報告書番号

381002

タイトル（和文）

杭の動的効果─基礎の動的挙動に対する杭の影響─

タイトル（英文）

EFFECTS OF PILE ON THE DYNAMIC BEHAVIORS OF FOUNDATION

概要 （図表や脚注は「報告書全文」に掲載しております）

同一基礎形状の直接基礎と杭基礎の起振実験結果を比較検討することにより、直接基礎に適用されている変電機器の耐震設計法の杭基礎への適用性について検討し、以下の結果を得た。なお実験に用いた基礎はコンクリート製で平面寸法３．８ｍ、高さ１．５ｍであり、杭基礎は、杭径５０８ｍｍ長さ２１ｍの５本杭からなる。（１）水平振動に関係する水平ばね係数・減衰係数には両基礎形式による差は認められない。上下振動と回転振動に関係する上下または回転ばね係数および減衰係数は、明らかに坑基礎の値が直接基礎に比べ大きく、杭の効果が認められる。（２）（１）の結果および従来の研究成果を参考にすれば変電機器基礎程度の杭基礎に対する地盤ばね係数・減衰係数の１次近似として、水平動については直接基礎と同じ値を、回転動については直接基礎の２倍程度。値を採用すれば良い。

概要 （英文）

THIS PAPER DESCRIBES THE BEHAVIOR OF PILE FOUNDATION(PLAN 3.8MX3.8M ;HIGHT 1.5M,PILE DIA. 508MM,LENGTH 21M,NUMBER OF PILE 5)EXCITED BY THE MECHANICAL EXCITER,COMPARING WITH THE MAT FOUNDATION,AND PROPOSES THE MODELING METHOD OF PILE FOUNDATION FOR THE SUBSTATION EQUIPMENTS. (RESULTS) (1)VERTICAL VIBRATION:THE DISPLACEMENT RESPONSE OF PILE FOUNDATION IS LESS THAN 50% OF THE MAT FOUNDATION IN CASE OF EMBEDDING,AND LESS THAN 30% IN CASE OF NON-EMBEDDING. THE RESONANT FREQUENCY IS 1.6 TIMES LARGER THAN THE MAT FOUNDATION,REGARDLESS OF THE EMBEDDING CONDITION. (2)SWAY AND ROCKING VIBRATION:THE DISPLACEMENT RESPONSE OF PILE FOUNDATION IS THE SAME AS THE ONE OF THE MAT FOUNDATION IN CASE OF EMBEDDING BUT THE FORMER BECAMES LESS THAN 50% OF THE LATTER IN CASE OF NON-EMBEDDING. THIS MEANS THAT THE ASEISMIC EFFECT OF PILE IS EXPECTED AS THE MOVEMENT OF PILE BECOMES VIOLENT. THE RESONANT FREQUENCY OF PILE FOUNDATIONS CONSIST WITH THE ONE OF MAT FOUNDATION. (3)THE BEHAVIORS DESCRIBED ABOVE(2)ARE EVALUATED USING THE SPRING MODEL AND THE FOLLOWING RESULTS ARE OBTAINED. (A)VERTICAL SPRING COEFFICIENT AND DAMPING COEFFICIENT OF THE PILE FOUNDATION ARE 3 OR 4 TIMES LARGER THAN THE MAT FOUNDATION. THE SPRING COEFFICIENT IS NOT DEPENDENT ON THE FREQUENCY AND THE DAMPING COEFFICIENT IS SLIGHTLY DEPENDENT ON THE FREQUENCY. (B)HORIAONTAL(SWAY)SPRING COEFFICIENT AND DAMPING COEFFICIENT ARE RECONGNIZED TO BE THE ALMOST SAME VALUES IN BOTH FOUNDATION TYPES. SPRING COEFFICIENT DOES NOT DEPEND ON THE FREQUENCY AND DAMPING COEFFICIENT DEPENDS ON THE FREQUENCY,ESPECIALLY EXHIBITING THE PEAK AT 8HZ ON THE RELATIONSHIPS BETWEEN THE COEFFICIENT AND THE FREQUENCY. (C)ROCKING SPRINGAND DAMPING COEFFCIENT OF PILE FOUNDATION EXHIBIT 2 TIMES LARGER THAN THE ONE OF MAT FOUNDATION. SPRING COEFFICIENT DECREASES SLIGHTLY WITH FREQUENCY AND DAMPING COEFFCIENT DEPENDS ON THE FREQUENCY,EXHIBITING THEPEAK AT 8 HZ.

報告者

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