報告書番号

380002

タイトル（和文）

広いひずみ範囲における粗粒材の動的変形特性と減衰特性

タイトル（英文）

DYNAMIC PROPERTIES OF DEFORMATION AND DAMPING OF COARSE SOILS FOR WIDE STRAIN RANGE

概要 （図表や脚注は「報告書全文」に掲載しております）

原子力発電所の建設では，基礎岩盤の掘削にともなって生ずる大量の砕石を構造物周辺に埋め戻し材や盛土材料として使用する場合が多くなってきた。しかし，粗粒材の強度や変形特性を室内実験的に求めることは技術面，経済面から容易ではなく，細粒土に比べて研究例が少ない。特に動的変形強度特性は，これら粗粒材からなる地盤の地震時安定性を論じる時に不可欠であるにもかかわらず，未解明な点が多い。筆者らは以前に三軸装置の応力とひずみの検出部に改良を加え，広範な動的ひずみ振巾の範囲での砂の動的物性を容易に測定できる実験法を開発した。今回，大型三軸試験機（供試体径３００ｍｍ，高さ７００ｍｍ）に同様の改良を加え，粗粒材の０．０００００１～０．００１オーダーのひずみ振巾での動的変形特性と減衰特性を解明することを目的とした実験を行った。本報告は，砕石および自然の円礫について行った実験結果を報告したものである。

概要 （英文）

DYNAMIC MATERIAL PROPERTIES OF SOILS HAVE USUALLY BEEN MEASURED IN THE LABORATORY USING THE TORSIONAL COLUMN SHEAR DEVICE. THE CYCLIC TRIAXIAL TEST DESPITE ITS FREQUENT USE IN THE ENGINEERING PRACTICE HAS SELDOM BEEN LOOKED UPON AS A RATIONAL WAY TO MAKE A RELIABLE MEASUREMENT OF DYNAMIC PROPERTIES FOR A SMALL STRAIN RANGE IN PARTICULAR. MOST OF THE MOVING PARTS OF THE TRIAXIAL APPARATUS SUFFER FROM MECHANICAL FRICTIONS MAKING HIGHLY SENSITIVE AM EASUREMENTS RATHER MEANINGLESS. IN THIS EXPERIMENTAL RESEARCH A DISPLACEMENT SENSOR CONSISTING OF TWO SEPARATE DISCS HIGHLY SENSITIVE ON THE RELATIVE SEPARATION HAS BEEN INTRODUCED TO A LARGE TRIAXIAL APPARATUS(SPECIMEN DIAMETER:300MM AND SPECIMEN HEIGHT:700MM),AS WELL AS A LOAD TRANSDUCER,INSIDE THE TRIAXIAL CELL TO COMPLETELY ELIMINATE THE MECHANICAL FRICTIONS,AND TO MEASURE THE DYNAMIC PROPERTIES OF COARSE MATERIALS FOR THE WIDE STRAIN RANGE OF 0.000001 TO 0.001. ALTHOUGH COARSE MATERIALS SUCH AS CRUSHED ROCKS AND ROUND GRAVELS ARE CONVENIENTLY UTILIZED IN CONSTRUCTION WORKS LIKE ROCKFILL DAMS, DEPENDABLE DYNAMIC PROPERTIES FOR THOSE MATERIALS AREFAR LESS AVAILABLE THAN FOR SANDS AND CLAYS ON ACCOUNT OF THE DIFFICULTIES OF THE TEST METHOD. A SERIES OF CYCLIC LOADING TESTS ON A ROUND GRAVEL USING THE IMPROVED LARGE TRIAXIAL APPARATUS HAVE CLARIFIED;(1)THE ELASTIC SHEAR MODULUS OF THE CRUSHED ROCK MEASURED AND FORMULATED HERE IN A SIMPLE EQUATION IS IN A GOOD COINCIDENCE WITH THE MODULUS MEASUREDWITH IN-SITU SEISMIC SURVEY,(2)THE MODULUS OF THE ROUND GRAVEL CAN BE EVALUATED WITH THE SAME EMPIRICAL EQUATION WHICH WAS ESTABLISHED FOR SANDS,(3)THE STRAIN DEPENDENT VARIATION OF THE MODULUS IS FAR MORE DRASTIC THAN SANDS,AND (4)THE DAMPING RATIO OF THE CRUSHED ROCK IS TWICE LARGER THAN SAND FOR THE STRAINS UP TO 0.001

報告者

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