The Dynamic Cone Penetrometer the DCP

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)



• 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:



• 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?



• 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?



(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



(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)



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



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



(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



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



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



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



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?



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



• 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.



ALF Lane 4

Base, Treated Subase, & Subgrade

Field & Laboratory Test Summary



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



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



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



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.



Thanks!

• Questions?

The Dynamic Cone Penetrometer the DCP

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