報告書番号

U89048

タイトル（和文）

自己掘進型孔壁加圧試験装置の開発と砂礫地盤の合理的な物性評価式の提案

タイトル（英文）

DEVELOPMENT OF SELF-BORING TYPE PRESSUREMETER AND PROPOSAL OF EMPIRICAL FORMULA TO ESTIMATE MECHANICAL PROPERTIES OF GRAVELLY SOIL

概要 （図表や脚注は「報告書全文」に掲載しております）

原子力発電所の第四紀地盤立地研究の中で，砂礫地盤でも調査可能な孔壁加圧試験装置として「自己掘進型孔壁加圧試験装置」を開発した。本装置を用いて密な砂および砂礫を主体とする第四紀層の地盤調査を実施し，その適用性を検討した。さらに，同時に実施した他の調査・試験法による結果との比較検討を行って，本装置で得られた地盤物性値の評価を行った。その結果は次の通りである。１．本装置による孔壁加圧試験は，従来の方法に比べて応力解放および孔壁の攪乱が小さいことが明らかになった。したがって，初期側方土圧（Ｐ０），静的変形係数（Ｅｓ），動的変形係数（ＥＤ）および減衰定数（ｈ），をより，精度よく求めることができた。２．砂礫層の動的孔壁加圧試験で得られたＧ～γ関係は，凍結サンプリング試料を用いて室内動的三軸試験で得られたＧ～γ関係とほぼ一致し，本装置で得られる物性値の精度の高いことがわかった。

概要 （英文）

DILUVIAL GRAVELLY GROUND HAS GREAT POTENTIALAS A FOUNDATION FOR CONSTRUCTING NUCLEAR POWER PLANTS(NPP). BECAUSE DILUVIAL GRAVELLY GROUND HAS A BEARING CAPACITY LARGE ENOUGH FOR NORMAL ENGINEERING STRUCTURES,IT HAS NOT BEEN NECESSARY TO CARRY OUT DETAILED SURVEYS AND TESTS ON SUCH GROUND. CRIEPI IS DEVELOPING IN-SITU TEST METHODS TO EVALUATE THE SETTLEMENT AND FOUNDATION STABILITY OF IMPORTANT NPP STRUCTURES AGAINST EARTHQUAKES. AS PART OF THE DEVELOPEMENT,CRIEPI HAS DEVELOPED A SELF-BORING TYPE PRESSUREMETER WHICH ENABLES THE PROBE TOPENETRATE GRAVELLY DEPOSITS WITH MINIMUM DISTURBANCE. THIS EQUIPMENT CAN IMPOSE STATIC AND REPEATED DYNAMIC PRESSURES ON THE BORE-HOLE WALL. THIS REPORT DESCRIBES THE RESULTS OF TESTS USING THIS EQUIPEMENT IN GRAVELLY GROUND AT 5 SITESIN JAPAN. THE TEST RESULTS ARE SOMPARED WITH THOSE OBTAINEDBY OTHER TESTING METHODS SUCH AS THE TRIAXIAL TEST AND SHEARWAVE VELOCITY TEST TO DEMONSTRATE THE EFFICIENCY OF THIS IN-SITU TEST.THE FOLLOWING CONCLUSIONS WERE OBTAINED. 1.THE SELF-BORING TYPE PRESSUREMETER ALLOWS DETERMINATION OF MECHANICAL PROPOERTIES OF GROUND AT HIGHER SCCURACY THAN PTHER TESTING METHODS BECAUSE THE FORMER METHOD MINIMIZES THE EFFECT OF DISTURBANCE AND STRESS RELEASE. 2. THE SHEAR MODULUSAND SHEAR STRAIN RELATIONSHIPS,AND THE DAMPING RATIO AND SHEAR STRAIN RELATIONSHIPS WERE OBTAINED BY THE SELF-BORING PRESSUREMETER TESTS IN GRAVEL DEPOSIT. THEY WERE COMPARED WITH RESULTS FROM DYNAMIC TRIAXIAL TESTS UNDER THE SAME STRESSCONDITIONS ON SPECIMENS SMAPLED FROM THE SAME SITE BY THE FREEZING SMAPLING METHOS. BOTH RESULTS WERE IN GOOD AGREEMENT.

報告者

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