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Enabling Learning Objective D - PowerPoint PPT Presentation

Enabling Learning Objective D. ACTION: Predict the California Bearing Ratio of a particular soil. CONDITION: Given student workbook for EOBC BD-02-02, charts & tables for EOBC BD-02-02, pencil and paper.

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ACTION: Predict the California Bearing Ratio of a particular soil.

CONDITION: Given student workbook for EOBC BD-02-02, charts & tables for EOBC BD-02-02, pencil and paper.

STANDARD: Predicted the California Bearing Ratio of a particular soil by analyzing results from laboratory testing, USCS Correlation, and expedient methods.

• CBR - California Bearing Ratio

• MMC - Minimum Moisture Content

• OMC - Optimum Moisture Content

• MDD - Maximum Dry Density

• BPL - Blows Per Layer

• CE - Compaction Effort

• CE56 - Compaction Effort, 56 Blows Per Layer

• Specification Block - The range where dry density within 5% and moisture content within 4% come together to determine project requirements.

Pg 26 SH

CBR =

X 100

Standard Stress

CBR Defined

A soil’s ability to support a load based on its strength relative to a limestone standard.

CBR measures the shearing resistance of a soil under controlled conditions of density and moisture content.

Pg 27 SH

based on 3/4" aggregate

CBR Relationship Curve

1500

1000

Stress (Psi)

500

.2

.1

Penetration (in)

Pg 27 SH

.1"

500

x 100 = 25

.2"

x 100 = 33.3

1000

1500

CBR Relationship Curve

1500

Limestone Standard

1000

Stress (Psi)

500

250

.2

.1

Penetration (in)

Pg 27 SH

Dr. Doug Dert

Dr. Ima Knird

• Compaction Test: Requires 3 separate tests (12, 26, & 56 BPL). 5 molds required for each test , for a total of 15 tests per sample.

• Plot density and moisture

curves

• Soak CBR mold for 4 days in

water with surcharge weights

that simulate a weight equal to the expected pavement/base weight.

Pg 28 SH

Pg 28 SH

• Free-Draining (Sand)

• Swelling (Clay)

• Non-Swelling (Silt)

Pg 30 SH

• U-Shaped Curves: Free-Draining Soils

• Bell-Shaped Curves: Swelling & Non-Swelling Soils

FM 5-410 Military Soils Engineering

Page 8-10, Figure 8-5 (CBR Design Flowchart)

or Page 8 of Charts and Tables

Pg 31 SH

105% MDD= 137.6 pcf

Specification Block

MDD= 131 pcf

130

DRY UNIT WEIGHT (Pounds per cubic feet)

120

MMC= 9.7%

MMC+4%=13.7%

110

3

7

11

15

Free-Draining Soil

• FM 5-410, Military Soils Engineering, Page 8-10, Fig 8-5.

• U-Shaped Curve

• Free-Draining Soil

• Peak of curve is MDD

• WC at peak is MMC

• Moisture range is MMC+4%

• Density range is MDD to 105% MDD

Pg 9 C&T, Pg 31 SH

MOISTURE (water) CONTENT (Percent of dry weight)

Soil that has more than a 3% volume

change with the addition of water

FLEX PAVEMENT

BASE COURSE

SUBBASE

CAPILLARY RISE

Pg 30 SH

The Army standards permits no more than a 3% swell to occur after a soil has been placed and compacted. Therefore swelling soils must be pre-swelled to a moisture content that will result in < 3% swell

FLEX PAVEMENT

CAPILLARY RISE

Pg 30 SH

Plasticity Index

0 - 14: Non-swelling14 - 25: Marginal Swell25 - 40: Critical Swell > 40 : Excessive Swell

PL

LL

PI

Liquid State

SolidState

Plastic State

100

95% MDD= 97.85 pcf

DRY UNIT WEIGHT (Pounds per cubic feet)

Specification Block

90% MDD= 92.7 pcf

90

MMC= 17.6%

MMC+4%=21.6%

80

12

16

20

24

Swelling Soil

• Bell-Shaped Curve

• Look at swell curve

• Swell curve exceeds 3% at any point

• Swelling soil

• Peak of curve is MDD

• Look at swell curve to determine MMC

• Moisture range is MMC+4%

• Density range is 90% to 95% MDD

MDD=103 pcf

Pg 9 C&T, Pg 31 SH

MOISTURE (water) CONTENT (Percent of dry weight)

130

DRY UNIT WEIGHT (Pounds per cubic feet)

95% MDD= 122.74 pcf

120

Specification Block

90% MDD= 116.28 pcf

0MC= 9.1%

OMC–2%= 7.1%

0MC+2%=11.1%

110

3

7

11

15

Non-Swelling SoilPI > 5

• Bell-Shaped Curve

• Look at swell curve

• Swell curve never exceeds 3% swell

• Non-Swelling soil

• Peak of curve is MDD

• Water Content at peak is OMC

• Moisture range is OMC +/-2%

• If PI > 5, Density range is 90% to 95% MDD

MDD=129.2 pcf

Pg 9 C&T, Pg 31 SH

MOISTURE (water) CONTENT (Percent of dry weight)

MDD=129.2 pcf

130

DRY UNIT WEIGHT (Pounds per cubic feet)

Specification Block

95% MDD= 122.74 pcf

120

0MC= 9.1%

OMC–2%= 7.1%

0MC+2%=11.1%

110

3

7

11

15

Non-Swelling SoilPI < 5, CBR < 20

• Bell-Shaped Curve

• Look at swell curve

• Swell curve never exceeds 3% swell

• Non-Swelling soil

• Peak of curve is MDD

• Water Content at peak is OMC

• Moisture range is OMC +/-2%

• If PI < 5, CBR < 20,Density range is 95% MDD to MDD

Pg 9 C&T, Pg 31 SH

MOISTURE (water) CONTENT (Percent of dry weight)

105% MDD= 135.66 pcf

Specification Block

130

MDD=129.2 pcf

DRY UNIT WEIGHT (Pounds per cubic feet)

120

0MC= 9.1%

OMC–2%= 7.1%

0MC+2%=11.1%

110

3

7

11

15

Non-Swelling SoilPI < 5, CBR > 20

• Bell-Shaped Curve

• Look at swell curve

• Swell curve never exceeds 3% swell

• Non-Swelling soil

• Peak of curve is MDD

• Water Content at peak is OMC

• Moisture range is OMC +/-2%

• If PI < 5, CBR > 20,Density range is MDD to 105% MDD

Pg 9 C&T, Pg 31 SH

MOISTURE (water) CONTENT (Percent of dry weight)

130

DRY UNIT WEIGHT (Pounds per cubic feet)

120

110

3

7

11

15

Specification Block

Anything

plotted to the

right of this line

is too wet

Anything

plotted to the

left of this line

is too dry

Anything

plotted above

this line

is over

compacted

Specification Block

Anything

plotted below

this line

is under

compacted

Pg 34 SH

MOISTURE (water) CONTENT (Percent of dry weight)

Too Much Compaction effort, water content good

Too much time wasted, Adjust number of passes

130

Under compacted/ Too Dry

Under compacted/ Too Wet

DRY UNIT WEIGHT (Pounds per cubic feet)

120

Scarify, Add Water, Mix Soil, Retest, Re-compact, Retest.

Scarify, Allow to dry, Re-Compact, Retest

110

3

7

11

15

Corrective Actions

Specification Block

MOISTURE (water) CONTENT (Percent of dry weight)

Pg 32-34 SH

• USCS Correlation

• Pentrometers

• Trafficability Test Set

• Airfield Cone Pentrometer

• Dual (Cone) Mass Pentrometer

Pg 28 SH

FM 5-410, Page 5-11, Table 5-3

Characteristics Pertinent to Roads & Airfields

Examples:

GW = 40 - 80

SW = 20 - 40

SC = 5 – 20

Note: If this method is used, assume lowest CBR value to be on the safe side.

• Trafficability Test Set:

• Airfield Cone Pentrometer:

Used for non-gravelly soils

• Dual (Cone) Mass Pentrometer

Used for all soil types

ACTION: Discuss the theory of California Bearing Ratio (CBR) and CBR expedients.

• CBR Theory

• CBR Timeline

• 3 Soil Groups

• Compaction Curves

• Specification Block

• CBR Expedients

Questions?

Q: What does CBR stand for?

A: California Bearing Ratio (PG 24)

Q: You have a soil with the CBR of 80 available to be used as well as a soil with the CBR value of 40. Which soil is stronger

A: CBR of 80 is stronger. The higher the CBR the stronger the soil, the lower the CBR the weaker. (PG 24)

Q: If you test a road for compaction and you discover that you are too dry and under compacted, what steps would you take?

A: Scarify, add water, mix soil, re-test moisture content, re-compact, re-test moisture content and density. (PG-31)

ACTION: Develop a quality control plan for a horizontal construction project.

CONDITION: Given student workbook for EOBC BD-02-02, charts & tables for EOBC BD-02-02, pencil and paper.

STANDARD: Developed a quality control plan for a horizontal construction project to include: Identified equipment available and equipment needed to test and adjust a particular soils density and moisture content

• Sand Cone Method

• MC-1 Nuclear Moisture-and-Density Tester

(Nuke Gauge)

• Common Sense

Pg 29 Workbook

Sand Cone Method(Measures the density of the soil)

Sand Cone Method(Measures the density of the soil)

Sand Cone Method(Measures the density of the soil)

“Nuke Gauge”

Provides both moisture

and density determination

MC-1

TROXLER

6 - 8”

Cesium (Cs) 137 and Americium (Am) 241

Nuclear Densometer

WARNING: Operator must be trained.

WARNING: Gauge must be stored in locked, unoccupied and isolated areas.

• Does soil appear to be too wet or too dry?

• Is compaction equipment “Riding Out”?

• Does equipment “Pump” as it drives over?

• CE56 results are not needed

Sheepsfoot Roller

Smooth-drum Vibratory

9-Wheel Pneumatic

Compaction Equipment

Other Equipment(Used to adjust moisture content)

FM 5-410, Page 8-13, Table 8-3

Soil classification and compaction

requirements (average)

If soil classification is GP (Poorly graded gravel) would you use a towed sheepsfoot roller to compact?

No, Table 8-3 does not recommend using this type of compaction equipment for this type of soil

Factors to consider when selecting compaction equipment include but are not limited to:

• Type of soil

• Desired density

• Desired lift thickness

• Numbers of passes required

• Size of the project

• Available equipment

Pg 29 Workbook

• Use test strips

• Test each lift after compaction

• Test roads and airfields every 250 linear feet

• Stagger tests on each side of the centerline

• Test parking lots every 250 square yards

• If initial checks are satisfactory increase distance

Pg 29 Workbook

Used to determine best roller to use,

amount of moisture that needs to be added, and amount of passes needed by the selected piece of equipment.

40 to 100 yards

Typical 6” lift thickness

6 Yards

• Determines the correct equipment and equipment effort needed for the job at hand.

• A test strip is used to determine the best suited compaction equipment for your project.

• It determines the amount of passes necessary to attain the proper density of the soil.

• Test strip helps to determine the optimum thickness of each lift.

V

T

T

V

T

P

V

P

T

P

P

QC Plan Development(using test strip data)

140

100 %

135

95 %

130

Dry Density

125

90 %

120

115

110

0 1 2 3 4

# of Passes

P - PNUEMATICT - TAMPING FOOTV - VIBRATORY

Pg 30 Workbook

ACTION: Discuss quality control measures in the theater of operation.

• Density and moisture testing equipment

• Compaction equipment

• Equipment used to adjust moisture content

• Quality control methods

Questions?

Q: What equipment can be used to test the soils density?

A: Sand cone, Nuke gauge. (with CE56 results)

Q: If compaction equipment is riding out but your tests do not plot within your specification block what might you consider?

A: That your CE56 results are not accurate and compaction is good. (Use common sense)

Q: What is the best way to determine which equipment to be used, how much water to add, and how many passes should be made to obtain compaction specifications?

A: Test strips