Shear wave velocity and shear modulus in offshore clays

2015 ◽  
pp. 1151-1156 ◽  
Author(s):  
L Zuccarino ◽  
D Morandi ◽  
M Sottile
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity

scholarly journals CHARACTERIZING A TROPICAL SOIL VIA SEISMIC IN SITU TESTS

2019 ◽  
Vol 37 (3) ◽  
pp. 263
Author(s):  
Breno Padovezi Rocha ◽  
Heraldo Luiz Giacheti
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soil Profile ◽  
Site Investigation ◽  
Tropical Soil ◽  
Engineering Properties ◽  
Foundation Engineering

ABSTRACT. The shear wave velocity (Vs) is an important geotechnical parameter to be used in dynamic problems (e.g. earthquakes and vibration problems) as well as in static deformation analysis such as excavations and foundation engineering design. There are several in situ seismic tests to determine Vs such as the crosshole and the downhole techniques, as well as hybrid tests (e.g. seismic dilatometer – SDMT). This paper presents crosshole, downhole and SDMT tests carried out in a typical tropical soil profile from Brazil. Advantages and limitations regarding the test procedures and interpretation are briefly presented and differences observed among Vs determined by these techniques are discussed. Shear wave velocities (Vs) estimated from the crosshole, downhole and SDMT tests ranging from 194 to 370 m/s. The shear wave velocity suggests that the experimental site could be divided into two strata, which are in agreement with soil profile description. The maximum shear modulus (G0) calculated from the Vs by theory of elasticity can be used to show the investigated tropical soil is a typical unusual geomaterial. This article also emphasizes that the SDMT is a useful test for site investigation since it allows a great means for profiling geostratigraphy and soil engineering properties during routine site investigation as well as for dynamics problems. Keywords: shear wave velocity, maximum shear modulus, crosshole, downhole, SDMT.RESUMO. A velocidade de onda cisalhante (Vs) é um parâmetro geotécnico empregado em análises dinâmicas (terremotos e problemas de vibração), bem como em análises estáticas (escavações e projeto de fundações). Existem vários ensaios sísmicos de campo para a determinação de Vs, entre eles as técnicas crosshole e downhole, e os ensaios híbridos (por exemplo, dilatômetro sísmico – SDMT). Este artigo apresenta os ensaios crosshole, downhole e SDMT realizados em um perfil típico de solo tropical do Brasil, as vantagens e limitações dos procedimentos de ensaio e de interpretação são brevemente apresentadas, e as diferenças observadas entre os valores de Vs determinados pelas diferentes técnicas são discutidas. Os perfis de Vs determinados pelas diferentes técnicas variaram de 194 a 370 m/s. A velocidade da onda cisalhante sugere que o campo experimental investigado pode ser dividido em dois horizontes, os quais estão de acordo com a descrição do perfil do solo estudado. O módulo de cisalhamento máximo (G0), calculado a partir de Vs pela teoria da elasticidade, pode ser utilizado para demonstrar o comportamento não convencional do solo investigado. Este artigo também enfatiza que o SDMT é um ensaio geotécnico útil para a investigação geotécnica do subsolo, uma vez que permite a definição do perfil estratigráfico e a estimativa de parâmetros estáticos e dinâmicos de um projeto.Palavras-chave: velocidade de onda cisalhante, módulo de cisalhamento máximo, crosshole, downhole, SDMT.

scholarly journals Shear modulus of hydrate bearing calcareous sand-fines mixture

2019 ◽  
Vol 92 ◽  
pp. 04002
Author(s):  
Litong Ji ◽  
Abraham C.F. Chiu ◽  
Lu Ma ◽  
Chao Jian
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hydrate Formation ◽  
Confining Pressure ◽  
Specimen Preparation ◽  
Bender Element ◽  
Calcareous Sand ◽  
Bender Element Test

This article presents a laboratory study on the maximum shear modulus of a THF hydrate bearing calcareous sand (CS)–fines mixture. The maximum shear modulus was inferred from the shear wave velocity measured from the bender elements installed in a temperature-controlled triaxial apparatus. The specimen preparation procedures were specially designed to mimic the hydrate formation inside the internal pores of CS. A trial test was conducted to validate whether the shear wave velocity is a feasible parameter to monitor the formation and dissociation of hydrate in the CS-fines mixture. Based on the bender element test results, hydrate has a more profound effect than confining pressure on enhancing the maximum shear modulus of CS-fines mixture.

Changes in dynamic shear moduli of carbonate rocks with fluid substitution

Geophysics ◽  
2009 ◽  
Vol 74 (3) ◽  
pp. E135-E147 ◽  
Author(s):  
Gregor T. Baechle ◽  
Gregor P. Eberli ◽  
Ralf J. Weger ◽  
Jose Luis Massaferro
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Water Saturation ◽  
Acoustic Properties ◽  
P Wave ◽  
Shear Moduli ◽  
Water Saturated ◽  
Fluid Interaction

To assess saturation effects on acoustic properties in carbonates, we measure ultrasonic velocity on 38 limestone samples whose porosity ranges from 5% to 30% under dry and water-saturated conditions. Complete saturation of the pore space with water causes an increase and decrease in compressional- and shear-wave velocity as well as significant changes in the shear moduli. Compressional velocities of most water-saturated samples are up to [Formula: see text] higher than the velocities of the dry samples. Some show no change, and a few even show a decrease in velocity. Shear-wave velocity [Formula: see text] generally decreases, but nine samples show an increase of up to [Formula: see text]. Water saturation decreases the shear modulus by up to [Formula: see text] in some samples and increases it by up to [Formula: see text] in others. The average increase in the shear modulus with water saturation is [Formula: see text]; the average decrease is [Formula: see text]. The [Formula: see text] ratio shows an overall increase with water saturation. In particular, rocks displaying shear weakening have distinctly higher [Formula: see text] ratios. Grainstone samples with high amounts of microporosity and interparticle macro-pores preferentially show shear weakening, whereas recrystallized limestones are prone to increase shear strengths with water saturation. The observed shear weakening indicates that a rock-fluid interaction occurs with water saturation, which violates one of the assumptions in Gassmann’s theory. We find a positive correlation between changes in shear modulus and the inability of Gassmann’s theory to predict velocities of water-saturated samples at high frequencies. Velocities of water-saturated samples predicted by Gassmann’s equation often exceed measured values by as much as [Formula: see text] for samples exhibiting shear weakening. In samples showing shear strengthening, Gassmann-predicted velocity values are as much as [Formula: see text] lower than measured values. In 66% of samples, Gassmann-predicted velocities show a misfit to measured water-saturated P-wave velocities. This discrepancy between measured and Gassmann-predicted velocity is not caused solely by velocity dispersion but also by rock-fluid interaction related to the pore structure of carbonates. Thus, a pore analysis should be conducted to assess shear-moduli changes and the resultant uncertainty for amplitude variation with offset analyses and velocity prediction using Gassmann’s theory.

scholarly journals Small strain stiffness in overconsolidated Pliocene clays

2013 ◽  
Vol 45 (2) ◽  
pp. 169-181 ◽  
Author(s):  
Katarzyna Markowska-Lech ◽  
Mariusz Lech ◽  
Marek Bajda ◽  
Alojzy Szymański
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Cohesive Soil ◽  
Small Strain ◽  
Soil Parameters ◽  
Small Strain Stiffness ◽  
Triaxial Apparatus ◽  
Triaxial Cell

Abstract Small strain stiffness in overconsolidated Pliocene clays. A huge development of technical infrastructure, including the construction of many high-rise buildings, roads, railroads and extension of subway lines, took place over the recent years in Poland. Therefore, numerous planned investment projects require geotechnical data documenting the variation of soil parameters found in the subsoil. The shear wave velocity is one of the most important input parameters to represent the stiffness of the soil deposits. This paper focuses on the methods and devices using measurements of the shear wave velocity to estimate the initial shear modulus in cohesive soil. It is preferable to measure VS by in situ wave propagation tests, however it is often economically not feasible in all regions of Poland. Hence, a reliable correlation between shear wave velocity and parameters measured in triaxial cell or static penetration parameters would be a considerable advantage. This study shows results obtained from the bender elements tests and field techniques - seismic cone penetration test and seismic flat dilatometer, performed on overconsolidated cohesive soils in Warsaw. On the basis of the test results possible correlations between shear wave velocity (initial shear modulus), mean effective stress and void ratio are considered and four original empirical relationships are proposed. Moreover, the proposed formulas by two different techniques using triaxial apparatus and also RCPT cone were examined. The proposed formulas show a reasonable agreement with direct shear wave velocity profiles for clays and might be incorporated into routine laboratory and field practice

scholarly journals Piezoelectric Ring Bender for Characterization of Shear Waves in Compacted Sandy Soils

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1226
Author(s):  
Dong-Ju Kim ◽  
Jung-Doung Yu ◽  
Yong-Hoon Byun
Keyword(s):  
Shear Modulus ◽  
Water Content ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Shear Waves ◽  
Small Strain ◽  
The Other ◽  
Compacted Soils ◽  
Small Strain Shear Modulus

Shear wave velocity and small-strain shear modulus are widely used as the mechanical properties of soil. The objective of this study is to develop a new shear wave monitoring system using a pair of piezoelectric ring benders (RBs) and to evaluate the suitability of RB in compacted soils compared with the bender element and ultrasonic transducer. The RB is a multilayered piezoelectric actuator, which can generate shear waves without disturbing soils. For five compacted soil specimens, the shear waves are monitored by using three different piezoelectric transducers. Results of time-domain response show that the output signals measured from the RB vary according to the water content of the specimen and the frequency of the input signal. Except at the water content of 9.3%, the difference in the resonant frequencies between the three transducers is not significant. The shear wave velocities for the RB are slightly greater than those for the other transducers. For the RB, the exponential relationship between the shear wave velocity and dry unit weight is better established compared with that of the other transducers. The newly proposed piezoelectric transducer RB may be useful for the evaluation of the shear wave velocity and small-strain shear modulus of compacted soils.

scholarly journals Effect of Confining Pressures on the Dynamic Response Characteristics of Niger Delta Clay Soils

2021 ◽  
Vol 5 (2) ◽  
pp. 377-386
Author(s):  
J. O. Okovido ◽  
C. Kennedy
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Niger Delta ◽  
Damping Ratio ◽  
Bender Element ◽  
Confinement Pressure ◽  
Niger Delta Region ◽  
Test Parameters

The study investigated the earthquake potential in Niger Delta region of Nigeria. A series of resonant column and bender element test was performed on compacted clay soil samples across the investigated Niger Delta States, which showed the influence of confinement on frequency, shear modulus, shear velocity and damping ratio. The confinement in clay was high. The frequency response increases with pressure increase. Also, the resonance column test at various confinements revealed changes in shear modulus, accelerometer output and damping ratio. Thus, there was high variation in the test parameters as confinement pressure was increased. Similarly, the bender element tests also showed that pressure has effect on shear wave-velocity, shear modulus and damping ratio confinement. Although, unlike Resonance Column tests, the shear modulus and shear wave-velocity generally increased as confinement pressure was increased, while for damping ratio it decreases as confinement pressure was increased. The variations in resonance column/binder element test parameters showed that the Niger Delta region, as an oil and gas area, is susceptible to earthquake. Therefore, continuous monitoring of oil exploration activities must be put in place.

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