Abstract
THIS is a project of the Tennessee Valley Authority, and owing to the proximity of the site to the secondary zone of disturbance of the New Madrid earthquake of 1812, all structures forming part of the main dam were proportioned to resist seismic disturbances (Earthquake Notes, 14, Nos. 3 and 4 ; June 1943). The following seismic loadings were adopted: for mass structures of great rigidity an equivalent inertia force equal to 0-05 g. and for less rigid structures an inertia force varying from 0-06 g. to O'lO g., based upon rational calculations of the dynamic action of the structure. The seismic increase in reservoir pressures was calculated by the Westergaard formula, using an earthquake acceleration of 0-05 g. For the two large retaining walls at the end of the earth embankment at each side of the river, special investigations were undertaken to establish the proper seismic loading. An extensive programme of shaking-table tests was conducted at Leland Stanford University by Prof. L. S. Jacobsen. On the basis of these tests an equivalent inertia force of 0-18 g. was applied to the conventional Coulomb wedge, the point of application being about 0-60 the height above the base. For structures sustaining hydraulic loads, the increase in overturning moment due to seismic effect was only 7 per cent, while the corresponding increase for structures such as retaining walls carrying earth loads was of the order of 35 per cent, Maps recently sent out by the State Geologist of the State of Missouri indicate large anomalies in both gravity and vertical magnetic intensity in Stoddard County, the locality of the great New Madrid earthquake of 1811. Whether there is any significance in the coincidence is not established, but the seismic precautions mentioned above do not appear to lack wisdom.
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The Kentucky Dam, Power House and Lock. Nature 152, 352 (1943). https://doi.org/10.1038/152352a0
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DOI: https://doi.org/10.1038/152352a0