Site Remediation And Mitigation Plan


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Part II of our senior design project. My design.

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Site Remediation And Mitigation Plan

  1. 1. <ul><li>Rockfall Hazard Rating for Road Cuts between Rolla and Vienna II. Site Remediation and Mitigation Plan for Site E Four Miles North of Rolla, MO on Highway 63 </li></ul><ul><li>Daniel Stout </li></ul><ul><li>Evan Stevens </li></ul><ul><li>Brian Mullen </li></ul>
  2. 2. Part 1: Rate all Rock Cuts on Highway 63 between Rolla and Vienna, MO <ul><li>How? </li></ul><ul><ul><li>Missouri Rock Fall Hazard Rating System </li></ul></ul><ul><ul><ul><li>Maerz et. al., 2005 </li></ul></ul></ul><ul><ul><ul><li>“ Missouri System” </li></ul></ul></ul><ul><ul><li>Oregon Rock Hazard Rating System </li></ul></ul><ul><ul><ul><li>Pierson & Van Vickle, 1993 </li></ul></ul></ul><ul><ul><ul><li>“ Oregon System” </li></ul></ul></ul><ul><li>Both use similar factors to rate rock fall hazards </li></ul><ul><li>Oregon system tailored for mountainous terrain </li></ul><ul><li>Missouri system designed for more moderate terrain; includes karst variables </li></ul>
  3. 3. In the beginning… <ul><li>36 individual sites </li></ul><ul><li>L & R sides rated separately </li></ul><ul><li>Digital video analysis and site visits used to gather data </li></ul>
  4. 4. “ Missouri System” <ul><li>RISK </li></ul><ul><ul><li>Slope height </li></ul></ul><ul><ul><li>Slope angle </li></ul></ul><ul><ul><li>Rock face instability </li></ul></ul><ul><ul><li>Weathering & Erosion </li></ul></ul><ul><ul><li>Rock strength </li></ul></ul><ul><ul><li>Face irregularity </li></ul></ul><ul><ul><li>Face looseness </li></ul></ul><ul><ul><li>Block size </li></ul></ul><ul><ul><li>Water </li></ul></ul><ul><ul><li>Karst </li></ul></ul><ul><li>CONSEQUENCE </li></ul><ul><ul><li>Ditch width </li></ul></ul><ul><ul><li>Ditch volume </li></ul></ul><ul><ul><li>Rockfall quantity </li></ul></ul><ul><ul><li>Slope angle </li></ul></ul><ul><ul><li>Shoulder width </li></ul></ul><ul><ul><li>Number of lanes </li></ul></ul><ul><ul><li>Daily traffic </li></ul></ul><ul><ul><li>Average vehicle risk </li></ul></ul><ul><ul><ul><li>(Cars/day * length)/(Speed limit * cut length) </li></ul></ul></ul><ul><ul><li>Decision Sight Distance </li></ul></ul><ul><ul><li>Block size </li></ul></ul>
  5. 5. “Missouri System” <ul><li>Rate factors, then sum risk 1-100 </li></ul><ul><li>Rate factors, then sum consequence 1-100 </li></ul>
  6. 6. “Oregon System” <ul><li>Factors </li></ul><ul><ul><li>Slope height </li></ul></ul><ul><ul><li>Ditch effectiveness </li></ul></ul><ul><ul><li>AVR </li></ul></ul><ul><ul><li>DSD </li></ul></ul><ul><ul><li>Structural condition & erosion </li></ul></ul><ul><ul><li>Block size/quantity </li></ul></ul><ul><ul><li>Climate/Water </li></ul></ul><ul><ul><li>Rock fall history </li></ul></ul><ul><li>Each factor rated </li></ul><ul><ul><li>3 (good) </li></ul></ul><ul><ul><li>9 (fair) </li></ul></ul><ul><ul><li>27 (poor) </li></ul></ul><ul><ul><li>81 (bad) </li></ul></ul><ul><li>Summation of all values gives score; maximum 810 </li></ul><ul><li>>500 needs “immediate action” </li></ul><ul><li>300-500 “of concern” </li></ul>
  7. 7. “Missouri system” results Site E Site D Site K
  8. 8. “Oregon System” results <ul><li>Sites E, D, and K elevated in this model too </li></ul><ul><li>E = 222/810 </li></ul><ul><li>Other sites (red arrows) perhaps “inflated” by AVR </li></ul>
  9. 9. Part I Results <ul><li>Site E clearly highest rated site by both methods </li></ul><ul><li>A few other sites may need attention </li></ul>
  10. 10. “Site E” <ul><li>Four miles north of Rolla, fifth cut on right </li></ul><ul><li>Just past Capital Quarry </li></ul>
  11. 11. The Paleosinkhole <ul><li>Cut is approx. 50 years old </li></ul><ul><li>Stands at 76 degrees </li></ul><ul><li>Heterogeneous jumbled up mass </li></ul><ul><li>Matrix like a calcrete or caliche </li></ul><ul><li>Dolomite boulders and broken strata </li></ul>
  12. 12. A short slideshow <ul><li>Left and right contacts </li></ul><ul><li>Jumbled mass of dolomite in a calcrete mix </li></ul><ul><li>Overhanging slab at top </li></ul><ul><li>Ravel Pile </li></ul>
  13. 13. <ul><li>Right contact </li></ul><ul><li>Dry </li></ul><ul><li>Slumping/slumped </li></ul><ul><li>Ditch along top </li></ul>
  14. 14. <ul><li>Left contact </li></ul><ul><li>Wet </li></ul><ul><li>Highly eroded; water off top and along joints </li></ul>
  15. 17. Approx. 2’
  16. 18. Current Mitigation Practice
  17. 19. Possible Remediation or Mitigation <ul><li>Excavation </li></ul><ul><li>Berms </li></ul><ul><li>Rocksheds </li></ul><ul><li>Ditches </li></ul><ul><li>Rock traps and fences </li></ul><ul><li>Retaining walls and Gabions </li></ul><ul><li>Mesh draping </li></ul><ul><li>Rock netting </li></ul><ul><li>Shotcrete </li></ul><ul><li>Rockbolting </li></ul><ul><li>Soil nailing </li></ul>Spang, 1987
  18. 20. Chosen Methods to Investigate <ul><li>Gabion Walls </li></ul><ul><li>Mesh Draping (w/ and w/o rock fencing) </li></ul><ul><li>Excavation </li></ul>Gabion wall on I-44 Mesh draping on a similar slope (Goodman, 1989)
  19. 21. Gabion Walls <ul><li>“ Natural looking” stacked baskets of rock </li></ul><ul><li>Low maintenance </li></ul><ul><li>Restraining mass </li></ul><ul><li>Local experience </li></ul><ul><li>Assumptions </li></ul><ul><ul><li>Phi = 35 degrees </li></ul></ul><ul><ul><li>C = 300 psf </li></ul></ul><ul><ul><li>Values consistent with a strong soil </li></ul></ul><ul><ul><li>Unit weight = 160 pcf </li></ul></ul><ul><li>Assignments </li></ul><ul><ul><li>Wall batter = 6 degrees </li></ul></ul><ul><ul><li>Porosity of 50 percent </li></ul></ul><ul><ul><li>2.7 mm PVC coated wire </li></ul></ul><ul><ul><li>Top slope of 3 degrees </li></ul></ul><ul><ul><li>3 ft top surface height (depth of lowest layer of gabions) aids FOS </li></ul></ul>
  20. 22. Design 1: Half-slope Gabion Wall <ul><li>24 ft gabion wall </li></ul><ul><li>Benched back 12 ft. </li></ul><ul><li>Bench covered w/ rip-rap </li></ul><ul><li>$70-$80,000 depending upon options </li></ul><ul><li>Overall FOS 1.91 </li></ul>
  21. 23. Design 2: Full-slope Gabion Wall <ul><li>48 ft gabion wall </li></ul><ul><li>Four tiers </li></ul><ul><li>$180-$220,000 </li></ul><ul><li>Overall FOS 1.69 </li></ul>
  22. 24. Design 3: Staggered half-slope gabion walls <ul><li>Two 24’ gabion walls staggered with a 12’ (9’) bench </li></ul><ul><li>Bench covered w/ rip-rap </li></ul><ul><li>$105-$135,000 </li></ul><ul><li>Overall FOS 1.97 </li></ul>
  23. 25. Design Cost Comparison
  24. 26. Design Comparison 2
  25. 27. Maintenance/ Recommendation <ul><li>Design 1 </li></ul><ul><li>Why? </li></ul><ul><ul><li>Lowest cost </li></ul></ul><ul><ul><li>Best FOS </li></ul></ul><ul><ul><li>No FOS < 1.50 </li></ul></ul><ul><ul><li>Others are overkill </li></ul></ul><ul><li>Not Designs 2 & 3 </li></ul><ul><li>Why? </li></ul><ul><ul><li>High cost </li></ul></ul><ul><ul><li>Poor overturning FOS </li></ul></ul><ul><li>Low maintenance </li></ul><ul><ul><li>Clear out vegetation, or allow it cover if wanted </li></ul></ul><ul><ul><li>Check regularly for wire breaks </li></ul></ul><ul><ul><li>Clean benches (if any) periodically </li></ul></ul>
  26. 28. Mesh Draping - General <ul><li>A flexible facing such as wire rope nets or conventional wire meshes are draped over the slope for passive rock fall protection. </li></ul><ul><li>The draping does not stop rock falls, but rather controls the velocity of falling rocks by limiting the horizontal component. </li></ul><ul><li>Anchored from above and simply hangs over slope </li></ul>(Hoek, 2006)
  27. 29. Mesh Draping - Procedure <ul><li>Clean and scale slope </li></ul><ul><li>Choose net size </li></ul><ul><li>Anchor support cables </li></ul><ul><ul><li>Could be problematic given the paleosinkhole material nature </li></ul></ul><ul><ul><li>Need 20 kips support </li></ul></ul>Muhunthan et. al. (2005)
  28. 30. Optional Rock Fencing Energy absorbing rock fence that can be used alone or in addition to other methods (Hoek, 2006) <ul><li>Design may or may not include rock fencing as a design element </li></ul>
  29. 31. Design 1: 40’ drape w/ rock fence <ul><li>40’ mesh draping over paleosink </li></ul><ul><li>4” x 4” mesh </li></ul><ul><li>120’ rock fence across center </li></ul>
  30. 32. Design 2: Full-slope draping <ul><li>55’ draping covers full slope </li></ul><ul><li>4” x 4” mesh </li></ul>
  31. 33. Draping Comparison
  32. 34. Draping Comparison 2 <ul><li>Draping with fence provides perhaps the best protection of all designs, but: </li></ul><ul><ul><li>Removal of accumulated debris is problematic </li></ul></ul><ul><ul><li>Periodic fence replacement costly (~$21,000) </li></ul></ul><ul><li>Full-slope draping alleviates above concerns </li></ul>
  33. 35. Draping Recommendation <ul><li>Full-slope draping </li></ul><ul><ul><li>Keeps all but the very smallest and largest rock falls in the ditch </li></ul></ul><ul><ul><li>Requires little to no maintenance </li></ul></ul><ul><ul><li>Relatively cheap compared to massive excavation or gabion walls. </li></ul></ul><ul><li>Problems </li></ul><ul><ul><li>Paleosink material problematic for placing anchors </li></ul></ul><ul><ul><li>No protection against rotational failure </li></ul></ul>
  34. 36. Excavation <ul><li>Removal of two linear yards into paleosink along entire face </li></ul><ul><li>1080 c.y. @ $28/c.y. </li></ul><ul><li>~$30,000 </li></ul><ul><li>Note: the $28/c.y. price is a high bid; could be done cheaper </li></ul><ul><li>What does this do? </li></ul><ul><ul><li>Temporary </li></ul></ul><ul><ul><ul><li>Removes weathered face </li></ul></ul></ul><ul><ul><ul><li>Decreases looseness </li></ul></ul></ul><ul><ul><ul><li>Decreases face instability </li></ul></ul></ul><ul><ul><li>Permanent </li></ul></ul><ul><ul><ul><li>Increases ditch width and volume </li></ul></ul></ul><ul><ul><ul><li>Slight decrease in slope angle to 70 degrees </li></ul></ul></ul>
  35. 37. Excavation effect (49,67) (58,79)
  36. 38. Comparison of all Designs
  37. 39. Recommended Design <ul><li>Full-slope draping at $53, 414 </li></ul><ul><li>Very good results w/ usage so far, for more info see: </li></ul><ul><li>Muhunthan et. al. (2005) Analysis and Design of Wire Mesh / Cable Net Slope Protection, Washington State Transportation Center, April 2005. </li></ul>
  38. 40. Afterthoughts <ul><li>We’ve noticed numerous paleosinkholes over Missouri in the middle of similar rock cuts that now sit at ~30 degrees and are heavily vegetated. If excavation could be done cheap, cut it back to <30 degrees and vegetate it </li></ul><ul><li>As we went through this exercise—even at the very end—we continued to discover alternatives </li></ul><ul><ul><li>There are numerous simple retaining wall structures that might work just fine if all we want to do is control rock, ravel, and roll. </li></ul></ul><ul><ul><li>Sheet piles, bin walls, etc. </li></ul></ul>The next road cut down from Site E has a degraded paleosinkhole…
  39. 41. In reality… <ul><li>The slope will probably sit and ravel… </li></ul>
  40. 42. Questions?