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Relationship Between Erodibility and Properties of Soils (2019)

Chapter: Chapter 4. Erosion Experiments

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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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Suggested Citation:"Chapter 4. Erosion Experiments." National Academies of Sciences, Engineering, and Medicine. 2019. Relationship Between Erodibility and Properties of Soils. Washington, DC: The National Academies Press. doi: 10.17226/25470.
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76 CHAPTER 4 4. EROSION EXPERIMENTS This chapter presents the results of all the erosion experiments performed as part of this NCHRP project. Section 4.1 of this chapter is dedicated to the Soil Erosion Laboratory at Texas A&M University, and the testing devices that were built as part of this project. The design plans as well as photographs of each device that was built is presented in this section. Section 4.2 presents the erosion test plan matrix in this project, and Section 4.3 presents the results of erosion experiments (i.e. Mini-JET, EFA, HET, PET, and BET). Finally, Section 4.4 presents the comprehensive information on the geotechnical properties of all tested samples. Appendix 1 and Appendix 2 of this report, include all detailed erosion test results, and the geotechnical properties spreadsheets for each sample, respectively. Also, from each sample that was tested in any erosion device, many photographs and videos were taken before, during, and after the tests. The photographs and videos are collected in a file and held by the authors. 4.1. TAMU Erosion Lab and Testing Devices The very primary step to perfom the erosion tests in this study was to furnish the erosion lab with all necessary testing equipment and work condition at Texas A&M University. Therefore, a Hole Erosion Test (HET) and a Jet Erosion Testing device were constructed in the lab. Also, the two Erosion Function Apparatus (EFA) machines at Texas A&M University were re-furnished and armored into proper condition. Following is the summary of the work done on the construction of each aforementioned device, and the refurbishment of the Soil Erosion Laboratory at Texas A&M University. Construction of the Hole Erosion Test (HET) Apparatus The HET apparatus was constructed at Texas A&M University in accordance with the work done by Wan and Fell (2002) at the University of New South Wales in Australia. A schematic diagram of this device, along with the design drawings are included in Figure 37 to Figure 41. A couple of dummy tests were also conducted to make sure that the constructed apparatus is ready for the testing schedule. Figure 42 shows a final version of the HET apparatus in the soil erosion lab at Texas A&M University, with labels describing each piece.

77 Figure 37. Schematic of the Hole Erosion Test assembly (Wan and Fell, 2002)

78 Figure 38. Drawing of the whole assembly in one glance (all dimensions are in mm) C.L. CROSS SECTION A-A LONGITUDINAL SECTION Left Cylinder Right Cylinder 25 .5 25.5 63.5 50. 8 55.5 56 .5 53 .0 A A 18 0. 0 180.0 90.0 90 .0 20 mm THK PERSPEX END PLATE 12 mm DIA. HOLE FOR 10 mm DIA. THE BOLT 3 mm DEEP RECESS 12 mm DIA. HOLE FOR MONOMETER 12 mm DIA. HOLE FOR AIR RELEASE VALVE Part A Part B Part C

79 Figure 39. Drawings associated with the “Part A: End Plate” (all dimensions are in mm) 17 .5 12.0 18 0. 0 180.0 90.0 90 .0 20 mm THK PERSPEX END PLATE 12 mm DIA. HOLE FOR 10 mm DIA.THE BOLT 3 mm DEEP RECESS 25 .5 25.5 16 mm THK 180x180 PERSPEX END PLATE 35 mm DIA. HOLE FOR OUTLET PIPE 12 mm DIA HOLE FOR 10 mm DIA. TIE BOLT 58 .5 12 .0 19 .5 3.0 63.5 16.0 12 .7 Without DimensionsWith Dimensions A A CROSS SECTION A-A LONGITUDINAL SECTION A A 50 .8 50. 8

80 Figure 40. Drawings associated with the “Part B: Middle Cylinder” (all dimensions are in mm) 63.5 3 mm DEEP RECESS 12 mm DIA. HOLE FOR MONOMETER 12 mm DIA. HOLE FOR AIR RELEASE VALVE 63 .5 12 mm DIA. HOLE FOR MANOMETER PERSPEX CYLINDER 101.6 mm INTERNAL DIA. 12 mm DIA. HOLE FOR AIR RELEASE VALVE 17.0 3.0 4. 7 50. 8 12 .7 3.0 50 .8 A A 55.5 Without DimensionsWith Dimensions A A CROSS SECTION A-A LONGITUDINAL SECTION

81 Figure 41. Drawings associated with the “Part C: Inlet Plate” (all dimensions are in mm) 18 0. 0 180.0 90.0 90 .0 20 mm THK PERSPEX END PLATE 12 mm DIA. HOLE FOR 10 mm DIA. THE BOLT 63.5 50. 8 55.5 56 .5 A A 3 mm DEEP RECESS 25 .5 25.5 Without DimensionsWith Dimensions A A CROSS SECTION A-A LONGITUDINAL SECTION 50 .8 55 .5 53 .01 2. 0 23.0 53 .0 26 .5 3.08.0 3. 5

82 Figure 42. Photos taken from the HET assembly at Texas A&M University Construction of the Mini-JET Apparatus The core part of the mini JET device was obtained from Dr. Garey Fox, professor in the Biosystems and Agricultural Engineering Department at Oklahoma State University. The JET test assembly was then constructed in the erosion lab at Texas A&M University (Figure 43). A couple

83 of dummy tests were also conducted to ensure that there is no considerable leakage and hindrance with the testing process. Figure 43 shows some photos taken from the JET assembly with labels describing each piece. Figure 43. Photos taken from the JET assembly at Texas A&M University Refurbishment of the EFA machines and the TAMU Erosion Lab There are two EFAs in the TAMU Soil Erosion Laboratory. Both machines were repaired and upgraded for the second phase of the project. Figure 44 shows some photos of the erosion laboratory, the control desk, and the two EFAs. The difference between the two EFAs is the way the sample extrusion is controlled. In the EFA #1 shown in Figure 44, the test operator needs to extrude the sample from the tube manually by pushing the button on the control board of the EFA, while in the EFA #2 the extrusion is controlled through the desktop on the control desk; however, one of the operators still need to stand by the EFA to monitor if there is any scour on the sample. Figure 44 shows the general view of the erosion lab as well as the two EFA machines.

84 Figure 44. Erosion laboratory at Texas A&M University, showing the two EFAs and the control desk 4.2. Test Plan Matrix As discussed earlier in Chapter 1, the majority of the erosion tests proposed in this study consists of laboratory tests using the devices developed in the soil erosion laboratory at Texas A&M University. The remaining are associated with the field tests which were conducted on the clay and sand sites located at the RELLIS Campus at Texas A&M University. A total 168 new erosion tests were planned to be performed during this project. Table 16 shows the experimental plan proposed for this project. A testing matrix was proposed in order to perform all erosion tests in accordance with the progress schedule timeline of the project. Table 17 shows the proposed testing matrix for this project.

85 Table 16. Experimental test plan proposed for this project TASK SOIL TYPE TYPE OF TESTS TOTAL NUMBER OF TESTS Compare different devices 1 Clay (man-made) 1 Silt (man-made) 1 Sand (man-made) 1 Gravel (man-made) EFA JET HET PET 16 Check repeatability of results 1 Clay (man-made) 1 Silt (man-made) 1 Sand (man-made) 1 Gravel (man-made) EFA JET HET PET 16 Organize field erosion devices demonstration and comparison 1 Clay 1 Sand PET BET ISEEP ISTD 8 Erosion tests to develop the equations 14 Clays EFA HET JET PET 56 Erosion tests to develop the equations 8 Silts EFA HET JET PET 32 Erosion tests to develop the equations 6 Sands EFA HET JET PET 24 Erosion tests to develop the equations 4 Gravels EFA HET JET PET 16 Total number of tests Clays, Silts, Sands, Gravels EFA JET HET PET BET ISEEP ISTD 168

86 Table 17. Testing matrix for this project FY TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # FY TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # TIME FRAME TASK # Texas A&M University System Iman SHAFII 24-43 Week 4 (10/22 to 10/29)Week 3 (10/14 to 10/21)Week 2 (10/7 to 10/14)Week 1 (9/29 to 10/7) Percent completed? ►►► TARGET Perform erosion tests with different devices using the same prepared soil 100 100 100 100 October 30th to November 30th 4 1 EFA, 1 JET, 1 HET, 1 PET on same as above Clay 1 EFA, 1 JET, 1 HET, 1 PET on same as above Silt 1 EFA, 1 JET, 1 HET, 1 PET on same as above Sand 1 EFA, 1 JET, 1 HET, 1 PET on same as above Gravel 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Sand 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Gravel4September 30th toOctober 30th TARGET Check repeatability of results Percent completed? ►►► 100 100 100 100 TARGET Week 1 (11/29 to 12/7) Week 2 (12/7 to 12/14) Week 3 (12/14 to 12/21) Week 4 (12/22 to 12/29) Week 1 (10/29 to 11/7) Week 2 (11/7 to 11/14) Week 3 (11/14 to 11/21) Week 4 (11/22 to 11/29) 1 BET, (possibly 1 ISTD) on sand site in RELLIS Campus w/ associated soil properties Percent completed? ►►► 100 100 100 100 November 30th to December 30th 4 Organize field erosion devices demonstraation and comparison 1 PET, (possibly 1 ISEEP) on clay site in RELLIS Campus w/ associated soil properties 1 PET, (possibly 1 ISEEP) on sand site in RELLIS Campus w/ associated soil properties 1 BET, (possibly 1 ISTD) on clay site in RELLIS Campus w/ associated soil properties TARGET Week 1 (12/28 to 1/5) Week 2 (1/5 to 1/14) Week 3 (1/14 to 1/21) Week 4 (1/22 to 1/29) December 30th to January 30th 5 Erosion tests to develop the equations (14 clay samples) Holidays (Christmas Break) 1 EFA, 1 JET, 1 HET, 1 PETw/ soil properties on Clay #1 January 30th to February 30th 5 Erosion tests to develop the equations (14 clay samples) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #4 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #5 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #2 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #3 Percent completed? ►►► 100 100 100 100 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #6 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #7 Percent completed? ►►► 100 100 100 100 TARGET Week 1 (1/29 to 2/7) Week 2 (2/7 to 2/14) Week 3 (2/14 to 2/21) Week 4 (2/22 to 2/29) Week 1 (2/29 to 3/7) Week 2 (3/7 to 3/13) Week 3 (3/13 to 3/19) Week 4 (3/19 to 3/29) February 30th to March 30th 5 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #8 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #9 Holidays (Spring Break) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #10 Erosion tests to develop the equations (14 clay samples) Percent completed? ►►► TARGET 100 100 100 100 TARGET Week 1 (3/29 to 4/7) Week 2 (4/7 to 4/14) Week 3 (4/14 to 4/21) Week 4 (4/22 to 4/29) April 30th to May 30th 5 Erosion tests to develop the equations (8 silt samples) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #1 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #2 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #14 Percent completed? ►►► 100 100 100 100 March 30th to April 30th 5 Erosion tests to develop the equations (14 clay samples) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #11 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #12 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Clay #13 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #3 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #4 Percent completed? ►►► 100 100 100 100 TARGET Week 1 (4/29 to 5/7) Week 2 (5/7 to 5/14) Week 3 (5/14 to 5/21) Week 4 (5/22 to 5/29) TARGET Week 1 (5/29 to 6/7) Week 2 (6/7 to 6/14) Week 3 (6/14 to 6/21) Week 4 (6/22 to 6/29) May 30th to June 30th 5 Erosion tests to develop the equations (8 silt samples) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #5 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #6 June 30th to July 30th 5 Erosion tests to develop the equations (6 sand samples) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Sand #1 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Sand #2 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #7 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Silt #8 Percent completed? ►►► 100 100 100 100 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Sand #3 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Sand #4 Percent completed? ►►► 100 100 100 100 TARGET Week 1 (6/29 to 7/7) Week 2 (7/7 to 7/14) Week 3 (7/14 to 7/21) Week 4 (7/22 to 7/29) TARGET Week 1 (7/29 to 8/7) Week 2 (8/7 to 8/14) Week 3 (8/14 to 8/21) Week 4 (8/22 to 8/29) July 30th to August 30th 5 Erosion tests to develop the equations (finish 6 sands, start on 4 gravel samples) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Sand #5 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Sand #6 Erosion tests to develop the equations (4 gravel samples) 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Gravel #3 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Gravel #4 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Gravel #1 1 EFA, 1 JET, 1 HET, 1 PET w/ soil properties on Gravel #2 Percent completed? ►►► 100 100 100 100 2017 2016 NCHRP Project No. Research Agency Laboratory Leader NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM TRANSPORTATION RESEARCH BOARD NATIONAL RESEARCH COUNCIL TESTING MATRIX Percent completed? ►►► 100 100 TARGET Week 1 (8/29 to 9/7) Week 2 (9/7 to 9/14) July 30th to August 30th 5

87 4.3. Results of Erosion Tests This section presents the results of all the erosion tests performed during this project. As discussed in the previous section, the used erosion test devices include EFA, JET, HET, PET, and BET. Also, the detailed information on the geotechnical properties of all tested samples are presented in Section 4.4. Ensuring the Repeatability of Erosion Tests and Field Demonstration The two major missions of this section are: 1) Testing the same soil with different erosion testing devices (i.e. EFA, JET, HET, PET) to evaluate the repeatability of the results for each erosion test. 2) Organizing field demonstration tests including the PET, and the BET. For the purpose of ensuring the repeatability of the erosion tests, all four types of soils (i.e. gravel, sand, silt, clay) are prepared (man-made samples) and tested using EFA, JET, HET, and PET. Table 18 shows the primary description of the soils that are tested for the purpose of ensuring repeatability. Thirty-two samples (Table 18) were tested. The first letter in the sample name refers to the first letter of the soil type. The second letter refers to the first letter of each apparatus type. The number at the end of the sample name is “1” if the sample is tested for the first time, and “2” if it is tested for the second time to ensure repeatability. For example, CJ-2 means that the sample is a clay which is tested by JET for the second time to evaluate the repeatability of this device. Table 18. Description of the soils used to ensure repeatability of erosion tests Soil Type Description Erosion Test Sample Name Target Water Content (%) Target Wet Unit Weight (kN/m3) Gravel Pea Gravel from Lowes HET JET EFA PET GH-1 & GH-2 GJ-1 & GJ-2 GE-1 & GE-2 GP-1 & GP-2 10% 20 Sand Mixture of (20% Bentonite+ 80% Silica Sand 60-80) from Armadillo Clay & Supplies Co. in Austin HET JET EFA PET SH-1 & SH-2 SJ-1 & SJ-2 SE-1 & SE-2 SP-1 & SP-2 10% 19 Silt Porcelain Grolleg Kaolin from Armadillo Clay & Supplies Co. in Austin HET JET EFA PET MH-1 & MH-2 MJ-1 & MJ-2 ME-1 & ME-2 MP-1 & MP-2 18% 16 Clay Mixture of (60% Porcelain Grolleg Kaolin + 40% Bentonite) from Armadillo Clay & Supplies Co. in Austin HET JET EFA PET CH-1 & CH-2 CJ-1 & CJ-2 CE-1 & CE-2 CP-1 & CP-2 15% 14

88 The results of the work done to check the repeatability of erosion tests for each sample is described as listed below in the following sections. 4.3.1.1. Ensuring repeatability of the Erosion Function Apparatus (EFA) - Ensuring the repeatability of EFA for the clay sample - Ensuring the repeatability of EFA for the silt sample - Ensuring the repeatability of EFA for the sand sample - Ensuring the repeatability of EFA for the gravel sample 4.3.1.2. Ensuring repeatability of the Pocket Erodometer Test (PET) - Ensuring the repeatability of PET for the clay sample - Ensuring the repeatability of PET for the silt sample - Ensuring the repeatability of PET for the sand sample - Ensuring the repeatability of PET for the gravel sample 4.3.1.3. Ensuring repeatability of the Jet Erosion Test (JET) - Ensuring the repeatability of JET for the clay sample - Ensuring the repeatability of JET for the silt sample - Ensuring the repeatability of JET for the sand sample - Ensuring the repeatability of JET for the gravel sample 4.3.1.4. Ensuring repeatability of the Hole Erosion Test (HET) - Ensuring the repeatability of HET for the clay sample - Ensuring the repeatability of HET for the silt sample - Ensuring the repeatability of HET for the sand sample - Ensuring the repeatability of HET for the gravel sample Ensuring the repeatability of the EFA Clay Samples (CE-1 & CE-2) The prepared clay samples were a mixture of 60% Porcelain Grolleg Kaolin plus 40% Bentonite purchased from Armadillo Clay & Supplies Co. in Austin. Both samples were remolded and compacted to re-produce the target condition in Table 18. Results of the EFA tests on CE-1 and CE-2 are presented in Figure 45 and Figure 46 against velocity and shear stress, respectively. Both samples can be categorized as Medium Erodibility Category (III). The critical velocities for CE-1 and CE-2 are 1.18 and 1.04 m/s, respectively. The critical shear stress values are also measured as 7.59 and 5.93 Pa for CE-1 and CE-2, respectively. The results of each EFA test is also presented in the format of an “EFA result spreadsheet” in Appendix 1. Figure 47 shows an example of the EFA result spreadsheet for the sample CE-1.

89 a) Logarithmic scale b) Natural scale Figure 45. EFA test results based on velocity for ensuring the repeatability of the EFA on clay samples a) Logarithmic scale b) Natural scale Figure 46. EFA test results based on shear stress for ensuring the repeatability of the EFA on clay samples Silt Samples (ME-1 & ME-2) Silt samples were 100% Porcelain Grolleg purchased from Armadillo Clay & Supplies Co. in Austin. Both samples were remolded and compacted to re-produce the target condition described in Table 18. Results of the EFA tests on ME-1 and ME-2 are presented in Figure 48 and Figure 49 against velocity and shear stress, respectively. Both samples can be categorized as in the High to Medium Erodibility Category (II to III). The critical velocities for ME-1 and ME-2 are 0.1 m/s. The critical shear stress values are also measured as 0.1 Pa.

90 Figure 47. EFA result spreadsheet for CE-1 a) Logarithmic scale b) Natural scale Figure 48. EFA test results based on velocity for ensuring the repeatability of the EFA on silt samples

91 a) Logarithmic scale b) Natural scale Figure 49. EFA test results based on shear stress for ensuring the repeatability of the EFA on clay samples Sand Samples Sand samples were a mixture of (20% Bentonite+ 80% Silica Sand 60-80) both purchased from Armadillo Clay & Supplies Co. in Austin. Both samples were remolded and compacted to re- produce the target condition described in Table 18. Results of the EFA tests on SE-1 and SE-2 are presented in Figure 50 and Figure 51 against velocity and shear stress, respectively. Both samples can be categorized as Medium Erodibility Category (III). a) Logarithmic scale b) Natural scale Figure 50. EFA test results based on velocity for ensuring the repeatability of the EFA on sand samples

92 a) Logarithmic scale b) Natural scale Figure 51. EFA test results based on shear stress for ensuring the repeatability of the EFA on sand samples Gravel Samples Gravel samples were Pea Gravel purchased from Lowes in College Station. Both samples were remolded and compacted to re-produce the target condition described in Table 18. Results of the EFA tests on GE-1 and GE-2 are presented in Figure 52 and Figure 53 against velocity and shear stress, respectively. Both samples can be categorized as in the Medium to low Erodibility Category (III to IV). The critical velocities for GE-1 and GE-2 are 1.44 and 1.5 m/s. The critical shear stress values are also measured as 17.63 and 19.13 Pa. a) Logarithmic scale b) Natural scale Figure 52. EFA test results based on velocity for ensuring the repeatability of the EFA on gravel samples

93 a) Logarithmic scale b) Natural scale Figure 53. EFA test results based on shear stress for ensuring the repeatability of the EFA on gravel samples Ensuring the repeatability of the PET The pocket erodometer test (PET) was performed on the top surface of each sample prior to each EFA test. As discussed earlier in Chapter 2, the PET consists of applying 20 times a jet of water at 8 m/s by squeezing the trigger of a water pistol positioned 50 mm from the sample face. The jet hits the sample surface at the same location at one end of the sample. The depth of the hole formed on the sample surface is then measured and entered in the PET erosion categories chart. The PET was conducted three times at different location on the top end of each sample. Results of the PET test are shown in Table 19. Results show a reasonable repeatability for each soil type. It is worth noting that performing the PET on gravel samples is not feasible. Table 19. Results of the Pocket Erodometer Test (PET) on each sample Clay Samples Silt Samples Sand Samples Gravel Samples CP-1 CP-2 MP-1 MP-2 SP-1 SP-2 GP-1 GP-2 2.11 mm 3.0 mm 5.33 mm 5.3 mm 5.4 mm 4.22 mm Not Applicable As discussed in Chapter 2, Results of the PET can be associated with the erosion category chart (Figure 54). All the points fall in the Medium Erodibility (III) category on this chart. Comparing this result with the results of EFA test shows a compliance between the two tests.

94 Figure 54. Erosion categories for the tested samples according to the PET Category Chart Ensuring the repeatability of the HET Clay Samples (CH-1 & CH-2) As said earlier, clay samples were a mixture of 60% Porcelain Grolleg Kaolin plus 40% Bentonite purchased from Armadillo Clay & Supplies Co. in Austin. Results of the HETs on CH- 1 and CH-2 are presented in Figure 55 and Figure 56, respectively. Please note that the HET results are plotted as erosion rate (mm/hr) against hydraulic shear stress. HET plots include several fluctuations due to the errors associated with the constant head system both upstream and downstream. Note that Wan and Fell (2002) had the same type of curves and fitted a best line on each plot and estimated the critical shear stress in that fashion. The critical shear stress values are also measured as 70 and 67 Pa for CH-1 and CH-2, respectively. As explained in Chapter 2, HET results start with a decrease in erosion rate with an increase in shear stress; thereafter, both erosion rate and shear stress start increasing. The first part of the curve is typically attributed to the thickness of the disturbed zone due to drilling the 6 mm hole in the center of the sample. The second part of the curve corresponds to the erosion of the undisturbed soil. To predict the critical shear stress, the erosion part of the fitted erosion curve is extended (see the dashed tangent line in Figure 55) to cross the horizontal axis. The shear stress associated with the obtained point is the critical shear stress. It should be noted that the dashed line is determined according to the operator’s interpretation. Therefore, the critical shear stress and slope of shear stress in HET are subjective. The erosion part of the CH-1 and CH-2 test result curves were plotted in the erosion category chart. It can be concluded that both samples place in the Low Erodibility category (IV) (Figure 57). The main reason that the curves are in two different shear stress ranges is that the initial head condition for CH-1 and CH-2 were different due to the unexpected change in the test condition at the time of test (815 mm and 360 mm, respectively); however, tracking the erosion part of the curves both crosses the horizontal axis at a critical shear stress of 70 Pa. It is important to notice that higher initial heads in the HET leads to greater shear stress ranges at the soil-water interface. Therefore, the user should be aware of the desired shear stress range before performing HET. For

95 high erodible geomaterials such as silt, the erosion function is better captured in an HET with low initial head; however, for more erosion resistant geomaterials such as dense high plasticity clay, performing the HET with higher initial heads would better capture the erosion function. The results of all HETs are also presented in the format of an “HET result spreadsheet” in Appendix 1. Figure 58 shows an example of the HET result spreadsheet for the sample CH-1. Figure 55. HET data for CH-1

96 Figure 56. HET data for CH-2 Figure 57. Erosion part of the clay HET curves plotted on the Erosion Category Chart Silt Samples (MH-1 & MH-2) As said earlier, silt samples were 100% Porcelain Grolleg Kaolin purchased from Armadillo Clay & Supplies Co. in Austin. Results of the HETs on MH-1 and MH-2 are presented in Figure 59 and Figure 60, respectively. The critical shear stress values are also measured as 50 and 46 Pa for CH-1 and CH-2, respectively. The erosion functions of MH-1 and MH-2 were plotted in the

97 erosion category chart. Erosion curves fall in the Medium Erodibility category (III) (Figure 61). The initial head was 330 and 321 mm for MH-1 and MH-2, respectively. Figure 58. HET result spreadsheet for the sample CH-1

98 Figure 59. HET data for MH-1 Figure 60. HET data for MH-2

99 Figure 61. Erosion part of the silt HET curves plotted on the Erosion Category Chart Sand Samples (SH-1 & SH-2) As said earlier, the sand samples were a mixture of 20% Bentonite plus 80% Silica Sand 60- 80 both purchased from Armadillo Clay & Supplies Co. in Austin. The results of the HETs on SH- 1 and SH-2 are presented in Figure 62 and Figure 63, respectively. The critical shear stress values are also measured as 111 and 108 Pa for CH-1 and CH-2, respectively. For the purpose of comparison and populating the TAMU-Erosion Spread Sheet, the erosion part of the SH-1 and SH-2 test result curves were plotted in the erosion category chart. Both erosion curves fall at the boundary between the Medium and Low Erodibility category (III & IV) (Figure 64). The initial head was 514 and 508 mm for SH-1 and SH-2, respectively. Figure 62. HET result for SH-1

100 Figure 63. HET result for SH-2 Figure 64. Erosion part of the sand HET curves plotted on the Erosion Category Chart Gravel Samples (GH-1 & GH-2) The HET can only be performed in soils where a horizontal hole can hold up and be self- supporting (i.e. fine-grained soils). Therefore, no HET could be conducted for the gravel samples.

101 Ensuring the repeatability of the JET As discussed earlier in Chapter 2, for every Jet Erosion Test (JET) the operator collects the depth of the hole being created at the center of the sample as a function of time under a constant head condition. The collected data are then back analyzed to estimate two main erodibility parameters (critical shear stress and rate of erosion). There are three techniques to interpret the JET results: 1) Blaisdell solution, 2) Scour Depth solution, 3) Iterative solution. Figure 65 shows an example of the reading inputs during a JET, and results of a sample JET spread sheet, respectively. Each method gives a different set of erodibility parameters: critical shear stress (τc), and detachment coefficient (kd). It is the test operator’s duty to find the best solution for interpreting the jet test results. In addition, since one of the goals of this research project is to establish relationships between soil erodibility and engineering properties, it is very important to understand each solution well, and choose a consistent method of data interpretation for all jet test results. Here is a summary of the differences between each interpretation technique: The most established solution in the literature is the Blaisdell solution which was developed and used by Hanson and Cook (1997, 2004). This technique was created based on a hyperbolic function (Blaisdell et al., 1981) to model the development of the scour hole. This report does not intend to go through the details of this hyperbolic function; however, it is worth mentioning that this function employs the real-time depth of the scour hole, and water jet velocity at the jet nozzle to predict the maximum depth of erosion, where the hole stops being eroded. Thereafter, the estimated equilibrium depth is used to measure the critical shear stress (Eq. 57): (57) Where Je is the equilibrium depth, and Jp is the potential core length (nozzle diameter x 6.2). τ0 is the maximum shear stress at the water-soil boundary. Value of kd is then determined using the least squared derivation between the real time and predicted time. Further information is provided in Section 2.1.6. It was found in the literature that this technique highly under predicts the values of τc and kd. After running many jet tests and letting the sample erode until it reaches the equilibrium depth, it was observed that the equilibrium depth estimated using the Blaisdell solution is typically lower than the actual equilibrium depth. This consequently leads to under prediction of the critical shear stress, and subsequently detachment coefficient (kd). The other issue with the Blaisdell solution was the high variability of the critical shear stress (Simon et al., 2010; Cossette et al., 2012). In an effort to improve the Blaisdell solution and reduce the scatter in τc vs. kd, Simon et al., (2010) developed the Iterative solution. In this technique, the results of τc and kd from Blaisdell solution are used for the next iteration to minimize the root mean square deviation between the real time and predicted time; however, many examples have shown that the same variation in results were often observed. The other technique is the Scour Depth solution firstly developed by Daly et al. (2013). The big difference with the other two techniques, is that it solves for kd and τc at the same time. As shown in Figure 65, the plot of scour depth versus time is better predicted using the scour depth

102 solution. In this method, JET should be run until the sample stops eroding in the center (reaches the equilibrium depth). So far, JET results are often reported using the Blaisdell solution technique. However, new studies by Daly et al. (2015) and Khanal et al. (2016) have reported the JET results in form of all three solution techniques. Khanal et al. (2016) have investigated the influence of the operator- dependent variables such as reading intervals, ending time, and pressure head setting on the JET results interpreted through all three solutions. It has been partially concluded that Scour Depth solution gives the most accurate results in terms of scour depth versus time. This solution also makes less assumptions (such as assuming the final equilibrium depth (Je) or predicted time) compared to Blaisdell and Iterative solutions. Due to the fact that it makes less assumptions than the Blaisdell and Iterative solution, the JET results obtained from the scour depth solution was selected and compared to the erosion results obtained from HET or EFA. One of the disadvantages of the scour depth solution however occurs in the case where the soil is very resistant to erosion. In this case, it is rarely possible to end with the equilibrium depth; therefore, the iterative solution is a better solution to predict the subtle changes in scour depth and obtain the equilibrium depth and consequently the erodibility parameters. For this project, the JET results are reported according to all three solutions discussed above. For the regression analyses which are presented in the next chapters, the scour depth solution will be used as the primary solution, unless there is a special case in which the iterative solution or Blaisdell solution are more appropriate to use. a) JET input readings (orange cells are recorded by the operator)

103 b) JET final results Figure 65. Example of the (a) reading inputs during a JET, (b) results of a sample JET spread sheet Clay Samples (CJ-1 & CJ-2) As discussed above JET test data can be reduced using three different techniques: 1) Blaisdell Solution (Hanson and Cook, 2004), 2) Scour Depth Solution (Daly et al. 2013), 3) Iterative Solution (Simon et al. 2010). All three techniques lead to the critical shear stress (τc) and erodibility or detachment coefficient (kd) which is the linear slope of the early part of the erosion curve in the erosion rate-shear stress plot. Table 20 shows the results of the three solutions for CJ-1 and CJ-2. A reasonable repeatability is observed for all three techniques. The results of all JET tests are also

104 presented in the format of a “JET result spreadsheet” in Appendix 1. Figure 66 shows an example of the JET result spreadsheet for the sample CJ-1. Table 20. JET results for the samples CJ-1 and CJ-2 Sample Blaisdell Solution Scour Depth Solution Iterative Solution (Pa) (cm3/N.s) (Pa) (cm3/N.s) (Pa) (cm3/N.s) CJ-1 5.79 0.59 8.80 2.56 5.80 3.82 CJ-2 4.81 0.53 6.74 1.19 4.92 3.76

105 Figure 66. JET result spreadsheet for CJ-1 Silt Samples (MJ-1 & MJ-2) Table 21 shows the JET results obtained for the samples MJ-1 and MJ-2. A reasonable repeatability is observed for all three techniques. Table 21. JET results for the samples MJ-1 and MJ-2

106 Sample Blaisdell Solution Scour Depth Solution Iterative Solution (Pa) (cm3/N.s) (Pa) (cm3/N.s) (Pa) (cm3/N.s) MJ-1 1.9 1.45 1.74 1.4 4.74 5.22 MJ-2 1.37 1.02 3.89 2.12 3.63 5.2 Sand Samples (SJ-1 & SJ-2) Table 22 shows the JET results obtained for the samples SJ-1 and SJ-2. Except for the iterative solution, a reasonable repeatability is observed for the other techniques, especially for the critical shear stress values. Table 22. JET results for the samples SJ-1 and SJ-2 Sample Blaisdell Solution Scour Depth Solution Iterative Solution (Pa) (cm3/N.s) (Pa) (cm3/N.s) (Pa) (cm3/N.s) SJ-1 4.10 1.34 8.30 5.56 5.15 10.54 SJ-2 4.06 0.73 8.03 3.59 3.96 5.48 Gravel Samples (GJ-1 & GJ-2) Similar to the HET, the JET can only be performed in fine grained soils. Therefore, no HET could be conducted for the gravel samples. Field Erosion Device Demonstration As shown in Table 17, the erosion testing consists of organizing field demonstration tests including the BET device, the PET, and possibly the ISEEP of NC-State and the ISTD of the FHWA. Invitation letters were sent to Dr. Gabr of North Carolina State University for bringing their erosion testing device (ISEEP), as well as to Dr. Kerenyi for bringing the FHWA in situ testing device. Dr. Gabr of the NC-State did not have the funds necessary to bring his equipment to College Station. Dr. Kereneyi of the FHWA, mentioned that they are still working on improving their device and need more time, thus are not ready to contribute to this project. It was decided to perform feasible available field tests at the National Geotechnical Experimentation Site at RELLIS Campus of Texas A&M University. These tests include the BET and the PET on both sand and clay sites. Terracon Consultants, Inc. in Conroe, TX provided necessary equipment to perform the Field Demonstration for this project. This section presents the results of the BET in clay and sand sites. The following BET procedure was undertaken in both sites: 1. Sampling from 2 to 5 ft, from 6 to 9 ft, and from 10 to 13 ft in a 14 ft deep borehole with 3” diameter Shelby Tubes. Three 3 ft long Shelby Tube samples every 4 ft. Use 3 inch drill bit if necessary. 2. Insert mechanical caliper (Figure 67) and measure diameter vs. depth.

107 3. Circulate the drilling fluid (Figure 68) for one minute in order to flush the borehole. 4. Insert mechanical caliper and measure diameter vs. depth. 5. Withdraw mechanical caliper. 6. Insert drilling rods down to 6” above the bottom of the hole, circulate drilling fluid for 15 minutes at maximum pump velocity. 7. Withdraw NW drilling rods. 8. Insert mechanical caliper and measure diameter vs. depth. 9. Withdraw mechanical caliper. 10. Insert drilling rods 6” above the bottom of the hole, circulate drilling fluid for 15 minutes at half the previous rate. 11. Withdraw NW drilling rods. 12. Insert mechanical caliper and measure diameter vs. depth. 13. Withdraw mechanical caliper. 14. Insert drilling rods 6” above the bottom of the hole, circulate drilling fluid for 15 minutes at a flow rate to be decided in the field. 15. Withdraw NW drilling rods. 16. Insert mechanical caliper and measure diameter vs. depth. 17. Withdraw mechanical caliper. 18. Plot the data and adjust the procedure. A photograph from the pump and the flowmeter assembly on the drill rig is shown in Figure 69. One borehole in the sand site and one borehole in the clay site were drilled using 3 in diameter hollow stem augers. The drilling rods used to circulate the drilling fluid was 2.75 in diameter. This leaves an almost quarter inch empty space between the drilling rods and the borehole wall. During the test, the flow rate is constantly monitored using the in-line flowmeter shown in Figure 69; therefore, the velocity of the fluid in the borehole can be obtained by dividing the flow rate by the annular space between the drilling rods and the borehole wall. Results of the BET for clay and sand are discussed in the following.

108 Figure 67. Photographs taken from the mechanical caliper (3 arms) in closed-arm and opened- arm conditions Figure 68. Circulating the drilling fluid in the borehole in order to flush

109 Figure 69. Photograph of the pump and the in-line flowmeter assembly on the drill rig BET at Clay Site One borehole was drilled down to the depth of 14 ft. The borehole was located at the coordinates: N 30o.38.104’, W 096o.29.348’. Soil was classified as CH throughout the borehole. As described earlier in the BET procedure, the zero reading was measured after 1 minute of flushing at 36 gpm (0.002271 m3/s) flow. After that, three different flows of 35 gpm (0.002208 m3/s), 21 gpm (0.001325 m3/s), and 33 gpm (0.002082 m3/s) were generated in the borehole and maintained for 10 minutes each. The diameter profile was obtained after each flow using the mechanical caliper shown in Figure 67. Figure 70 shows the caliper readings in five different stages: 1) Before flushing: right after the borehole was drilled and before doing the 1-minute flushing 2) After flushing: readings were made after 1-minute flushing 3) Reading 1: the borehole diameter profile was obtained after 10 minutes of 35 gpm flow 4) Reading 2: the borehole diameter profile after 10 minutes of 21 gpm flow 5) Reading 3: the borehole diameter profile after 10 minutes of 33 gpm flow It should be noted that the caliper readings at each of the aforementioned stages were obtained in two runs in order to make sure that the readings are repeatable. For all the cases, an acceptable overlay was observed, and the repeatability of caliper readings were confirmed. The borehole diameter profiles shown in Figure 70 portray the averaged diameter profile between the first and second runs at each stage. Before doing any calculations of the erosion rate, Figure 70 clearly shows that there is a weak sand fissure at the proximity of the depth of 7.5 to 8.5 ft which has

110 caused much higher diameter enlargement. This observation, indeed, is an example of one of the most important advantages of the BET compared to many other erosion tests in catching a continuous erodibility profile in a site prior to construction of bridges, levees, dams, etc. While Figure 70 shows the borehole diameter profile at different stages during the test, it must be noted that the erosion function curve (i.e. “average erosion rate vs. the fluid velocity” plots) were constructed for each 2 ft intervals (i.e. 2-4 ft, 4-6 ft., 6-8 ft., 8-10 ft., 10-12 ft.) separately. Table 23 gives the flow rates, velocities, and time of application of each velocity for the BET at clay site. Figure 71 shows the erosion function curves for each of the 2 ft intervals. As discussed in Section 2.2.3, the BET has two component tests: the lateral erosion test associated with the increase in diameter of the borehole (also called as the LBET), and the bottom erosion test associated with the increase in depth below the bottom of the drilling rods during the flow (also called as the BBET). The first one is very similar in concept to the HET but with a larger hole and a vertical flow direction. The latter one is much like an in situ jet erosion test. The depth increase at the bottom of the borehole was monitored after each stage (BBET); however, these measurements did not lead to a reasonable erosion rate at the bottom of the hole. The main reason was that as the wall of the borehole was being eroded, some eroded materials would settle and remain at the bottom of the borehole, and therefore, the measurements of the bottom depth did not necessarily represent the actual erodibility of the soil at that depth. This issue, however, was not confronted during the BET at the sand site. The following section presents the results of the LBET and the BBET in the sand site. Table 23. Flow, velocity, and time for the BET at clay site Depth Flow (m3/s) Velocity (m/s) Duration (min) Change in profile (Figure 70) 2 ft – 4 ft 0.002271 1.967 1 before flushing to after flushing 0.002208 1.308 10 After flushing to reading 1 0.001325 0.773 10 Reading 1 to reading 2 0.002082 1.063 10 Reading 2 to reading 3 4 ft – 6 ft 0.002271 2.639 1 before flushing to after flushing 0.002208 1.444 10 After flushing to reading 1 0.001325 0.967 10 Reading 1 to reading 2 0.002082 1.431 10 Reading 2 to reading 3 6 ft – 8 ft 0.002271 2.450 1 before flushing to after flushing 0.002208 1.280 10 After flushing to reading 1 0.001325 0.669 10 Reading 1 to reading 2 0.002082 0.687 10 Reading 2 to reading 3 8 ft – 10 ft 0.002271 N/A 1 before flushing to after flushing 0.002208 0.596 10 After flushing to reading 1 0.001325 0.418 10 Reading 1 to reading 2 0.002082 0.433 10 Reading 2 to reading 3 10 ft – 12 ft 0.002271 2.242 1 before flushing to after flushing 0.002208 1.188 10 After flushing to reading 1 0.001325 0.621 10 Reading 1 to reading 2 0.002082 0.712 10 Reading 2 to reading 3

111 Figure 70. Clay borehole diameter profile at different stages during the BET

112 Figure 71. LBET Results - erosion function curves for each of the 2 ft. intervals in the clay site Figure 72 shows the results of some earlier EFA tests performed on samples taken from the same depths in the clay site. These EFA tests were performed about one year earlier than the BET. Also, the boring, from which samples were taken for EFA testing, was not the same as or close to the boring in which BET was performed. These two factors as well as different flow conditions in EFA and BET could be the main reasons that the EFA and BET results are not matching perfectly. Clearly, there is a gap between the results of the two tests; however, in both tests, most erosion is observed in the soil layers deeper than 6 ft. Existence of a weak sand fissure at the proximity of 8 ft makes a big difference in the erosion resistance of the borehole in the clay site. Figure 72. EFA Results - erosion function curves for each of the 2 ft. intervals in the clay site

113 BET at Sand Site One borehole was drilled down to the depth of 12 ft. The borehole was located at the coordinates: N 30o.38.301’, W 096o.27.606’. Soil was classified as SC throughout the borehole. Similar to what described earlier in the BET procedure, the borehole was flushed for almost 30 seconds at 37 gpm (0.002334 m3/s) flow. After that, two different flows of 34 gpm (0.002145 m3/s) and 38 gpm (0.002397 m3/s) were generated in the borehole and maintained for 7 minutes each. The borehole diameter profile was obtained after each flow using the mechanical caliper shown in Figure 67. Figure 73 shows the caliper readings in four different stages during the test: 1) Before flushing: right after the borehole was drilled and before doing the 30-seconds flushing 2) After flushing: readings were made after 30 seconds flushing 3) Reading 1: the borehole diameter profile after 7 minutes of 34 gpm flow 4) Reading 2: the borehole diameter profile after 7 minutes of 38 gpm flow Similar to the BET at the clay site, the caliper readings at each of the aforementioned stages were obtained in two runs in order to make sure that the readings are repeatable. For all the cases, an acceptable overlay was observed, and the repeatability of caliper readings were confirmed. The borehole diameter profiles shown in Figure 73 portray the averaged diameter profile between the first and second runs at each stage. It is clearly shown that the diameter enlargement at depths closer to the ground surface (0-3 ft) was significantly higher than other depths. While Figure 73 shows the borehole diameter profile at different stages during the BET, it must be noted that the erosion function curve (i.e. “average erosion rate vs. the fluid velocity” plots) were constructed for each 2 ft intervals (i.e. 1-3 ft, 3-5 ft., 5-7 ft., 7-9 ft., 9-11 ft.) separately. Table 24 gives the flow rates, velocities, and time of application of each velocity for the BET at sand site. Figure 74 shows the erosion function curves for each of the 2 ft intervals. Figure 75 shows the results of some earlier EFA tests performed on the sand site samples. The sand samples tested in the EFA were mixed from different depths, and constructed in the laboratory to represent a similar condition in the field. The EFA results are in an acceptable consistency with the BET results specifically for the soil deeper than 5 ft. As mentioned earlier, the first five feet showed a significant erosion during the BET. One of the reasons for a much higher erosion in depths closer to the ground surface was that as the test was being performed, the cohesion-less sand wall on top of the borehole became weaker and started eroding more compared to deeper layers. However, in deeper layers, more reasonable erosion was observed. One of the reasons that better consistency between EFA and BET on sand samples is observed can be the fact that the borings used for BET and EFA were close to each other, and therefore soils from same depth were more similar compared to the case of clay site. The BET results discussed above are all associated with the increase in the diameter of the borehole (LBET). For the sand borehole, the depth increase at the bottom of the borehole was also monitored (BBET). The erosion function curve for the bottom of the sand borehole is shown in Figure 76. Briaud et al. (2016) showed that the flow velocity of the jet eroding the borehole is almost equal to the average velocity of the flow in the annular space between the drilling rods and the borehole wall at depths close to the jet nozzle. For this purpose, the average velocities of the

114 flow for the depth 9’-11’ is chosen to represent the velocities of the jet at the bottom of the borehole. The BBET result presented in Figure 76 shows a higher erosion rate compared to the LBET result for the depth 9-11 ft in Figure 74. Figure 73. Sand borehole diameter profile at different stages during the BET

115 Table 24. Flow, velocity, and time for the BET at sand site Depth Flow (m3/s) Velocity (m/s) Duration (min) Change in profile (Figure 73) 1 ft – 3 ft 0.002334 0.518 0.5 before flushing to after flushing 0.002145 0.147 7 After flushing to reading 1 0.002397 0.102 7 Reading 1 to reading 2 3 ft – 5 ft 0.002334 0.548 0.5 before flushing to after flushing 0.002145 0.179 7 After flushing to reading 1 0.002397 0.162 7 Reading 1 to reading 2 5 ft – 7 ft 0.002334 2.453 0.5 before flushing to after flushing 0.002145 1.555 7 After flushing to reading 1 0.002397 1.191 7 Reading 1 to reading 2 7 ft – 9 ft 0.002334 1.652 0.5 before flushing to after flushing 0.002145 0.988 7 After flushing to reading 1 0.002397 0.721 7 Reading 1 to reading 2 9 ft – 11 ft 0.002334 1.207 0.5 before flushing to after flushing 0.002145 0.769 7 After flushing to reading 1 0.002397 0.647 7 Reading 1 to reading 2 Figure 74. LBET Results - erosion function curves for each of the 2 ft intervals in the sand site

116 Figure 75. EFA Results - erosion function curves for each of the 2 ft intervals in the sand site Figure 76. BBET Results - erosion function associated with the bottom of the sand borehole

117 Erosion Tests Performed Using Many Different Soils This section is dedicated to running different erosion tests on many natural samples. More than 128 erosion tests (32 EFA, 32 JET, 32 HET, and 32 PET) on 14 natural clay, 8 silt, 6 sand, and 4 gravel samples were performed. Many of these tests were performed on the natural samples taken from Terracon office in Houston. Some were collected from the Alcona Dam near Oscoda, Michigan, as well as Tittabawassee River in Midland, Michigan, Crane Creek in California, and Freeport and Lissie in Texas. After Hurricane Harvey, Iman Shafii (Lead Engineer working on this NCHRP Project) joined the Geotechnical Extreme Events Reconnaissance (GEER) team supported by National Science Foundation (NSF). During this major effort, 15 samples from different locations were obtained and brought to the soil erosion laboratory for erosion testing (primarily for the EFA testing). A few challenges confronted the investigating team during the erosion testing phase, due to the limitations with each erosion testing device. Following revisions were made to the testing plan: 1. On HET testing on clay and silt samples: HET was primarily conducted on remolded samples instead of natural samples, following the advice of the panel. 2. On HET testing on sand and gravel (6 tests on sand, and 4 tests on gravel): The HET tests could not be properly conducted on sand and gravel samples due to the limitations associated with its setup. The drilled hole in all cases collapsed for sand samples. For gravel samples, clearly, this test was not feasible. Therefore, it was decided to increase the number of erosion tests on any other sample (mostly coarse-grained samples) using other erosion tests (i.e. EFA and PET) to make up for the number of erosion tests promised in the proposed testing matrix. 3. On JET testing on gravel (4 tests on gravel): The JET test also is not designed for gravel samples. Therefore, no JET was reported for gravel samples. A summary of the tested samples presented in this section is shown in Table 25. Majority of Table 3 is incorporated with intact samples; however, some cohesion-less samples were remolded in the laboratory to follow the testing matrix shown in Table 17. Erosion result spreadsheets as described in earlier sections were prepared for each tested sample separately. Appendix 1 shows the results of EFA, JET, and HET for all samples tested in this project. The total number of tests performed during this project turned out to be more than 168 erosion tests promised in the proposed testing matrix.

118 Table 25. Summary list of the tested sample Test Samples Name Collected from Date Collected Site Intact Samples EFA and PET B-1 (23’-25’) G2 Consulting Group, LLC Dec 2016 Tittabawassee River, Midland, MI B-7 (22’-24’) B-9A (25’-27’) B-9A (29’-31’) B-7-16 @ 8.5’ Barr Engineering Co. Nov 2016 Alcona Dam, Oscoda, MI B-7-16 @ 11.6’ B-7-16 @ 13.5’ B-7-16 @ 15.3’ B-9-16 @ 16.1’ B-9-16 @ 17.3’ B-11-16 @18’ B-11-16 @ 20.5’ B-12-16 @ 18.1’ B-12-16 @ 18.9’ B-12-16 @ 20.5’ B-13-16 @ 19’ B-13-16 @ 20.5’ B-13-16 @ 23.5’ B-2 (13’-15’) Terracon, Houston Oct 2016 Beaumont Formation, TX B-6 (0’-2’) B-1 (4’-6’) B-1 (28’-30’) B-8 (2’-4’) 5694 B-1 (12.5’-14.5’) American Geotechnics Apr 2017 Crane Creek, CA GEER Sample #1 Geotechnical Extreme Events Reconnaissance (GEER) Sept 2017 Port Aransas bridge, TX GEER Sample #2 Bay City Bridge, TX GEER Sample #3 GEER Sample #4 GEER Sample #5 GEER Sample #6 San Louis Pass, TX GEER Sample #7 GEER Sample #8 Levee at Brazos River, TX GEER Sample #9 Rosenberg Culvert Bridge, TX GEER Sample #10 JET and PET B-1 (2’-4’) Terracon, Houston Oct 2016 Beaumont Formation, TX B-1 (4’-6’) B-1 (8’-10’)

119 B-1 (10’-12’) B-1 (13’-15’) B-1 (18’-20’) B-1 (28’-30’) B-2 (2’-4’) B-2 (8’-10’) B-2 (13’-15’) B-3 (8’-10’) B-4 (8’-10’) B-5 (4’-6’) B-5 (6’-8’) B-6 (0’-2’) B-2 (8’-10’) Terracon, Houston Winter 2016 Lissie Formation TX B-3 (10’-12’) B-8 (2’-4’) Terracon, Houston Winter 2016 Alluvium, Freeport TX B-13 @ 20’ B-13 @ 18’ B-9A @ 26’ G2 Consulting Group, LLC Dec 2016 Tittabawassee Midland, MI B-9A @ 27’ B-1 (23’-25’) B-7 (22’-24’) GEER Sample #2 GEER Sept 2017 Bay City Bridge, TX Remolded Samples EFA and PET Teton Dam 1 N/A N/A N/A Teton Dam 2 Teton Dam 3 Sample 2 (FHWA) S-0-0-0 Sand #1 Sand #2 Gravel #1 Gravel #2 Gravel #3 Gravel #4 JET and PET Teton Dam Core S-0-0-0 Sand #1 Sand #2 Sample 2 (FHWA) HET and PET Clay #1 N/A N/A N/A Clay #2 Clay #3

120 Clay #4 Clay #5 Clay #6 Clay #7 Clay #8 Clay #9 Clay #10 Clay #11 Clay #12 Clay #13 Clay #14 Silt 1 Silt 2 Silt 3 Silt 4 Silt 5 Silt 6 Silt 7 Teton Dam Core 4.4. Soil Geotechnical Properties As mentioned earlier, soil index tests were conducted for all the samples tested by any erosion testing device. The geotechnical tests include: unit weight (ASTM D7263-09), moisture content (ASTM D2216-10), Atterberg limits (ASTM D4318-17), mini vane shear test (ASTM D4648), pocket penetrometer, sieve analysis (ASTM 422), hydrometer analysis (ASTM D7928-17), USCS (ASTM D2487-17), and AASHTO classification, specific gravity test (ASTM D854-14). Existing relevant geologic information such as latitude and longitude location, origin, water table data of the samples, etc. are also recorded for each sample when possible. All these information are compiled in a comprehensive two-page “soil properties spread sheet” for each sample. As an illustration, Figure 77 and Figure 78 show the two pages of the completed soil properties spread sheet for the sample B-7-16 (13’-15.5’). Such spread sheets were developed for all the soil samples that were tested in different erosion testing devices. Appendix 2 documents all the soil properties spreadsheets developed for this project.

121 Figure 77. Page 1 of the “soil properties spread sheet” for B-7-16 (13’-15.5’)

122 Figure 78. Page 2 of the “soil properties spread sheet” for B-7-16 (13’-15.5’)

Next: Chapter 5. Organization and Interpretation of the Data »
Relationship Between Erodibility and Properties of Soils Get This Book
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TRB’s National Cooperative Highway Research Program (NCHRP) has released the pre-publication version of NCHRP Research Report 915: Relationship Between Erodibility and Properties of Soils, which provides reliable and simple equations quantifying the erodibility of soils based on soil properties.

The report presents a detailed analysis of the issue. In addition, the project that developed the report also produced a searchable spreadsheet that uses statistical techniques to relate geotechnical properties to soil erodibility. The spreadsheet, NCHRP Erosion, includes a searchable database that includes compiled erosion data from the literature review and a plethora of erosion tests. It contains equations which may be used to estimate the erosion resistance of soil and determine whether erosion tests are needed.

The following appendices to NCHRP Report 915 were published online in a single Appendices Report.

Appendix 1 – Erosion Test Results Spreadsheets

Appendix 2 – Geotechnical Properties Spreadsheets

Appendix 3 – First and Second Order Statistical Analysis Results

Appendix 4 – Deterministic Frequentists’ Regression Analysis

Appendix 5 – Probabilistic Calibration Results

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