Container, large enough to permit immersingthe wire basketSuitable equipment for suspending the wirebasket from the center of balance scale panThermometer, general laboratoryPROCEDURE.— Perform the test in thefollowing steps. You must complete the first stepas quickly as possible after surface-drying thesample.1. Determine the weight of the saturated-surface-dry sample and container. This weightminus the tare weight of the container is theweight of the saturated-surface-dry soil that youshould enter in block 7e (fig. 15-33).2. Determine the weight of the wire basketsuspended in water. Record this weight in block7g (fig. 15-33).3. Place the sample in the basket and immersethe basket and sample in water. (Hang the basketfrom the balance and support the container so thatthe basket hangs freely in the water.) Read theweight and record it in block 7f (fig. 15-33). Sub-tract the weight of the empty basket suspendedin water, Step 2 above, to determine the weightof the saturated soil in water. Record this weightin block 7h (fig. 15-33).4. Measure and record the temperature of thewater and soil. Enter this temperature in block7b (fig. 15-33).5. Determine the ovendry weight of thesample and enter the results in block 7k(fig.15-33).6. From the recorded information, you maynow calculate both the bulk specific gravity (G~)and the apparent specific gravity (Ga) using thefollowing formulas:andSpecific Gravity of Composite SampleAfter determining the specific gravity of solids(G.) and the apparent specific gravityyou can calculate the specific gravity of an en-tire soil sample (both larger and smaller thana No. 4 sieve). To do so, use the followingformula:Enter this composite specific gravity in theremarks block of the data sheet. Note, too, thatyou should also enter in the remarks block thepercent of materials that is retained on, or passes,the No. 4 sieve.Comment Regarding CorrectionFactor (K)Refer again to figure 15-33. In this figure, yousee the values of G~,G., and G~ that were ob-tained using the correction factor (K). Now, if youwere to disregard K and recalculate, you wouldobtain values of the following: G. = 2.7939,G== 2.6638, and Gm= 2.4471. As you can see,these values, obtained without the correction fac-tor, are hardly different than the values obtainedwith the correction factor. Therefore, unlessunusually accurate precision is required, the cor-rection factor may be disregarded.ATTERBERG LIMITSAs you previously learned, fine-grained soilsare not classified under the Unified Soils Clas-sification System on the basis of grain sizedistribution. They are, instead, classified on thebasis of plasticity and compressibility. The At-terberg limits are laboratory classification criteriaused for classifying fine-grained soils. As an EA3,you will be responsible for the performance of theAtterberg limits test.A clay or related fine-grained soil, when dryor nearly dry, has a semisolid consistency. Asmoisture content increases, a point is reachedwhere the material has a plastic (putty like) con-sistency. This point is called the PLASTIC LIMIT(PL). As moisture content continues to increase,the material remains plastic over a certain range.However, at a point called the LIQUID LIMIT(LL), the consistency of the material finallychanges to semiliquid.The upper and lower limits of the plastic range(that is, the liquid and plastic limits) are calledATTERBERG LIMITS. These limits were namedafter a Swedish scientist who developed the con-cept of the limits. The liquid limit (LL) is simply15-29
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