The Elements of economic geology

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Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

Usage license:: Get license information via the feedback formular.

Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part IV. Engineering geology

Collection:: Economics Books

254 ECONOMIC GEOLOGY Similarly in the earthquake of 1923 motor cars at Yoko- hama were tossed into the air and fell upside down, and houses near the edge of a cliff were flung over it. Fortunately the meizoseismic area of most earthquakes is comparatively small. The main damage in districts farther from the origin is due to the yielding of insecure foundations, to the collapse of buildings of unsuitable design, or to fire or earthquake wave. Anti-earthquake building design has been based upon two opposite principles. The first aims at keeping the structure so light and elastic that it withstands shaking like a basket ; the other plans a structure so firm and rigid that it is as difficult to shake to pieces as a box. The basket system was tried in Japan, but was unsatisfactory, as though the building was safe, the play of the framework cracked the plaster, overthrew light objects, and created terrifying noise and dust. Extreme rigidity has been secured by interlocking bricks and strong ties, which must be broad to prevent them cutting the structures attached to them. Thus in 1880 a fire destroyed part of Yokohama, and left the brickwork chimneys as isolated stacks. They were uninjured by a subsequent earthquake, when adjacent houses were destroyed by the fall of the chimneys, which were cut through by the bands that attached them to the floors. C. Loose versus Firm Founparions—There has been much discussion as to whether a loose or firm foundation is the safer. A loose foundation may absorb the shock. Milne found that the vibration caused by the fall of a weight of 2000 1b. from a height of 35 feet on to soft ground was barely perceptible 40 feet away, whereas the same blow on hard clay produced a dislocation of about zisth of an inch at 250 feet away. In the Tokyo Earthquake of 1923 of buildings on hard soil only 6 per cent. collapsed, as against 10 per cent. of those on soft soil ; but on hard soil 88 per cent. suffered some injury as against 81 per cent. on soft soil. Many attempts have been made to protect buildings from earthquakes by a free foundation. As Japanese light- houses suffered from the scattering of oil from the lamps during earthquakes Stevenson designed a lighthouse resting on a platform of cannon balls, hoping that their movement might absorb the vibration. The lighthouse was freed from

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