REP10582

• Permit No: M1977378
• IBM Index Class Name: Report
• Doc Date: 4/19/1991
• Doc Name: GEOTECHNICAL SERVICES
• Media Type: D
• Archive: No

' Tailings Pond N • •
Sunnyside Mine
Silverton, Colorado
Project No. 3120K114
' parameters obtained from laboratory and field testing as
outlined above. The stability analyses were conducted on the
' slope cross-sections 3 and 5 provided by San Juan Mining
Venture. Sections 3 and 5 were chosen since they comprise the
steepest slopes of the Tailings Pond. Section 3 is located
near the corner of the pond and is one of the highest sections
' of the tailings pond.
i ' The internal geometry of each cross-section was formulated
based on the subsurface conditions encountered in the test
borings along each cross-section. Groundwater levels, as
' encountered in the test borings and piezometers, were used to
simulate the phreatic surface within the pond materials.
t PC STABL 4, developed by Purdue University, using a modified
' Bishop technique, was utilized for the stability analyses of
the existing and proposed slopes. The computer model assumes
that the tailings embankment behaves as a rigid body, assumes a
' constant distribution of stress and a uniform distribution of
strength along the postulated slip surface. The forces acting
' to resist movement are compared to the forces tending to cause
movement. This ratio, the factor of safety, is an indication
of the stability of the postulated slip surface. The computer
program locates the slip surface with the lowest factor of
' safety which is used as an indicator of the safety within the
embankment model. This factor of safety of the cross-section
analyzed for the applicable loading condition.
Each cross-section was analyzed under static and pseudo-static
' (seismic) conditions. For pseudo-static analyses, a horizontal
acceleration of 0.0878 was used to simulate potential
' earthquake loading. In addition, each cross-section was
analyzed using the existing configuration of the slope, and the

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