所報 104

15/38

－　　－13Published PaperHorizontal Resistance of Pile Evaluated by Chang’s Formula Using Coefficient of Subgrade Reaction Calculated from Shear Wave Velocity Shuichi SHIMOMURA and Yasutsugu SUZUKIIn seismic design of pile foundation by static stress analysis, a model in which a pile is a beam and the beam and the ground are connected by multiple springs (coefficient of subgrade reaction kh) is used as a practical design. The stress and horizontal displacement of the piles obtained from this method strongly depends on the evaluation accuracy of the coefficient of subgrade reaction kh as well as the specification section of the pile body. In this study, we propose a method to evaluate coefficient of subgrade reaction kh based on shear wave velocity. We also propose a method to evaluate kh from inverse analyses based on the Chang’s formula using past several horizontal loading test data including large diameter piles performed at in situ. Using the proposed kh, simulation analyses by Chang’s formula are carried out and the validity of the coefficient is verified.Keywords: Single pile, Coefficient of subgrade reaction, Horizontal load test, Shear wave velocity, Pressuremeter test, Chang’s formulaせん断波速度に基づく地盤の変形係数を用いたChang式による杭の水平抵抗評価　静的応力解析による杭基礎の耐震設計では，杭を梁，この梁と地盤を複数のばね（地盤反力係数kh）で連結したモデルを実用的な設計として用いている。この手法から得られる杭の応力と水平変位は，杭体の断面性能だけではなく，水平地盤反力係数の評価精度に強く依存する。本研究では，水平地盤反力係数の評価に用いる地盤の変形係数算定にせん断波速度を用いる方法を提案した。さらに，杭頭自由条件の単杭の原位置水平載荷試験結果に基づき，Chang式を用いた逆解析から逆算水平地盤反力係数を求め，大口径杭まで含めた水平地盤反力係数の設定方法を提案した。提案手法を用いたChang式による原位置水平載荷試験のシミュレーションにより，本提案手法の有効性を確認した。キーワード：単杭，水平地盤反力係数，水平載荷試験，せん断波速度，孔内水平載荷試験，Chang式Journal（掲載誌）J.Struct. Constr. Eng., AIJ, Vol. 82, No. 741, pp.1747-1757, Nov. 2017