ELASTIC WAVE MEASUREMENT VARIOUS TYPE OF TRANSDUERS IN IIS 室内土供試体の弾性波速度測定 The elastic wave measurement is becoming popular to obtain small strain stiffness of soil. In IIS, various type of transducers are currently used, including bender element (BE), Trigger-Accelerometer (TA), Trigger-Bimorph element (TB) and disk transducer (DT). The waveform of each transducer on Toyoura sand specimen is presented. 地盤材料の微小ひずみ剛性は、供試体内の弾性波の伝播速度を測定することにより求めることができます。様々なセンサーを用いて砂供試体内のP 波およびS波の伝播速度を測定して比較しています。 Various type of Transducers トップに装着した加振機によって送信し、供試体側 面2箇所につけた受信機で波を捉える。 The signal is actuated by triggers attached to a top. A pair of sensors put lateral surface of the specimen receive the signal. 圧電素子 Piezo-ceramic Element ベンダーエレメント Bender Element Transducer 加速度計による 受信機 Accelerometer Input/Output voltage (V, mV) Metal block 加速度計 Accelerometer 送信波 Input wave Typical waveform by Disk Transducer Input signal (V) P波加振機 Output signal (mV) Trigger for P-wave 0 S波加振機 Trigger for S-wave Top cap ∆ t -15 σ1=σ3=50kPa, Dr=48% S-wave, Sine, 6kHz 0.0000 0.0005 Time (sec) Specimen: Φ=50mm, H=100mm X Specimen LDT Typical waveform by Accelerometer X Lower Accelerometer Pedestal Oscilloscope -0.2 0.0000 Specimen: Φ=50mm, H=100mm 0.0007 Time (sec) σ1=σ3=400kPa, Dr=68% S-wave, Sine, 15.6kHz -30 0.6 0.0 σ1=σ3=50kPa Dr=48% P-wave, Sine, 2.65kHz ∆ t Specimen: Φ=75mm, H=150mm Typical waveform by BE Receiver Output voltage (V) Output voltage (V) ∆ t 0 Output signal (mV) 0.0003 0.0006 Time (sec) バイモルフ素子による受信 Bimorph element receiver Upper Accelerometer 0.2 Input signal (V) 30 0.0000 0.0010 加速度計 Accelerometer バイモルフ素子による受信機 Bimorph Element Receiver Function Generator Typical waveform by Bender Element 15 バイモルフ素子(シリーズ) Series type bimorph element Metal block Disk Transducer TEST ON TOYOURA SAND P波加振機 Trigger for P-wave S波加振機 Trigger for S-wave Input/Output voltage (V, mV) バイモルフ型素子 Bimorph Element 加振機 Trigger Trigger Accelerometer method Trigger Bimorph element method 波の送受信に使われる圧電素子はメタルケースの中に収められ、さらに三 軸試験装置のトップとペデスタル内に装着する。 Piezo-ceramic elements are used for both transmitter and receiver. Coated elements are encapsulated into metal housing and then installed into top cap and pedestal. 0.0014 送信波と受信波の取得 Monitoring of input and output signal 0.3 Upper BE Lower BE ∆ t 0.0 -0.3 -0.6 σ1=σ3=100kPa, Dr=92% P-wave, Sine, 3.7kHz 0.000 Specimen: Φ=75mm, H=150mm 0.001 Time (sec) 本研究に関する担当研究室は桑野研究室です. 部屋は東京大学生産技術研究所B棟3階のBw-304 For further information, contact below. Dr. Reiko Kuwano, #Bw-304, Institute of Industrial Science 電話: 03-5452-6843,FAX: 03-5452-6844 E-mail: kuwano@iis.u-tokyo.ac.jp TEL: +81-3-5452-6843, FAX: +81-3-5452-6844 E-mail: kuwano@iis.u-tokyo.ac.jp 0.002 ELASTIC WAVE MEASUREMENT SIMULTANEOUSLY OBTAINED P & S WAVES BY DISK TRANSDUCER ディスクトランスデューサーによるP波・S波の同時測定 Recently developed flat disk shaped piezo-ceramic transducer, “Disk Transducer” is employed on the cyclindrical triaxial specimen of 75 mm in diameter and 150 mm in height in several granular geo-materials. Both compressional and shear (P and S) waves were propagated exciting P type and S type peizo-ceramic elements together and the corresponding responses (received compressional and shear waves) are achieved simultaneously. 室内土供試体のP波とS波速度を同時に測定できる、ディスクトランスデューサーを開発しました。粒径の異なる3種類の砂で得られた結果を示します。 SIMULTANEOUSLY ACHIEVED COMPRESSIONAL AND SHEAR (P AND S) WAVES ON GRANULAR MATERIALS Waveforms obtained on Toyoura sand Waveforms obtained on Silica sand Waveforms obtained on Hime gravel RELATIONS TO EVALUATE MATERIALS PROPERTIES Relations used in elastic wave measurement Velocity of the wave Vp H Tp Poisson’s ratio in terms of velocity (0.5V p2 Vs2 ) Young’s modulus V p2 Vs2 H Vs Ts Constrained modulus M *V p Shear modulus G * Vs 2 2 Static relations H E M (1 2 )(1 ) (1 ) E Conversion between G G and E 2(1 v) H = Distance between two transducers (specimen height) dH H ln( ) H H 0 H0 Axial (vertical) strain, a Radial (lateral) strain, r R dR R R0 Poisson’s ratio, r ln( R ) R0 Young’s modulus, E a Stress-Stiffness relationship Toyoura sand` Silica sand Hime gravel 本研究に関する担当研究室は桑野研究室です. 部屋は東京大学生産技術研究所B棟3階のBw-304 For further information, contact below. Dr. Reiko Kuwano, #Bw-304, Institute of Industrial Science 電話: 03-5452-6843,FAX: 03-5452-6844 E-mail: kuwano@iis.u-tokyo.ac.jp TEL: +81-3-5452-6843, FAX: +81-3-5452-6844 E-mail: kuwano@iis.u-tokyo.ac.jp a
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