Geotechnical and Geomechanical Characterisation of the Goathill North Rock Pile at the Questa Molybdenum Mine, New Mexico, USA

Gutierrez, Luiza A. F.; Viterbo, Vanesssa; McLemore, Virginia T.; Aimone-Martin, C. A.

doi:10.36487/acg_repo/802_2

Cited by 3 publications

(12 citation statements)

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“…While even a small amount of compaction will increase the density and strength of the soil, the angle of repose is a conservative estimate of the friction angle. Similar values of / and c for loose spoils in the Appalachian region were reported by Sweigard et al (2011), while similar values for reclaimed spoils outside the Appalachian were found in the literature (Ulusay et al 1995;Stormont and Farfan 2005;Kasmer and Ulusay 2006;Gutierrez et al 2008;Sweigard et al 2011) as summarized in Table 4.…”

Section: Shear Strength Parameterssupporting

confidence: 85%

The Low Compaction Grading Technique on Steep Reclaimed Slopes: Soil Characterization and Static Slope Stability

2013

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Since the Surface Mining and Control Reclamation Act of 1977, US coal mining companies have been required by law to restore the approximate ground contours that existed prior to mining. To ensure mass stability and limit erosion, the reclaimed materials have traditionally been placed with significant compaction energy. The Forest Reclamation Approach (FRA) is a relatively new approach that has been successfully used to facilitate the fast establishment of native healthy forests. The FRA method specifies the use of low compaction energy in the top 1.2-1.5 m of the contour, which may be in conflict with general considerations for mechanical slope stability. Although successful for reforestation, the stability of FRA slopes has not been fully investigated and a rational stability method has not been identified. Further, a mechanics-based analysis is limited due to the significant amount of oversize particles which makes the sampling and measurement of soil strength properties difficult. To investigate the stability of steep FRA slopes (steeper than 20°), three reclaimed coal mining sites in the Appalachian region of East Tennessee were investigated. The stability was evaluated by several methods to identify the predominant failure modes. The infinite slope method, coupled with the estimation of the shear strength from field observations, was shown to provide a rational means to evaluate the stability of FRA slopes. The analysis results suggest that the low compaction of the surface materials may not compromise the long-term stability for the sites and material properties investigated.

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Section: Shear Strength Parameterssupporting

confidence: 85%

The Low Compaction Grading Technique on Steep Reclaimed Slopes: Soil Characterization and Static Slope Stability

2013

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“…and "weak zone" at GHN and their gradation results (Robertson GeoConsultants, Inc., 2000b;URS Corporation, 2003;Norwest Corporation, 2004) (Franklin and Chandra, 1972) (Broch and Franklin, 1972) Molling, 1989;Shum, 1999;Piché and Jébrak, 2004;Plumlee et al, 2006). Gutierrez, 2006;Gutierrez et al, 2008;Boakye, 2008). Histograms and statistical analysis are in Appendix 11 .... 173 TABLE 41.…”

Section: List Of Figuresmentioning

confidence: 99%

“…Histograms and statistical analysis are in Appendix 11 .... 173 TABLE 41. Summary of ultimate (or residual) friction angle form direct shear tests of samples from GHN by geologic units, normal stress of 160-750 kPa (modified from Gutierrez, 2006;Gutierrez et al, 2008;Boakye, 2008)…”

Section: List Of Figuresmentioning

confidence: 99%

“…Direct shear tests were performed at NMIMT (ASTM test procedure D 3080-98; Gutierrez, 2006) and at UBC. At NMIMT, direct shear tests were performed in a 2-inch shear box using dry samples from GHN with densities ranging from 1.60 to 1.84 g/cm 3 , 0.02 in/min displacement rate, and normal load varying from 100 to 500 KPa (Gutierrez, 2006;Gutierrez et al, 2008). At UBC, direct shear tests were performed in a 4-inch shear box using saturated samples at loads ranging from 60 to 500 kPa (G. W. Wilson, written communication, Sept. 2005).…”

Section: Analytical Proceduresmentioning

confidence: 99%

“…A simple weathering index (SWI) was developed to differentiate the weathering intensity of Questa rock-pile materials (SWI=1, fresh to SWI=5, most weathered; Table 24; Gutierrez et al, 2008). The five classes described in Table 24 describes the SWI classification for the soil matrix at the Questa mine based on relative intensity of both physical and chemical weathering (modified in part from Little, 1969;Gupta and Rao, 2000;Blowes and Jambor, 1990).…”

Section: Simple Weathering Indexmentioning

confidence: 99%

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Characterization of Goathill North Rock Pile, New Mexico

McLemore,

Ayakway,

Boakue

et al. 2009

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Nineteen trenches were constructed in the Goathill North (GHN) rock pile as it was regraded in [2004][2005]. The regrading of GHN provided a rare opportunity to examine, map, and sample the interior of this rock pile. The GHN rock pile is stratified and the strata can be correlated down slope through the rock pile. Rock fragment lithology is generally consistent within mapped units and correlates well with mineralogy and chemistry. Detailed geologic mapping and sampling revealed mappable geologic units in the rock pile, which were correlated between benches and to opposite sides of each trench, and units were correlated down slope through the excavated trenches. Units were defined on the basis of particle size, color, texture, stratigraphic position, lithology, and other physical properties that could be determined in the field. Eighteen geologic units were differentiated, described, and sampled. The units also could be distinguished within the adjacent drill holes.Weathering is the set of physical and chemical changes, up to and including disintegration of rock by physical, chemical, and/or biological processes occurring at or near the earth's surface (e.g. in the vadose zone at temperatures less than or equal to approximately 70°C) that result in reductions of grain size, changes in cohesion or cementation, and changes in mineralogical composition. In this operational definition, there is no clear distinction between weathering and diagenesis, although the coarse-grained and subaerial nature of the mined rock pile restricts the nature of "diagenetic" reactions compared to, for example, those that might occur in a submarine, saturated system. From this mapping and analyses of samples, four different zones of weathering can be distinguished at GHN:• outer oxidized zone (included the surface, unit C, and geologic units I and J)• intermediate zone (included unit N)• inner, less oxidized, unweathered zone (included units K-W)• basal oxidized zone (included geologic units R and rubble zone). The regrading of GHN provided a rare opportunity to examine, map, and sample the interior of this rock pile. The GHN rock pile is stratified and the strata can be correlated down slope through the rock pile. Rock fragment lithology is generally consistent within mapped units and correlates well with mineralogy and chemistry. The majority of geochemical activity appears to be confined to the interface regions of the rock pile, but not all of these regions exhibit weathering effects. The areas most affected by weathering processes are the 1) surfaceatmosphere, 2) bedrock-rock pile (rubble zone) areas, and 3) interfaces between fine-and coarsegrained layers in the interior zones where water and/or humid air flow and oxidize the rock pile material. Weathering generally decreased from the outer edge of the rock pile to its interior and then increased toward the base of the rock pile. Where water and oxygen are available, pyrite and calcite are being dissolved by weathering to form gypsum, jarosite and other soluble Fe salts. Oxygen an...

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