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should reduce any waste in time and material at the site. As a result, costs are
lowered and construction time decreases.
Many types of building sections can be prefabricated. For example, entire
walls may be prefabricated for a wooden-frame house. Huge wooden arches are
prefabricated for use as supports in churches, gymnasiums, and other buildings.
Concrete beams, floors, roofs, and wall panels may be precast for many types
of structures. Entire buildings may be constructed in a factory and then
transported to the desired location.
Prefabricated structures are sometimes made by a process called modular
construction, first used in Japan. Modular construction refers to the use of a
standard measurement as the basis for all building materials. The size of the
module may vary considerably from country to country. In the United States,
the basic module is 10 centimeters. All building parts are designed so that each
dimension equals this measurement. Modular parts are also used in buildings
that are not prefabricated.
Site Improvement Methods
If the expected settlement for a proposed structure is too large, then
different foundation support or soil stabilization options must be evaluated. One
alternative is a deep foundation system that can transfer structural loads to
adequate bearing material in order to bypass a compressible soil layer. Another
option is to construct a floating foundation, which is a special type of deep
foundation where the weight of the structure is balanced by the removal of soil
and construction of an underground basement. Other alternatives include site
improvement methods, such as the following:
Soil Replacement. There are basically two types of soil replacement
methods: removal and replacement, and displacement.
The first is the most common approach and consists of the removal of the
compressible soil layer and replacement with structural fill during the grading
operations.
Usually the remove and replace grading option is economical only if the
compressible soil layer is near the ground surface and the groundwater table is
