Expansion of application limitation of bender element test using a correction method based on linear system

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K04342
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Akita University
• Principal Investigator: OGINO Toshihiro 秋田大学, 理工学研究科, 准教授 (80312693)
• Co-Investigator(Kenkyū-buntansha): 田口 岳志 秋田大学, 理工学研究科, 助教 (00452839)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: ベンダーエレメント / モード解析 / 伝達関数

Outline of Final Research Achievements

For the purpose of improving measurement accuracy of bender element test, which can easily estimate S-wave velocity of ground materials, the vibration characteristics of several types of bender elements were evaluated at multiple points by a laser displacement sensor. The elements exhibited damped vibration following multi-degree-of-freedom system with several natural frequencies. As a result of experimental modal analysis, an unexpected eigen mode consisting of transverse bending motion, which is beyond the assumption was observed in all the elements.
Taking advantage of mode shape similarity between the elements and simple cantilever plate, the mode shapes were successfully modeled by replacing with analytical solutions. The determination method of the parameters that is necessary for fitting the model were also demonstrated.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

ベンダーエレメント法から得られるS波速度は，地盤材料のせん断弾性係数を求めるために用いられる。せん断弾性係数は土の材料特性を表す重要なパラメータのひとつであり，例えば，数値解析によって地盤の変形や地震応答を計算するために欠かせない。しかし，ベンダーエレメント法はS波の到達点の決定が難しい場合が多く，それが原因となって大きな誤差を生む可能性が従来から指摘されている。本研究はこれを解決するため，同法の測定精度改善を目的としたものである。その鍵となるベンダーエレメントの振動特性を本助成期間において明らかにすることができ，高精度化に欠かせない，振動特性のモデル化の道筋をつけることができた。