Rational Incorporation of Subsurface Drainage within an M-E Design Framework

Transcription

1 Rational Incorporation of Subsurface Drainage within an M-E Design Framework Mn/ROAD January 2003 TRB COMMITTEE A2K06 SUBSURFACE DRAINAGE Ruth Roberson

2 Acknowledgments Local Road Research Board (LRRB) Special Thanks Dr. Bjorn Birgisson (U of Florida, Gainsville) Defne Apul (UNH, RMRC) Bruce Tanquist (Mn/DOT) Mn/ROAD

3 Material Moisture Characterization Mechanical Characterization Numerical Methods Mechanistic-Empirical Design (MnPAVE) Evaluation of Pavement Current Drainage Design (SEEP/W) Mn/ROAD Cost Effective Pavement Design (New and Reconstructed)

4 Objective Linking Material Moisture Characteristics to Design Parameters Mn/ROAD

5 Material Characterization for M-E and Drainage Design Develop Framework for Incorporation Into Design Measurements and Instrumentation (MnROAD) Moisture Conditions Determine moisture regime Develop soil property functions Determine relationship to design variables Implementation Design M-E design (Material Properties) Evaluating Current Drainage Designs Mn/ROAD

6 Mn/ROAD Seasonal Moisture Content Saturation 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% CL ft OWP CL ft OWP CL ft OWP CL ft OWP 0% Jan-93 Jun-94 Oct-95 Mar-97 Jul-98 Time (date)

7 Base Water Contents Top of Base 0.5 ft Bottom of Base 1.3 ft Middle of Base 0.8 ft Percent Saturation Cell 35 5-Mar 4-Apr 4-May 3-Jun 3-Jul 2-Aug 1-Sep DATE

8 Base Water Contents % Saturation CL 0.97' (daily avg) OWP 1.09' (daily avg) PRECIP (daily sum) February-October 1998 TIME (julian day) Cell Precipitation (in)

9 Moisture Conditions Moisture conditions within the pavement system vary over time and space. Material characterization must take into account both saturated and unsaturated properties. Saturated and unsaturated properties must be considered in M-E and pavement drainage design. Mn/ROAD

10 Material Characterization for M-E and Drainage Design Estimating SWCC (SV Database) Pedo-transfer function Van Genuchten, Fredlund and Xing, Brooks and Corey, etc.. (Cu, PI, D10, D60,density) Evaluate Drainage Designs (SEEP/W) M-E Design Resilient Modulus Pore suction resistance factors τ =c + (σ n u a ) tan φ + (u a u w ) [(Θ k ) tan φ ] (Vanapalli 1996)

11 Applications Design Evaluating Current Drainage Designs ME-design Mn/ROAD

12 Soil Water Movement Flux is the volume flow rate per unit area (cm 3 /sec/cm 2 ). Saturated conditions: flux is proportional to the gradient and the hydraulic potential is independent of the conductivity. Unsaturated conditions: flux remains proportional to the hydraulic gradient but conductivity depends on hydraulic potential. q = -K H (Darcy s law) q = -K(Ψ) H (Richards 1931) θ/ t = [K(Ψ) H] (Richards equation)

13 Soil Water Characteristic Curve Saturation 100% CL3 est. 90% CL 5 est. CL 3 measured 80% CL 5 measured 70% 60% 50% 40% 30% 20% 10% 0% CL 4 est. CL 6 est. CL 4 measured CL 6 measured Suction (kpa) Van Genuchten fit (RETC)

14 Tempe Cell and Pressure Plate Extraction

15 Estimate Hydraulic Conductivity Function 0.2 Hydraulic Conductivity (m/day) CL 4 est. CL 5 est. CL 6 est Suction (kpa) Muelam (RETC)

16 Evaluating Current Drainage Designs

17 Applications Design Evaluating Current Drainage Designs M-E Design Mn/ROAD

18 Seasonal Pore Suction Resistance Factors Material % Saturation *Mean (summer) SD Suction (kpa) Mn/ROAD Class Mn/ROAD Class Mn/ROAD Class Mn/ROAD Class *difference is significant, n=418 Generated From Mn/ROAD Test Sections Used as MnPAVE default values (Basic Level) Mn/ROAD

19 MnPAVE View Default Values Mn/ROAD

20 MnPAVE Mn/ROAD Class Material Mn/ROAD

21 MnPAVE Select to input aggregate gradation Mn/ROAD

22 MnPAVE D60, porosity, etc. are calculated Mn/ROAD

23 Mn/ROAD MnPAVE

24 Mn/ROAD MnPAVE

25 Conclusion/ Current & Future Research Current drainage design and traditional soil mechanics methods are based on assumptions and design criteria which over simplify in situ conditions. Continue to develop and implement rational approach which incorporates unsaturated properties into the M-E and drainage design process. Continue to build extensive and comprehensive database of unsaturated material properties. Extend framework to recycled materials.

26 Cooperating Universities and Researchers University of Florida, Gainesville (Dr. Bjorn Birgisson) University of Minnesota, Department of Soil, Water, and Climate (Dr. Satish Gupta) Recycled Materials Resource Center (RMRC), University of New Hampshire (Defne Apul, Drs. Eighmy and Gardner) Lakehead University, Thunder Bay (Dr. Sai Vanapalli)

27 More Information Unsaturated Properties of Engineered Materials Research perties.asp MnPAVE (Download M-E Design Software) M-E Design Implementation Resources Recycled Materials in Pavements Ruth Roberson or (651)