The Edinburgh Encyclopedia Volume 14 PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1832 edition. Excerpt: ...the same direction, if on being produced it fall within the base, there will in fact be no resisting force, and the wall will stand and support the earth independent of its own weight, and may therefore be made of any open structure that will be firm; a proposition that is true in fact, and of great and well-known importance; for curved walls, and arches to resist earth, are of daily occurrence in civil engineering, though it is evidently not that which the investigation professes to inquire after, which was the thickness requisite for a wall to resist by its weight alone. The oblique action necessarily involves a corresponding modification of the back surface of the wall. Several practical maxims may, however, be deduced from the foregoing mode of investigation. It is evident the wall cannot fall on the side next the earth, therefore, by making it lean backward, not only is the triangle of earth or acting power diminished, but also the wall itself, by having its centre of gravity removed further from the point of conversion at the toe, is the better enabled to resist the thrust. According as the wall is made to batter or lean backwards, therefore, its thickness may be diminished until it becomes a mere pavement over the natural slope of the earth; all that is necessary being to secure the foot of it fromsinking or sliding forwards, and the beds from sliding on each other. But we must take care that the earth behind be well rammed or puddled as the work proceeds, to prevent any settlement from taking place inthe masonry. Nevertheless, builders have very slowly and unwillingly agreed to this form of wall, wishing the security of their work to depend on itself alone They readily agree to the batter in front, but dislike the leaning behind, ..