報告書番号

U90064

タイトル（和文）

地震時における基礎地盤の安定性評価（その８）－模型振動実験を対象とした数値シミュレーション手法の検証と地震時安定性評価の例示

タイトル（英文）

EVALUATION OF STABILITY OF FOUNDATION GROUNDDURING EARTHQUAKE(PART8) -NUMERICAL SIMULATION OF SHAKING-TABLE TEST AND CASE STUDY OF EVALUATION OF STABILITY DURING EARTHQUAKE

概要 （図表や脚注は「報告書全文」に掲載しております）

本報告は，非線形解析手法を用いて，第四紀地盤の地震知己安定性評価の検証を図った結果について述べるものであり，得られた知見は以下の通りである。（１）砂の破壊強度などに主応力軸の方向や中間主応力の影響を考慮するよ構成式の拡張が図られた。（２）陰・陽混合法の直接積分を行うことが可能となった。（３）地盤－構造物系の２次元動的問題への適用性を検証するため，模型振動実験の数値シミュレーションを行い，解析手法の妥当性を確認した。（４）第四紀立地の安定性評価フローに従って，Ａ地点の地盤調査・試験結果に基づき，基本検討段階から詳細検討段階までの地震時安定性評価を行った。その結果，砂礫地盤は地震動中ほとんど過剰間隙水圧が上昇しないこと，構造物の最終的な残留沈下量は，最大でも０．６ｍｍ程度で，不同沈下もほとんど生じず，構造物は十分安定であることが示された。

概要 （英文）

IN CONSTRUCTION OF NUCLEAR POWER PLANTS ON QUATERNARY GROUND, IT IS VERY IMPORTANT TO EVALUATE THE STABILITY OF THEFOUNDATION GROUND DURING EARTHQUAKES WITH HIGH ACCURACY. SO FAR, CRIEPI HAS DEVELOPED A NONLINEAR RESPONSE ANALYSIS METHOD FOR PREDICTING FOUNDATION DEFORMATION DURING AND AFTER AN EARTHQUAKE AND VERIFICATION HASBEEN PERFORMED BY SEVERAL NUMERICAL SIMULATIONS. THIS REPORT DESCRIBESTHE RESULTS OF A TWO-DIMENSIONAL SHAKING-TABLE TEST AND A CASE STUDY ANALYSIS. THE FOLLOWING CONCLUSIONS WERE REACHED. 1.NUMERICAL SIMULATIONOF TWO-DIMENSIONAL SHAKING-TABLE TEST (1)NUMERICAL SIMULATION WAS PERFORMED BY NONLINEAR RESPONSE ANALYSIS (NAFSS) AND THE COMPUTED RESULTS WERE IN GOOD AGREEMENT WITH THE EXPERIMENTAL ONES. THE APPLICABILITY OF NUMERICAL ANALYSIS TO TWO-DIMENSIONAL DYNAMIC INTERACTIONS WAS VERIFIED. 2.STABILITY EVALUATION OF GROUND (1)THE STABILITY OF THE FOUNDATION GROUND AND THE STRUCTURE DURING EARTHQUAKES WAS STUDIED IN ACCORDANCE WITH THE PROPOSED EVALUATION PROCEDURES. THE SOIL PROFILE IS A LOOSE SANDLAYER FROM GLOM TO -5M AND A QUATERNARY GRAVELLY-SAND LAYER FROM GL-5MTO GL-80M. THE STRUCTURE IS EMBEDDED IN THE QUATERNARY GRAVELLY-SAND LAYER DOWN TO GL-20M. (2)IT IS PROBABLE THAT THE SURFACE LOOSE SAND LAYER LIQUEFIES BUT THE GRAVELLY-SAND LAYER DOES NOT. THE SETTLEMENT OF THEGROUND SURFACE AND AT THE TOP OF GRAVELLY SAND LAYER ARE 1.55 CM AND 0.75 CM, RESPECTIVELY. (3)THE EXCESS PORE WATER PRESSURE IS ALMOST AT THE LIQUEFACTION CONDITION IN THE SURFACE LOOSE SAND LAYER, BUT, IN THE GRAVELLY-SAND LAYER, THE EXCESS PORE WATER PRESSURE IS SMALL. THUS,THE BEARING CAPACITY OF THIS LAYER IS MAINTAINED DURING AND AFTER AN EARTHQUAKE. THE FINAL SETTLEMENT AT THE BOTTOM OF THE FOUNDATION LAYER IS 0.06CM INDICATING NO SERIOUS EFFECT ON THE STABILITY OF THE STRUCTURE.

報告者

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