Traffic & Highway Engineering Book by Nicholas J. Garber

Traffic and Highway Engineering, Fourth Edition
Nicholas J. Garber and Lester A. Hoel Click here to download

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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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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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What is Soil in Geotechnical Engineering.

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Definition of Soil The word ‘soil’ is derived from the Latin word solium which, according to Webster’s dictionary, means the upper layer of the earth that may be dug or plowed; specifically, the loose surface material of earth in which the plants grow. The above definition of soil is used in the field of agronomy (The application of soil and plant sciences to land management and crop production) where the main concern is in the use of soil for raising crops. In geology, earth’s crust is assumed to consist of unconsolidated sediments, called mantle or regolith, overlying rocks. The top soil contains a large quantity of organic matter and is not suitable as a construction material or as a foundation for structure. The top soil is removed from the earth’s surface before the construction of structure. The term ‘ soil ’ in the soil engineering is defined as an unconsolidated material , composed of solid particles , produced by the disintegration of rocks . The void space...
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