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CEEn-2017CPST-

Temporary Slope Repair for Highway Expansion

April 20, 2018 1

006

Stephen Isaacson

Amanda McFarland

Mary Ririe

McKay Parkinson

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IntroductionAnalysis of the Problem Soil profiles were constructed by interpolation of boring logs from holes 7310 and 7370.

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Figure 1. Soil profile from boring logs, station 489+50 Figure 2. Boring Hole Locations

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IntroductionAnalysis of the Problem Soil properties

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Soil Type Unit Weight Cohesion Friction

AngleClay (Sandy, tan) (CL) 135 959 29Sand (tan) 125 30Clay (CL) 120 2867Sand (tan) 125 36Clay (sandy, tan, and gray)(CH) 135 1922Shale (gray) 150

Table 1: Soil Properties

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Design, Analysis & ResultsSlope failure was found to be on the upper clay layer after several iterations and study of all stations. Lowest factor of safety was 0.874.

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Figure 2. Slope Failure Analysis

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Design, Analysis & ResultsAnalysis of possible solutions

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Ratings Table:1 = lowest (worst), 4 = highest (best) Drill Shafts Driven Piles Shotcrete Steel Mesh

Cost (weighting = 0.85) 1 2 3 4

Ease of Construction (Weighting = 0.3 1 4 3 2

Capacity Design Load (Weighting = 0.5) 4 2 3 1

Meets Design Life (Weighting = (0.25) 1 2 3 4

Aesthetic/Environment (Weighting = 0.15) 1 3 2 4

Sum of (Rating Times Weighting) 3.55 4.85 6 6.1

Table 2: Cost Comparison Analysis

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Design, Analysis & ResultsSolution DesignNail parameters from FHWA:

• 20 ft. in length• #6 bar• 15° from horizontal• Pullout resistance: 1000 k/fto Ultimate: 2000 k/fto FS: 2

• Spacing:o Vertical: 5 ft.o Horizontal: 4 ft.

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Figure 3. Reinforced Slope Analysis

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Design, Analysis & ResultsSolution Design Facing and Grout from FHWA:

• Plate size: 8”x 8” x 3/4”• 6” grout diameter• 4” initial facing• 6” final facing

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Figure 4. Slope Stability Design Detail

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Conclusions & Recommendations

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Conclusions & Recommendations

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Conclusions & Recommendations Soil nails with shotcrete facing Total cost estimate: $167,000Duration: 4 weeks

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Cost Estimation6x6x.105 Wire Mesh: $1,675Grade 60 Rebar (#8): $20,0008x8x3/4 Steel Plates: $10,710

Shotcrete: $3,031Material Subtotal: $35,416

Installation: $121,584Contingency: $10,000Project Total: $167,000

Table 3: Final Cost Estimate