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Chimney demolition
On
23rd February 1994 companies interested in blasting technology, council
officials, many from the excited public and obviously also press and TV
correspondents assembled at the BP oil refinery in the Hamburg Harbour area.
At 2 p.m. it was intended to demolish a 150 metre (450 ft) high chimney
built of reinforced concrete and brickwork by means of blasting technology.
The blasting was also the starting signal for the complete demolition of
the refinery which should be completed in 1995. Until then it was hoped
to have cleared the plot of 100.000 sq. metres (25 acres) in order to build
a container terminal by the Hamburger Hafen und Lagerhaus AG (Hamburg Harbour
and Storage Co.). The interest in the blasting, carried out by Roller Sprengtechnik
(Blasting Technology) Wuppertal was very high because the refinery was still
in operation. Nearby was large storage depot and in the tubes oil and also
petrol was circulating. Any mistake in the execution of the planned procedure
during the blsting would have created the danger of an explosion. It was
intended that the chimney falls into the southerly direction at 13.5 degrees
against the north-south axis. In order that it falls into a prepared bed
of earth walls, an exact preplanning was required. The necessary drilling
and sawing operations in preparation of the blasting were contracted to
Messrs. J. Draeger & Co. Hamburg. Assembly of tilting joints
The 150 metre (450 ft) high chimney was built up
to height of 135 metres (405 ft) of reinforced concrete with the 
remaining
15 metres (45 ft) of brickwork. In order to exclude an implosion of the
chimney and an uncontrolled fall of the brickwork during the blasting
it was intended to assemble two tilting joints. They were intended at
an 170 degree angle almost opposite to each other into openings still
to be provided. The o.d. of the chimney at this level was about 10 metres
(33 ft). The openings had the dimensions (L x H) 2185 x 860 mm (7 x 2¾
ft). From ground level to the lower side of the opening the distance was
1140 mm (45 in) an to the upper side 2000 mm (80 in). The 
vertical
cutting edges on the front side, as can be seen on the picture, were penetrating
for about 400 mm (16 in) into the semicircle in the direction of the intended
fall. Finally clearance cuts had to be sawn at the upper side of the opening
both from inside and from outside in order to cut the chimney wall free
on the opposite side to the fall direction. Prior to the commencing of
the sawing and drilling operations an existing door opening was filled
with concrete up to a height of 1140 mm (45 in). For the loading of the
blasting material 200 holes of 40 mm Ø (1½ in) had to be drilled in the
area of the tilting devices.
Perforating and sawing
It was intended that the 840 mm (33 in) long
vertical cuts
would be produced by 5 perforating holes using drills of 201 mm Ø (8 in)
and that the horizontal cuts would be made by means of a wall saw. During
autumn 1993 initially 4 test cores were taken from both sides of the chimney
at the inner vertical lien of the intended cuts in order to calculate
the basis of the static for the blasting. At a later stage the remaining
16 holes were drilled with a core drilling unit. For the sawing of the
horizontal cuts a Cedima Wall Saw, Type WS-1202, was used. Especially
the cutting of the lower edge of the opening an extremely accurate cutting
was necessary, which had to be exactly levelled, as the tilting joints
were to be mounted on this area. The swing was carried out in three stages
using diamond blades of 800, 1000 and 1200 mm Ø (32, 40 and 48 in). The
guide rail of 1400 mm (55 in) length was supported by two support beams
which were plugged in. After reaching the length to be cut it was remounted.
It followed the upper cut from the inner side from one opening to the
other at a cutting depth of 120 mm (4¾ in). The reinforcement bars at
the inner side of the chimney were thereby cut through. At this stage
the job had to be interrupted as the autumn gales in Hamburg started.
It took until February 1994 when the weather improved to such a degree
that blasting could be done. On 22nd February 1994, therefore, the outer
cut to a depth of 150 mm (6 in) from one opening 
to
the other was carried out in order to cut the outer reinforcement bars.
The 200 holes of 40 mm Ø (1½ in) for the blasting holes were already drilled
the previous week. The blasting was so carefully planned and perfectly
executed that the chimney and the brickwork fell into the prearranged
bed. During the blasting the chimney wall was destroyed to such a degree,
that the broken parts could be removed without any further cutting-up
operations.
Drilling and Sawing of a window opening
The owners of a detached family home felt that the lounge was too dark. In order to have a better view and improve the living quality they decided to have another window. It was planned to have a window with an upper semicircle of 1000 mm (40 in) diameter.
