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.

1 . A building foundation structure, comprising:
 a shallow-layer soil improving body that improves the subsurface of soft soil or soil with possible liquefaction occurrence, which is formed by a 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;   a peristyle-form soil improving body including a plurality of columnar improving bodies that improve the soil, which are suspended from the bottom surface of the periphery improving bodies and the internal improving body or suspended and provided in a row from the bottom surface of a plate in contact with bottom surfaces of the periphery improving bodies and internal improving body or the bottom surface of an intermediate in contact with the bottom surface of the plate; and   a raft foundation cast on the top improving body of the shallow-layer soil improving body.   
   
   
       2 . The building foundation structure according to  claim 1 , wherein the peristyle-form soil improving body comprises columnar improving bodies disposed immediately beneath columns of a building to be constructed on the raft foundation and columnar improving bodies provided in a row immediately beneath underground beams. 
   
   
       3 . The building foundation structure according to  claim 1 , wherein covered cylindrical cap materials are fitted over to the top end part of the columnar improving body. 
   
   
       4 . A construction method for soil improvement and raft foundation, comprising the 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 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;   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 suspended and provided in a row from the bottom surfaces of the periphery improving bodies and the internal improving body.   
   
   
       5 . A construction method for soil improvement and raft foundation, comprising the 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 improving 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.