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Maher H.,University of Nebraska at Omaha | Ferguson S.,University of Nebraska at Omaha | Korth R.,Terracon | Marshall J.,University of Nebraska at Omaha | Pickett L.,University of Nebraska at Omaha
Rocky Mountain Geology | Year: 2015

A distinctive strata-bound vein array occurs in the basal Pierre Shale exposed along the shores of Lake Francis Case, a reservoir on the Missouri River in south-central South Dakota. Typically 2-4 meters in thickness, the array consistently outcrops over a >50-km distance, a significant areal footprint. Ash layers define the upper and lower bounds of the vein array. Two, suborthogonal, preferred directions of vertical veins (northeast and southeast strike) define a regional pattern. By volume, vertical veins comprise 1-2% of the rock. Thinner, more discontinuous, and irregular horizontal veins also occur. Comparisons between array orientations and the joint/vein pattern in the immediately underlying marls of the top of the Niobrara Chalk identify distinct differences. Traverse data suggest that the vein arrays are characterized by uniform horizontal extension. Vertical veins in the array are typically 1-2 centimeters thick and contain massive jarosite, selenite, and fibrous gypsum. The abundance of jarosite and fibrous gypsum distinctly correlates with position in the weathering profile, and these phases are interpreted as due to replacement of original selenite during modern weathering. However, for initial vein array formation, the following suggests that they are not related to modern weathering and formed at depth: (1) a lack of correlation of vein width/frequency with position in the weathering profile; (2) the regional extent; (3) the consistent preferred orientations; (4) the uniform horizontal extension; and (5) the coarsegrained character of the selenite. The consistent strike pattern suggests influence of a regional stress field. The mechanism/timing of vein array formation is unclear. Formation due to diagenetic processes, which are especially significant in mud rocks, would explain the strata-bound character and isotropic horizontal strain and is considered most likely. Formation during glacial loading is one intriguing possibility. Localization of the vein array may be due to the organic-rich character of the host Burning Brule Member of the Sharon Springs Formation. © 2015 University of Wyoming.

Miller G.A.,University of Oklahoma | Tan N.K.,Terracon | Muraleetharan K.K.,University of Oklahoma
Geotechnical Special Publication | Year: 2012

Pre-bored monocell pressuremeter tests were conducted in a calibration chamber containing compacted low plasticity clayey silt. A miniature pressuremeter probe having a diameter of 15.2 mm and expandable length to diameter ratio of 8.5 was used; this provided a soil bed diameter (610 mm) to probe diameter ratio of 40. Pressuremeter tests were conducted under three different levels of net normal stress (103, 152, and 206 kPa) and four different levels of matric suction (nominally 15, 28, 38, and 48 kPa). This paper presents results of the pressuremeter tests with emphasis on the interpretation of elastic modulus and the influence of matric suction. Results indicate that the pressuremeter modulus is sensitive to the initial soil state as defined by the net normal stress, matric suction, and void ratio (or dry unit weight). © 2012 American Society of Civil Engineers.

Mokhtari S.,University of Central Florida | Mehdawi N.,University of Central Florida | Park S.-H.,Korea Infrastructure Safety and Technology Corporation | Sallam A.M.,Terracon | And 3 more authors.
Structural Health Monitoring | Year: 2014

The recent advances in sensing methods and data acquisition technologies have facilitated the collection of instrumentation data for continuous structural health monitoring (SHM). However, interpretation of raw sensor data, affected by various known and unknown environmental factors in field conditions is a challenging task. Structural systems are usually undetermined due to limited sensor data that are not sufficient for finding explicit relations between system inputs and outputs. This study aims to introduce a data-driven methodology using response-only data for underdetermined structural systems. The Principle Component Analysis (PCA) as a Blind Source Separation (BSS) method has been used to decompose the mixed raw response data into a linear combination of statistically uncorrelated mode shapes of input data. Being a datadriven method, the proposed framework is not limited in application to a specific sensor type. To evaluate the efficiency of the method in practice, the close proximity excavation effects of a new tunnel on an existing tunnel has been considered. The analysis results show that the method is not only able to decompose measurements into excavation-induced and the environment-induced deformations but also the calculated eigen-parameters can be used as excellent indicators of structural behaviors during excavation by visualizing the tunnel lining deformations. © The Society for Experimental Mechanics, Inc. 2014.

Wu T.H.,Ohio State University | Gale S.M.,01 Twelve Oaks Center Dr | Zhou S.Z.,Terracon | Geiger E.C.,Office of Geotech. Engineering
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2011

A geotextile-reinforced embankment was built over soft ground. Staged construction and vertical prefabricated drains were used to obtain strength gain via consolidation of the foundation material. Settlement and pore pressure were measured as a part of construction control. Settlement, differential settlement, and rate of consolidation were predicted by simple models. Uncertainties in the predictions were evaluated to assess the reliability of the predictions. The estimated errors were compared with the measured values, and major contributors to prediction errors were identified. © 2011 American Society of Civil Engineers.

Shu S.,Terracon | Muhunthan B.,Washington State University | Li X.S.,Hong Kong University of Science and Technology
International Journal of Geomechanics | Year: 2011

This paper presents a state-dependent constitutive model for sand formulated within the critical-state framework and its implementation into a numerical analysis (FLAC3D) program. The implemented model was verified by using drained triaxial results on sands. The proposed model is shown to capture the stress path dependent behavior of sand over a wide range of densities and confining pressures well based on a unique set of parameters. Numerical simulations of the behavior of a micropile under vertical loading shows that the side and tip resistance, and thus the total resistance of the pile, are functions of the "in situ state" of soil as defined by the state parameter ψ=e-ec in which e is the void ratio and ec the void ratio at the critical state. © 2011 American Society of Civil Engineers.

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