Objectives Be able to use basic volume weight

Objectives Be able to use basic volume weight equations v Understand principal of soil compaction. v Explain how the compaction test is used in design and quality control v Be able to perform basic compaction test (LAB EXERCISE) v plot compaction data and evaluate for accuracy v Understand procedure for Atterberg Limit Tests (LAB EXERCISE) v

Review of Compaction Principles v Compaction Tests are not suitable for soils with more than 30 % by weight of the sample being larger than a ¾” sieve. v Compaction tests are not usually performed on soils with 12 % or fewer fines

Review of Compaction Principles v Relative Density testing is used for clean sands and gravels – covered later in class v Standard Procedures for testing are available for soils with some gravel (less than the maximum allowable content)

Principle of compaction v Theory developed by R. R. Proctor in 1930’s in California v Three Factors determine the density that results from soil compaction

Proctor Developed Principle v. Three variables determine the density of a compacted soil – The energy used in compaction – The water content of the soil – The properties of the soil

Dry Density, pcf State Diagram 100 % saturation curve Water content, %

Dry Density, pcf State Diagram Water content, %

Energy Used in Compaction v Assume you have some clay soil that is at a water content of 16 percent. v Look at the effect different compaction energy has on the density of the soil. v Energy expressed as number of passes of a sheepsfoot roller on a lift of soil

Dry Density, pcf At this water content, energy has a large effect on compacted density 10 passes of equipment 4 passes of equipment 3 passes of equipment 2 passes of equipment 1 pass of equipment Water content, %

Dry Density, pcf At this point, the sample has had most of its air driven out by the compaction 10 passes of equipment 100 % saturation line Water content, %

Dry Density, pcf At a lower water content, energy has little effect on the compacted density of a clay soil 10 passes of 43 passes equipment passes of of equipment 2 equipment passes of equipment 1 pass of equipment Water content, %

Compacting at low water contents v At low water contents, insufficient water is available to lubricate the particles and allow them to be rearranged into a dense structure. v The frictional resistance of dry particles is high

Dry Density, pcf At a very high water content, energy has little effect on the compacted density of a clay soil because the water is incompressible and takes the applied force without densifying the soil This results in a term called pumping 1043 passesof of equipment 2 equipment passes of equipment 1 pass of equipment Water content, %

Compacting Very Wet Soil At this point, few air pockets remain – compaction forces are carried by water in soil which is incompressible

Water has Zero Shear Strength

Water has Zero Shear Strength

Effect of Water Content v Now examine the effect of just changing the water content on a clay soil, using the same energy each time the soil is compacted. v For example, assume soil is spread and compacted with 4 passes of a sheepsfoot roller each time. v Examine using State Diagram

Dry density, pcf Effect of Water Content 99. 0 pcf Sample 1 compacted at 12 % water – Dry Density is 99. 0 pcf 12 % Water content, %

Dry density, pcf Effect of Water Content Sample 2 compacted at 14 % water – Dry Density is 104. 5 pcf 14 % Water content, %

Dry density, pcf Effect of Water Content 105. 5 pcf Sample 3 compacted at 16 % water – Dry Density is 105. 5 pcf Water content, % 16 %

Dry density, pcf Effect of Water Content 98. 5 pcf Sample 4 compacted at 18 % water – Dry Density is 98. 5 pcf Water content, % 18 %

Dry density, pcf Effect of Water Content @ constant energy Maximum dry density, pcf Optimum water content, % Water content, %

Now, perform the same test at a different (Higher energy) on the soil Dry density, pcf 10 passes of sheepsfoot roller Water content, % 4 passes of sheepsfoot roller

Dry density, pcf Effect of Soil Type on Curves 80 -95 pcf Plastic Clay Soils have Low Values of Maximum Dry Density Water content, %

Dry density, pcf Effect of Soil Type on Curves Plastic Clay Soils have high values for optimum water content (20 -40 %) 20 -40 % Water content, %

Dry density, pcf Effect of Soil Type on Curves Plastic Clay Soils have a Flat Curve for Lower Energies Density Water content, %

Effect of Soil Type on Curves Dry density, pcf 115 -135 pcf Sandy Soils with Lower PI’s have High Values of Maximum Dry Density Water content, %

Dry density, pcf Effect of Soil Type on Curves Sandy Soils with Lower PI’s have Low Values of Optimum Water Content 8 -15 % Water content, %

Dry density, pcf Effect of Soil Type on Curves Sandy Soils have a Steep Curve – Short distance from plastic to liquid states of consistency Water content, %

Summary Lower PI – Sandier Soils in this Region Dry density, pcf 110 -135 95 -120 Higher PI – Clayey Soils in this Region 75 -95 Water content, % Intermediate PI Soils in this Region

Summary Lower PI – Sandier Soils in this Region Dry density, pcf Intermediate Higher PI – PI Soils in thisin Clayey this. Region 8 -14 Water content, % 12 -20 20 -40

Family of Curves (Covered Later)

d, dry density, pcf Family of Curves Zero air voids curve not parallel to line of optimums at upper end Line of Optimums water content, %

Proctor’s principle of compaction v Using a standard energy, if a series of specimens of a soil are compacted at increasing water contents, the resultant dry density of the specimens will vary. The density will increase to a peak value, then decrease.

Principle of Compaction v A plot of the dry density versus the water content from a compaction test will be parabolic in shape. v The peak of the curve is termed the maximum dry density, and the water content at which the peak occurs is the optimum water content.

Standard Proctor Energies v. Several standard energies are used for laboratory compaction tests – Standard – 12, 400 ft-lbs/ft 3 – Modified – 56, 000 ft-lbs/ft 3 – California – 20, 300 ft-lbs/ft 3

Standard Proctor Compaction Test Summary 5. 5 # hammer v Uses 5. 5 pound hammer v dropped 12 inches v mold filled in 3 lifts v 25 blows of hammer per lift v Total energy is 12, 400 ft-lbs/ft 3 12”drop 3 lifts

Modified Proctor Compaction Test Summary 10 # hammer v Uses 10 pound hammer v dropped 12 inches v mold filled in 5 lifts v 25 blows of hammer per lift v Total energy is 12, 400 ft-lbs/ft 3 18”drop 5 lifts

Proctor Compaction Test Summary v Several Standard molds are used depending on maximum particle size in sample – 4”diameter mold (1/30 ft 3) used for soils with low gravel contents – Method A for soils with < 20 % gravel – Method B for soils with > 20 % gravel and < 20 % larger than 3/8”

Proctor Compaction Test Summary v Several Standard molds are used depending on maximum particle size in sample – 6”diameter mold (1/13. 33 ft 3) used for soils with significant gravel contents – More than 20 % gravel larger than 3/8” – Must have less than 30 % larger than 3/4”

Proctor Compaction Test Summary v Standardized tests are not available for soils with more than 30 percent by weight of the total sample being larger than 3/4”in diameter gravels v ASTM Compaction Test Methods are – D 698 A – D 698 B – D 698 C D 1557 A D 1557 B D 1557 C

Proctor Compaction Test Summary v Prepare 4 to 5 specimens at increasing water contents about 2 % apart. Example prepared samples at 14, 16, 18, and 20 percent. Use range of moistures based on feel and experience.

Proctor Compaction Test Summary Hammer v Then, compact each sample into a steel mold with standard procedures Cured soil Compaction mold

Proctor Compaction Test Summary v Then, strike off excess soil so the mold has a known volume of soil.

Proctor Compaction Test Summary For each sample, measure the weight and the water content of the soil in the mold v The mold volume and weight are pre-measured. Don’t assume nominal volume of 1/30 ft 3 or 1/13. 33 ft 3 v Calculate moist density v Calculate dry density v Plot dry density and water content for each point v

Class Problem v Calculate Moist density, dry density

Class Problem Mold wt = 4. 26 #, Mold Vol. = 0. 03314 ft 3

Class Problem v. Calculate Moist density, dry density v. Plot curve of dry density versus water content v. Determine Maximum dry density and optimum water content

Set Up Plot – Form SCS-352 110 5 pounds 90 {

Set Up Plot – Form SCS-352 Make each vertical division equal to 1 percent water content

Class Problem v Calculate Moist density, dry density v Plot curve of dry density versus water content v Determine Maximum dry density and optimum water content v Plot zero air voids ( 100 % saturation curve assuming specific gravity = 2. 68

Zero Air Voids Curve v After you plot a compaction test, plotting a zero air voids curve is very important. This curve is also called the 100 % saturation curve v This curve shows for a range of dry density values what the saturated water content is for any given value

Compaction Problem Zero air void equation Assume 3 values of d and calculate wsat%

Assumed dry density assumed = 105 Gs pcf= 2. 70 Unit wt. water = 62. 4 100 % Saturation Curve 95 % Saturation Curve wsat(%) = 22. 1(%) 75 % Saturation Curve

Zero Air Voids Curve

Plotted Class Problem

Zero Air Voids Curve v The 100 % saturation curve is used to judge the reliability of the compaction curve and of field measurements of compacted soil density and water content v Compacted soils for NRCS specifications are usually at a degree of saturation of about 75 to 95 percent

100 % Saturation Curve 95 % Saturation Curve 75 % Saturation Curve

Review of Compaction v Evaluating Compaction Tests – Standard requirements - spread in water content about 2 % and at least two points above and below optimum – Typical shape - soil type ?

Compaction Problem Other given information: LL = 47, PI = 30, classified as CL soil Gs = 2. 68

Evaluating compaction test 2. 1 % 2. 7 % Are points about two percent apart ?

Evaluating compaction test Are two points below and 2 above optimum ?

Review of Compaction Optimum water content about 80 % saturated water content ? Acceptable range is 75 -95 Optimum w% = 21. 0 % sat = 21. 0÷ 23. 6=89% 102. 5 pcf

Plotted Class Problem wopt/wsat = 21. 0/23. 6 = 89 % wsat @ 102. 5 pcf = (62. 4/102. 5 - 1/2. 68) * 100 = 23. 6 %

Review of Compaction Wet side parallel to saturation curve at 90 % saturation ? % Sat = 24. 3 ÷ 26. 4 = 92. 0 % d, pcf Check a point on wet side at 98 pcf, w % on curve is 24. 3% w, %

Plotted Class Problem wopt/wsat = 24. 3/26. 6 = 91 % wsat @ 98. 0 pcf = (62. 4/98. 0 - 1/2. 70) * 100 = 26. 6 %

Review of Compaction üEvaluating Compaction Tests u. Typical value for fine-grained soils compared to Navdocks equations dmax = 130. 3 - 0. 82 *LL + 0. 3*PI wopt = 6. 77 + 0. 43 * LL - 0. 21 * PI

Review of Compaction üEvaluating Compaction Tests u. Typical value for fine-grained soils compared to Navdocks equations dmax = 130. 3 - 0. 82 *47 + 0. 3*30 = 100. 8 pcf OK - test value was 102. 5 pcf wopt = 6. 77 + 0. 43 * 47 - 0. 21 * 30 = 19. 6 % OK Test value was 21. 0 %

Purposes of compaction v Soils are compacted to improve the engineering properties over those of loosely placed soils. v The engineering properties are affected both by the density to which the soil is compacted and the water content at which it is compacted

Role of compaction tests in earth fill projects v Samples are obtained in site investigation and sent to laboratory for testing v Soils are tested to determine reference density - as well as other index properties v Engineering properties are measured by testing at a percentage of the reference test density. For example, a shear test might be performed at 95 percent of the Standard Proctor maximum dry density of the soil.

Role of compaction tests in earth fill projects v The engineering properties are used in analyses to determine a suitable design v For example, the shear strength is used in a slope stability analyses v If the engineering properties allow a satisfactory design, then the degree of compaction is used in a contract specification.

Role of compaction tests in earth fill projects v If an unsatisfactory design results, the soil is re- tested at a different degree of compaction to obtain better engineering properties v The design is re-analyzed and the process repeated until a final satisfactory degree of compaction is decided v Then the degree of compaction is used in a contract specification.

Role of compaction tests in earth fill projects v Quality control processes are used to ensure that the earth fill is compacted to the degree of compaction specified, within a range of specified water contents v Field compaction tests are performed to assure that the proper reference density is being used

Compaction Tests as Used in Design of an Earth Fill

Example of Process v Sample obtained to determine suitability as clay liner v Sample Sent to Laboratory v Laboratory performs Standard Proctor Test v A Permeability Test is performed at 95 % of maximum Standard Proctor Dry Density

Example of Process v The sample is remolded at 2 percent wet of optimum (for this sample, 85 % saturated) v The permeability test measures an acceptably low permeability v A recommendation is given to the field office that compaction to this combination of density and water content results in acceptably low permeability

Example of Process v During construction, measurements of dry density and water content are made during construction. v If the degree of compaction and percent saturation are equal to or better than specified, the liner is judged to have a low permeability and is considered acceptable.

Class Problem 2 v A compaction test measures a maximum dry density of 104. 0 pcf and an optimum water content of 18. 0 %. The soil has an estimated Gs value of 2. 68 v A contract requires compaction to 95 % of maximum dry density at a water content of optimum or greater

Class Problem 2 v A field test measures a moist density of 126. 3 pcf and a water content of 23. 4 % v Does the compacted fill meet the contract requirement ? v Use the values given for measured moist density and water content, calculate the dry density v Assume a Gs value of 2. 68 and compute a wsat value

Class Problem v Compare the reported compaction water content to theoretical saturated water content v Compacted soils are commonly in the range of 75 -95 percent saturated v What do the results tell you about the reliability of the field data? v What would you look for to explain any problems?

Conclusions of Class Problem v The measured data appears to have problems. v Possible errors are in the measurement of the dry density, the water content, or the specific gravity value used in computations v Recommend investigating most probable causes