An alternate method of sand calibration uses acontainer of known weight, such as a Proctor mold. Inthis method, you first weigh the mold and the attachedbase plate. Then, after attaching the mold collar, youpour the sand through the sand cone into the mold. Next,you remove the collar, strike off the excess sand, brushoff the outside of the mold and base plate, and weigh thesand-filled mold (with the base plate attached). Thedifference in weights (filled and empty) divided by theknown volume of the mold is equal to the density of thesand.The third calibration(surface calibration) isdiscussed as part of the site preparation since it must beperformed at the test site.SITE PREPARATION.— Site preparation con-sists of preparing the test surface, seating the templatetray, and surface calibration of the tray.Begin your site preparation by choosing an area ofthe compacted surface that appears most level. You mayhave to remove some loose debris; however, make noattempt to pack or smooth the surface. Next, you seatthe template tray flush on the surface, especially aroundthe center hole. If necessary, seal any spaces around thecenter hole of the tray with modeling clay. Then forcenails through the holes in the tray to hold it firmly inplace. Now you are ready to perform the surfacecalibration.Surface calibration accounts for surface irregu-larities of the area to be tested. With the valve closed,turn the sand-filled apparatus over and place the largecone over the center hole of the template tray. Openthe valve and allow the sand to pass through until thelarge cone is completely filled. Do NOT shake orvibrate the apparatus. Then close the valve, weigh theapparatus with the remaining sand, and enter thisweight on line 8 of DD Form 1215 (fig. 13-6A). Thedifference between the initial weight (line 7) and thefinal weight (line 8) is the weight of the sand thatpassed through the cone valve into the lower cone andthe center hole of the template. Enter that weight online 9.After performing the surface calibration, recoveras much of the sand from the tray as possible withoutdisturbing the template tray or the soil in the hole.Brush the remaining sand particles lightly from withinthe tray. Leave the template in place for the volume-of-hole determination to be discussed next.VOLUME-OF-HOLE DETERMINATION.—The volume-of-hole determination consists of diggingout a soil sample through the center of the template andcomputing the volume of the resulting hole.The hole that is dug through the center hole of thetemplate tray should be about 6 inches deep andapproximately the same diameter as the hole in thetray. When digging, keep the inside of the hole as freefrom pockets and sharp protuberances as possible.Make sure that ALL material removed from the holeis placed in a container of known and recorded weight(line 23, fig. 13-6B). Keep the lid on the container asmuch as possible to prevent excessive moisture lossuntil it is weighed. When all removed material hasbeen placed in that container, immediately weigh itand record the weight of the container and the materialon line 15. Mark the container for later identificationwhen the soil moisture content is determined.Next, place the sand-cone apparatus over the holein the tray and open the valve to allow the sand to flowinto the hole that you have just dug. When the sandstops flowing, close the valve and weigh the apparatuswith its remaining sand. Record this weight on line 11(fig. 13-6A). The weight of the sand required to fillthe hole and the volume of the hole can then bedetermined by following the instructions printed onthe data sheet.DENSITY DETERMINATION.— Now that youhave determined the volume of the hole, the onlyremaining requirements are to determine the moisturecontent and the dry density of the sample that wasremoved from the hole. The moisture content should bedetermined using the oven-dried method that youstudied in the EA3 TRAMAN. Lines 15 through 21 ofDD Form 1215 (fig. 13-6B) are used to record themoisture-content data.The wet density or unit weight (line 25) iscomputed by dividing the wet soil weight (line 24) by453.6 to convert the grams to pounds and then by thevolume of the hole (line 14, fig. 13-6A). The drydensity or unit weight is then computed using theformula shown on line 26 of DD Form 1215.Nuclear Moisture-DensityMeter MethodAnother method for determining the moisturecontent and density of in-place soil uses a nuclear13-8
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