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. 1904 edition. Excerpt: ...as low as from.2 to % the weight of tne wall; on dry earth, it is about to %; and on sand or gravel, about % to The friction of masonry on a wooden Jc fFI platform, is about of the wt, if dry; and if wet. foil liter forts, shown In plan at c c c, Fig 13, consist la an increase of the thickness of the wall, at its back, at regular inter Ji I vals of its length. We conceive them to be but little better than a 1 l (I S waste of masonry. When a wall of this kind fails, It almost in J variably separates from its counterforts; to which it is connected merely by the adhesion of the mortar; aud to aslight extent, by t lie bonding of the masonry. The table in Art 7 shows that a very small addition to the base of a wall, is attended by a great increase of its strength; we therefore think that the masonry of counterforts would be much better, and more cheaply employed in giving the wall an additional thickness, along its entire length; and Tor the lower third of its height. Counterforts are very generally used in retaiuing-walls by European engineers; butrarely, if ever, by Americans. liuttresses are like counterforts, except that they are placed in front of a wall Instead of behind It; and that then-prolile is generally triangular, or nearly so. They greatly increase it3 Btreugth. but. being unsightly, are seldom used, except as a remedy when a wall is seen to be failing. Land-ties, or long rods of iron, have been employed as a makeshift for upholding weak retaining-walts. Extending through the wall from its face, the land ends are connected with anchors of masonry, cast-iron or wooden posts; the whole being at some dist below the surface. Retaining? Walls WHH curved profiles are mentioned here merely to caution the young engineer against building...
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