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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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 – 2: V
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Khosla’s Method of independent variables for determination of pressures and exit gradient for seepage below a weir or a barrage

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In order to know as to how the seepage below the foundation of a hydraulic structure is taking place, it is necessary to plot the flow net. In other words, we must solve the Laplacian equations. This can be accomplished either by mathematical solution of the Laplacian equations, or by Electrical analogy method, or by graphical sketching by adjusting the streamlines and equipotential lines with respect to the boundary conditions. These are complicated methods and are time consuming. Therefore, for designing hydraulic structures such as weirs or barrage or pervious foundations, Khosla has evolved a simple, quick and an accurate approach, called Method of Independent Variables. In this method, a complex profile like that of a weir is broken into a number of simple profiles; each of which can be solved mathematically. Mathematical solutions of flow nets for these simple standard profiles have been presented in the form of equations given in Figure  and curves given in Plate, wh
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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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