| The Jamuna, one of the world's major rivers, rises in the
Himalayas and passes through Tibet, China (known there as Tsang Po) and
India (as Brahmaputra) before entering Bangladesh and finally discharging
in the Bay of Bengal. It is a shifting braided river, consisting of numerous
channels whose width and course change significantly with the seasons.
At the bridge site, for example, the width of the river could vary from
5 km in the dry season to about 12 km during the flood season.
Training the river, to ensure it would continue to flow under
the bridge corridor was one of the most difficult technical challenges
of the project and the most costly of its components.
The River Training Works were undertaken by HAM-Van Oord ACZ Joint Venture
from the Netherlands and were substantially completed in October 1997 |
work on the guide bund slopes |
Delivery of rock to the guide bund site |
The bases of the river training works are two guide bunds,
one on each side of the river, to lead the river through the bridge corridor.
These augment the hardpoints at Sirajganj (being undertaken as part of
another project), and Bhuapur, which has been strengthened as part of the
Jamuna Multipurpose Bridge Project (JMPB).
The bunds are constructed of geotextile fascine mattresses overlaying
dredged soil slopes. They are covered by rocks and overlayed with open
asphalt surfacing. 1.5 million tons of rock, from Bangladesh, India, Bhutan
and Indonesia have been used to provide the coverage for the guide bund
slopes. |
| To counter the considerable scour effects of the river the protection
works on the guide bunds extend to depths of 15 to 18 metres
below datum, where a falling apron has been provided. The additional rocks
dumped in the falling apron should be able to cover the slopes in case
of scour, which may go down to 30 metres below datum.
The large volume of material dredged to form the guide bunds has
been used for reclamation works which provide flood free land for the bridge
end facilities and for resettlement sites. |
A view of the completed West Guide Bund |