Relationship Between Erodibility and Properties of Soils (2019) / Chapter Skim
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76 This chapter presents the results of all the erosion experiments performed as part of NCHRP Project 24-43. Section 4.1 of this chapter describes the Soil Erosion Laboratory at Texas A&M University (TAMU)
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Erosion Experiments 77 Figure 37. Schematic of HET assembly (Wan and Fell 2002)
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78 Relationship Between Erodibility and Properties of Soils 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.
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Erosion Experiments 79 17 .5 12.0 18 0.
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80 Relationship Between Erodibility and Properties of Soils 63.5 3 mm DEEP RECESS 12 mm DIA.
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Erosion Experiments 81 18 0.
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82 Relationship Between Erodibility and Properties of Soils Flow rate indicator HET Sample Constant Head Tank U/S & D/S Piezometers Drainage Sump Pump Low Flowmeter Dummy Test Sample Right After the Test Flow Indicator at the Middle of a Dummy Test HET Sample Core at the Middle of a Dummy Test Drainage Hose Inflow: Tap Water Figure 42. Photos of HET assembly at TAMU (U/S = upstream; D/S = downstream)
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Erosion Experiments 83 Constant Head System Source Flow Hose Drain Hose Inlet: Tap Water JET Device Outlet: Drain Hose Submergence Tank Support Ring Standard Compaction Sample Mold Scour Gauge Inlet from Source Hose Deflector Plate Rotatable Plate JET nozzle (1/8") Figure 43.
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84 Relationship Between Erodibility and Properties of Soils 4.1.3 Refurbishment of EFA Machines and TAMU Soil Erosion Laboratory The TAMU Soil Erosion Laboratory contains two EFAs. Both machines were repaired and upgraded for the second phase of the project.
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Erosion Experiments 85 RELLIS campus. A total of 168 new erosion tests were planned to be performed during this project.
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86 Relationship Between Erodibility and Properties of Soils 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)
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Erosion Experiments 87 For the purpose of ensuring the repeatability of the erosion tests, man-made samples of all four types of soils (gravel, sand, silt, and clay) were prepared and tested using the EFA, JET, HET, and PET.
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(a) Logarithmic Scale (b)
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Erosion Experiments 89 Erosion Rate vs. Shear Stress Erosion Rate vs.
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90 Relationship Between Erodibility and Properties of Soils stress, respectively. Both samples can be categorized as high to medium erodibility (Categories II to III)
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(a) Logarithmic Scale (b)
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Figure 52. EFA test results based on velocity for ensuring the repeatability of the EFA on gravel samples.
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Erosion Experiments 93 sample surface is then measured and entered in the PET erosion categories chart. The PET was conducted three times at different areas on the top end of each sample.
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94 Relationship Between Erodibility and Properties of Soils curve is typically attributed to the thickness of the disturbed zone resulting from 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.
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Erosion Experiments 95 initial head condition for CH-1 and CH-2 differed because of the unexpected change in the test condition at the time of test (815 mm and 360 mm, respectively) ; however, when the erosion part of the curves is tracked, both curves cross the horizontal axis at a critical shear stress of 70 Pa.
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Figure 58. HET result spreadsheet for Sample CH-1.
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Erosion Experiments 97 Actual test data Tangent line Fitted curve Figure 59. HET data for Sample MH-1.
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98 Relationship Between Erodibility and Properties of Soils Actual test data Tangent line Fitted curve Figure 62. HET result for Sample SH-1.
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Erosion Experiments 99 4.3.1.4 Ensuring the Repeatability of the JET As discussed Chapter 2, for every JET the operator records 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 backanalyzed to estimate two main erodibility parameters: critical shear stress and erosion rate.
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Erosion Experiments 101 time. As shown in Figure 65, the plot of scour depth versus time is better predicted by the scour depth solution.
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102 Relationship Between Erodibility and Properties of Soils Figure 66. JET result spreadsheet for Sample CJ-1.
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Erosion Experiments 103 to invite them to participate in the field demonstration tests. However, North Carolina State University did not have the funds necessary to bring the ISEEP to College Station, and FHWA declined because it was working on improving the ISTD and thus was not ready to contribute to this project.
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104 Relationship Between Erodibility and Properties of Soils Figure 67. Photographs taken from the mechanical caliper (3 arms)
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Erosion Experiments 105 A photograph of the pump and the flow meter 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 with 3-in.-diameter hollow stem augers.
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106 Relationship Between Erodibility and Properties of Soils 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., the plot of the average erosion rate versus the fluid velocity) was constructed separately for each 2-ft interval (i.e., 2–4 ft, 4–6 ft., 6–8 ft, 8–10 ft, and 10–12 ft)
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Erosion Experiments 107 Flow (m3/s) Velocity (m/s)
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108 Relationship Between Erodibility and Properties of Soils BET. Also, the boring from which samples were taken for EFA testing was not the same as or close to the boring done for the BET.
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Erosion Experiments 109 Figure 75 shows the results of some earlier EFA tests performed on the samples from the sand site. 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.
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110 Relationship Between Erodibility and Properties of Soils Flow (m3/s) Velocity (m/s)
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Erosion Experiments 111 100,000 1,000 100 10 1 0.1 10,000 Er os io n Ra te (m m /h r) Figure 75.
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112 Relationship Between Erodibility and Properties of Soils Because of the limitations of each erosion testing device, a few challenges confronted the investigating team during the erosion testing phase. The following revisions were made to the testing plan: 1.
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Erosion Experiments 113 B-2 (8–10 ft)
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114 Relationship Between Erodibility and Properties of Soils Test and Note: Shading indicates not applicable. Sample Name Collected From Date Collected Site 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 REMOLDED SAMPLES EFA and PET Teton Dam 1 Teton Dam 2 Teton Dam 3 Sample 2 (FHWA)
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Erosion Experiments 115 4.4 Soil Geotechnical Properties Soil index tests were conducted for all samples tested by any erosion testing device. The geotechnical tests included unit weight (ASTM D7263-09)
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116 Relationship Between Erodibility and Properties of Soils 0.003 21.5 0.01340 7.0 0.003 21.5 0.01340 7.6 0.003 21.5 0.01340 8.0 0.003 21.5 0.01340 8.40 0.003 21.4 0.01341 8.8 0.003 21.1 0.01348 9.4 0.003 20.8 0.01357 10.1 0.003 20.5 0.01356 10.5 0.003 20.0 0.01365 11.0 0.003 19.0 0.01386 11.8 0.003 18.9 0.01386 12.8 D (mm) % susType Time 5 2 1 0.50 K CC 0.99954 1.0305 1.03201.035 1.0235 1.0285 1.03 1.0315 1.0335 1.017 1.02 1.022 1.0265 2 1 0.5 0.266667 0.083333 240 60 30 15 22.1 Error (%)
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