1. Riprap Installation Construction Inspection for Field Office Activities Will use Riprap Gradation and Riprap Subgrade Problems from Class Problem Section USDA is an equal opportunity provider and employer.

2. Objectives  Understand importance of rock quality  Define D 50, D max and D min  Understand importance of subgrade  Visualize good placement vs. bad

3. Specifications  Construction Specification 61 - Rock Riprap  Construction Specification 62 - Grouted Rock Riprap  Material Specification 523 - Rock For Riprap

4. Riprap definition Stone materials, generally less than two tons in weight, specially selected and graded, and when properly placed prevents erosion caused by minor wave action, or erosive currents and thereby preserves the shape of a surface, slope, or the underlying structure.

5. Materials Rock

6. Rock Approval  Specifications 61 and 62 require the contractor to designate the material source prior to delivery to the site  When possible the inspector should visit the source to avoid rejecting on site  Geologist can help determine rock quality (if requested)

7. Why is good rock quality important?  Rock size always shrinks with time  The design is based on certain rock weights/sizes

8.  Rock size/weight decreases (does not grow)  From loading  Dumping  Placing  Weathering Rock Inspection

9. Rock, Field Checking  At quarry  Rock quality  Rock size  Rock name for acceptable pile  Measure out a sample size (2 ton?) if quarry will allow it  Quarry equipment may be needed to move rocks  Visual reference for operator loading at quarry

10. Rock Inspection at Quarry  Rock quality  Drop rock on another  Foot protection  Hit with hammer  Eye protection  Look for seams

11. Rock Inspection at Quarry  Rock size/shape  Angular not rounded  Gradation/Weight calculations

12. Gradation Check rock size(s)

13. GRADATION Rock that is too large will cause quantity overruns. Rock that is too small may become displaced. Rock that is poorly graded may not protect the subgrade as intended. flow Planned limits Exposed subgrade

14. What is D 50 ?  D = rock diameter (inches)  50 = 50% of rock is lighter  By weight not volume  Example gradation  D 100 = 24” (usually between 2D 50 to 2.5D 50 )  D 50 =10”  D min =5” (about 0.5D 50 )

15. Poorly graded

17. Well graded

18. Will half the rocks in a properly graded truck load be D 50 size? No, rock gradation is by weight not by the number of rocks.

19. Sample gradation  The following specification will apply to the slope rock:  5 % (by weight) shall be equal to or less than 150 lbs.  95 % shall be between 300 and 3,000 lbs. and well- graded.  maximum weight of 4,000 lbs

20. Measure rock sizes

21. Field estimate of rock weights (assuming rock is cube shape)  Measure 3 sides of a typical rock  Multiply the sides  Multiply answer by 165

22. Multiply volume times weight  3 ft x 3 ft x 2 ft rock = 18*165 = approximately 3000 lbs

23. Weight adjustment if rock is not cubical  if rocks are more rounded than square reduce this by as much as 75%  OR

24. MNTC (double perimeter) method assumes rock is spherical shape  W (lb) = (P 1 +P 2 ) 3 /3  P 1 = perimeter of major axis (ft)  P 2 = perimeter of minor axis (ft)  AND  d (in) = 2.41W 1/3  d = rock diameter (in)

25. Examples  P 1 = 2.3 ft  P 2 = 3.3 ft  W = (2.3+3.3) 3 /3 = 58 lb  AND  d = 2.41(58) 1/3 = 9.3 in

26. Graph located at back of section Use graph to answer Riprap Size problem

27. From Friendly Farmer GSS specifications, D 50 = ______lb D 90 = _____lb, Assume this is Dmax D 10 = _____lb, Assume this is Dmin Riprap Gradation Problem: Use Friendly Farmer GSS specs and graph 80 200 10

28. From Friendly Farmer GSS specifications, D 50 = 80 lbs Dmax = 200 lbs Dmin = 10 lbs From graph 1. Probable diameter of Dmax is ____ 2. Sum of perimeters is ____ 3. Probable diameter of Dmin is ____ 4. Sum of perimeters is _____ Riprap Size Problem: Use Friendly Farmer GSS specs and graph 14” 8.4’ 5” 3.1’

29. Weigh each riprap sample using: 1. The sum of perimeter method 2. The three dimension method. Class Exercise:

30. Sample #1–Actual weight is 31.5 lbs Class Exercise Results : Sample #2–Actual weight is 44.2 lbs

31. On-Site Installation Process  Sediment & Erosion Controls  Staking  Sub-grade Preparation  Filter Bedding, or Geotextile  Placement

32. Erosion and Sediment Control  Planned controls in place  Functioning as planned  Do not work in standing water  Never work in flowing water (unless the locations are specifically identified on the permit)

33. Concrete barrier diversion Diversion channel

34. Inspect sediment controls

35. Staking/Layout H D Set hubs away from the immediate work area. Record station number, H, and D on lathe near hub. Survey rod

36. Subgrade  Toe excavation alignment  Toe excavation elevation  Check for proper slope on bank, cut and fill  Watch type of soil excavated  Removal of water

38. POOR SUBGRADE PREPARATION

39. Toe rock excavation Note alignment Subgrade

40. Subgrade  POINT OF NO RETURN  Do it right the first time  Plan ahead  Check elevations and dimensions  Class Problem Time!!!

41. Bedding vs. Filter  Bedding is a structural base  Filter is for preventing or delaying movement of fines

42. Bedding vs. Filter  Bedding and filter may be required together  Can be soil or geo-textile or both

43. Bedding vs. Filter  Bedding and filter installed smooth  Must be stable  Compaction only if called for by Designer

44. Geotextile placement Good or Bad placement?

45. Bedding soil  Check source of material  Inspect gradation and quality  Prepared bedding must be inspected before rock is placed  To ensure proper thickness

46. Sandy-gravel bedding

47. Onsite gravel soil bedding

48. Rock, Field Checking  Rock delivery tickets show that rock is from previously agreed-upon source  Rock, on truck, and as dumped looks like rock from source Visual Inspection Measurements  Amount of fines are acceptable

49. Placement

50. Placement

51. Placement  Assure rocks are touching (no voids, no soil showing)  A thumb attachment is very useful for this work

52. SECTION VIEW of PROPER vs. IMPROPER PLACEMENT PROPER PLACEMENT Large rocks evenly distributed, small rocks fill voids between large rocks IMPROPER PLACEMENT Large rocks distributed unevenly with pockets of small rock in between

53. PLAN VIEW OF PROPER PLACEMENT Large rocks touch small rocks filling voids between. Should not see much ground when looking down.

54. AVOID DOUBLE DECKING Double decking usually occurs when hand placed. Small rocks are placed on top of the rock fill to bring it up to the specified grade. Looks good, works bad.

55. Poorly placed

56. Poor placement

57. Better placement

59. Close-up good placement

60. Placement  Watch thickness  Watch Slopes

61. Measure average thickness Measure here

62. Checking Slope

63. Questions?