1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

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

9. 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

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

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

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

13. 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

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

15. 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

16. 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

17. 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

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

19. 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

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