Søgning i bogen
Den bedste måde at søge i bogen er ved at downloade PDF'en og søge i den.
Derved får du fremhævet ordene visuelt direkte på billedet af siden.
Digitaliseret bog
Bogens tekst er maskinlæst, så der kan være en del fejl og mangler.
PIERHEADS, QUAYS, AND LANDING-STAGES.
191
of the mole or jetty itself. Its base consists of three courses of masonry
blocks, set in the form of a circle, and inclosing a space which is filled
with mass concrete. The base rests upon a rubble-work deposit brought
up from the sea bottom to within 14 feet of the surface of the water, and
levelled with great care by the aid of divers. The superstructure is of
masonry, and consists of a lighthouse with a cellar compartment used as a
cistern, absolutely water-tight, so carefully was the concrete work carried out.
The pierhead does not actually join up to the jetty ; that is to say, there is
no interlocking bond. A narrow vertical joint separates the two structures so
as to remove all possibilities of fracture arising from unequal settlement.
Pierhead at Sunderland.—The pierhead of the Roker pier was formed
by means of an iron-plated caisson 100J feet long, 69 feet wide, and 26^ feet
deep. The caisson, containing 3500 tons of concrete, was floated out into
position with a draught of 22 feet on to a carefully levelled foundation bed
of concrete bags finished at 23 feet below low water. After being sunk, the
caisson was built up with 15-ton and 25-ton blocks, mass concrete, and
cement-grouted rubble, until, when completed, its weight amounted to 10,000
tons. On top of this, the pierhead superstructure was constructed in block-
work and surmounted by a lighthouse.
Pierhead at Pillau.1 —The new moles at Pillau were built, during the
closing quarter of the nineteenth century, to a type whicli is common on the
Baltic seaboard, viz., that of a rubble mound confined between two lines of
sheet piling connected by iron ties and having a brickwork superstructure.
The width at mean water level between the sheet piling is 31 feet, the summit
width 26 feet, and the height above mean water 10 feet.
Both mole ends have occasionally to withstand very violent attacks by
the sea. The pierhead structures, therefore, were given enlarged dimensions,
the width being increased to 46 feet. In plan the termination of the north mole
exhibits a return in a straight line; at the southern mole, the pierhead front
forms three sides of a regular hexagon. The superstructures are set back
from the ends of piled work by 18 feet in the case of the north mole, and
30 feet in the case of the south mole. The area of the recessed portion in
each case was paved over with brick to a thickness of 3 feet, forming a sort of
terrace or platform. The depth of water at the pierheads was 30 feet when
building operations were commenced. As the piles were driven down to a
depth of 50 feet below water level, no special rubble apron was deemed
necessary.
The south molehead was only just completed in the year 1885, when, in
the month of September, it had to withstand the onslaught of a severe gale,
which blew for two days from the south-west and north-west, gradually
increasing in intensity. The whole front portion of the head, the terrace
work, and a large portion of the sheet piling, were destroyed. Moreover, the
rubble filling inclosed by the lastnamed, in default of restraint, fell away,
depriving the superstructure of its support to such an extent that it leaned
1 Anderson on Prussian Breakwaters, Proc. Pil. Nav. Cony. Milan, 1905