JP2022016934A - Earthen floor structure for soft ground - Google Patents

Abstract

To control cracking, rippling, etc. caused by a foundation beam supporting an earthen floor with a large amount of settlement.SOLUTION: An earthen floor structure for soft ground comprising a pile foundation 2 supporting a building on a soft ground G, and a concrete earthen floor 3 constructed at a position higher than the pile foundation 2 and supported on the soft ground G, comprises a settlement allowable space 4 between an upper surface 22a of a foundation beam 22 of the pile foundation 2 and a lower surface 31a of the earthen floor 3, which allows the earthen floor 3 to settle without the support force acting from the foundation beam 22 supported by a pile 20.SELECTED DRAWING: Figure 3

Description

The present invention comprises a pile foundation that supports a building on soft ground and a concrete soil that is constructed above the pile foundation and is supported by the soft ground. Regarding.

In the above-mentioned soil structure of soft ground, the amount of subsidence of the building is small because the building on the soft ground is supported by the pile foundation. However, the amount of subsidence increases in concrete soil floors (truck berths, etc.) that are constructed above the pile foundation and supported by soft ground. Therefore, since the foundation beam of the pile foundation with a small amount of subsidence exists below the soil floor, the soil floor with a large amount of subsidence is supported by the foundation beam. As a result, the above-mentioned difference in the amount of subsidence may cause cracks and waviness in the soil.

Further, as the above-mentioned soil structure of soft ground, for example, there is a method of constructing the lowermost floor of a building on a viscous ground, which is disclosed in Patent Document 1. In this construction method, the ground directly under the building is excreted, and the plate-shaped hard foam is bonded to the lower surface sheet and the upper surface sheet at the trace, and also adhered to each other to be integrated into a large hard foam. After laying while laying, a hard foam thin plate is placed on the upper surface of the foundation beam, and then soil concrete is placed on the upper surface of the integrated hard foam and the hard foam thin plate on the foundation beam to construct the lowest floor. ..

Japanese Patent No. 2836492

The above-mentioned technique of Patent Document 1 suppresses the ground subsidence due to the consolidation of the cohesive soil layer, which is increased by the construction of the lowermost floor due to the excretion of the ground. This is a technology that suppresses uneven subsidence of the lowermost floor for buildings that are supported by pile foundations and have a small amount of subsidence.
Therefore, Patent Document 1 does not disclose a technique for suppressing cracks and waviness in the soil caused by the soil having a large amount of subsidence being supported by the foundation beam of a pile foundation having a small amount of subsidence.

In view of this situation, a main object of the present invention is to provide a soil structure of soft ground capable of suppressing cracks and waviness caused by the soil floor having a large subsidence amount being supported by the foundation beam.

The first characteristic configuration of the present invention includes a pile foundation that supports a building on soft ground and a concrete soil floor that is constructed above the pile foundation and is supported by the soft ground. It is a soil structure with soft ground,
Between the upper surface of the foundation beam of the pile foundation and the lower surface of the soil floor, a subsidence allowable space is provided that allows the subsidence of the soil floor without applying a supporting force from the foundation beam supported by the pile. At the point.

According to the above configuration, since the building on the soft ground is supported by the pile foundation, the amount of subsidence of the building is small. However, the amount of subsidence increases in concrete soil floors (truck berths, etc.) that are constructed above the pile foundation and supported by soft ground. Even if there is a difference between the amount of subsidence of the building supported by the pile foundation and the amount of subsidence of the soil supported by the soft ground, it is still between the upper surface of the foundation beam of the pile foundation and the lower surface of the soil. In the provided subsidence tolerance space, subsidence of the soil can be tolerated without exerting a bearing force from the foundation beam supported by the pile. As a result, cracks and waviness caused by the large amount of subsidence being supported by the foundation beam can be suppressed.

The second characteristic configuration of the present invention is that the lateral portion of the subsidence allowable space is provided with a support leg portion for supporting a portion located above the subsidence allowable space in the soil floor.

According to the above configuration, while providing a subsidence allowable space between the upper surface of the foundation beam of the pile foundation and the lower surface of the soil, the load of the soil portion located above the subsidence allowable space is applied to the side of the subsidence allowable space. It can be appropriately supported by the support legs provided at the site.

In the third characteristic configuration of the present invention, the support leg portion extends downward along the side surface of the foundation beam, and a clearance is provided between the side surface of the support leg portion and the facing surface of the side surface of the foundation beam. It is in the point that it is prepared.

According to the above configuration, the support legs are extended downward along the side surface of the foundation beam to more appropriately support the load of the soil portion located above the allowable subsidence space, while supporting the support legs. The clearance provided between the side surface and the side surface of the foundation beam can suppress the influence of the side surface of the support leg and the side surface of the foundation beam on cracks and waviness in the soil due to frictional contact.

Cross-sectional view showing the layout relationship between the building on the truck berth side and the pile foundation Plan view showing the arrangement of pile foundations on the truck berth side FIG. 2 is a cross-sectional view taken along the line III-III.

An embodiment of the present invention will be described with reference to the drawings.
The construction site to which the soil structure of the soft ground G is applied is a reclaimed land which is an example of the soft ground G, and as an example of the building 1 on the soft ground G, as shown in FIGS. 1 and 2, the rigid frame structure The warehouse building is illustrated.
The geological formation of the reclaimed land of the present embodiment will be a filling layer, an unconsolidated marine clay layer, a sandy, clayey burial alternating layer, and a burial cohesive soil layer from the ground surface. Land subsidence is expected over the course.

Therefore, in the soil structure of the soft ground G, there is a pile foundation 2 that supports the building 1 on the soft ground G and a concrete soil that is constructed above the pile foundation 2 and is supported by the soft ground G. The floor 31 of the track berth 3 is provided.
The pile foundation 2 includes a plurality of piles 20 reaching the support grounds of the Kozumi alternating layer or the Kozumi cohesive soil layer, footings 21 supporting the plurality of pillars 11 of the building 1, and the X and Y directions of the building 1. It is provided with a plurality of foundation beams 22 integrally constructed with the footing 21 along the above.
Examples of the pile 20 include cast-in-place concrete piles, PHC piles (ready-made concrete piles), steel pipe piles and the like. The shape, structure, and arrangement of the pile 20 can be changed as appropriate.

The footing 21 is constructed of reinforced concrete in a state of covering the pile head of the pile 20 after excavating the shallow layer portion of the soft ground G to the root cutting surface. As shown in FIG. 3, the foundation beam 22 has a beam reinforcing bar (not shown) connected to the reinforcement arrangement of the footing 21 (not shown) on the waste concrete (not shown) laid on the root cutting surface. After assembling and constructing the formwork, the concrete of the foundation beam 22 is placed.

After the construction of the pile foundation 2, as shown in FIG. 3, it is buried in the excavation area of the shallow part of the soft ground G excluding the thickness of the floor 31 of the truck berth 3 constructed by placing the soil concrete. The return material 32 is filled. As the backfill material 32, various materials such as fluidized soil, excavated soil, demolition waste, gravel, and crushed stone can be appropriately used according to the construction plan and the like. Next, the reinforcing reinforcing bar 33 is assembled on the upper surface side of the backfill layer, and the soil concrete is placed up to the design ground surface (design GL) to construct the floor 31 of the truck berth 3.

Then, as shown in FIG. 2, footings 21 supported by two piles 20 are arranged at each of the central portion in the X direction in the track berth 3 and the central portion in the X direction on the periphery of the track berth 3. A central foundation beam 22 along the Y direction is arranged over both footings 21.
As shown in FIG. 3, the upper surface (top surface) 22a of the foundation beam 22 in the central portion is arranged below the lower surface 31a of the floor 31 of the track berth 3, but the marine clay layer of the soft ground G. The track berth 3 supported by the soft ground G also sinks due to the consolidation settlement and the like. Since the subsidence amount of the track berth 3 is larger than the subsidence amount of the building 1 supported by the pile foundation 2, as the subsidence of the track berth 3 progresses, the lower surface 31a of the floor 31 of the track berth 3 becomes the foundation in the central portion. It will be supported by the upper surface 22a of the beam 22. As a result, there is a possibility that the floor 31 of the track berth 3 may be cracked or wavy due to the difference in the amount of subsidence described above.

Therefore, in the soil structure of the soft ground G of the present invention, as shown in FIG. 3, the pile 20 is supported between the upper surface 22a of the foundation beam 22 in the central portion and the lower surface 31a of the floor 31 of the track berth 3. A subsidence allowable space 4 that allows the subsidence of the track berth 3 without applying a bearing force is provided from the foundation beam 22 in the central portion. The subsidence allowable space 4 is a cavity, which is wider than the width of the foundation beam 22 in the central portion and is configured to have a depth that allows the set subsidence amount of the track berth 3.
In the present embodiment, as shown in FIG. 1, in order to secure the subsidence allowable space 4, the top end surface of the footing 21 arranged in the central portion in the X direction in the track berth 3 and the footing 21 in the Y direction. The top surface of the foundation beam 22 arranged along the line is arranged below each top surface of the footing 21 and the foundation beam 22 arranged at other places.

Then, even if there is a difference between the subsidence amount of the building 1 supported by the pile foundation 2 and the subsidence amount of the track berth 3 supported by the soft ground G as described above, the foundation beam 22 in the central portion In the subsidence allowable space 4 provided between the upper surface 22a and the lower surface 31a of the floor 31 of the track berth 3, the track berth 3 is supported by the central foundation beam 22 supported by the pile 20 without applying a bearing force. Subsidence can be tolerated. As a result, it is possible to suppress cracks and waviness caused by the floor 31 of the track berth 3 having a large amount of subsidence being supported by the foundation beam 22 in the central portion.

Further, as shown in FIG. 3, support legs supporting a portion (soil portion) located above the subsidence allowable space 4 on the floor 31 of the track berth 3 are provided on both sides of the subsidence allowable space 4 in the width direction. 41 is provided. The support leg portion 41 is a reinforced concrete leg wall portion 41A extending downward from the lower surface 31a of the floor 31 along both side surfaces 22b of the foundation beam 22 in the central portion, and the horizontal direction from the lower ends of both leg wall portions 41A. It is provided with a reinforced concrete leg bottom portion 41B extending along the side of the foundation beam 22 so as to be separated from the foundation beam 22.

As described above, while the subsidence allowable space 4 is provided between the upper surface 22a of the foundation beam 22 in the central portion and the lower surface 31a of the floor 31 of the track berth 3, the upper side of the subsidence allowable space 4 on the floor 31 of the track berth 3 is provided. The load of the portion (soil portion) located in can be appropriately supported by the support leg portions 41 provided on both side portions in the width direction of the subsidence allowable space 4.

Crushed stone 42 and waste concrete 43 are laid in two layers at the construction site of the sole portion 41B of the support leg portion 41. On the upper side of the waste concrete 43, the reinforcing reinforcing bars 44 of the leg wall portion 41A and the reinforcing reinforcing bars 45 of the leg bottom portion 41B are assembled in a substantially "L" shape while being connected to the reinforcing reinforcing bars 33 on the floor 31 side, and the formwork is formed. After construction, the concrete of the support leg 41 is placed.

As shown in FIG. 3, a clearance 5 is provided between each facing surface of the side surface 41a of the leg wall portion 41A of both support leg portions 41 and the side surface 22b of the foundation beam 22 in the central portion.
Then, both support legs 41 are extended downward along both side surfaces 22b of the foundation beam 22 in the central portion, and are located above the subsidence allowable space 4 on the floor 31 of the track berth 3 (soil portion). By the clearance 5 formed between the side surfaces 41a of the leg wall portion 41A of the support leg portions 41 and the side surface 22b of the foundation beam 22 in the central portion, both of them are supported more appropriately. It is possible to suppress the influence of the side surface 41a of the leg wall portion 41A of the support leg portion 41 and the side surface 22b of the foundation beam 22 in the central portion on the cracking and waviness of the floor 31 of the track berth 3 due to frictional contact. ..

[Other embodiments]
(1) In the above-described embodiment, the subsidence allowable space 4 is configured as a cavity, but a compressible filler may be filled. In short, the subsidence allowable space 4 may be any space that allows the track berth 3 to subside without applying a bearing force from the central foundation beam 22 supported by the pile 20.

(2) In the above-described embodiment, a clearance 5 is provided between the side surfaces 41a of the leg wall portion 41A of both support leg portions 41 and the both side surfaces 22b of the foundation beam 22 in the central portion. It may be carried out without providing the clearance 5. That is, even if the side surface 41a of the leg wall portion 41A of both support leg portions 41 and the side surface 22b of the foundation beam 22 in the central portion are brought into contact with each other in a state allowing relative movement in the vertical direction due to the subsidence of the track berth 3. good.

1 Building 2 Pile foundation 3 Doma (truck berth)
4 Allowable subsidence space 5 Clearance 20 Pile 21 Footing 22 Foundation beam 22a Top surface 22b Side surface 31a Bottom surface G Soft ground

Claims (3)

It is a soil structure of soft ground provided with a pile foundation that supports a building on soft ground and a concrete soil that is constructed above the pile foundation and is supported by the soft ground.
Between the upper surface of the foundation beam of the pile foundation and the lower surface of the soil floor, there is provided a subsidence allowable space that allows subsidence of the soil floor without applying a supporting force from the foundation beam supported by the pile. Soil structure of soft ground. The soil structure of a soft ground according to claim 1, wherein a support leg portion for supporting a portion of the soil above the subsidence allowable space is provided on a side portion of the subsidence allowable space. The second aspect of claim 2, wherein the support leg portion extends downward along the side surface of the foundation beam, and a clearance is provided between the side surface of the support leg portion and the facing surface of the side surface of the foundation beam. Soil structure of soft ground.

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