Identifier: buildingengineer1616cont (find matches)
Title: Building & engineering news
Year: 1914 (1910s)
Authors: Contractors' and Dealers' Association of California
Subjects: Architecture Building Construction industry Engineering
Publisher: San Francisco : L. A. Larson
Contributing Library: San Francisco Public Library
Digitizing Sponsor: San Francisco Public Library

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nd the core beneath the station arch is nowbeing taken out through the tuiniel section. .\( the east end of the tunnel (he excavadou for severalhundred fee( was through clay and gravel, but is now intochert and altered sandstone. The chert is in layers withclay strata be(ween and requires the same heavy timber-ing as the softer material. A large flow of water fromunderground springs was encountered, but this did nothinder (he work (o any ex(ent. An open joint pipe drainis carried forward beneath (he floor level as the workprogresses and materially aids in keeping the tunnel dry. The progress of (he excavadon through (his materialhas been at the rate of 9 feet per day, but as the driftsare in solid sandstone it is expected that the rate of prog-ress will be increased as less timbering will be required.The heavier tunnel section requires about 30 cubic yardsof excavation per lineal foot, the medium section but 23cubic yards. * -At a point alionr l.siiO feet from the westerly portal, the
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Arch .Section Xear West Portal in Open Cut. The tunnel is excavated (o 12 or 18 inches below railgrade, and trenched along the sides for plumb posts andfor the concrete foofings of (he sidewalls. The muck hasbeen dumped into cars and hauled out by mules. At thewest end (he muck has been used (o fill a ravine beyondthe portal. At the east end the cars were hauled to thesurface through an opening in the roof of the double tubesection on an escalator (a moving endless chain con-veyor and (he muck used to backfill over the sectionsconstructed in open cut. This escalator was later re-moved and the muck is now loaded at the face direct intomotor trucks, which haul it to low lying sections of thecity for dumping and fill. Bunkers and electrically oper-ated elevators are now being constructed at the openings,formerly occupied by (he escala(ors. When those arecomijleted, tracks will be laid in the tunnel and the ex-cavated material hauled out in cars by mules to the ele-vators and then up into

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