PERMFILE43801

• Permit No: C1996083
• IBM Index Class Name: Permit File
• Doc Date: 3/24/2004
• Doc Name: Section 11
• From: Yeh & Associates, Inc
• Section_Exhibit Name: Volume VII Geotechnical Studies
• Media Type: D
• Archive: No

4.0 General Requirements and Notes
1.0 MSE Berm Materials
1.1 Backfill soils
1.1.1 Backfill for reinforced zones shall meet the following gradation:
Sieve Percent Passing 6y We'ight
8" 100
No. 4 30-100
No. 50 10-65
No. 200 0-50
1.1.2 The part of the backfill soil passing the No. 200 sieve shall have a
liquid limit less than 35 and a plasticity Index less than 20 when tested
in accordonce with AASHTO T89 and T90, respectively.
1.2 Geotextile reinforcement have on ultimate wide width tensile strength
greater than 1800 pounds per foot (Tu„>1800 Ibs/ft).
2.0 MSE Berm Construction Sequence
2.1 Prior to construction the reinforced backfill area shall be cleared of
unsuitable material and grubbed.
2.2 Backfill shall be placed In lifts no thicker than 8" compacted for
heavy compaction equipment and in lifts no thicker than 4" for
hand-operated compaction equipment. Backfill shall be placed in
horizontal layers and compacted against horizontal surfaces.
2.3 Backfill shall be compacted to at least 95% of maximum dry density
as determined by the standard Proctor (AASHTO T-99) of optimum
moisture content f2%.
2.4 Place geotextile reinforcements as shown on the drawings. All geotextile
reinforcement layers are 100% coverage.
25 Track vehicles shall not be operated directly on the geotextile. A
minimum of 6" of backfill is required to operate track vehicles over the
geotextile and turning shall be minimized to avoid displacing the geotextile.
2.6 Rubber tired vehicles may pass over the geosynthetic but should ovoid
sudden braking and sharp turning.
27 Overlapping geotextiles shall be placed with at least 3" of
backfill between layers to prevent fabric to fabric contact.
2.8 Permanent surface water diversion is the responsibility of the
owner. The backfill and foundation Bolls should not be allowed to
saturate.
3.0 MSE Berm Design Parameters
3.1 The MSE berm has been designed in general accordonce with
procedures contained in the "Mechanically Stabilized Earth Walls and
Reinforced Soil Slopes Design and Construction Guidelines" and the
"Full Scale Geotextile Rock Barrier Wall Testing, Analysis, and
Prediction" prepared for CDOT by Parsons De Leuw, Inc. in
December 1992.
3.2 The following values hove been assumed for soil/rock design
parameters:
Effective Friction
Angle (m)
Effective Cohesion
Unit Weight
Reinforced Soil 28' 100 psf 110 pcf
Foundation Soll pg• 100 psf 110 pcf
An experienced geotechnical engineer should verify the above design
parameters during construction.
3.3 Groundwater was not considered in this design. No groundwater
was also assumed during service Ilfe of the wall.
3.4 Factors of safety
3.4.1 Global - FS>1.3
3.4.2 External
Bearing capacity - FS>25
Overturning - Eccentric ity<L/6
Sliding - FS>L5
3.4.3 Internal
Pullout - FS>1.5
Tensile Overstress - FS>1.5
3.5 Service life of the wall is 3 months.
3.6 Deformation of the wall greater than 12" may occur.
3.7 The design rock diameter is 5 feet with 5-foot to 40-foot
drop heights.
3.8 The berm is designed for an impact energy of approximately
one million ft-Ibs with impacts in the lower 60% of the berm
height.
4.7 This rockfoll catchment has been designed os o temporary
structure for protection of the mine facilities during subsidence of
the mine as described in the "Rockfall Hazard Evaluation Bowie
#2 Mine" by Yeh and Associates dated November 20, 2003. This
design is valid only for this site.
4.2 This design is valid only for dry surface and subsurface
conditions. Wetting at the base of the wall will reduce the factors
of safety. If surface or groundwater is encountered during
excavation or installation, or wetting occurred during the service
life of the wall, Yeh and Associates should be notified
immediately.
4.3 Yeh and Associates is not responsible for maintaining slope
stability during excavation and MSE wall construction.
4.4 Yeh and Associates is not responsible for quality control,
quality assurance, changed conditions or problems resulting from
improper construction techniques.
4.5 Yeh and Associates is not responsible for construction site
safety.
4.6 The Contractor is responsible for reinforced soil slope layout
and construction surveying. The rockfoll catchment shall be field
located within the areas designated in these plans. The
Contractor is responsible for utility locations and for any utility
relocation.
4.7 Any revisions to the design parameters or structure geometry
shall require design modifications prior to proceeding with
construction.
4.8 This design is based on information provided to us by others.
The Contractor is responsible for field verification of the design
assumptions and for providing materials which are consistent with
this design.
4.9 The berm and ditch area above fhe wall will require periodic
maintenance. The owner Is responsible for maintaining the design
configuration of the ditch.
4.10 Yeh and Associates hove designed the berm based on site
grading and drainage plans provided by others. Changes to the
site grading plan will require redesign of the berm. the owner is
responsible for construction control.
4.77 After the subsidence event, the berm shall be inspected,
repaired, and made permanent if neccessory.
4.12 Rockfall hazards exist on the site and the Impact energies
of very large rocks may exceed the design capacity of most
systems. Complete protection from rockfoll haze rds is not
achievable.
Sheet Revision Prove=t Noiaode
Temporary Rock note Revision/Issue Checked By: 'L4-009 ,~ Yeh and Associates, IIIC~
Catchment Design General Notes Consulting Geotechnical Engineers
Bowie Mine #Z 420 Seventh Street, Suite 100 Phone: [phone]
1855 Old Highway 133 Pro;ear: o~ow~ eY: Glenwood Springs, CO 81601 Fax: [phone]
Paonia, CO Rock Catchment Desigo KdS P,9~,e No.: 5700 E. Evans Ave. Phone: [phone]
Dole: cne~kee eY: 2 of 4
February 12, 2004 RAP Denver, CO 80222 Fax: [phone]