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适用范围：<p>Dispersive clays are those which normally deflocculate when exposed to water of low-salt concentration, the opposite of aggregated clays that would remain flocculated in the same soil-water system <span class="bold"> (3, 4, 7). </span>Generally, dispersive clays are highly erosive, possibly subject to high shrink-swell potential, may have lower shear strength, and have lower permeability rates than aggregated clays.</p> <p>Available data <span class="bold">(1)</span> indicates that the test method has about 85 % reliance in predicting dispersive performance (85 % of dispersive clays show more than 35 % dispersion).</p> <p>Since this test method may not identify all dispersive clays, design decisions based solely on this test method may not be conservative. It is often run in conjunction with the crumb test <span class="bold">(4, 7)</span>, the pinhole test given in Test Method <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D4647-HTML">D4647</a>, or the analysis of the pore water extract <span class="bold">(4, 7)</span>, or combination thereof, to identify possible dispersive clay behavior.</p> <p class="desc" id="N00001"> <span class="smallcap">Note</span> 18212;Notwithstanding the statement on precision and bias contained in this test method; the precision of this test method is dependent on the competence of the personal performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D3740-HTML">D3740</a> are generally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D3740-HTML">D3740</a> does not in itself ensure reliable testing. Reliable testing depends on several factors; Practice <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D3740-HTML">D3740</a> provides a means of evaluating some of those factors.</p><p id="s00002">1.1 This test method, when used in conjunction with a test performed by Test Method <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D422-HTML">D422</a> on a duplicate soil sample, provides an indication of the natural dispersive characteristics of clay soils <span class="bold">(1).</span> </p> <p id="s00003">1.2 This test method is applicable only to soils with a plasticity index greater than 4 as determined in accordance with Test Method <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D4318-HTML">D4318</a> and more than 12 % of the soil fraction finer than 5-<span class=''unicode''>x03BC;</span>m as determined in accordance with Test Method <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D422-HTML">D422</a> <span class="bold">(2). </span></p> <p id="s00004">1.3 This test method is similar to Test Method <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D422-HTML">D422</a>, except that this method covers the determination of percent of soil particles smaller than 5-<span class=''unicode''>x03BC;</span>m in diameter in a soil-water suspension without mechanical agitation and to which no dispersing agent has been added. </p> <p id="s00005">1.4 The amount of particles smaller than 5-<span class=''unicode''>x03BC;</span>m determined by this method compared with the total amount of particles smaller than 5-<span class=''unicode''>x03BC;</span>m determined by Test Method <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D422-HTML">D422</a> is a measure of the dispersive characteristics of the soil.</p> <p id="s00006">1.5 This test method may not identify all dispersive clay soils. Pinholes (Test Method <a href="http://myastm.astm.org/SUBSCRIPTION/NewValidateSubscription.cgi?D4647-HTML">D4647</a> and crumb tests, or both, (<sp......