Building foundation structure formed with soil improving body and raft foundation and construction method for soil improvement and raft foundation

Abstract

To provide building foundation structure formed with a soil improving body and raft foundation that can suppress weight increase of a soil improving body while achieving suppression of differential settlement and improvement of bearing capacity of the whole foundation and that can be applied to medium-rise buildings.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to building foundation structure formed with a soil improving body that improves soft soil or soil in which liquefaction occurrence is foreseen at the time of earthquakes and raft foundation cast on the soil improving body and a construction method for soil improvement and raft foundation.[0003]2. Description of the Background Art[0004]As a foundation for a building for soft soil or soil with possible liquefaction occurrence at the time of earthquakes, Japanese Unexamined Patent Publication No. 61-5114 (FIG. 1 and FIG. 2) discloses increasing rigidity as the whole soil and preventing damage to structure by liquefaction of the soil by penetrating into and drawing out of a soil while rotating an agitation blade of a deep mixing soil stabilizer, supplying an agglomeration chemical to discharge to the vicinity of the agitation blade at the time of penetration, agitating and mixing in the soil a...

AI Technical Summary

Benefits of technology

[0027]In addition, according to the building foundation structure formed with soil improving bodies and raft foundation obtained by the construction method for soil improvement and raft foundation of the present invention, the building load is supported by the frictional force of the side surface and reaction force of the bottom end surface of columnar soil improving bodies that make up a peristyle-form soil improving body in addition to the soil reaction force of the shallow-layer soil improving body and large bearing capacity is able to be obtained. Therefore, the present invention is able to be used for foundation of medium-rise buildings.

[0028]Furthermore, according to the building foundation structure formed with soil improving bodies and raft foundation obtained by the construction method for soil improvement and raft foundation of the present invention, locations of columnar improving bodies, the pitch between adjacent columnar improving bodies and diameter and length of columnar improving bodies can be varied to easily change the circumferential surface frictional force and tip reaction force. The present invention is able to be used for buildings of various shapes and loads by optimizing the cost while securing performance by controlling sharing ratio of soil contact reaction force, circumferential surface frictional force, and tip reaction force and relative settlement rate.

[0029]Still more, according to the building foundation structure formed with soil improving bodies and raft foundation obtained by the construction method for soil improvement and raft foundation of the present invention, columnar improving bodies that make up a peristyle-form soil improving body are not allowed to be suspended from the bottom surface of the top improving body but allowed to be suspended from the bottom surfaces of comparatively thick periphery improving bodies and internal improving body. It is therefore possible to efficiently increase the bearing capacity for buildings while suppressing an increase of the number of columnar improving bodies.

[0030]The construction method for soil improvement and raft foundation of the present invention includes steps of digging down the subsurface of soft soil or soil with possible liquefaction occurrence in a form of a shallow-layer soil improving body of a soil improving body, forming a peristyle-form soil improving body by agitating while injecting a solidification material and water after excavating the soil in a form of the columnar improving bodies, or by adding and mixing a solidification material to soil taken by excavating the soil in the form of the columnar improving bodies and backfilling, and compacting after mixing and agitating, mounting a plate or an intermediate as well as the plate on the top end surface of the peristyle-form soil improving body, forming the shallow-layer soil improving body by adding and mixing a solidification material to the soil taken by excavating the soil in the form of the shallow-layer soil improving body and backfilling and screeding, and compacting, and building a raft foundation of reinforced concrete construction on a top improving body of the shallow-layer soil improving body, wherein the soil improving body comprises the shallow-layer soil improving body that is formed by the horizontal plate form top improving body, periphery improving bodies that are suspended from the bottom surface of the top improving body and form outer frames, and at least one internal improving body that is suspended from the bottom surface of the top improving body, at the same time links across the outer frames, and partitions an area inside the periphery improving bodies into a plurality of areas, and the peristyle-form soil improving body including a plurality of the columnar improving bodies that are suspended and provided in a row from the bottom surface of the plate in contact with the bottom surfaces of the periphery improving bodies and the internal improving body or the bottom surface of the intermediate in contact with the bottom surface of the plate. Therefore, in addition to the effects of the above-mentioned construction method for soil improvement and raft foundation, in the building foundation structure formed with soil improving bodies and raft foundation obtained by the construction method for soil improvement and raft foundation related to the present invention, plate material or plate material and intermediate are arranged between the periphery improving bodies as well as the internal improving body and columnar improving bodies. Consequently, the top surface of the columnar improving bodies that make up the peristyle-form soil improving body and the bottom surfaces of the periphery improving bodies and the internal improving body that make up the shallow-layer soil improving body are able to be easily deviated relatively in the horizontal direction at the time of earthquakes. It is therefore possible to reduce the seismic force (horizontal force) transmitted to buildings constructed on the relevant foundation structure and to greatly reduce the shakiness. Consequently, earthquake-resistant performance of the overall structure including the relevant foundation structure and buildings constructed on the structure can be still more improved.

Problems solved by technology

In the foundation by the underground wall made up of soil improving bodies of Patent Document 1, columnar soil improving bodies need to be continuously produced to form a wall, and therefore, it takes time to build the soil improving bodies and at the same time the cost increases.

In addition, in the piled raft foundation as is the case of Patent Document 2, a large number of reinforced concrete piles need to be placed beneath the foundation by the use of large heavy machinery, and as compared to the case in which the soil beneath the foundation is improved, the weight increases and at the same time the cost increases.

However, the foundation structure of buildings having the soil improving bodies and raft foundation of Patent Document 3 may be sometimes unable to achieve necessary bearing capacity and thereby unable to be used for the foundation of, for example, medium-rise reinforced concrete buildings of 5 to 7 stories.

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