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ii - <br />higher clay content and dry unit weight than the materials which <br />• collapsed upon saturation, The dry density of the swelling samples <br />varied from 97.3 to 114.3 pcf with an average of 108.1 pcf. An <br />average of 828 of the expansive samples passed the U. S. No. 200 sieve <br />while the collapsing soils had approximately 628 passing the U.S. No. <br />200 sieve. <br />Gradation Analyses: Three gradation analyses, including sieve <br />analyses and hydrometer analyses, are presented on Figs. B-8 and B-9. <br />These grain size distribution curves are nearly identical, indicating <br />428 of the material retained on the U.S. IJo. 200 sieve and 588 passing <br />the U.S. No. 200 sieve. The material retained on the U. S. No. 200 <br />sieve is predominantly fine sand. Approximately 208 of the material <br />is finer than 2 microns, which is normally considered the upper limit <br />of clay size particles. The remaining soil fraction, approximately <br />• 358 to 408, is silt. <br />Strength Testing: Unconsolidated, undrained triaxial tests sere <br />conducted on six relatively undisturbed samples obtained in the test <br />borings. The results of this testing are shown on Figs. B-10 through <br />B-15. The cohesive strengths of these samples, which were saturated <br />prior to testing, range from 160 to 880 psf with an average cohesion <br />of 600 psf. <br />Direct shear tests and consolidated, drained triaxial tests were <br />conducted on four samples of relatively undisturbed soils obtained <br />from the test borings. The direct shear tests are shown on Figs. B-16 <br />and B-17, and the triaxial testing is shown rn Figs. B-18 and B-19. <br />The direct shear and triaxial strength testing indicate that the <br />• <br />