Soheil Nazarian

Bio: Soheil Nazarian is an academic researcher from University of Texas at El Paso. The author has contributed to research in topics: Subgrade & Asphalt concrete. The author has an hindex of 30, co-authored 346 publications receiving 4209 citations. Previous affiliations of Soheil Nazarian include Fugro & Texas A&M University.

Use of spectral analysis of surface waves method for determination of moduli and thicknesses of pavement systems.

Abstract: The spectal analysis of surface waves (SASW) method is a nondestructive method for determining moduli and thicknesses of pavement systems. By means of a transient impact on the surface of a pavement system (or soil deposit), a group of waves with different frequencies is transmitted to the medium. Seismic wave velocities and, eventually, elastic moduli and thicknesses of the various layers in the pavement system are determined from analysis of the phase information for each frequency determined between two receivers located on the surface. The method has several advantages: it is nondestructive, has a unique solution, and is capable of full automation. The results of three series of tests performed on TX-71 near Columbus, Texas, are presented. Testing was performed on an asphaltic concrete pavement, a continuously reinforced concrete pavement, and a natural soil occupying the median at the site. Elastic moduli determined by using the SASW method are compared with those determined by means of crosshole seismic tests and Dynaflect measurements. Moduli determined by the SASW method are in agreement with those from crosshole tests, whereas moduli back-calculated from Dynaflect measurements compare rather unfavorably with moduli determined by the other two methods.

Nondestructive testing to identify concrete bridge deck deterioration

Abstract: This work was sponsored by the Federal Highway Administration in cooperation with the American Association of State Highway and Transportation Officials. It was conducted in the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies. The project was managed by Monica Starnes, Senior Program Officer for SHRP 2 Renewal. The research reported herein was performed by the Center for Advanced Infrastructure and Transportation (CAIT) at Rutgers University (RU); the Center for Transportation Infrastructure Systems (CTIS) at The University of Texas at El Paso (UTEP); the Federal Institute for Materials Research and Testing (BAM), Germany; and Radar Systems International, Inc. (RSI). Rutgers University was the coordinator and contractor for this project. Dr. Nenad Gucunski, professor and chair of Civil and Environmental Engineering and director of CAIT’s Infrastructure Condition Monitoring Program at RU, was the principal investigator. The other authors of this report are Dr. Soheil Nazarian, professor of Civil Engineering and director of CTIS at UTEP; Dr. Deren Yuan, research associate at CTIS at UTEP; Dr. Herbert Wiggenhauser, head of Non-Destructive Testing (NDT) in Civil Engineering at BAM; Dr. Alexander Taffe, leader of Combination and Automation of NDT of Buildings at BAM; Dr. Parisa Shokouhi, Alexander von Humboldt Research Fellow, hosted by BAM; and Doria Kutrubes, president of RSI. Arezoo Imani and Touraj Tayebi, graduate research assistants at RU, helped conduct the validation testing, data analysis, and web manual content preparation. Hoda Azari, a graduate research assistant, and Dr. Manuel Celaya, a research engineer at UTEP, assisted in the validation study as well. Hooman Parvardeh, research assistant at RU, helped build the reference database and develop the framework for the web manual, while Erica Erlanger, a research staff member at RU, edited the manuscript. Their contributions are gratefully acknowledged. The research team also gratefully acknowledges contributions of the participants from industry and academia in the validation testing. The participants include NDT Corporation; Germann Instruments; Olson Engineering; Dr. Ralf Arndt, National Research Council associate at FHWA Turner–Fairbank Highway Research Center; Ingegneria Dei Sistemi S.p.A. (IDS), Italy; 3D-RADAR, Norway; Dr. John Popovics, University of Illinois at Urbana-Champaign; Dr. Jinying Zhu, The University of Texas at Austin; Rutgers University—Center for Advanced Infrastructure and Transportation; and The University of Texas at El Paso—Center for Transportation Infrastructure Systems. The contributions of these participants were critical for the evaluation and grading of the performance of NDT technologies.

Automated Surface Wave Method: Field Testing

Abstract: The spectral analysis of surface waves (SASW) method is a nondestructive in situ seismic testing method for determining shear wave velocity profiles of soil sites and stiffness profiles of pavement systems. The key steps involved are construction of an experimental dispersion curve from data collected in situ, and inversion of the dispersion curve to determine the stiffness profile. In this paper, an automated method for the construction of dispersion curves is discussed. Weighted least-squares best-fit solution is used to estimate the phase at each frequency with coherence as weighted function. By knowing the distance between the receivers and the phase at each frequency, phase velocity and wavelength associated with that frequency are calculated. These raw data are then combined using the least-absolute-value best-fit criterion to construct a dispersion curve. The inversion process for determination of stiffness profile from the dispersion curve is described in a companion paper.

Automated inversion procedure for spectral analysis of surface waves

Abstract: The usual inversion procedures for spectral analysis of surface waves (SASW) testing assume that only one Rayleigh mode is dominant, and thus fail to give reliable results for irregular soil profiles and some complex pavement systems. A new inversion algorithm is presented that is based on the numerical simulation of an actual SASW test, thus enabling the contributions of all types of waves and their modes to be taken into account. The algorithm also benefits from a nonlinear minimization technique in addition to the current linearized minimization to improve robustness of the inversion. Artificial irregular profiles, including a profile with a softer layer trapped between two stiffer layers, a profile with a stiffer layer sandwiched between two softer layers, and a profile with softer layers at larger depths, as well as two experimental pavement profiles have all been successfully inverted.

Automated surface wave method: Inversion technique

Abstract: The spectral‐analysis‐of‐surface‐waves (SASW) method is a nondestructive testing method based upon generation and detection of elastic stress waves. The key steps involved are construction of an experimental dispersion curve from data collected in situ, and inversion of the dispersion curve to determine the stiffness profile. An automated algorithm for determining the representative dispersion curve from field data has been presented in a companion paper. In most applications, the determination of the layer moduli are accomplished by using a manual trial and error process (forward modeling). Unfortunately, this process is rather time‐consuming and requires engineering judgement. To improve this aspect of SASW testing, an automated technique based upon the general inverse theory is described here. The technique provides a fast procedure for simultaneously determining shear wave velocity and thickness of different layers. In addition, some description of uncertainty in the determined results is provided.

Multichannel analysis of surface waves

Abstract: The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and characterizing the shallow subsurface. Most surface-wave analysis relies on the accurate calculation of phase velocities for the horizontally traveling fundamental-mode Rayleigh wave acquired by stepping out a pair of receivers at intervals based on calculated ground roll wavelengths. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the whole wave field. Among these nonplanar, nonfundamental-mode Rayleigh waves (noise) are body waves, scattered and nonsource-generated surface waves, and higher-mode surface waves. The degree to which each of these types of noise contaminates the dispersion curve and, ultimately, the inverted shear-wave velocity profile is dependent on frequency as well as distance from the source. Multichannel recording permits effective identification and isolation of noise according to distinctive traceto-trace coherency in arrival time and amplitude. An added advantage is the speed and redundancy of the measurement process. Decomposition of a multichannel record into a time variable-frequency format, similar to an uncorrelated Vibroseis record, permits analysis and display of each frequency component in a unique and continuous format. Coherent noise contamination can then be examined and its effects appraised in both frequency and offset space. Separation of frequency components permits real-time maximization of the S/N ratio during acquisition and subsequent processing steps. Linear separation of each ground roll frequency component allows calculation of phase velocities by simply measuring the linear slope of each frequency component. Breaks in coherent surface-wave arrivals, observable on the decomposed record, can be compensated for during acquisition and processing. Multichannel recording permits single-measurement surveying of a broad depth range, high levels of redundancy with a single field configuration, and the ability to adjust the offset, effectively reducing random or nonlinear noise introduced during recording. A multichannel shot gather decomposed into a sweptfrequency record allows the fast generation of an accurate dispersion curve. The accuracy of dispersion curves determined using this method is proven through field comparisons of the inverted shear-wave velocity (vs) profile with a downholevs profile.

Estimation of near‐surface shear‐wave velocity by inversion of Rayleigh waves

Abstract: The shear‐wave (S-wave) velocity of near‐surface materials (soil, rocks, pavement) and its effect on seismic‐wave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh‐wave phase velocity of a layered‐earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion‐curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high‐frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the weighted equation proved very effective in the high‐frequency range when using the Levenberg‐Marquardt and singular‐value decomposition techniques. Convergence of the weighted solution is guaranteed through selection of the damping factor using the Levenberg‐Marquardt method. Synthetic examples demonstrated calculation efficiency and stability ...

Liquefaction resistance of soils from shear-wave velocity

Abstract: A simplified procedure using shear-wave velocity measurements for evaluating the liquefaction resistance of soils is presented. The procedure was developed in cooperation with industry, researchers, and practitioners and evolved from workshops in 1996 and 1998. It follows the general format of the Seed-Idriss simplified procedure based on standard penetration test blow count and was developed using case history data from 26 earthquakes and >70 measurement sites in soils ranging from fine sand to sandy gravel with cobbles to profiles including silty clay layers. Liquefaction resistance curves were established by applying a modified relationship between the shear-wave velocity and cyclic stress ratio for the constant average cyclic shear strain suggested by R. Dobry. These curves correctly predicted moderate to high liquefaction potential for >95% of the liquefaction case histories and are shown to be consistent with the standard penetration test based curves in sandy soils. A case study is provided to illustrate application of the procedure. Additional data are needed, particularly from denser soil deposits shaken by stronger ground motions, to further validate the simplified procedure.