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Nasseri-Moghaddam A.,Inspec Sol Inc. | Park C.B.,Park Seismic LLC
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2010

The effect of source offset distance and the geophone array length on the dispersion curves are discussed in this paper. The source offset distance was changed systematically at sites with various subsurface conditions to investigate its effect on quality of data and the corresponding dispersion curves. Further, tests were carried out at same locations with various geophone intervals to evaluate the effect of the array length on the quality of the data and dispersion curves. Active and passive data were collected and the dispersion images were combined for possible improvement in dispersion image with enhanced multimodal delineation over a broadened bandwidth. It is observed that source offsets in the range of 25% to 45% of the array length provide dispersion curves with reasonable quality. Further, collecting data with different geophone intervals (same array mid station) improves the resolution of the obtained dispersion image. Multi geometry technique is suggested to obtain better quality field data. In this approach two (or more) different geophone intervals are used with same mid station. Passive and active data at two or more offset distances are collected for each of the array geometries. Stacking the obtained dispersion images can also result in a better quality dispersion curve. Source


Khayat K.H.,Universite de Sherbrooke | Hwang S.-D.,Universite de Sherbrooke | Belaid K.,Inspec Sol Inc.
ACI Materials Journal | Year: 2010

Viscosity-enhancing admixtures (VEAs) are water-soluble polymers that increase viscosity and cohesion of cement-based materials. Such enhancement is essential in highly flowable concrete including self-consolidating concrete (SCC) - to control the risk of segregation. For a given mixture composition, the performance of SCC can widely vary with the type and dosage rate of the VEA in use. The main objective of this investigation is to compare the performance of five VEA systems in SCC. More specifically, the investigation seeks to determine the effect of VEA type on key workability and engineering properties of SCC designated for cast-in-place building applications. The concrete is designed with a characteristic compressive strength of 35 MPa (5076 psi) at 28 days. In total, five VEAs incorporated with two compatible high-range water-reducing admixtures (HRWRAs) are investigated. A finely ground limestone filler that can be used as a stabilizer in flowable concrete is also included in the study. Copyright © 2010, American Concrete Institute. All rights reserved. Source


Bouzoubaa N.,CANMET Energy | Bilodeau A.,CANMET Energy | Tamtsia B.,Inspec Sol Inc. | Foo S.,Public Works and Government Services Canada
Canadian Journal of Civil Engineering | Year: 2010

The present study consists of investigating the carbonation resistance of two series of concrete mixtures designed for three classes of concrete (25, 35, and 45 MPa compressive strength at 28 d) and using American Society for Testing and Materials (ASTM) type I Portland cement and two commercially used fly ashes meeting the ASTM standards at the level of 20%, 35%, and 50% of the total weight of cementitious materials. The carbonation resistance was determined on samples moist cured for 3, 7, and 10 d and exposed to a CO2-enriched environment (3% CO2 at 23 °C and 65% relative humidity) for 140 d to accelerate the carbonation; it was also determined on samples moist cured for 7 d and exposed to an indoor and outdoor natural environments for 4 years. A mathematical model allowing the prediction of the depth of accelerated carbonation of fly ash concrete mixtures is presented. Source


Xie P.,Intel Corporation | Grant S.L.,Missouri University of Science and Technology | Anderson N.L.,Missouri University of Science and Technology | Nasseri-Mohgaddam A.,Inspec Sol Inc.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2014

This paper investigates challenges faced by many geophysical algorithms applied to real-world cases such as the Attenuation Analysis of Rayleigh Waves (AARW). AARW shows great promise in terms of detecting shallow underground tunnels. However, in-situ subsurface anomalies, including those due to anisotropy, and instrument sensitivity to natural conditions can significantly degrade the utility of this technique. To address this problem, this work proposes a data acquisition scheme and develops a new post-processing approach. The first applied measure estimates the confidence level of each detection result. The second processes the data in sub-arrays, and filters out false alarms. The third scans all detections and searches the cluster with the highest cumulative confidence level. This paper provides engineering practitioners with a simple and efficient method to reliably determine tunnel locations. Experimental results derived from data recorded in various testing sites and surface conditions verify the effectiveness of this work. © 2014 IEEE. Source


Xie P.,Missouri University of Science and Technology | Grant S.,Missouri University of Science and Technology | Putnam N.,Missouri University of Science and Technology | Anderson N.,Missouri University of Science and Technology | Nasseri-Moghaddam A.,Inspec Sol Inc.
2012 14th International Conference on Ground Penetrating Radar, GPR 2012 | Year: 2012

This paper investigates challenges faced by many geophysical algorithms applied to real-world cases such as the Attenuation Analysis of Rayleigh Waves (AARW). AARW shows great promise in terms of detecting shallow underground tunnels. However, in-situ subsurface anomalies, including those due to anisotropy, and instrument sensitivity to natural conditions can significantly degrade the utility of this technique. The first applied measure estimates the confidence level of each detection result. The second processes the recorded data in sub-arrays, acting as a filter to remove false alarms. The third scans all detections and searches the cluster with the highest cumulative confidence level. A case study is presented to demonstrate the effectiveness of AARW along with post-processing quality control measures. This work provides engineering practitioners with a simple and efficient method to reliably determine tunnel locations. ©2012 IEEE. Source

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