Measurements of shear wave velocity by resonant-column test, bender element test and miniature accelerometers

Javier Camacho-Tauta, Giovanni Cascante, Jaime A. Santos, António Viana da Fonseca

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Laboratory Testing

ABSTRACT: Bender elements (BE) have been widely utilized to measure shear wave velocities at low shear strain. One of the most controversial issues is the lack of knowledge of the actual behaviour of the BE inside the soil. BE tests were compared with resonant-column tests and readings of miniature accelerometers inside the specimen at different elevations. While time domain (TD) analysis produced reasonable results, frequency domain (FD) analysis showed significant differences. Experimental measurements and simplified numerical simulations revealed the existence of several peaks in the transfer function between BE. These peaks produce slight variations in the slope of the phase angle function, affecting the travel time estimation. FD analysis should be done in a frequency range located far away to the main peaks, requiring a careful selection of the input signal depending of the soil stiffness, characteristics of BE and specimen dimensions. PRESENTACIONES TÉCNICAS El ensayo de Bender elements (BE) ha sido ampliamente utilizado para medir la velocidad de la onda cortante a baja deformación. Uno de los aspectos mas controvertidos es el poco conocimiento acerca del comportamiento de estos elementos dentro del espécimen. Se compararon ensayos BE con ensayos de columna resonante y lecturas de acelerómetros miniatura localizados a diferentes elevaciones. Mientras los análisis en el dominio del tiempo (TD) concordaron razonablemente, los análisis en el dominio de la frecuencia (FD) mostraron diferencias significativas. Resultados experimentales y simulaciones numéricas simplificadas mostraron múltiples picos en la función de transferencia entre el par de BE. Estos picos coinciden con ligeras variaciones en la pendiente del ángulo de fase, afectando la estimación del tiempo de viaje. El análisis FD debería realizarse en un rango frecuencial alejado de los picos principales, requeriendo una cuidadosa selección de la señal de entrada, dependiendo de la rigidez del suelo, las características de los BE y las dimensiones del espécimen.

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Cite this article:
Javier Camacho-Tauta; Giovanni Cascante; Jaime A. Santos; António Viana da Fonseca (2011) Measurements of shear wave velocity by resonant-column test, bender element test and miniature accelerometers in GEO2011. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GEO11Paper949,author = Javier Camacho-Tauta; Giovanni Cascante; Jaime A. Santos; António Viana da Fonseca ,title = Measurements of shear wave velocity by resonant-column test, bender element test and miniature accelerometers,year = 2011}