that. Known methods of ground improvement work include the pile method and the ground replacement method. The pile method involves driving piles into hard ground such as diluvial deposits, which is suitable from the perspective of preventing building subsidence, but it is a large-scale and expensive construction method. Furthermore, in the event of a major earthquake, the piles transmit the seismic vibrations to the building, which has caused the building to collapse in some cases. This problem is explained in detail in Patent Document 1. In addition to anchor piles, friction piles are also known as pile methods, but they are similarly expensive and suffer from the problem of transmitting vibrations during a major earthquake.

[0003] Ground replacement ground improvement is a construction method that does not rely on piles and can be implemented relatively inexpensively. Among these, the methods disclosed in Patent Documents 2 and 3 involve laying resin blocks with openings as structural materials to replace the ground. Compared to polystyrene foam ground replacement materials, this method has the advantage of not being affected by rainfall during construction. Furthermore, the resin blocks can store underground water, which has the advantage of preventing rainwater runoff during heavy rain and providing seismic isolation in the event of an earthquake. For this reason, ground replacement methods using resin blocks other than polystyrene foam are becoming widely adopted. This type of ground reinforcement technology can be considered a method of burying foundation support members 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 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned 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 work using resin blocks is carried out prior to the construction of the foundation. An area (root excavation) is excavated on the site that is slightly larger than the area (horizontal area) where the foundation will be constructed. The bottom of the excavated recess (hereafter referred to as the root excavation recess) is then tamped and crushed stone laid, and the area is then covered with a permeable sheet. A number of resin blocks are then laid vertically and horizontally on top of the sheet to form a resin block layer. The resulting resin block layer is strong enough to support the weight of the foundation and building to be constructed above, yet is much lighter than the soil on the site, achieving ground replacement and preventing subsidence.

[0006] When forming this type of resin block layer (ground replacement layer), retaining walls are formed on the side walls of the excavation recess. Traditionally, retaining walls are formed by driving steel retaining piles, such as H-beams, into the ground at equal intervals and installing sheet piles to bridge between them. These retaining walls are designed to prevent the walls of the excavation recess from collapsing when the ground replacement layer is formed or the foundation is constructed.

[0007] Even at construction sites where foundations are constructed while retaining walls are being used in this way, the effects of labor shortages and rising material costs are becoming more apparent. As the workforce ages, the work of transporting and driving heavy steel retaining piles such as H-beams is becoming more strenuous (load-intensive). As a result, there are increasing cases where the work is being replaced by younger, less skilled workers, or by foreign workers with little knowledge, instead of experienced, older workers.

[0008] However, when such inexperienced workers work on the site, unexpected accidents can occur due to insufficient construction of the earth retaining wall. In other words, when the roots are excavated and a recess is formed, the recess becomes a space free of earth pressure, which disrupts the balance of earth pressure with the neighboring site. Therefore, it is necessary to ensure that the earth retaining strength is sufficient to withstand the earth pressure of the neighboring land, and for this reason, the back side of the sheet piles (the side opposite the foundation) must be sufficiently backfilled and compacted. However, if inexperienced workers neglect this, accidents such as the earth retaining piles tilting or attracting earth pressure from the neighboring land, causing land subsidence on the neighboring land, may occur. Also, crushed stone may be filled behind the earth retaining piles to serve as a water path when the groundwater level rises, but if workers neglect or do this insufficiently, groundwater may rise to unexpected places and overflow during heavy rain, etc., resulting in accidents.

[0009] Furthermore, there has been an influx of cheap, foreign-made steel earth retaining piles, such as H-beams, but some of these piles are smaller in size and thinner than standard piles. Using these cheap, foreign-made H-beams as earth retaining piles to reduce construction costs can result in the strength assumed by the architect in the earth retaining design not being realized, leading to accidents such as the earth retaining piles tilting or partial collapse. The collapse of an earth retaining pile not only significantly delays the foundation construction schedule, but also often reduces the bearing capacity of the neighboring land, potentially causing serious accidents such as houses tilting (uneven settlement of the ground).

[0010] Furthermore, apart from these problems of labor shortages and rising material costs, problems can also arise due to the steel earth retaining piles themselves, such as H-beams. When an earth retaining pile is driven into the ground, the voids around the pile are compacted. In this case, steel earth retaining piles such as H-beams have a large load, which causes compaction and upsets the balance of stress in the ground. As a result, partial settlement can occur even when the ground is replaced with a resin block layer. In such cases, the settlement is often only a few centimeters to 10 cm, and while it rarely becomes a major problem, it can reduce the reliability of the ground replacement method using a resin block layer.

[0011] The above problem becomes particularly serious when earth retaining piles and sheet piles are left in place even after the construction of a building is complete. In urban areas where building standards (floor area ratio, building coverage ratio) have been relaxed, buildings with relatively heavy loads (such as mid-rise apartment buildings) are often constructed on narrow plots of land. In these cases, the foundations are relatively large, with pit structures, and so deep excavation is required to install earth retaining piles. However, because the plots are narrow and the distance to neighboring land is short, heavy machinery cannot be brought in, so the earth retaining piles may have to remain in place even after the building is completed.

[0012] Of the remaining earth retaining structures, sheet piles rarely cause problems, but steel earth retaining piles such as H-beams can cause ground subsidence over time. In other words, the heavy earth retaining piles gradually sink, and as a result, the surrounding ground can be dragged down. The problem is exacerbated in urban areas where building standards have been relaxed, as these areas are often located on alluvial plains with high groundwater levels. Steel earth retaining piles, such as H-beams, do not easily conform to the alluvial clay layers (i.e., they have low frictional resistance) and are prone to settling under their own weight. This not only worsens the balance of groundwater distribution due to settlement, but also causes corrosion problems due to constant exposure to groundwater. When earth retaining piles corrode and become thinner, voids form, further destabilizing the ground.

[0013] The present invention was made based on this awareness of the problem, and was made with the goal of avoiding problems caused by components that remain in place to support the foundation. [Means for solving the problem]

[0014] In order to solve the above problems, this specification discloses inventions of a construction method and a building. The construction method according to the disclosed invention is a method for constructing a building consisting of a foundation and a building constructed on the foundation. This construction method includes a root cutting process of digging down an area including a horizontal area to be occupied by the foundation on the site where the building is to be constructed to form a recessed space relative to the ground surface, a retaining wall process of installing sheet piles on the side walls of the recessed space formed in the root cutting process to reinforce the side walls and prevent them from collapsing, a foundation construction process of constructing a foundation in the recessed space formed in the root cutting process, and a building construction process of constructing a building on the foundation constructed in the foundation construction process. The retaining wall process is as follows: a pile driving step of driving wooden piles so that their tips reach a position lower than the bottom surface of the recessed space formed or created in the root cutting step; and a pile installation step of installing multiple piles. Contains: The earth retaining pile driving step is a step of driving a plurality of earth retaining piles at intervals along the edge of the bottom surface of the recessed space formed or created in the root excavation step. When the central side of the recessed space is defined as the inside and the opposite side as the outside, the sheet pile installation process is a process of fixing each sheet pile to the earth retaining pile so as to bridge the gap between adjacent earth retaining piles, and fixing each sheet pile to the inside of the earth retaining pile. The foundation construction process is a process of constructing the foundation by pouring concrete and curing it while using each sheet pile installed in the sheet pile installation process as part of the formwork. In this construction method, the retaining piles driven in the retaining pile driving process and the sheet piles installed in the sheet pile installation process remain on the ground of the site as wooden structures that support the foundation even after construction of the building is completed. This specification also discloses a construction method according to another invention. This construction method according to another invention is a construction method for constructing a building consisting of a foundation and a building constructed on the foundation, and includes a root cutting process of digging down an area including a horizontal area to be occupied by the foundation on the site on which the building is to be constructed to form a recessed space relative to the ground surface, a retaining wall process of installing sheet piles on the side walls of the recessed space formed in the root cutting process to reinforce the side walls and prevent them from collapsing, a foundation construction process of constructing a foundation in the recessed space formed in the root cutting process, and a building construction process of constructing a building on the foundation constructed in the foundation construction process. The retaining wall process is as follows: a retaining pile driving step of driving a wooden retaining pile so that its tip reaches a position lower than the bottom surface of the recessed space formed or created in the root cutting step; A sheet pile installation process for installing multiple sheet piles; Contains: The earth retaining pile driving step is a step of driving a plurality of earth retaining piles at intervals along the edge of the bottom surface of the recessed space formed or created in the root excavation step. When the central side of the recessed space is defined as the inside and the opposite side as the outside, the sheet pile installation process is a process of fixing each sheet pile to the earth retaining pile so as to bridge the gap between adjacent earth retaining piles, and fixing each sheet pile to the inside of the earth retaining pile. This method allows the retaining piles driven in the retaining pile driving process and the sheet piles installed in the sheet pile installation process to remain on the ground of the site as wooden structures supporting the foundation even after construction of the building is completed. This construction method involves filling the gap between the remaining sheet piles and the foundation with crushed stone or broken rubble stone. The construction methods according to the above-mentioned inventions can be configured such that the inner surface of the retaining pile is a flat cut surface, and the sheet pile installation process is a process of fixing the sheet pile to this cut surface. In order to solve the above problems, this specification also discloses an invention for a building. The building according to the disclosed invention is a building consisting of a foundation and a building constructed on the foundation. This building has buried wooden structures that support the foundation, and the wooden structures consist of sheet piles and earth retaining piles. The sheet piles are installed along the outer surface of the foundation, covering it. The earth retaining piles are installed on the opposite side of the sheet piles from the foundation, and the sheet piles are fixed to the earth retaining piles. The sheet piles extend horizontally, and multiple retaining piles are arranged in a line in the direction in which the sheet piles extend. The tip of each retaining pile reaches a position deeper than the bottom of the foundation. In addition, in order to solve the above problems, this building Each earth retaining pile has a flat cut surface on the foundation side, and the sheet piles are fixed to the cut surface of each earth retaining pile. It can have the following configuration. In addition, in order to solve the above problems, this building Retaining piles home, Between the two earth retaining piles facing each other across the foundation, a wooden beam is installed on the underside of the foundation. The two retaining posts in question It can have a configuration in which it serves as a bracing beam material for the In addition, in order to solve the above problems, this building The bracing beams are provided between two earth retaining piles facing each other in a first direction, and also between two earth retaining piles facing each other in a second direction perpendicular to the first direction, and these bracing beams are assembled in a lattice pattern below the foundation. It can have the following configuration. In order to solve the above problems, this specification also discloses a building according to another invention. The building according to another invention is a building consisting of a foundation and a building constructed on the foundation, in which a wooden structure supporting the foundation is buried, and the wooden structure is an underground raft installed under the foundation. In this building according to another invention, the underground raft is made of logs arranged in a lattice pattern. In order to solve the above problem, a building according to another invention is: An underground raft made of logs arranged in a grid pattern, with crossing logs connected to each other and the inside of the grid filled with broken or crushed stone. It can have the following configuration. These disclosed inventions have in common the fact that they are structures in which wooden structures that support foundations are buried. [Effects of the Invention]

[0015] As explained below, in the construction methods and buildings according to the disclosed inventions, wooden earth retaining piles are used instead of steel piles such as H-beams to form earth retaining structures. This reduces the load on the ground and reduces the loss of effectiveness when replacing the ground with soil replacement materials such as resin blocks. Wooden earth retaining piles are also cheaper than steel earth retaining piles such as H-beams, offering cost advantages. Furthermore, the labor required to remove sheet piles and earth retaining piles can be reduced, providing cost advantages and shortening the construction period. In this case, the inner surface of the retaining pile is a flat cut surface, and by fixing the sheet pile to this cut surface, it is possible to easily ensure sufficient fixing strength of the sheet pile. Furthermore, in the building according to the disclosed invention, the configuration in which parallel beam members are provided reinforces the retaining piles, thereby enhancing the effectiveness of preventing the retaining piles from collapsing during foundation construction, and achieving the effect of stabilizing the retaining piles in the ground after the building is completed. Furthermore, in the building according to the disclosed invention, the configuration in which bracing beams are provided reinforces the retaining piles, thereby enhancing the effectiveness of preventing the retaining piles from collapsing during foundation construction, and achieving the effect of stabilizing the retaining piles in the ground after the building is completed. Furthermore, by assembling the bracing rods in a lattice pattern, the effectiveness of preventing the earth retaining wall from collapsing is enhanced when the foundation is being constructed, and after the building is completed, the bracing rods act as underground rafts, providing ground replacement, seismic isolation, and ground conservation functions. In addition, according to a building according to another disclosed invention, the lattice-shaped underground raft provides the effects of ground replacement, seismic isolation, and ground conservation functions. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic front cross-sectional view of a building according to a first embodiment. [Figure 2] FIG. 2 is a partial cross-sectional schematic view of the underground portion of the building of FIG. 1. [Figure 3] FIG. 2 is a schematic plan view showing the arrangement of each earth retaining pile and the reinforcement structure of the building shown in FIG. 1. [Figure 4] FIG. 10 is a schematic cross-sectional plan view showing the fixing of a sheet pile to an earth retaining pile. [Figure 5] 1 is a schematic diagram showing the main parts of a construction method for a building according to an embodiment. [Figure 6] 1 is a schematic diagram showing the main parts of a construction method for a building according to an embodiment. [Figure 7] This is a schematic front cross-sectional view showing the positional relationship between the retaining piles and the bracing beams. [Figure 8] FIG. 10 is a schematic front cross-sectional view of the main part of the building of the second embodiment. [Figure 9] FIG. 10 is a schematic cross-sectional front view showing another embodiment in which beams are arranged differently. DETAILED DESCRIPTION OF THE INVENTION

[0017] Next, a description will be given of a mode (embodiment) for carrying out the invention of this application. Fig. 1 is a schematic cross-sectional front view of a building according to a first embodiment. Fig. 2 is a schematic cross-sectional partial view of an underground portion of the building shown in Fig. 1. As shown in Figure 1, the building of the first embodiment consists of a foundation 1 and a building 2 constructed on the foundation 1. In this embodiment, it is assumed that the building is constructed in an urban area where building standards have been relaxed. For this reason, the foundation 1 and building 2 are located close to the boundary with the neighboring property (for example, about 1 to 2 meters). In this example, Foundation 1 is a mat foundation with a structure that forms a pit. Building 2 is assumed to be a medium-rise (approximately 4 to 8 stories) reinforced concrete building.

[0018] The building in this embodiment is built on a site with slightly weak ground strength, and the ground is reinforced. In this embodiment, the ground reinforcement is performed using a ground replacement method, in particular 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 a shape with many openings to allow water to pass through and reduce weight. Each resin block 31 is formed, for example, from a mixture of polypropylene and high-density polyethylene, with a mixing ratio of, for example, about 30-50% polypropylene (70-50% high-density polypropylene) by weight. Considering environmental and cost considerations, it is preferable to use recycled materials (recycled materials) for both PP and HDPE.

[0019] This example involves a relatively small-scale ground replacement project, in which three layers of thin, plate-like resin blocks 31, each about 3-4 cm thick, are stacked to form a ground replacement layer 3 with a total thickness of about 10-12 cm. Each resin block 31 is connected by fitting it together vertically and horizontally. For example, a configuration is used in which three layers of Super Geo B ("Super Geo" is a registered trademark of Plant Trees Co., Ltd.) are stacked. The ground replacement layer 3 is covered with a permeable civil engineering stabilization sheet (not shown) to prevent concrete from seeping in during construction of the foundation 1. The structure and construction of the ground replacement layer 3 are disclosed in Patent Documents 2 and 3, which may be referenced.

[0020] Additionally, earth retaining piles 41 and sheet piles 42 are provided around the periphery of the foundation 1, which is built on the ground replacement layer 3. The earth retaining piles 41 and sheet piles 42 are what remain from the earth retaining piles that were used for earth retaining during the construction of the foundation 1. The sheet piles 42 were also used as formwork during the construction of the foundation, and remain even after the foundation 1 was completed. A major feature of the building of this embodiment is that wooden earth retaining piles 41 are used instead of steel piles such as H-beams. In this embodiment, the earth retaining piles 41 are logs, and thinned wood is used as the earth retaining piles 41 in particular. The logs used as the earth retaining piles 41 have a diameter (diameter of the cross section perpendicular to the length direction) of about 15 to 30 cm and a length of about 3 to 6 meters. The tips (bottom ends) of such logs are tapered (pencil-shaped) and sharpened before being used as the earth retaining piles 41.

[0021] As shown in Figure 1, the earth retaining pile 41 extends in a vertical position, with its tip (bottom end) reaching a position deeper than the bottom of the foundation 1 and further reaching a position deeper than the bottom of the ground replacement layer 3. The driving depth of the earth retaining pile 41 (shown as d in Figure 1) relative to the bottom of the foundation 1 is, for example, about 2 to 3 meters. 1, a layer filled with crushed stone (hereinafter referred to as backfill crushed stone layer) 421 is provided on the back side of the sheet pile 42 so as to extend in the vertical direction. A civil engineering stabilization sheet (not shown) is placed on the top surface of the backfill crushed stone layer 421, and a thin layer of topsoil is placed on top of the civil engineering stabilization sheet.

[0022] Another major feature of the building of this embodiment is that each earth retaining pile 41 is reinforced by beams buried in the ground. This will be explained with reference to Figures 1 to 3. Figure 3 is a plan view schematic diagram showing the arrangement and reinforcing structure of each earth retaining pile 41 in the building shown in Figure 1. As shown in Figure 3, the earth retaining piles 41 are provided at equal intervals in the horizontal direction in which the sheet piles 42 extend. The intervals between the earth retaining piles 41 are approximately 50 cm to 150 cm. In this embodiment, the entire area in which 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 to form a rectangular periphery in plan view.

[0023] FIG. 4 is a schematic cross-sectional plan view showing the fastening of sheet piles to earth retaining piles. As shown in FIG. 4(1), each earth retaining pile 41 is cut to form a flat surface 411 on the side facing the foundation 1. Hereinafter, this flat surface 411 will be referred to as the cut surface. As shown in FIG. 4(2), a sheet pile 42 is fastened to the cut surface 411. The size of the cut surface 411 is explained in terms of the angle (indicated by θ in FIG. 4(1)) from the center of the earth retaining pile 41. As the angle θ increases, the cut portion becomes larger, the cross-sectional area of ​​the earth retaining pile 41 decreases, and the strength of the pile decreases. Therefore, θ is preferably 180 degrees or less, more preferably 150 degrees or less, and even more preferably 120 degrees or less. Furthermore, as the angle θ decreases, the flat surface with which the sheet pile 21 contacts becomes smaller, which may result in insufficient fastening. Therefore, θ is preferably 10 degrees or more, more preferably 20 degrees or more, and even more preferably 30 degrees or more. The center of the retaining pile 41 can be determined by imagining a flat plate with uniform density distribution and the same dimensions and shape as the cross-sectional outline, and locating the center of gravity of the plate.

[0024] Each sheet pile 42 is fixed to such a cutting surface 411 with fixing devices 43 such as nails or anchor bolts. As shown in Figure 4 (2), the fixing devices 43 are preferably driven obliquely rather than perpendicularly to the surface of the sheet pile 42, and are preferably driven from both sides of a perpendicular line drawn from the center of the earth retaining pile 41 to the sheet pile 42. Staple nails may also be used as fixing devices 43.

[0025] When using thick logs as retaining piles 41, they may be split in half. For example, if a log has a diameter of more than 30 cm, it is strong enough to be used as a retaining pile 41 even when split in half. In this case, the cut surface (flat surface) of the half faces the foundation 1, and sheet piles 42 are fixed there. Furthermore, if the height of the earth retaining structure is not too high (the root excavation recess 9 is not too deep), thin logs with a diameter of 15 cm or less may be used as the earth retaining piles 41. For example, if the depth of the root 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 the earth retaining piles 41.

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

[0027] In this embodiment, beams 51A, 51B, 52A, and 52B are buried in the ground as reinforcement members for each of the earth retaining piles 41. As shown in FIGS. 1 and 2, the beams 51A, 51B, 52A, and 52B are buried below the bottom of the foundation 1 (deeper than the bottom). Like the earth retaining piles 41, logs are used for the beams 51A, 51B, 52A, and 52B (their tips are not sharpened). Similarly, thinned timber can be used for the beams 51A, 51B, 52A, and 52B, each measuring approximately 10 to 30 cm in diameter. To ensure the required length, multiple beams 51A, 51B, 52A, and 52B can be connected lengthwise. At the connection points, the end faces are abutted against each other and secured with nails or the like, but securing may not be necessary. It is also possible to employ a structure in which a protrusion is provided on one end face and a matching recess is provided on the other end face, and the two are fitted together.

[0028] In this embodiment, two types of reinforcing beams 51A, 51B, 52A, and 52B are provided. As shown in FIG. 3 , the beams 51A and 51B extend along the direction in which the earth retaining piles 41 are arranged and abut against the arranged earth retaining piles 41. Hereinafter, these beams 51A and 51B are referred to as "arrangement beams." For example, as shown in FIG. 3 , a first arrangement beam 51A abuts against each earth retaining pile 41 arranged in a first direction, and a second arrangement beam 51B abuts against each earth retaining pile 41 arranged in a second direction. Each arrangement beam 51A and 51B abuts against each earth retaining pile 41 from the inside (the side on which the foundation 1 is provided in plan view). In many cases, each arrangement beam 51A and 51B is fixed to each earth retaining pile 41 with nails or anchors, but in some cases, they simply abut against each other without being fixed.

[0029] In addition to these parallel beams 51A, 51B, in this embodiment, beams 52A, 52B are provided that act as bracing rods between two opposing earth retaining piles 41. Hereinafter, these beams 52A, 52B will be referred to as bracing rod beams. The bracing rod beams consist of a first bracing rod beam 52A arranged along the first direction so as to be interposed between two opposing earth retaining piles 41 in the first direction, and a second bracing rod beam 52B arranged along the second direction so as to be interposed between two opposing earth retaining piles 41 in the second direction.

[0030] The first brace beam 52A and the second brace beam 52B intersect in a plan view as shown in FIG. 3, but are arranged offset vertically as shown in FIGS. 1 and 2. In this example, the first brace beam 52A is on the upper side and the second brace beam 52B is on the lower side. As can be seen from FIGS. 1 and 3, the first brace beam 52A and the second brace beam 52B form a lattice shape (a right-angled lattice shape in this example) in a plan view, which is like a raft. The first brace beam 52A and the second brace beam 52B may be secured at the intersection with a rope or the like, but they do not have to be secured.

[0031] As can be seen from Figures 2 and 3, each first lateral beam 51A rests on each end of each second support beam 52B. On the other hand, both ends of each first support beam 52A rest on each second support beam 51B. The ends of each support beam 52A, 52B may be fixed to each of the lateral beams 51A, 51B with ropes or nails, or they may not be fixed at all. This raft-shaped structure 50, in which multiple log beams 51A, 51B, 52A, 52B are assembled, is called an underground raft, and the underground layer 5 in which the underground raft 50 is installed is called an underground raft layer.

[0032] In the underground raft 50 forming the underground raft layer 5, the spaces between the beams 51A, 51B, 52A, and 52B are filled with broken rubble stones 53. In the example of Figures 1 to 3, the underground raft 50 has one level, but it may also have multiple levels by stacking multiple single levels each made up of beams 51A, 51B, 52A, and 52B. Below the underground raft layer 5 is a foundation layer 60 made of broken granite stones. 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] At the interface between the underground raft layer 5 and the resin block 31 layer, a thin interfacial crushed stone layer 61 is provided to reduce unevenness. On the other hand, a thin basal concrete layer 62 is provided between the resin block 31 layer and the foundation 1. As described above, the resin block 31 layer is covered with a civil engineering stabilization sheet (not shown), so a civil engineering stabilization sheet is interposed at the interface between the interfacial crushed stone layer 61 and the resin block 31 layer, and a civil engineering stabilization sheet is also interposed between the resin block 31 layer and the basal concrete layer 62.

[0034] The construction of such an embodiment of a building will be described below in brief with reference to Figures 5 and 6. Figures 5 and 6 are schematic diagrams showing the main parts of the construction method of the embodiment of the building. The following description also describes the embodiment of the construction method invention. When constructing the building of this embodiment, an area on the site slightly larger than the area where the foundation 1 and building 2 are planned to be constructed is excavated and root cutting is performed. Prior to this, as shown in Figure 5 (1), retaining piles 41 are driven. Each retaining pile 41 is driven at a predetermined interval along the outline of the area where root cutting is planned. This interval and driving depth are values ​​specified in the retaining pile design. A pile driver or a boring machine is used to drive the retaining piles 41 as necessary. The retaining piles 41 are previously cut to form cutting surfaces 411.

[0035] Next, as shown in Figure 5 (2), the inside of the area where the earth retaining piles 41 are lined up is excavated little by little to remove the roots. When doing this, once the excavation has reached a certain depth, sheet piles 42 are installed, and the excavation continues while preventing the ground from collapsing. Then, while installing the sheet piles 42, the excavation recess 9 is excavated to the required depth to form the excavation recess 9. Furthermore, as shown in Figure 5 (3), a space is created behind the sheet piles 42, and crushed stone is filled in this space to form a backfill crushed stone layer 421. Note that below the bottom of the sheet piles 42, a temporary board may be placed as a bridge between adjacent earth retaining piles 41, and crushed stone may be filled behind this.

[0036] Thereafter, as shown in Figure 5(4), broken gravel stones are laid on the bottom of the excavation recess 9 to form the foundation layer 60. Then, as shown in Figure 6(1), beams are placed on top of the foundation layer 60 to form the parallel beams 51A, 51B and the bracing beams 52A, 52B. The beams are assembled to form the underground raft 50, and the inside of the grid is filled with broken gravel stones 53 to form the underground raft layer 5.

[0037] Next, as shown in Figure 6 (2), a thin interfacial crushed stone layer 61 is laid on 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 the resin block layer 3 and cured to form a basal concrete layer 62. Thereafter, the foundation 1 is constructed. At this time, as shown in Figure 6(3), formwork 10 is temporarily set up in the center, and sheet piles 42 are used as formwork at the outermost locations. Then, when the construction of the foundation 1 is completed, as shown in Figure 6(4), the formwork 10 other than the sheet piles 42 is removed, and the building 2 is constructed on the foundation 1, completing the building of the embodiment. In addition, the above method involves driving each retaining pile 41 in advance prior to forming the root excavation recess 9, but the driving of each retaining pile 41 may occur after the formation of the root excavation recess 9, or the root excavation and the driving of each retaining pile 41 may be performed simultaneously.

[0038] According to the building and construction method of this embodiment, when forming the earth retaining structure, wooden earth retaining piles 41 are used instead of steel piles such as H-beams, which reduces the load on the ground and has a positive effect on the bearing capacity of the ground, thereby reducing the loss of the effect of ground replacement carried out by laying ground replacement materials such as resin blocks 31. The use of lightweight earth retaining piles 41 makes them easy to transport and handle, even for elderly, experienced workers, and avoids various problems that can arise from construction by inexperienced workers. Furthermore, wooden earth retaining piles 41 are cheaper than steel earth retaining piles 41 such as H-beams, and are particularly cheap when made from unsawn logs. Furthermore, when used with thinned wood as earth retaining piles 41, they are extremely inexpensive and contribute to promoting the use of thinned wood, thereby contributing to the conservation of forests and the prevention of landslides. Furthermore, there is no need to use inferior foreign-made earth retaining piles to reduce costs, which increases the reliability of earth retaining piles and foundation work.

[0039] In this case, each earth retaining pile 41 is reinforced by beams, so the collapse of the earth retaining structure is sufficiently prevented. Furthermore, because the beams are made of wood, the load on the ground is small, and the effect of preventing a reduction in the effect of ground replacement is demonstrated. In this case, in addition to the parallel beams 51A and 51B, the bracing beams 52A and 52B are also provided, significantly enhancing the effectiveness of the earth retaining reinforcement. A known method of reinforcing the earth retaining structure using beam-like members is waling, which secures horizontally extending members to the sheet piles 42. The parallel beams 51A and 51B in the embodiment correspond to this waling. Conventionally, when waling alone is insufficient to reinforce the earth retaining structure, beams are installed across the openings of the excavation recesses 9 for further reinforcement. However, such beams crossing the openings tend to interfere with the construction of the foundation 1. In the configuration of the embodiment, the bracing beams 52A and 52B are located below the foundation 1 and therefore do not interfere with the construction of the foundation 1. In other words, the bracing beams 52A and 52B in the embodiment are significant in providing sufficient reinforcement for the earth retaining structure without interfering with the construction of the foundation 1.

[0040] For such bracing beams 52A, 52B, the positional relationship with the earth retaining pile 41 is important. This point will be explained below. Figure 7 is a schematic front cross-sectional view showing the positional relationship between the earth retaining pile and the bracing beams. The bracing beams 52A and 52B support the earth retaining pile 41 to prevent it from tilting or collapsing due to external soil pressure, so they preferably abut against the earth retaining pile 41 at a position halfway up the pile 41 (the center position in the height direction), as shown in Figure 7(1). A position lower than this is also possible, but abutting at a position too low reduces the effectiveness of supporting the earth retaining pile 41. As shown in Figure 7(2), if the distance from the bottom end of the earth retaining pile 41 to the abutment position of the bracing beams 52A and 52B (the distance to the center of the beams 52A and 52B) is L2, then L2 should preferably be no less than 20% of the total length (height) H of the earth retaining pile 41, and more preferably no less than 30%.

[0041] Although it is possible to position the contact points of the bracing beams 52A, 52B above the mid-slope, since the bracing beams 52A, 52B are installed below the foundation 1, if they are positioned too high, it may become impossible to secure a vertical area for installing the sheet piles 42 or to secure space for placing the foundation 1. Another problem arises, which is that the earth retaining piles 41 must be unnecessarily long and driven deep. Therefore, assuming that the distance from the top end of the earth retaining pile 41 to the contact points of the bracing beams 52A, 52B is L3 as shown in Figure 7(3), L3 should preferably be no less than 20% of the total length of the earth retaining pile 41, and more preferably no less than 30%. The same applies to the positions where the parallel beams 51A, 51B abut against the respective retaining piles 41. These positions are also preferably within 30% above and below the mid-slope position (30% of the length of the retaining piles 41), and more preferably within 20%.

[0042] As described above, the construction method of the embodiment is a method in which the members supporting the foundation 1 remain, even after the building is completed. In other words, the building of the embodiment uses the wooden members used in constructing the foundation 1 as supporting structures. This has many advantages. This point will be explained below.

[0043] First, the configuration in which the sheet piles 42 used for the earth retaining structure also serve as formwork for the construction of the foundation 1 and are left in place along with the earth retaining piles 41 is suitable as a construction technique for narrow sites and is advantageous in terms of shortening the construction period. Typically, the H-shaped steel beams and sheet piles used for the earth retaining structure are removed after the foundation is completed, and the area around the foundation is backfilled. Heavy machinery is used for the removal, such as for pulling up the H-shaped steel beams. However, when building on narrow sites, the distance to the boundary with the neighboring land is short, making it difficult to deploy heavy machinery, and manual labor is the only option. This work is extremely difficult and time-consuming. On the other hand, the configuration of the embodiment does not require the removal of the earth retaining structure itself, eliminating the need for heavy machinery. After the foundation 1 is completed, only the inner formwork needs to be removed, significantly shortening the construction period. This significantly contributes to reducing construction costs.

[0044] While there is great significance in leaving the earth retaining piles 41 in place, leaving heavy piles such as H-beams in place will have a negative impact on the soft ground, continuing to undermine the effectiveness of the ground replacement. However, this problem is not present in the configuration of the embodiment that uses wooden earth retaining piles 41. In other words, the significance of the configuration of the embodiment lies in the fact that while retaining the piles allows for the benefit of shortening the construction period (reducing costs), it prevents problems from arising as a result.

[0045] Furthermore, the beams 51A, 51B, 52A, and 52B that reinforce the earth retaining pile 41 are significant in that they reinforce the earth retaining pile 41 during the construction of the foundation 1 as described above and adequately prevent the earth retaining pile from collapsing, but the configuration in which they are left in place fulfills several different important functions. First, the beams 51A, 51B, 52A, and 52B that remain after the building is completed and form the underground raft provide a seismic isolation effect in the event of an earthquake. In other words, the underground raft 50, consisting of the beams 51A, 51B, 52A, and 52B, forms layers in the ground with different natural frequencies, preventing resonance and achieving seismic isolation. This effect can be enhanced by not fastening the beams 51A, 51B, 52A, and 52B together, or by loosely fastening them together. This is because a so-called damping effect occurs, which makes it difficult for vibrations to be transmitted between the beams 51A, 51B, 52A, and 52B.

[0046] The underground raft layer 5, consisting of the underground raft 50 and the broken rubble stones 53, also functions to preserve the ground. A structure in which logs are assembled into a raft shape and filled with broken rubble stones inside is often used as a reinforcement structure for river banks. This structure has the function of suppressing soil runoff and preventing flooding damage in the surrounding area even if the bank collapses. The underground raft layer 5 of the embodiment has a similar function. In the event of a large-scale flood that inundates the entire town, the ground directly below the foundation 1 is preserved, thereby suppressing damage such as tilting of the building 2 due to soil erosion. From this perspective, it is preferable that the beams 51A, 51B, 52A, and 52B are fastened together with ropes or the like. It is also possible to obtain a ground replacement effect by 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 being filled with broken rubble stones, the underground raft layer 5 becomes a lightweight layer, and a ground replacement effect is obtained. In some cases, resin blocks may be laid inside the underground raft 50 to improve its strength.

[0047] In the configuration of the embodiment, the backfill crushed stone layer 421 behind the underground raft layer 5 and the sheet piles 42 is significant in that it provides a path for underground water to rise in the event of liquefaction during a major earthquake, thereby reducing damage if the building is constructed on sandy ground such as in a reclaimed land or near a port. It is also significant in that it provides a path for underground water to rise during heavy rain, preventing damage caused by groundwater erupting in unexpected places.

[0048] Next, a description will be given of a building and a building method according to a second embodiment. Fig. 8 is a schematic front cross-sectional view of the main part of the building according to the second embodiment. In the second embodiment, the earth retaining piles 41 and sheet piles 42 are also left in the ground after the foundation 1 is completed, and are not removed. However, unlike the first embodiment, the second embodiment is designed for a site with ample space rather than a narrow lot. For this reason, the sheet piles 42 are not also used as formwork when constructing the foundation 1. In other words, since the foundation 1 is constructed at a location slightly away from the earth retaining piles, a formwork separate from the sheet piles 42 is used for construction, and this formwork is removed after the foundation 1 is completed. Therefore, there is a certain distance between the remaining sheet piles 42 and the foundation 1. 8, crushed stone is filled in the space between the remaining sheet piles 42 and the foundation 1, forming an intermediate crushed stone layer 423. As in the first embodiment, a civil engineering stabilization sheet (not shown) is placed on top of the intermediate crushed stone layer 423, and topsoil is placed on top of that.

[0049] In the second embodiment, the earth retaining pile 41 is provided with parallel beams 51A, 51B and bracing beams 52A, 52B, which form an underground raft 50. The interior of the underground raft 50 is filled with crushed gravel to form an underground raft layer 5. These beams 51A, 51B, 52A, 52B reinforce the earth retaining pile 41 during the construction of the foundation 1, and also provide seismic isolation and ground preservation effects after the construction of the building is completed. Similar to the first embodiment, the intermediate crushed stone layer 423 between the foundation 1 and the sheet pile 42 provides a path for underground water to rise, thereby suppressing damage during liquefaction or heavy rain.

[0050] In each of the above-described embodiments, the arrangement of beams 51A, 51B, 52A, and 52B may be different. This will be described with reference to Fig. 9. Fig. 9 is a schematic front cross-sectional view showing another embodiment in which the arrangement of beams is different. In the above-described embodiments, the stop beams 52A, 52B abut against the earth retaining piles 41, but as shown in Fig. 9(1), they may abut against the parallel beams 51A, 51B. In this case, the parallel beams 51A, 51B are interposed between the stop beams 52A, 52B.

[0051] 9(2), a short auxiliary pile 53 may be driven into the intersection of the first brace beam 52A and the second brace beam 52B to reinforce the structure. The auxiliary pile 53 is located below the foundation 1 (not shown in FIG. 9). The auxiliary pile 53 acts to stabilize the underground pile 50 as a whole, which is made up of the beams 51A, 51B, 52A, and 52B. It is preferable to secure the intersecting brace beams 52A and 53B to the auxiliary pile 53 with ropes or the like, but it is also possible that they are not secured and are simply locked to the underground pile 50 to restrict lateral movement. 9(3), two parallel beams 51A, 51B may be provided above and below the contact position of the bracing beams 52A, 52B with the retaining pile 41. In this configuration, the two parallel beams 51A, 51B further strengthen the wale-raising function.

[0052] As mentioned above, the configuration using wooden earth retaining piles 41 is particularly advantageous when ground replacement is performed using resin blocks 31, but it also has the advantage of being low cost when the ground strength is sufficient and ground replacement is not performed. Also, although not explained here, in a configuration where the earth retaining piles remain, corrosion is unavoidable in the case of steel piles such as H-beams, but with wooden earth retaining piles 41, the corrosion problem is significantly less. 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 passage have the advantage that there is no problem of water washing away even in heavy rain during construction.

[0053] Furthermore, the effect of the underground raft 50 described above is particularly pronounced in the case of wooden retaining piles 41, but it can also be used in the case of steel retaining piles such as H-beams to provide the effect of reinforcing the retaining pile at low cost. The seismic isolation and ground preservation effects of the underground raft layer 5 can be obtained in the same way even if the earth retaining piles 41 and sheet piles 42 used for earth retaining are removed without being left behind. Therefore, the same seismic isolation and ground preservation effects can be obtained even when steel earth retaining piles such as H-beams are used.

[0054] Furthermore, sawn wood other than logs may be used for the earth retaining piles 41 and the beams 51A, 51B, 52A, and 52B. However, as mentioned above, using logs has a cost advantage, and when thinned wood is used in particular, in addition to the cost advantage, there is also the advantage of contributing to the promotion of the use of thinned wood. In the above description, building 2 is 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. Building 3 Ground replacement layer 31 Resin Block 41 Earth retaining pile 42 Yaita 421 Backfill crushed stone layer 5 Underground raft layer 50 Underground raft 51A, 51B Beams in the parallel direction 52A, 52B Bracing beams 60 Land Industry Layer 61 Interfacial crushed stone layer 62 Disposable Concrete Layer 9 Root cutting recess

Claims

1. A construction method for constructing a building consisting of a foundation and a building constructed on the foundation, a root cutting process of digging down an area including a horizontal area to be occupied by a foundation on a site where a building is to be constructed, to form a recessed space relative to the ground surface; a retaining step of providing sheet piles on the side wall surfaces of the recessed space formed in the root cutting step to reinforce the side wall surfaces so as to prevent the side wall surfaces from collapsing; a foundation construction process of constructing a foundation in the recessed space formed in the root cutting process; A building construction process in which a building is constructed on the foundation constructed in the foundation construction process; It contains The retaining wall process is as follows: a retaining pile driving process for driving a wooden retaining pile so that its tip reaches a position lower than the bottom surface of the recessed space formed or created in the root cutting process; A sheet pile installation process for installing multiple sheet piles; It contains The earth retaining pile driving step is a step of driving a plurality of earth retaining piles at intervals along the edge of the bottom surface of the recessed space formed or created in the root cutting step, When the center side of the recessed space is defined as the inside and the opposite side as the outside, the sheet pile installation process is a process of fixing each sheet pile to the earth retaining pile so as to bridge the gap between adjacent earth retaining piles, and fixing each sheet pile to the inside of the earth retaining pile, The foundation construction process is a process in which the foundation is constructed by pouring concrete and curing it while using each sheet pile installed in the sheet pile installation process as part of the formwork. This construction method is characterized in that the retaining piles driven in the retaining pile driving step and the sheet piles installed in the sheet pile installation step remain on the ground of the site as wooden structures supporting the foundation even after construction of the building is completed.

2. A construction method for constructing a building consisting of a foundation and a building constructed on the foundation, a root cutting process of digging down an area including a horizontal area to be occupied by a foundation on a site where a building is to be constructed, to form a recessed space relative to the ground surface; a retaining step of providing sheet piles on the side wall surfaces of the recessed space formed in the root cutting step to reinforce the side wall surfaces so as to prevent the side wall surfaces from collapsing; a foundation construction process of constructing a foundation in the recessed space formed in the root cutting process; A building construction process in which a building is constructed on the foundation constructed in the foundation construction process; It contains The retaining wall process is as follows: a retaining pile driving process for driving a wooden retaining pile so that its tip reaches a position lower than the bottom surface of the recessed space formed or created in the root cutting process; A sheet pile installation process for installing multiple sheet piles; It contains The earth retaining pile driving step is a step of driving a plurality of earth retaining piles at intervals along the edge of the bottom surface of the recessed space formed or created in the root cutting step, When the center side of the recessed space is defined as the inside and the opposite side as the outside, the sheet pile installation process is a process of fixing each sheet pile to the earth retaining pile so as to bridge the gap between adjacent earth retaining piles, and fixing each sheet pile to the inside of the earth retaining pile, The earth retaining piles driven in the earth retaining pile driving process and the sheet piles installed in the sheet pile installation process are left on the ground of the site as wooden structures supporting the foundation even after the construction of the building is completed. A construction method characterized by filling crushed stone or broken rubble stone between the remaining sheet piles and the foundation.

3. 3. A construction method according to claim 1, wherein the inner surface of the retaining pile is a flat cut surface, and the sheet pile installation step is a step of fixing the sheet pile to this cut surface.

4. A building consisting of a foundation and a building constructed on the foundation, A wooden structure is buried to support the foundation. The wooden structures are sheet piles and earth retaining piles. The sheet piles are provided along the outer surface of the foundation and cover the outer surface of the foundation, The earth retaining piles are installed on the opposite side of the sheet pile foundation, and the sheet piles are fixed to the earth retaining piles. The sheet piles extend horizontally, and a plurality of the earth retaining piles are arranged in a line in the direction in which the sheet piles extend. A building characterized in that the tip of each earth retaining pile reaches a depth greater than the bottom of the foundation.

5. 5. The building according to claim 4, wherein each of the earth retaining piles has a flat cut surface on the side of the foundation, and the sheet piles are fixed to the cut surface of each of the earth retaining piles.

6. A building as described in Claim 4, characterized in that when the side of each retaining pile on which the foundation is installed is considered to be the inside in a plan view, a directional beam extending in the direction of the arrangement of the multiple retaining piles is installed on the inside of the multiple retaining piles, and the directional beam is installed on the inside of the multiple retaining piles at a position below the foundation.

7. A building as described in claim 4, characterized in that between two of the retaining piles that face each other across the foundation, a wooden beam is provided on the underside of the foundation, serving as a bracing beam for the two retaining piles.

8. The building described in claim 7, characterized in that the bracing rod beams are arranged between two of the retaining piles facing each other in a first direction, and also between two of the retaining piles facing each other in a second direction perpendicular to the first direction, and these bracing rod beams are assembled in a lattice pattern below the foundation.

9. 9. A building according to claim 8, wherein the bracing beams assembled in a lattice pattern are connected to each other, and the inside of the lattice is filled with broken granite or crushed stone.

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