Bridging the span of time, are two aqueducts both remarkable engineering feats on their own. In the news recently was the 918-meter Magdeburg water bridge in Germany, the longest aqueduct in Europe, connecting the important Mittellandkanal over the river Elbe to the Elbe-Havel canal. At the other end of the time bridge is the Solani aqueduct, Roorkee, India’s first aqueduct.
Magdeburg Water BridgeThe inauguration of the Magdeburg Water Bridge in October 2003 marked the realization of an idea conceived way back in 1919. Lost in the turmoil of the World War II and the consequent division of Germany, the project regained its prominence with the reunification of the country. Construction was started in 1998 after a whopping 80 years in planning!
The purpose of the project was two-fold -
To overcome the problem of Elbe’s unreliable passage if the river’s watermark fell to unacceptably low levels. Year round East-West traffic is possible for motor-ships and push tows independent of the River Elbe.
Reducing the route by a healthy 12 kilometers. Earlier ships moving between the Midland canal and the Elbe-Havel canal had to detour 12 km through the Rothensee lock, the Elbe and the Niegripp lock.
The main bridge is a continuous girder and consists of a through bridge and the two exterior main girder boxes. The main girder boxes are divided into 11 constructional sections with lengths from 13.8 meters up to 30 meters. The cross-section consists of the upper boom, the bottom boom, the sides of the through bridges as well as the post and diagonals of the framework.
A steely approachThe approach bridge is also constructed as a continuous girder of 16 sections with equidistant spans of 42.85 meters. The through bottom of the approach is longitudinally oriented as a result of the small spans (7 longitudinal girders). The lateral sides are reinforced at the upper edge with a box girder, which at the same time is a traffic route.
For the steel construction of the main bridge and the construction of the approach bridge respectively 10,000 tons and 14,000 tons of heavy plate type S355J2G3 (Certificate 3.1.C) were used. The plate thicknesses ranging from 10 to 80 millimeters, widths up to 4,500 millimeters and lengths up to 28,000 millimeters were used. About 6,000 tons of the total tonnage was longitudinally profiled plates that is, plates with a continuous variable thickness in the longitudinal direction.
The Solani River Aqueduct
The Ganga Canal
The most spectacular section is the 27 kilometers downstream from the Haridwar intake to Roorkee, situated in the foothills of the Himalaya, 160 kilometers north-east of Delhi. The canal drops through four 2.7 meter falls, each with a former navigation lock. Two large aqueducts carry the Ranipur and Pathri rivers over the canal whilst the Ratmau River is crossed on the level with an attendant spillway which is opened out during the monsoon.
A graceful beautyThe Solani River, an intermittent stream, was crossed on a magnificent arched aqueduct ornamented with lions and with approach embankments over 2 miles long. The aqueduct was built 175 feet wide — 150 feet for the canal itself, the rest for a two-lane road and railings. The 980 feet long aqueduct consisted of 15 spans of 50 feet each separated by 10 feet wide piers, the trough being 175 feet wide.
Engineering MarvelStones sunk nearly 20 feet under the bed of the river support the arches, and the work was done so well that upon removal of the ‘centering’ (the wooden frameworks used in constructing the arches) the keystones sagged only an eighth of an inch. Over 11 million cubic feet of masonry, 85 million bricks were used in the aqueduct. The frontispiece showed two elegant details: decorative iron railings imported from England and pairs of large stone lions, made locally and placed at each end of the aqueduct.
The Solani river bed consists of sand of average diameter of 0.25 millimeters and carries maximum flood flow of 80,000 cusecs. The channel in this reach runs in filling. The embankments here are about 5 kilometers long and are held on one side by masonry walls, 55 feet high and supported on walls. These are provided on water face with a flight of steps up to 3 feet above canal bed level. To make it strong enough to withstand the yearly floods, the Solani Aqueduct had to be supported on 300 cubes of brick sunk 6 meters below the river bed. The technique of sinking cubes of masonry was one familiar to Indian engineers for centuries.
Keeping up with timeDuring re-modeling of canal in 1956, the bed was lowered by 6 inches by replacing the old clay bed over laid brick on edge by 3 inches cement concrete.1:2:4 which enabled passing of an increased discharge of 10,500 cusecs.
The World Bank in 1984 agreed to help fund the reconstruction of the canal, known as the ‘upper’ Ganges Canal. The reconstruction of the Upper Ganges system included a new Solani Aqueduct, a bridge of pre-stressed concrete beams. The initial plan was to demolish the old bridge, but the demolishing costs were too high, simply because the work was so difficult—a huge credit to the original construction and design.
Today the old bridge stands nearby—gracefully arched plastered brick neatly dated with a plaque from the 1840s. The decorative iron railings have disappeared and the stone lions have been moved upstream to a new location.