報告書番号

U89020

タイトル（和文）

不飽和土における有効応力の新しい定義

タイトル（英文）

THE CONCEPT OF THE EFFECTIVE STRESS IN UNSATURATED SOILS

概要 （図表や脚注は「報告書全文」に掲載しております）

地盤の安定性に及ぼす間隙水挙動の影響を，不飽和土を含めて検討する上で不可欠な，不飽和土における有効応力の概念について，既往の研究の再検討と，多孔質体の変形挙動に関する基礎的な考察とにより検討し，新たに提案した。不飽和土の間隙は，保水状態によって，一様不飽和あるいは封入不飽和となる。前者の場合には，連続する間隙空気を，また，後者の場合には，空気を包み込んだ水を，単一の間隙流体と見なすことにより，不飽和土を固体相と圧縮性の流体相との二相からなる多孔質体として扱える。この多孔質体の変形挙動を検討した結果，有効応力を「外応力のうち，変形に寄与する応力成分」と定義すれば，従来の，飽和土におけるものと同一の有効応力式を導くことができる。ただし，間隙流体圧として，一様不飽和状態の場合には気体圧を，封入不飽和の場合には水圧を採用する必要がある。

概要 （英文）

THE PRINCIPAL OF THE EFFECTIVE STRESS IS THEFUNDAMENTAL CONCEPT WHEN WE DISCUSS THE STABILITY OF THE SATURATED SOIL STRUCTURE CONSIDERING THE PORE WATER BEHAVIOR AND THE DEFORMATION OF SOILS SIMULTANEOUSLY. IN ADDITION TO THE SATURATED STATE OF THE SOIL THERE MAY BE A LOT OF GEOTECHNICAL PROBLEMS CONCERNING THE UNSATURATE SOILS SO THAT THE EXAMINATION OF THE CONCEPT OF THE EFFECTIVE STRESS IN THE UNSATURATED SOILS IS REQUIRED. IN ORDER TO STUDY THE CONCEPT OF THE EFFECTIVE STRESS IN UNSATURATED SOILS,IN THIS PATER,THE STATE OF THE ARTIS REVIEWED AND THE FUNDAMENTAL DISCUSSION ON THE EFFECTIVE STRESS IS PERFORMED BY CONSIDERING THE BEHAVIOR OF DEFORMATION OF THE SOILS AS THAT OF THE POROUS MEDIA. THE CONCLUSIONS OF THIS PAPER ARE DESCRIBED AS FOLLOWS: (1)THERE ARE TWO TYPES OF EXISTENCE OF THE AIR IN UNSATURATED PORE OF SOILS. THAT IS TO SAY,THE AIR EXISTS CONTINUOUSLY IN THE PORE OR THE AIR IS OCCLUDED IN THE PORE WATER. IN THE FORMER CASE BY ASSUMINGTHAT THE AIR IS THE SOLE PORE FLUID AND THE SOIL STRUCTURE CONSISTS OFSOIL PARTICLES AND WATER,AND IN THE LATTER CASE BY ASSUMING THAT THE WATER OCCLUDING THE AIR IS THE SINGLE PORE FLUID AND THE SOIL STRUCTURE CONSISTS OF SOIL PARICLES,WE CAN TREAT THE UNSATURATED SOILS AS POROUS MEDIA OF A SOLID PHASE AND A COMPRESSIVE FLUID PHASE. (2)THE APPLICATION OF TWO-PHASE MIXTURE THEORY TO THE POROUS MEDIA LEADS THE GENERAL EXPERSSION OF THE DEFORMATION CAUSED BY EXTERNAL STRESS. IF WE DEFINE THE EFFECTIVE STRESS AS THE EFFECTIVE PART OF THE EXTERNAL STRESS CONTRIBUTING TO THE DEFORMATION ,THE EQUATION OF THE EFFECTIVE STRESS OF THE UNSATURATE SOIL IS EXPRESSED AS THE SAME EQUATION OF TERZAGHI S. CONSEQUENTLY IT IS EXPRESSED AS FOLLOWS: SIGMA IJ=SIGMA IJ+P SIGMA IJ (I,J=1,2,3) WHERE SIGMA IJ :TOTAL STRESS, SIGMA IJ :EFFECTIVE STRESS, RHO :PORE FLUID PRESSURE SIGMA IJ :KRONECKER S DELTA. CONCERNING THE PORE FLUID PRESSURE,P,IT IS THE AIR PRESSURE WHEN THE PORE AIR IS CONTINUOUS,AND ITIS THE WATER.

報告者

キーワード