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<br />e <br /> <br />e <br /> <br />e <br /> <br />3-33 <br /> <br />banks during high flows, possibly leaving a deflocculated, dispersed, <br />erodible surface layer. In arid and semi-arid regions, the soluble <br />salt content ,may be determined for representative samples, even though <br />results of this test cannot be used quantitatively at present. <br /> <br />Linear shrinkage. - - Coherent soils which have linear shrinkage <br />factors in the range of ten percent or more are generally subject to <br />considerable density and strength changes with variations in moisture <br />content, Results from linear shrinkage tests on coherent soils serve <br />as indicators of potential problems related to bank stability. <br /> <br />Field Sample and Test Specimen Requirements <br /> <br />The quantity of materials needed for testing depends primarily on such <br />factors as (I) number, type and purpose of tests to be performed, (2) <br />particle size characteristics of the material, and (3) homogeneity of <br />the natural materials, particularly when undisturbed specimens are to <br />be tested. The minimum number of test specimens for one test is given <br />below: <br /> <br />Unconfined compression <br />Direct shear <br />Triaxial shear <br />Permeability <br /> <br />I <br />3 <br />3 <br />I <br /> <br />It is suggested that undisturbed samples be large enough so that an <br />additional test specimen will be available as a spare. In the case <br />of small diameter tube samples, duplicate sampling should be obtained. <br /> <br />Sample sizes and specimen requirements for testing of soils from channel <br />projects are given in Table 3-3 (Disturbed Samples) and 3-4 (Undisturbed <br />Samples) . The specimen sizes given in Table 3-4 are those which are <br />actually required for testing; these sizes do not include allowances <br />for trilllllling. <br />