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<br />8 <br /> <br />~ <br /> <br />'-" <br /> <br /> <br />1tl\~~ <br />/." "." "~\' '.., <br />.;' .. f.' : \ . <br />. . '. .... . <br /> <br />FIGURE 2.5-6 TRANSMISSION OF COMPACTION FORCE <br /> <br />The pressure directly under the foot of the <br />tool is fairly"uniform; however, as the depth <br />increases, the impact is spread out over a <br />greater area and has less effect on the soil. <br />Also, in the lower parts of the sample, the <br />impact is not great enough to cause the grains <br />to break or move against each other. <br /> <br />The examples shown in Figures 2.5-3 through <br />2.5-6 illustrate why it is necessary to place a <br />soil in controlled layers in order to obtain a <br />uniformly dense material. The thickness of <br />the layer that can be effectively compacted <br />depends on the type and weight of the <br />equipment being used. Figures 2.5-7 through <br />2.5-11 show various types of compaction <br />equipment. <br /> <br />2.5-2 VIBRATION AIDS IN COMPACTION <br />Soil materials having contact surfaces that <br />resist particle-ta-particle movement can be <br />compacted more effectively when vibration <br />is applied. Usually rocks, cobble, gravel, and <br />sands require vibration in addition to impact <br />force in order to obtain the desired compac- <br />tion. Figure 2.5-11 shows a vibrating roller <br />which is equipped with a mechanism that <br />causes the roller drums to vibrate as it passes <br />over the material being compacted. <br /> <br />2.5-3 COMPACTION EQUIPMENT <br />Some of the more common compaction <br />equipment is shown here. <br /> <br /> <br />FIGURE2.5-7 - POGO STICK, SIMILAR TO TAMPING TOOL. -Is <br />used in tlgllt 'Spots not accessible to lareer equipment. <br /> <br /> <br />FIGURE 2.S.9 - SHEEPSFOOT ROLLER. - Used in open areas. <br /> <br />- <br /> <br />J ~_ <br /> <br />., <br /> <br />FtGURE 2.5-10 - SELF-PROPELLED ROLLER. - Used In open <br />areu. <br />