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AP World History: Modern was designed to help students develop a greater understanding of the evolution of global processes and contacts as well as interactions between different human societies. The course advances understanding through a combination of selective factual knowledge and appropriate analytical skills.
Section through railway track and foundation showing the sub-grade. Grading in civil engineering and landscape architectural construction is the work of ensuring a level base, or one with a specified slope, [1] for a construction work such as a foundation, the base course for a road or a railway, or landscape and garden improvements, or surface drainage.
In transport engineering, subgrade is the native material underneath a constructed road, [1] pavement or railway track (US: railroad track). It is also called formation level . The subgrade provides support to the subbase level and acts as an integral load-bearing layer.
A railway track (CwthE and UIC terminology) or railroad track (NAmE), also known as permanent way (CwthE) [1] or "P Way" (BrE [2] and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers (railroad ties in American English) and ballast (or slab track), plus the underlying subgrade.
Asphalt batch mix plant A machine laying asphalt concrete, fed from a dump truck. Asphalt concrete (commonly called asphalt, [1] blacktop, or pavement in North America, and tarmac or bitumen macadam in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. [2]
In addition to minimising construction cost, other factors influence the placement of cut or filled sections. For example, air pollutants can concentrate in the valleys created by the cut section.
An embankment is a raised wall, bank or mound made of earth or stones, that are used to hold back water or carry a roadway. A road , railway line , or canal is normally raised onto an embankment made of compacted soil (typically clay or rock-based) to avoid a change in level required by the terrain , the alternatives being either to have an ...
Slab pull is a geophysical mechanism whereby the cooling and subsequent densifying of a subducting tectonic plate produces a downward force along the rest of the plate. In 1975 Forsyth and Uyeda used the inverse theory method to show that, of the many forces likely to be driving plate motion, slab pull was the strongest. [1]