DRA-42 NMIMT LABORATORY DIRECT SHEAR TESTS ON THE ... · shear test apparatus in the Soil Mechanics Laboratory of NMIMT (SOP 50). Most samples were air-dried material, passed No

DRA-42

Questa Weathering Study p 1 of 28 February 16, 2009

DRA-42. NMIMT LABORATORY DIRECT SHEAR TESTS ON THE MATERIALS FROM QUESTA MINE ROCK PILES AND ANALOGS

A. Fakhimi, V. T. McLemore, S. Nunoo, K. Anim, and L. Gutierrez, March 28, 2008, revised February 16, 2009 (reviewed by D. van Zyl) 1. STATEMENT OF THE PROBLEM What is the shear strength of Questa mine materials? How does the shear strength change between the rock-pile materials and the older natural analog materials? This DRA reports the results of direct shear tests on Questa rock-pile and analog materials to measure the friction angle and cohesion that were conducted at NMIMT. Friction angle and cohesion are important geotechnical parameters that control the stability of the rock piles. 2. PREVIOUS WORK A comprehensive geotechnical characterization has been conducted in the last few years to evaluate the shear strength of Questa rock-pile and analog materials (presented in more detail in DRA 44). URS Corporation (2003) reports the results of a number of shear tests on Questa rock-pile materials, using 12-inch wide and 2.4-inch diameter shear boxes that were conducted by AMEC geotechnical laboratory and Advanced Terra Testing in Arizona and Colorado, respectively. The tests were performed under different normal stresses ranging from 119.7 to 478.8 kPa (2.5 to 10 ksf) and 98.6 to 526.7 kPa (2.06 to 11ksf) for 12-inch and 2.4-inch samples, respectively. The materials of minus-1.5 inch for the 12-inch box and minus-No. 4 sieve for 2.4-inch diameter box were used for the shear tests. The materials for 12-inch samples were prepared using dry densities ranging from 1522 to 1682 kg/m3 (95 to 105 pcf) at water contents ranging from 8 to 12%. The 2.4-inch samples had dry densities of 1522 to 1890 kg/m3 (95 to 118 pcf) and water contents of 10 to 14%. The friction angle and cohesion for 12-inch shear box ranged from 26º to 59º and 0 to 111 kPa, respectively. For the 2.4-inch shear box, the friction angle and cohesion ranged from 30º to 41º and 0 to 34 kPa, respectively. Based on the above shear test results, URS Corporation (2003) concluded that as larger particles are allowed to be present in the shear box, higher shear strengths are obtained; therefore scalping of the Questa rock-pile material causes reduction in the measured shear strengths.

Some direct shear tests were conducted by Azam and Wilson (2006) on saturated samples from Goathill North (GHN) rock pile and shear zone (samples from toe of the slope) (presented in more detail in DRA-43). The shear box was 100 mm × 100 mm × 45 mm in size and normal stresses of 60, 120, 250, and 500 kPa were used. The minus No. 4 sieve material was compacted in three layers to a dry density of 1700 kg/m3, allowed to become saturated overnight, and then sheared at a shear displacement rate of 0.05 to 0.1 mm/min. The peak friction angles and cohesions reported from this study were 36° to 45° and 0.3 to 3.1 kPa, respectively. The authors reported that the mean friction angle decreased by approximately 7° (from 39.6° to 32.7° for the peak and from 33.3° to 26.1° for the residual) for samples collected from the shear zone.

Norwest Corporation (2005) reported the results of isotropically consolidated undrained triaxial tests performed by Thurber Engineering Ltd using a 6-inch diameter triaxial apparatus (additional detail presented in DRA-45). Minus 1.5-inch rock-pile

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material was used and compacted to a target density of 1922 kg/m3 (120 pcf) at 5 % and 9 % water contents. Effective confining pressures of 68.9, 344.7, 689.5, 1379, and 2757.9 kPa (10, 50, 100, 200 and 400 psi) were used for the tests. Figure 1-1 (Appendix 1) summarize the results of direct shear tests and triaxial tests reported by Norwest Corporation (2005), suggesting higher friction angles for the 12-inch shear box.

Some laboratory direct shear tests have been performed on the pure minerals such as gypsum as well. The results of these shear tests are similar to the Questa rock-pile and analog materials and are reported in McLemore et al. (2007). 3. TECHNICAL APPROACH Samples were collected specifically for examining relationships between friction angle and mineralogy, chemistry, lithology, geotechnical parameters, and weathering. Several different types of samples were collected:

• Samples of the rock-pile material (5 ft channel or selected layers), including 5 of the 9 rock piles (Goathill North, Sugar Shack West, Spring Gulch, Sugar Shack South, Middle) and analogs (Alteration scars and debris flow)

• Soil profiles and selected samples of colluvium, alteration scars, and debris flows (analog materials)

• Outcrop samples of unweathered (or least weathered) igneous rocks representative of the mined rock before emplacement into the rock piles.

The regrading of GHN rock pile brought a unique opportunity to examine the undisturbed internal geology of the rock pile through the construction of trenches cut into the pile as earth-moving progressed. The collected samples from the rock piles consisted of a heterogeneous mixture of rock fragments ranging in size from boulders (0.5 m) to <1 mm in diameter within a fine-grained soil matrix. Most rock fragments were hydrothermally altered before mining occurred; some are oxidized and weathered since emplacement in the rock pile. The Questa mine materials that were tested are classified as GC, GP-GC, GW-GC, SC, GP-GM, GW-GM, and SP-SC in the Unified Soil Classification System. The liquid limit and plasticity index of the materials were in the range of 19 to 51 and 0 to 25, respectively.

A total of 178 samples (more than 600 shear tests) were tested using the direct shear test apparatus in the Soil Mechanics Laboratory of NMIMT (SOP 50). Most samples were air-dried material, passed No. 6 sieve and were compacted to a dry density mostly in the range of 1600-1900 kg/m3. The shear box was 5 cm (2 inch) wide, even though for a few samples a 10 cm (4 inch) shear box was used by Gutierrez (2006) for shear testing of wet and air-dried samples. A shear displacement rate of 8.5×10-3 mm/sec

(0.02 in/min) was used for the tests. Two sets of normal stresses of 20 to 120 kPa (low normal stress) and 160 to 750

kPa (high normal stress) were used in order to investigate the shear strength of the Questa mine materials within a wide range of normal stresses. The friction angles and cohesion intercepts obtained are reported for low and high normal stress ranges separately in this DRA.

One limitation of direct shear testing is the inability to control or monitor the pore water pressure. A few tests were performed with different water contents by Gutierrez

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(2006) and it was decided by the Questa Geotechnical Team to perform tests on air-dried samples.

Another limitation identified was the size of the shear box used. Gutierrez (2006) tested a few samples in both 5-cm (2-inch) and 10-cm (4-inch) boxes and determined that the results were relatively similar (no major size effect for changing the box size of 2 inch to 4 inch). A 2-inch box was chosen because a wider range of normal stresses could be applied using this shear box.

In order to verify the accuracy of the adopted procedure, some samples were tested in duplicate or triplicate. In addition, tests were conducted using a 2.5-inch calibrated ELE direct shear testing apparatus at Kleinfelder Laboratory in Albuquerque, NM. The proving ring for this motorized apparatus is annually calibrated. The purpose of these tests was to validate the tests conducted with the manual Soiltest shear box machine in the NMIMT Soil Mechanics Laboratory. The Mohr-Coulomb diagrams for samples GHN-KMD-0014 and GNH-KMD-0017 tested using both machines are shown in Figures 2-1 and 2-2 (Appendix 2). The shear test results using the ELE machine fell along the trend lines defined by data generated with the machine at NMIMT. The addition of the corroborating data did not change the φ values. Therefore, the test results obtained at NMIMT are considered to be representative and reproducible.

4. CONCEPTUAL MODEL The well known Mohr-Coulomb failure criterion was used to interpret the shear test results. This failure criterion has two constants, namely cohesion (c) and friction angle (φ). Since most of the shear tests were conducted on air-dried material, two interpretations of Mohr-Coulomb failure criterion were used in obtaining the shear strength of the material for the range of normal stress of 160-750 kPa. In the first interpretation of the test results used in this DRA, the failure envelope was defined as the best straight line that passed through the four normal stress-shear strength data points, while in the second approach, this best line was forced to pass through the origin resulting in zero cohesion intercept (Gutierrez, 2006). The difference in the calculated friction angles in these two approaches in most situations is less than 3°.

A non-linear Coulomb failure criterion (Equation 1) also was used to interpret the shear strength of the material (Charles and Watts, 1980), τ = Aσn

b (1)

In equation (1), A and b are material constants, and σn is the applied normal stress in a shear test. This failure criterion is more practical if a wide range of normal stresses is used. According to equation (1), as the normal stress increases, the corresponding shear strength does not grow linearly, possibly due to the particle breakage. This non-linear failure criterion was successfully used by Linero et al (2007) in describing the shear strength of some rock piles in Chile. Note that materials with higher resistance generally have higher values of A. The b parameter determines the curvature of the failure envelope.

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5. STATUS OF COMPONENT INVESTIGATION • The friction angle of all rock–pile materials is 35.3° to 49.3° with the mean of

42.2o and the standard deviation of 2.9o (Table 3-3, Appendix 3). The peak friction angle of this report is higher than the friction angles of 32° to 44° (Figure 1-1, Appendix 1) reported by Norwest Corporation (2005) that were obtained from laboratory direct shear tests (2.4 inch in size). One reason for this difference is that most tests at NMIMT were conducted on air-dried samples that rules out moisture softening effects (DRA-49).

• The average ultimate friction angle of all rock-pile materials is 38.5o with a standard deviation of 2.4o (Table 3-4, Appendix 3). The ultimate strength was defined as the shear strength after about 10 mm shear displacement.

• Samples from unit I and unit RUB of Goathill North rock pile (φave = 40.8° and 40.7°) have the lowest average peak friction angle (Table 3-1, Appendix 3). Unit I is near the surface and unit RUB is at the base of the GHN rock pile (DRA-6, 46) and have been exposed to more intensive weathering. Samples from Unit I have a lower point load strength (1.1 MPa) and slake durability index of the rock fragments (87.9%) then other units (Table 3-7, Appendix 3).

• All rock-pile materials have mean peak friction angles ranging from 39.7° to 43.8° (Table 3-3, Appendix 3). The Spring Gulch rock-pile material has the lowest mean peak friction angle of 39.7°. Note that the compaction densities for shear testing of the Questa materials were not identical. Table 3-9 (Appendix 3) reports the statistics of the compaction dry densities of rock-pile and analog materials.

• The average cohesion intercept of all rock-pile materials is 24.6 kPa with a standard deviation of 18.5 kPa (Table 3-6, Appendix 3).

• Values of A, for the curve failure envelope, vary from 1.49 to 9.72. The b values range from 0.61 to 0.9 (Appendix 3, Table 3-8). The range of mean values of A and b parameters are 3.9 to 6.1 and 0.69 to 0.78, respectively (Appendix 4, Figs. 4-7 and 4-8).

• Samples of andesite and rhyolite (Amalia Tuff) were collected to determine the geotechnical parameters, including friction angle, of these materials. These samples represent the material of the deposit before mining. The friction angle of the andesite samples has a mean of 41º and the rhyolite samples have a mean of 42.7º (Appendix 3). The friction angles of these materials are similar to those of the rock piles.

• The friction angles of rock-pile and analog materials and the friction angle of GHN rock-pile materials versus the plasticity index are shown in Figures 4-11 and 4-12 (Appendix 4). As expected, with increase in plasticity index, the friction angle reduces for the GHN samples that were compacted to a dry density of 1600 to 1800 kg/m3 for most of the samples (Fig. 4-12). On the other hand, the data are scattered in Figure 4-11, possibly due to the wider range of compaction dry densities used for most of the samples (1600 to 2000 kg/m3). Similar observations apply as the friction angle is plotted versus the percent fines of the Questa material (Figures 4-13 and 4-14 of Appendix 4).

• An effort was made to obtain intact samples from Middle rock pile by a combination of pushing a sample box into the material and digging a trench

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around the sample, such that the sample was disturbed as little as practical. This effort was not very successful as the presence of large rock fragments did not allow proper trimming of the sample for the shear box without at least partially disturbing it. The results of shear tests on these samples are reported separately in Appendix 5.

6. RELIABILITY ANALYSIS The friction angles and cohesion intercepts reported in this DRA were obtained by conducting direct shear tests on air-dried specimens using a 2-inch shear box. These results are valuable when the shear strengths of different geological units or rock pile are compared. Previous results indicate that the Questa rock-pile materials demonstrate moisture softening. The friction angle results obtained for the air-dried samples must be compared to other shear strength testing performed during this project (DRA-43, 44, 45, 49) to select representative values. In particular, the cohesion intercepts values of this DRA are not reliable, as the disturbed laboratory materials can not truly represent the original materials when cohesion measurement is involved. 7. CURRENT CONCLUSION OF THE COMPONENT

• The friction angles of the Questa rock-pile materials are high (φave >40°, Table 3-3). The high friction angles of Questa mine materials are due to (a) angularity of the particles (DRA-40), (b) high strength as determined by point load strength and slake durability of the rock fragments (Table 3-7, Appendix 3, and DRA-46), and (c) presence of low amount of fines material in the rock piles (Appendix 4, Figs. 4-9 and 4-10).

• The friction angles of Questa rock-pile and natural analog materials are similar (Fig. 4-1, Appendix 4). Since the analogs are older than the rock piles, it appears that weathering so far has not caused noticeable reduction of the friction angles at the test locations. Friction angle, point load strength index and slake durability index of the GHN rock-pile samples decreased as the degree of hydrothermal alteration and weathering increased in some samples but not all (Gutierrez, 2006, Gutierrez et al., 2008).

• The friction angles of Questa mine materials reduce as the normal stress increases (Figs. 4-1 and 4-3, Appendix 4). The nonlinear failure envelope can capture the reduction of friction angle with normal stress.

• A normal statistical distribution can reasonably model the scatter of the friction angles of Questa mine material (Figs. 6-1 to 6-4, Appendix 6).

8. REFERENCES CITED

Azam, S., and Wilson, G. W., 2006, Geotechnical characterization of shear strength and hydraulic properties of waste rock samples from Questa Mine, Norman B. Keevil Institute of Mining Engineering, University of British Columbia, Vancouver, British Columbia, Canada.

Charles, J. A. and Watts, K. S., 1980, The influence of confining Pressure on the shear strength of compacted rockfill: Geotechnique, v. 30, no. 4, p. 353 – 367.

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Gutierrez, L.A.F., 2006, The influence of mineralogy, chemistry and physical engineering properties on shear strength parameters of the Goathill North rock pile material, Questa Molybdenum mine, New Mexico: M. S. thesis, New Mexico Institute of Mining and Technology, Socorro, 201 p., http://geoinfo.nmt.edu/staff/mclemore/Molycorppapers.htm, accessed December 06, 2007.

Gutierrez, L.A.F., Viterbo, V.C., McLemore, V.T., and Aimone-Martin, C.T., 2008, Geotechnical and geomechanical characterisation of the Goathill North Rock Pile at the Questa Molybdenum Mine, New Mexico, USA; in Fourie, A., ed., First International Seminar on the Management of Rock Dumps, Stockpiles and Heap Leach Pads: The Australian Centre for Geomechanics, University of Western Australia, p. 19-32. http://geoinfo.nmt.edu/staff/mclemore/Molycorppapers.html accessed August 20, 2008

Linero, S., Palma, C., and Apablaza, R., 2007, Geotechnical characterization of waste material in very high dumps with large scale triaxial testing: Proceedings of International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering, 12-14 September 2007, Perth, Australia, p. 59-75.

McLemore, V.T., Ayakwah, G., Boakye, K., Campbell, A., Donahue, K., Dunbar, N., Gutierrez, L., Heizler, L., Lynn, R., Lueth, V., Osantowski, E., Phillips, E., Shannon, H., Smith, M., Tachie-Menson, S., van Dam, R., Viterbo, V.C., Walsh, P., and Wilson, G.W., 2008, Characterization of Goathill North Rock Pile: revised unpublished report to Molycorp, Tasks: 1.3.3, 1.3.4, 1.4.2, 1.4.3, 1.11.1.3, 1.11.1.4, 1.11.2.3, B1.1.1, B1.3.2.

McLemore, V.T., Boakye, K., and Donahue, K., 2007, Geotechnical Evaluation of Gypsum and Jarosite from Doña Ana County and Hematite from the Questa Mine, New Mexico: unpublished report to Chevron, Task B1.2, 17 p.

Norwest Corporation, 2005, Questa roadside rock piles: 2005 operational geotechnical stability evaluation, Final report submitted to Molycorp Inc.

URS Corporation, 2003, Mine rock pile erosion and stability evaluations, Questa mine: Unpublished Report to Molycorp, Inc. 4 volumes.

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9. TECHINCAL APPENDICES APPENDIX 1. Some published friction angle values of Questa mine material.

FIGURE 1-1. Friction angle vs. %fines (Norwest Corporation, 2005).

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90 100% Fines

Fric

tion

Ang

le

Small Box Direct Shear (2.4'')Large Box Direct Shear (12'')Triaxial (4'')

Range of Fines in Field (5-21%)

Note: GT-6 f ield f ines at 31%

Angle of Repose Φ = 36°

0

2

4

6

8

10

0 4 8 12 16 20 24 28 32 36 40

% Fines (In Field)

Freq

uenc

y

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APPENDIX 2. Direct shear test results for samples GNH-KM0014 and GNH-KMD-0017 using NMT Soiltest machine and ELE machine at Kleinfelder Laboratory in Albuquerque, NM.

R2 = 1.00

R2 = 0.92

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800Norma stress (kPa)

Shea

r stre

ngth

(kPa

)

Friction angle-NMT Residual Friciton angle- NMTKleinfelder Lab. Kleinfelder Lab.

Sample ID. GHN-KMD-0014

FIGURE 2-1. Mohr-Coulomb diagrams for sample GNH-KMD-0014 tested using both ELE machine at Kleinfelder Laboratory in Albuquerque , NM and Soiltest machine at the Mineral Engineering Department, NMIMT.

R2 = 0.96

R2 = 0.97

0

100

200

300

400

500

600

0 100 200 300 400 500 600Normal load (kPa)

Shea

r Str

engt

h (k

Pa)

Friction angle- NMT Residual friction angle - NMTKleinfelder Lab Kleinfelder Lab

Sample ID. GHN-KMD-0017

FIGURE 2-2. Mohr-Coulomb diagrams for sample GNH-KMD-0017 tested using both ELE machine at Kleinfelder Laboratory in Albuquerque , NM and Soiltest machine at the Mineral Engineering Department, NMIMT.

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APPENDIX 3. Friction angle, cohesion intercept and strength of the Questa mine material. TABLE 3-1. Peak friction angle of all geological units (normal stress of 160-750 kPa). (modified from Gutierrez, 2006; Gutierrez et al., 2008; Bokye, 2008). Histograms and statistical analysis are in McLemore et al. (2008, appendix 11).

Location No of Samples Tested

Min (degrees)

Max (degrees)

Range (degrees)

Mean (degrees)

Standard Deviation (degrees)

Coefficient Of

Variation (%)

All Andesite samples

10 38.7 43.7 5.0 41.0 1.8 4.5

All Rhyolite samples

(Amalia Tuff)

9 37.8 45.7 7.9 42.7 2.6 6.1

All Colluvium samples

22 36.9 46.1 9.2 41.4 2.5 6.0

All Debris Flow samples

12 39.2 50.1 10.9 44.3 3.9 8.8

All alteration scars 22 33.4 54.3 20.9 40.7 4.8 11.8 Oxidized, outer zone (GHN rock pile)

Unit C 1 45.7 45.7 na 45.7 na na Unit I 5 38.8 42.1 3.3 40.8 1.3 3.2

Intermediate zone (GHN rock pile) Unit J 5 43.7 45.8 2.1 44.9 0.8 1.8 Unit N 3 41.7 42.8 1.1 42.1 0.6 1.4

Unoxidized, internal zone (GHN rock pile) Unit K 3 39.6 46.9 7.3 42.3 4.0 9.5 Unit O 15 39.9 47.8 7.9 42.8 2.2 5.1 Unit M 1 42.7 42.7 na 42.7 na na Unit R 2 43.4 45.8 2.4 44.6 NA NA Unit S 1 43.3 43.3 NA 43.3 NA NA Unit P 1 43.8 43.8 NA 43.8 NA NA Unit U 4 41.5 46.2 4.7 43.0 2.2 5.1 Unit V 3 42.0 47.8 5.8 44.5 3.0 6.7

Unit RUB 2 39.3 42.1 2.8 40.7 na na Samples from the Unstable portion

of GHN

11 37.8 45.3 7.5 41.7 2.2 5.3

All Questa materials tested

178 33.4 54.3 20.9 42.0 3.3 7.8

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TABLE 3-2. Ultimate friction angle of all geological units (normal stress of 160-750 kPa).

Ultimate Friction Angle(degrees)-High Normal Stress, 160-750 kPa Location No of

Samples Tested

Min (degrees)

Max (degrees)

Range (degrees)

Mean (degrees)


Coefficient Of

Variation (%)

All Andesite samples

10 34.1 42.2 8.1 37.4 2.3 6.1

All Rhyolite samples

(Amalia Tuff)

9 32.1 38.8 6.7 37.1 2.0 5.3


22 35.7 43.7 8.0 38.6 1.9 4.9


12 33.8 42.3 8.5 36.9 2.5 6.8

Oxidized, outer zone (GHN rock pile) Unit C 1 43.2 43.2 NA 43.2 NA NA Unit I 5 34.6 39.9 5.3 37.4 2.0 5.3


Unoxidized, internal zone (GHN rock pile) Unit K 3 37.5 44.3 6.8 39.9 3.8 9.5 Unit O 15 33.8 43.0 9.2 39.1 2.3 5.9 Unit M 1 42.0 42.0 NA 42.0 NA NA Unit R 2 40.7 40.7 0.0 40.7 NA NA Unit S 1 39.3 39.3 NA 39.3 NA NA Unit P 1 35.0 35.0 NA 35.0 NA NA Unit U 4 36.9 42.4 5.5 39.1 2.3 5.9 Unit V 3 35.9 41.6 5.7 38.6 2.9 7.5 Scars 22 26.9 44.8 17.9 36.2 3.4 9.4

Samples from the Unstable

portion of GHN

11 34.2 41.7 7.5 38.2 2.3 6.0

All Questa material tested

178 26.9 44.8 17.9 38.0 2.6 6.8

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TABLE 3-3. Peak friction angle (degrees) of all rock piles (normal stress of 160-750 kPa).

Peak Friction Angle (degrees), High Normal Stress, 160-750 kPa Location No of

Samples Tested

Min (degrees)

Max (degrees)

Range (degrees)

Mean (degrees)


Coefficient Of Variation

(%) All Rock

Pile samples

99 35.3 49.3 14.0 42.2 2.9 6.9

GHN 57 37.8 47.8 10.0 42.7 2.2 5.2 Middle Rock Pile

4 37.8 44.5 6.7 40.7 3.3 8.1

Spring Gulch

11 35.9 49.3 13.4 39.7 3.8 9.6

Sugar Shack South

8 38.9 48.0 9.1 43.8 3.0 6.9

Sugar Shack West

19 35.3 47.9 12.6 41.8 3.4 8.2

TABLE 3-4. Ultimate friction angle (degrees) of all rock piles (normal stress of 160-760 kPa).

Ultimate Friction Angle(degrees),High Normal Stress, 160-750 kPa Location No of

Samples Tested

Min (degrees)

Max (degrees)

Range (degrees)

Mean (degrees)



(%) All Rock

Pile samples

99 32.8 44.4 11.6 38.5 2.4 6.2


4 36.7 38.1 1.4 37.4 0.7 1.9

Spring Gulch

11 32.8 39.9 7.1 36.6 2.3 6.3

Sugar Shack South

8 35.9 41.9 6 39.0 2.2 5.6

Sugar Shack West

19 35.5 44.4 8.9 38.7 2.4 6.2

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TABLE 3-5. Cohesion intercept of Questa mine material (normal stress of 160-750 kPa). Samples with negative cohesion intercept are not included in this table.

Cohesion(kPa) Location No of

Samples Tested

Min (kPa)

Max (kPa)

Range (kPa)

Mean (kPa)

Standard Deviation

(kPa)


(%) All Andesite samples 9 9.6 46.9 37.3 25.4 12.4 48.8 All rhyolite samples

(Amalia Tuff) 9 2.6 47.8 45.2 23.8 14.8 62.2


21 0.4 52.3 51.9 22.6 14.2 62.8


8 0.1 32.4 32.3 15.8 13.4 84.8

Oxidized, outer zone (GHN rock pile) Unit C 1 14.4 14.4 NA 14.4 NA NA Unit I 5 20.1 35.5 15.4 24.5 6.6 26.9


Unoxidized, internal zone (GHN rock pile) Unit K 3 7.0 40.5 33.5 24.5 16.8 68.6 Unit O 14 8.0 41.9 33.9 21.5 11.5 53.5 Unit M 1 15.4 15.4 NA 15.4 NA NA Unit R 1 7.8 7.8 NA 7.8 NA NA Unit S 1 18.7 18.7 NA 18.7 NA NA Unit U 4 0.0 36.9 36.9 17.8 15.5 87.1 Unit V 2 12.5 24.0 11.5 18.3 NA NA Scars 20 9.5 123.4 113.9 38.4 25.8 67.2

Unstable GHN 10 0.4 99.3 98.9 25.4 29.3 115.4

TABLE 3-6. Cohesion intercept of rock piles (normal stress of 160-750 kPa). Samples with negative cohesion intercept are not included in this table.

Cohesion (kPa) Location No of Samples

Tested Min

(kPa) Max (kPa)

Range(kPa)

Mean (kPa)

Standard Deviation

(kPa)


(%) All Rock Pile

samples 85 0.0 116.1 116.1 24.6 18.5 75.2


4 12.9 23.2 10.3 18.4 5.0 27.2

Spring Gulch 8 8.3 42.3 34.0 26.2 11.4 43.5 Sugar Shack

South 6 2.1 36.4 34.3 19.7 16.0 81.2

Sugar Shack West

15 16.2 116.1 99.9 39.8 25.8 64.8

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TABLE 3-7. Summary statistics of the point load and slake durability indices of rock fragments from GHN rock pile.

Location Statistics Point Load Strength

Index (MPa)

Slake Durability Index (%)

Traffic No. of Samples NA 2 Mean NA 97.0 Standard deviation NA Minimum 96.0 Maximum 98.0 Coefficient of Variation (%)

NA

Unit C No. of Samples 1 Mean 97.9 Standard deviation NA Minimum 97.9 Maximum 97.9 Coefficient of Variation (%)

NA

Unit I No. of Samples 2 4 Mean 1.1 87.9 Standard deviation NA 5.5 Minimum 0.6 82.2 Maximum 1.6 95.0 Coefficient of Variation (%) NA 6.3

Unit J No. of Samples 6 7 Mean 5.0 95.8 Standard deviation 1.7 1.9 Minimum 3.3 94.0 Maximum 7.0 98.5 Coefficient of Variation (%) 34.0 2.0

Unit N No. of Samples 4 5 Mean 2.6 96.3 Standard deviation 1.4 1.4 Minimum 1.1 94.0 Maximum 4.5 98.5 Coefficient of Variation (%) 53.8 1.5

Unit K No. of Samples 4 5 Mean 5.3 96.2 Standard deviation 2.0 2.2 Minimum 3.7 93.6 Maximum 8.2 98.4 Coefficient of 37.7 2.3

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Index (MPa)


Variation (%) Unit O No. of Samples 4 18

Mean 3.5 96.5 Standard deviation 1.3 1.4 Minimum 2.4 93.6 Maximum 5.4 98.1 Coefficient of Variation (%) 37.1 1.5

Unit R No. of Samples 2 2 Mean 5.8 96.4 Standard deviation NA NA Minimum 4.3 95.5 Maximum 7.3 97.3 Coefficient of Variation (%) NA NA

Unit S No. of Samples 3 3 Mean 4.0 97.5 Standard deviation 1.0 1.6 Minimum 3.4 95.6 Maximum 5.3 98.4 Coefficient of Variation (%) 25.0 1.6

Unit U No. of Samples 1 5 Mean 6.1 97.7 Standard deviation NA 0.6 Minimum 6.1 97.1 Maximum 6.1 98.5 Coefficient of Variation (%) NA 0.6

Unit UV No. of Samples 2 3 Mean 5.3 96.7 Standard deviation NA 0.8 Minimum 4.5 95.9 Maximum 6.1 97.4 Coefficient of Variation (%) NA 0.8

Unit M No. of Samples 1 1 Mean 3.7 96.6 Standard deviation NA NA Minimum 3.7 96.6 Maximum 3.7 96.6 Coefficient of Variation (%) NA NA

Unit RUB No. of Samples 1 7

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Index (MPa)


Mean 6.5 97.4 Standard deviation NA 1.1 Minimum 6.5 95.2 Maximum 6.5 98.5 Coefficient of Variation (%) NA 1.1

Colluvium No. of Samples 9 Mean 95.7 Standard deviation 1.7 Minimum 93.0 Maximum 98.5 Coefficient of Variation (%)

1.8

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TABLE 3-8. Values of A and b parameters for Questa mine materials. Test id A (kPa**(1-b)) b

QPS-AAF-0001-1 5.10 0.72

QPS-AAF-0001-2 4.74 0.71

QPS-AAF-0001-3 2.66 0.84

QPS-AAF-0008-1 2.38 0.83

QPS-AAF-0009-1 4.81 0.74

QPS-AAF-0020-1 4.95 0.74

QPS-AAF-0022-1 8.84 0.61

QPS-VTM-0001-1 6.60 0.66

MIN-AAF-0001-1 9.68 0.61

MIN-AAF-0004-1 6.66 0.67

MIN-AAF-0010-1 9.7 0.63

MIN-AAF-0012-1 3.72 0.78

MIN-AAF-0015-1 4.7 0.77

MID-AAF-0001-1 5.91 0.69

MID-AAF-0002-1 7.19 0.63

MID-AAF-0002-2 3.5 0.76

MID-VTM-0002-1 7.42 0.66

SPR-AAF-0001-1 3.02 0.82

SPR-AAF-0001-2 4.02 0.77

SPR-VTM-0005-1 2.82 0.80

SPR-VTM-0008-1 4.19 0.75

SPR-VTM-0008-2 1.49 0.90

SPR-VTM-0012-1 4.87 0.73

SPR-VTM-0012-2 2.30 0.82

SPR-VTM-0012-3 8.52 0.61

SPR-VTM-0019-1 3.54 0.75

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Test id A (kPa**(1-b)) b

SPR-VTM-0019-2 2.98 0.78

SSS-AAF-0001-1 4.96 0.73

SSS-AAF-0001-2 3.14 0.81

SSS-AAF-0005-1 5.04 0.72

SSS-AAF-0005-2 4.74 0.74

SSS-AAF-0009-1 4.92 0.73

SSS-AAF-0009-2 3.75 0.79

SSS-VTM-0600-1 4.22 0.74

SSS-VTM-0601-1 3.35 0.80

SSW-AAF-0001-1 5.80 0.69

SSW-AAF-0002-1 2.42 0.85

SSW-AAF-0002-2 3.44 0.78

SSW-AAF-0002-3 2.60 0.84

SSW-AAF-0004-1 6.36 0.71

SSW-AAF-0005-1 3.57 0.78

SSW-AAF-0007-1 6.73 0.67

SSW-VTM-0016-1 6.32 0.70

SSW-VTM-0016-2 8.85 0.62

SSW-VTM-0023-1 9.10 0.62

SSW-VTM-0026-1 6.29 0.70

SSW-VTM-0030-1 9.72 0.63

SSW-VTM-0030-2 6.17 0.70

SSW-VTM-0600-1 2.86 0.78

SSW-VTM-0600-2 4.73 0.74

SSW-VTM-0600-3 2.90 0.83

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TABLE 3-9. Summary statistics of the compaction dry density of Questa mine material used in the direct shear testing.

Compaction Dry Densities Location No of

Samples Tested

Min (kg/m3)

Max (kg/m3)

Range (kg/m3)

Mean (kg/m3)

Standard Deviation (kg/m3)

Coefficient of Variation

(%) All Andesite

samples 10 1510.0 1800.0 290.0 1703.5 113.3 6.6

All rhyolite samples

(Amalia Tuff)

9 1640.0 1820.0 180.0 1755.6 67.3 3.8

Colluvium samples

22 1360.0 1850.0 490.0 1686.4 105.9 6.3

Debris Flow samples

12 1510.0 2160.0 650.0 1831.7 180.0 9.8

Alteration Scar samples

22 1510.0 2130.0 620.0 1804.1 184.3 10.2


4 1880.0 2160.0 280.0 1990.0 119.4 6.0

Spring Gulch 11 1460.0 2170.0 710.0 1743.6 210.6 12.1 Sugar Shack

South 8 1810.0 1960.0 150.0 1890.0 54.5 2.9

Sugar Shack West

19 1410.0 2110.0 700.0 1841.1 189.1 10.3

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APPENDIX 4. Scatter plots of some geotechnical properties of Questa mine material.

30

35

40

45

50

55

60

0 1 2 3 4 5 6 7 8

Sample Location

Peak

Fric

tion

Ang

le (d

egre

es)

GHN (57,2.2)

MID (4,3.3)

SPR (11,3.8)

SSS (8,3.0)

SSW (19,3.4)

Scars (22,4.8)

Debris Flow (12,3.9)

FIGURE 4-1. Peak friction angles of the rock piles and analogs (normal stress of 160-750 kPa).The number of data points and the standard deviation for each rock pile or analog are shown in the parentheses. The average values are shown with circles.

30

35

40

45

50

55

60

0 1 2 3 4 5 6 7 8

Sample Location

Ulti

mat

e Fr

ictio

n A

ngle

(d

egre

es)

GHN (57,2.4)

MID (4,0.7)

SPR (11,2.3)

SSS (8,2.2)

SSW (19,2.4)

Scars (22,3.4)


FIGURE 4-2. Ultimate friction angles of the rock piles and analogs (normal stress of 160-750 kPa). The number of data points and the standard deviation for each rock pile or analog are shown in the parentheses. The average values are shown with circles.

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35

40

45

50

55

60

0 1 2 3 4 5 6 7

Sample Location

Peak

Fric

tion

Ang

le (d

egre

es)

MID (4,6.7)

SPR (11,3.0)

SSS (8,3.0)

SSW (19,4.1)

Scars (9,3.6)

Debris Flow (6,4.6)

FIGURE 4-3. Peak friction angle of the rock piles and analogs (normal stress of 20-120 kPa). The number of data points and standard deviation for each rock pile or analog are shown in the parentheses. The average values are shown with circles.

30

35

40

45

50

55

60

0 1 2 3 4 5 6 7

Sample Location

Ulti

mat

e Fr

ictio

n A

ngle

(d

egre

es)

MID (4,2.7)

SPR (8,3.4)

SSS (8,3.2)

SSW (19,2.3)

Scars (9,5.7)

Debris Flow (6,3.0)

FIGURE 4-4. Ultimate friction angle of the rock piles and analogs (normal stress of 20-120 kPa). The number of data points and standard deviation for each rock pile or analog are shown in the parentheses. The average values are shown with circles.

DRA-42


0

20

40

60

80

100

120

140

0 1 2 3 4 5 6 7 8

Sample Location

Coh

esio

n (k

Pa)

GHN (52,15.7)

MID (4,5.0)

SPR (8,11.4)

SSS (6,16.0)

SSW (15,25.8)

Scars (20,25.8)


FIGURE 4-5. Cohesion intercept of the rock piles and analogs (normal stress of 160-750 kPa). The number of data points and standard deviation for each rock pile or analog are shown in the parentheses. The average values are shown with circles.

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7

Sample Location

Coh

esio

n (k

Pa)

MID (4,20.3)

SPR (11,10.2)

SSS (8,7.3)

SSW (19,13.4)

Scars (9,13.0)


FIGURE 4-6. Cohesion intercept of the rock piles and analogs (normal stress of 20-120 kPa). The number of data points and standard deviation for each rock pile or analog are shown in the parentheses. The average values are shown with circles.

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0.0

2.0

4.0

6.0

8.0

10.0

12.0

0 1 2 3 4 5 6 7

Sample Location

Para

met

er A

MID (4,1.8)

SPR (11,1.8)

SSS (8,0.8)

SSW (19,2.4)

Scars (9,2.1)

Debris Flow (6,2.9)

FIGURE 4-7. The parameter A of the nonlinear failure envelopes of the rock piles and analogs (normal stress of 20-750 kPa). The number of data points and standard deviation for each rock pile or analog is shown in the parentheses. The average values are shown with circles.

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7

Sample Location

Para

met

er b

MID (4,0.1)

SPR (11,0.1)

SSS (8,0.0)

SSW (19,0.1)

Scars (9,0.1)

Debris Flow (6,0.1)

FIGURE 4-8. The parameter b of the nonlinear failure envelopes of the rock piles and analogs (normal stress of 20-750 kPa). The number of data points and standard deviation for each rock pile or analog is shown in the parentheses. The average values are shown with circles.

DRA-42


0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8

Sample Location

% F

ines

(Fie

ld S

ampl

es)

GHN (52,6.4)

MID (4,0.9)

SPR (11,3.0)

SSS (8,2.2)

SSW (19,4.4)

Scars (18,4.4)


FIGURE 4-9. Percent fine of in situ or field samples. The number of data points and standard deviation for each rock pile or analog is shown in the parentheses. The average values are shown with circles.

0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Sample Location

% F

ines

(Lab

orat

ory

Sam

ples

)

GHN (52,5.7)

MID (4,1.8)

SPR (11,8.0)

SSS (8,10.6)

SSW (18,10.8)

Scars (14,12.3)


FIGURE 4-10. Percent fine of –No. 6 sieve samples that were used for laboratory shear tests. The number of data points and standard deviation for each rock pile or analog are shown in the parentheses. The average values are shown with circles.

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30

35

40

45

50

55

60

0 5 10 15 20 25 30

Plasticity Index (%)

Fric

tion

Ang

le (d

egre

es)

GHN MID

SPR SSS

SSW Scars

Debris Flow

FIGURE 4-11. Friction angle vs. plasticity index of rock piles and analogs (normal stress of 160-750 kPa).

Goathill North

30

35

40

45

50

0 5 10 15 20 25

Plasticity Index (%)

Fric

tion

Ang

le (d

egre

es)

FIGURE 4-12. Friction angle vs. plasticity index of GHN rock pile material (normal stress of 160-750 kPa).

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30

35

40

45

50

55

60

0 10 20 30 40 50

%Fine

Fric

tion

Ang

le (d

egre

es)

GHN MID SPR

SSS SSW Scars

Debris Flow

FIGURE 4-13. Friction angle vs. percent fines of rock piles and analogs (normal stress of 160-750 kPa).

Goathill North

30

35

40

45

50

0 10 20 30 40 50

%Fine

Fric

tion

Ang

le (d

egre

es)

FIGURE 4-14. Friction angle vs. percent fines of GHN rock pile material (normal stress of 160-750 kPa).

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APPENDIX 5. 2-inch direct shear test results on intact samples from Middle rock pile. Negative cohesion intercept values are shown as NA in the table.

Sample Id Peak Friction Angle (degree)

Cohesion (kPa) Residual Friction Angle (degree)

Residual cohesion (kPa)

MID-KXB-0001

46.7 NA 44.6 NA

MID-KXB-0003

44.7 NA 43.4 NA

MID-KXB-0004

21.2 189.2 21.9 169.0

APPENDIX 6. Histograms for friction angle of Questa mine material

Friction Angle (degrees)20 25 30 35 40 45 50 55 60

Num

ber

of S

ampl

es

0

5

10

15

20

25

30

35

40GHN

FIGURE 6-1. Peak friction angle of GHN rock pile material (normal stress of 160-750 kPa).

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Ultimate Friction Angle (degrees)32 34 36 38 40 42 44 46

Cou

nt

0

3

6

9

12

15

Ultimate Friction Angle of Goathill North

FIGURE 6-2. Ultimate friction angle of GHN rock pile material (normal stress of 160-750 kPa).

Friction Angle (degrees)20 25 30 35 40 45 50 55 60

Num

ber

of S

ampl

es

0

10

20

30

40

50

60Questa Rock Piles

FIGURE 6-3. Peak friction angle of all rock piles (normal stress of 160-750 kPa).

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Ultimate Friction Angle (degrees)30 35 40 45 50

Cou

nt

0

5

10

15

20

25Ultimate Friction Angle of All Rock Piles

FIGURE 6-4. Ultimate friction angle of all rock piles (normal stress of 160-750 kPa).

Documents

DRA-42 NMIMT LABORATORY DIRECT SHEAR TESTS ON THE ... · shear test apparatus in the Soil Mechanics Laboratory of NMIMT (SOP 50). Most samples were air-dried material, passed No