Presentation is loading. Please wait.

Presentation is loading. Please wait.

Mark Lindemann NDOR Geotechnical Engineer.  Background on previous field testing  Research – Non-nuclear field testing  Cost Savings of Going Non-Nuclear.

Similar presentations


Presentation on theme: "Mark Lindemann NDOR Geotechnical Engineer.  Background on previous field testing  Research – Non-nuclear field testing  Cost Savings of Going Non-Nuclear."— Presentation transcript:

1 Mark Lindemann NDOR Geotechnical Engineer

2  Background on previous field testing  Research – Non-nuclear field testing  Cost Savings of Going Non-Nuclear  Fundamentals of LWD  LWD Correlation  Field Implementation

3  Volumemeasure Test Method

4  Nuclear Density & Moisture Gauge (NDG)

5  Why fix what isn’t broken?  Nuclear Gauges –  Regulations  Licensing  Storage and transport  Training  Costs add up  Have 84 gauges needing replacement  Possible Fines  Approximately $250,000/ year Falls in Line with Every Day Counts Initiative Innovative Technologies

6  University of Nebraska – Dr. Yong K. Cho  Non-Nuclear Methods for HMA and Soil Density  Historical research  Field Research: PQI (HMA)  Compare to Nuclear Density Gauge  Bulk Specific Gravity of Asphalt Cores (AASHTO T166)

7  PQI (Pavement Quality Indicator)  Measures the change in electromagnetic field as current is sent through the material.  Calibrated with average of 5 core densities and average of 5 PQI densities.

8  Results:  Both Nuclear and PQI provided results very close to asphalt core values  Nuclear gauge closer to asphalt core values (+1.07 lb/ft 3 )  PQI gauge values lb/ft 3 to asphalt core values.

9

10

11

12

13

14

15 Nuclear Results:  Average difference of 1.71 pcf compared to standard for density.  Average difference of 0.22% for moisture. EDG Results:  Average difference of 9.86 pcf compared to standard for density  Average difference of 1.66% for moisture.

16  M+DI (Moisture Density Indicator)  Uses Time Domain Reflectometry to send electromagnetic pulse through soil  Requires correlation of several points from Proctor tests  Takes 15 to 20 minutes per test.  Had trouble with device at beginning  Removed from testing

17

18

19

20

21  Light-Weight Deflectometer (LWD)  Measures soil surface deflection  Provides Modulus, Deflection, Velocity  No moisture content results

22 LWD Results:  Compared Pass/Fail results based on 95% compaction of devices to standard (lab)  Nuclear Gauge: 72% correlation  LWD: 54% correlation  Overall – best correlation of new devices  Suggest better way to determine target value (not density)

23  Widely Accepted QA/QC Method  Indirect Parameter of Strength  Small Variations – Result Large Variation in Stiffness  Compaction Lab vs. Compaction Field  Costs/Regulations of Nuclear  Results are Material dependent based on a small sample compared to that in the field.

24

25  LWD Initial Costs: $8,257  Thermal Paper: $20/ Year  Maintenance/ Calibration: $300

26  Net Present Worth of Costs (NPW)= Initial Costs + Yearly Costs (P/A, 15 yrs, 10%)  NPW of Nuclear Gauge= $10,873 + $2,155(P/A, 15yrs, 10%) = $27,264  NPW of LWD = $8,257 + $320(P/A, 15yrs, 10%) = $10,690

27  Dynamic non-destructive testing tool  Measure layer/surface modulus (stiffness)  How it works  Transient Load on Loading Plate  Accelerometer within the device measures the deflection of the ground due to the load  Soil Modulus back-calculated based on deflection and assumed Poisson’s ratio.  Results taken as an immediate indication of the materials strength (ability to support roadway)

28  Modulus Calculation: E o = f x (1-  2 ) x  o x a / d o E o = Modulus f = Plate Rigidity factor (2)  Poisson’s Ratio (0.35)  o = Maximum contact stress a = Plate Radius d o = Maximum deflection

29  Zorn  Keros  Dynatest  Prima  Loadman  ELE

30  ASTM E for LWD without Load Cell  ASTM E for LWD with Load Cell  Plate Size  Drop Height  Falling Weight  Type and location of Sensors  Significant variability between manufacturers  Seating Load (3 Drops)  Testing Load (3 Additional Drops)

31  MnDot Research – Beginning 1997  NCHRP – 382 & 456  Colorado DOT  Vermont DOT  US Army Corps of Engineers  UK – Fleming, Frost, and Lambert  Virginia Transportation Research Council  Kansas DOT  Louisiana Transportation Research Center

32  Several LWD models with variety of differences  Steel spring buffer and accelerometer in plate  Critical to use same device with same plate diameter, drop height, and falling mass  Hand-held recording instrument  SD card memory  Graphical and numerical results  Printout of results  GPS capability

33

34 Normal Result For unbound materials

35 Rebound Common for Bound materials If rebound is >20% Of Peak Re-seat and retest

36 Variable May be poor Compaction

37

38  Recipe for Good Compaction  Know Soil Type  Moisture Control  Limit Lift Thickness  Compaction Testing  Stiffness/ Strength of materials  Target = Minimum Modulus or Maximum Deflection  Based on Material Type  Moisture Content  May Require A Test Strip

39  Side by Side LWD Tests & Nuke Tests  Bag Samples for Lab  Determine NGI & Moisture  Compare Deflection vs % Compaction for each Soil Type (NGI)

40 PI= 20 LL = 45 % Ret.= 50 Chart 1 = 3.5 Chart 2 = 3.5 NGI = 7

41

42

43

44  Modulus in Laboratory is complicated, expensive, and time consuming.  Test methods have continually changed over the years  NDOR – Resilient Modulus Research based on Nebraska Soil Types (NGI)  Correlate well with FWD  Do not correlate with LWD

45 Resilient Modulus Correlation to NGI

46  Deflection is easy to understand  Two Specifications  1.Provide Target Value for each NGI  2. Perform Test Strip / Calibration Area

47  Maximum Deflection based on Nebraska Group Index (PI, LL, #200)  First – Make sure moisture is within Spec.  Refer to Chart for Deflection Requirements

48 1.2 Target Value = Max Deflection 1.2 mm For Equivalent to 95% Compaction

49 Nebraska Group Index Concrete Upper 3'Concrete Below 3'Asphalt Upper 3'Asphalt Below 3' Max Deflection (mm) NGI = 7 Under Concrete Top 3’ NGI = 7 Under Asphalt Below 3’

50  Deflection Data for Soil Type not available  Perform a Test Strip/ Calibration Area  First Test Moisture  Size of Test Strip – 200’ Length x Width of Embankment, Two-8” Lifts  3 LWD Tests/ Roller Pass – Random Locations

51  Continue LWD/ Roller Pass Testing  Target Deflection Value Obtained when:  Moisture Content Acceptable Range (based on PL or Standard Proctor)  Average of Deflection Tests for three consecutive passes does not change significantly with each additional pass (when change is < 10%)  Obtain Rep. Sample from test strip for further lab testing  Passing Test = < 1.1 x Target Value

52  Re-Evaluate when:  More than 20% of test measurements are less than 0.8 x TV  Failing results consistently occur even though adequate compaction observed.  Perform new Test Strip

53  Finalize and Implement Specifications  Eliminate all Nuclear Gauges  Build NGI Chart  Find a reliable field moisture testing device

54 QUESTIONS?


Download ppt "Mark Lindemann NDOR Geotechnical Engineer.  Background on previous field testing  Research – Non-nuclear field testing  Cost Savings of Going Non-Nuclear."

Similar presentations


Ads by Google