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
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.
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.
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.
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
View of the embankment from the upstream side, with almost 2/3 of the embankment completed. Notice the haul roads on the left abutment.
Backhoes carefully place large rocks (rip-rap) on the upstream face. The rocks are carefully packed together to protect the dam face from erosion.
The different colored soils correspond to the upstream shell (left side), core (darkest), filter, and drain zone (lightest), and downstream shell.
The core materials are being disked (left side) and compacted by sheepsfoot rollers.
A closer view of the disk that breaks the imported soil down into smaller clods for effective moisture conditioning and compaction.
The downstream filter and drain zones are the lighter-colored soils in the middle of this photo.
The imported soils are raked by this caterpillar blade to remove any oversize boulders or cobbles.
III. Factors Affecting Compaction a)Soil Type b)Moisture Content c)Thickness of lift d)Degree of compaction (intensity of pressure & the coverage area) e)Number of passes
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?
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)
Zero Air Void Curve All compaction points should lie to the left of ZAV curve - corresponds to 100% saturation Water content Dry density ( d ) Zero air void curve (S=100%) S<100% S>100% (impossible) From: N. Sivakugan
Compaction Curves for Spectrum of Soil Types ED Monahan, 1994
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
Rubber Balloon Method ASTM D-2167 Similar to above Vol. is measured utilizing a rubber balloon filled with water
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