UPDATE ON FHWA’S IN-SITU SCOUR TESTING DEVICE (ISTD) National Hydraulic Engineers Conference Portland, OR August 9 – 12, 2016 In-situ Scour Testing Device Research

Concept of Soil Erosion Resistance Level 1: Using current assumptions of uniform soil (e.g. D50) Factored Resistance Nominal Resistance Factored Erosion Force 𝜇+2𝜎 𝜇−2𝜎 𝜇 True ys ASSUMED UNIFORM SOIL Estimated ys Level 1 Uncertainty y Hydraulic Loading and Soild Erosion Resistance

Concept of Soil Erosion Resistance Level 2: Soil Erosion Resistance Data from Historical Records Boring Logs from Historical Records Factored Resistance Nominal Resistance Factored Erosion Force 𝜇+2𝜎 𝜇−2𝜎 𝜇 True ys Estimated ys Level 2 Uncertainty y Hydraulic Loading and Soild Erosion Resistance

Concept of Soil Erosion Resistance Level 3: Soil Erosion Resistance from Geotechnical Properties Soil Erosion Resistance = f (PI, Cu, …) Factored Resistance Nominal Resistance Factored Erosion Force 𝜇+2𝜎 𝜇−2𝜎 𝜇 True ys Estimated ys Level 3 Uncertainty y Hydraulic Loading and Soild Erosion Resistance

Concept of Soil Erosion Resistance Level 4: Soil Erosion Resistance from Lab Erosion Testing Shelby Tube Sample for Lab Erosion Testing Factored Resistance Nominal Resistance Factored Erosion Force 𝜇+2𝜎 𝜇−2𝜎 𝜇 True ys Estimated ys Level 4 Uncertainty y Hydraulic Loading and Soild Erosion Resistance

Concept of Soil Erosion Resistance Level 5: Soil Erosion Resistance from In-situ Scour Testing Devices Factored Resistance Nominal Resistance Factored Erosion Force 𝜇+2𝜎 𝜇−2𝜎 𝜇 True ys Estimated ys Level 5 Uncertainty y Hydraulic Loading and Soild Erosion Resistance

IN-SITU SCOUR TESTING DEVICE (ISTD) Determine critical shear of fine-grained cohesive soils Difficult due to large influences at the molecular level Current Approaches: Erosion Resistance Categories: based on general soil description; very broad range of critical values (X10) Empirical Relationships: based on specific soil properties; limited soil types tested, large error possible Site/depth-specific soil sampling and lab testing: more accurate, but data is discontinuous with depth In-situ testing: most accurate and data continuous with depth In-situ Scour Testing Device Research

In-situ Scour Testing Device Concept (Patented) A-A B-B B In-situ Scour Testing Device Research 8

In-situ Scour Testing Device Concept (Patented) Water tank Erosion pump Sample casing Level pump Erosion head River water level Reel Top tank Level pump Sample casing Water tank Erosion pump O-ring sealing River water level Reel Top tank Radial flow at erosion head Compatible with standard drill equipment Test desired location & depth Minimum disturbance to soil System automated Suction system Pressure system 9

In-situ Scour Testing Device (Patented) In-situ Scour Testing Device Research 10

In-situ Scour Testing Device Research Drill rig In-situ Scour Testing Device Research 11

In-situ Scour Testing Device Concept In-situ Scour Testing Device Research 12

In-situ Scour Testing Device - Proof of Concept Drill drive shaft Erosion head Water supply tank Linear drive Drill casing Head box In-situ Scour Testing Device Research

In-situ Scour Testing Device - Proof of Concept In-situ Scour Testing Device Research 14

In-situ Scour Testing Device - Proof of Concept Results Erosion rate 1.0 mm/min 2.1 mm/min 0.5 mm/min 2.3 mm/min In-situ Scour Testing Device Research 15

In-situ Scour Testing Device – General Field Procedure 1. Pretest boring 2. Bore log review 3. Drill to a specified depth (Hollow-stem auger advancing with steel casing) 4. Advance steel casing into soil 5. Detach drill rig and setup erosion head with linear actuator 6. Erosion test for the soil inside steel casing 7. Connect additional auger and steel casing sections Repeat until maximum depth reached In-situ Scour Testing Device Research 16

In-situ Scour Testing Device Gen 2 Erosion Head OUT In-situ Scour Testing Device Gen 2 Erosion Head In-situ Scour Testing Device Research 17

In-situ Scour Testing Device - Gen 3 Erosion Head In-situ Scour Testing Device Research 18

In-situ Scour Testing Device - Calibration Erosion rate ESTD Shear (τ) Lab-ISTD Flow (Q, gap) Lab-ISTD flow (Q, gap) ESTD shear (τ) In-situ Scour Testing Device Research 19

In-situ Scour Testing Device QUESTIONS? In-situ Scour Testing Device Research 20