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From page 301... ... 301 The goal of this project was to develop reliable and simple equations quantifying the erodibility of soils on the basis of soil properties. The reliability must take into account the accuracy required for erosion-related projects, while the simplicity must consider the economic aspects of erosion-related projects. Read the entire page →
From page 302... ... 302 Relationship Between Erodibility and Properties of Soils applications of the three major erosion tests (EFA, JET, and HET) used in this study are presented in Table 90 (Chapter 8) Read the entire page →
From page 303... ... Conclusions and Recommendations 303 the erosion process. The first part of the chapter dealt with the evolution of hydraulic shear stress and the velocity profile with the assumption that the soil was not erodible. Read the entire page →
From page 304... ... 304 Relationship Between Erodibility and Properties of Soils aSee Chapter 7, Section 7.3.1. bn = number of data points. Read the entire page →
From page 305... ... Conclusions and Recommendations 305 9.1.8 Chapter 8: Most Robust Correlation Equations Chapter 8 began with a summary of the advantages, disadvantages, and applications of the three major erosion tests used in this study -- the EFA, the JET, and the HET [see Table 90 (Chapter 8) Read the entire page →
From page 306... ... 306 Relationship Between Erodibility and Properties of Soils 9.2 Recommendations on How to Approach Erosion-Related Design Problems One of the key missions of this project was to provide engineers in charge of erosion problems with a set of correlation equations for predicting erosion parameters without the need to perform multiple and costly erosion tests. In this section, a step-by-step approach is presented. Read the entire page →
From page 307... ... Conclusions and Recommendations 307 The most robust equations were repeated in Chapter 8, Section 8.2. The proposed equations were developed on the basis of data obtained in different erosion tests (i.e., EFA, JET, and HET) Read the entire page →
From page 308... ... 308 Relationship Between Erodibility and Properties of Soils from different projects. (Chapter 5 of this report includes the Inquiry Operation Manual for NCHRP-Erosion.) Read the entire page →
From page 309... ... Conclusions and Recommendations 309 Therefore, The POO plot in Table 95 shows that to reach 80% confidence that the predicted Et is greater than the actual Et, the predicted value should be multiplied by 2.5 (2.5 × 0.19 = 0.475 mm/h-Pa) Read the entire page →
From page 310... ... 310 Relationship Between Erodibility and Properties of Soils The POU plot in Table 92 shows that to reach 90% confidence that the predicted tc is less than the actual tc, the predicted value should be multiplied by 0.6 (0.6 × 7.54 = 4.54 Pa) Read the entire page →
From page 311... ... Conclusions and Recommendations 311 Table 99 shows the recommended equations for the erosion category (EC) according to the EFA test data. Read the entire page →
From page 312... ... 312 Relationship Between Erodibility and Properties of Soils Table 93 shows the recommended equations for critical shear stress (tc) according to the HET data. Read the entire page →
From page 313... ... Conclusions and Recommendations 313 The POO plot in Table 97 shows that to reach 90% confidence that the predicted Et is greater than the actual Et, the predicted value should be multiplied by 1.45 (1.45 × 1.13 = 1.64 mm/h-Pa) Read the entire page →
From page 314... ... 314 Relationship Between Erodibility and Properties of Soils developed on the basis of the EFA, JET, and HET data; however, as also mentioned previously, the user is referred to Table 90 to select the best equation according to his or her objective. Table 91 shows the recommended equations for critical shear stress (tc) Read the entire page →
From page 315... ... Conclusions and Recommendations 315 Therefore, The POO plot in Table 95 shows that to reach 87% confidence that the predicted Et is greater than the actual Et, the predicted value should be multiplied by 2 (2 × 7 × 10-11 = 14 × 10-11 mm/h-Pa) Read the entire page →
From page 316... ... 316 Relationship Between Erodibility and Properties of Soils The POU plot in Table 99 shows that to reach 90% confidence that the predicted EC is less than the actual EC, the predicted value should be multiplied by 0.75 (0.75 × 3.3 = 2.48) Read the entire page →
From page 317... ... Conclusions and Recommendations 317 • An increase in the plasticity index (PI) in general leads to an increase in the erosion resistance in both coarse-grained and fine-grained soils (especially soils with D50 less than 0.3 mm) Read the entire page →

From page 301...

... 301 The goal of this project was to develop reliable and simple equations quantifying the erodibility of soils on the basis of soil properties. The reliability must take into account the accuracy required for erosion-related projects, while the simplicity must consider the economic aspects of erosion-related projects.