Lesson Version 1.0 1/15 2 1

Transcription

1 Lesson Version 1.0 1/15 2 1

2 Learning Outcomes Describe the difference between compaction and density and wet & dry density Calculate unit weight Describe the Proctor and LBR Tests and their use Identify and describe material classifications for embankment construction 2-2 Version 1.0 1/15 2 2

3 Terminology What is the difference between COMPACTION & DENSITY 2-3 The contractor uses compaction, (a process) to achieve density (a product). Compactive effort is a measure of the mechanical energy applied to a soil mass. In the field, compactive effort is the number of passes or coverages of the roller of a certain type and weight on a given volume of soil Version 1.0 1/15 2 3

4 Terminology Wet Density vs. Dry Density Wet Density = Total Density = (Total Weight)/(Total Volume) = (Solids+Water+Gas)/(Total Volume) Dry Density = Dry Weight / Total Volume = (Solids+Gas)/(Total Volume) = (Solids)/(Total Volume) 2-4 Wet Density the weight of soil and water occupying a unit volume Dry Density the weight of just the soil solids occupying a unit volume Version 1.0 1/15 2 4

5 Density DENSITY = WEIGHT / VOLUME VOLUME = H x L x D DENSITY = W / (H x L x D) L D H W 2-5 Density is the ratio of the mass of a substance to its volume, expressed, for example, in units of grams per cubic centimeter or pounds per cubic foot. The density of a pure substance varies little from sample to sample and is often considered a characteristic property of the substance. Density often is taken as an indication of how heavy a substance is. Iron is denser than cork, since a given volume of iron is more massive (and weighs more) than the same volume of cork. It is often said that iron is heavier than cork, although a large volume of cork obviously can be more massive and thus be heavier (i.e., weigh more) than a small volume of iron. Weight is the measure of the force of gravity on a body. Since the weights of different bodies at the same location are proportional to their masses, weight is often used as a measure of mass. However, the two are not the same; mass is a measure of the amount of matter present in a body and thus has the same value at different locations, and weight varies depending upon the location of the body in the earth's gravitational field (or the gravitational field of some other astronomical body). A given body will have the same mass on the earth and on the moon, but its weight on the moon will be only about 16% of the weight as measured on the earth. One pound of weight, or force, is the force necessary at a given location to accelerate a one-pound mass at a rate equal to the acceleration of gravity at that location (about 32 ft per sec ). Version 1.0 1/15 2 5

6 Version 1.0 1/15 2 6

7 Exercise CLASS PROBLEM What is the density of the cube? 5 ft. 3 ft. DENSITY = W / V 2 ft. SCALE Weight = 200 lbs. 2-6 Math Problem Work Area Version 1.0 1/15 2 7

8 Learning Outcomes Compaction is considered a when compared to density. Density is considered the when compared to compaction. 2-7 Version 1.0 1/15 2 8

9 Learning Outcomes Wet density is the weight of occupying a unit volume. Dry density is the weight of occupying a unit volume. 2-8 Version 1.0 1/15 2 9

10 Theory What does A represent? Proctor Test Curve What does B represent? DRY DENSITY B A % MOISTURE 2-9 Version 1.0 1/

11 Theory Maximum Density (B) at Optimum Moisture Content (A) Can the Contractor achieve 98% outside the dashed lines? 100% 98% B Target Area Dry Density (pcf) Just Right A % Moisture Where will it be easiest for the Contractor to achieve density? 2-10 Version 1.0 1/

12 Moisture Sensitivity of Soils CLAYEY SOIL Which of these two is affected more by water? PCF Increasing Moisture SANDY SOIL PCF Increasing Moisture 2-11 Version 1.0 1/

13 Maximum Density (Proctor) MODIFIED PROCTOR FM 1 T Moisture Density Relations of Soils Using 10-lb. (4.54-kg) Rammer and 18-inch (457-mm) Drop STANDARD PROCTOR AASHTO T 99 - Moisture Density Relations of Soils Using 5.5-lb. (2.5-kg) Rammer and 12-inch (305- mm) Drop DIFFERENCES Rammer Weight - 10 lb. Drop Height - 18 inches Use spacer disc in mold Use 6 inch molds 56 blows/layer; 5 layers Rammer Weight lbs. Drop Height - 12 inches No spacer disc in mold Use 4 inch molds 25 blows/layer; 3 layers 2-12 The FDOT uses two types of Moisture Density Relation tests: Standard - AASHTO T-99, which employs the use of a 5.5 lb. rammer dropped from a height of 12 inches. Specimens are prepared in 4 inch molds. NOTE: This is the method typically used for obtaining Proctor values on embankment and structure backfill materials. Modified - FM 1 T-180, which employs a 10 lb. rammer dropped from a height of 18 inches. Specimens are prepared in 6 inch molds and a spacer disk used in the bottom of the mold. NOTE: This is the method typically used for obtaining Proctor values for project base, subgrade and MSE wall materials. As road construction equipment and methods improved, it became apparent that construction methods were outdistancing testing methods. In an effort to have Proctor testing be more representative of what was being done in the field, the Modified Proctor was adopted by the FDOT. The Modified Proctor requires substantially more effort in the compaction process than the Standard method. Version 1.0 1/

14 Proctor Applicability MODIFIED PROCTOR Method typically used on FDOT projects for base, subgrade and MSE wall backfill materials. STANDARD PROCTOR Method typically used on FDOT projects for embankment & structure backfill materials. Generally, requirement is 98% of Maximum Density (some isolated cases 95%, such as MSE Walls). Generally, requirement is 100% of Maximum Density (some isolated cases 95%, such as plastic and metal pipe) Version 1.0 1/

15 Limerock Bearing Ratio (LBR) WHAT IS THE LBR? The ratio of the bearing capacity of the material being tested to the bearing capacity of reference limerock PURPOSE OF TEST The Limerock Bearing Ratio Test is useful for determining whether limerock and other soils used for base and subgrade, meet the minimum strength requirements in the plans The standard penetration resistance for a typical crushed limerock in Florida has been standardized to 800 psi. The LBR result is expressed as a percent, without the percent sign. The LBR test is a Florida revision to the California Bearing Ratio test procedure. Version 1.0 1/

16 Limerock Bearing Ratio (LBR) BEARING CAPACITY of MATERIAL_. LBR = x 100 (REFERENCE LIMEROCK) 800 psi 200 LBR vs. % MOISTURE LBR VARIES WITH THE MOISTURE AT THE TIME OF COMPACTION. L B R % MOIST 2-15 Version 1.0 1/

17 DATE COMPACTED MOLD NO. WATER (C.C.) WET WT. + MOLD (GM) WET WT. + MOLD (LBS.) WT. OF MOLD (LBS.) WET WT. (LBS.) WET UNIT WT. (LBS./C.F.) DRY UNIT WT. (LBS./C.F.) LBR BEGIN SOAK END SOAK Limerock Bearing Ratio (LBR) 203 6% L.B.R. AT 0.1 PENETRATION TIME OF TEST MOISTURE DETERMINATION CAN NO. CAN + WET SOIL (GM) CAN + DRY SOIL (GM) WT. WATER (GM) WT. CAN (GM) WT. DRY SOIL (GM) MOISTURE CONTENT (%) DRY UNIT WT. (P.C.F.) % 7% 8% 9% 10% 2-16 WATER CONTENT, % Version 1.0 1/

18 Exercise Using the following graph, answer these questions: 1. What is the Maximum Density? 2. What is the Optimum Moisture? 3. What is the Moisture Range for 98% of the Maximum Density? 4. What is the LBR? 2-17 Version 1.0 1/

19 Exercise L.B.R. AT 0.1 PENETRATION DRY UNIT WT. (P.C.F.) % 7% 8% 9% 10% WATER CONTENT, % 2-18 Version 1.0 1/

20 Learning Outcomes What is the method number for the Standard Proctor? What is the method number for the Modified Proctor? 2-19 Version 1.0 1/

21 Learning Outcomes The standard penetration resistance for the LBR has been standardized to. The LBR value is NOT affected by moisture at the time of compaction. True or False 2-20 Version 1.0 1/

22 Embankment Utilization Design Std Sheet 1 Flexible Pavement 2-21 Version 1.0 1/

23 Embankment Utilization Design Std. 505 Sheets 2 & 3 Rigid Pavement with Treated Permeable Base (2) Rigid Pavement with Asphalt Base (3) 2-22 Version 1.0 1/

24 Embankment Utilization Design Std. 505 Sheet 4 Rigid Pavement with Special Select Option 2-23 Version 1.0 1/

25 Soil Classification Design Std. 505 (Combination of Sheets 1-4) Symbol Soil Classification AASHTO M-145 S Select A-1, A-3, A-2-4** S+ Special A-3*** with Min. Average Lab Permeability Select of 5x10-5 cm/sec as per FM 1-T215 P Plastic A-2-5, A-2-6, A-2-7, A-4, A-5, A-6, A-7 (All with LL<50) H High Plastic A-2-5, A-2-7, A-5 or A-7 (All with LL>50) M Muck A ** Certain types of A-2-4 materials are likely to retain excess moisture and may be difficult to dry and compact. They should be used in the embankment above the water level existing at the time of construction. They may be used in the subgrade portion of the roadbed when approved by the District Geotechnical Engineer. ***When allowed by the plans, some types of A-2-4 material may be approved in writing by the District Materials Engineer. This material must meet the minimum lab permeability requirements, be nonplastic, and not exceed 12% passing the No. 200 sieve. Version 1.0 1/

26 Soil Classification 2-25 Version 1.0 1/

27 2-26 Version 1.0 1/

28 Soil Classification 2-27 Version 1.0 1/

29 2-28 Version 1.0 1/

30 Learning Outcomes From the information on the two preceding pages answer the following questions: Slide 29, could this material be used as roadway embankment? If so where? Slide 30, could this material be used as roadway embankment? If so, where? Determine where A-3 material could be used. Determine where A-2-4 material could be used Version 1.0 1/

31 Compaction Suggestions & Techniques CLAYEY SOILS... SHEEP FOOT ROLLER CLAYEY SOILS BLEEDING... TURN OFF VIBRATOR, STATIC & TRAFFIC ROLLERS SANDY SOILS... WATER & VIBRATE HIGH DENSITY MATERIAL & BRIDGING... LIGHT WEIGHT, NO VIBRATION HIGH SPEED INITIALLY 2-30 Bleeding When moisture is drawn up by capillary action to the surface of the material being compacted. Bridging When the compactive effort does not penetrate the full thickness of the lift being compacted. Walking out When applied to Sheepsfoot rollers refers to attaining less than 1 (25 mm) penetration into the soil. Version 1.0 1/

32 Any Questions 2-31 Version 1.0 1/

33 2-32 Version 1.0 1/