室内土供試体の弾性波速度測定 Elastic wave - 桑野研究室

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: [email protected]
TEL： +81-3-5452-6843， FAX： +81-3-5452-6844
E-mail: [email protected]
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: [email protected]
TEL： +81-3-5452-6843， FAX： +81-3-5452-6844
E-mail: [email protected]
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 a

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