Light Weight Deflectometer, Principles and Versability Content: 1. - - PowerPoint PPT Presentation

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Light Weight Deflectometer, Principles and Versability Content: 1. - - PowerPoint PPT Presentation

Aug 17, 2023 586 likes •898 views

1 Light Weight Deflectometer, Principles and Versability Content: 1. Introduction 2. Dynatest 3031 LWD 3. Field measurements 4. Conclusions NVF/BRA Symposium Oslo Feb. 13 and 14, 2008: Helge Mork, Light weight deflectometer (LWD) 2

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Content: 1. Introduction 2. Dynatest 3031 LWD 3. Field measurements 4. Conclusions

NVF/BRA Symposium Oslo Feb. 13 and 14, 2008: Helge Mork, Light weight deflectometer (LWD)

Light Weight Deflectometer, Principles and Versability

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Light Weight Deflectometer

  • Introduction

– Field testing equipment for determination of stiffness of pavement materials – Easy to operate, and small enough to be used at any place (especially construction sites) – Lower initial cost than an

  • rdinary FWD ( 1/10)

FV 873-01 km 3,01

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Light Weight Deflectometer

  • Basic principles

– Measurement of deflections induced by dropping weight (up to 20 kg – hence light weight) using geophones.

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Light Weight Deflectometer

  • LWD equipments on the market

– Dynatest LWD – Prima 100, CarlBro (previously Phoenix) – Light Drop Weight (LDW), Germany – Loadman, Finland

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Light Weight Deflectometer

Dynatest 3031 LWD

  • It has a basic 10 kg falling mass (+5kg)
  • During the test, the falling mass impacts the

plate, producing a load pulse up to 15 kN of 15 – 25 ms duration.

  • The center geophone sensor measures the

deflection caused by the mass impact on the loading plate. (+2 more geophones optional)

  • The diameter of the loading plate can easily be

varied between 150 and 300 mm

  • The software associated with the equipment is

LWDmod, which uses the same principle as ELmod for Dynatest FWD.

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Light Weight Deflectometer

Dynatest 3031 LWD

  • the surface deflection modulus E0 is calculated

using Boussinesq solution as follows: where:

  • E0 : Surface deflection modulus
  • f : Factor for stress distribution (2 or /2)
  • : Poisson’s ratio
  • 0 : Uniformily distributed stress under plate
  • : Radius of plate
  • d0 : Center deflection

2

*(1 )* * f a E d

  • a

* 3 2 a E d

  • 2

a P

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Light Weight Deflectometer

Dynatest 3031 LWD

  • For multi-layer systems, Odemark’s

method of equivalent thickness (MET) is used in LWDmod for backcalculation of modulus values

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LWDmod analysis

  • Analysis

starts by filtering out unrealistic drops

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LWDmod analysis

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Field measurements

  • Objective

– To compare modulus values of pavement materials determined from field measurements carried out with Light Weight Deflectometer (LWD), Falling Weight Deflectometer (FWD), Dynamic Cone Penetrometer (DCP) and Static Plate Loading Test (SPLT). – Evaluate whether LWD could be used for evaluation of low volume roads

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Measurements in the Malvik area

Pilot test locations

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Malvik low volume test roads

Bitumen stabilized gravel road (Herjuan) E0=126 MPa Gravel road E0=192 MPa AC road (Bostad) E0=166 MPa

250 mm, E1 400 mm, E2 E3 120 mm, E1 AC 750 mm, E2 E3 40 mm, Stabilized gravel 460 mm E2 500mm E1

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Malvik test roads

  • Test point arrangement at each of two sections

10m 10m 10m 10m 10m 5m 5m Lane A Lane B C L 7 6 5 4 3 2 1

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Light Weight Deflectometer

LWD, FWD and DCP used for pilot study at Malvik

LWD DCP FWD

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LWD/DCP set-up

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LWDmod data analyses

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LWDmod data analyses

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LWD data analyses

  • Comparison of surface modulus

values of the three roads

Road KV-12 FV 873-01 km 3,0 – km 3,6 FV 873-01 km 7,1 – km 7,7 Surfacing Gravel Asphalt Concrete Bitumen Stabilized Base/Subbase Natural gravel Sandy gravel Silty gravel Surface Modulus E0 (MPa) 192 166 126

2

2*(1 )* *a E d

  • NB: The rating of these values agree with the visual condition evaluation
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DCP data

  • A typical DCP plot.

DCP value [mm/blow] 0.6 2.4 6

Field CBR

703.6 124.4 39.6 E (MPa) 755.1 300.6 163.5

E = 537.76*DCP-0.6645 Dang-Fong Lin 2006

DCP and E

1 2 3 4 5 6 7 8 100 200 300 400 500 600 700 800 900

Dybde (mm) DCP (med mer/slag)

0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0 1600.0

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20 Comparison of results -gravel

  • 1. Gravel Road KV-12

250 mm, E1 400 mm, E2 E3

KV-12 E1

y = 0.4154x + 194.2 R2 = 0.4951 y = 0.5346x + 302.88 R2 = 0.3 200 300 400 500 600 700 800 200 300 400 500 600 700 800 LWD Modulus KV-12 E1 DCP Modulus Linear (KV-12 E1) Linear (DCP Modulus)

KV-12 E2

y = 0.5788x + 22.367 R2 = 0.4694

y = 2.6108x + 130.41 R

2 = 0.5112

50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350 400 450 500 LWD Modulus FWD Modulus DCP Modulus Linear (FWD Modulus) Linear (DCP Modulus)

KV-12 E3

y = 0.0692x + 24.178 R2 = 0.0296

20 40 60 80 100 120 140 160 180 200

20 40 60 80 100 120 140 160 180 200

LWD Modulus

FWD Modulus DCP Modulus Linear (FWD Modulus)

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21 Comparison of results -gravel

  • 1. Gravel Road KV-12

250 mm, E1 400 mm, E2 E3

KV-12 E1

y = 0.4154x + 194.2 R2 = 0.4951 y = 0.5346x + 302.88 R2 = 0.3 200 300 400 500 600 700 800 200 300 400 500 600 700 800 LWD Modulus KV-12 E1 DCP Modulus Linear (KV-12 E1) Linear (DCP Modulus)

KV-12

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.00 200.00 400.00 600.00 800.00 1000.00 1200.00 LWD E1 LWD E1 FWD E1 FWD E1

<

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Comparison of results -AC

  • 2. AC Road: FV 873 km 3-3.6 (Bostad)

120 mm, E1 AC 750 mm, E2 E3

Bostad E1

y = 1.3231x - 756.99 R2 = 0.71

500 1000 1500 2000 2500 3000 3500 4000 500 1000 1500 2000 2500 3000 3500 4000

LWD M odulus (E1) FWD Modulus (E1)

Bostad E2 y = -0.0816x + 47.982 R2 = 0.1017 y = 0.6731x + 63.577 R2 = 0.1978

20 40 60 80 100 120 140 160 180 200 20 40 60 80 100 120 140 160 180 200 LWD Modulus (E2) FWD Modulus DCP Modulus Linear (FWD Modulus) Linear (DCP Modulus)

Bostad E3

y = 0.134x + 13.24 R2 = 0.1566

y = 0.0277x + 45.609 R2 = 0.0003 10 20 30 40 50 60 70 10 20 30 40 50 60 70 LWD Modulus (E3) FWD Modulus DCP Modulus Linear (FWD Modulus) Linear (DCP Modulus)

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Comparison of results -AC

  • 2. AC Road: FV 873 km 3-3.6 (Bostad)

120 mm, E1 AC 750 mm, E2 E3

Bostad E1

y = 1.3231x - 756.99 R2 = 0.71

500 1000 1500 2000 2500 3000 3500 4000 500 1000 1500 2000 2500 3000 3500 4000

LWD M odulus (E1) FWD Modulus (E1)

FV873 3-3.6 Bostad

0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007 0.0008 0.0009 0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00 7000.00 LWD E1 LWD E1 FWD E1 FWD E1

<

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Comparison of results -stabilized

  • 3. Stabilized Road: FV 873 km 7.1-7.7 (Herjuan)

40 mm, Stabilized gravel 460 mm E2 500mm E1

Herjuan E1

y = 0.1219x + 128.79 R2 = 0.2898

y = 0.2887x + 167.81 R2 = 0.8801 100 200 300 400 500 600 700

100 200 300 400 500 600 700 LWD Modulus

FWD Modulus DCP Modulus Linear (FWD Modulus) Linear (DCP Modulus)

Herjuan E2

y = 0.3676x + 17.593 R2 = 0.1634

y = -0.0163x + 68.572 R2 = 6E-05 10 20 30 40 50 60 70 80 90 100 110 10 20 30 40 50 60 70 80 90 100 110 LWD Modulus FWD Modulus DCP Modulus Linear (FWD Modulus) Linear (DCP Modulus)

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Comparison of results

  • 3. Stabilized Road: FV 873 km 7.1-7.7 (Herjuan)

40 mm, Stabilized gravel 460 mm E2 500mm E1

Herjuan E2

y = 0.3676x + 17.593 R2 = 0.1634

y = -0.0163x + 68.572 R2 = 6E-05 10 20 30 40 50 60 70 80 90 100 110 10 20 30 40 50 60 70 80 90 100 110 LWD Modulus FWD Modulus DCP Modulus Linear (FWD Modulus) Linear (DCP Modulus)

FV873 7.1-7.6 Herjuan

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.00 50.00 100.00 150.00 200.00 LWD E2 LWD E2 FWD E2 FWD E2 <

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LWD SPLT DCP

SPLT, DCP and LWD at E6 Steinkjer

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27 Comparison of results -subgrade

y = 0.2405x + 41.464 R2 = 0.6043 y = 0.706x + 74.532 R

2 = 0.5773

20 40 60 80 100 120 140 160 20 40 60 80 100 120 140 160 LWD Modulus SPLT Modulus* DCP Modulus Linear (SPLT Modulus*) Linear (DCP Modulus)

Results of tests on clay subgrade at E6 construction site, Steinkjer, May 14 2007

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.00 50.00 100.00 150.00 200.00 250.00 LWD SPLT DCP

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Summary and conclusions

  • Observations from the field testing

– Stability problems encountered when testing with the smaller plate

  • Preliminary conclusions:

– With this exception, generally good practical experiences with the equipment – Surface modulus evaluation comply with overall visual condition – LWD modulus and SPLT stiffness seem to be comparable – Backcalculated results from LWDmod for layered structures using one defl. sensor are questionable – No correlation found between LWD moduli and DCP values – Probably, the load is too low to give a certain determination of subgrade stiffness when performing surface measurements for layered structures – There is a relatively wider scatter of LWD modulus values than for moduli backcalculated from FWD measurements

  • There are no significant connections found between the LWD and FWD moduli for subgrade

materials, and a very poor link for subbase layers

– Generally the LWD modulus values tend to be a bit higher than the FWD modulus values, in contradiction with other tests reported elsewhere. The explanation could be:

  • This test is conducted on in-service roads while the others are prototype tests in a laboratory.
  • LWDmod is more realistic up to two layer structures, for three or more layers the results are

sensitive to the seed values used.

  • The obtained results can not be used for application due to a limited number of test points
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Thank you!

Questions?