presented by: national ready mixed concrete association...astm d1883-standard test method for cbr...
TRANSCRIPT
Soils 101: The Importance of Soil In Pavement Design and
Construction Part 1Soils 101: What to Know for a Successful Paving
Project
Presented By: National Ready Mixed Concrete Association
2
National Ready Mixed Concrete Association
• National Trade Association – Established in 1930 • HQ in Alexandria, VA • 1,400+ Member Companies • NRMCA Represents ~75% of North American Ready Mixed Production • Mission - Serve Industry and Partners Through:
• Compliance and Operations • Engineering • Government Affairs • Local Paving: Pave Ahead™ Initiative (PaveAhead.com)
• Structures and Sustainability: Build With Strength™ Initiative
Interested in becoming a member, visit: www.nrmca.org/membership/
Your Instructors Today…
• Brian Killingsworth, P.E. – NRMCA Local Paving, Division Head – 28 Years in Practice – Pavement Design, Materials, Construction, Forensics
• Luke McHugh, P.E. – NRMCA Local Paving, Northeast Region – 33 Years in Practice – Civil Design – Aviation Emphasis
More information at paveahead.com/experts/
5
NRMCA Disclaimer
• This presentation has been prepared solely for information purposes. It is intended solely for the use of professional personnel, competent to evaluate the significance and limitations of its content, and who will accept full responsibility for the application of the material it contains. The National Ready Mixed Concrete Association and any other organizations cooperating in the preparation of this presentation strive for accuracy but disclaim any and all responsibility for application of the stated principles or for the accuracy of the content or sources and shall not be liable for any loss or damage arising from reliance on or use of any content or principles contained in this presentation.
• Unless otherwise indicated, all materials in this presentation are copyrighted to the National Ready Mixed Concrete Association. All rights reserved. Therefore reproduction, modification or retransmission in any form is strictly prohibited without the prior written permission of the National Ready Mixed Concrete Association.
• ©2015 National Ready Mixed Concrete Association.
6
Instructions • Everyone is muted. • Webinar is being recorded and posted at paveahead.com/education/. • Type questions in the question box. • Download the handouts in the GoToWebinar control panel. • Credit for course:
– Based on attendance. – Survey (Quiz) – In follow-up e-mail, not required, but encouraged. – Attendance Certificate – In follow-up e-mail 1 hour after webinar. – AIA members – Attendance registered with AIA-CES if AIA number provided.
• AIA-CES Course SOIL101: 1.5 LU|Elective & 1.5 PDH for Engineers
• Learning Objectives:
– Recognize how a soil sampling and testing plan is developed for a paving project.
– Comprehend a geotechnical engineering report.
– Learn the various ways soil strength can be determined for use in pavement design.
– Understand the importance of the soil moisture-density relationship in construction.
8
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Structure – Surface course – Base course – Subbase course – Subgrade
11
Subgrade stresses differ considerably.
Strength.
12
+++ (Tensile Stress)
++ (Tensile Stress)
Transverse Cracking Joint Faulting
14
Longitudinal Joint
Transverse Joint
Subgrade Subbase
Surface Texture
Concrete Materials
Tie bars
Concrete Pavement Design
• Thickness is a Function of Key Parameters: – Design life – Traffic loads & frequencies – Concrete strength – Subgrade/subbase support (strength characterization)
• Jointing & Reinforcement: – Load transfer considerations – Prevention of uncontrolled cracking
• Other Design Considerations: – Reliability (Factor of Safety) – Grades & drainage – Edge support conditions (e.g. curb & gutter, shoulder…) – Pavement/subsurface interaction
Source: PavementInteractive.org
How Do We Evaluate The Suitability of Subgrade Soils?
Geotechnical Engineering Study and Report • Classification (Gradation, Atterberg Limits, etc.) • Depth to Bedrock • Depth to Water Table • Potential for Compaction • Presence of Weak or Soft Layers or Organics • Susceptibility to Frost Action or Excessive Swell • Soil Strength Characteristics – Critical Parameter For Pavement Design
19
Stay Tuned, More Details To Come…
20
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
Data Collection Activities - Drilling
• Geotechnical Drilling (New Pavements) – Minimum 5 feet below final top of subgrade elevation** – Spacing a function of roadway type and soil conditions – High plasticity soils: increase drilling depth to 10 to 15 feet – Strength testing must be representative of subgrade soil supporting pavement materials – May require larger augers at some boring locations for material collection
• Geotechnical Drilling (Existing Pavements) – Obtain existing pavement thicknesses – Consider test pits if full depth reclamation is possible – Spacing as stated above – Drilling depths as stated above – Materials for soil strength as stated above
**Airport, Industrial, and Port Facilities may be different!
23
• Standard Penetration Test (SPT) blows/ft • Material Descriptions • Moisture and Water Table Depth (if encountered)
• Bedrock Depth (if encountered)
– Density – % Swell (freeze and/or moisture related) – Subgrade Strength Characterization
25
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Coarse or Fine Grained • Typically Classified as:
– Gravel – Sand – Silt – Clay (Lean or Fat: Based on Plasticity*) – Or a combination of any of the above
• e.g. Sandy Gravel With Clay *Soil plasticity refers to the manner in which water interacts with the soil particles.
27
States of Consistency for Cohesive Soils (Soil Passing #40 Sieve)
28
Atterberg Limits
• Liquid Limit (LL) • Plastic Limit (PL) • Plasticity Index (PI) • PI = LL - PL
Albert Atterberg 1846-1916
29
• AASHTO Classification System – (AASHTO M 145)
30
Source: ASTM D 3282
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Water Effect – Capillary Forces
36
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10 11 12 13 14 15 16 17 18 19 20 21 22 23
gdry max
Chart1
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103.9
107.6
109.4
108.8
106
103
Sheet1
wc
gamma
12
103.9
14
107.6
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109.4
18
108.8
20
106
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103
Volume of Proctor Mold (ft3) 1/30 1/30 1/30 1/30 1/30 1/30
Weight of wet soil in the mold (lb) 3.88 4.09 4.23 4.28 4.24 4.19
Water Content (%) 12 14 16 18 20 22
Wet Unit Weight (lb/ft3) 116.4 122.7 126.9 128.4 127.2 125.7
Dry Unit Weight (lb/ft3) 103.9 107.6 109.4 108.8 106.0 103.0
Sheet2
Sheet3
37
Soil Compaction
• Soil compaction is the process of “artificially” increasing the density (unit weight) of a soil by compaction (by application of rolling, tamping, or vibration).
• Moisture-density testing as practiced today was started by R.R. Proctor in 1933. – His method became known as the “standard Proctor” test.
Ralph Roscoe Proctor, PE (1894 -1962)
38
Moisture and Density Relationships of Soils & Base – Laboratory Methods
• ASTM D 698 - Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12,400 ft-lbs/ft3)
• ASTM D 1557 - Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbs/ft3)
• AASHTO T 99 - Moisture-Density Relations of Soils Using a 5.5-lb Rammer and a 12-in. Drop • AASHTO T 180 - Moisture-Density Relations of Soils Using a 10-lb Rammer and a 18-in. Drop
39
Soil Strength is usually greatest at its maximum dry density.
40
Total Compaction Energy Affects Maximum Dry Density and Optimum Moisture
Typical Compaction Curves
• Compaction Increases Soil Strength
• Compaction Achieves Soil Support Uniformity
• Provides Stable Platform for Pavement Layers *To Optimum or Just Above the Optimum Moisture Content
Source: Equipment World
42
Soil Compaction in the Lab: 1- Standard Proctor Test 2- Modified Proctor Test
Standard Proctor Test Modified Proctor Test
43
Compaction Curve
Wet to Optimum
Dry to Optimum
Soil Compaction in the Lab: 1- Standard Proctor Test 2- Modified Proctor Test
wc1 wc2 wc3 wc4 wc5 gd1 gd2 gd3 gd4 gd5
4 inch diameter compaction mold. (V = 1/30 of a cubic foot)
W = 5.5 or 10 pound hammer
25 blows per layer
Increasing Water Content
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Some Strength Parameters Require Complex & Expensive Testing Devices.
• Some Strength Parameters Cannot Be Determined in the Laboratory.
46
(Not Commonly Used)
(More Commonly Used)
– California Bearing Ratio (CBR) • Measures shearing resistance • Units: percent • Typical values: 0 to 20 for soils
– Resilient Modulus (MR) • Measures stress-strain relationship (an engineering property)
• Units: psi or MPa • Typical values: 3,000 to 15,000 psi for soils
– K-value (k) **Typically required for concrete pavement design**
• Measures resistance to deflection • Units: psi/in • Typical Values: 75 - 200 psi/in for soils
Source: FHWA
• Resistance of the material to uniaxial penetration.
• Measure of soil shear strength relative to standard crushed stone.
• Field and laboratory test.
– An empirical test.
Source: www.dur.ac.uk/
Source: www.matest.com
ASTM D1883-Standard Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils
51
California Bearing Ratio (CBR)
• Load a piston (area = 3 in2) at a constant rate (0.05 in/min)
• Record load every 0.1 inch penetration
• Total penetration not to exceed 0.5 inch
• Draw load-penetration curve
0
100
200
300
400
500
600
700
Moisture Content
C B
R
Use relevant or saturated value for moisture content when assessing soils under laboratory conditions.
Chart3
0.043
0.116
0.179
0.217
0.259
0.4
0.5
Typical Testing Machine Source: Humboldt
Surcharge Weights
• Simulate the weight of pavement.
• Prevent heaving up around the piston.
54
55
Dynamic Cone Penetrometer (DCP)
• Originally developed in the Republic of South Africa (RSA) where it has been used with related tools and analyses for over 25 years.
• Equipment can be purchased for about $1,000 to $3,000 (US).
56
• Standard Test Method:
– ASTM D6951-Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications
– Equipment can come with different hammer weights:
• 8 kg (17.6 lb.)
• 4.6 kg (10.1 lb.)
– USACE CBR—DCP correlations in the ASTM standard test method:
• e.g. CBR = 292 / ( DCP1.12 )
Mr
Source: www.GCTS.com
Source: Buchanan
Source: www.GCTS.com
Source: Buchanan
Source: FHWA
Define stress conditions at appropriate analysis depth to
determine resilient modulus for use in design.
Source: FHWA
• Falling Weight Deflectometer (FWD)*
Source: Cornell Local Roads Program
Source: Controls Group website
Falling Weight Deflectometer (FWD)
Heavy Weight Deflectometer (FWD)
64
You can solve for (backcalculate): • Pavement Layer Moduli
FWD è Backcalculated Pavement Layer Properties
Backcalculation is an Iterative Process:
Source: Lytton
k-value = spring constant
Reaction
k (psi/in) = unit load on plate / plate deflection
68
See ACPA Static (aka Effective or Composite) K-Value Calculator at http://apps.acpa.org/applibrary/KValue/
() = [( × ) + (× ) + (× )]
keffective
keffective calculation is not quite this simple…but you get the idea!
CBR % 2 - 80
k-Value psi/in 75 - 300
Equation Origin Limitations
Only for fine-grained non- expansive soils with a soaked
CBR of 10 or less.
Mr = 2555 x CBR0.64 AASHTO M-E Design A fair conversion over a wide range of values.
See http://www.apps.acpa.org/apps/MRSG.aspx app library for Mr & CBR correlation
Also a correlation for k-value and CBR:
MR vs CBR
CBR
Mr
Chart2
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1
1.5
1.5
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19.5
19.5
20
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– Strength
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Depth of Stabilization
Encountering Special Circumstances…
• Expansive Soils: – Frost Heave – High Plasticity Soils (PI >20 to 25)
77
Pavements On Expansive Soils Soil Heave from an expansive clay subgrade in this neighborhood resulted in a lawsuit between the homeowners and the homebuilder.
78
• Soil Treatment with Cement, Lime, or Fly Ash
• Geosynthetics: Geotextiles or Geogrids
• Drains or Barriers to Collect or Inhibit Moisture Infiltration
• Chemical Injection of Soil
• Material Availability and Cost
80
Don’t Forget…
• Mitigation Techniques: – May Need to be Combined, and – May Not Completely Solve the Problem!
Treatment of Upper Native Soil
Water Native Expansive Soil (High PI)
81
• There is a difference between Stabilization (sometimes referred to as Modification) and Treatment.
• Additional laboratory testing and construction verification are required for Stabilization (or Modification).
• Determining the correct Unconfined Compressive Strength (UCS) value for stabilization is key (UCS of 150 – 300 psi at 7 days and lab moisture cured is common).
• See Portland Cement Association or National Lime Association (Mixture Design) for more info.
82
• Lime-Fly Ash or Self-Cementing Fly-Ash Stabilization – Typically Used with High Silt, Low Clay Soils
• Recycled and Waste Product Stabilization • Example: Cement Kiln Dust (CKD)
• Deep Layer Subgrade Stabilization (Max 16”)
83
Fly Ash Soil Stabilization
• Chemical Stabilizers – ROADBOND EN 1™
– EMC SQUARED® System
– FA = Chemical Stabilization
87
Subgrade
Stabilized
Pulverize, Shape, Add Cement, Mix In Place, Compact, and Surface
89
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
1- Rammers
Increasing compaction energy Lower OWC and Higher Dry Density
In the field: increasing compaction energy = increasing number of passes or
reducing lift depthIn the lab: increasing compaction energy =
increasing number of blows/weight
92
• Compact granular materials near or even below optimum moisture. • Density 95% or above of standard proctor or
• Density 98% or above of modified proctor
• Compact plastic soils at or slightly above optimum moisture: • BUT do not exceed about 3% above opt.
• Density 95% or above of standard proctor
106
103
94
97
100
109
Max. Density
Opt. Moisture
D en
si ty
, l b/
93
During construction of pavement layers, there is usually a requirement to achieve a specified dry unit weight.
Moisture content
D ry
u ni
(a) > 98% of maximum dry unit weight, no moisture criteria
(b) >95% of maximum dry unit weight and moisture within ±2% of mopt
Accept
Reject
94
• Stump holes
Nuclear Density Testing
In-Situ Moisture and Density of Soils & Base – Nuclear Methods
• ASTM D6938 - Standard Test Method for In-Place Density and Water Content of Soil and Soil- Aggregate by Nuclear Methods (Shallow Depth)
• AASHTO T 310 - In-Place Density and Moisture Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
98
Source: utest.com.tr
– Free Tutorials
– Regulatory Requirements
• Compact with proper moisture content.
• Check density with testing or proof rolling.
• Fine grading.
• Consider subgrade stabilization when extremely poor soils are encountered.
• Insure adequate surface drainage.
• Uniformity is the key!
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
104
Longitudinal joint
Tie Bar Eroded Subbase
Erosion
Water
Load
107
110
Pumping and Joint Faulting
For control of pumping/faulting: • Short slabs • Proper jointing design • Good load transfer • Good surface drainage • Use a non-erodible subbase
111
Potential for Erosion and Lifting
112
When is a Subbase Needed?
• Subbases Have Little Influence on Required Concrete Pavement Thickness, but do Affect Erosion and Faulting.
• What Conditions Need to Exist for Subbase Use?
– Heavy Loading (i.e. Trucks; ADTT > 100 to 200)
– Subgrade Susceptible to Pumping/Erosion (fine-grained)
– Water Available to Subgrade (infiltration or high water table)
– Risk of Deep Frost Penetration & Heave
– Project Phasing and/or Need for Construction Platform
113
• If Conditions Exists, What Kind of Subbase?
– Granular (Crushed Stone)
• Project Conditions Will Dictate…
• If Conditions Exists, Are There Other Options?
– Subgrade Stabilization
– Soil Mixing
– Subsurface Drainage
• Various Methods to Characterize – Classification
– Strength
– Stabilization
NRMCA Resources
Pave Ahead™ Design Center • Design and Jointing recommendations and reviews for FREE • Cost comparisons including life cycle costs • Specification review • Ready mixed products:
– Conventional concrete (full depth and overlays) – Pervious concrete – Roller compacted concrete – Cement slurry for full depth reclamation (FDR)
123
124
www.paveahead.com/education
– Each Thursday beginning at 2:00 pm EDT
– April 02 Designing Concrete Parking Lots and Streets
– April 09 Designing Concrete Industrial Pavements
– April 16 Soils 101: What to Know for a Successful Paving Project
– April 23 Concrete Pavement Jointing and Details
– April 30 Materials and Construction Specifications for Concrete Pavement Projects
– May 07 Concrete Street and Parking Lot Maintenance and Repair
– May 14 Concrete Overlays of Existing Asphalt Surfaced Streets and Parking Lots
– May 21 Concrete Trail Design
• Concrete Buildings Webinar Series: buildwithstrength.com/education/
– Each Wednesday beginning at 2:00 pm EDT
Recordings available for previous webinars!
– Each Thursday beginning at 2:00 pm EDT
– May 28 Designing Pervious Concrete
– June 4 Specifying Pervious Concrete
– June 11 Installing Pervious Concrete
– June 18 Maintenance Guidelines for Pervious Concrete
• Portland Cement Association Webinar Series: www.cement.org/learn/education
– Each Wednesday beginning at 9:00 am EDT
– April 22 Full-Depth Reclamation with Cement
– April 29 Lightweight Cellular Concrete for Geotechnical Applications
– May 6 Roller-Compacted Concrete Pavements
– May 13 Cement Stabilized Subgrade Soils
– May 20 Cement-Based Water Resource Applications
Pervious Concrete Webinar Series!
(210) 508-4923 [email protected]
(267) 212-4700 [email protected]
Presented By: National Ready Mixed Concrete Association
2
National Ready Mixed Concrete Association
• National Trade Association – Established in 1930 • HQ in Alexandria, VA • 1,400+ Member Companies • NRMCA Represents ~75% of North American Ready Mixed Production • Mission - Serve Industry and Partners Through:
• Compliance and Operations • Engineering • Government Affairs • Local Paving: Pave Ahead™ Initiative (PaveAhead.com)
• Structures and Sustainability: Build With Strength™ Initiative
Interested in becoming a member, visit: www.nrmca.org/membership/
Your Instructors Today…
• Brian Killingsworth, P.E. – NRMCA Local Paving, Division Head – 28 Years in Practice – Pavement Design, Materials, Construction, Forensics
• Luke McHugh, P.E. – NRMCA Local Paving, Northeast Region – 33 Years in Practice – Civil Design – Aviation Emphasis
More information at paveahead.com/experts/
5
NRMCA Disclaimer
• This presentation has been prepared solely for information purposes. It is intended solely for the use of professional personnel, competent to evaluate the significance and limitations of its content, and who will accept full responsibility for the application of the material it contains. The National Ready Mixed Concrete Association and any other organizations cooperating in the preparation of this presentation strive for accuracy but disclaim any and all responsibility for application of the stated principles or for the accuracy of the content or sources and shall not be liable for any loss or damage arising from reliance on or use of any content or principles contained in this presentation.
• Unless otherwise indicated, all materials in this presentation are copyrighted to the National Ready Mixed Concrete Association. All rights reserved. Therefore reproduction, modification or retransmission in any form is strictly prohibited without the prior written permission of the National Ready Mixed Concrete Association.
• ©2015 National Ready Mixed Concrete Association.
6
Instructions • Everyone is muted. • Webinar is being recorded and posted at paveahead.com/education/. • Type questions in the question box. • Download the handouts in the GoToWebinar control panel. • Credit for course:
– Based on attendance. – Survey (Quiz) – In follow-up e-mail, not required, but encouraged. – Attendance Certificate – In follow-up e-mail 1 hour after webinar. – AIA members – Attendance registered with AIA-CES if AIA number provided.
• AIA-CES Course SOIL101: 1.5 LU|Elective & 1.5 PDH for Engineers
• Learning Objectives:
– Recognize how a soil sampling and testing plan is developed for a paving project.
– Comprehend a geotechnical engineering report.
– Learn the various ways soil strength can be determined for use in pavement design.
– Understand the importance of the soil moisture-density relationship in construction.
8
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Structure – Surface course – Base course – Subbase course – Subgrade
11
Subgrade stresses differ considerably.
Strength.
12
+++ (Tensile Stress)
++ (Tensile Stress)
Transverse Cracking Joint Faulting
14
Longitudinal Joint
Transverse Joint
Subgrade Subbase
Surface Texture
Concrete Materials
Tie bars
Concrete Pavement Design
• Thickness is a Function of Key Parameters: – Design life – Traffic loads & frequencies – Concrete strength – Subgrade/subbase support (strength characterization)
• Jointing & Reinforcement: – Load transfer considerations – Prevention of uncontrolled cracking
• Other Design Considerations: – Reliability (Factor of Safety) – Grades & drainage – Edge support conditions (e.g. curb & gutter, shoulder…) – Pavement/subsurface interaction
Source: PavementInteractive.org
How Do We Evaluate The Suitability of Subgrade Soils?
Geotechnical Engineering Study and Report • Classification (Gradation, Atterberg Limits, etc.) • Depth to Bedrock • Depth to Water Table • Potential for Compaction • Presence of Weak or Soft Layers or Organics • Susceptibility to Frost Action or Excessive Swell • Soil Strength Characteristics – Critical Parameter For Pavement Design
19
Stay Tuned, More Details To Come…
20
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
Data Collection Activities - Drilling
• Geotechnical Drilling (New Pavements) – Minimum 5 feet below final top of subgrade elevation** – Spacing a function of roadway type and soil conditions – High plasticity soils: increase drilling depth to 10 to 15 feet – Strength testing must be representative of subgrade soil supporting pavement materials – May require larger augers at some boring locations for material collection
• Geotechnical Drilling (Existing Pavements) – Obtain existing pavement thicknesses – Consider test pits if full depth reclamation is possible – Spacing as stated above – Drilling depths as stated above – Materials for soil strength as stated above
**Airport, Industrial, and Port Facilities may be different!
23
• Standard Penetration Test (SPT) blows/ft • Material Descriptions • Moisture and Water Table Depth (if encountered)
• Bedrock Depth (if encountered)
– Density – % Swell (freeze and/or moisture related) – Subgrade Strength Characterization
25
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Coarse or Fine Grained • Typically Classified as:
– Gravel – Sand – Silt – Clay (Lean or Fat: Based on Plasticity*) – Or a combination of any of the above
• e.g. Sandy Gravel With Clay *Soil plasticity refers to the manner in which water interacts with the soil particles.
27
States of Consistency for Cohesive Soils (Soil Passing #40 Sieve)
28
Atterberg Limits
• Liquid Limit (LL) • Plastic Limit (PL) • Plasticity Index (PI) • PI = LL - PL
Albert Atterberg 1846-1916
29
• AASHTO Classification System – (AASHTO M 145)
30
Source: ASTM D 3282
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Water Effect – Capillary Forces
36
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
10 11 12 13 14 15 16 17 18 19 20 21 22 23
gdry max
Chart1
12
14
16
18
20
22
103.9
107.6
109.4
108.8
106
103
Sheet1
wc
gamma
12
103.9
14
107.6
16
109.4
18
108.8
20
106
22
103
Volume of Proctor Mold (ft3) 1/30 1/30 1/30 1/30 1/30 1/30
Weight of wet soil in the mold (lb) 3.88 4.09 4.23 4.28 4.24 4.19
Water Content (%) 12 14 16 18 20 22
Wet Unit Weight (lb/ft3) 116.4 122.7 126.9 128.4 127.2 125.7
Dry Unit Weight (lb/ft3) 103.9 107.6 109.4 108.8 106.0 103.0
Sheet2
Sheet3
37
Soil Compaction
• Soil compaction is the process of “artificially” increasing the density (unit weight) of a soil by compaction (by application of rolling, tamping, or vibration).
• Moisture-density testing as practiced today was started by R.R. Proctor in 1933. – His method became known as the “standard Proctor” test.
Ralph Roscoe Proctor, PE (1894 -1962)
38
Moisture and Density Relationships of Soils & Base – Laboratory Methods
• ASTM D 698 - Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12,400 ft-lbs/ft3)
• ASTM D 1557 - Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbs/ft3)
• AASHTO T 99 - Moisture-Density Relations of Soils Using a 5.5-lb Rammer and a 12-in. Drop • AASHTO T 180 - Moisture-Density Relations of Soils Using a 10-lb Rammer and a 18-in. Drop
39
Soil Strength is usually greatest at its maximum dry density.
40
Total Compaction Energy Affects Maximum Dry Density and Optimum Moisture
Typical Compaction Curves
• Compaction Increases Soil Strength
• Compaction Achieves Soil Support Uniformity
• Provides Stable Platform for Pavement Layers *To Optimum or Just Above the Optimum Moisture Content
Source: Equipment World
42
Soil Compaction in the Lab: 1- Standard Proctor Test 2- Modified Proctor Test
Standard Proctor Test Modified Proctor Test
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Compaction Curve
Wet to Optimum
Dry to Optimum
Soil Compaction in the Lab: 1- Standard Proctor Test 2- Modified Proctor Test
wc1 wc2 wc3 wc4 wc5 gd1 gd2 gd3 gd4 gd5
4 inch diameter compaction mold. (V = 1/30 of a cubic foot)
W = 5.5 or 10 pound hammer
25 blows per layer
Increasing Water Content
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Some Strength Parameters Require Complex & Expensive Testing Devices.
• Some Strength Parameters Cannot Be Determined in the Laboratory.
46
(Not Commonly Used)
(More Commonly Used)
– California Bearing Ratio (CBR) • Measures shearing resistance • Units: percent • Typical values: 0 to 20 for soils
– Resilient Modulus (MR) • Measures stress-strain relationship (an engineering property)
• Units: psi or MPa • Typical values: 3,000 to 15,000 psi for soils
– K-value (k) **Typically required for concrete pavement design**
• Measures resistance to deflection • Units: psi/in • Typical Values: 75 - 200 psi/in for soils
Source: FHWA
• Resistance of the material to uniaxial penetration.
• Measure of soil shear strength relative to standard crushed stone.
• Field and laboratory test.
– An empirical test.
Source: www.dur.ac.uk/
Source: www.matest.com
ASTM D1883-Standard Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils
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California Bearing Ratio (CBR)
• Load a piston (area = 3 in2) at a constant rate (0.05 in/min)
• Record load every 0.1 inch penetration
• Total penetration not to exceed 0.5 inch
• Draw load-penetration curve
0
100
200
300
400
500
600
700
Moisture Content
C B
R
Use relevant or saturated value for moisture content when assessing soils under laboratory conditions.
Chart3
0.043
0.116
0.179
0.217
0.259
0.4
0.5
Typical Testing Machine Source: Humboldt
Surcharge Weights
• Simulate the weight of pavement.
• Prevent heaving up around the piston.
54
55
Dynamic Cone Penetrometer (DCP)
• Originally developed in the Republic of South Africa (RSA) where it has been used with related tools and analyses for over 25 years.
• Equipment can be purchased for about $1,000 to $3,000 (US).
56
• Standard Test Method:
– ASTM D6951-Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications
– Equipment can come with different hammer weights:
• 8 kg (17.6 lb.)
• 4.6 kg (10.1 lb.)
– USACE CBR—DCP correlations in the ASTM standard test method:
• e.g. CBR = 292 / ( DCP1.12 )
Mr
Source: www.GCTS.com
Source: Buchanan
Source: www.GCTS.com
Source: Buchanan
Source: FHWA
Define stress conditions at appropriate analysis depth to
determine resilient modulus for use in design.
Source: FHWA
• Falling Weight Deflectometer (FWD)*
Source: Cornell Local Roads Program
Source: Controls Group website
Falling Weight Deflectometer (FWD)
Heavy Weight Deflectometer (FWD)
64
You can solve for (backcalculate): • Pavement Layer Moduli
FWD è Backcalculated Pavement Layer Properties
Backcalculation is an Iterative Process:
Source: Lytton
k-value = spring constant
Reaction
k (psi/in) = unit load on plate / plate deflection
68
See ACPA Static (aka Effective or Composite) K-Value Calculator at http://apps.acpa.org/applibrary/KValue/
() = [( × ) + (× ) + (× )]
keffective
keffective calculation is not quite this simple…but you get the idea!
CBR % 2 - 80
k-Value psi/in 75 - 300
Equation Origin Limitations
Only for fine-grained non- expansive soils with a soaked
CBR of 10 or less.
Mr = 2555 x CBR0.64 AASHTO M-E Design A fair conversion over a wide range of values.
See http://www.apps.acpa.org/apps/MRSG.aspx app library for Mr & CBR correlation
Also a correlation for k-value and CBR:
MR vs CBR
CBR
Mr
Chart2
1
1
1.5
1.5
2
2
2.5
2.5
3
3
3.5
3.5
4
4
4.5
4.5
5
5
5.5
5.5
6
6
6.5
6.5
7
7
7.5
7.5
8
8
8.5
8.5
9
9
9.5
9.5
10
10
10.5
10.5
11
11
11.5
11.5
12
12
12.5
12.5
13
13
13.5
13.5
14
14
14.5
14.5
15
15
15.5
15.5
16
16
16.5
16.5
17
17
17.5
17.5
18
18
18.5
18.5
19
19
19.5
19.5
20
20
– Strength
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
• Depth of Stabilization
Encountering Special Circumstances…
• Expansive Soils: – Frost Heave – High Plasticity Soils (PI >20 to 25)
77
Pavements On Expansive Soils Soil Heave from an expansive clay subgrade in this neighborhood resulted in a lawsuit between the homeowners and the homebuilder.
78
• Soil Treatment with Cement, Lime, or Fly Ash
• Geosynthetics: Geotextiles or Geogrids
• Drains or Barriers to Collect or Inhibit Moisture Infiltration
• Chemical Injection of Soil
• Material Availability and Cost
80
Don’t Forget…
• Mitigation Techniques: – May Need to be Combined, and – May Not Completely Solve the Problem!
Treatment of Upper Native Soil
Water Native Expansive Soil (High PI)
81
• There is a difference between Stabilization (sometimes referred to as Modification) and Treatment.
• Additional laboratory testing and construction verification are required for Stabilization (or Modification).
• Determining the correct Unconfined Compressive Strength (UCS) value for stabilization is key (UCS of 150 – 300 psi at 7 days and lab moisture cured is common).
• See Portland Cement Association or National Lime Association (Mixture Design) for more info.
82
• Lime-Fly Ash or Self-Cementing Fly-Ash Stabilization – Typically Used with High Silt, Low Clay Soils
• Recycled and Waste Product Stabilization • Example: Cement Kiln Dust (CKD)
• Deep Layer Subgrade Stabilization (Max 16”)
83
Fly Ash Soil Stabilization
• Chemical Stabilizers – ROADBOND EN 1™
– EMC SQUARED® System
– FA = Chemical Stabilization
87
Subgrade
Stabilized
Pulverize, Shape, Add Cement, Mix In Place, Compact, and Surface
89
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
1- Rammers
Increasing compaction energy Lower OWC and Higher Dry Density
In the field: increasing compaction energy = increasing number of passes or
reducing lift depthIn the lab: increasing compaction energy =
increasing number of blows/weight
92
• Compact granular materials near or even below optimum moisture. • Density 95% or above of standard proctor or
• Density 98% or above of modified proctor
• Compact plastic soils at or slightly above optimum moisture: • BUT do not exceed about 3% above opt.
• Density 95% or above of standard proctor
106
103
94
97
100
109
Max. Density
Opt. Moisture
D en
si ty
, l b/
93
During construction of pavement layers, there is usually a requirement to achieve a specified dry unit weight.
Moisture content
D ry
u ni
(a) > 98% of maximum dry unit weight, no moisture criteria
(b) >95% of maximum dry unit weight and moisture within ±2% of mopt
Accept
Reject
94
• Stump holes
Nuclear Density Testing
In-Situ Moisture and Density of Soils & Base – Nuclear Methods
• ASTM D6938 - Standard Test Method for In-Place Density and Water Content of Soil and Soil- Aggregate by Nuclear Methods (Shallow Depth)
• AASHTO T 310 - In-Place Density and Moisture Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth)
98
Source: utest.com.tr
– Free Tutorials
– Regulatory Requirements
• Compact with proper moisture content.
• Check density with testing or proof rolling.
• Fine grading.
• Consider subgrade stabilization when extremely poor soils are encountered.
• Insure adequate surface drainage.
• Uniformity is the key!
– ASTM – AASHTO
– Laboratory Methods – In-Situ Methods
• Field Compaction of Soils • Bases and Subbases
Source: www.cement.org
104
Longitudinal joint
Tie Bar Eroded Subbase
Erosion
Water
Load
107
110
Pumping and Joint Faulting
For control of pumping/faulting: • Short slabs • Proper jointing design • Good load transfer • Good surface drainage • Use a non-erodible subbase
111
Potential for Erosion and Lifting
112
When is a Subbase Needed?
• Subbases Have Little Influence on Required Concrete Pavement Thickness, but do Affect Erosion and Faulting.
• What Conditions Need to Exist for Subbase Use?
– Heavy Loading (i.e. Trucks; ADTT > 100 to 200)
– Subgrade Susceptible to Pumping/Erosion (fine-grained)
– Water Available to Subgrade (infiltration or high water table)
– Risk of Deep Frost Penetration & Heave
– Project Phasing and/or Need for Construction Platform
113
• If Conditions Exists, What Kind of Subbase?
– Granular (Crushed Stone)
• Project Conditions Will Dictate…
• If Conditions Exists, Are There Other Options?
– Subgrade Stabilization
– Soil Mixing
– Subsurface Drainage
• Various Methods to Characterize – Classification
– Strength
– Stabilization
NRMCA Resources
Pave Ahead™ Design Center • Design and Jointing recommendations and reviews for FREE • Cost comparisons including life cycle costs • Specification review • Ready mixed products:
– Conventional concrete (full depth and overlays) – Pervious concrete – Roller compacted concrete – Cement slurry for full depth reclamation (FDR)
123
124
www.paveahead.com/education
– Each Thursday beginning at 2:00 pm EDT
– April 02 Designing Concrete Parking Lots and Streets
– April 09 Designing Concrete Industrial Pavements
– April 16 Soils 101: What to Know for a Successful Paving Project
– April 23 Concrete Pavement Jointing and Details
– April 30 Materials and Construction Specifications for Concrete Pavement Projects
– May 07 Concrete Street and Parking Lot Maintenance and Repair
– May 14 Concrete Overlays of Existing Asphalt Surfaced Streets and Parking Lots
– May 21 Concrete Trail Design
• Concrete Buildings Webinar Series: buildwithstrength.com/education/
– Each Wednesday beginning at 2:00 pm EDT
Recordings available for previous webinars!
– Each Thursday beginning at 2:00 pm EDT
– May 28 Designing Pervious Concrete
– June 4 Specifying Pervious Concrete
– June 11 Installing Pervious Concrete
– June 18 Maintenance Guidelines for Pervious Concrete
• Portland Cement Association Webinar Series: www.cement.org/learn/education
– Each Wednesday beginning at 9:00 am EDT
– April 22 Full-Depth Reclamation with Cement
– April 29 Lightweight Cellular Concrete for Geotechnical Applications
– May 6 Roller-Compacted Concrete Pavements
– May 13 Cement Stabilized Subgrade Soils
– May 20 Cement-Based Water Resource Applications
Pervious Concrete Webinar Series!
(210) 508-4923 [email protected]
(267) 212-4700 [email protected]