Reconstruction methods for existing buildings and reconstructed buildings

Abstract

To provide a reconstruction method of an existing building capable of reducing a work period and a construction cost in reconstructing the existing building of which ground water level is higher than a bottom surface of an existing underground skeleton.SOLUTION: A reconstruction method of an existing building is the method for reconstructing an existing building 1 of which ground water level W is higher than a bottom surface of an existing underground skeleton 11. The existing underground skeleton 11 has an existing pressure board 13 configuring the bottom surface and an existing underground outer wall 14. The reconstruction method of the existing building comprises a step S2 of leaving a part of the existing underground outer wall 14 which is deeper than the ground water level W and the existing pressure board 13, demolishing the inside of the existing underground skeleton 11 and forming an underground space S enclosed by the existing pressure board 13 and the existing underground outer wall 14 and a step S3 of constructing a new underground skeleton 30 in the underground space S.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for rebuilding an existing building, and a building rebuilt using this method for rebuilding an existing building. [Background technology]

[0002] BACKGROUND ART Conventionally, methods have been proposed for rebuilding an existing building having an existing underground skeleton built on ground with a high groundwater level (see Patent Documents 1 to 3). Patent Document 1 shows a building reconstruction method in which a new foundation is constructed on the foundation of a building with an underground structure built on ground with a high groundwater level, with a weight that resists buoyancy of the weight that will be lost when the above-ground structure is demolished, and then a new underground structure is constructed on the new foundation while the existing underground structure and the existing above-ground structure are demolished. Patent Document 2 shows a method of dealing with buoyancy during the demolition of an existing structure, in which an existing structure on which groundwater pressure acts is demolished, leaving at least the pressure-resistant plate of the existing structure, and a new structure is constructed on top of the existing pressure-resistant plate.During the demolition, a casing for constructing new piles is installed on the existing pressure-resistant plate at a height higher than the head of groundwater pressure, new concrete piles are driven through the casing, and the heads of the concrete piles and the pressure-resistant plate of the existing structure are integrally joined to resist groundwater pressure.

[0003] Patent Document 3 discloses a method for rebuilding a structure in which an existing structure having an underground structural portion and an aboveground structural portion is demolished to construct a new structure having at least an underground structural portion, while taking measures against groundwater to prevent groundwater from gushing out from the base of the new structure at the site to be rebuilt. As a groundwater countermeasure, an uplift resistance measure is taken in which the bottom portion of the existing underground structural portion is not demolished but is left as a water-stopping portion, giving the bottom portion an uplift resistance force, and a pumping measure is taken to pump up groundwater, and these measures are implemented in separate areas at the site to be rebuilt. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-339816 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-177410 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-79567 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a method for rebuilding an existing building and a rebuilt building that can shorten the construction period and reduce construction costs when rebuilding an existing building where the groundwater level is higher than the bottom surface of the existing underground structure. [Means for solving the problem]

[0006] The inventors have arrived at the present invention by focusing on the fact that this is a reconstruction method for existing buildings constructed on sites with high groundwater levels, and that by leaving the portions of the existing underground exterior walls that are deeper than the groundwater level and the existing pressure plates in place, it is possible to prevent groundwater from seeping into the underground space surrounded by the existing underground exterior walls and the existing pressure plates, while the weight of the existing underground exterior walls and the existing pressure plates resists the buoyancy caused by the groundwater, thereby shortening the construction period and reducing construction costs. The method for rebuilding an existing building of the first invention is a method for rebuilding an existing building (e.g., an existing building 1 described later) that has an existing underground skeleton (e.g., an existing underground skeleton 11 described later) and whose groundwater level (e.g., a groundwater level W described later) is higher than the bottom surface of the existing underground skeleton, and the existing underground skeleton has an existing pressure-resistant plate (e.g., an existing pressure-resistant plate 13 described later) that forms the bottom surface and an existing underground outer wall (e.g., an existing underground outer wall 14 described later) that forms the side surface, and at least In both cases, the method includes a process (e.g., step S2 described below) of demolishing the interior of the existing underground structure while leaving the portion of the existing underground outer wall that is deeper than the groundwater level and the existing pressure plate in place, to form an underground space (e.g., underground space S described below) surrounded by the existing pressure plate and the existing underground outer wall, and a process (e.g., step S3 described below) of constructing a new underground structure (e.g., new underground structure 30 described below) in the underground space.

[0007] Here, "leaving at least the existing pressure-resistant plate" includes a case where only the existing pressure-resistant plate is left in place, and a case where part of the existing foundation on the existing pressure-resistant plate is left in place in addition to the existing pressure-resistant plate. According to this invention, the existing underground outer wall and existing pressure plate remain in place at a depth below the groundwater level, preventing groundwater from seeping into the underground space enclosed by the existing underground outer wall and existing pressure plate. This makes it easy to construct a new underground structure in this underground space. In addition, the weight of the existing underground exterior walls and existing pressure plates below the groundwater level resists the buoyancy of the groundwater, preventing the existing underground structure from floating up when it is demolished. Furthermore, since there is no need to install new heavy objects to resist the buoyancy of the groundwater, construction time and costs can be shortened. In addition, since the existing underground exterior walls and existing pressure plates in the areas deeper than the groundwater level prevent groundwater from seeping in, there is no need to install new water barriers to prevent groundwater seepage, which shortens the construction period and reduces construction costs.

[0008] The rebuilt building of the second invention is a rebuilt building (e.g., rebuilt buildings 4, 4A, 4C described below) that replaces an existing building (e.g., existing building 1 described below) that has an existing underground structure (e.g., existing underground structure 11 described below) and whose groundwater level (e.g., groundwater level W described below) is higher than the bottom surface of the existing underground structure, and is characterized in that the existing underground structure comprises an existing pressure-resistant plate (e.g., existing pressure-resistant plate 13 described below) that forms the bottom surface of the existing underground structure, an existing underground outer wall (e.g., existing underground outer wall 14 described below) that extends from the outer periphery of the existing pressure-resistant plate to at least the height of the groundwater level, and a new underground structure (e.g., new underground structure 30 described below) constructed in the space surrounded by the existing pressure-resistant plate and the existing underground outer wall.

[0009] According to this invention, when constructing a new underground structure for a rebuilding building, the existing underground exterior walls and existing pressure plates in the areas deeper than the groundwater level resist buoyancy while preventing groundwater infiltration, so there is no need to install new water barriers to prevent groundwater infiltration or new heavy objects to counter the buoyancy caused by groundwater, thereby shortening the construction period and reducing construction costs.

[0010] The rebuilt building of the third invention is characterized in that it further comprises existing piles and / or new piles extending downward from the bottom surface of the existing pressure plate.

[0011] According to this invention, in addition to the weight of the existing underground exterior wall and existing pressure plate in the portion deeper than the groundwater level, the pull-out resistance of the existing piles and / or newly constructed piles resists the buoyancy caused by the groundwater, so that the existing underground structure can be more reliably prevented from floating up when it is demolished. Furthermore, since the existing piles and / or the newly constructed piles resist the buoyancy caused by groundwater, there is no need to provide new heavy objects to counter the buoyancy caused by groundwater, which reduces construction costs. [Effects of the Invention]

[0012] According to the present invention, a method for rebuilding an existing building and a rebuilt building can be provided that can shorten construction time and reduce construction costs when rebuilding an existing building where the groundwater level is higher than the bottom surface of the existing underground structure. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a vertical cross-sectional view of an existing building to be rebuilt by a method for rebuilding an existing building according to a first embodiment of the present invention. [Figure 2] 1 is a flowchart of the procedure for rebuilding an existing building according to the first embodiment. [Figure 3] This is an explanatory diagram of the reconstruction procedure for an existing building according to the first embodiment (part 1, after the interior of the existing underground structure has been demolished). [Figure 4] This is an explanatory diagram of the reconstruction procedure for an existing building in the first embodiment (part 2, the state after the reconstruction building has been constructed). [Figure 5] This is a diagram used to determine whether the existing underground structure will float up when its interior is demolished. [Figure 6] FIG. 10 is a vertical cross-sectional view of a rebuilt building according to the second embodiment. [Figure 7] FIG. 10 is an explanatory diagram of the procedure for rebuilding an existing building according to the second embodiment (showing the state in which new piles have been constructed using a pile driver). [Figure 8] FIG. 10 is an explanatory diagram of the procedure for rebuilding an existing building according to the third embodiment (showing the state in which new piles have been constructed using a pile driver). [Figure 9] FIG. 10 is a vertical cross-sectional view of a rebuilt building according to the fourth embodiment. [Figure 10] An explanatory diagram of the reconstruction procedure for an existing building according to the fourth embodiment (after the interior of the existing underground structure has been demolished). DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention relates to a method for rebuilding an existing building with a basement floor, and a rebuilt building, in which the existing pressure-resistant plate and the portion of the existing underground exterior wall that is deeper than the groundwater level serve as buoyancy resistance means and water-blocking means. In the first embodiment of the present invention, an existing building comprises an existing pressure plate, a portion of the existing underground outer wall that is deeper than the groundwater level, and existing piles, and a new underground structure is constructed in the underground space surrounded by the existing pressure plate and the existing underground outer wall (Figures 1 to 5). In the second and third embodiments, new piles are added to the rebuilt building of the first embodiment (Figs. 6 and 7). In the fourth embodiment, a new underground exterior wall is added to the rebuilt building of the first embodiment (Figs. 9 and 10). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the embodiments, the same components will be denoted by the same reference numerals, and the description thereof will be omitted or simplified. [First embodiment] FIG. 1 is a vertical cross-sectional view of an existing building 1 to be rebuilt by a method for rebuilding an existing building according to a first embodiment of the present invention. The existing building 1 comprises existing piles 10 constructed in the ground 2, an existing underground structure 11 constructed on the existing piles 10 in the ground 2, and an existing above-ground structure 12 constructed on the existing underground structure 11. The existing underground structure 11 has an existing foundation 17 including an existing pressure-resistant plate 13 that forms the bottom surface, and an existing underground exterior wall 14 that forms the side surface. The existing underground exterior wall 14 extends from the outer periphery of the existing pressure-resistant plate 13 to the ground surface 3. The existing piles 10 extend downward from the bottom surface of the existing pressure-resistant plate 13.

[0015] Additionally, in the ground 2, an SMW (soil cement continuous wall, soil mixing wall) 20, which is an existing earth retaining wall, is constructed by mixing and stirring soil and a cement-based suspension in a borehole or excavation trench in the ground along the outer periphery of the existing underground outer wall 14 of the existing underground structure 11. Core materials 21 are driven into the SMW 20 at predetermined intervals, and these core materials 21 are integrated with the existing underground structure 11. Furthermore, groundwater exists in the ground 2, and the groundwater level W is lower than the ground surface 3 and higher than the bottom surface of the existing underground structure 11.

[0016] The procedure for rebuilding the existing building 1 will be described below with reference to the flowchart in FIG. In step S1, the existing ground structure 12 is demolished up to the existing first floor floor surface 15 (see FIG. 1). In step S2, as shown in FIG. 3, the interior of the existing underground structure 11 is demolished, leaving the existing underground outer walls 14 and the existing pressure slab 13 in place. Specifically, the existing underground outer walls 14 of the existing underground structure 11 are left in place, and the inner structure surrounded by these existing underground outer walls 14 is demolished from top to the top surface of the existing pressure slab 13. This forms an underground space S surrounded by the existing pressure slab 13 and the existing underground outer walls 14. In this state, the buoyancy acting on the existing underground structure 11 is resisted by the weight of the existing pressure slab 13 and the existing underground outer walls 14 of the existing underground structure 11, the pull-out strength of the existing piles 10, and the pull-out friction resistance of the core material 21 of the SMW 20, preventing the existing underground structure 11 from floating up. In step S3, as shown in FIG. 4, a new underground framework 30 is constructed in the underground space S surrounded by the existing pressure-resistant plate 13 and the existing underground outer wall 14. In step S4, as shown in FIG. 4, a new above-ground skeleton 31 is constructed on the new underground skeleton 30 to form a rebuilt building 4.

[0017] Below, we will consider, with reference to Figure 5, whether or not the existing underground structure will float up due to the buoyancy of groundwater when the interior of the existing underground structure is demolished to form an underground space. First, calculate the buoyancy w1 acting on the existing underground structure 11. The head difference H is expressed by the following formula. H = 21.45m (depth below the existing underground structure) - 5.0m (pressured head) =16.45m

[0018] Therefore, the buoyancy force w1 acting on the existing underground structure is expressed by the following equation: w1=4012m 2 (area of ​​the base of the existing underground structure) x 16.45m (water head difference) ×1t / m 3 =65997t

[0019] The weight of the existing underground structure w2 is 49,888 tons. The pull-out strength w3 of the existing pile is expressed by the following formula. w3 = 998kN (pulling strength per existing pile) x 113 (number of piles) =112774kN =11507t

[0020] Calculate the pull-out friction resistance w4 of the SMW. The pull-out friction resistance of the SMW is assumed to be resisted by only the core material below the bottom surface of the existing underground structure. Therefore, the length of the core material (embedded length) Ls is 26.5m - 21.45m = 5.05m. Furthermore, if the average N value Ns of the ground is 20 and the perimeter L of the core material on one side is 256m, the pull-out friction resistance w4 of the SMW can be expressed by the following formula. w4=1 / 3×(10×Ns×Ls / 3)×L×2 =57906kN =5908t

[0021] Therefore, the formula for determining whether the existing underground structure will float due to the buoyancy of groundwater is as follows: (w2+w3+w4) / w1 =(49888+11507+5908) / 65997 =1.02>1.0 Therefore, it is possible to prevent the existing underground structure from floating up due to the buoyancy of groundwater.

[0022] According to this embodiment, the following effects are obtained. (1) The existing underground outer wall 14 and the existing pressure-resistant plate 13 are left in place in the portion deeper than the groundwater level W, so that it is possible to prevent groundwater from infiltrating into the underground space S surrounded by the existing underground outer wall 14 and the existing pressure-resistant plate 13. Therefore, the new underground structure 30 can be easily constructed in this underground space S. Furthermore, the weight of the existing underground outer wall 14 and the existing pressure plate 13 in the portion deeper than the groundwater level W resists the buoyancy caused by the groundwater, so the existing underground structure 11 can be prevented from floating up when it is demolished. Furthermore, since there is no need to install new heavy objects to resist the buoyancy caused by the groundwater, it is possible to shorten the construction period and reduce construction costs. In addition, since the existing underground exterior wall 14 and existing pressure plate 13 in the area deeper than the groundwater level prevent groundwater from seeping in, there is no need to install a new water barrier to prevent groundwater from seeping in, which shortens the construction period and reduces construction costs.

[0023] (2) In addition to the weight of the existing underground exterior wall 14 and the existing pressure plate 13 that are deeper than the groundwater level, the pull-out resistance of the existing piles 10 resists the buoyancy caused by the groundwater, so that when the existing underground structure 11 is demolished, it is possible to more reliably prevent the existing underground structure 11 from floating up. Furthermore, since the existing piles 10 resist the buoyancy caused by the groundwater, there is no need to provide new heavy objects to counter the buoyancy caused by the groundwater, which reduces construction costs.

[0024] Second Embodiment FIG. 6 is a vertical cross-sectional view of a rebuilt building 4A according to the second embodiment of the present invention. This embodiment differs from the first embodiment in that a new underground skeleton 30 and new piles 32 are constructed in an underground space S surrounded by an existing pressure-resistant plate 13 and an existing underground outer wall 14 to form a rebuilt building 4. The new piles 32 extend downward from the bottom surface of the existing pressure-resistant plate 13. Specifically, in step S2, as shown in FIG. 7, a portion of the existing underground structure 11 located directly above the new pile 32 is demolished to form a vertically continuous opening 16. Next, a casing 41 is installed through the opening 16 from above the existing pressure plate 13 to a position higher than the groundwater level W, and a pile driver 40 is placed on the existing first floor floor surface 15, and the new pile 32 is constructed inside the casing 41 by the pile driver 40. Thereafter, the interior of the existing underground structure 11 is demolished, leaving the existing underground outer wall 14 and the existing pressure plate 13 in place. Note that in this embodiment, the pull-out resistance strength of the new pile 32 also resists buoyancy. According to this embodiment, the same effects as those of (1) and (2) above are obtained.

[0025] Third Embodiment In this embodiment, the method of constructing the new piles 32 is different from that in the second embodiment. That is, in step S2, as shown in Fig. 8, only the central portion of the existing underground structure 11, including the portion located directly above the new pile 32, is demolished down to the top surface of the existing pressure plate 13. Next, a casing 41 is installed from above the existing pressure plate 13 to a position higher than the groundwater level W, and a pile driver 40 is placed on the existing pressure plate 13, and new piles 32 are constructed inside the casing 41 by the pile driver 40. Thereafter, the outer periphery of the existing above-ground structure 12 is demolished down to the top surface of the existing pressure plate 13, leaving the existing underground outer wall 14. Note that in this embodiment, the pull-out resistance of the new pile 32 also resists buoyancy. According to this embodiment, the same effects as those of (1) and (2) above are obtained.

[0026] [Fourth embodiment] FIG. 9 is a vertical cross-sectional view of a rebuilt building 4C according to the fourth embodiment of the present invention. This embodiment differs from the first embodiment in that a new underground exterior wall 33 is provided outside the existing underground exterior wall 14. That is, in step S2, as shown in Fig. 10, a new underground outer wall 33 is constructed outside the existing underground outer wall 14 and joined to the existing pressure-resistant plate 13, and then the inside of the new underground outer wall 33 is dismantled down to the top surface of the existing pressure-resistant plate 13. In this embodiment, the weight of the new underground outer wall 33 also resists buoyancy. According to this embodiment, the same effects as those of (1) and (2) above are obtained.

[0027] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. For example, in each of the above-described embodiments, in step S2, the existing underground outer wall 14 and the existing pressure plate 13 are left in place and the interior of the existing underground structure 11 is demolished to form the underground space S surrounded by the existing pressure plate 13 and the existing underground outer wall 14, but this is not limited to this. That is, the existing underground outer wall 14, the existing pressure plate 13, and a part of the existing foundation 17 on this existing pressure plate 13 may be left in place and the interior of the existing underground structure 11 may be demolished to form the underground space surrounded by the existing foundation 17 including the existing pressure plate 13 and the existing underground outer wall 14. Furthermore, in each of the above-described embodiments, the existing piles 10 and the SMW 20 are provided in the existing building 1, but this is not limiting, and the existing piles 10 and the SMW 20 may not be provided. Furthermore, in each of the above-described embodiments, the SMW 20 in which the core materials 21 are driven into the ground at predetermined intervals is provided as the existing earth retaining wall, but the present invention is not limited to this, and a cast-in-place pile wall may also be used. In addition, in the fourth embodiment, all of the existing underground outer walls 14 and SMW 20 located above the existing pressure-resistant plate 13 were removed, but this is not limited to this, and part of the existing underground outer walls 14 and SMW 20 located above the existing pressure-resistant plate 13 may be left in place. [Explanation of symbols]

[0028] 1...Existing building 2...Ground 3...Ground surface 4, 4A, 4C...Reconstructed building 10...Existing pile 11...Existing underground structure 12...Existing aboveground structure 13...Existing pressure-resistant panel 14...Existing basement exterior wall 15...Existing first floor floor 16...Opening 17...Existing foundation 20...SMW (soil cement continuous wall) 21...Core material 30...New underground structure 31...New above ground structure 32...New piles 33...New underground outer wall 40...Pile driver 41...Casing W...Groundwater level S...Underground space

Claims

1. A method for rebuilding an existing building that has an existing underground structure and whose groundwater level is higher than the bottom surface of the existing underground structure, The existing underground structure has an existing pressure-resistant plate that forms the bottom surface and an existing underground outer wall that forms the side surface, a step of constructing new piles extending downward from the bottom surface of the existing pressure plate using a pile driver from above the existing first floor floor surface, and then dismantling the interior of the existing underground structure while leaving at least the portion of the existing underground outer wall that is deeper than the groundwater level and the existing pressure plate in place, to form an underground space surrounded by the existing pressure plate and the existing underground outer wall; A method for rebuilding an existing building, comprising the step of constructing a new underground structure in the underground space.

2. A rebuilt building that replaces an existing building that has an existing underground structure and whose groundwater level is higher than the bottom surface of the existing underground structure, an existing pressure-resistant plate that constitutes the bottom surface of the existing underground structure; a new underground exterior wall provided outside the existing underground structure and joined to the existing pressure plate; A reconstructed building characterized by comprising: a new underground structure constructed in a space surrounded by the existing pressure-resistant plate and the new underground outer wall.

3. A method for rebuilding an existing building that has an existing underground structure and whose groundwater level is higher than the bottom surface of the existing underground structure, The existing underground structure has an existing pressure-resistant plate that forms the bottom surface and an existing underground outer wall that forms the side surface, a step of providing a new underground outer wall joined to the existing pressure-resistant plate outside the existing underground outer wall, leaving at least the existing pressure-resistant plate in place, and demolishing the existing underground structure to form an underground space surrounded by the existing pressure-resistant plate and the new underground outer wall; A method for rebuilding an existing building, comprising the step of constructing a new underground structure in the underground space.

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