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e . e > .. e EM 1110-2-1913 31 Mar 78 channels, and other discontinuities in surface blankets can signifi- cantly affect the overall effective permeability. Therefore, an average value of the coefficient of permeability based on the dominant soil type (Appendix B) is generally of sufficient accuracy for use in underseepage analyses, and laboratory tests are not essential. 3-7. Compaction Tests. The type and number of compaction tests will be influenced by the method of construction and the variability of avail- able borrow materials. The types of compaction tests required are summarized in table 3-1. Section II. Coarse-Grained Soils 3-8. Shear Stren~th. When coarse-grained soils contain few fines, the consolidated drained shear strength is appropriate for use in all types of analyses. In most cases, conservative values of the angle of inter- nal friction (~) can be assumed from correlations such as those shown in figure 3~5, and no shear tests will be needed. 3-9. Permeability. To solve the problem of underseepage in levee foun- dations, reasonable estimates of permeability of pervious foundation deposits are required. However, because of difficulty and expense in obtaining undisturbed sam.ples of sands and gravels, laboratory perme- ability tests are rarely performed on foundation sands. Instead, field pumping t~sts or correlations such as that of figure 3-5 devel- oped between a grain-size param.eter (such as Dla) and the coefficient of permeability, k, are generally utilized. 3-10. Density Testing of Pervious Fill. Maximum and m~n:unum density tests on available pervious borrow materials should be performed in accordance with procedures described in EM 1110-2-1906 (ref. A-3a(7)) so that relative density requirements for pervious fills may be checked in the field when required by the specifications. 3-11