How to Manage Disaster

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Lane’s Weighted Creep Theory

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Bligh, in his theory, had calculated the length of the creep, by simply adding the horizontal creep length and the vertical creep length, thereby making no distinction between the two creeps. However, Lane, on the basis of his analysis carried out on about 200 dams all over the world, stipulated that the horizontal creep is less effective in reducing uplift (or in causing loss of head) than the vertical creep. He, therefore, suggested a weightage factor of 1/3 for the horizontal creep, as against 1.0 for the vertical creep. Thus in Fig–1,  the total Lane’s creep length (L l ) is given by L l = (d 1 + d 1 ) + (1/3) L 1 + (d 2 + d 2 ) + (1/3) L 2 + (d 3 + d 3 ) = (1/3) (L 1 + L 2 ) + 2(d 1 + d 2 + d 3 ) = (1/3) b + 2(d 1 + d 2 + d 3 ) To ensure safety against piping, according to this theory, the creep length Ll must no be less than C1H L , where H L is the head causing flow, and C 1 is Lane’s creep coefficient given in table –2 Table – ...
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Bligh’s Creep Theory for Seepage Flow

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According to Bligh’s Theory , the percolating water follows the outline of the base of the foundation of the hydraulic structure. In other words, water creeps along the bottom contour of the structure. The length of the path thus traversed by water is called the length of the creep. Further, it is assumed in this theory, that the loss of head is proportional to the length of the creep. If HL is the total head loss between the upstream and the downstream, and L is the length of creep, then the loss of head per unit of creep length (i.e. H L /L) is called the hydraulic gradient. Further, Bligh makes no distinction between horizontal and vertical creep. Consider a section a shown in Fig above. Let H L be the difference of water levels between upstream and downstream ends. Water will seep along the bottom contour as shown by arrows. It starts percolating at A and emerges at B. The total length of creep is given by L = d 1 + d 1 + L 1 + d 2 + d 2 + L 2 + d 3 + d 3 = (L 1 +...
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The 10 Longest Arch Bridges in the World...

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Arch bridges are one of the oldest types of bridges. The oldest known bridge in the world known to still be in use is the Caravan Bridge, a stone arch bridge across the Meles River in Izmir, Turkey. It was built in 850 B.C. Roman engineers built many arch bridges, quite a few of which are still standing. Probably the most famous is the Pont du Gard, an aqueduct bridge in southern France. Built in the first century A.D., it features three tiers of limestone arches and stands 48 meters high and 275 m long. The Alcantara Bridge, a stone arch bridge built by the Romans in Spain in 106 A.D., has been repaired numerous times after suffering damage during various wars, but it is still serving pedestrians. It is 45 m high and 182 m long. The oldest bridge in the city of Rome itself is the Pons Fabricius, a 62-m-long stone arch bridge over the Tiber River, built in 62 A.D., that is still in use by pedestrians. Many arch bridges from the Medieval and Renaissance periods are still funct...
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