A National Catalog of Subgrade Soil- Water Characteristic Curve (SWCC) Default Inputs and Selected Soil Properties for Use with the ME-PDG

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1 A National Catalog of Subgrade Soil- Water Characteristic Curve (SWCC) Default Inputs and Selected Soil Properties for Use with the ME-PDG Claudia E. Zapata Arizona State University March 17,

2 Introduction Objectives of the Study Background Information What is Needed by EICM Plan of Work How the Catalog was Developed Presentation of an User s Interface Summary and Opportunities for ME-PDG Enhancement OUTLINE 2

3 Introduction Implementation of the ME-PDG Guide is crucial to the long term success of the US highway network It allows the engineer to assess sensitivity of most critical parameters that will influence performance The Enhanced Integrated Climatic Model (EICM) main engine within the guide: Input collection, and Characterization and analysis of environmental and unbound properties effects on the material stiffness Significant role in predicted pavement distresses 3

4 Background EICM input (variables and parameters) needed is large Climatic information Temperature Rainfall Sunshine Relative humidity Wind speed Readily available +800 weather stations 4

5 Background Unbound material parameters Compacted materials Subgrade materials Routine index properties Specialized moisture retention parameters Widely used by agricultural science Becoming popular to the geotechnical community Relatively unfamiliar to the pavement community 5

NCHRP 9-23A Project Objectives Creation of a National Database that Reflected Subgrade Materials Properties Needed in the Implementation of the ME-PDG Catalog

6 NCHRP 9-23A Project Objectives Creation of a National Database that Reflected Subgrade Materials Properties Needed in the Implementation of the ME-PDG Catalog (Database) Maps Database focuses on subgrade material properties Index soil properties SWCC parameters Estimates of strength and moduli All hierarchical levels of analysis 6

7 EICM Hierarchical Approach to Determine Input Parameters LEVEL 1 Comprehensive lab, field testing to directly determine index properties and unsaturated soil properties LEVEL 2 Indirect determination of unsaturated properties from other properties (correlations) Measured index and volumetric properties LEVEL 3 Indirect determination of saturated and unsaturated soil properties using correlations Measured index properties

8 Level 1 Gradation Atterberg limits Plasticity Index Liquid Limit Compaction Max. dry unit weight Opt. moisture content Saturated permeability Specific gravity SWCC parameters

9 Level 2 Gradation Atterberg limits Plasticity Index Liquid Limit Compaction Max. dry unit weight Opt. moisture content Saturated permeability Specific gravity SWCC parameters

10 Level 3 Gradation Atterberg limits Plasticity Index Liquid Limit Compaction Max. dry unit weight Opt. moisture content Saturated permeability Specific gravity SWCC parameters

11 EICM Input Parameters Groundwater table Level 1 From profile characterization Level 2 Seasonal variation Level 3 Annual average 11

12 EICM Input Parameters Groundwater table Level 1 From profile characterization Level 2 Seasonal variation Level 3 Annual average 12

13 NCHRP 9-23A Plan of Work Task 1 - Development of the Database Data acquisition Processing Reduction and sorting Computation of parameters when not directly available Task 2 Development of GIS-based soil unit maps Development of a simple user s interface to extract data 13

14 TASK 1 DEVELOPMENT OF DATABASE 14

15 Origin of Database National Resources Conservation Service (NRCS) from the US Dept. of Agriculture (USDA) database Initially intended for agricultural purposes Key soil properties useful in highway/pavement engineering Joint agreement with the then Bureau of Public Roads (BPR) NRCS databases different levels of detail Soil Survey Geographic (SSURGO) database State Soil Geographic (STATSGO) database National Soil Geographic (NATSGO) database 15

16 Soil Data NATSGO: Scale is 1:5000K Used primarily for national and regional resource appraisal and planning STATSGO: Scale is 1:250K Polygon size is about km 2 SSURGO: Scale is 1:24K Polygon size is about 20 km 2 16

17 Scale Difference STATSGO-SSURGO Source: Ziya Zhang et al. 17

18 Processing the Data Data is of public domain and available from the Soildatamart website Two types of data are available Tabular Spatial Spatial files or shapefiles that allows Analysis of spatial information Editing of data Creation of maps in GIS-based format 18

19 Map Unit and Component Map unit Area with a group of soil profiles (components) with similar characteristics Component Soil profile 19

20 Map Unit and Component Profile or Component Several layers ranging in number from 3 to 11 Average depth = 60 in. with a good number of profiles approaching 100 in. The component with the largest percentage of coverage was assumed to be representative of the entire map unit. 20

21 Preliminary File Downloaded File The initial master file created with the information extracted from NRCS contained data for 1,227,117 boring logs throughout the USA and Puerto Rico Missing Information Only (11.6%) of the total number of soils mapped were found to have incomplete information at the NATSGO level. 21

22 Available Data - SSURGO 22

23 Data Reduction Criteria Boring logs with similar characteristics were averaged The profile with the largest percentage of coverage was assumed to be representative of the entire soil unit Final count in NCHRP 9-23A Catalog 9,827 map units 31,100 soils 23

24 Properties Collected Grain-size distribution (99%) Passing #4, #10, #40, #200 Percentage of clay (> mm) (4%) Atterberg limits Liquid limit (88%) Plasticity Index (99%) AASHTO soil classification (100%) Saturated hydraulic conductivity (100%) Enough data to estimate the Fredlund and Xing soil-water characteristic curve (SWCC) parameters (66%) Groundwater table depth Annual average (32%) Seasonal (29%) 24

25 Properties Estimated Soil horizon layer thickness AASHTO Group index SWCC parameters From moisture-suction measurements CBR From soil index properties Resilient modulus From estimated CBR 25

Group Index Estimated based on equation from AASHTO M145-91 Standard Specification for Classification of Soils and Soil-Aggregate Mixtures for

26 Group Index Estimated based on equation from AASHTO M Standard Specification for Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes Concept that categorizes the probable service performance of the soil when used as a highway pavement subgrade 26

27 SOIL-WATER CHARACTERISTIC CURVE PARAMETERS 27

28 SWCC Parameters The SWCC is the relationship between soil moisture content and the matric suction at equilibrium conditions Suction dictates the moisture retention or storage capacity of the soil Suction is perhaps the most important stress state in the gradient that causes fluid flow when the soil is not 100% saturated 28

29 Darcy s Law Gets a Bit Complicated when S r < 100% 29

30 Influence of Soil Type on SWCC Degree of Saturation, S Sand Silt Clay Matric Suction (kpa) 30

31 SWCC Descriptive Parameters 31

32 SWCC Hysteresis SWCC hysteresis may have an important role in the soilatmosphere fluxes Effect of SWCC hysteresis during cycles of evaporation and precipitation events can be significant for fine-grained materials ME-PDG considers only the drying branch 32

33 SWCC Mathematical Models Several models exist to describe the SWCC ME-PDG makes use of the Fredlund-Xing model 33 + θ = θ c b s w a h exp(1) ln C(h) + + = r 6 r h 10 1 ln h h 1 ln 1 C( h ) Input parameters: a b c h r

34 NCHRP 9-23A Product SWCC parameters were found for 31,100 soils Nonlinear optimization minimizing the sum of the squared errors Solver function in Excel and macros LEVEL 1 Degree of Saturation, S Matric Suction (kpa) 34

35 CBR AND RESILIENT MODULUS FROM SOIL INDEX PROPERTIES 35

36 CBR and Resilient Modulus CBR for coarse, clean, typically non-plastic material CBR = (D 60 ) CBR for materials with fines that exhibit some plasticity CBR = 1 + Resilient modulus (wPI ) CBR and M R values should be confined only to Level 3 applications of the ME-PDG because they are rough estimates 36

37 TASK 2 GIS-BASED UNIT MAPS 37

NCHRP 9-23A Task 2 Objective Collection and reduction of cartographic information This information was the basis for the creation of a series of maps that will allow

38 NCHRP 9-23A Task 2 Objective Collection and reduction of cartographic information This information was the basis for the creation of a series of maps that will allow the user of the ME-PDG to visually identify the geographic region of interest Cartographic Process Software ESRI s ArcGIS 9.2 Microsoft Excel 2007 Microsoft Access

39 GIS/Cartographic Process Data Collection from US Census Bureau website Downloading of boundary files for the 50 states and Puerto Rico Downloading of main Interstate road network Road shapefiles from counties were combined to get 50 new shapefiles Soil unit boundaries and related tabular data were downloaded from the USDA NRCS database State boundary and map unit files were combined 39

40 Map Projection / Coordinate System Original data was downloaded as unprojected shapefiles (with the GCS North American 1983 coordinate system) To avoid distortion: Data was re-projected to a more appropriate projection and coordinate system Each state was treated as a separate set of maps, and the State Plane Coordinate System (SPCS) was employed A Map Character number was assigned to each map unit Allow the user to easily search for the unbound material information needed to run the ME-PDG 40

41 IMPLEMENTATION: USER S INTERFACE 41

42 Excel User s Interface Extraction tool that facilitates the use, analysis and reporting of the data and maps implemented in this project It contains: Links to the maps created which allows the user to choose the soil unit of interest Macro that controls and extract, in a printable report, all the information available for that particular unit 42

43 Step 1 Choose a State 43

44 Step 1 State map will be displayed Each state is divided into regions/grid Example 1: Vermont 44

45 Step 1 Example 2 Louisiana 45

46 Step 1 Example 3 Georgia 46

47 Step 1 Example 4 Alaska 47

48 Step 2 Select the State Region Map of interest 48

49 Step 2 Region Map will be displayed Example 1: Connecticut Soil unit map 4 49

50 Step 2 Example 2: Illinois Soil unit map 3 50

51 Step 2 Example 3: Iowa Soil unit map 5 51

52 Step 2 Example 4: Texas Soil unit map 16 52

53 Step 3 Select the map unit desired to extract the relevant soil properties Input alphanumerical value 53

54 Step 4 Display and/or print a report of the soil properties for that particular map unit View Report 54

55 Step 4 View Report Map Char PJ5 Mapunit Key Mapunit Name Woodbridge-Ridgebury-Paxton (s6625) Component Name Ridgebury Top Layer Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 Layer 7 Layer 8 Layer 9 AASHTO Classification A-5 A-5 A-5 AASHTO Group Index Top Depth (in) Bottom Depth (in) Thickness (in) % Component Water Table Depth - Annual Min (ft) Depth to Bedrock (ft) STRENGTH PROPERTIES CBR from Index Properties Resilient Modulus from Index Properties (psi) 16,842 17,755 19,823 N/A 55

56 Step 4 View Report INDEX PROPERTIES Passing #4 (%) Passing #10 (%) Passing #40 (%) Passing #200 (%) Passing mm (%) Liquid Limit (%) N/A N/A N/A Plasticity Index (%) Saturated Volumetric Water Content (%) Saturated Hydraulic Conductivity Ksat (ft/hr) SOIL-WATER CHARACTERISTIC CURVE PARAMETERS Parameter af (psi) Parameter bf Parameter cf Parameter hr (psi) 3,

57 Recall SWCC Equation and Fitting Parameters 57 + θ = θ c b s w a h exp(1) ln C(h) + + = r 6 r h 10 1 ln h h 1 ln 1 C( h ) Input parameters: a b c h r

58 Recall SWCC Equation and Fitting Parameters Input parameters: a = 7.8 b = 0.99 c = 0.97 h r =

59 Level 1 Gradation Atterberg limits Plasticity Index Liquid Limit Compaction Max. dry unit weight Opt. moisture content Saturated permeability Specific gravity SWCC parameters

60 Step 4 Printable Report 60

61 SOFTWARE DEMONSTRATION 61

62 SUMMARY / OPPORTUNITIES FOR ME-PDG ENHANCEMENT 62

Summary Result of this project will provide the user of the ME- PDG with an implementable tool that can be used to extract unbound material properties Catalog provides measured data Level 3

63 Summary Result of this project will provide the user of the ME- PDG with an implementable tool that can be used to extract unbound material properties Catalog provides measured data Level 3 Level 2 Level 1 Largest SWCC database in the world Tremendous asset to the ME-PDG implementation Catalog opens opportunities for ME-PDG improvement and enhancement with implementation tecniques 63

64 Enhancement of ME-PDG Massive database can be used to conduct future studies to enhance the ME-PDG 1. Incorporation of the NCHRP 9-23A Products into the ME-PDG to Aid Users with Input Phase Experience A. Incorporate GIS-based map of soil units B. Superimpose U.S. highway system on soil maps C. Incorporate new feature to allow user to define a route of interest D. Refine resolution of regional map units to illustrate more detail 64

65 Enhancement of ME-PDG 2. Improvement of Default Unbound Material Properties Currently Implemented in ME-PDG A. Grain-size distribution B. Atterberg limits C. Saturated hydraulic conductivity D. SWCC parameters 65

66 Enhancement of ME-PDG 3. Incorporation of Additional Maps of other Key Pavement Design Input Parameters A. Development of regional contour maps of HMA effective temperature for fatigue cracking and permanent deformation for U.S. B. Development of regional contour maps of groundwater table depth for U.S. C. Development of regional maps of estimated resilient modulus, CBR, R-values and modulus of subgrade reaction 66

67 Enhancement of ME-PDG 4. Enhancement of the EICM Moisture Content Predictive Models A. Refinement of resilient modulus-moisture model to account for soil type distribution B. Refinement of SWCC models to account for hysteresis due to wetting/drying cycles C. Recalibration of resilient modulus- R-value relationship with a better database 67

68 Acknowledgments Ed Harrigan Project Coordinator Graduate students Gustavo Torres Natalie Lopez Carlos Cary Undergraduate student Berenice Barranco 68

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