Comprehensive Material Characterizations for a Pavement Embankment Installed with Wicking Fabric Chuang Lin Ph.D. Student Xiong Zhang Associate Professor University of Alaska Fairbanks Jie Han Professor University of Kansas August 3, 2015
Outline Introduction New Geotextile with Wicking Ability Material Characterizations Applications Conclusions 2
Conventional Drainage Design 3
Conventional Drainage Design Drainage Materials Gravel, coarse sand and geotextile Capillary barrier to stop water from flowing upward Potential Issues Only drains free water or gravitational water Cannot drain water under unsaturated conditions Soil water content eventually increase with time 4
New Drainage Design Concept Suction > 140 MPa (RH < 90%) Asphalt Concrete Suction > 140 MPa (RH < 90%) Wicking Wicking Fabric Fabric Relatively Dry Air-Dry Surface (Impermeable) 5
New Geotextile with Wicking Ability Reinforcement Drainage Dia.: 5.7-47.8 μm Specific Area: 3650 cm 2 /g Permittivity: 611 l/min/m 2 6
Geotextile with Wicking Ability RH= 50% 1.86 m in 983 mins 7
Geotextile with Wicking Ability 8
Geotextile Specifications Mechanical Properties Test Method Unit Average Roll Value Tensile Modulus @ 2% Strain (CD) ASTM D4595 kn/m 657 Permittivity ASTM D4491 Sec -1 0.24 Flow Rate ASTM D4491 l/min/m 2 611 Pore Size (O50) ASTM D6767 microns 85 Pore Size (O95) ASTM D6767 microns 195 Apparent Opening Size (AOS) ASTM D4751 mm 0.43 Tested Value Wet Front Movement (24 minutes) ASTM C1559 inches 6.0 Vertical Direction Wet Front Movement (983 minutes) Zero Gradient ASTM C1559 inches 73.3 Horizontal Direction 9
Comparison in Road Conditions May 12, 2010 May 24, 2011 Beaver Slide 10
Comparison in Road Conditions Without Geotextile Installed Coldfoot, AK 11
Comparison in Road Conditions With Geotextile Installed Coldfoot, AK 12
Problem Statement What types of soils is the geotextile applicable for To what extent can the pavement structure water content be reduced to How to quantify the improved pavement performance What is the geotextile functional working range 13
Material Characterizations Soil Characterization Wicking Fabric Characterization Soil-Geotextile Interaction Potential Issue: Clogging Effect 14
Soil Basic Properties Soil Type: AB-3 Base Course About 8.5%-10% of Fines in the Soil Optimum Water Content: 8.5% Maximum Dry Density: 2.2 10 3 kg/m 3 15
Resilient Modulus, MR ( MPa) Resilient Modulus Test 2500 2000 WC = 10.8% WC = 8.9% WC = 6.9% WC = 3.8% WC = 2.1% WC = 0% 1814 1657 1889 1768 2091 1500 1000 500 0 1066 1156 1010 944 1006 1030 895 920 916 841 553 633 463 333 363 185 3554 56 98 159 209 86 20.7 34.5 68.9 103.4 137.9 Confining Pressure (kpa) 16
Permanent Deformation (mm) Permanent Deformation 14 12 12.0 10 8 8.2 6 4 2 0 2.5 1.2 1.4 0.3 0.5 0.0 2.1 3.9 6.8 8.8 9.5 10.8 Water Content (%) 17
Water Content (%) SWCC and GWCC 35 30 25 20 15 10 Geotextile Inter-Yarn Air Entry Value 8.5 % Geotextile Water Charateristic Curve Soil Water Characteristic Curve Pressure Plate Test (Soil) Pressure Plate Test (Geotextile) Salt Concentration Test (Geotextile) Salt Concentration Test (Soil) Geotextile Inner-Yarn Air Entry Value 5 6.5 % 0 30 200 1 10 100 1000 10000 Suction (KPa) 18
Shear Stress, τ (kpa) Soil-Geotextile Interaction 250 200 τ = 0.93σ φ = 42.9 (WC = 0 %) τ = 1.09σ φ = 47.5 (WC = 2 %) τ = 1.03σ φ = 45.8 (WC = 4 %) τ = 0.94σ φ = 43.2 (WC = 6 %) τ = 0.87σ φ = 41.2 (WC = 8 %) 150 100 50 0 0 % 2 % 4 % 6 % 8 % 10.5 % 0 50 100 150 200 250 Normal Stress, σ (kpa) Large-Scale Direct Shear Test 19
Potential Issue: Clogging Effect Wicking Fabric with Dry Soil Wicking Fabric with Soil Slurry 20
Water Content (%) Applications Suction > 140 MPa (RH < 90%) Surface Suction 30 kpa Asphalt Concrete Suction > 140 MPa (RH < 90%) Wicking Wicking Fabric Fabric Relatively Dry Suction 200 kpa Air-Dry Surface (Impermeable) Suction Contour with Geotextile (-) 35 Suction Contour without Geotextile (+) 30 25 20 15 10 8.5 % Geotextile Water Charateristic Curve Soil Water Characteristic Curve Pressure Plate Test (Soil) Pressure Plate Test (Geotextile) Salt Concentration Test (Geotextile) Salt Concentration Test (Soil) Geotextile Inner-Yarn Air Entry Value 5 0 6.5 % 30 200 1 10 100 1000 10000 21 Suction (KPa)
Applications Test Results Summary 22
Conclusions Excess water causes severe issues and conventional drainage material cannot drain water under unsaturated conditions New drainage design concept to use natural environment as pump to continuously wick water out of the pavement embankment the new geotextile with wicking ability works effectively for soils with particle size greater than 12 μm 23
Conclusions The functional suction range for the geotextile can be as high as 200 kpa For the tested soil, the geotextile can reduce the water content by 2%. By dong so, the resilient modulus increased by 3 times and the permanent deformation decreased to half Interface shear strength is not sensitive to water content variation 24
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