Accelerated Pavement Testing at the Geotechnical and Structures Laboratory

Transcription

1 Accelerated Pavement Testing at the Geotechnical and Structures Laboratory Vicksburg, Mississippi, U.S.A. U.S. Army Engineer Research and Development Center

2 Accelerated Pavement Testing HVS Conventional Airfield Light-Duty Road Rapid Patching of Airfields Swamp Roads Non-HVS Beach Roads Aggregate-Surfaced Roads Mat-Surfaced Aprons Stabilized-Surfaced Aprons Geosynthetic-Reinforced Roads? NCAT Instrumentation NCAT Instrumentation U.S. Army Engineer Research and Development Center

3 Swamp Roads Difficult Terrain LANE 1 Swamp LANE 2 Swamp

4 Swamp Roads Difficult Terrain

5 Critical Load Involves Turning 30 ft. R = 50 ft. R = 50 ft. R = 75 ft. R = 50 ft. 50 ft. 75 ft. Beach Roads 5 ft.

6 Mat-Surfaced Aprons Turnaround >3500 ft >300 ft >90 ft >165 ft >300 Overrun Rapid Soil Stabilization and/or Light-Weight Mats

7 Mat-Surfaced Aprons Durabase Mat Multi-Purpose Mat

8 Mat-Surfaced Aprons Rapid Mat Rolla Road SP-12 Mats

9 C-130 Load Cart 30, psi Mat-Surfaced Aprons

10 Mat-Surfaced Aprons 15 cm High (40-50 CBR) Subgrade Support Clay Gravel Durabase MP Mat Rolla Road Rapid Mat SP cm Buckshot Clay Durabase MP Mat 60 cm Medium (8-10 CBR) Subgrade Support Buckshot Clay

11 Stabilized-Surfaced Aprons 6% PC 2.3% P3 2.9% P1 3% PC Silty Sand 12 m 2.4 m 9% PC 4.6% P3 5.8% P1 3% PC

12 Stabilized-Surfaced Aprons Cement Stabilization of Silty Sand

13 Stabilized-Surfaced Aprons Tilled Before Stabilizing Added the Stabilizer Tilled Again (2 passes) Wait 28 days, Add Traffic Compacted to 95% Proctor

14 Stabilized-Surfaced Aprons Primary Conclusions Cement or (cement + polymer) Simple laboratory strength tests not very well correlated with field tests

15 Geosynthetic-Reinforced Roads Plan View Shoulder 12 Transition Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8 Slab 3 Shoulder Longitudinal Cross-Section 6 Transition Crushed Aggregate GW Clay Gravel GP-GC GC Crushed Limestone GW Crushed Limestone GW Crushed Limestone GW Crushed Limestone GW Clay Gravel GP-GC GC Crushed Aggregate GW Slab 24 Geotextile (NW) Geogrid Geotextile (NW) CH Soil with CBR = 4 Geogrid Geogrid Geogrid ML-CL Soil with CBR = 10

16 Geosynthetic-Reinforced Roads

17 Geosynthetic-Reinforced Roads

18 Geosynthetic-Reinforced Roads Longitudinal Cross-Section Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8 6 Transition CH Soil with CBR = 4 ML-CL Soil with CBR = 10 Earth Pressure Cell Strain Gage Pore Pressure Transducer Moisture and Temperature Single Depth Deflectometer (SDD) 8-ft Anchor

19 Geosynthetic-Reinforced Roads Plan View Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8 12 Transition 6 Slab 3 Shoulder Earth Pressure Cell (EPC) Single Depth Deflectometer (SDD) Pore Pressure Transducer Moisture and Temperature

20 Geosynthetic-Reinforced Roads Strain Gages on Geogrid/Geotextile Plan View Item 4 (25-ft) Item 6 (30-ft) Strain gage

21 NCAT Test Track Year 2000

22 NCAT Test Track Year 2000 N Campbell Scientific datalogger Troxler probe reader drainage outlet drainage outlet with tipping bucket traffic counting device Lab with Computers W2 W1 N13 N12 N11 N10 N9 N8 N7 N6 N5 N4 N3 N2 N1 E10 E9 W3 E8 W4 E7 W5 E6 W6 E5 W7 E4 W8 E3 W9 W10 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 E1 E2

23 NCAT Test Track Year to 100 mm 150 mm HMA Upper Asphalt Binder Course temperature probes 230 mm Lower Asphalt Binder Course 125 mm 150 mm Permeable Asphalt Treated Base Crushed Granite Base Course geotextile 305 mm AASHTO A-2 Select Fill moisture probes Foundation Soil

24 NCAT Test Track 0.3 m Year 2000

25 NCAT Test Track Year 2003 Alabama DOT Structural Sections

26 NCAT Test Track Year 2003

27 HVS Capabilities Dual Commercial Truck Super Single B-52 Military Truck F-15 1 m C-17 (new) 1 m

28 Conventional Airfield North Item Paved Surface South Item asphalt 115 mm 115 mm concrete 580 mm North Item crushed limestone South Item 840 mm 1220 mm fat clay 1220 mm sand

29 Conventional Airfield N 40 ft 10 ft horizontal strain vertical deflection vertical stress

30 Conventional Airfield C-5 CBR p e t 2.0 α A 3.0 test section performance 4.0 cubic CBR equation 90% confidence interval 5.0

31 Conventional Airfield 0.0 CBR p e t α A High Repetitions B cubic CBR equation 90% confidence interval 5.0

32 Conventional Airfield Report Primary Conclusions No evidence that current design procedures are unconservative for high-repetition traffic Need methods of accounting for densification/consolidation under heavy aircraft Extensive presentation of response under static and rolling loads Deflection, stress, and strain Loads from single truck tire to C-17 gear

33 Light-Duty Roadway dual truck tires F-15 super-single F-15 F-15 F-15 super-single super-single 15.2 m x 15.2 m - vertical deflection - vertical stress 50 mm 150 mm AC SP-SC CH (CBR = 9)

34 Non-Destructive Testing

35 SASW for Monitoring Deterioration Station (ft) Lane 8 Rut Depth (in.) Dual Truck Tires 67 kn (15000 lb) Lane 8, Station 25 (Surface Layer) 16 Modulus (ksi) Thickness (in.) E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 Passes

36 Laser for Measuring Surface Profile Lane 2 Super-Single w/ 67 kn passes Station Relative Elevation (in.) Transverse Distance (in.), West to East

37 Laser for Measuring Surface Profile Lane 2 Super-Single w/ 67 kn passes Station Relative Elevation (in.) Transverse Distance (in.), West to East

38 Light-Duty Roadway Conclusions from performance under traffic USACE LE predicted stress better than deflection USACE design models need improved accounting of marginal materials Super-single more damaging than standard dual APT programs should always Quantify spatial variability Practice replicates where possible U.S. Army Engineer Research and Development Center

39 Modeling PCASE CBR and Westergaard Layered Elastic STUBBS PC-based finite element Random Walk (Milton Harr) Stress (2002) Strain and Deflection (2003) U.S. Army Engineer Research and Development Center

40 Predicting Pavement Response to Loads Milton Harr Purdue University started with estimating stress state Conceptually similar to a random walk Central limit theorem

41 Predicting Stress State Only one material parameter needed: coefficient of lateral earth stress, ν ν = σ h σ v Conceptually similar to coefficient of lateral earth pressure, K Represents the degree to which materials spread the load Load is uniformly distributed over a circle or a rectangle

42 Predicting Stress State Vertical Stress (kpa) ν = 0.50 ν = 0.25

43 Predicting Stress State Back-calculating ν-values Stress Depth ν 1 ν 2 calculated measured

44 Predicting Stress State Back-calculated ν-values

45 Predicting Stress State Advantages of probabilistic stress estimates Simple: one parameter, few assumptions Explicit, non-iterative solution Method includes a solution for multi-layer systems kn load 690 kpa pressure 150 mm depth Maximum Shear Stress (kpa) "nu" = 1/3 Poisson = 0.5 Poisson = Transverse Location (mm)

46 Predicting Strains and Deflections Advantages of probabilistic estimates of strain or deflection (ν + E) Same list as previous slide, plus Elastic modulus and load spreading are considered separately. AC unbound crushed limestone CH E ν E ν

47 Accelerated Pavement Testing in 2004 Rapid Patching of Airfields JRAC Program AC-surfaced and PCC-surfaced pavements Joint spall and localized patch repairs C-130 and C-17 aircraft U.S. Army Engineer Research and Development Center

48 Accelerated Pavement Testing in 2004 Rapid Patching of Airfields

49 Accelerated Pavement Testing in 2004 Rapid Patching of Airfields Move experiment to HVS facility Concentrate on a few materials U.S. Army Engineer Research and Development Center

50 Accelerated Pavement Testing in 2004 Aggregate-Surfaced Levee Roads USACE MVD needs a pre-bid acceptance test to qualify aggregate sources Currently, the specification addresses only gradation, LL, and PI Lab component and field component 5 aggregate sources 20 pavement test items

51 Accelerated Pavement Testing in 2004 Test Track (1.7-mile outer loop) Aggregate-Surfaced Roads

52 Accelerated Pavement Testing in 2004 Test Track Inaccessible by the HVS

53 Accelerated Pavement Testing in 2004? Move experiment to HVS facility?

54 Reports - APT Expedient Road Construction Over Soft Soils Enhanced Coastal Trafficability: Road Construction Over Sandy Soils Instrumentation at the National Center for Asphalt Technology Test Track Accelerated Loading on Asphalt Pavement with a Thick Granular Base Accelerated Loading on Asphalt Pavement with a Marginal Base Material

55 Reports - Modeling Modeling Permanent Deformation of Unbound Granular Base Layers Asphalt Pavements Subjected to Aircraft Loading Thermodynamic Approach to Modeling Partially Saturated Soils Reliability-Based Approach to Predict Load-Induced Structural Failure in Asphalt-Surfaced Pavements

56 Thank You U.S. Army Engineer Research and Development Center