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Building Design and Construction Handbook - Merritt - Ventech!

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6.24 SECTION SIX<br />

6.3.2 Soil Element<br />

In order to analyze the results of laboratory tests, the concept of the soil element<br />

must be introduced. Figure 6.7 shows an element of soil that can be divided into<br />

three basic parts:<br />

1. Solids—the mineral soil particles<br />

2. Liquids—usually water that is contained in the void spaces between the solid<br />

mineral particles<br />

3. Gas—such as air that is also contained in the void spaces between the solid<br />

mineral particles<br />

As indicated on the right side of Fig. 6.7, the three basic parts of soil can be<br />

rearranged into their relative proportions based on volume <strong>and</strong> mass. Note that the<br />

symbols as defined in Fig. 6.7 will be used throughout this section.<br />

6.3.3 Index Tests<br />

Index tests are the most basic types of laboratory tests performed on soil samples.<br />

Index tests include the water content (also known as moisture content), specific<br />

gravity tests, unit weight determinations, <strong>and</strong> particle size distributions <strong>and</strong> Atterberg<br />

limits, which are used to classify the soil.<br />

Water Content (w). The water content (also known as moisture content) test is<br />

probably the most common <strong>and</strong> simplest type of laboratory test. This test can be<br />

performed on disturbed or undisturbed soil specimens. The water content test consists<br />

of determining the mass of the wet soil specimen <strong>and</strong> then drying the soil in<br />

an oven overnight (12 to 16 hr) at a temperature of 110�C (ASTM D 2216-92,<br />

1998). The water content (w) of a soil is defined as the mass of water in the soil<br />

(M w) divided by the dry mass of the soil (M s), expressed as a percentage (i.e.,<br />

w � 100 M w/M s).<br />

FIGURE 6.7 Soil element <strong>and</strong> the soil element separated into phases.

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