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Old Posted Apr 30, 2012, 4:19 PM
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scalziand scalziand is offline
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Join Date: Aug 2007
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The extra space is useful for mechanical equipment and parking. Structurally, the excavation can reach own to bedrock in areas where the bedrock is fairly shallow. In areas where bedrock is very deep, pilings or caissons are used to reach bedrock or a layer of soil that is strong enough to bear the weight of the tower. With pilings, it's not strictly necessary for a large excavation(see Burj Khaliffa). In these cases, the foundation may be excavated purely to gain extra space.
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