報告書番号

U90046

タイトル（和文）

砂礫地盤に対する各種サンプリング法の適用性の検討

タイトル（英文）

APPLICABILITY OF VARIOUS SAMPLING METHODS TOGRAVELLY GROUND

概要 （図表や脚注は「報告書全文」に掲載しております）

一般に砂礫は，試料採取時に乱れも受けやすいため，凍結サンプリング法が有効であり，従来行われてきた非凍結サンプリング法では高品質な試料を採取することはもちろん，試料を得ることさえ難しいとされてきた。ところが，凍結サンプリング法によれば，高品質な試料が得られるものの，実施には高額な費用を要するため，広範囲な地盤調査に適用することは困難であると思われる。一方，攪乱の影響の大きさは，物性の種類によっても異なるため，凍結サンプリングの必要性は，求めようとする物性の種類により異なるものと思われる。そこで本報告では，複数の非凍結サンプリング法により採取された試料の物性も凍結サンプリング法によるものと比較し，非凍結サンプリングの適用性も検討した。その結果，密度，粒度分布，静的強度，剛性比・減衰比のひずみ依存性については両者の差がないこと，動的密度には大きな差があるが，補正できる可能性があることがわかった

概要 （英文）

PREVIOUSLY,IT HAS BEEN THOUGHT THAT HIGH-QUALITY GRAVELLY SOIL SAMPLES CANNOT BE OBTAINED BY CONVENTIONAL TUBE SAMPLING BUT THEY CAN BE OBTAINED BY USING AN IN-SITU FREEZING METHOD. HOWEVER,IN-SITY FREEZING SAMPLING IS MORE EXPENSIVE THAN CONVENTIONAL IN TUBE SAMPLING. THEREFORE,IT IS DIFFCULT TO USE IN-SITU FREEZING MANY FIELDS OF INVESTIGATION. IN ADDITION,IN-SITU FREEZING SAMPLING MAY BE REPLACED BY NON-FREEZING SAMPLING TO ESTIMATE SOIL CHARACTERISTICS THAT ARE NOT SENSITIVE TO SAMPLE DISTURBANCE. IN THIS RESEARCH,GRAVELLY SOIL SAMPLES WERE OBTAINED BY IN-SITU FREEZING AND VARIOUS CONVENTIONAL TUBE-SAMPLING METHODS. LABORATORY TESTS WERE CONDUCTED ON THE PHYSICAL ANS MECHANICAL PROPERTIES OF THE SAMPLES TO EVALUATE THE SAMPLING METHODS. THEFOLLOWING CONCLUSIONS WERE REACHED. (1)PHYSICAL PROPERTIES THE GRAIN SIZE DISTRIBUTION AND UNIT WEIGHT ARE INDEPENDENT OF THE SAMPLING METHOD. HOWEVER THE FINES CONTENT OF TUBE SAMPLES WAS SOMEWHAT LARGER THAN THAT OBTAINED BY IN-SITU FREEZING. (2)MECHANICAL PROPOERTIES CHARACTERISTICS SUCH AS STATIC STRENGTH,STRAIN DEPENDENCY OF G:GO (G:SHEAR MODULUS,GO:INITIAL SHEAR MODULUS)AND DAMPING RATIO OF TUBE SAMPLES AGREED WITH THOSE OF SAMPLES OBTAINED BY IN-SITU FREEZING. HOWEVER,CHARACTERISTICS SUCH AS INTIAL SHEAR MODULUS GO AND UNDRAINED CYCLIC SHEAR STRENGTH OF TUBE SAMPLES WERE SMALLER THAN THOSE IN-SITU FREEZING SAMPLES. HOWEVER,THE INITIAL SHEAR MODULUS CAN BE OBTAINED BY IN-SITY PS LOGGING. THE UNDRAINED CYCLIC SHEAR STRENGTH MIGHT BE EVALUATED FROM THE IN-SITU SHEARWAVE VELOCITY OBTAINED BY PS LOGGING. (3)APPLICABILITY OF TUBE SAMPLING TO GRAVELLY GROUND IT WAS DEMONSTRATED THAT CONVENTIONAL TUBE SAMPLING CAN BE APPLIED AS AN ALTERNATIVE TO IN-SITU FREEZING TO INVESTIGATE AWIDE RANGE OF DATA ABOUT GRAVELLY GROUND FROM THE VIEWPOINTS OF SAMPLEQUALITY AND COST.

報告者

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