報告書番号

385048

タイトル（和文）

軟質地盤における基礎の埋設効果に関する実験的検討（その２）－起振実験に基づく振動台基礎周面地盤の剛性・減衰性評価－

タイトル（英文）

EXPERIMENTAL STUDY ON ENBEDMENT EFFECT OF FOUNDATION (PART 2)EVALUATION OF DYNAMIC SOIL STIFFNESSAND DAMPING SURROUDING THE TABLE FOUNDATION DUE TO SHAKING TEST

概要 （図表や脚注は「報告書全文」に掲載しております）

軟質地盤における埋設基礎の動的挙動を明らかにするため，同一地盤上で模型基礎（４×４×３ｍ）と実規模の振動台基礎（１６×１６×７．７ｍ）を対象とした起振実験と地震観測を実施した。本研究は振動台基礎の起振実験に基づいて，基礎の挙動，基礎周辺地盤の剛性，減衰特性を模型基礎の実験結果と対比しつつ検討し，基礎の埋設効果について考察したものである。起振実験結果から埋設形式の基礎が減衰の非常に大きい振動系であることが確かめられた。このような埋設効果を支配する側面地盤の剛性，減衰性について検討したところ，振動台基礎の側面地盤ばね定数値は模型基礎より約３０倍も大きくなったが，その相違はＮｏｖａｋの理論解によって基本的に説明できることが判明した。一方，側面地盤へ逸散する減衰量は両者の埋設深さや地盤物性が異なるにもかかわらずほぼ同程度であり，５０～６０％と非常に大きな値をとることが判明した。

概要 （英文）

IN OEDER TO MAKE CLEAR THE DYNAMIC BEHAVIOR OF AN EMBEDED FOUNDATION ON THE QUATENARY GROUND EXPERIMENTALLY,A SERIES OF FORCED VIBRATION TESTS AND SEINSMIC OBSERVATION ON BOTH THE SMALL FOUNDATION (4*4*3M)AND THE EMBEDED FORM LARGER SCALE FOUNDATION OF THE SHAKING TABLE (16*16*7.7M) WERE CONDUCTED AT THE SAME SITE. THE PURPOSES OF THIS STUDY ARE TO EVALUATE THE DYNAMIC BEHAVIOR AND THE CHARACTERISTICS OF DYNAMIC STIFFNESS AND DAMPING OF THE LARGER FOUNDATION BASED ON FORCED VIBRATION TESTS AND APPLING THEM TO THE DYNAMIC RESPONSE ANALYSIS OF SIMILAR EMBEDDED FOUNDATIONS. IN THIS REPORT,THE AUTHORS FIRST EXAMAINE FREQUENCY DEPENDENT PROPERTY AND ITS THEORETICAL TENDENCY OF DYNAMIC STIFFNES AND DAMPING SARROUNDING TABLE FOUNDATION,AND THEN,CONSIDER THE ENBEDMENT EFFECT IN CONTRAST WITH THE EXPERIMENTAL DATA OF THE MODEL FOUNDATION. IN THE CASE OF FULL-BACKFILL MODEL FOUNDATION AND THE TABLE FOUNDATION,RESONANT PEAK DESS NOT APPEAR AND DISPLACE AMPLITUDE MODERATELY DECREASES AS FREQUENCY RANGE IS HIGHER. SO,IT IS RECOGNIZED THAT THE DYNAMIC RESPONSE OF EMBEDED FORM FOUNDATION WOULD BE PRODUCTED WITH HIGHER DAMPING VALUE. AND THEN,THE SIDE LAYER STIFFNESS AND DAMPING WHICH DOMINATE THE EMBEDMENT EFFECT ARE CONSIDERED COMPARING THE MODEL FOUNDATION AND THE TABLE FOUNDATION. THE EXPERIMENTAL DATA OF THE SOIL SPRING CONSTANTS IN THE TABLE FOUNDATION HAVE ABOUT 30 TIMES AS MUCH VALUES AS THE MODEL FOUNDATION ONES,AND THIS RESULT CAN BE WELL EXPLAINED BY HALF-SPECE THEORY. N THE OTHER HAND,THOSE DAMPING CONSTANTS ARE ROUGHLY EQUAL AND HAVE HIGHER VALUE(50 60 PERCENT)IN SPITE OF THE DIFFERENCE RELATED WITH THE SIDE LAYER SOIL CONSTANTS AND THE EMBEDMENT DEPTHBETWEEN BOTH FOUNDATION. IT SEEMS TO BE QUITE ALL RIGHT TO CONSIDER SIGNIFICANT CHARACTERISTICS OF THE EMBEDDED FROM FOUNDATION.

報告者

キーワード