oa Civil Engineering = Siviele Ingenieurswese - Geophysical surveys for foundations in South Africa with special reference to the sink-holes in the dolomite south of Pretoria
Geophysical methods of site exploration should be used whenever a saving of time and cost can be accomplished. Depth of solid bed-rock can readily be obtained by an electrical resistivity survey; igneous dyke and sill intrusions are located by magnetic survey; the gravitational method is applied for determining safe and dangerous zones for sink-holes in dolomite; and fault-zones are traced by the electromagnetic method. Sink-holes may occur in dolomite where excess water causes loose material at the surface to slump into near-surface cavities. If the dolomite over an extensive area is covered by younger formation such an area is considered safe. It has been found possible to delineate both safe and dangerous zones in the dolomite area south of Pretoria by extensive geophysical surveys.
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