Relationship Between Erodibility and Properties of Soils (2019) / Chapter Skim
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20 This chapter describes some of the most common tests developed over the past century to quantify soil erodibility. The drawbacks and advantages of these testing methods are evaluated and identified.
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Existing Erosion Tests 21 is kept flush at all times by pushing the soil with the piston as it is eroded by the water and maintaining a level interface. Continue this procedure until 50 mm of the soil is eroded or 30 min have passed.
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22 Relationship Between Erodibility and Properties of Soils 5. The EFA can test the erodibility of the soil at any depth as long as a sample can be recovered.
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Existing Erosion Tests 23 soil samples, for which both pumps can be running. Also, erosion of the Shelby tube size sample is continuously monitored by the control computer with an video camera attached next to the test section.
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24 Relationship Between Erodibility and Properties of Soils to instantaneously capture both normal forces and shear stress induced on the soil surface. Samples for the ESTD are prepared in the lab, typically with a Pugger-Mixer, which prevents the existence of air bubbles in the specimen.
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Existing Erosion Tests 25 and extract a sample from the site. In soft soils, the sampler can be pushed into the soil, whereas in stiffer soils, a Vibracoring head can be used.
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26 Relationship Between Erodibility and Properties of Soils 2. The lab apparatus is very bulky and costly (more than $100,000)
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Existing Erosion Tests 27 same time with the same slope. The flow depth could be adjusted between 80 cm and 210 cm.
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28 Relationship Between Erodibility and Properties of Soils rates were calculated as the rate of dried mass removal in a given time. The shear stress on the soil sample was predicted as (10)
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Existing Erosion Tests 29 that is aligned with the orifice and measures the scour in the center of the specimen. The soil specimen is compacted in a 4-in.
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30 Relationship Between Erodibility and Properties of Soils 3. Adjust the pressure head at the jet orifice to be 775 mm.
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Existing Erosion Tests 31 To describe the relationship between the JET erosion rate and the jet velocity or calculated shear stress (erosion function) , Hanson and colleagues used a linear relationship and called the slope of the line the erosion coefficient, KD (Hanson 1991, 1992; Hanson and Cook 2004)
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32 Relationship Between Erodibility and Properties of Soils 6. The JET gives only three erodibility parameters [tc, Et, and the erosion category (EC)
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Existing Erosion Tests 33 where Save = depth of scour hole for a specific jet velocity, h0 = distance from jet orifice to soil surface, t = time of scour for a specific velocity, µ = viscosity of eroding fluid, r = eroding fluid density, and d = nozzle diameter. Moore and Masch could observe that measured Ks was linearly correlated with the Reynolds number.
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34 Relationship Between Erodibility and Properties of Soils space to transmit the shear stress onto the side surface of the sample. The test procedure is as follows: 1.
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Existing Erosion Tests 35 Drawbacks 1. Owing to the existence of the shaft within the soil sample in the apparatus, the test can only be conducted on remolded samples.
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36 Relationship Between Erodibility and Properties of Soils included masses ranging from 0 to 40 g and had a precision of 0.1 g. The device could also produce a maximum 1,750 rpm rotational speed.
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Existing Erosion Tests 37 3. The apparatus is equipped with a torque transducer.
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38 Relationship Between Erodibility and Properties of Soils The procedure for the pinhole erosion test is as follows: 1. Create a 38-mm-long sample by compacting the soil in the test cylinder above the coarse sand space, which is covered by a wire screen (Figure 17)
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Existing Erosion Tests 39 2.1.13 Drill Hole Test Lefebvre et al.
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40 Relationship Between Erodibility and Properties of Soils (a)
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Existing Erosion Tests 41 2.1.14 Hole Erosion Test The hole erosion test (HET) is a laboratory erosion test that evolved from the older pinhole erosion test and can be credited to Robin Fell in Australia (Wan and Fell 2002; Wahl et al.
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42 Relationship Between Erodibility and Properties of Soils (a)
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Existing Erosion Tests 43 where rw = density of water, st = hydraulic gradient across the hole, and φ = diameter at time t. The equation used for the erosion function is linear:  (16)
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44 Relationship Between Erodibility and Properties of Soils (a)
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Existing Erosion Tests 45 velocity while the rate of mass removal per unit area as a function of time is recorded to obtain an erosion rate (kg/s/m2)
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46 Relationship Between Erodibility and Properties of Soils (b)
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Existing Erosion Tests 47 2.1.17 True Triaxial Piping Test Apparatus Richards and Reddy (2010) developed a true triaxial piping test apparatus (TTPTA)
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48 Relationship Between Erodibility and Properties of Soils (a)
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Existing Erosion Tests 49 depth is compared with an erosion chart to determine the erosion category of the soil, which helps the geotechnical engineer with preliminary design of erosion projects. Many different options were considered during the development of the pocket erodometer, including the most appropriate device, velocity range, direction of application, distance from the face of the sample, and repeatability from one person to another.
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50 Relationship Between Erodibility and Properties of Soils The height of the erodometer (shown as H in Figure 24) must be kept constant during the calibration process.
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Existing Erosion Tests 51 5. Using the end of a digital caliper or an appropriate measuring tool, measure the depth of the hole created.
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52 Relationship Between Erodibility and Properties of Soils subsurface is measured and represents the erosion rate. The body of the probe is divided into sections so that the length can be adjusted for deep locations in the field.
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Existing Erosion Tests 53 2. The use of the stream power makes it difficult to compare this device with other erosion devices.
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54 Relationship Between Erodibility and Properties of Soils 2. Each test gives the erosion function for all layers traversed, since a complete borehole diameter profile is obtained from the caliper.
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Existing Erosion Tests 55 2.3 Summary A summary of all the erosion tests reviewed in this chapter is presented in Table 4 in terms of their application in the field or the lab. Table 5 shows some of the most common and important erosion tests with information regarding their ability to measure shear stress, the soil type that can be tested, and the cost associated with them.
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