JP7628248B2 - Precast concrete base material for forming a mat foundation, a molding device for molding the precast concrete base material, a method for molding the precast concrete base material using the molding device, and a method for forming a mat foundation using the precast concrete base material - Google Patents

Description

The present invention relates to a precast concrete foundation material for forming a mat foundation, a molding device for forming such a precast concrete foundation material, a method for forming the precast concrete foundation material using such a molding device, and a method for forming a mat foundation using the precast concrete foundation material.

For example, as shown in Patent Documents 1 and 2 below, it has been well known to form a slab foundation using precast concrete foundation materials. A slab foundation has a floor section and a rising section, both of which are made of concrete with reinforcing bars arranged inside. The precast concrete foundation materials shown in Patent Documents 1 and 2 are placed on the outer periphery of the upper surface of the basal concrete that has been formed in advance at the construction site, and mainly form the rising section of the slab foundation. Reinforcing bars are arranged on the basal concrete, and the floor section of the slab foundation is formed by pouring concrete inside the placed precast concrete foundation material and burying the reinforcing bars. The precast concrete foundation materials as described above are formed in a factory with the reinforcing bars already included, and are transported from the factory to the construction site with the reinforcing bars protruding to the outside.

JP 2010-70903 A JP 2011-64047 A

In the case of the precast concrete foundation materials shown in Patent Documents 1 and 2, the reinforcing bars are transported from the factory to the construction site with the reinforcing bars protruding outward, and there is a risk that the protruding reinforcing bars may damage surrounding workers or construction materials during transportation. Furthermore, the weight of the foundation material is heavy, and a large crane is required to move the foundation material, which makes the workability unfavorable. In addition, in the method of forming a mat foundation using the precast concrete foundation materials shown in Patent Documents 1 and 2, it is necessary to pour basing concrete over a wide area before placing the precast concrete foundation material at the construction site, which lengthens the construction period. And in the mat foundation formed using the precast concrete foundation materials shown in Patent Documents 1 and 2, the rising part is made of precast concrete formed in the factory, but the dirt floor part is made of concrete poured at the construction site, so the two are not molded together, and cracks are likely to occur at the boundary between the two. If such cracks occur, the seismic strength will decrease.

The present invention was made in light of the above facts, and its main technical objective is to provide a new precast concrete foundation material for forming slab foundations that is lightweight and can be transported safely, yet maintains sufficient earthquake resistance.

According to the present invention, a precast concrete foundation material that achieves the above-mentioned main technical object is a precast concrete foundation material for forming a mat foundation, which has a bottom wall of a required shape and upright walls that rise upward from the side edges of the bottom wall and form a groove of the same shape as the required shape in a plan view, an opening window that communicates with the groove is formed at the lower end of the upright wall, and the upper surface and end surfaces of the groove formed by the upright walls are open,
A precast concrete foundation material is provided, characterized in that the rising portion of the slab foundation is formed by pouring concrete into the groove .

Preferably, the required shape is a straight line, an L-shape, a T-shape, or a cross shape. A bottomed hole is preferably formed in the upper surface of the bottom wall. Preferably, a through hole penetrating the bottom wall in the vertical direction is formed, and a female thread is formed on the inner peripheral surface of the bottom wall that defines the through hole. In this case, the through hole is preferably formed at the center of gravity of the bottom wall.

A precast concrete base material constructed according to the present invention comprises a fixed base and an inner mold and an outer mold attached to the base, the inner mold protruding upward from the upper surface of the base, and the outer mold consisting of a plurality of plate-shaped outer mold pieces connected to the base via hinge means, and each of the plurality of outer mold pieces can freely rotate between a molding position in which the inner surface is close to the outer surface of the inner mold and a demolding position separated from the outer surface of the inner mold, and when the outer mold piece is located at the molding position, the upper end position of the outer mold piece is located above the upper end position of the inner mold in the vertical direction, and a bulge portion is formed at a required portion of the inner surface of the outer mold piece that comes into surface contact with the outer surface of the inner mold when it is at the molding position. In this case, the bulging portion has a bulging end surface that is in surface contact with the outer surface of the inner mold when the outer mold piece is in the molding position, and a bulging outer peripheral surface that extends from the outer peripheral edge of the bulging end surface and connects to the inner surface of the outer mold piece, and the bulging outer peripheral surface preferably extends in a direction from the inner surface of the outer mold piece toward the outer surface. The vertical cross-sectional shape of the inner mold is preferably tapered upward.

The method for manufacturing a precast concrete foundation material constructed according to the present invention using the above-mentioned molding device includes a foundation material forming body casting step in which unhardened concrete is poured inside the outer mold when all the outer mold pieces are in the molding position to form a precast concrete foundation material formed body, a demolding preparation step in which all the outer mold pieces are rotated from the molding position to the demolding position after the precast concrete foundation material formed body has hardened, and a demolding step in which the precast concrete foundation material formed body is demolded from the inner mold after the demolding preparation step. In such a method, it is preferable to form the through hole and the female thread in the demolding preparation step, screw a bolt into the through hole from above, and press the upper surface of the inner mold with the tip of the bolt. It is also preferable to form the through hole and the female thread in the demolding preparation step, and screw an eye bolt into the through hole from above.

A method for forming a mat foundation using a precast concrete foundation material constructed according to the present invention preferably includes a foundation material arrangement step in which a plurality of the precast concrete foundation materials are arranged continuously as required on the basal concrete to connect the groove endlessly, a reinforcement arrangement step in which the ends of the slab reinforcement are inserted into the openings after the foundation material arrangement step to arrange the slab reinforcement, and a foundation pouring step in which unhardened concrete is poured from the top surface of the groove after the reinforcement arrangement step. After the reinforcement arrangement step and before the foundation pouring step, an anchor bolt arrangement step is carried out in which an anchor bolt is arranged at the upper end of the precast concrete foundation material, and the anchor bolt is preferably supported by a support straddling the upper end of the precast concrete foundation material.

In the precast concrete foundation material constructed according to the present invention, the rising part of the slab foundation is formed by pouring concrete into the groove at the construction site. In other words, since the rising part of the slab foundation is completed at the construction site, not at the factory where the precast concrete foundation material is formed, the weight of the precast concrete foundation material itself is light. Therefore, according to the precast concrete foundation material constructed according to the present invention, a large crane is not necessarily required to move it, and therefore the workability of the foundation construction is good. Furthermore, since an opening window that communicates with the above-mentioned groove is formed at the lower end of the standing wall, after the precast concrete foundation material is arranged as required at the construction site, the slab reinforcement can be arranged by inserting the end of the slab reinforcement into the opening window. Therefore, there is no need to form the precast concrete foundation material with the reinforcing bar included, and the reinforcing bar does not protrude to the outside during transportation. Therefore, the precast concrete foundation material constructed according to the present invention can be transported safely. Furthermore, according to the method of forming a mat foundation using the precast concrete foundation material constructed according to the present invention, the construction period can be shortened because the basin concrete poured at the construction site is sufficient only in the area where the precast concrete foundation material is placed. Furthermore, in the mat foundation formed using the precast concrete foundation material constructed according to the present invention, the floor area and the rising area are formed integrally without any joints, so cracks are unlikely to occur at the boundary between the floor area and the rising area, and sufficient seismic strength can be maintained.

FIG. 1 is a view showing a linear precast concrete foundation member, which is one of preferred embodiments of the precast concrete foundation member constructed according to the present invention. FIG. 1 is a view showing a single L-shaped precast concrete foundation, which is one of the preferred embodiments of the precast concrete foundation constructed according to the present invention. FIG. 1 is a view showing a single T-shaped precast concrete foundation, which is one of the preferred embodiments of the precast concrete foundation constructed according to the present invention. FIG. 1 is a single view of a cross-shaped precast concrete foundation, which is one of the preferred embodiments of the precast concrete foundation constructed according to the present invention. FIG. 1 is a single view of a cross-shaped precast concrete foundation, which is one of the preferred embodiments of the precast concrete foundation constructed according to the present invention. 1 is a diagram showing the structure of a molding device for molding a precast concrete foundation material constructed according to the present invention. 6 is a diagram showing a method of forming a precast concrete foundation material using the forming device shown in FIG. 5 . FIG. 5 is a plan view showing an example of a state immediately after the completion of a foundation material arrangement process using the various precast concrete foundation materials shown in FIGS. FIG. 8 is an enlarged perspective view of a portion of FIG. 7 . FIG. 4 is an enlarged perspective view showing a portion of the structure immediately after the reinforcement process is completed. FIG. 10 is a diagram showing a basic structure in the state shown in FIG. 9 . FIG. 13 is a schematic diagram showing the foundation structure immediately after the anchor bolt installation process is completed. FIG. 2 is a schematic diagram showing the foundation structure immediately after the foundation pouring process is completed.

As will be explained later with reference to the drawings, the precast concrete foundation material constructed according to the present invention has a bottom wall of the required shape and upright walls that rise upward from the side edges of the bottom wall, and can be formed by a forming device described below. A more detailed explanation will be given below with reference to the attached drawings showing a preferred embodiment of the precast concrete foundation material constructed according to the present invention.

Figure 1 shows a precast concrete foundation material when the required shape is a straight line shape. The precast concrete foundation material shown in Figure 1 is designated by the reference symbol 2a as a straight line precast concrete foundation material, and is to be distinguished from precast concrete foundation materials of other shapes described later. Figures 1(a) to (d) respectively show a perspective view, a plan view, a right side view, and a cross-sectional view along line A-A of the straight line precast concrete foundation material 2a. The straight line precast concrete foundation material 2a has a straight line bottom wall 4a and upright walls 6a-1 and 6a-2 that stand upward from both side edges of the bottom wall 4a. The upper and lower surfaces of the bottom wall 4a are both flat, and four bottomed holes 8a are formed at intervals in the longitudinal direction on the upper surface of the bottom wall 4a. In addition, a through hole 10a that penetrates the bottom wall 4a in the vertical direction is also formed, and a female thread 12a is formed on the inner peripheral surface of the bottom wall 4a that defines the through hole 10a. The through hole 10a is formed at the center of gravity of the bottom wall 4a, and the four bottomed holes 8a are formed, two on each side of the through hole 10a when viewed in the longitudinal direction, and the bottomed holes 8a and the through holes 10a are arranged at equal intervals on the same straight line extending in the longitudinal direction. The upright walls 6a-1 and 6a-2 stand upward from both side edges of the bottom wall 4a extending in the longitudinal direction, and a groove 14a is formed between the upright walls 6a-1 and 6a-2, with its top surface and end surfaces open and extending linearly in the longitudinal direction. The groove 14a has a linear shape and is the same as the required shape described above. As shown in Fig. 1(c), the outer side surfaces 16a of the upright walls 6a-1 and 6a-2 both extend substantially vertically from the upper surface of the bottom wall 4a, while the inner side surfaces 18a of the upright walls 6a-1 and 6a-2 extend from the upper surface of the bottom wall 4a at a slight incline toward the outside, and the thickness of the upright walls 6a-1 and 6a-2 is gradually reduced from the base end toward the extended end. An opening window 20a that communicates with the groove 14a is formed at the base end of the upright wall. As shown in Fig. 1(b) and (c), in the illustrated embodiment, the opening window 20a is expanded from the inner side surface of the upright wall toward the outer side surface. The reason for this will be mentioned later. In the linear precast concrete foundation 2a shown in FIG. 1, the opening window 20a is formed only in the standing wall 6a-1 and not in the standing wall 6a-2, but as described below, the opening window 20a may be formed at the base end of the two standing walls 6a-1 and 6a-2.

Figure 2 shows a precast concrete foundation material when the required shape is an L-shape. The precast concrete foundation material shown in Figure 2 is an L-shaped precast concrete foundation material and is generally indicated by the reference symbol 2b. Figures 2(a) to (d) respectively show a perspective view, a plan view, a right side view, and a cross-sectional view along the line A-A of the L-shaped precast concrete foundation material 2b. The L-shaped precast concrete foundation material 2b has substantially the same configuration as the linear precast concrete foundation material 2a described above except that the required shape is an L-shape, so the same configuration is assigned the reference symbol b to the same number and detailed description thereof is omitted. The L-shaped precast concrete foundation material 2b has two standing walls 6b-1 and 6b-2 that are both L-shaped in plan view, and the opening window 20b is formed only at the lower end of one of the two standing walls 6b-1 and 6b-2. In the L-shaped precast concrete foundation 2b shown in FIG. 2, the opening window 20b is formed in the standing wall 6b-1, but as described below, the opening window 20b may also be formed in the standing wall 6b-2.

Figure 3 shows a precast concrete foundation material when the required shape is a T-shape. The precast concrete foundation material shown in Figure 3 is a T-shaped precast concrete foundation material and is generally indicated by the reference symbol 2c. Figures 3(a) to (d) respectively show a perspective view, a plan view, a front view, and a cross-sectional view along the line A-A of the T-shaped precast concrete foundation material 2c. The T-shaped precast concrete foundation material 2c has substantially the same configuration as the linear precast concrete foundation material 2a described above except that the required shape is a T-shape, so the same configuration is given the reference symbol c with the same numbers and detailed description thereof is omitted. The T-shaped precast concrete foundation material 2c has one standing wall 6c-1 that is linear in plan view and two standing walls 6c-2 and 6c-3 that are L-shaped, and an opening window 20c is formed only at the lower end of the standing walls 6c-2 and 6c-3 as shown by the dashed line in Figure 3(b). In the T-shaped precast concrete foundation 2c shown in FIG. 3, the opening window 20c is not formed in the standing wall 6c-1, but as described below, there are cases where the opening window 20c is also formed in the standing wall 6c-1.

Figures 4-1 and 4-2 show a precast concrete foundation material when the required shape is a cross shape. The precast concrete foundation material shown in Figure 4 is a cross-shaped precast concrete foundation material and is indicated as a whole by the reference symbol 2d. Figures 4-1(a) to 4-2(d) respectively show a perspective view, a plan view, a front view, and a cross-sectional view along line A-A of the cross-shaped precast concrete foundation material 2d. The cross-shaped precast concrete foundation material 2d has substantially the same configuration as the linear precast concrete foundation material 2a described above except that the required shape is a cross shape, so the same configuration is given the reference symbol d with the same number and detailed description thereof is omitted. The cross-shaped precast concrete foundation material 2d has four standing walls 6d-1 to 6d-4 that are L-shaped in plan view, and as shown by the dashed line in Figure 4-1(b), an opening window 20d is formed at the lower end of all the standing walls 6d-1 to 6d-4. One opening window 20d is formed on each side of the upright walls 6d-1 to 6d-4.

Figure 5 shows the structure of a molding device for molding the linear precast concrete foundation material 2a shown in Figure 1 as an example of a molding device for molding a precast concrete foundation material constructed according to the present invention. The molding device, generally designated by the number 22a, has a base 24a fixed on a substantially horizontal surface, and an inner mold 26a and an outer mold 28a attached to the base 24a. The base 24a extends linearly in the depth direction of the paper, and its cross-sectional shape is approximately rectangular. A groove 30a extending linearly in the depth direction of the paper is formed on both side edges in the left-right direction of the upper surface of the base 24a, and the outer surface of the groove 30a viewed in the left-right direction of the paper is open. The inner mold 26a is fixed to the upper surface of the base 24a by an appropriate fixing means. The inner mold 26a also extends linearly in the depth direction of the paper, protrudes upward from the upper surface of the base 24a, and its upper surface is closed flat. In the illustrated embodiment, the vertical cross-sectional shape of the inner mold 26a is a hollow trapezoid tapered toward the top. The outer mold 28a is composed of two plate-shaped outer mold pieces 34a connected to the base 24a via hinge means 32a provided in the groove 30a, and the two outer mold pieces 34a both extend linearly in the depth direction of the paper. As shown in Fig. 5, the two outer mold pieces 34a are arranged on both sides of the inner mold 26a that extends linearly in the depth direction of the paper. Both of the two outer mold pieces 34a can freely rotate between a molding position (position shown by a solid line in Fig. 5) where the inner surface is close to the outer surface of the inner mold 26a and a demolding position (position shown by a two-dot chain line in Fig. 5) where the inner surface is separated from the outer surface of the inner mold 26a. When the outer mold piece 34a is in the molding position, the outer mold piece 34a stands upright substantially perpendicular to the upper surface of the base 24a, and the upper end of the outer mold piece 34a is located above the upper end of the inner mold 26a. Therefore, when all the outer mold pieces 34a are in the molding position, the inner side of the outer mold piece 34a is defined by the inner side of the outer mold piece 34a, the outer side of the inner mold 26a, and the upper surface of the base 24a, and the inner side of the outer mold 28a is defined above the inner mold 26a. Due to the presence of the groove 30a, the inner side of the outer mold piece 34a is sufficiently separated from the outer side of the inner mold 26a at the above-mentioned mold release position. At a required portion of the inner side of the outer mold piece 34, a bulge 39 is formed that comes into surface contact with the outer side of the inner mold 26 when in the molding position. The bulging portion 39 has a rectangular bulging end surface 39a that comes into surface contact with the outer surface of the inner mold 26 when the outer mold piece 34 is in the molding position, and a bulging outer peripheral surface 39b that extends from the outer peripheral edge of the bulging end surface 39a and connects to the inner surface of the outer mold piece 34, and the bulging outer peripheral surface 39b extends in a direction from the inner surface of the outer mold piece 34 toward the outer surface. Although not shown, the molding device 22a also has end molds that are fixed or rotatable relative to the base 24a and come into contact with the end surfaces of the inner mold 26a and the outer mold piece 34a and both end surfaces in the depth direction of the paper to define both end surfaces in the longitudinal direction of the linear precast concrete foundation material 2a.

Next, referring to FIG. 6, the process of forming the linear precast concrete foundation material 2a by the forming device 22a will be described. First, as shown in FIG. 6(a), when all the outer mold pieces 34a are in the forming position, unhardened concrete is poured inside the outer mold 28a to form a linear precast concrete foundation material molded body 2a' (foundation material molded body pouring process). Referring also to FIG. 5, the unhardened concrete is poured not only into the above-mentioned standing wall forming space 36a but also into the bottom wall forming space 38a. The concrete poured into the standing wall forming space 36a and the bottom wall forming space 38a and hardened will later become the standing wall 6a and the bottom wall 4a of the linear precast concrete foundation material 2a, respectively. Therefore, in the concrete poured into the bottom wall forming space 38a and hardened, the part that will later become the bottom wall 4a is called the bottom wall 4a'. As shown in FIG. 6(a), the linear precast concrete foundation material molded body 2a' is molded with the bottom wall 4a' positioned upward. In addition, a bulge 39 is formed at a required portion of the inner surface of the outer mold piece 34, which is in surface contact with the outer surface of the inner mold 26 when in the molding position. This causes no concrete to exist in the portion where the bulge 39 is formed, and an opening window 20a' of the linear precast concrete foundation molding 2a' is formed in this portion. If desired, unhardened concrete may be poured after well-known mesh reinforcement, in which solid rod-shaped reinforcing bars are arranged in a mesh shape, is placed in the upright wall forming space 36a and the bottom wall forming space 38a. In this case, hardened concrete pieces (not shown) are placed on the base 24a in advance, and the mesh reinforcement is placed on the concrete pieces.

Next, after the linear precast concrete foundation molding 2a' has hardened, as shown in FIG. 6(b), all the outer mold pieces 34a are rotated from the molding position to the demolding position to expose the linear precast concrete foundation molding 2a' (mold-release preparation process). At this time, the bulge 39 formed on the outer mold piece 34 is demolded from the linear precast concrete foundation molding 2a'. In the illustrated embodiment, the bulge outer peripheral surface 39b of the bulge 39 formed on the outer mold piece 34 spreads and extends in the direction from the inner surface of the outer mold piece 34 toward the outer surface, so that the bulge 39 can be easily demolded from the upright wall 6'. In the illustrated embodiment, the mold release preparation step further includes forming a through hole 10a' and a female thread 12a' at a required position of the bottom wall 4a' (FIG. 6(c)), and screwing an appropriate bolt 40 into the through hole 10a' from above by rotating it clockwise as viewed from above (FIG. 6(d)), and pressing the upper surface of the inner mold 26a with its tip. At this time, as shown in FIG. 6(e), the tip of the bolt 40 abuts against the upper surface of the inner mold 26a, preventing the bolt 40 from moving downward. However, if the bolt 40 continues to screw while the tip of the bolt 40 abuts against the upper surface of the inner mold 26a, the male thread 41 formed on the bolt 40 and the female thread 12a' formed in the through hole 10a' are screwed together, causing the linear precast concrete foundation molding 2a' to move upward relative to the inner mold 26a. In other words, the linear precast concrete foundation molding 2a' is temporarily released from the inner mold 26a.

After the linear precast concrete foundation molding 2a' is temporarily released from the inner mold 26a, as shown in Fig. 6(f), the bolt 40 is rotated counterclockwise as viewed from above to lower the linear precast concrete foundation molding 2a' toward the inner mold 26a, and the two are abutted again. After that, the bolt 40 is further rotated counterclockwise to unscrew the bolt 40 from the through hole 10a'. Next, as shown in Fig. 6(g), an eye bolt 42 is screwed into the through hole 10a' from above, an appropriate wire 44 is wound around the eye bolt 42, and the linear precast concrete foundation molding 2a' is lifted upward via the eye bolt 42 by a crane (not shown) to release it from the inner mold 26a (release process). At this time, since the linear precast concrete foundation molded body 2a' has already been released once from the inner mold 26a in the mold release preparation process, the linear precast concrete foundation molded body 2a' is smoothly released from the inner mold 26a in the mold release process.

The above describes the molding device 22a for molding the linear precast concrete base material 2a and the method for manufacturing the linear precast concrete base material 2a using the molding device, but the molding devices for manufacturing precast concrete base materials of other shapes (2b to 2d) and the method for manufacturing precast concrete base materials of each shape using the molding device are configured in the same way, so detailed explanations will be omitted. Just to be clear, in the molding device for molding precast concrete base materials of other shapes 2b to 2d whose bottom walls have the required shape, the inner mold is the same as the required shape in a plan view, and the plate-shaped outer mold pieces that make up the outer mold are arranged according to the sides of the required shape.

Next, referring to Figures 7 to 12, the process of forming a mat foundation using the various precast concrete foundation materials 2a to 2d shown in Figures 1 to 4 will be described. Although not shown, first, after performing the well-known root cutting and splitting work as required at the construction site, basing concrete 48 is poured on the outer edge of the earthen floor 46. Then, as shown in Figures 7 and 8, a plurality of various precast concrete foundation materials 2a to 2d are continuously arranged on the basing concrete 48 to connect the grooves 14a to 14d of the precast concrete foundation materials 2a to 2d endlessly (base material arrangement process). Figure 8 is partially omitted for easy understanding. It is preferable to arrange the well-known adjustment mortar 50 between the basing concrete 48 and the precast concrete foundation materials 2a to 2d. In addition, when moving the precast concrete foundation members 2a to 2d, as shown in Fig. 8, it is preferable to screw the eye bolts 42 into the through holes 10a to 10d formed in the bottom plates 4a to 4d from above (from the inside of the grooves 14a to 14d) and hang the eye bolts 42 with an appropriate crane. At this time, since the through holes 10a to 10d are formed at the center of gravity of the bottom walls 4a to 4d, the precast concrete foundation members 2a to 2d can be hung stably in a substantially horizontal state. In the foundation arrangement process, the opening windows 20a to 20d formed in the various precast concrete foundation members 2a to 2d are all arranged on the side of the earth floor 46, and are not arranged on the opposite side of the earth floor 46, that is, on the outside of the building in a plan view. Therefore, in the precast concrete foundation member indicated by the symbol 2A in Fig. 7, unlike the precast concrete foundation member 2a shown in Fig. 1, the opening windows 20a are formed not only in the standing wall 6a-1 but also in the standing wall 6a-2. In addition, in the precast concrete foundation material indicated by the symbol 2B in FIG. 7, unlike the precast concrete 2b shown in FIG. 2, the opening window 20b is formed in the standing wall 6b-2, not in the standing wall 6b-1. Furthermore, in the precast concrete foundation material indicated by the symbol 2C in FIG. 7, unlike the precast concrete 2c shown in FIG. 3, the opening window 20c is formed not only in the standing walls 6c-2 and 6c-3, but also in the standing wall 6c-1.

After the foundation material arrangement process, as shown in Figures 9 and 10, a reinforcing bar arrangement process is carried out in which solid rod-shaped reinforcing bars are arranged. Figure 9 is partially omitted for easy understanding. In the reinforcing bar arrangement process, the ends 54 of the slab bars 52 are inserted into the openings 20a to 20d to arrange the slab bars 52. As can be understood by referring to Figure 10, the ends 54 of the slab bars 52 are bent, and the ends 54 are positioned in the grooves 14a to 14d. In the reinforcing bar arrangement process, vertical bars 56 are arranged in each of the bottomed holes 8a to 8d of the precast concrete foundation materials 2a to 2d, and horizontal bars 58 are also arranged to be fastened to the vertical bars 56 by appropriate fastening means.

After the above-mentioned reinforcing bar arrangement process, an anchor bolt arrangement process is performed in which anchor bolts 60 are arranged at the upper ends of the precast concrete foundation members 2a to 2d. A plurality of anchor bolts 60 are arranged at intervals at the upper ends of the precast concrete foundation members 2a to 2d, and as shown in FIG. 11, the lower ends of each anchor bolt 60 are fastened to the horizontal bars 58 by well-known fasteners 62. If desired, the lower ends of the anchor bolts 60 may be fastened to the vertical bars 56. In FIG. 11, the vertical bars 56 are omitted for easy understanding. Meanwhile, the upper ends of the anchor bolts 60 are supported by a support 64. The support 64 is a U-shaped plate material with an open bottom, and is installed across the upper ends of the precast concrete foundation members 2a to 2d. A through hole is formed in the center of the support 64 penetrating in the vertical direction, and the support 64 prevents the anchor bolt 60 from falling over by inserting the anchor bolt 60 into this through hole. The anchor bolts 60 thus arranged extend upward beyond the upper ends of the precast concrete foundation members 2a to 2d.

After the anchor bolt installation process (i.e., after the reinforcement process), a foundation pouring process is carried out in which unhardened concrete is poured from any position on the top surface of the grooves 14a to 14d formed in the various precast concrete foundation materials 2a to 2d. In this way, the unhardened concrete flows from the grooves 14a to 14d through the opening windows 20a to 20d and flows out onto the floor 46, and the slab reinforcement 52 is buried. The unhardened concrete is poured up to a height position exceeding the upper end position of the opening windows 20a to 20d in the floor 46, and up to the upper end position of the grooves 14a to 14d in the precast concrete foundation materials 2a to 2d, respectively, and thus the vertical reinforcement 56 and the horizontal reinforcement 58 are also buried. As the poured concrete hardens, the floor portion 68 and the rising portion 70 of the mat foundation 66 are integrally formed without any joints, as shown in FIG. 12. After the poured concrete has hardened, the support 64 is removed from the anchor bolt 60.

In the precast concrete foundations 2a to 2d constructed according to the present invention, the rising portion 70 of the mat foundation 66 is formed by pouring concrete into the grooves 14a to 14d at the construction site. In other words, the rising portion 70 of the mat foundation 66 is completed at the construction site, not at a factory where the precast concrete foundations 2a to 2d are formed, so the weight of the precast concrete foundations 2a to 2d themselves is light. Therefore, according to the precast concrete foundations 2a to 2d constructed according to the present invention, a large crane is not necessarily required to move them, and therefore the workability of the foundation construction is improved. Furthermore, since the opening windows 20a to 20d that communicate with the grooves 14a to 14d are formed at the lower ends of the upright walls 6a to 6d, the slab reinforcement 52 can be arranged by inserting the ends 54 of the slab reinforcement 52 into the opening windows 20a to 20d after the precast concrete foundations 2a to 2d are arranged as required at the construction site. Therefore, there is no need to form the precast concrete foundation material with the reinforcing bars included, and the reinforcing bars do not protrude to the outside during transportation. Therefore, the precast concrete foundation material constructed according to the present invention can be safely transported. Furthermore, according to the method of forming the mat foundation 66 using the precast concrete foundation materials 2a to 2d constructed according to the present invention, the construction period can be shortened because the sacrificial concrete poured at the construction site is sufficient only in the places where the precast concrete foundation materials 2a to 2d are placed. Furthermore, in the mat foundation 66 formed using the precast concrete foundation materials 2a to 2d constructed according to the present invention, the earthen floor portion 68 and the rising portion 70 are formed integrally without any joints, so that cracks are unlikely to occur at the boundary between the earthen floor portion 68 and the rising portion 70, and sufficient seismic strength can be maintained.

2a to 2d: Precast concrete foundation material 4a to 4d: Bottom plate 6a-1 to 6d-4: Standing wall 14a to 14d: Groove 20a to 20d: Opening window 22a: Forming device 24a: Base 26a: Inner mold 28a: Outer mold 32a: Hinge means 34a: Outer mold piece 50: Floor 52: Slab reinforcement 56: Vertical reinforcement 58: Horizontal reinforcement 60: Mat foundation 62: Floor portion (of mat foundation) 64: Rising portion (of mat foundation)

Claims (13)

A precast concrete foundation material for forming a mat foundation, comprising a bottom wall of a required shape and upright walls rising upward from the side edges of the bottom wall to form a groove of the same shape as the required shape in a plan view, an opening window communicating with the groove is formed at the lower end of the upright wall, and the upper surface and end surfaces of the groove formed by the upright walls are open,
This precast concrete foundation material is characterized in that the rising portion of the slab foundation is formed by pouring concrete into the groove . The precast concrete foundation material according to claim 1, wherein the required shape is a straight line, an L-shape, a T-shape, or a cross shape. The precast concrete foundation material according to claim 1 or 2, in which a bottomed hole is formed in the upper surface of the bottom wall. The precast concrete foundation material according to any one of claims 1 to 3, wherein the bottom wall has a through hole penetrating in the vertical direction, and the inner peripheral surface of the bottom wall that defines the through hole has a female thread formed thereon. The precast concrete foundation material according to claim 4, wherein the through hole is formed at the center of gravity of the bottom wall. A molding device for molding the precast concrete foundation material according to any one of claims 1 to 5,
The mold has a fixed base and an inner mold and an outer mold attached to the base,
The inner mold protrudes upward from an upper surface of the base,
The outer mold is composed of a plurality of plate-shaped outer mold pieces connected to the base via hinge means, and each of the plurality of outer mold pieces is freely rotatable between a molding position in which its inner surface is close to the outer surface of the inner mold and a demolding position in which it is separated from the outer surface of the inner mold, and when the outer mold pieces are positioned at the molding position, the upper end position of the outer mold pieces is positioned higher in the vertical direction than the upper end position of the inner mold, and a bulge portion is formed at a required portion of the inner surface of the outer mold piece that comes into surface contact with the outer surface of the inner mold when in the molding position. The molding device according to claim 6, wherein the bulging portion has a bulging end surface that is in surface contact with the outer surface of the inner mold when the outer mold piece is in the molding position, and a bulging outer peripheral surface that extends from the outer peripheral edge of the bulging end surface and connects to the inner surface of the outer mold piece, and the bulging outer peripheral surface extends in a direction from the inner surface of the outer mold piece toward the outer surface. The molding device according to claim 6 or 7, wherein the vertical cross-sectional shape of the inner mold is tapered upward. A method for producing the precast concrete foundation material according to any one of claims 1 to 5 using the molding device according to any one of claims 6 to 8,
a base forming body pouring step of pouring unhardened concrete into the inside of the outer mold when all of the outer mold pieces are in the molding position to form a precast concrete base forming body;
a demolding preparation step of rotating all of the outer mold pieces from the molding position to the demolding position after the precast concrete foundation body has hardened;
The method further comprises a demolding step of demolding the precast concrete base body from the inner mold after the demolding preparation step. When the precast concrete base material according to claim 4 or 5 is manufactured by the method according to claim 9, in the mold release preparation step, the through hole and the female thread are formed, a bolt is threaded into the through hole from above, and the tip of the bolt presses the upper surface of the inner mold. When the precast concrete base material according to claim 4 or 5 is manufactured by the method according to claim 9 or 10, the through hole and the female thread are formed in the mold release preparation step, and an eye bolt is screwed into the through hole from above. A method for forming a mat foundation using the precast concrete foundation material according to any one of claims 1 to 5, comprising the steps of:
a base member arranging step of arranging a plurality of the precast concrete base members continuously as required on the basal concrete to connect the groove endlessly;
a reinforcing bar arrangement process for inserting an end of a slab reinforcing bar into the opening window after the foundation material arrangement process;
and a foundation pouring step of pouring unhardened concrete from the top surface of the groove after the reinforcement step. 13. The method according to claim 12, further comprising the steps of: after the reinforcing bar arrangement step and before the foundation casting step, performing an anchor bolt arrangement step of arranging an anchor bolt at an upper end of the precast concrete foundation material; and the anchor bolt being supported by a support device straddling the upper end of the precast concrete foundation material.

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