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CEE 434 GEOTECHNICAL DESIGN FALL 2008

CEE 434 GEOTECHNICAL DESIGN FALL 2008. GRADING AND SITE IMPROVEMENT METHODS PART I. OUTLINE. Introduction Case Studies Factors Affecting Compaction Fundamentals of Shallow Compaction Examples. I. Introduction. When considering a site for construction,

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CEE 434 GEOTECHNICAL DESIGN FALL 2008

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  1. CEE 434GEOTECHNICAL DESIGNFALL 2008 GRADING AND SITE IMPROVEMENT METHODS PART I

  2. OUTLINE • Introduction • Case Studies • Factors Affecting Compaction • Fundamentals of Shallow Compaction • Examples

  3. I. Introduction When considering a site for construction, a Geotechnical Engineer encounters: • Abandon • Adapt • Alter

  4. “... almost no significant engineered construction occurs without the movement of soil from one place to another!” -Ed Monahan, 1994 From: Coduto, 1999

  5. Research Park Tech Center IV Construction Camera #1

  6. UNCONTROLLED AND CONTROLLED FILLS CONT’D… 2V TO 1H Research Park Tech Center IV Construction Camera #1 Source: Greenfield, 1992

  7. II. CASE STUDIES

  8. Compaction at a Highway Off-Ramp The next series of photos are from the construction of a highway off-ramp in Davis, CA, in 1995. This relatively small earthwork job was performed with very few pieces of equipment (a cat, water truck, grader, and the trucks that transported fill soils to the site). http://cee.engr.ucdavis.edu/faculty/boulanger/geo_photo_album/GeoPhoto.html

  9. This cat is equipped with a blade for shaping the roadway and sheepsfoot rollers for compacting the clayey soils. Fill materials were brought to the site by trucks that spread the materials out in roughly 6 to 8 inch thick layers. The cat spread the material out evenly and compacted it at the same time.

  10. The water truck sprays the earth during compaction to condition the soil to near its optimum moisture content for compaction, and to control dust at the site.

  11. The operators of the water truck and cat sequence their passes across the site. A grader was later used for final shaping of the roadway surface.

  12. Compaction at Los Vaqueros Dam These next series of photos are from Los Vaqueros dam, California, during construction in 1998. This large earthwork project involved numerous pieces of equipment and required a high degree of engineering quality control. http://cee.engr.ucdavis.edu/faculty/boulanger/geo_photo_album/GeoPhoto.html

  13. View of the embankment from the upstream side, with almost 2/3 of the embankment completed. Notice the haul roads on the left abutment.

  14. Backhoes carefully place large rocks (rip-rap) on the upstream face. The rocks are carefully packed together to protect the dam face from erosion.

  15. The different colored soils correspond to the upstream shell (left side), core (darkest), filter, and drain zone (lightest), and downstream shell.

  16. The core materials are being disked (left side) and compacted by sheepsfoot rollers.

  17. A closer view of the disk that breaks the imported soil down into smaller clods for effective moisture conditioning and compaction.

  18. The downstream filter and drain zones are the lighter-colored soils in the middle of this photo.

  19. The imported soils are raked by this caterpillar blade to remove any oversize boulders or cobbles.

  20. III. Factors Affecting Compaction • Soil Type • Moisture Content • Thickness of lift • Degree of compaction (intensity of pressure & the coverage area) • Number of passes

  21. Among the Questions to be Answered on These Two Projects: • Why do we need to compact the soil in the first place? • How much would the fill settle? • What are the strength and permeability characteristics of the constructed dam? How much leakage through and under the dam? • Where do we get the material from (borrow)? • How do we compact the fill (lifts, equipment, etc)? • How much water do we need to add to compact efficiently? • How thick a layer of gravel and rock facing …? • How fast could the fill be placed? • What are the maximum allowable slopes? • How much would the fill settle?

  22. IV. Fundamentals of Shallow Compaction

  23. Excavation, Transportation, and Compaction Stages of Construction Air Air Air Water Water Water Solids Solids Solids Natural Condition Being Hauled In Compacted Fill

  24. Stage 1. Laboratory Compaction

  25. What is compaction? A simple ground improvement technique, where the soil is densified through external compactive effort. Compactive effort + water = From: N. Sivakugan

  26. From: Monahan, 1994

  27. Source: Das, 2002

  28. PROCTOR TESTS • Standard Proctor – historically regarded as non-load-bearing (or light bldg loads, parking lots, lightly secondary roads). • Modified Proctor – load-bearing, “comparable to that obtained with the heaviest rollers under favorable working conditions.” (Sowers, 1979)

  29. Dry density (d) d, max optimum watercontent Water content Compaction Curve Soil grains densely packed - good strength and stiffness - low permeability From: N. Sivakugan

  30. Source: Das, 2002

  31. From: Monahan, 1994

  32. Dry density (d) Zero air void curve (S=100%) Water content Zero Air Void Curve - corresponds to 100% saturation S<100% S>100% (impossible) All compaction points should lie to the left of ZAV curve From: N. Sivakugan

  33. Compaction Curves for Spectrum of Soil Types ED Monahan, 1994

  34. Stage 2. Field Compaction

  35. SPECIFICATIONS • Degree of Compaction R(%) = CR (%)= [(d)field /(d)max-lab]x100% • Typical Spec’s (d)field = CR(%) x (d)max-lab

  36. Relative Compaction – Relative Density Relationships -K.L. Lee, 1971

  37. From: Caterpillar, 1993

  38. Smooth Wheel Rollers • 100% coverage (under the wheels) • Contact pressure = 45 to 55 psi • Sandy & clayey soils

  39. Pneumatic Rubber-Tired Rollers • 4 to 6 (tires) in a row • Contact pressure = 85 to 100 psi • 70 to 80% coverage • Sandy & clayey soils

  40. Sheepsfoot Rollers • Projection area = 4 to 13 in2 • Contact pressure = 200 to 1000 psi • Clayey Soils

  41. Vibratory Rollers Vibration – by rotating off-centers weights Handheld ones for limited access areas Granular soils

  42. From: Greenfield & Shen From: D’Appolonia, et al. 1969

  43. From: D’Appolonia, et al. 1969

  44. Stage 3. Assessment

  45. Sand Cone Method • ASTM D-1556 • Glass (or plastic) jar with a metal cone • Ottawa sand (known wt. & vol.) • Dig a hole – weigh the soil and obtain w(%) • Fill the hole with sand • Determine the new wt. & vol. • Eventually, • d = (dry wt. of excavated soil)/vol. of hole

  46. Rubber Balloon Method • ASTM D-2167 • Similar to above • Vol. is measured utilizing a rubber balloon filled with water

  47. Nuclear Method • Emits gamma rays • Detects how the gamma rays travel thru soil • Amounts of gamma rays detected correlate with the unit weight of soil

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