07 GeoGauge Lecture

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GeoGauge LectureTM

September 2001

Scott FiedlerProduct Manager Humboldt Mfg. Co., Norridge, Illinois U.S.A.

GeoGaugeIllinois U.S.A.

TM

Directly measures the in-situ or in-place stiffness. Manufactured by Humboldt Mfg. Co. in Norridge, U.S.A. and World Patent Pending GeoGauge is trademark of Humboldt Mfg. Co.

2

To Meet A Need

Why The GeoGauge?

Relentless Pursuit of Lower Cost & Higher Quality By Achieving A Goal Increased Precision of Design & Construction Increased Continuity Between Design & ConstructionMechanistic Designs Performance Specifications Process Control

Through A Historically Successful Path Structural Stiffness & Material Modulus Engineering / Mechanistic Values

Design Parameters Used to Evaluate Construction Contractor Warranties

3

Physical Attributes Size: 280mm diameter x255mm tall Ring Foot

114mm OD x 89mm ID Weight: 10 kg Powered by 6 D-CellBatteries

IR Data Downloading(Optional)

Keypad User Interface

4

Operating PrincipleStiffness= Resistance of a Layer or Structure to Deformation+ Foot Radius & Poissons Ratio

Modulus

= Resistance of a Material to Deformation

At GeoGauge Frequencies & Stress, Impedance is Predominately No Need for a Non-Moving Displacement Reference Permits the Accurate Measurement of Small DisplacementsFdr = Kflex (X2 - X 1) Kgr = Fdr X1flex

Stiffness

Fdr = K flex (X 2 X1 ) + 2 m int X1(X 2 - X1 ) X1 n

Kgr = K

n

= Kflex

1

n

(V 2 - V1 ) V1 n5

1

Measurement Procedure Inspect GeoGauge Power On Select Mode & Poissons Ratio Seat the Foot Rough & Irregular Surfaces Smooth Hard Surfaces

> 60% Direct Contact Moist Sand Assisted (3 to 6 mm thick)

Take the Measurement:

75 Seconds (15 sec. Noise + 60 sec. Signal) Results Displayed

Examine the Foot Print Save Data

Signal/Noise: > 3/1 (10 db) Standard Deviation: a Measure of Foot Contact Average Stiffness or Modulus (English or SI)

6

Specification Stiffness: 3 to >70 MN/m (17 to >399 klbf/in) Youngs Modulus: 26 to >607 MPa (4 to >88 kpsi) Poissons Ratio: 0.20 to 0.70 in 0.05 Increments Precision: Typically 3.9% Coefficient of Variation Bias: < 1% Coefficient of Variation Depth of Measurement: 220 to 310 mm Battery Life: > 1,500 measurements Operating Temperature: 0 to 38C

7

PrecisionSingle GaugeM ean 8/16/96 Salisbury ByPass 9/19/96 10/12/96 10/13/96 10/19/96 10/28/96 NM 44 16 Vegas Dr. Silty Sand 6.28 11.33 8.86 51.37 40.20 12.74 Date Site M aterial Typical Stiffness, M N/ m 1 0.28 0.37 0.47 2.17 1.57 0.35 M ean 4.08 3.31 5.35 4.25 3.84 2.67 Coeff. Of Var., % 65% Confidence 6.01 7.17 5.66 5.21 3.13 95% Confidence 7.94 9.00 7.07 6.58 3.59 Sandy Clay Subgrade* Sility Clay**

16 Vegas Dr. Full Depth Pavement* I70/I270 Rutters Graded GAB* Fat Clay*

* Assisted Seating (moist sand) ** Unprepared ground

Typical Coefficient Of Variation: 3.9% Basis: 3 Gauges, 3 Operators & 470 Measurements8

Multiple GaugesDate 11/ 6/ 96 11/ 6/ 96 11/ 7/ 96 11/ 23/96 Site 16 V egas Dr. 16 V egas Dr. 16 V egas Dr. 16 V egas Dr. M aterial Sility Clay** Sility Clay** Full Depth Pavement* Sility Clay** No. of M easurements 12 30 16 10 Stiffness, MN/ m M ean 8.50 9.94 44.83 10.06 1 0.33 Coeff. of V ar. % 3.89 3.91 3.83 5.84

Precision

0.39 1.72 0.59

ssisted Seating (moist sand) * A ** Unprepared ground

Statistics Based on Combined Measurements From Both Gauges Basis: 2 Gauges, 1 Operator & 68 Measurements

9

Bias Reference: Moving Mass Known Mass: 10 kg 25 Known Frequencies: 100 to 196 Hz Stiffness = -j 2M Coefficient of variation: < 1%

10

Calibration Platen Reference: Moving Mass, Platen of Certain Geometry Known Mass: 10 kg 25 Known Frequencies: 100 to 196 Hz Stiffness = -j 2M Coefficient of variation: < 1%

11

Verifier Mass

Used whenever a

check of GeoGauge operation is desired12

What is GeoGauge Stiffness ?Quasi-Static Field Plate Load Test Results60k=18.2

GeoGauge Measurement: k=14.5 klb/in50Unloading

k=14.7 k=14.8

Load 40 (lb)

Loading

k=11.8

Performed by CNA Consulting Engineers Typ. of a Granular Base September, 99

30k=12.8 klb/in

20k=1.68 k=8.01 k=6.98 k=8.15 GeoGauge Measures the Reaction of the Soil to Removing the Working Load

10

0 0 0.005(in) 0.01 Deflection, 0.015

0.02

0.025

0.0313

GeoGauge Stiffness: How To Confirm It?University of New Mexico, ATR Institute Model Footing Precisely Constructed of Cohesionless Sand Measure Stiffness With GeoGauge Calculate 9 Layer Stiffness From: Measured Void Ratio Estimated Mean Effective Stress Under GeoGauge Foot Estimated Poissons Ratio0.00 0 0.40 3 Vertical Effective Stress, psi 0.80 1.20 1.60

Geostatic Effective Stress Load Induced Stress Total Stress

6

Measured Stiffness Within 5%

9 Depth, in.

of Calculated Value GeoGauge Can Sense Boundaries Up to 12 From Its Foot To be Repeated on Silt, Clay & Layered Media

12

15

18

21

Uniform Vertical Annular Line Load Center Line Stress @ r = 0 (Line Load = 1.752 lb/in., Annular Radius, a = 2.0 in.)

24

14

Correlation to Other ModuliSection 17, Mn/ROADModulus ( MPa) Compaction (%)

Seismic, ES (MPa)2500 2000

Subgrade & Base Materials In 6 TXDOT DistrictsSeismic vs. GeoGauge Modulus

200

1201500 1000 500 0 0

E S = 6.27EG - 31.91 Correlation Coefficient: .79

150

115

PFWD (small plate) PFWD (large plate)

100 50

110 105

DCP (6" avg.) DCP (3" avg.) GeoGauge sc compaction

50

100

150

200

250

300

350

400

FWD, E F (MPa)1500 1200

GeoGauge, EG , (MPa)

0

100

ng compaction

FWD vs. GeoGauge ModulusE F = 4.08E G - 231.53 Correlation Coefficient: .80

-50 1 2 3 4 5 6

95

900 600

13 Pavement Sections at 5 MnDOT Sites

300 0 0 50 100 150 200 250 300 350 400

GeoGauge, EG, (MPa)

15

Correlation to Dry Density2 1Analytical-Empirical Relationship Calculate C From Regional Companion Measurements of Stiffness, Moisture Content & Dry Density

3

Define Several Linear Relationships Between C and K/m .25 For Groups of Regional Soil Classes

C = (K/m)

{[( /0

D-1)

/1.2] + 0.3}

2

5000 4000 3000

C = 2.26(K/m .25 ) + 160.36 Correlation Coefficient: 0.98

C, C, klb/in klb/in2000Estimated Density Re Measured Density

01 + 1.2 [.5 mC - .3].5 K

1000

A-2-4 and A-2-5 Soils0 0 500 1000K / m , klb/in K/m^.25, kip/ft.25

1500

2000

110

A-2-4 and A-2-5 Soils105

4From Measurements of Stiffness & Moisture Content And A Calculated C, Estimate Dry Density Using the Same Analytical-Empirical Relationship

100

(GeoGauge), pcf

95

Data from MODOT, November, 99

90

85 90 95

(GeoGauge.)

= 0.58(

(Nuc ) )

+ 39.39

85

Correlation Coefficient: 0.78

100

105

110

115

(Nuclear), pcf

16

Other Correlations Resilient Modulus Unconfined Compressive Strength California Bearing Ratio (CBR) Dynamic Cone Penetrometer (DCP) Static Cone Penetrometer Plate Load

17

GeoGauge AlternativesMetho d : In-Place St i ffness or Mod u u l s*One that does not delay or interfere with construction

Sp

* Production Test:

18

Soil Physics & Measurements Soil Impedance Wave Propagation

Development: BBN Shallow Soil Seismic/Acoustic Research

Transducer Coupling Research System Development & Displays2m Hole

Seismic Array

BBN Proprietary Weight-biased Geophones and Compact Vibrator Source

Mine

Seismic Sonar Display of Response of Mine19

Design Validation Alpha Field Trials: MN, NY & TX Construction Noise: Freq. Shift & Improved Filtering Calibration: Soil vs. Elastomer vs. Mass Relationship Between Density & Modulus Beta Field Trials: MN, TX, NC, FL, OH, CA, NJ & MO Usability & Reliability Manufacturing & Test Methods Development Establish Precision & Bias Standards Development ASTM AASHTO20

Benefits of Stiffness & Modulus TodayControl of Compaction Mitigating the Risk of Pavement Failure Control of Stabilized Fill Quality

Control of Compaction QualityDensity or Stiffness Job by Job / Material by Material Evaluation Stiffness added to Proctor or Proctor Like Testing Empirical Relationship vs. Moisture Determined118

Univ. of NM, ATR Inst. Silty Sand Unified SM AASHTO A-2-4 Standard Proctor 30 Effort

Stiffness116 25

Stiffness Lab / Test Strip Correction (Proctor Mold) Conditions for Using Stiffness Lift Thickness: > 8 Awareness of Variability from Lift Support

Unique Stiffness of each Moisture & Density Pair

114

20

Density112

100 % Compaction15

110

10

108

5

98 % Compaction106 0 5 10 15 0

Moisture Content, %

22

Control of the Compaction Process Compaction of A Layer Is Only As Good As the Supporting Material Will Allow Directly Measure Compaction (Rate of Increase in Stiffness) As a Function of Effort When the Rate Is