The Elements of economic geology

Bibliographic data

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

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part IV. Engineering geology

Collection:: Economics Books

EARTHQUAKES 255 -Q 2g g a 1 fo a a J | 3 t fo) 2 0} Nn F 35 } S OF k= it 1] the lateral vibration of earthquakes, but was disturbed by the vertical shocks and swayed badly in the wind. Milne mounted a room on a layer of cannon balls; it also rocked unpleasantly during high wind; but when the cannon balls were replaced by shot a quarter of an inch in diameter, the friction was enough to resist wind action, and the room re- mained at rest during earthquakes which caused violent oscillation in the adjacent ground. Milne concluded that the method is practicable for special purposes, but not for ordinary buildings. The defect of a free foundation is that though the oscil- lation is reduced in speed, the amplitude and actual move- ment may be increased. Weak beds generally form un- satisfactory foundations as their cavities collapse and loose patches become more closely packed. The insecurity of weak foundations can be overcome by tying all parts of the building together, so that it moves as a whole. The Temple of Diana at Ephesus is said to have been built on a marsh to protect it from earthquakes. It like other Greek temples was built on a massive platform that acted like a pontoon and protected the superstructure from waves in the founda- tion. This principle has been adopted by building regulations in earthquake areas; after the destruction of Casamicola in Ischia in 1883, it was enacted that each house must stand on a platform of masonry or cement 27 inches thick for a one-story and 47 inches for a two-story building. Loose foundations on steep slopes are dangerous, as earth- quakes there cause landslips; and the free vibration of the sides of a railway embankment may shake it into piles of sand. ErrecTs OF LATERAL MovEMENT—The lateral movement of the surface in an earthquake dismantles railways by jerk- ing the rails forward and buckling them into serpentine curves; bridges are broken by the girders riding forward, till one end falls off its pier. Bridges may also be destroyed by the vertical upward movement thrusting the piers through the roadway, which is dragged down by the descending movement ; this process is repeated and the roadway is transfixed by the piers. Buildings beside steep hill-sides and cliffs are often seriously damaged owing to the free movement on the hill-face. A

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