Mountain Remains

Abstract

This invention provides a retaining wall that enables labor savings in the construction of a new retaining wall inside the outer structure. [Solution] The retaining wall according to the present invention is a retaining wall 2N newly installed inside the outer frame 3 of the underground portion 1U of an existing building during building reconstruction work, comprising an upper retaining wall 21, an intermediate retaining wall 22, and a lower retaining wall 23, wherein the upper retaining wall 21 and the lower retaining wall 23 are composed of a pile and sheet pile wall formed by a plurality of main piles 9 installed so as to penetrate a plurality of main pile through holes 5 formed in the pressure slab at predetermined intervals along the boundary 214 in the vicinity of the boundary between the outer frame of the underground portion and the pressure slab, and sheet piles 12 installed between adjacent main piles at predetermined intervals, and the intermediate retaining wall 22 is composed of a plurality of main piles 9 installed at predetermined intervals and a cut surface 35 of the edge portion 4e of the pressure slab that remains after the pressure slab is separated between adjacent main piles at predetermined intervals.

Description

Technical Field

[0001] The present invention relates to a newly installed earth-retaining wall in building reconstruction work.

Background Art

[0002] In building reconstruction work, a method of constructing a composite earth-retaining wall in which the underground outer wall and / or the existing earth-retaining wall of an existing building and a new earth-retaining wall are integrated is known (see Patent Document 1). In Patent Document 1, first, a part of the underground slab 11 of the existing building 10 is demolished to construct the earth-retaining wall 22 for constructing the underground part of the new building 20. This new earth-retaining wall 22 is constructed at a position below the foundation slab (pressure-resistant slab) of the existing building 10, and is not constructed inside the underground outer wall (peripheral side frame body) 13. Therefore, after constructing the earth-retaining wall 22, when demolishing the underground slab 11 of the existing building 10 while leaving the underground outer wall 13, struts 14 are installed between the opposing underground outer walls 13, 13 at the position where the underground outer wall 13 reaches a predetermined self-supporting height. Similarly, while replacing the struts 14 to support the underground outer wall 13, the lower floor slabs 11, 11... are sequentially demolished and removed. Finally, the foundation slab (pressure-resistant slab) of the existing building 10 is removed so that the excavation plate 15 is exposed, and excavation of the new underground part deeper than the foundation level of the existing building 10 is performed while installing a predetermined number of stages of struts 24.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] However, in Patent Document 1, the new earth-retaining wall 22 is not constructed inside the underground outer wall (peripheral side frame body) 13. When constructing a new retaining wall inside the outer structural frame that constitutes the outer perimeter structure, one might consider constructing a retaining wall such as a sheet pile wall. However, in this case, the work of installing sheet piles over the entire inside of the outer structural frame is complicated and labor-intensive, which presents a challenge. This invention has been made in view of the above-mentioned problems, and provides a retaining wall that reduces the labor required for installing horizontal sheet piles and reduces the labor required for constructing a new retaining wall inside the outer structure. [Means for solving the problem]

[0005] The earth retaining wall according to the present invention is an earth retaining wall newly constructed inside the outer frame of the underground portion of an existing building during building reconstruction work, comprising an upper earth retaining wall provided above the location where the pressure slab of the underground portion existed, an intermediate earth retaining wall provided at the location where the pressure slab existed, and a lower earth retaining wall provided below the location where the pressure slab existed, wherein the upper earth retaining wall and the lower earth retaining wall are composed of a pile and sheet pile wall formed by providing a plurality of main piles installed so as to penetrate a plurality of main pile penetration holes formed in the pressure slab at predetermined intervals along the boundary in the vicinity of the boundary between the outer frame of the underground portion and the pressure slab, and sheet piles installed between adjacent main piles at predetermined intervals, and the intermediate earth retaining wall is characterized by comprising a plurality of main piles installed at predetermined intervals and the cut surface of the edge of the pressure slab that remains after the pressure slab has been separated between adjacent main piles at predetermined intervals. Furthermore, the cut surface of the edge of the pressure-resistant plate is characterized by being composed of the inner surfaces of multiple core-punched holes formed using a core-punching drill so as to be continuous with the pressure-resistant plate. According to the present invention, the work of installing horizontal sheet piles can be streamlined, and labor savings can be achieved in the work of constructing a new retaining wall inside the outer structure. [Brief explanation of the drawing]

[0006] [Figure 1] A vertical cross-sectional view (Embodiment 1) showing the construction procedure for the retaining wall construction method. [Figure 2]A vertical cross-sectional view (Embodiment 1) showing the construction procedure for the retaining wall construction method. [Figure 3] A cross-sectional view (Embodiment 1) showing the construction procedure for a retaining wall construction method. [Figure 4] A diagram (Embodiment 1) showing the procedure for forming a main pile penetration hole in the pressure-resistant slab. [Figure 5] A diagram showing the procedure for separating the pressure-resistant slab from the outer structure (Embodiment 1). [Figure 6] A diagram showing the newly constructed retaining wall (corresponding to the view of arrow AA in Figure 2(d)) (Embodiment 1). [Modes for carrying out the invention]

[0007] Embodiment 1 Referring to Figures 1 to 6, a building reconstruction project employing the retaining wall construction method according to Embodiment 1 will be described. As shown in Figure 1(a), the building reconstruction project involves the demolition of the existing building 1 and the construction of a new building. The existing building 1 is, for example, a building with a rectangular cross-section (see Figure 3). As shown in Figure 1(a), the demolition of the existing building 1 involves the demolition of the above-ground portion 1A of the existing building 1, followed by the demolition of the underground portion 1U of the existing building 1. The retaining wall construction method according to Embodiment 1 is employed in the underground portion demolition work. Note that in the ground G surrounding the underground portion 1U of the existing building 1, there are cases where the existing retaining wall 2E remains in place and cases where the existing retaining wall 2E has been removed. Embodiment 1 will be explained using the reconstruction project of an existing building 1 in which the existing retaining wall 2E remains as an example.

[0008] In the retaining wall construction method according to Embodiment 1, new retaining walls 2N, 2N (see Figure 3(d)) are constructed inside one pair of opposing outer structural bodies 3a, 3b of the outer perimeter structural body 3R (see Figure 3(a)) which has a rectangular cross-section in the underground portion 1U. Furthermore, new retaining walls 2M, 2M are constructed outside the existing retaining wall 2E that remained on the outside of the other pair of opposing outer structural bodies 3c, 3d of the outer perimeter structural body 3R (see Figures 3(b) to (d)). According to the retaining wall construction method according to Embodiment 1, the new retaining wall is constructed by connecting the newly constructed retaining walls 2N, 2N inside one pair of opposing outer structural bodies 3a, 3b and the newly constructed retaining walls 2M, 2M outside the other pair of opposing outer structural bodies 3c, 3d. For example, let's consider a case where the outer perimeter structure 3R of the underground section 1U has a rectangular cross-section, with one pair of opposing outer structures 3a and 3b being the longer side of the rectangle, and the other pair of opposing outer structures 3c and 3d being the shorter side of the rectangle. In this case, new retaining walls 2N and 2N are constructed inside the outer structures 3a and 3b on the longer side, and new retaining walls 2M and 2M are constructed outside the outer structures 3c and 3d on the shorter side.

[0009] For example, as shown in Figure 3, there is limited site boundary space on the north and south sides of the existing building, making it difficult to construct a new retaining wall outside the existing retaining wall 2E on the north and south sides of the underground portion of the existing building. Under these site conditions, new retaining walls 2N, 2N are constructed inside the outer structural elements 3a, 3b on the north and south sides, and new retaining walls 2M, 2M are constructed outside the existing retaining walls 2E, 2E that remained outside the outer structural elements 3c, 3d on the east and west sides (see Figure 3(d)). Specifically, new retaining walls 2N, 2N are constructed inside the outer structures 3a, 3b on the north and south sides, which form the outer structures on the longer sides, and new retaining walls 2M, 2M are constructed outside the existing retaining walls 2E, 2E that remained on the outside of the outer structures 3c, 3d on the east and west sides, which form the outer structures on the shorter sides. In this case, the new retaining walls are constructed by connecting the new retaining walls 2N, 2N constructed inside the outer structures 3a, 3b on the north and south sides, and the new retaining walls 2M, 2M constructed outside the existing retaining walls 2E, 2E on the outside of the outer structures 3c, 3d on the east and west sides.

[0010] The retaining wall construction method according to Embodiment 1 includes the following steps shown in Figures 1 and 2. Specifically, the retaining wall construction method includes a demolition step, a pile penetration hole formation step, a work platform formation step, a pile installation step, an excavation and platform installation step, an excavation and retaining wall construction step, a pressure slab separation and subdivision step, a pressure slab removal and retaining wall construction step, and a final retaining wall construction step. Figures 1 to 3 illustrate the construction procedure when new retaining walls 2N, 2N are constructed inside the outer structures 3a, 3b on the north and south sides, and new retaining walls 2M, 2M are constructed outside the existing retaining walls 2E, 2E on the outside of the outer structures 3c, 3d on the east and west sides.

[0011] In the demolition step, as shown in Figure 1(a), after the above-ground demolition work, in which the above-ground portion 1A of the existing building 1 is demolished, the underground portion 1U is demolished, leaving the outer perimeter frame 3R and the pressure-resistant slab 4 of the underground portion 1U. In other words, the underground interior portion 1B of the underground portion 1U, such as columns, beams, and floors, is demolished. This demolition step allows the demolition work of the underground interior portion 1B to be carried out all at once, making the demolition work more efficient.

[0012] As shown in Figure 1(a), the pile penetration hole formation step includes a pile penetration hole formation step that forms pile penetration holes 5 for penetrating the main piles of the main pile sheet pile wall, and a support pile penetration hole formation step that forms support pile penetration holes 6 for penetrating support piles for supporting the platform. As shown in Figure 3(a), in the pile penetration hole formation step, multiple pile penetration holes 5, 5… are formed in the pressure slab 4 at predetermined intervals along the boundary 34 between the northern and southern outer structures 3a, 3b and the pressure slab 4, in the vicinity of the boundary 34. Although not shown in Figure 3(a), in the support pile penetration hole formation step, multiple support pile penetration holes 6, 6… are formed at predetermined intervals along the east-west direction on the central side of the pressure slab 4 in the north-south direction for penetrating support piles.

[0013] The main pile penetration hole 5 is a through hole for passing through the H-shaped steel that constitutes the main pile 9 (see Figure 1(c)). The main pile penetration hole 5 is formed by removing a portion 5s enclosed by multiple core-drilled holes 5a, 5a... formed in the pressure slab 4 using a core-drilling drill, as shown in Figure 4(a), and as shown in Figure 4(b). The support pile penetration hole 6 is a through hole for passing through the H-shaped steel or other steel materials that constitute the support pile 10 (see Figure 1(c)). The support pile penetration hole 6 is formed in the same way as the main pile penetration hole 5 by removing a portion enclosed by multiple core-drilled holes formed in the pressure slab 4 using a core-drilling drill. In this way, since the main pile penetration hole 5 and the support pile penetration hole 6 are formed using a core-drilling drill, noise and vibration can be reduced compared to when drilling work into the pressure slab 4 using heavy machinery such as a rock auger. Therefore, the impact of noise and vibration on the surrounding area can be reduced.

[0014] After forming the main pile penetration holes 5 and the support pile penetration holes 6 in the pressure-resistant slab 4, the process proceeds to the work platform formation and introduction hole formation steps shown in Figure 1(b). In the work platform formation step, soil S is placed on the pressure-resistant slab 4 up to near the ground surface GL, and the soil S is backfilled inside the outer perimeter structure 3R of the underground portion 1U to form the work platform 8. The introduction hole formation step includes an introduction hole formation step for the main pile penetration holes 5 and an introduction hole formation step for the support pile penetration holes 6. In the introduction hole formation step for the main pile penetration holes 5, an introduction hole 5A is formed from the work platform 8 to reach the main pile penetration holes 5. In the introduction hole formation step for the support pile penetration holes 6, an introduction hole 6A is formed from the work platform 8 to reach the support pile penetration holes 6.

[0015] Next, the process moves to the pile installation step shown in Figure 1(c). The pile installation step includes a main pile installation step and a support pile installation step. In the main pile installation step, multiple main piles 9, 9, ... are installed by passing the main pile 9 through each of the multiple main pile through-holes 5, 5, ... via the introduction hole 5A. As a result, as shown in Figures 1(c) and 3(b), multiple main piles 9, 9, ... are installed inside the outer structures 3a, 3b on the north and south sides, along the outer structures 3a, 3b, at predetermined intervals in the east-west direction. In the support pile installation step, as shown in Figure 1(c), multiple support piles 10, 10 ... are installed by passing the support pile 10 through each of the multiple support pile through-holes 6, 6, ... via the introduction hole 6A. In the main pile installation step, the main pile 9 is installed so that its lower end 9b is located below the lowest point GN (see Figure 2(d)) of the newly constructed building 1N, and its upper end 9a is located near the ground surface GL. Similarly, in the support pile installation step, the support pile 10 is installed so that its lower end 10b is located below the lowest point GN of the building 1N, and its upper end 10a is located near the ground surface GL.

[0016] The operations of the introduction hole forming step and the pile installation step are performed using, for example, a heavy machine such as an earth auger installed on the work floor 8. As shown in Fig. 3(b), a plurality of main piles 9A, 9A,... are also installed at predetermined intervals along the north-south direction in the ground G outside the existing earth-retaining walls 2E, 2E outside the east and west outer skeletons 3c, 3d. Note that H-shaped steel is used as the main piles 9A. Also in this case, using a heavy machine such as an earth auger, installation holes for installing the main piles 9A are formed in the ground G outside the existing earth-retaining walls 2E, and the main piles 9A are installed in the installation holes. Similar to the main piles 9, the main piles 9A are installed such that their lower ends are positioned below the position GN that is the lowermost surface of the newly constructed building 1N, and their upper ends are positioned near the ground surface GL.

[0017] Next, the process proceeds to the excavation and gantry installation step shown in Fig. 1(d). In the excavation and gantry installation step, the earth and sand S backfilled on the pressure-resistant slab 4 are excavated, and the gantry 11 is installed so as to span over the upper end sides of the plurality of support piles 10, 10,... installed in the support pile installation step. By installing this gantry 11, it becomes possible to, for example, carry heavy machinery onto the gantry 11 to perform excavation work of the earth and sand S, lifting and carrying-out work of blocks described later, and the like, and carry materials onto the gantry 11. The gantry 11 is also used as a passage for workers.

[0018] Next, the process proceeds to the excavation and earth-retaining wall (upper earth-retaining wall) construction step shown in Fig. 2(a). In the excavation and earth-retaining wall construction step, the earth and sand S backfilled on the pressure-resistant slab 4 are excavated, and horizontal sheet piles 12 (see Fig. 6) are installed between the adjacent main piles 9, 9 exposed by excavation to form a main pile horizontal sheet pile wall. Then, while excavating the earth and sand S up to the upper surface of the pressure-resistant slab 4 (see Fig. 2(b)), the horizontal sheet piles 12 are sequentially installed between the adjacent main piles 9, 9 exposed by excavation to form the main pile horizontal sheet pile wall (see Fig. 6). As described above, the north-south upper earth-retaining wall (main pile horizontal sheet pile wall) 21 (see Fig. 2(b)) positioned above the pressure-resistant slab 4 is constructed.

[0019] Incidentally, in the excavation and earth-retaining wall (upper earth-retaining wall) construction step, the earth and sand S backfilled on the pressure-resistant slab 4 is excavated, and as shown in Fig. 3(b) and Fig. 3(c), the outer side bodies 3c, 3d on the east and west sides and the existing earth-retaining walls 2E, 2E on the outer side of the outer side bodies 3c, 3d are dismantled. Then, horizontal sheet piles 12A are installed between the adjacent main piles 9A, 9A exposed by the dismantling of the east and west outer side bodies 3c, 3d and the existing earth-retaining walls 2E, 2E, so as to form a main pile horizontal sheet pile wall. Through the above steps, the east and west upper earth-retaining walls (main pile horizontal sheet pile walls) 21A, 21A (see Fig. 3(c)) positioned above the pressure-resistant slab 4 are constructed.

[0020] Then, by connecting the upper earth-retaining walls 21, 21 newly installed on the inner side of the north and south outer side bodies 3a, 3b with the upper earth-retaining walls 21A, 21A newly installed on the outer side of the position where the east and west outer side bodies 3c, 3d and the existing earth-retaining walls 2E, 2E were provided, the upper earth-retaining walls 21, 21, 21A, 21A are constructed on the north, south, east and west sides at positions above the pressure-resistant slab 4 (see Fig. 3(c)).

[0021] Incidentally, in the process of constructing the upper earth-retaining wall 12 and the upper earth-retaining wall 21A, struts (not shown) are appropriately erected on the upper earth-retaining wall 12 and the upper earth-retaining wall 21A to construct a strut support structure.

[0022] After the upper earth-retaining walls 21, 21, 21A, 21A are constructed, the process proceeds to the pressure-resistant slab separation and subdivision step shown in Fig. 2(b). In the pressure-resistant slab separation and subdivision step, as shown in Fig. 2(b) and Fig. 3(c), the pressure-resistant slab 4 is separated from the outer side bodies 3a, 3b, and the pressure-resistant slab 4 is subdivided into a plurality of blocks 4a, 4a, ....

[0023] In the pressure slab separation step, as shown in Figure 5(a), a plurality of core holes 5b, 5b… are formed in the pressure slab 4 along the vicinity of the boundary 214 between the upper retaining wall 21 and the pressure slab 4. In other words, in the pressure slab separation step, the pressure slab 4 is separated from the outer structure 3a, 3b by forming these continuous core holes 5b, 5b…. As a result, the pressure slab 4 is separated from the outer structure 3a, 3b between adjacent main piles 9, 9, leaving the cut surface 35 of the edge 4e of the pressure slab 4 (see Figures 5(b) and 6).

[0024] In the pressure slab subdivision step, as shown in Figure 5(a), a group of core holes 5c, 5c… connected to the aforementioned group of core holes 5b, 5b… are formed in the pressure slab 4 in a direction perpendicular to the boundary 214. These groups of core holes 5c, 5c… are formed at predetermined intervals along the boundary 214. The length of this predetermined interval corresponds to the interval of the subdivided block 4a. Furthermore, a cut line 5d is formed perpendicular to the boundary 214 so as to connect to the end core hole 5c of the aforementioned group of core holes 5c, 5c…. Also, as shown in Figure 3(c), a cut line 5e is formed in the central part of the pressure slab 4 between the northern and southern outer structures 3a, 3b, in a direction perpendicular to the cut line 5d (east-west direction). Multiple cut lines 5e are formed at predetermined intervals along the direction of the cut line 5d. As described above, as shown in Figure 3(c), the pressure-resistant slab 4 is subdivided into blocks 4a partitioned by core holes 5b, 5b…, core holes 5c, 5c… and cut lines 5d, 5e, and blocks 4a partitioned by cut lines 5d, 5e. The core holes 5b and 5c are formed using a core drill. The cut lines 5d and 5e are formed using a road cutter. However, when forming the cut line 5d using a road cutter, the road cutter interferes with the upper retaining wall 21, making it impossible to form a cut line 5d that reaches the core hole 5b. Therefore, the portion where a cut line 5d cannot be formed is cut by a group of multiple core holes 5c, 5c….

[0025] Then, the process moves to the steps of removing the pressure slab and constructing the retaining wall, as shown in Figure 2(c). Specifically, in the pressure slab removal step, the pressure slab 4 is removed by lifting and transporting each of the subdivided blocks 4a, 4a, ... one by one using heavy machinery such as a backhoe. For example, a hook part (not shown) is provided on block 4a, and each of the blocks 4a, 4a, ... is lifted and transported one by one using heavy machinery such as a backhoe that has been brought onto the platform 11.

[0026] In the construction step of the retaining wall (intermediate retaining wall), the pressure slab 4 is separated between adjacent main piles 9,9, and the cut surface 35 of the remaining edge 4e of the pressure slab 4 is made to function as part of the newly constructed retaining wall 2N, that is, as part of the intermediate retaining wall 22 (see Figure 6). In other words, without installing horizontal sheet piles on the surface side of the cut surface 35 of the edge 4e of the pressure slab 4 that remains after the pressure slab 4 is separated between adjacent main piles 9,9, the cut surface 35 is made to function as part of the newly constructed retaining wall 2N.

[0027] In other words, the intermediate retaining wall 22, which constitutes a part of the retaining wall 2N newly constructed inside the outer structures 3a and 3b on the north and south sides, is composed of main piles 9, 9, ... and the edge portion 4e of the pressure-resistant plate 4 that remains with a cut surface 35 at the location where the pressure-resistant plate 4 between the main piles 9, 9 existed, as shown in Figure 6.

[0028] Furthermore, the intermediate retaining walls newly constructed on the outside of the east and west outer structural bodies 3c and 3d, that is, the other pair of outer structural bodies 3c and 3d that are opposite each other among the outer perimeter structural bodies 3R, are composed of a pile-and-sheet wall formed by providing horizontal sheet piles 12A between adjacent piles 9A, 9A.

[0029] Then, the process moves to the final step of retaining wall construction, as shown in Figure 2(d). In the final step of retaining wall construction, after the pressure slab 4 is removed, the ground G is excavated down to position GN, which will be the lowest point of the newly constructed building 1N, and the lower retaining wall is constructed. In other words, the ground G is excavated down to position GN, which will be the lowest point of the new building 1N, at a deeper ground level than where the bottom surface of the pressure slab 4 of the existing building 1 was located. In the final step of retaining wall construction, the lower retaining walls 23 on the north and south sides and the lower retaining walls on the east and west sides are constructed by installing horizontal sheeting between the main piles 9, 9 that are exposed by the excavation, and these lower retaining walls 23 on the north and south sides and the lower retaining walls on the east and west sides are connected. As a result, lower retaining walls (main pile horizontal sheeting walls) are constructed on the east, west, north, and south sides at a position below the pressure slab 4.

[0030] As described above, as shown in Figures 2(d) and 3(d), new retaining walls 2N, 2N are constructed inside the north and south outer structures 3a, 3b, that is, one pair of opposing outer structures 3a, 3b. Also, as shown in Figure 3(d), new retaining walls 2M, 2M are constructed outside the east and west outer structures 3c, 3d, that is, the other pair of opposing outer structures 3c, 3d, and the location where the existing retaining walls 2E, 2E were located.

[0031] Thus, the retaining wall 2N newly constructed inside the outer structural members (long-side outer structural members) 3a, 3b of the underground portion 1U of the existing building 1 by the retaining wall construction method according to Embodiment 1 is composed of an upper retaining wall 21, an intermediate retaining wall 22, and a lower retaining wall 23. Specifically, the retaining wall 2N comprises an upper retaining wall 21 provided above the location where the pressure-resistant slab 4 of the underground portion 1U was located, an intermediate retaining wall 22 provided at the location where the pressure-resistant slab 4 was located, and a lower retaining wall 23 provided below the location where the pressure-resistant slab 4 was located.

[0032] The upper retaining wall 21 and the lower retaining wall 23 are composed of a pile-and-sheet wall formed by a plurality of main piles 9,9,... and horizontal sheet piles 12 installed between adjacent main piles 9,9 separated by a predetermined interval. The plurality of main piles 9,9,... are main piles 9 installed so as to penetrate a plurality of main pile through-holes 5,5,... formed in the pressure slab 4 at predetermined intervals along the boundary 34 in the vicinity of the boundary between the outer structure 3a,3b of the underground portion 1U and the pressure slab 4. The intermediate retaining wall 22 is composed of a plurality of main piles 9,9,... installed at predetermined intervals and the cut surface 35 of the edge 4e of the pressure slab 4 that remains after the pressure slab 4 is separated between adjacent main piles 9,9 separated by a predetermined interval. Furthermore, the cut surface 35 of the edge 4e of the pressure-resistant plate 4 is composed of the inner surfaces of a plurality of core-punching holes 5b, 5b, ... formed to be continuous with the pressure-resistant plate 4.

[0033] As described above, the retaining wall 2N newly constructed inside the outer structural elements 3a and 3b of the underground portion 1U of the existing building 1 using the retaining wall construction method according to Embodiment 1 has been configured such that the work of installing the horizontal sheeting 12 can be omitted when constructing the intermediate retaining wall 22. In other words, the intermediate retaining wall 22 is constructed by performing the pressure slab separation step, thus reducing the labor required to install the horizontal sheeting 12 and enabling labor savings in the construction of the new retaining wall 2N inside the outer structural elements 3a and 3b.

[0034] Then, after the newly constructed retaining walls 2N and 2M are built, the new building 1N will be constructed inside the newly constructed retaining walls 2N and 2M (see Figures 2(d) and 3(d)).

[0035] According to the retaining wall construction method of Embodiment 1, the demolition work is carried out to dismantle the underground portion 1U of the existing building 1, leaving the outer perimeter frame 3R and the pressure slab 4 intact, and then the new retaining walls 2N and 2M are constructed, making the demolition work more efficient. In addition, in Embodiment 1, since the retaining walls 2N and 2N are constructed on the inside of one pair of opposing outer frames (outer frames on the long side) 3a and 3b of the outer perimeter frame 3R, the cutting and removal work of the pressure slab 4 using a core drill can be carried out safely. Furthermore, in the existing building 1, the lateral pressure of the ground G is supported by the outer perimeter frame 3R, and the outer perimeter frame 3R is supported by the pressure slab 4, so when removing the pressure slab 4, it is necessary to install a retaining wall on the inside or outside of the outer perimeter frame 3R. According to Embodiment 1, since new retaining walls 2N and 2M that resist lateral pressure are constructed before the removal of the pressure-resistant slab 4, the cutting and removal work of the pressure-resistant slab 4 can be carried out safely. In addition, by forming multiple core-punched holes 5b, the pressure-resistant slab 4 is separated from the outer structure 3a and 3b, and the cut surface 35 of the remaining edge 4e of the pressure-resistant slab 4 functions as part of the new retaining wall 2N, thus reducing the labor required to construct the retaining wall 2N. Furthermore, since the main pile penetration holes 5 in the pressure-resistant slab 4 and the cut surface 35 of the edge 4e of the pressure-resistant slab 4 are formed by core-punching holes using a core-punching drill, the impact of noise and vibration on the surrounding area can be reduced.

[0036] Embodiment 2 In Embodiment 1, an example was given in which, in a narrow site with limited space around the existing building 1, the process of forming the main pile penetration holes 5 in the pressure-resistant slab 4 and the cut surface 35 of the edge 4e of the pressure-resistant slab 4 is carried out using a core drill to minimize noise and vibration to the neighboring area. However, if there is sufficient space around the existing building 1 to set up heavy machinery and the site conditions are such that vibration to the neighboring area is minimal, the drilling work in the pressure-resistant slab 4 may be carried out using heavy machinery such as a rock auger.

[0037] Embodiment 3 Furthermore, in Embodiment 1, a work platform 8 was formed to improve work efficiency when the site surrounding the existing building 1 is a narrow, cramped space. However, work may be performed without forming a work platform 8. For example, if the site conditions allow for sufficient space to set up heavy machinery around the existing building 1, the work platform 8 may not be formed. [Explanation of Symbols]

[0038] 1 Existing building 1U Underground portion of an existing building 2N Newly constructed retaining wall 3a,3b,3c,3d outer frame 4 Pressure-resistant plate 4e Edge of pressure-resistant plate 5. Main pile penetration hole 5b Core drilling hole 9 Main stake 12 Horizontal sheet piles 21 Upper retaining wall 22 Intermediate retaining wall 23 Lower retaining wall 35. Cut surface of the edge of the pressure-resistant plate 214 The boundary between the outer structure and the pressure-resistant slab.

Claims

1. In the reconstruction of a building, a retaining wall is newly constructed on the inside of the outer structure of the underground portion of the existing building. The upper retaining wall was constructed above the location where the pressure-resistant slab in the underground section was located, An intermediate retaining wall was installed in the location where the pressure-resistant slab was located, A lower retaining wall was constructed below the location where the pressure-resistant slab was located, Equipped with, The upper retaining wall and the lower retaining wall are composed of a pile-and-sheet wall formed in the vicinity of the boundary between the outer structure of the underground portion and the pressure-resistant slab, with multiple main piles installed so as to penetrate multiple main pile through-holes formed in the pressure-resistant slab at predetermined intervals along the boundary, and horizontal sheet piles installed at predetermined intervals between adjacent main piles. The intermediate retaining wall is characterized by comprising a plurality of main piles installed at predetermined intervals and the cut surface of the edge of the pressure-resistant plate remaining after the pressure-resistant plate has been separated between adjacent main piles at predetermined intervals.

2. The retaining wall according to claim 1, characterized in that the cut surface of the edge of the pressure-resistant slab is composed of the inner surfaces of a plurality of core-punched holes formed in a continuous manner with the pressure-resistant slab using a core-punching drill.

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