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.

Download or read book A Framework Interpreting Bender Element Tests Combining Time Domain and Frequency Domain Methods written by António Viana da Fonseca and published by . This book was released on 2009 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bender element (BE) testing is a powerful and increasingly common laboratory technique for determining the shear S-wave velocity of geomaterials. There are several advantages of BE testing, but there is no standard developed for the testing procedures or for the interpretation of the results. This leads to high degree of uncertainty and subjectivity in the interpretation. In this paper, the authors review the most common methods for the interpretation of BE tests, discuss some important technical requirements to minimize errors, and propose a practical framework for BE testing, based on the comparison of different interpretation techniques in order to obtain the most reliable value for the travel time. This new procedure consists of the application of a methodical, systematic, and objective approach for the interpretation of the results, in the time and frequency domains. The use of an automated tool enables unbiased information to be obtained regarding variations in the results to assist in the decision of the travel time. Two natural soils were tested: residual soil from Porto granite, and Toyoura sand. Specimens were subjected to the same isotropic stress conditions and the results obtained provided insights on the effects of soil type and confining stress on the interpretation of BE results; namely, the differences in testing dry versus saturated soils, and in testing uniform versus well-graded soils.

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.

Download or read book Push Pull Tests for Site Characterization written by Jonathan David Istok and published by Springer Science & Business Media. This book was released on 2012-09-18 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: The push-pull test is a powerful site characterization technique that has been applied to a wide range of problems in contaminant hydrogeology. The theoretical and practical apsects of push-pull testing were initially developed to characterize groundwater acquifers but the method has now been extended to saturated and unsaturated soils and sediments as well as to surface water bodies. Dr. Istok and his collaborators have been instrumental in the development of these techniques and he is widely recognized as the world's leading expert push-pull testing. This is the only reference book available on this powerful method.

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.

Download or read book Laboratory Tests for Unsaturated Soils written by Eng-Choon Leong and published by CRC Press. This book was released on 2023-02-16 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: The testing of unsaturated soils requires greater care and effort than that of saturated soils. Although unsaturated soil mechanics has been embraced by geotechnical engineering, engineering practice has not yet caught up as the characterization of unsaturated soils is difficult and time-consuming, and made harder still by a lack of standards. Laboratory Tests for Unsaturated Soils collates test procedures to cover all laboratory tests for characterising unsaturated soils. It covers the background, theory, test procedures, and interpretation of test results. Each test procedure is broken down into simple stages and described in detail. The pitfalls of each test and the interpretation of the test results are explained. Test data and calculation methods are given, along with many numerical examples to illustrate the methods of interpretation and to offer the presentation of typical results. The book is especially useful for students and researchers who are new to the field and provides a practical handbook for engineering applications.

Download or read book Modeling a Bender Element Test Using Abaqus Finite Element Program written by Sean Michael Johnson and published by . This book was released on 2011 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: Finite Element Methods hold promise for modeling the behavior of an unsaturated soil specimen subjected to bender element agitation. The immediate objective of this research project is to reproduce a bender element test using Abaqus Finite Element Software assuming elastic and isotropic conditions. Extensive compressions were made of bender element testing of unsaturated Ticino Sand specimens uniaxially compressed and the Abaqus Finite Element Method program simulation. The research determined that the mesh resolution of a numerical analysis are optimal at a resolution of a twentieth of the shear wavelength and the integration time step has a negligible effect on the observed wave velocity. Moreover, it is possible to reproduce an uniaxially stressed bender element experiments of unsaturated Ticino sand in an Abaqus Finite Element Method program with relatively minimal error of the body wave velocity measurements if the source receiver distance is beyond two shear wavelengths and the reflected signals from the boundaries are suppressed.

Download or read book Particulate Discrete Element Modelling written by Catherine O'Sullivan and published by CRC Press. This book was released on 2011-04-06 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first single work on DEM providing the information to get started with this powerful numerical modelling approach. Provides the basic details of the numerical method and the approaches used to interpret the results of DEM simulations. It will be of use to professionals, researchers and higher level students, with a theoretical overview of DEM as well as practical guidance.Selected Contents: 1.Introduction 2.Use of DEM in Geomechanics 3.Calculation of Contact Forces 4.Particle Motion 5.Particle Types 6.Boundary Conditions 7.Initial Geometry and Specimen Generation 8.Time Integration and Discrete Element Modelling 9.DEM Interpretation: A Continuum Perspective 10.Postprocessing: Graphical Interpretation of DEM Simulations 11.Basic Statisti

Download or read book Advances in Geotechnical and Transportation Engineering written by Sireesh Saride and published by Springer Nature. This book was released on 2020-04-09 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the selected peer-reviewed papers from the national conference Futuristic Approaches in Civil Engineering (FACE) 2019. This volume focuses on latest research and challenges in the field of geotechnical, transportation, environmental and water resources engineering. The first part focuses on alternative and sustainable pavement materials, maintenance and rehabilitation of roads, transportation planning, traffic engineering, hybrid vehicles, safety management, and intelligent transport systems. In the second part of the book, basic and advanced research in geotechnical engineering which can provide sustainable solutions to practical problems in foundations, retaining structures, soil dynamics, site characterization, slope stability, dams, rock engineering, environmental geotechnics, and geosynthetics are covered. The third part of the book includes current research in environment, and water resources engineering. The contents of this book will be useful for students, researchers as well as industry professionals.

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.

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.

Download or read book Soil Behaviour in Earthquake Geotechnics written by Kenji Ishihara and published by Oxford University Press, USA. This book was released on 1996 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: This highly topical book, written by a leading Japanese author, provides a comprehensive study of current research in soil dynamics for earthquake engineering. The behaviour of the ground on which structures are built during earthquake conditions is crucial to understanding the behaviour of those structures. This well-illustrated text summarizes current knowledge of the subject, presenting material accumulated by Japanese and other researchers over recent years. It comprehensively covers theory, laboratory tests, and field work. It also includes helpful guidelines for civil engineers undertaking groundwork to protect structures in potential earthquake zones.

Download or read book Numerical Models in Geomechanics written by G.N. Pande and published by CRC Press. This book was released on 2020-12-17 with total page 691 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this volume a number of developments on a variety of topics have been reported. These topics include: partially saturated soil; instabilities in soil behaviour; environmental geomechanics; parallel computing; and applications to tunnels, embankments, slopes, foundations and anchors.

Download or read book Dynamic Geotechnical Testing written by M. L. Silver and published by ASTM International. This book was released on 1978 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pre failure Deformation Characteristics of Geomaterials written by M. Jamiolkowski and published by CRC Press. This book was released on 1999 with total page 968 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrical Measuring Instruments and Measurements written by S.C. Bhargava and published by CRC Press. This book was released on 2012-12-27 with total page 1888 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, written for the benefit of engineering students and practicing engineers alike, is the culmination of the author's four decades of experience related to the subject of electrical measurements, comprising nearly 30 years of experimental research and more than 15 years of teaching at several engineering institutions. The unique feature of this book, apart from covering the syllabi of various universities, is the style of presentation of all important aspects and features of electrical measurements, with neatly and clearly drawn figures, diagrams and colour and b/w photos that illustrate details of instruments among other things, making the text easy to follow and comprehend. Enhancing the chapters are interspersed explanatory comments and, where necessary, footnotes to help better understanding of the chapter contents. Also, each chapter begins with a "recall" to link the subject matter with the related science or phenomenon and fundamental background. The first few chapters of the book comprise "Units, Dimensions and Standards"; "Electricity, Magnetism and Electromagnetism" and "Network Analysis". These topics form the basics of electrical measurements and provide a better understanding of the main topics discussed in later chapters. The last two chapters represent valuable assets of the book, and relate to (a) "Magnetic Measurements", describing many unique features not easily available elsewhere, a good study of which is essential for the design and development of most electric equipment – from motors to transformers and alternators, and (b) "Measurement of Non-electrical Quantities", dealing extensively with the measuring techniques of a number of variables that constitute an important requirement of engineering measurement practices. The book is supplemented by ten appendices covering various aspects dealing with the art and science of electrical measurement and of relevance to some of the topics in main chapters. Other useful features of the book include an elaborate chapter-by-chapter list of symbols, worked examples, exercises and quiz questions at the end of each chapter, and extensive authors' and subject index. This book will be of interest to all students taking courses in electrical measurements as a part of a B.Tech. in electrical engineering. Professionals in the field of electrical engineering will also find the book of use.

Download or read book Geohazards written by Madhavi Latha Gali and published by Springer Nature. This book was released on 2020-08-13 with total page 763 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume comprises select papers presented during the Indian Geotechnical Conference 2018. This volume discusses concepts of soil dynamics and studies related to earthquake geotechnical engineering, slope stability, and landslides. The papers presented in this volume analyze failures connected to geotechnical and geological origins to improve professional practice, codes of analysis and design. This volume will prove useful to researchers and practitioners alike.