|
April 21, 2020 Page 4
<br />Table 1. Summary Numerical Model Input Parameters
<br />Material
<br />Average Depth of
<br />Confinement (ft)
<br />Deformation
<br />Modulus (psf)
<br />Cohesion
<br />(psf)
<br />Friction Angle
<br />(0)
<br />New Spoils -A
<br />10
<br />1,000,000
<br />475
<br />34.0
<br />New Spoils-B
<br />30
<br />1,732,051
<br />475
<br />32.5
<br />New Spoils-C
<br />50
<br />2,236,068
<br />475
<br />31.3
<br />New Spoils-D
<br />70
<br />2,645,751
<br />475
<br />30.9
<br />New Spoils-E
<br />90
<br />3,000,000
<br />475
<br />29.4
<br />New Spoils-F
<br />110
<br />3,316,625
<br />475
<br />28.6
<br />New Spoils-G
<br />130
<br />3,605,551
<br />475
<br />27.7
<br />New Spoils-H
<br />150
<br />3,872,983
<br />475
<br />26.9
<br />New Spoils -I
<br />170
<br />4,123,106
<br />475
<br />26.1
<br />New Spoils-J
<br />190
<br />4,358,899
<br />475
<br />25.3
<br />New Spoils-K
<br />210
<br />4,582,576
<br />475
<br />24.6
<br />New Spoils-L
<br />230
<br />4,795,832
<br />475
<br />23.8
<br />New Spoils-M
<br />250
<br />5,000,000
<br />475
<br />23.1
<br />New Spoils-N
<br />270
<br />5,196,152
<br />475
<br />22.4
<br />Old Spoils -Fine
<br />25
<br />1,000,000
<br />475
<br />34.0
<br />Old Spoils -Medium
<br />75
<br />2,645,751
<br />500
<br />37.5
<br />Old Spoils -Coarse
<br />100
<br />3„000,000
<br />525
<br />40.0
<br />Rock mass
<br />-
<br />220,000,000
<br />201,000
<br />26.5
<br />Global Stability Analysis Using Numerical Modeling
<br />Given the sloping terrain and complex geometrical interaction between the old spoils, new
<br />spoils and underlying rock mass, AAI selected the use of a three-dimensional numerical modeling
<br />tool F1ac3D (version 5.01.152).5 A three-dimensional model of the proposed spoil pile was created
<br />in F1ac3D, which included the native rock mass, old spoils in I -Seam cuts, and new spoils
<br />differentiated into 20-ft-tall benches. At the time of study, the spoil benches were proposed to be
<br />constructed in 20-ft lifts, which is the reason 20-ft bench heights were assumed in AAI's numerical
<br />models. Even though Trapper currently proposes to construct the spoil pile in 25-ft bench
<br />increments, the overall conclusions of the study remain valid. In order to avoid model edge effects,
<br />the edges of the model were offset horizontally by at least 500 ft from the perimeter of the new
<br />spoil pile. The post -construction model geometry is presented in Figure 2, where different colors
<br />represent old and new spoils of variable strengths. The numerical model was run in two distinct
<br />stages. The model was simulated using current topography (including the I -Seam cuts and spoils)
<br />5 F1ac3D 5.01 Manual (2012), available at hlW://www.itascacg.com.
<br />Agapito Associates, Inc.
<br />
|