中間層支持杭の鉛直支持力特性に関する研究
中間層の厚さをパラメータとした遠心模型実験
中間層に支持される杭の遠心模型実験を実施し，中間層厚を変化させた場合の杭先端の鉛直支持力特性を比較検討した。本研究により得られた知見をまとめれば以下に示す通りである。
(1) 杭下方の中間層厚の減少に伴い，中間層のパンチング破壊に起因して杭先端荷重が低下する。
(2) 杭先端の（沈下量が杭径の10%に達した時の）第2限界荷重の実験結果は，杭先端付近の地盤変状を考慮して修正した既往式と概ね対応する。
(3) 杭先端の（沈下量が杭径の10%に達するまでの）荷重～沈下量関係の実験結果の平均は，杭下方の中間層厚が杭径の3倍以上となる場合は既往式とよい対応を示し，また杭径の2倍程度となる場合は既往式に比べて剛性変化が大きい傾向を示す。
キーワード： 杭，支持力，沈下，中間層，鉛直載荷実験，遠心模型実験
＊１ 技術センター建築技術研究所建築構工法研究室
Bearing Behavior of Vertically Loaded Piles on Thin Bearing Layers
Centrifuge Modeling of Piles on Bearing Layers of Various Thicknesses
Centrifuge modeling of piles was conducted to investigate the bearing behavior of vertically loaded piles on thin bearing layers of various thicknesses. The following conclusions were reached.
(1) The bearing capacities of the pile toes tended to decrease as the bearing layers below the pile toes became thinner.
(2) As for decreasing of the bearing capacities of the pile toes as the bearing layers became thinner when the settlement equaled 10% of a pile diameter, the test results generally corresponded to a previously -proposed relationship, modified in consideration for the conditions of the soils near the pile toes.
(3) As for the load-settlement relationships at the pile toes before the settlement reached 10% of a pile diameter, the test results generally corresponded to a previously -proposed relationship when the thickness of the bearing layer below a pile toe was more than 3 times the diameter of the pile, stiffness tended to change significantly when the thickness of the bearing layer was about twice diameter of the pile.
Keywords: pile, bearing capacity, settlement, thin bearing layer, vertical loading test, centrifuge model test
*1 Building System and Material Research Section, Building Engineering Research Institute, Technology Center
