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Kallu R.R.,University of Nevada, Reno | Keffeler E.R.,RESPEC Consulting and Services | Watters R.J.,University of Nevada, Reno | Agharazi A.,Itasca Houston Inc.
International Journal of Mining Science and Technology | Year: 2015

Estimating weak rock mass modulus has historically proven difficult although this mechanical property is an important input to many types of geotechnical analyses. An empirical database of weak rock mass modulus with associated detailed geotechnical parameters was assembled from plate loading tests performed at underground mines in Nevada, the Bakhtiary Dam project, and Portugues Dam project. The database was used to assess the accuracy of published single-variate models and to develop a multivariate model for predicting in-situ weak rock mass modulus when limited geotechnical data are available. Only two of the published models were adequate for predicting modulus of weak rock masses over limited ranges of alteration intensities, and none of the models provided good estimates of modulus over a range of geotechnical properties. In light of this shortcoming, a multivariate model was developed from the weak rock mass modulus dataset, and the new model is exponential in form and has the following independent variables: (1) average block size or joint spacing, (2) field estimated rock strength, (3) discontinuity roughness, and (4) discontinuity infilling hardness. The multivariate model provided better estimates of modulus for both hard-blocky rock masses and intensely-altered rock masses. © 2015. Source

Roberts L.A.,South Dakota School of Mines and Technology | Buchholz S.A.,RESPEC Consulting and Services | Mellegard K.D.,RESPEC Consulting and Services | Dusterloh U.,Clausthal University of Technology
Rock Mechanics and Rock Engineering | Year: 2015

The Solution Mining Research Institute (SMRI) has embarked on inquiries into the effect cyclic loading might have on salt. This interest stems from the concept of using salt caverns as a storage medium for renewable energy projects such as compressed air energy storage where daily pressure cycles in the cavern are conceivable as opposed to the seasonal cycles that are typical for natural gas storage projects. RESPEC and the Institut für Aufbereitung und Deponietechnik at Clausthal University of Technology jointly executed a rock mechanics laboratory study using both facilities for performing triaxial cyclic loading creep tests on rock salt recovered from the Avery Island Mine in Louisiana, USA. The cyclic triaxial creep tests were performed under various load paths including compression, extension, and compression/extension. The tests were performed under both dilative and nondilative stress regimes. The cyclic compression creep data were compared to static creep tests performed under similar conditions to assess the effect of cycling of the applied stress. Furthermore, the cyclic compression tests were compared to a numerically simulated static creep test at the same stress and temperature conditions to determine if the creep behavior was similar under cyclic loading. © 2015, Springer-Verlag Wien. Source

Davis A.D.,South Dakota School of Mines and Technology | Webb C.J.,Western Kentucky University | Sorensen J.L.,RESPEC Consulting and Services | Dixon D.J.,South Dakota School of Mines and Technology | Betemariam H.,The Mosaic Company
Environmental Earth Sciences | Year: 2014

The Gilt Edge Superfund Site is a former heap-leach gold mine that currently is being remediated in the Black Hills of South Dakota. Mine runoff water is treated before release from the site. The field pH, before treatment, is about 3; the water contains arsenic at low levels and some trace metals at elevated levels, in addition to total dissolved solids concentrations of more than 1,900 mg/L. In the Keystone area of the Black Hills, naturally occurring arsenic has been detected at elevated concentrations in groundwater samples from wells. The City of Keystone's Roy Street Well, which is not used currently, showed arsenic concentrations of 36 parts per billion and total dissolved solids of 320 mg/L. With field samples of water from the Gilt Edge site, a limestone-based method was successful in reducing trace metals concentrations to about 0.001 mg/L or less; at the Keystone site, the limestone method reduced arsenic levels to about 0.006 mg/L. The results are significant because previous research with the limestone-based method mainly had involved samples prepared with distilled water in the laboratory, in which interference of other ions such as sulfate did not occur. The research indicates the potential for broader applications of the limestone-based removal method, including scale-up work at field sites for water treatment. © 2013 Springer-Verlag Berlin Heidelberg. Source

MacKenzie K.A.,Master Planning Program Manager | Nolle J.,RESPEC Consulting and Services | Leak A.,RESPEC Consulting and Services
International Low Impact Development Conference 2015 - LID: It Works in All Climates and Soils - Proceedings of the 2015 International Low Impact Development Conference | Year: 2015

The Denver High Line Canal is a 130-year-old irrigation channel that follows a 106 km (66 mi) serpentine path through the Denver urbanized region. While it once served to bring 200 km (500 mi) of semi-arid, high plains prairie into agricultural production, nearly all of that land has now urbanized, rendering much of the canal obsolete. With urbanization, the canal has become a treasured recreational trail, due in part to the impressive gallery of giant cottonwoods that have grown up along its banks over the past 90 years, providing a full canopy of shade in many areas. The canal is extremely inefficient at delivering water due to seepage, infiltration, evaporation, and evapotranspiration via the thirsty cottonwoods. Reasonably, these same things that make it bad for water delivery should make it good for stormwater pollutant reduction and runoff reduction. In 2014, the Urban Drainage and Flood Control District, Denver Water, and four local governments completed a feasibility study that confirmed the practicability of retrofitting the High Line Canal to provide stormwater quality enhancement and runoff reduction. Specific project outcomes included characterization of all watersheds that cross the canal; determination of the canal's treatment capacity; determination of infrastructure needed; estimation of the annual stormwater volume available for infiltration and evapotranspiration; estimation of capital, operational, and maintenance costs; evaluation of a framework for operating within the Colorado water rights administration system; conceptual design of a pilot project to further confirm the project feasibility; and identification of future steps for project implementation. Construction of two pilot projects is proposed to begin in 2015 and 2016. © 2015 American Society of Civil Engineers. Source

Davis A.D.,South Dakota School of Mines and Technology | Webb C.J.,Western Kentucky University | Sorensen J.L.,RESPEC Consulting and Services | Dixon D.J.,South Dakota School of Mines and Technology | Varajic B.,Western Kentucky University
2012 SME Annual Meeting and Exhibit 2012, SME 2012, Meeting Preprints | Year: 2012

Limestone-based material shows great promise for removal of arsenic from water. In laboratory tests, it has removed more than 95% or arsenic and more than 99% of cadmium and lead. In addition, the waste material appears to be suitable for recycling or disposal in an ordinary landfill. However, the efficiency of limestone for arsenic removal could be improved. Recent research has shown that iron treatment of limestone can enhance its arsenic-removal efficiency greatly, increasing its attractiveness as an alternative to other methods. Copyright © 2012 by SME. Source

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