26 Ground improvement by deep vibratory methods
tunnel at its deepest has its crown 17.7 m below water level and covered
by 3.5 m of sand. To create a safe foundation and to minimize the lateral
pressure, the in-situ and dredged sand below and around the tunnel was
compacted. Some 125,000 lin.m of deep compaction were carried out in
1968 under difficult site conditions.
One example for the advantageous use of the deep vibratory methods in
harbor construction is the foundation works for the quay wall of Thuwal
harbor on the west coast of Saudi Arabia. About 160,000 lin.m of vibro
flotation in loose coral sands were carried out in 1978 for this project from
a working ship equipped with five vibrator units. Numerous and often quite
extensive foundation works employing deep vibratory methods were carried
out on the Arabian peninsula starting in the early 1970s for the infrastructure as it exists today: large power plants and desalination units and impressive facilities for the petrochemical, steel, aluminum, and cement industry.
Vibro compaction was and is regularly recommended by the consulting engineers in this area when, besides the cost advantage of the system, the groundwater is particularly aggressive against concrete. This concrete attack, which
is especially strong on piles, can be better controlled and indeed avoided by
the choice of a shallow foundation placed on improved ground whereby the
direct contact with the aggressive groundwater can be avoided or minimized.
Although the first phase of a large grain terminal at Kwinana at the west
coast of Australia was founded in 1969 on driven piles, the owner opted
for vibro compaction with depth vibrators for the second phase of the
project. Situated near Perth, this grain terminal with its loading facilities is
among the largest of its kind. The in-situ fine-grained sand was compacted
to a depth of 24 m to safely carry the heavy loads of the silos, to reduce
the overall settlement of the structures, and to increase their safety against
earthquakes. After just 14 months, some 260,000 lin.m of vibro compaction was completed in 1974. The foundation works for this impressive grain
terminal won the 1974 Construction Achievement Award of the Australian
Federation of Construction Contractors which helped the method of vibro
compaction to gain acceptance also on the fifth continent (see Figure 2.16).
This was followed by some interesting works at Botany Bay Harbour south
of Sidney and then some vibro replacement works for the foundation of
railway embankments on soft ground.
In 1962, the Ughelli Power Plant in Nigeria had its foundations laid using
the vibro compaction method. In 1972, the method was again used for the
foundation of the Massingir Dam in Mozambique. Complex compaction
work became necessary for the construction of the Jebba Dam in Nigeria
in 1982 and 1983, where deep underlying noncohesive, loose river deposits
had to be compacted up to 90% relative density to fulfill earthquake design
requirements. The necessary densification to depths of 45 m together with
the large volume to be compacted in a relatively short time pushed the limits
of the technology and the existing equipment. It was only achieved by a combination of vibro compaction to 30 m with deep blasting for the sand below.
tunnel at its deepest has its crown 17.7 m below water level and covered
by 3.5 m of sand. To create a safe foundation and to minimize the lateral
pressure, the in-situ and dredged sand below and around the tunnel was
compacted. Some 125,000 lin.m of deep compaction were carried out in
1968 under difficult site conditions.
One example for the advantageous use of the deep vibratory methods in
harbor construction is the foundation works for the quay wall of Thuwal
harbor on the west coast of Saudi Arabia. About 160,000 lin.m of vibro
flotation in loose coral sands were carried out in 1978 for this project from
a working ship equipped with five vibrator units. Numerous and often quite
extensive foundation works employing deep vibratory methods were carried
out on the Arabian peninsula starting in the early 1970s for the infrastructure as it exists today: large power plants and desalination units and impressive facilities for the petrochemical, steel, aluminum, and cement industry.
Vibro compaction was and is regularly recommended by the consulting engineers in this area when, besides the cost advantage of the system, the groundwater is particularly aggressive against concrete. This concrete attack, which
is especially strong on piles, can be better controlled and indeed avoided by
the choice of a shallow foundation placed on improved ground whereby the
direct contact with the aggressive groundwater can be avoided or minimized.
Although the first phase of a large grain terminal at Kwinana at the west
coast of Australia was founded in 1969 on driven piles, the owner opted
for vibro compaction with depth vibrators for the second phase of the
project. Situated near Perth, this grain terminal with its loading facilities is
among the largest of its kind. The in-situ fine-grained sand was compacted
to a depth of 24 m to safely carry the heavy loads of the silos, to reduce
the overall settlement of the structures, and to increase their safety against
earthquakes. After just 14 months, some 260,000 lin.m of vibro compaction was completed in 1974. The foundation works for this impressive grain
terminal won the 1974 Construction Achievement Award of the Australian
Federation of Construction Contractors which helped the method of vibro
compaction to gain acceptance also on the fifth continent (see Figure 2.16).
This was followed by some interesting works at Botany Bay Harbour south
of Sidney and then some vibro replacement works for the foundation of
railway embankments on soft ground.
In 1962, the Ughelli Power Plant in Nigeria had its foundations laid using
the vibro compaction method. In 1972, the method was again used for the
foundation of the Massingir Dam in Mozambique. Complex compaction
work became necessary for the construction of the Jebba Dam in Nigeria
in 1982 and 1983, where deep underlying noncohesive, loose river deposits
had to be compacted up to 90% relative density to fulfill earthquake design
requirements. The necessary densification to depths of 45 m together with
the large volume to be compacted in a relatively short time pushed the limits
of the technology and the existing equipment. It was only achieved by a combination of vibro compaction to 30 m with deep blasting for the sand below.