Stiffness and permeability evaluation of a geocomposite drainage layer for granular-surfaced roads

Transcription

1 Stiffness and permeability evaluation of a geocomposite drainage layer for granular-surfaced roads 2015 Mid-Continent Transportation Research Symposium August 19, 2015 David J. White, Ph.D., P.E. Jeramy Ashlock, Ph.D. Cheng Li, M.S. Department of Civil, Construction and Environmental Engineering Iowa State University

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6 Current practice is to build and maintain a 4% road surface crown to drain water to ditches. 6

7 Several methods were evaluated for mitigating freeze-thaw damage to granular surfaced roads. 1700' N 250' 550' ' 500' 500' 332' control 475' 400' control 2 x 345' 520' 400' 4 x 600' 263 control 2 x 300' 1A 1B A 19B 20 ~28' Dirty Macadam Stone Base Clean Macadam RPCC Macadam Agg. Columns 5% Bentonite 15% Fly Ash G.C. Drain 6% Cement BX- Geogrid 5% bentonite surface treatment Calcium chloride surface treatment NW- geotextile between base and surface No treatment 12: G.C. lining 13: No lining 19A: BX-geogrid +NW-geotextile 19B: BX-geogrid 330 th St Drainage 320 th St tiles 310 th St Hamilton County Demo Project Li et al. (2015) 7

8 This presentation will show comparisons between the geocomposite section and control sections. (a) Geocomposite 6 in. road stone 2 to 5 in. road stone (b) Subgrade Subgrade Geocomposite Section 18 Control Section 10, 14, and 20 Macdrain W1051 geocomposite (a) top view and (b) side view 8

9 Installation of the geocomposite drainage layer for granular surfaced roads was easy and fast. 1. Remove existing surface aggregate 2. Lay geocomposite 3. Replace surface aggregate 4. Spread and compact surface aggregate The section was constructed on June 5 and 6,

10 Large-scale HPTs were performed to measure the permeability of soils under horizontal flow conditions manometer connected to the soil tank Soil Tank Flow Tank Water Reservoir Grit Tank Water Pump 10

11 Geocomposite drainage layer was placed at the mid-depth of the specimen. (a) (b) (d) (e) (c) (f) 11

12 Geocomposite increased the horizontal K sat of the surface aggregate by three orders of magnitude Existing surface aggregate Macdrain W1051 Test 1 Macdrain W1051 Test 2 Macdrain W1051 Test 3 K 68 o F, ft / day Hydraulic Gradient, i 12

13 APT tests were performed to measure the in situ K sat of the geocomposite and control sections. Air permeability test (APT) (White et al. 2014, White et al. 2007) 13

14 The APT tests were performed to measure the change of K sat with depth in the surface course layer. Depth (in) Geocomposite Drain Section (18) Location 1 Location 2 Location 3 Surface Aggregate W1091 Geocomp. Subgrade Surface Aggregate W1091 Geocomp. Subgrade Surface Aggregate W1051 Geocomp. Subgrade Distance from South End of the Section (ft) Depth (in) Control Section (17 Before Construction) Location 1 Location 2 Location 3 Surface Aggregate Subgrade Surface Aggregate Subgrade Surface Aggregate Subgrade Distance from South End of the Section (ft) The APT tests were performed on July 10,

15 APT test results showed that the geocomposite significantly improves the drainage conditions. Depth (in) Control Loaction 1 Control Location 2 Control Location 3 Geocomp. Location 1 Geocomp. Location 2 Geocomp. Location K sat (ft/day) 15

16 A 2-D water infiltration model was used to evaluate performance of geocomposite under transient flow conditions. Assumptions: Isotropic and homogeneous soil Richards Equation Haverkamp s WRC model Soil Properties Residual water content cm 3 /cm 3 Saturated water content cm 3 /cm 3 Initial water content 0.08 cm 3 /cm 3 Initial matric potential K sat cm cm/s K vertical = K horizontal Rainfall direction is always perpendicular to the roadway surface 16

17 Rainfall condition and modeling time used for the 2-D model: Rainfall rate: 5 in/hr (< K sat of the soil = 5.7 in/hr) Rainfall time: 1800 sec. (0.5 hr) Modeling time: 5400 sec. (1.5 hr) Time step: 0.25 sec. 17

18 The road surface crown cannot significantly improve the drainage condition under a transient flow. Control (Slope=0%) Control (Slope=4%) 18

19 The road surface crown cannot significantly improve the drainage condition under the transient flow. Control (Slope=0%) Control (Slope=4%) 19

20 The geocomposite drainage layer can quickly remove water from the surface aggregate layer. Control (Slope=4%) Geocomposite drain (Slope=4%) 20

21 The geocomposite drainage layer can quickly remove water from the surface aggregate layer. Control (Slope=4%) Geocomposite drain (Slope=4%) 21

22 FWD tests were performed to measure the in situ stiffness of the geocomposite and control sections. Falling weight deflectometer (FWD) test 22

23 FWD tests showed that the geocomposite did not increase the stiffness of the section. E FWD-Composite (ksi) Note: The elastic modulus are calculated under lb applied load S11 Control S14 Control High Median Low n=5 n=5 n=3 n=5 S20 Control S18 Geocomposite FWD tests performed October 20,

24 FWD full time history may indicate the geocomposite section had higher M r and lower permanent strain. Impact load, kips Note: The tests were performed at different locations for each section MM rr = σσ dd / εε rr σσ dd? Geocomposite Section 18 Control Section εε pp? εε rr? Deflection at the center of the FWD loading plate, mils 24

25 Survey photos after a rainfall event (09/02/2014) S 10 Control S 14 Control S 18 Geocomposite S 20 Control 25

26 Survey photos after a short period of unusually warm weather (01/20/2015) S 10 Control S 14 Control S 18 Geocomposite S 20 Control 26

27 Survey photos after seasonal thawing period (04/21/2015) S 10 Control S 10 Control S 14 Control S 18 Geocomposite S 18 Geocomposite S 20 Control 27

28 Construction costs for the geocomposite section were approximately $10 per square yard. Construction Costs ($/sq. yd) #7 RPCC #6 Clean #5 Clean #4 Dirty Macadam+Geotextile+Bentonite #3 Dirty Macadam+Geotextile #2 Dirty Macadam+Calcium Chloride #1B Dirty Macadam+Bentonite #1A Dirty Macadam Labor and Equipment Macadam Gravel Geosynthetic Chemical Stabilizer #19B #19A Geogrid+Geotextile #18 Geocomposite #17 Cement #16 Fly Ash #15 Bentonite #13 Aggregate #12 Aggregate Columns+Geocomp. Lining #8 RPCC Macadam+Geotextile 28

29 Works cited Li, C., Ashlock, J., White, D. J., Vennapusa, P. (2015). Low-Cost Rural Surface Alternatives: Demonstration Project. IHRB Project TR-664, Iowa State University, Ames, IA, 242p. White, D. J., Vennapusa, P., and Zhao, L. (2014). "Verification and repeatability analysis for the in situ air permeameter test." Geotechnical Testing Journal, 37(2). White, D. J., Vennapusa, P. K. R., Suleiman, M. T., and Dahren, C. T. (2007). "An in-situ device for rapid determination of permeability for granular bases." Geotechnical Testing Journal, 30(4),