報告書番号

EU97001

タイトル（和文）

台湾・花蓮地点における大規模耐震実証試験研究 -－動的ｼﾐｭﾚｰｼｮﾝ解析のための土の剛性比，減衰比のひずみ依存性の提案－-

タイトル（英文）

The Hualien Large-Scale Seismic Test for Soil-Structure Interaction Research― Proposal on strain dependency of stiffness ratio and damping ratio of soils for dynamic simulation analysis―

概要 （図表や脚注は「報告書全文」に掲載しております）

大地震時の地盤と構造物の相互作用を調べるため，『花蓮プロジェクト』と呼ばれる国際共同研究が現在進行している．本報告では，地震時応答の予測をするために実施された一連の地盤調査・試験結果のうち，室内試験結果をとりまとめて，解析に必要な物性値を提案することを目的にしている．得られた成果は以下の通りである． （１）軸ひずみの測定方法を改善した高精度な繰返し三軸試験による初期せん断弾性係数からせん断波速度を計算し，原位置PS検層によるせん断波速度と比較したところ，砂層の場合両者はほぼ一致するが，砂礫層では前者は後者よりも小さかった．これは，不均一性が原因であると思われた．（２）三軸供試体に加えた応力と原地盤における応力の差ならびに詰直して作製した三軸供試体と原地盤との間の密度の差を考慮して繰返し三軸試験結果を補正し，動的シミュレーション解析に用いる地盤材料の剛性比・減衰比のひずみ依存性を提示した．

概要 （英文）

The Hualien Large-Scale Seismic Test (HLSST) program is under way to investigate soil-structure interaction during large earthquakes in Hualien, a region in Taiwan of high seismicity. A 1/4-scale model building was constructed on the gravelly soil layer in this site. Extensive geotechnical investigation including velocity logging and sampling by the in-situ freezing technique was conducted for accurate evaluation of SSI during earthquakes. This report summarizes the field and laboratory tests conducted to obtain the strain dependency of shear modulus and damping ratio of the soils for dynamic response analysis and to characterize the ground of the test site. The following conclusions were drawn. (1) Strain dependency of shear modulus and damping ratio as well as initial shear modulus were accurately measured by cyclic triaxial tests. The shear wave velocities converted from initial shear modulus measured by cyclic triaxial tests were compared with those by the velocity logging. For sands, the shear wave velocities measured by cyclic triaxial tests were almost the same as those by the velocity logging, whereas shear wave velocities of gravelly soils measured by cyclic triaxial tests were much smaller than those by the velocity logging. This difference seems to be attributable to the effect of heterogeneity in the gravelly soil layer. (2) The strain dependency of stiffness ratio and damping ratio for earthquake response analysis were proposed by correcting the results of the cyclic triaxial tests to the in-situ confining stress and to the in-situ soil density.

報告者

キーワード