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Continuous Monitoring Of Bender Element Shear Wave Velocities During Triaxial Testing
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Book Synopsis Continuous Monitoring of Bender Element Shear Wave Velocities During Triaxial Testing by : Mark A. Styler
Download or read book Continuous Monitoring of Bender Element Shear Wave Velocities During Triaxial Testing written by Mark A. Styler and published by . This book was released on 2014 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bender element testing is used to measure shear wave velocities (VS) across soil specimens in the laboratory. Conventional bender element testing is carried out at a few discrete points during an experiment. This paper presents a method which uses bender elements to monitor VS continuously throughout a triaxial test. The method is based on monitoring the change in phase angle between a continuous trigger signal and a received signal. It allows the phase velocity at multiple selected frequencies to be monitored throughout a test. The method is described in detail and its use is illustrated for triaxial tests on loose specimens of Fraser River sand prepared by water pluviation. The variation of shear wave velocity is demonstrated during consolidation, ageing, and shearing to failure along a conventional stress path. Potential difficulties of interpretation are presented and discussed. In addition, the potential for continuous excitation of the specimen to alter the test results is considered and dismissed based on a comparison of samples tested without benders and with continuous benders at a range of excitation voltages. The proposed method for continuously monitoring bender element shear wave velocities does not use special or unique equipment. It results in a continuous VS from a trigger and receiver element installed on opposite ends of a triaxial specimen. This method provides a measure of VS during dynamic phases of an experiment that have not previously been observed. For example, this paper includes measures of VS at the onset of creep, the onset of shearing, and over the phase transformation from contractive to dilative behaviour. The relationship between fundamental soil behaviour and VS can now be more easily explored.
Book Synopsis Fabrication, Operation, and Health Monitoring of Bender Elements for Aggressive Environments by : Brina M. Montoya
Download or read book Fabrication, Operation, and Health Monitoring of Bender Elements for Aggressive Environments written by Brina M. Montoya and published by . This book was released on 2012 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bender elements are commonly used to monitor the shear wave velocity of soils in various tests, including triaxial, consolidation, and centrifuge tests. When used in aggressive soil environments, electromagnetic crosstalk can distort the received bender element signal, preventing accurate shear wave velocity measurements. Aggressive soil environments are defined herein as conductive soils with high relative permittivity. Under these conditions, the electrical source is transmitted from source to receiver bender, dominating any received shear wave signal propagating through the soil. Careful attention must be paid to reducing the transmission of the electromagnetic signal, particularly in aggressive soil environments. When the waterproof coating of a bender element degrades and the inner and outer electrodes become electrically connected in a saturated environment, the bender element will no longer operate. However, when the waterproofing material is degraded so that only a single electrode on the source element is exposed, electric current can enter the pore fluid and affect the received signal. Further, even if the waterproofing coating is intact, electromagnetic crosstalk from the induced electrical field generated by the transmitting bender element can still affect the received signal when the conductivity of the pore fluid is high. Bender elements can be constructed so as to greatly reduce the electromagnetic crosstalk, and simple tests can be performed to help ensure that the bender element system is not susceptible to crosstalk. The objective here is to present details and practical guidelines regarding the fabrication, operation, and health monitoring of bender elements that will help ensure clear shear wave velocity measurements in aggressive soil environments. The fabrication steps presented improve on previous recommendations. Bender element operation (including signal form, frequency, and amplitude) also affects signal quality and the accuracy of the measured travel time. Finally, recommendations for monitoring the health of the bender elements throughout the transducer life are outlined.
Book Synopsis Geotechnical Engineering in the XXI Century: Lessons learned and future challenges by : N.P. López-Acosta
Download or read book Geotechnical Engineering in the XXI Century: Lessons learned and future challenges written by N.P. López-Acosta and published by IOS Press. This book was released on 2019-11-26 with total page 3006 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first Pan-American Conference on Soil Mechanics and Geotechnical Engineering (PCSMGE) was held in Mexico in 1959. Every 4 years since then, PCSMGE has brought together the geotechnical engineering community from all over the world to discuss the problems, solutions and future challenges facing this engineering sector. Sixty years after the first conference, the 2019 edition returns to Mexico. This book, Geotechnical Engineering in the XXI Century: Lessons learned and future challenges, presents the proceedings of the XVI Pan-American Conference on Soil Mechanics and Geotechnical Engineering (XVI PCSMGE), held in Cancun, Mexico, from 17 – 20 November 2019. Of the 393 full papers submitted, 335 were accepted for publication after peer review. They are included here organized into 19 technical sessions, and cover a wide range of themes related to geotechnical engineering in the 21st century. Topics covered include: laboratory and in-situ testing; analytical and physical modeling in geotechnics; numerical modeling in geotechnics; unsaturated soils; soft soils; foundations and retaining structures; excavations and tunnels; offshore geotechnics; transportation in geotechnics; natural hazards; embankments and tailings dams; soils dynamics and earthquake engineering; ground improvement; sustainability and geo-environment; preservation of historic sites; forensics engineering; rock mechanics; education; and energy geotechnics. Providing a state-of-the-art overview of research into innovative and challenging applications in the field, the book will be of interest to all those working in soil mechanics and geotechnical engineering. In this proceedings, 58% of the contributions are in English, and 42% of the contributions are in Spanish or Portuguese.
Book Synopsis Analysis of Bender Element Tests by : R. Arulnathan
Download or read book Analysis of Bender Element Tests written by R. Arulnathan and published by . This book was released on 1998 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study is presented of potential errors in, and methods of interpreting, the results of cantilever-type, piezoceramic bender element tests for measuring the shear wave velocity of laboratory soil specimens. Interpretations based on the first direct arrival in the output signal are often masked by near-field effects and may be difficult to define reliably. Interpretations based on characteristic points or cross-correlation between the input and output signals are shown to be theoretically incorrect in most cases because of: (1) the effects of wave interference at the boundaries; (2) the phase lag between the physical wave forms and the measured electrical signals; and (3) non-one-dimensional wave travel and near-field effects. Interpretations based on the second arrival in the output signal are theoretically subject to errors from non-one-dimensional wave travel and near-field effects. Differences in Vs values obtained by the different interpretation methods are illustrated analytically and experimentally.
Book Synopsis Deformation Characteristics of Geomaterials by : C.-K. Chung
Download or read book Deformation Characteristics of Geomaterials written by C.-K. Chung and published by IOS Press. This book was released on 2011 with total page 1382 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the international edition of the proceedings of IS-Seoul 2011, the Fifth International Symposium on Deformation Characteristics of Geomaterials, held in Seoul, South Korea, in September 2011.The book includes 7 invited lectures, as well as 158 technical papers selected from the 182 submitted. The symposium explored ideas about the complex load-deformation response in geomaterials, including laboratory methods for small and large strains; anisotropy and localization; time-dependent responses in soils; characteristics of treated, unsaturated, and natural geomaterials; applications in field methods; evaluation of field performance in geotechnical structures; and physical and numerical modeling in geomechanics. These topics were grouped under a number of main themes, including experimental investigations from very small strains to beyond failure; behavior, characterization and modeling of various geomaterials; and practical prediction and interpretation of ground response: field observation and case histories. Both the symposium and this book represent an important contribution to the exchange of advanced knowledge and ideas in geotechnical engineering and promote partnership among participants worldwide.
Book Synopsis Horizontally Mounted Bender Elements for Measuring Anisotropic Shear Moduli in Triaxial Clay Specimens by : DS. Pennington
Download or read book Horizontally Mounted Bender Elements for Measuring Anisotropic Shear Moduli in Triaxial Clay Specimens written by DS. Pennington and published by . This book was released on 2001 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Novel horizontally mounted bender element devices capable of high-quality transmission and reception of horizontally propagated shear waves polarized in orthogonal planes across the mid-height of a triaxial clay specimen are described. Mounting of these mini benders, in a T-shaped configuration, is in the pads of a radial strain belt on 100 mm diameter triaxial samples, or alternatively as bender probes (similar in concept to mid-height pore pressure probes) suitable for use on triaxial samples down to 38 mm diameter. This latter type may also be used in bench-top tests or on site. The effective fabrication procedures that have been developed are described. The instrumentation systems used to drive and receive signals are outlined, and estimates of the magnitude of the shear strains developed by the bender elements and the accuracy with which shear wave velocities can be determined are discussed. These new bender elements enable both anisotropic shear moduli to be measured over the same path length on a single triaxial specimen that can be taken to a wide variety of anisotropic stress states. Comparison with measurements using conventional platen-mounted bender elements suggests these may underestimate the shear modulus by up to 20%.
Book Synopsis Advancements in Bender-element Testing - Frequency Effects by : Muhammad Irfan
Download or read book Advancements in Bender-element Testing - Frequency Effects written by Muhammad Irfan and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern building and bridge codes require seismic design of foundations and structures; for which, the evaluation of the soil's response to dynamic loads is an important requirement in seismic design. The dynamic soil response is governed by its dynamic properties such as shear modulus (wave velocity) and damping ratio. These soil dynamic properties are typically measured in laboratory mostly using a bender element system (BE) or a resonant column (RC) device. However, the operating frequency range of BEs (e.g. 1 to 15 kHz) and the RC (e.g. 20 to 220 Hz) are not representative of typical earthquake loads (e.g. 0.1 to 10 Hz). In addition, there are significant limitations in BE and RC testing which reduce their reliability. Thus, current seismic designs could be either conservative or unsafe. A major limitation in BE testing is that there is no standard procedure; mostly because the soil-BE interaction is not well understood; and the characterization of BE inside a soil specimen was not possible. On the other hand in RC testing, the soil dynamic properties cannot be evaluated simultaneously as function of frequency and strain. In a typical narrow-band resonant column test (e.g. sine sweep, random noise), the induced shear strains are different at each frequency component. Therefore, the main objectives of this study are to understand better the soil-BE interaction; which will provide the basis for the development of reliable guidelines for BE testing; and to verify the BE test results using the standard RC device. The main objectives are achieved by testing the BE using a state-of-the-art laser vibrometer and a newly developed transparent soil to measure the actual response of the bender element transmitter (Tx) and receiver (Rx) inside different media such as air, liquids, and sand under different confinements. Then, the dynamic characteristics of the Tx are measured using advanced modal analysis techniques originally developed for structural applications (e.g. Blind Source Separation). The modal analysis is used to investigate if the different BE vibration modes correspond to a cantilever beam, as currently assumed or a cantilever plate. The Rx is also studied to assess the effects of compressional waves, the total damping of the BE system inside the medium on the actual evaluation of the shear wave velocity of the soil. In addition, the dependence of the output voltage from the Rx and the applied strain is investigated at different confining pressures. The thesis concludes with the dynamic characterization of a sensitive clay (Leda clay) that is present in large areas of Eastern Canada (Leda or Champlain sea clay) BE and RC tests are performed on unique undisturbed samples. All results presented in this study represent to the averages of multiple tests (more than 10 for RC and more than 500 for BEs). In all cases, the maximum coefficient of variance was 3 % which demonstrates the repeatability of the measurements. Contrary to a common assumption in BE testing, measurements on the transparent soil show that the Tx response inside the specimen is significantly different from the actual input voltage. In addition, BE measurements in soil and oil show that the time delay between input excitation and Tx response is not constant but it decreases with the increase in frequency. Results from the modal analysis of the Tx show a cantilever beam deformation (2D) only for the first mode of the Tx response in air and liquids; however, the response inside the soil specimen (no confinement) shows a cantilever plate behavior (3D). The excitation frequency in BE test should not be constant as commonly done; but it should be increased at each confinement level to match the increase in natural frequency and improve the signal-to-noise ratio. The overall damping ratio of the Tx increases up to 30% with confinement because of the soil-BE interaction, causing additional challenges in the evaluation of shear wave velocity and damping ratio from BE tests. The measured BE-system response shows a significant p-waves interference that affects the evaluation of the shear wave velocity. The p-wave interference must be carefully evaluated for the correct interpretation of the results. The p-wave interference is clearly observed when the Rx response is measured inside different liquids. This interference increases with the increase in the excitation frequencies. The Rx response in the transparent soil shows that participation of high frequencies and the interference of p-waves increases with increase in confinement. The p-wave arrivals mask the shear wave arrivals; which can lead to the overestimation of shear waves by more than 25 %. The results from the RC and BE tests on fused quartz and Leda clay specimens confirm the conclusion that high input frequencies enhance the generation of p-waves. The theoretical relationship between the maximum BE displacement and maximum input voltage for the Tx or the maximum output voltage for the Rx is verified for the first time for liquids and sands at no confining pressure. The peak displacements at the tip of the BE increased linearly with the input voltage because the maximum displacement in a piezo-electric transducer is proportional to the applied voltage. RC and BE tests performed on four Leda clay samples showed the effects of shear strain, confinement, and excitation frequency on shear modulus and damping ratio of the Leda clay. The effect of frequency is evaluated using a recently proposed methodology called the 'carrier frequency' (CF) method. The stiffest sample displayed the highest degradation with the increase in shear strain. There is a 15 % difference observed between the shear wave velocity estimates from RC and BE tests. The RC tests at frequencies below 100 Hz showed no effect of loading frequency on shear modulus and damping ratio; however, BE tests at frequencies centred at 12kHz did show a 15% change in wave velocity. This change could be attributed to the loading frequency or to the complex interaction of between p-waves and s-wave in BE testing. Loading frequency in BE tests does have a significant effect in the results, up to 40% error in the estimation of s-wave velocity, as the interaction between p-waves and s-waves increases with frequency.
Book Synopsis Combined Time and Frequency Domain Approach to the Interpretation of Bender-Element Tests on Sand by : Mark A. Styler
Download or read book Combined Time and Frequency Domain Approach to the Interpretation of Bender-Element Tests on Sand written by Mark A. Styler and published by . This book was released on 2013 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shear wave velocities are obtained from bender-element tests on laboratory specimens by analyzing the trigger and response signals. The response signal is a highly distorted translation of the trigger signal, obscuring the identification of the shear wave arrival. This has led to the publication of many criteria to guide subjective decisions on the selection of trigger waveform and frequency and of applicable interpretation methods. Current methods of interpretation result in determination of either the group or phase velocity. As soil and bender-element responses are dispersive, and as the group velocity is only valid in non-dispersive systems, the phase velocity should be measured. A combined time and frequency domain method is presented to allow interpretation of the phase velocity, minimizing subjective input to the interpretation. The method is first demonstrated using simplified synthetic signals and is then applied to laboratory test data. The reproducibility of the results is demonstrated from measurements on ten triaxial specimens of saturated Fraser River sand. The group velocities are shown to be very sensitive to dispersion, not reproducible, and contingent on the selected frequency window, whereas the phase velocities are considerably more repeatable. The combined time and frequency domain method results in the interpretation of a phase velocity using only measured parameters.
Book Synopsis Bender Elements and Bending Disks for Measurement of Shear and Compression Wave Velocities in Large Fully and Partially Saturated Sand Specimens by : E. Eseller-Bayat
Download or read book Bender Elements and Bending Disks for Measurement of Shear and Compression Wave Velocities in Large Fully and Partially Saturated Sand Specimens written by E. Eseller-Bayat and published by . This book was released on 2013 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bender element and bending disk setups were designed and implemented in a liquefaction box that accommodated a large sand specimen (190 mm × 300 mm × 490 mm). The box was manufactured for testing fully and partially saturated sand specimens under cyclic and earthquake excitation. Special housings for bender elements (31.8 mm × 12.7 mm × 0.51 mm) were manufactured to allow insertion of the elements through the side walls of the box. The bender elements were used to measure shear wave velocities in multiple directions to ascertain the uniformity of a sand specimen prepared in the liquefaction box. Large bending disks (31.8 mm × 0.41 mm) in special housings were utilized to measure compression wave velocities with the aim of investigating the presence and effect of the degree of partial saturation in specimens. The housings for bender elements and bending disks were designed to minimize the boundary effects of the Plexiglas walls of the liquefaction box. This paper provides details of the experimental setup and the designs of the bender element and bending disk housings. Sample test results of shear and compression wave measurements are also included to demonstrate successful application of the test setup. The experimental setup described is well suited for utilizing bender elements and bending disks for shear and compression wave velocity measurements in fully and partially saturated large sand specimens.
Book Synopsis Pre-failure Deformation Behaviour of Geomaterials by : R. J. Jardine
Download or read book Pre-failure Deformation Behaviour of Geomaterials written by R. J. Jardine and published by Thomas Telford. This book was released on 1998 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past fifteen years experimental and theoretical characterisation of the pre-failure deformation properties of geomaterials has developed enormously. In recognition of these important research developments a Geotechnique Symposium in Print (SIP) was held at the Institution of Civil Engineers in 1997. This volume brings together the nineteen Geotechnique SIP papers which summarise the recent developments in measuring and understanding the pre-failure stress-strain-time properties of natural soils, and apply this information to practical engineering problems.
Book Synopsis Unsaturated Soil Mechanics - from Theory to Practice by : Zhenghan Chen
Download or read book Unsaturated Soil Mechanics - from Theory to Practice written by Zhenghan Chen and published by CRC Press. This book was released on 2015-10-14 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past decades advances have been made in the research and practice on unsaturated soil mechanics. In 2000 the first Asia-Pacific Conferences on Unsaturated Soils was organized in Singapore. Since then, four conferences have been held under the continued support of the Technical Committee on Unsaturated Soils (TC106) of the International Socie
Book Synopsis Deformation Characteristics of Geomaterials by : H. DiBenedetto
Download or read book Deformation Characteristics of Geomaterials written by H. DiBenedetto and published by CRC Press. This book was released on 2005-03-03 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solutions for soil engineering and soil-structure interaction problems need realistic and pertinent experimental and modelling tools. In this work, extensive developments proposed by the invited speakers of the Lyon International Symposium held in September 2003 are presented, including experimental investigations into deformation properties; laboratory, in-situ and field observation interpretations; behaviour characterisation and modelling; and case histories. The contributions include recent investigations into anisotropy and non-linearity, the effects of stress-strain-time history, ageing and time effects, yielding, failure and flow, cyclic and dynamic behaviour. In addition, advanced geotechnical testing is applied to real engineering problems, and to ways of synthesising information from a range of sources while engaging in practical site characterisation studies.
Download or read book Géotechnique written by and published by . This book was released on 2008 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions by : Francesco Silvestri
Download or read book Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions written by Francesco Silvestri and published by CRC Press. This book was released on 2019-10-22 with total page 5946 pages. Available in PDF, EPUB and Kindle. Book excerpt: Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions contains invited, keynote and theme lectures and regular papers presented at the 7th International Conference on Earthquake Geotechnical Engineering (Rome, Italy, 17-20 June 2019. The contributions deal with recent developments and advancements as well as case histories, field monitoring, experimental characterization, physical and analytical modelling, and applications related to the variety of environmental phenomena induced by earthquakes in soils and their effects on engineered systems interacting with them. The book is divided in the sections below: Invited papers Keynote papers Theme lectures Special Session on Large Scale Testing Special Session on Liquefact Projects Special Session on Lessons learned from recent earthquakes Special Session on the Central Italy earthquake Regular papers Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions provides a significant up-to-date collection of recent experiences and developments, and aims at engineers, geologists and seismologists, consultants, public and private contractors, local national and international authorities, and to all those involved in research and practice related to Earthquake Geotechnical Engineering.
Download or read book Canadian Geotechnical Journal written by and published by . This book was released on 2012 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Unsaturated Soils, Two Volume Set by : Eduardo E. Alonso
Download or read book Unsaturated Soils, Two Volume Set written by Eduardo E. Alonso and published by CRC Press. This book was released on 2010-09-02 with total page 1532 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent decades the development of unsaturated soil mechanics has been remarkable, resulting in momentous advances in fundamental knowledge, testing techniques, computational procedures, prediction methodologies and geotechnical practice. The advances have spanned the full spectrum of theory and practice. In addition, unsaturated materials exhibiting complex behaviour such as residual soils, swelling soils, compacted soils, collapsing soils, tropical soils and solid wastes have been integrated in a common understanding of shared behaviour features. It is also noteworthy that unsaturated soil mechanics has proved surprisingly fruitful in expanding to other neighbouring areas such as swelling rocks, rockfill mechanics, and freezing soils. As a consequence, geotechnical engineering involving unsaturated soils can be now approached from a more rational and systematic perspective leading towards an improved and more effective practice. Unsaturated Soils contains the papers presented at the 5th International Conference on Unsaturated Soil (Barcelona, Spain, 6-8 September 2010). They report significant advances in the areas of unsaturated soil behaviour, testing techniques, constitutive and numerical modelling and applications. The areas of application include soil-atmosphere interaction, foundations, slopes, embankments, pavements, geoenviromental problems and emerging topics. They are complemented by three keynote lectures and three general reports covering general issues of modelling, testing and applications. Unsaturated Soils is a comprehensive record of the state-of-the art in unsaturated soil mechanics and a sound basis for further progress in the future. The two volumes will serve as an essential reference for academics, researchers and practitioners interested in unsaturated soils.
Book Synopsis Vibrations of Soils and Foundations by : Frank Edwin Richart
Download or read book Vibrations of Soils and Foundations written by Frank Edwin Richart and published by Prentice Hall. This book was released on 1970 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: For graduate students in soil dynamics with a background in statics and elementary dynamics.
