How to build a building foundation

Abstract

To provide a technology shortened in a construction period, compared to a case of constructing a ground improvement wall after an existing underground skeleton outer wall inside is backfilled with back filling material.SOLUTION: The construction method of a building foundation comprises steps of: constructing one recycled crushed stone layer by laying the recycled crushed stone inside an underground skeleton outer wall; kneading an improving object part in the one recycled crushed stone layer by adding a solidification material to the improving object part in the one recycled crushed stone layer; constructing another recycled crushed stone layer by laying the recycled crushed stone on the one recycled crushed stone layer; and kneading the improving object part in another recycled crushed stone layer with at least a part of the improving object part in the one recycled crushed stone layer, by adding the solidification material to the improving object part in the other recycled crushed stone.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for constructing a building foundation. [Background technology]

[0002] The building foundation structure described in Patent Document 1 has an underground skeleton outer wall and a ground improvement body wall constructed in backfill material that backfills the inside of the underground skeleton outer wall. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-44493 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional technology, ground improvement walls are constructed by backfilling the inside of the existing underground outer wall with backfill material, and then wrapping ground improvement piles in the backfill using a mechanical mixing method, etc. This requires the use of large heavy machinery such as a pile driver and medium-sized general-purpose heavy machinery such as a backhoe, which lengthens the construction period.

[0005] The object of the present disclosure is to provide a technology that can shorten construction time compared to constructing a ground improvement wall after backfilling the inside of an existing underground structure exterior wall with backfill material. [Means for solving the problem]

[0006] The method for constructing a building foundation according to the first embodiment is a method for constructing a building foundation including a ground improvement wall by stacking recycled crushed stone in multiple layers on the inside of the outer wall of an existing underground structure, and is characterized by including the steps of: laying recycled crushed stone on the inside of the outer wall of the underground structure to construct one recycled crushed stone layer; adding a solidification material to the portion to be improved in the one recycled crushed stone layer and mixing the portion to be improved in the one recycled crushed stone layer; laying recycled crushed stone on top of the one recycled crushed stone layer to construct another recycled crushed stone layer; and adding a solidification material to the portion to be improved in the other recycled crushed stone layer and mixing the portion to be improved in the other recycled crushed stone layer with at least a portion of the portion to be improved in the one recycled crushed stone layer.

[0007] According to the first aspect of the present invention, a building foundation including a ground improvement wall is constructed by stacking multiple layers of recycled crushed stone inside the outer wall of an existing underground structure. When mixing the target area of ​​a recycled crushed stone layer on top of another recycled crushed stone layer, the target area of ​​the other recycled crushed stone layer is mixed with at least a portion of the target area of ​​the first recycled crushed stone layer. This results in a vertically integrated ground improvement wall.

[0008] In this way, by stacking recycled crushed stone in multiple layers and constructing a building foundation including a ground improvement wall, the building foundation can be constructed using medium-sized general-purpose heavy machinery such as a backhoe without using a pile driver. This shortens the construction period compared to constructing a ground improvement wall after backfilling the inside of the existing underground outer wall with backfill material.

[0009] The method for constructing a building foundation according to the second aspect is a method for constructing a building foundation including a ground improvement wall by stacking recycled crushed stone in multiple layers on the inside of the outer wall of an existing underground structure, and is characterized by including the steps of: laying recycled crushed stone on the inside of the outer wall of the underground structure to construct one recycled crushed stone layer; adding a solidification material to the portion to be improved in the one recycled crushed stone layer and mixing the portion to be improved in the one recycled crushed stone layer; laying recycled crushed stone on top of the one recycled crushed stone layer to construct another recycled crushed stone layer; adding a solidification material to the portion to be improved in the other recycled crushed stone layer and mixing the portion to be improved in the other recycled crushed stone layer; and constructing a stopper between the portion to be improved in the one recycled crushed stone layer and the portion to be improved in the other recycled crushed stone layer.

[0010] According to the second aspect, recycled crushed stone is piled up in multiple layers inside the outer wall of an existing underground structure to construct a building foundation including a ground improvement wall. Then, a stopper is installed between the improvement target area in one recycled crushed stone layer and the improvement target area in another recycled crushed stone layer. This results in the construction of a ground improvement wall that is integrated vertically.

[0011] In this way, by stacking recycled crushed stone in multiple layers and constructing a building foundation including a ground improvement wall, the building foundation can be constructed using medium-sized general-purpose heavy machinery such as a backhoe without using a pile driver. This shortens the construction period compared to constructing a ground improvement wall after backfilling the inside of the existing underground outer wall with backfill material.

[0012] The building foundation construction method of the third aspect is the building foundation construction method described in the second aspect, characterized in that in the step of constructing the shear stopper, reinforcing bars are constructed to straddle the improvement target area in the one recycled crushed stone layer and the improvement target area in the other recycled crushed stone layer.

[0013] According to the third aspect, in the step of constructing the shear stopper, reinforcing bars are constructed to straddle the improvement target portion in one recycled crushed stone layer and the improvement target portion in another recycled crushed stone layer, thereby mechanically preventing the improvement target portion in one recycled crushed stone layer from shifting from the improvement target portion in the other recycled crushed stone layer. [Effects of the Invention]

[0014] According to the present disclosure, construction time can be shortened compared to when the inside of the existing underground structure exterior wall is backfilled with backfill material and then a ground improvement wall is constructed. [Brief explanation of the drawings]

[0015] [Figure 1] This is a process diagram showing the process of constructing the lower recycled crushed stone layer in the method for constructing a building foundation according to the first embodiment of the present disclosure. [Figure 2] This is a process diagram showing the process of constructing the upper recycled crushed stone layer in the building foundation construction method according to the first embodiment of the present disclosure. [Figure 3] This is a process diagram showing the process of constructing the final layer, a recycled crushed stone layer, in the method for constructing a building foundation according to the first embodiment of the present disclosure. [Figure 4] 1 is a plan view showing a building foundation in a building foundation construction method according to a first embodiment of the present disclosure. FIG. [Figure 5] FIG. 10 is a process diagram showing the process of constructing the final recycled crushed stone layer in the building foundation construction method according to the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment Hereinafter, a method for constructing a building foundation according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. All drawings used in the following description are schematic. The dimensional relationships between elements, the ratios of elements, etc. shown in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional relationships between elements, the ratios of elements, etc. do not necessarily correspond between multiple drawings. In addition, arrow H shown in the drawings indicates the up-down direction (vertical direction) of the foundation, arrow W indicates the width direction (horizontal direction) of the foundation, and arrow D indicates the depth direction of the foundation.

[0017] The method for constructing a building foundation according to the first embodiment is a method for constructing a new building foundation (supporting ground) by backfilling the inside of an existing underground skeleton exterior wall 100 with demolition debris and recycled crushed stone (hereinafter referred to as "recycled crushed stone"). This new building foundation can be reused, for example, as the building foundation of a newly constructed building. Recycled crushed stone is an example of backfill material.

[0018] (Building foundation construction method) The existing underground skeleton outer wall 100 is made of reinforced concrete and buried in the ground 110, and as shown in Figures 1 and 4, is concave and has a rectangular shape extending in the depth direction of the foundation when viewed from above. The upper end surface of the underground skeleton outer wall 100 and the upper surface of the ground 110 are at the same height.

[0019] In this method for constructing a building foundation, a building foundation including a ground improvement wall is constructed by stacking recycled crushed stone in multiple layers inside the underground skeleton outer wall 100. For example, the inside of the underground skeleton outer wall 100, which is 10 m high, is divided into layers 1 m to 2 m thick to construct a building foundation.

[0020] First, as shown in Fig. 1, recycled crushed stone is laid inside the outer wall 100 of the underground structure to construct a recycled crushed stone layer 10a. Specifically, a backhoe 80, which is a general-purpose heavy machine, is used to lay and level the recycled crushed stone inside the outer wall 100 of the underground structure. Then, the backhoe 80 is caused to travel over the top surface of the recycled crushed stone layer 10a, and the leveled surface of the recycled crushed stone layer 10a is compacted by the caterpillar 82 of the backhoe 80.

[0021] Next, a solidification material is added to the improvement target portion 12a in the recycled crushed stone layer 10a, and the improvement target portion 12a is mixed (stirred) using a basket 80a of a backhoe 80. Examples of solidification materials that can be used include cement powder, cement milk, and fluidized treated soil. As shown in FIG. 4, the improvement target portion 12a is formed so as to divide the interior of the underground structure outer wall 100 into three equal parts in the depth direction and into two equal parts in the width direction. In this way, the improvement target portion 12a is formed in a lattice pattern. The ends of the improvement target portion 12a are in contact with the wall surface of the underground structure outer wall 100.

[0022] Next, as shown in Figure 2, recycled crushed stone is laid inside the outer wall 100 of the underground structure to form recycled crushed stone layer 10b. Specifically, a backhoe 80, which is a general-purpose heavy machine, is used to lay and level the recycled crushed stone on the top surface of recycled crushed stone layer 10a. Then, by running the backhoe 80 over the top surface of recycled crushed stone layer 10b, the caterpillar 82 of the backhoe 80 rolls and compacts the leveled surface of recycled crushed stone layer 10b.

[0023] Next, a solidification material is added to the improvement target portion 12b in the recycled crushed stone layer 10b, and the improvement target portion 12b is mixed with at least a portion of the improvement target portion 12a in the recycled crushed stone layer 10a using the basket 80a of the backhoe 80. By mixing the improvement target portion 12b with at least a portion of the improvement target portion 12a in the recycled crushed stone layer 10a in this manner, the improvement target portion 12a and the improvement target portion 12b are integrated.

[0024] Furthermore, by repeating the above steps, recycled crushed stone layer 10c including improvement target portion 12c, recycled crushed stone layer 10d including improvement target portion 12d, recycled crushed stone layer 10e including improvement target portion 12e, recycled crushed stone layer 10f including improvement target portion 12f, and recycled crushed stone layer 10g including improvement target portion 12g are constructed in this order, as shown in Figure 3. Note that if recycled crushed stone layers 10a, 10b, 10c, 10d, 10e, 10f, and 10g are not particularly distinguished from each other, the final letters may be omitted. Also, if improvement target portions 12a, 12b, 12c, 12d, 12e, 12f, and 12g are not particularly distinguished from each other, the final letters may be omitted.

[0025] Then, by vertically integrating the improvement target portions 12a, 12b, 12c, 12d, 12e, 12f, and 12g, a lattice-shaped ground improvement wall 14 is constructed, as shown in Figures 3 and 4. Furthermore, by spreading the top layer of recycled crushed stone evenly, a building foundation including the ground improvement wall 14 is constructed.

[0026] (summary) As described above, in the building foundation construction method of this embodiment, a building foundation is constructed by stacking recycled crushed stone layers 10 in multiple layers inside an existing underground skeleton exterior wall 100. Similarly, a ground improvement wall 14 is constructed by stacking improvement target sections 12 in multiple layers. Here, when mixing the improvement target sections 12 in the upper layer, at least a portion of the improvement target sections 12 in the lower layer is mixed together, thereby integrating the improvement target sections 12 in the vertical direction. In this way, by constructing a building foundation including the ground improvement wall 14, work can be performed using only a backhoe 80.

[0027] On the other hand, in conventional methods for constructing building foundations, the inside of the existing underground structure exterior wall is completely backfilled with recycled crushed stone using a backhoe or similar tool, and then a ground improvement wall is constructed in the backfilled ground using a pile driver using a mechanical mixing method or similar.

[0028] As described above, conventional building foundation construction methods require the use of heavy machinery such as a pile driver and a backhoe. On the other hand, the building foundation construction method of this embodiment allows the building foundation to be constructed using only the backhoe 80. Therefore, the building foundation construction method of this embodiment can shorten the construction period. In other words, the building foundation construction method of this embodiment can shorten the construction period compared to the case where the inside of the existing underground skeleton exterior wall is backfilled with recycled crushed stone and then a ground improvement wall is constructed.

[0029] Furthermore, shortening the construction period can reduce construction costs. Furthermore, in the conventional method for constructing a building foundation, the leveled surface of the recycled crushed stone layer 10 is compacted by the caterpillar 82 of the backhoe 80. This eliminates the need for a dedicated heavy machine for compaction.

[0030] In addition, in the building foundation construction method of this embodiment, the ground improvement body walls 14 are constructed in a lattice pattern while in contact with the wall and bottom surfaces of the underground skeleton outer wall 100. This suppresses shear deformation that occurs in the backfilled ground during an earthquake, and prevents the ground from liquefying.

[0031] Second Embodiment Next, a method for constructing a building foundation according to a second embodiment will be described with reference to Fig. 5. Note that, with regard to the second embodiment, differences from the first embodiment will be mainly described.

[0032] In the method for constructing a building foundation according to the first embodiment, when mixing the improvement target portion 12 of the upper layer, at least a portion of the improvement target portion 12 of the lower layer is mixed together. However, in the method for constructing a building foundation according to the second embodiment, when mixing the improvement target portion 12 of the upper layer, the improvement target portion 12 of the lower layer is not mixed. In other words, only the improvement target portion 12 of each layer is mixed for each recycled crushed stone layer 10.

[0033] Furthermore, in the second embodiment of the building foundation construction method, as shown in Figure 5, steel bars 30 are installed to prevent slippage between the improvement target portion 12 in the upper recycled crushed stone layer 10 and the improvement target portion 12 in the lower recycled crushed stone layer 10.

[0034] This makes it possible to prevent misalignment between the upper and lower improvement target areas 12, even if the upper recycled crushed stone layer 10 is constructed on or after the day after the lower recycled crushed stone layer 10 is constructed.

[0035] Although the present disclosure has been described in detail with respect to specific embodiments, it will be apparent to those skilled in the art that the present disclosure is not limited to such embodiments and that various other embodiments are possible within the scope of the present disclosure. For example, in the first embodiment, in all layers, when mixing the improvement target portion 12 of the upper layer, at least a portion of the improvement target portion 12 of the lower layer is mixed together. However, this does not have to be done in all layers. For example, when mixing the improvement target portion 12d of the recycled crushed stone layer 10d, at least a portion of the improvement target portion 12c of the lower layer may be mixed together.

[0036] Furthermore, in the second embodiment described above, reinforcing bars 30 were installed in all layers so as to straddle the improvement target section 12 in the upper layer and the improvement target section 12 in the lower layer, but this does not have to be done in all layers; for example, reinforcing bars 30 may be installed so as to straddle only the improvement target section 12d and the improvement target section 12c.

[0037] Furthermore, although not specifically explained in the above embodiment, reinforcing bars 30 are used to prevent misalignment between the lower layer improvement target portion 12 and the upper layer improvement target portion 12 only when the upper layer recycled crushed stone layer 10 is constructed on or after the day after the lower layer recycled crushed stone layer 10 is constructed, and in other cases, at least a portion of the lower layer improvement target portion 12 may be mixed together when mixing the upper layer improvement target portion 12.

[0038] Furthermore, in the first and second embodiments, examples have been shown in which the soil improvement body walls 14 are arranged in a lattice pattern, but the arrangement is not particularly limited to a lattice pattern, and may be, for example, an X-shape.

[0039] In addition, in the above first and second embodiments, the inside of the existing underground structure outer wall 100 was backfilled with demolition debris and recycled crushed stone (hereinafter referred to as "recycled crushed stone"), but it may also be backfilled with, for example, sand, gravel, clay, etc.

[0040] In the second embodiment, the reinforcing bars 30 are used to prevent misalignment between the lower and upper improvement target portions 12, but misalignment can be prevented by water tightening after improving the joints. Specifically, when the lower improvement target portion 12 is constructed and compacted by the caterpillar 82 of the backhoe 80, water may be poured in to perform water tightening.

[0041] Furthermore, in the second embodiment, reinforcing bars 30 are used to prevent misalignment between the improvement target portion 12 in the lower layer and the improvement target portion 12 in the upper layer, but for example, a backfilling method that controls the Dc value may be adopted only when backfilling the vicinity of a pouring joint. Here, the Dc value is the degree of compaction, and is a value calculated by the following formula (1), where the dry density ρd of the compacted soil measured on site is "D1" and the maximum dry density ρmax obtained from a compaction test is "D2". Dc(%)=(D1 / D2)×100 (1)

[0042] Although not specifically described in the above embodiment, there is a conventional construction method that does not use a solidifying agent. Specifically, this construction method controls the rolling method when backfilling with recycled crushed stone, and controls the backfilled ground to reach a certain density or higher. In this construction method, the degree of compaction Dc is generally used. With this construction method, the degree of compaction obtained varies depending on the compacting machine, the thickness of the spread material, and the number of compactions, so the construction method must be selected comprehensively, taking into account the yard of the construction site, construction period, and cost. Also, the compaction capacity of a compaction machine is higher with large machines such as vibratory rollers, while small machines such as plate compactors are small. For this reason, when backfilling in narrow construction areas such as existing pits or high foundation beams, it is not possible to use large compaction machines, and it may be difficult to achieve a degree of compaction above the control value. Compared to this method of compacting recycled crushed stone when backfilling, the configuration of the present application makes it possible to increase the thickness of the material spread, and furthermore, there is no need to use large compaction machinery even if the construction site is narrow. [Explanation of symbols]

[0043] 10 Recycled crushed stone layer 10a Reclaimed crushed stone layer (an example of a reclaimed crushed stone layer) 10b Recycled crushed stone layer (an example of another recycled crushed stone layer) 12 Improvement target area 12a Improvement target area 12b Improvement target area 14 Ground improvement wall 30 Reinforced concrete 100 Underground framework outer wall 110 Ground

Claims

1. A method for constructing a building foundation including a ground improvement wall by stacking recycled crushed stone in multiple layers on the inside of an existing underground structure exterior wall, A step of laying recycled crushed stone on the inside of the outer wall of the underground structure to construct one recycled crushed stone layer; A step of adding a solidification material to the improvement target portion in the one recycled crushed stone layer and kneading the improvement target portion in the one recycled crushed stone layer; A step of laying recycled crushed stone on the first recycled crushed stone layer to construct another recycled crushed stone layer; A step of adding a solidification material to the improvement target portion in the other recycled crushed stone layer and kneading the improvement target portion in the other recycled crushed stone layer with at least a portion of the improvement target portion in the one recycled crushed stone layer; Methods for constructing building foundations, including:

2. A method for constructing a building foundation including a ground improvement wall by stacking recycled crushed stone in multiple layers on the inside of an existing underground structure exterior wall, A step of laying recycled crushed stone on the inside of the outer wall of the underground structure to construct one recycled crushed stone layer; A step of adding a solidification material to the improvement target portion in the one recycled crushed stone layer and kneading the improvement target portion in the one recycled crushed stone layer; A step of laying recycled crushed stone on the first recycled crushed stone layer to construct another recycled crushed stone layer; A step of adding a solidification material to the improvement target portion in the other recycled crushed stone layer and kneading the improvement target portion in the other recycled crushed stone layer; A step of constructing a slip stop between the improvement target portion in the one recycled crushed stone layer and the improvement target portion in the other recycled crushed stone layer; Methods for constructing building foundations, including:

3. In the step of constructing the shear stopper, a reinforcing bar is constructed to straddle the improvement target portion in the one recycled crushed stone layer and the improvement target portion in the other recycled crushed stone layer. The method for constructing a building foundation according to claim 2.

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