Building underground structures and design methods for building underground structures

Abstract

The objective is to provide a building's underground structure and a design method for such a structure that can reduce the diameter and number of piles. [Solution] A building's underground structure 10 and a method for designing a building's underground structure, characterized by comprising: an underground exterior wall 3b constituting the underground portion 3 of the building; a soil-cement wall 6 provided adjacent to the outside of the underground exterior wall 3b; a plurality of H-shaped steel beams 7, each with one flange 7a in contact with the outer surface 3c of the underground exterior wall 3b and spaced horizontally apart from each other, arranged inside the soil-cement wall 6 to form an underground wall 5 together with the soil-cement wall 6; recesses 5a provided in the underground wall 5 between adjacent flanges 7a and opening toward the outer surface 3c of the underground exterior wall 3b; and protrusions 3d provided integrally with the outer surface 3c of the underground exterior wall 3b, protruding from the outer surface 3c and engaging with the recesses 5a.

Description

[[TECHNICAL FIELD]]

[0001] The present invention relates to an underground structure of a building and a design method for an underground structure of a building. [[BACKGROUND ART]]

[0002] For example, as a building such as an office building, a structure having an underground portion and supported by piles provided in the ground is known (see, for example, Patent Document 1).

[0003] Conventionally, when designing piles for a building having such an underground portion, it has been common practice to evaluate only the underground portion of the building as a resistance element, calculate the spring and yield strength in the embedding effect of the underground portion of the building into the ground, and set the diameter and number of piles using the calculation results. [[PRIOR ART DOCUMENTS]] [[PATENT DOCUMENTS]]

[0004] [[Patent Document 1]] Japanese Unexamined Patent Application Publication No. 2018-145775 [[SUMMARY OF THE INVENTION]] [[Problems to be Solved by the Invention]]

[0005] As a building having an underground portion, there is known one having an underground structure in which an underground wall (SMW wall) in which a plurality of H-shaped steels are arranged inside a soil cement wall formed of soil cement is constructed as an earth retaining by the SMW construction method, after excavating the ground inside the underground wall, the underground portion of the building is constructed in the excavated portion.

[0006] Even in buildings constructed using the SMW construction method, the diameter and number of piles are set by evaluating only the underground portion of the building as a resistance element. However, in such buildings, there is a demand for reducing the load borne by piles to reduce the diameter and number of piles, and in this respect, there is room for improvement in the underground structure of buildings and the design method for underground structures of buildings.

[0007] This invention was made in view of the above-mentioned problems, and its purpose is to provide a building's underground structure and a method for designing a building's underground structure that can reduce the diameter and number of piles. [Means for solving the problem]

[0008] The underground structure of the building of the present invention is (1) The structure is characterized by comprising: an underground exterior wall constituting the underground portion of a building; a soil-cement wall section provided adjacent to the outside of the underground exterior wall; a plurality of H-shaped steel beams, each abutting the outer surface of the underground exterior wall at one flange and arranged inside the soil-cement wall section at horizontal intervals from each other to form an underground wall together with the soil-cement wall section; recesses provided in the underground wall between adjacent flanges and opening toward the outer surface of the underground exterior wall; and protrusions provided integrally with the outer surface of the underground exterior wall and protruding from the outer surface to engage with the recesses.

[0009] (2) The underground structure of the building described in (1) above preferably has a plurality of recesses in the underground wall corresponding to the space between all adjacent flanges, and a plurality of protrusions in the underground outer wall corresponding to each of the recesses.

[0010] (3) In the underground structure of the building described in (1) or (2) above, it is preferable that the recess and the protrusion each have a rectangular cross-section perpendicular to the vertical direction.

[0011] The present invention's method for designing the underground structure of a building is: (4) The underground structure of a building having an underground exterior wall constituting the underground portion of the building, a soil-cement wall portion provided adjacent to the outside of the underground exterior wall, a plurality of H-shaped steels each abutting the outer surface of the underground exterior wall at one flange, and arranged inside the soil-cement wall portion at horizontal intervals from each other to form an underground wall together with the soil-cement wall portion, recesses provided in the underground wall between adjacent flanges and opening toward the outer surface of the underground exterior wall, and protrusions provided integrally with the outer surface of the underground exterior wall and protruding from the outer surface to engage with the recesses, is characterized in that horizontal forces are transmitted between the underground exterior wall and the underground wall via the recesses and the protrusions. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a building's underground structure and a method for designing a building's underground structure that can reduce the diameter and number of piles. [Brief explanation of the drawing]

[0013] [Figure 1] This is a front view cross-sectional view of a building equipped with an underground structure according to one embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view of the building from the side. [Figure 3] This is a cross-sectional view along line AA in Figure 1. [Figure 4] This is an enlarged cross-sectional view showing an expanded area B in Figure 3. [Figure 5] This is a cross-sectional view along the CC line in Figure 3. [Figure 6] This is a cross-sectional view along the DD line in Figure 3. [Modes for carrying out the invention]

[0014] The following describes in detail, with reference to the drawings, a building's underground structure and a design method for such a structure according to one embodiment of the present invention.

[0015] The building 1 shown in Figs. 1 to 3 can be used as, for example, an office building, and has an above-ground portion 2 and an underground portion 3. Note that in Figs. 1 to 3, the description of the internal structure of the building 1 is omitted.

[0016] The above-ground portion 2 is a portion of the building 1 constructed above the ground 4. The structure and the number of floors of the above-ground portion 2 are not particularly limited. The underground portion 3 is a portion constructed inside the ground 4, that is, in the ground. The underground portion 3 is made of reinforced concrete, and has a bottom wall 3a and an underground outer wall 3b. The underground portion 3 may be a portion constituting an underground floor of the building 1, or may be only a foundation portion having no underground floor. The number of floors of the underground portion 3 is not particularly limited.

[0017] An underground structure 10 of a building according to the embodiment of the present invention comprises the underground outer wall 3b constituting the underground portion 3 of the building 1, and an underground wall 5 provided in the ground.

[0018] As shown in Figs. 1 and 2, in the present embodiment, the underground wall 5 extends to a position deeper than the underground portion 3 such that the lower end position thereof is located below the bottom wall 3a of the underground portion 3 of the building 1. Further, as shown in Fig. 3, in the present embodiment, the underground wall 5 is configured as an annular wall that surrounds the entire circumference of the underground portion 3 of the building 1.

[0019] As shown in Fig. 4, the underground wall 5 includes a soil cement wall portion 6 and a plurality of H-shaped steels 7.

[0020] The soil cement wall portion 6 constitutes a wall-shaped main body portion of the underground wall 5, and is provided adjacent to the outside of the underground outer wall 3b of the building 1. The soil cement wall portion 6 is formed of soil cement obtained by mixing earth and sand with cement slurry.

[0021] Multiple H-shaped steel beams 7 are members that are placed inside the soil-cement wall section 6 to reinforce the soil-cement wall section 6. Each of the multiple H-shaped steel beams 7 has one flange 7a positioned on the side of the underground outer wall 3b, a web 7b integrally connected to the flange 7a, and the other flange 7c integrally connected to the end of the web 7b opposite to the flange 7a. Each of the multiple H-shaped steel beams 7 has its flanges 7a and 7b positioned parallel and vertical to the outer surface 3c of the underground outer wall 3b (the surface facing the soil-cement wall section 6), and is placed inside the soil-cement wall section 6 with a horizontal spacing between them (horizontal direction along the outer surface 3c of the underground outer wall 3b). The portion of the soil-cement wall section 6 facing the underground outer wall 3b is flattened, and the surface of one flange 7a of each of the multiple H-shaped steel beams 7 that faces away from the web 7b is exposed from the soil-cement wall section 6. As shown in Figures 4 and 5, one flange 7a of each of the multiple H-shaped steel beams 7 abuts against the outer surface 3c of the underground outer wall 3b on the surface exposed from the soil-cement wall 6. As shown in Figures 1 and 2, the lower ends of the multiple H-shaped steel beams 7 are located below the bottom wall 3a of the underground portion 3 of the building 1, but above the lower ends of the soil-cement wall 6.

[0022] The underground wall 5 with the above configuration is also called an SMW wall and is constructed using the SMW method. That is, as can be seen from Figure 4, before constructing the underground portion 3 of building 1, the ground 4 is excavated to sequentially form multiple holes 8 that partially overlap each other, and H-shaped steel beams 7 are erected in the center of each of these holes 8. Then, cement slurry is poured into these holes 8 and mixed with soil and sand, and then hardened, thereby constructing an underground wall 5 having a soil cement wall section 6 and multiple H-shaped steel beams 7 as a retaining wall. After constructing the underground wall 5, the ground 4 inside the underground wall 5 is excavated, and the underground portion 3 of building 1 is placed in the excavated area, thereby constructing the underground structure 10 of building 1.

[0023] As shown in Figures 1 and 2, piles 20 are installed in the ground 4 beneath the underground portion 3 of the building 1. In this embodiment, six piles 20 are installed, but the number of piles 20 can be changed as appropriate. The piles 20 are joined to the bottom wall 3a of the underground portion 3 of the building 1 at their pile heads. This allows horizontal forces to be transmitted between the underground portion 3 of the building 1 and the piles 20.

[0024] As shown in Figure 4, in the underground structure 10 of the building according to this embodiment, a recess 5a is provided in the underground wall 5, and a protrusion 3d is integrally provided in the underground outer wall 3b that constitutes the underground portion 3 of the building 1. The protrusion 3d engages with the recess 5a, thereby transmitting a horizontal force in the direction along the underground outer wall 3b between the underground portion 3 of the building 1 and the underground wall 5. In other words, a cotter is provided between the underground outer wall 3b and the underground wall 5 by the protrusion 3d and the recess 5a.

[0025] More specifically, the recesses 5a are provided in the underground wall 5 between adjacent flanges 7a and open toward the outer surface 3c of the underground outer wall 3b. In this embodiment, as can be seen from Figure 3, the underground wall 5 is provided with multiple recesses 5a corresponding to the spaces between all adjacent flanges 7a. That is, recesses 5a are provided between all adjacent flanges 7a. As shown in Figure 4, each recess 5a has a rectangular cross-section perpendicular to the vertical direction, and its horizontal width is the same as the distance between adjacent flanges 7a. That is, the horizontally facing sides of adjacent flanges 7a are exposed in the recess 5a. Furthermore, each recess 5a is deep enough to reach the web 7b side of the flange 7a. Moreover, as shown in Figure 6, each recess 5a extends to a depth in the underground wall 5 that corresponds to the lower surface of the bottom wall 3a of the underground portion 3 of the building 1.

[0026] The protrusions 3d are integrally provided on the outer surface 3c of the underground outer wall 3b of the building 1, protruding from the outer surface 3c and engaging with the recesses 5a. In this embodiment, as can be seen from Figure 3, the outer surface 3c of the underground outer wall 3b is provided with multiple protrusions 3d corresponding to each of the multiple recesses 5a, and each protrusion 3d engages with the corresponding recess 5a. As shown in Figure 4, each protrusion 3d has a rectangular cross-section perpendicular to the vertical direction that corresponds to the recess 5a, and its entirety engages or fits into the recess 5a without any gaps. That is, each protrusion 3d abuts against the horizontally facing side of the adjacent flange 7a in the corresponding recess 5a on its side. Also, as shown in Figure 6, each protrusion 3d extends continuously from the upper end to the lower end of the underground outer wall 3b.

[0027] As described above, in the underground structure 10 of the building according to this embodiment, a protrusion 3d integrally provided on the underground outer wall 3b constituting the underground portion 3 of the building 1 engages with a recess 5a provided on the underground wall 5. The horizontal shear resistance generated by the protrusion 3d causes a horizontal force to be transmitted between the underground portion 3 of the building 1 and the underground wall 5 in the direction along the underground outer wall 3b. As a result, the horizontal force applied to the building 1 during an earthquake can be supported not only by the underground portion 3 of the building 1 but also by the underground wall 5. Therefore, the effect of embedding the building 1 into the ground 4 can be evaluated by considering the underground wall 5 as a resistance element in addition to the underground portion 3 of the building 1, and the diameter and number of piles 20 can be set accordingly. This allows for a reduction in the diameter and number of piles 20 compared to when the underground wall 5 cannot be evaluated as a resistance element.

[0028] Furthermore, in the underground structure 10 of the building according to this embodiment, horizontal forces can be transmitted between the underground portion 3 of the building 1 and the underground wall 5 with a simple configuration in which a protrusion 3d integrally provided on the underground outer wall 3b constituting the underground portion 3 of the building 1 is engaged with a recess 5a provided on the underground wall 5, thereby reducing the construction cost of the building 1. That is, as a configuration for transmitting horizontal forces between the underground wall 5 and the underground outer wall 3b of the building 1, a configuration can be considered in which a large number of studs are joined to each flange 7a of a plurality of H-shaped steels 7 constituting the underground wall 5, and concrete is poured so that these studs are embedded to construct the underground outer wall 3b, thereby integrating the underground wall 5 and the underground outer wall 3b of the building 1 via a large number of studs. However, in such a configuration, a large number of studs must be joined to the flange 7a by welding or the like, resulting in a large amount of parts cost and labor required to join the studs. In contrast, the underground structure 10 of the building according to this embodiment can reduce the construction cost of the building 1 without requiring a large amount of parts cost and labor.

[0029] Furthermore, in this embodiment, the underground wall 5 is provided with a plurality of recesses 5a corresponding to the spaces between all adjacent flanges 7a, and the underground outer wall 3b is provided with a plurality of protrusions 3d corresponding to each of the recesses 5a. This allows for more reliable and efficient transmission of horizontal forces along the underground outer wall 3b between the underground portion 3 of the building 1 and the underground wall 5, thereby further enhancing the above effect.

[0030] Furthermore, in this embodiment, the side surfaces of each protrusion 3d are brought into contact with the horizontally facing side surfaces of adjacent flanges 7a in the corresponding recesses 5a. This allows for more efficient transmission of horizontal forces between the protrusion 3d and the flange 7a, thereby further enhancing the above-mentioned effect.

[0031] Furthermore, in this embodiment, since the underground wall 5 is provided so as to surround the entire perimeter of the underground portion 3 of the building 1, horizontal forces in all directions can be transmitted between the underground portion 3 of the building 1 and the underground wall 5.

[0032] A method for designing the underground structure of a building according to one embodiment of the present invention can be used when designing the underground structure 10 of a building with the above configuration.

[0033] In the building underground structure design method according to this embodiment, the underground structure 10 of the building having the above configuration, that is, an underground outer wall 3b constituting the underground portion 3 of the building 1, a soil cement wall 6 provided adjacent to the outside of the underground outer wall 3b, a plurality of H-shaped steels 7 each abutting the outer surface 3c of the underground outer wall 3b at one flange 7a and arranged inside the soil cement wall 6 at horizontal intervals from each other to form an underground wall 5 together with the soil cement wall 6, a recess 5a provided in the underground wall 5 between adjacent flanges 7a and opening toward the outer surface 3c of the underground outer wall 3b, and a protrusion 3d provided integrally with the outer surface 3c of the underground outer wall 3b and protruding from the outer surface 3c and engaging with the recess 5a, is designed so that horizontal forces are transmitted between the underground outer wall 3b and the underground wall 5 via the recess 5a and the protrusion 3d. In other words, the design provides a protrusion 3d and a recess 5a that function as cotters between the underground outer wall 3b and the underground wall 5.

[0034] As a result, in the building's underground structure design method according to this embodiment, the effect of embedding the building 1 into the ground 4 can be evaluated by considering the underground wall 5 as a resistance element in addition to the underground portion 3 of the building 1, and the diameter and number of piles 20 can be set while designing the building 1. Therefore, the diameter and number of piles 20 can be reduced compared to when the building 1 is designed without evaluating the underground wall 5 as a resistance element.

[0035] Furthermore, in the design method for the underground structure of the building according to this embodiment, as described above, the diameter and number of piles 20 can be reduced, thereby reducing the man-hours and material costs involved in constructing the piles 20, and thus reducing the construction cost of the building 1.

[0036] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention.

[0037] For example, in the above embodiment, the cross-sectional shape perpendicular to the vertical direction of the recess 5a and the protrusion 3d is rectangular, but it is not limited to this, and the cross-sectional shape perpendicular to the vertical direction of the recess 5a and the protrusion 3d can be various shapes.

[0038] Furthermore, in the above embodiment, the horizontal width of the recess 5a and the protrusion 3d is the same as the distance between adjacent flanges 7a, but this is not limited to this, and the horizontal width of the recess 5a and the protrusion 3d can be changed as appropriate, as long as the recess 5a and the protrusion 3d can be positioned between adjacent flanges 7a. In other words, it is preferable that the protrusion 3d is in contact with the side surface of the flange 7a, but this is not limited to this.

[0039] Furthermore, in the above embodiment, the recess 5a and the protrusion 3d are configured to extend continuously in areas corresponding to the upper and lower ends of the underground exterior wall 3b of the building 1, respectively. However, the configuration is not limited to this, and they may be provided only in a part of the area between the upper and lower ends of the underground exterior wall 3b, or they may be provided intermittently in the vertical direction throughout the entire area corresponding to the upper and lower ends of the underground exterior wall 3b.

[0040] Furthermore, in the above embodiment, recesses 5a and protrusions 3d are provided between all adjacent flanges 7a, but the invention is not limited to this, and recesses 5a and protrusions 3d may be provided only between some adjacent flanges 7a. [Explanation of Symbols]

[0041] 1. Building 2 Above ground part 3 Underground part 3a Bottom wall 3b Basement outer wall 3c External surface 3D convex part 4 Ground 5 underground wall 5a recess 6. Soil-cement wall section 7 H type steel 7a Flange 7b Web 7c flange 8 holes 10. Building underground structure 20 stakes

Claims

1. The underground exterior wall that makes up the underground portion of the building, A soil-cement wall section provided adjacent to the outside of the aforementioned underground exterior wall, Multiple H-shaped steel beams, each in contact with the outer surface of the underground outer wall at one flange, and positioned horizontally apart from each other within the soil-cement wall section, thereby forming an underground wall together with the soil-cement wall section, A recess is provided in the underground wall between adjacent flanges, and opens toward the outer surface of the underground outer wall, The underground structure of a building is characterized by having a protrusion integrally provided on the outer surface of the underground outer wall, which protrudes from the outer surface and engages with the recess.

2. The underground wall is provided with a plurality of recesses corresponding to the spaces between all adjacent flanges. The underground structure of a building according to claim 1, wherein the underground exterior wall is provided with a plurality of protrusions corresponding to each of the recesses.

3. The underground structure of a building according to claim 1 or 2, wherein the recess and the protrusion each have a rectangular cross-section perpendicular to the vertical direction.

4. The underground exterior wall that makes up the underground portion of the building, A soil-cement wall section provided adjacent to the outside of the aforementioned underground exterior wall, Multiple H-shaped steel beams, each in contact with the outer surface of the underground outer wall at one flange, and positioned horizontally apart from each other within the soil-cement wall section, thereby forming an underground wall together with the soil-cement wall section, A recess is provided in the underground wall between adjacent flanges, and opens toward the outer surface of the underground outer wall, A building's underground structure having a protrusion integrally provided on the outer surface of the underground outer wall, which protrudes from the outer surface and engages with the recess, A method for designing the underground structure of a building, characterized in that horizontal forces are transmitted between the underground exterior wall and the underground wall via the recess and the protrusion.

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