Effects of particle breakage on compressibility of coral sand

さんご石灰質砂の圧縮特性と粒子破砕の影響を一次元圧縮試験により明らかにした。主な結果は次のようである。(1) 石灰質砂はシリカ質砂に比べて圧縮性が著しい。(2) 圧縮指数は圧縮応力の増加に伴い0.5まで増加する。(3) 粒子破砕に及ぼす圧縮応力の影響の程度は初期間隙比に関係なく圧縮応力と圧縮降伏応力の比で評価できる。(4)圧縮応力の増加に伴う間隙比の減少は粒子破砕の程度に支配される。(5) 粒子破砕を伴う応力レベルでのクリープ変形は磨耗を伴う粒子間の相対変位によってもたらされることが推察される。(6) 一次元圧縮条件下ではクリープひずみ速度の対数とクリープ経過時間の対数の関係は2つの折点を持つ線形関係で表される。Coral sands are consist of such bioclastic as coral, shell, foraminifera, etc. in that particles are relatively soft and can easily be broken. In this paper in order to investigate the effects of the particle breakage on the compressibility and creep deformation of coral sand, the one-dimensional compression tests up to a vertical stress of 62.72MPa and the one-dimensional creep tests under a constant vertical stress of 11.76MPa. The materials used are coral sands obtained from eight different locations in coral reefs around Ryukyus Islands, south west part of Japan. The compressibility of sand is controlled by the particle breakage. The degree of particle breakage is uniquely related to the ratio of the compressive yield stress to the maximum applied stress. Creep deformation is significant after an elapsed loading time of 1000 minutes. The time dependence of the compressibility is caused by the abrasion on the particle surface because of the increase in the percent finer than 0.075mm during creep process