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8/8/2019 The Dynamic Cone Penetrometer the DCP
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The Dynamic Cone Penetrometer “The DCP”
What is it, how does it work, and how
can it help you?
Gavin P. Gautreau, P.E.Geotechnical Research ManagerLouisiana Transportation Research Center (LTRC)
8/8/2019 The Dynamic Cone Penetrometer the DCP
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• What is it?
– Purpose & Concept
– Parts• How does it work?
– Operation/Technique
– Data Recording/Analysis• How can it help you?
– Layer Stiffness
– Layer Thickness – Acceptance & Verification
– Forensics
– Correlations (CBR, Mr, etc.)
Presentation Objectives:
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• Purpose & Concept
– Dynamic Cone Penetrometer
– Shallow Pavement Applications – Measures Stiffness, mm/blow
– Simple Concept
• Like hammering a nail
• Stiff material requires more drops
• Weak material requires fewer drops
– Non Nuclear
– Possible Method for Acceptance
– Quick and Cost Effective
– Another “Tool for the Toolbox”
What is it?
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• Parts – Handle
– Upper Rod (5/8” dia) – Hammer
• 17.8 pounds (8kg)
• 22.6 inch drop
– Anvil & Lower Rod
– Cone Tip (60 degree, ¾” dia)
– Measuring Rod with cm & mm divs.
– Other
• Hammer Drill
• Generator
• Farm Jack
What is it?
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(A)(B)
How does it work?
• Operation
– Assemble DCP
– Drill thru Asphalt or Concrete ifnecessary
– Record reference readings (A)
• Rod remains stationary
– Lift hammer to handle
– Release hammer
– Record rod reading after each
hammer drop (B) – Repeat drop, read, and record
process thru pavement layers
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(A)(B)
How does it work?
• Technique
– Keep straight (vertical)
– Avoid banging hammerinto handle during lift.
• Can lose disposable cone
• Damage to device – Spin rod after each blow.
– Keep measuring rod inone spot during test.
– Record reading afterevery hammer drop.
(X)
(Y)
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How does it work?
• Operation (Prep & Planning)
– Hammer Drill
• Quickly thru Asphalt or Concrete
• Minimal Intrusion
• Various Length bits
• Dry vs wet coring rig
– Crew Size• Hammer Operator
• Reader
• Recorder
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How does it work?
• Data Recording
– Project Information
• Site Location
• Station #
• Distance from Centerline
• Elevation (if available)
– Pavement Information (as available)• Cross-Section Thickness Information
• Material Types (classification and gradation)
• Compaction Info (Proctor Moisture and Density) as available
• Nuclear Gauge Information if available
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(A) 46.0(B) 46.3
How does it work?
47.55
????
46.93
46.62
47.24
Top of Asphalt/Concrete
Top of Testing Surface
(bottom of drilled hole, if applicable)
Reading after First Blow
Reading after Second Blow
Anytown, LA – Hwy 1, Sta. 19+00 RL
NA0
46.0(A)0
RodReading
Blow#
Reading after Fourth Blow
Reading after Third Blow
Reading after Last Blow
Reading after Fifth Blow
• Data Recording, example
1 46.3(B)
,cm
Stone
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How does it work? • Data Calculations (without drilling)
46.93
46.6246.31
NA0
46.00
47.86
47.55
47.24
RodReading, cm
Blow#
0.90.90.3
0.60.60.30.30.30.3
cm
can plot as inches or elev.
cm
Running Total
cm
this timesten = DCPI
equal to tip location
below surface0.00.0
1.81.80.3
1.51.50.3
1.21.20.3
Distance below SurfaceCumulativePenetration
Distanceper Blow
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How does it work? • Data Calculations (drilling occurred)
46.93
46.6246.31
38.40
46.00
47.86
47.55
47.24
RodReading, cm
Blow#
8.50.90.3
8.20.60.37.90.30.3
cm
can plot as inches or elev.
cm
Running Total
cm
tip location
below pavement surface0.07.6Drilled depth
9.41.80.3
9.11.50.3
8.81.20.3
Distance below SurfaceCumulativePenetration
Distanceper Blow
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0
5
10
15
20
25
30
35
40
0 20 40 60 80Number of Blows
C u m u l a t i v e P e n e t r a t i o n , c m
Anytown, LA – Hwy 1, Sta. 19+00 RL
3 mm/blowLayer Change
Layer Change
36 mm/blow
11.2 mm/blow
Number of Blows
D e p t h o f P e n e t r a
t i o n , c m
• Data Analysis
– Plotting Data
– Layer Changes
– Average mm/blow
Example, cont’d
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Advantages:• Determines Stiffness in mm/blow
• Plotted slope = Stiffness in mm/blow
• Flatter Slopes indicate stiffer layers
• Steeper Slopes indicate weak layers
• Layer Changes identified by Slope Changes
• Thicknesses can be determined/verified
• Weak layers identified
• Minimal disturbance• Test lower pavement layers without removal of upper layers
• Test different materials (Stone, Sand, Clay, and Silt)
• Compare time differences or adjacent sites
Disadvantages:• Not for use on large stone, shell, asphalt, and concrete
• Damage can occur (repetitive blows in very stiff & improper removal)
• Does not measure moisture content or density – measures stiffness
D e p t h
Blow Count0
How can it help you?
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How can it help you?
• Advantages:
• Possibly another way to adjust pay, based on
Stiffness of in-place layers• Non “Nuclear”
• Not rocket science
• Correlations to CBR, Mr, etc.• Another “tool for the toolbox”… spread the word
• Simple reliable, cost-effective tool for shallowpavement applications
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• Develop a comprehensive implementation plan ofDCP with procedures that DOTD can use in its dailyproduction
• Develop or modify current DOTD specifications toaccommodate such changes.
LTRC Project: 06-4GT
Objectives:
This is a comprehensive follow-up studyafter four LTRC research projects on
involving DCP applications.
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ALF Lane 4
Base, Treated Subase, & Subgrade
Field & Laboratory Test Summary
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Cross-Section
• Asphalt Surface (2”)
• Base (8.5”) – Stone
– BCS with 10% Slag
– BCS with FlyAsh (small untreated area at end) – Foamed Asphalt
• Treated Subbase (12”) – Lime
– Cement
• Untreated Subgrade C o n s t r u c t i o n
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SUBGRADE DCP VALUES
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
20-Nov 10-Dec 30-Dec 19-Jan 8-Feb
TIME, DATE
A V E R A G E M M / B L O
1A AVERAGE
2A AVERAGE
2A 0+10
1B AVERAGE
2B AVERAGE
3A AVERAGE
3B AVERAGE
NovemberAverage =28.9
FebruaryAverage =13.6
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TREATED SUBBASE DCP VALUES
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
20-Nov 10-Dec 30-Dec 19-Jan 8-Feb
TIME, DATE
A V E R A G E M M
/ B L O
1A AVERAGE
2A AVERAGE
2A 0+10
1B AVERAGE
2B AVERAGE
3A AVERAGE
3B AVERAGE
LimeInitialAverage= 31.8
CementAverage= 5.3
CementInitialAverage= 20.3
LimeAverage= 7.3
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BASE DCP VALUES
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20-Nov 10-Dec 30-Dec 19-Jan 8-FebTIME, DATE
A V E R A G E M
M / B L O
1A AVERAGE
2A AVERAGE
2A 0+10
1B AVERAGE
2B AVERAGE
3A AVERAGE
3B AVERAGE
BASE DCP VALUES
BCS & Slag
BCS & Fly Ash
BCS (Raw)
Stone
Stone
Foamed Asphalt
Foamed Asphalt
Each point represents 3 testsper section per date.
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Thanks!
• Questions?