In an area underlain by unconsolidated sediments or soils, it
obviously pays to know the depth to bedrock, or if that is not
practical, the depth to the "bearing course" (usually a thick
sand layer or lens) that may serve to support the foundation
(piles) of heavy or high-rise buildings. To know the subsurface
geometry of such competent sand/gravel bodies may significantly
help land-use planners and surely reduce construction costs by a
huge factor.
In the Pudong New Area of Shanghai, China, borehole logs
compiled in a GIS revealed an old river course (now a elongated
sand bar) about 40 m deep, while the surrounding area had a
piling depth of more than 70 m. Consequently, urban planners
were able to situate virtually all high-rise buildings on this
meandering sand bar, resulting in veritably huge cost-savings
for the Shanghai Municipality.
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