Compaction Process in the Field Dr. Talat Bader

Field Compaction Dr. Talat Bader

DUMPING DOZING

SCARIFYING PICKING UP STONES

WATERING

Quality Assurance water content Water contents must be closely monitored during field compaction. If the soil gets too wet, it will be impossible to compact. If the soil is too dry, it will be difficult to compact. Since it is  easier to add than remove water, it is best to maintain   water contents on the dry side of optimal during field compaction. Water content can be measured instantaneously using nuclear density probes.

Determine the Water Content (in Field) 2.0 1.9 1.8 1.7 1.6 5 10 15 20 25 Water content w (%) Dry density ( Mg / m ) 3 Optimum Moisture Content 100% C Line of optimums A OMC Holtz and Kovacs, 1981

Determine the Water Content (in Field) 2.0 1.9 1.8 1.7 1.6 5 10 15 20 25 Water content w (%) Dry density ( Mg / m ) 3 Check Point Method 100% C Line of optimums A B Increase compaction energy 90% R.C. Control (1) Relative compaction (2) Water content (dry side or wet side) Note: the engineering properties may be different between the compacted sample at the dry side and at the wet side. Holtz and Kovacs, 1981

Check Point Method Destructive Methods (Cont.) Holtz and Kovacs, 1981 Check Point Method Destructive Methods (Cont.) Sometimes, the laboratory maximum density may not be known exactly. It is not uncommon, especially in highway construction, for a series of laboratory compaction tests to be conducted on “representative” samples of the borrow materials for the highway. If the soils at the site are highly variable, there will be no laboratory results to be compared with. It is time consuming and expensive to conduct a new compaction curve. The alternative is to implement a field check point, or 1 point Proctor test. 2.0 1.9 1.8 1.7 1.6 5 10 15 20 25 Water content w (%) Dry density ( Mg / m ) 3 Check Point Method 100% C Line of optimums A B X Field check point X (it should be on the dry side of optimum)

COMPACTING

COMPACTION ON SLOPES

CORNERS COMPACTION NEAR

FINAL LAYER

Estimating Performance of Compacted Soils

Quality Assurance Sampling in the field The fill is sampled at random Monitoring the compaction process should look for systematic errors Dry unit weights of the compacted soil are measured to make sure that they are exceed the minimum acceptable values To assure that the entire fill is compacted above the minimal density requirements The average density measured should be well above the minimum required Statistical methods can be used for this purpose. Sampling rates: Large fills: about 1 sampling per (1000-2000 m2)/lift. Small fills (< 1000m2):  2 or 3 samples / lift Fill with lateral dimensions of 100m by 100m, one would expect to take 5 - 10 sample measurements per lift.

Definitions Relative Compaction R Relative Density Dr Relative Compaction R should not be confused with relative density Dr because they are not the same Relative Compaction R Relative Density Dr df = Field Unit Weight do = Optimum Unit Weight

Relative Compaction (R or R.C.) Relative compaction or percent compaction Correlation between relative compaction (R.C.) and the relative density Dr It is a statistical result based on 47 soil samples. As Dr = 0, R.C. is 80 Typical required R.C. = 90% ~ 95%

Determine the Relative Compaction in the Field Where and When Select the test site. It should be representative or typical of the compacted lift and borrow material. Typical specifications call for a new field test for every 1000 to 3000 m2, Or when the borrow material changes significantly. It is also advisable to make the field test at least one or maybe two compacted lifts below the already compacted ground surface, especially when sheepsfoot rollers are used or in granular soils. Method Field control tests, measuring the dry density and water content in the field can either be destructive or nondestructive. Holtz and Kovacs, 1981

Statistical Evaluation A median density is subjected to assure overall behavior of fill A limit of variation is permitted usually 3-5% less than median. No more than 4-5% of the total tests on project below the limit. Specified Median Limit Actual Median of all tests % Compaction 85 90 95 100 105 110 115 20 30 40 50 60 % Tests Densities are unneeded Reject

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