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Building Design and Construction Handbook - Merritt - Ventech!

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6.2 SECTION SIX<br />

Table 6.1 presents a list of common soil <strong>and</strong> rock conditions that require special<br />

consideration by the geotechnical engineer.<br />

6.1.3 Foundation Engineering<br />

A foundation is defined as that part of the structure that supports the weight of<br />

the structure <strong>and</strong> transmits the load to underlying soil or rock. Foundation engineering<br />

applies the knowledge of soil mechanics, rock mechanics, geology, <strong>and</strong><br />

TABLE 6.1 Problem Conditions Requiring Special Consideration<br />

Problem<br />

type Description Comments<br />

Organic soil, highly plastic Low strength <strong>and</strong> high compressibility<br />

soil<br />

Sensitive clay Potentially large strength loss upon large<br />

straining<br />

Micaceous soil Potentially high compressibility<br />

Soil Expansive clay, silt, or slag Potentially large expansion upon wetting<br />

Liquefiable soil Complete strength loss <strong>and</strong> high deformations<br />

caused by earthquakes<br />

Collapsible soil Potentially large deformations upon wetting<br />

Pyritic soil Potentially large expansion upon oxidation<br />

Laminated rock Low strength when loaded parallel to bedding<br />

Expansive shale Potentially large expansion upon wetting;<br />

degrades readily upon exposure to air <strong>and</strong><br />

water<br />

Rock<br />

Condition<br />

Pyritic shale Exp<strong>and</strong>s upon exposure to air <strong>and</strong> water<br />

Soluble rock Rock such as limestone, limerock, <strong>and</strong> gypsum<br />

that is soluble in flowing <strong>and</strong> st<strong>and</strong>ing water<br />

Cretaceous shale Indicator of potentially corrosive groundwater<br />

Weak claystone Low strength <strong>and</strong> readily degradable upon<br />

exposure to air <strong>and</strong> water<br />

Gneiss <strong>and</strong> schist Highly distorted with irregular weathering<br />

profiles <strong>and</strong> steep discontinuities<br />

Subsidence Typical in areas of underground mining or high<br />

groundwater extraction<br />

Sinkholes Areas underlain by carbonate rock (Karst<br />

topography)<br />

Negative skin friction Additional compressive load on deep<br />

foundations due to settlement of soil<br />

Expansion loading Additional uplift load on foundation due to<br />

swelling of soil<br />

Corrosive environment Acid mine drainage <strong>and</strong> degradation of soil <strong>and</strong><br />

rock<br />

Frost <strong>and</strong> permafrost Typical in northern climates<br />

Capillary water Rise in water level which leads to strength loss<br />

for silts <strong>and</strong> fine s<strong>and</strong>s<br />

Source: ‘‘St<strong>and</strong>ard Specifications for Highway Bridges,’’ 16th ed., American Association of State<br />

Highway <strong>and</strong> Transporation Officials, Washington, DC.

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