Railway Construction

Railway Construction

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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. 1895 edition. Excerpt: ...boss, the picks are kept open, but when hauled up by the shaft they are kept closed, as shown by the dotted lines. The spider is generally used merely to break up the clay, so as to enable it afterwards to be brought up by ordinary dredgers. The picks are generally made sharp and pointed if used for breaking up gravel, but if the clay is to be retained and brought to the surface they should be broad and flattened out. In some cases they are not only flattened out, but forked. But the proper form to be used must depend chiefly on the character of the material. The ram should not be too heavy, otherwise the picks are likely to be broken. The outside of the well is generally plastered over to decrease the friction in sinking, and a scale showing the height above the bottom of the curb is painted on the outside of the wells. Plumb-bobs hung outside the well should be continually watched during the process of sinking, and when any indication of canting is observed immediate steps should be taken to remedy it. Sinking should be stopped, and the causes ascertained, and, if necessary, divers sent down to clear any obstacle. Canting is sometimes caused by excavation carried unequally at one side of the well, but more frequently by the curb meeting some obstruction at one side, either from stiff clay, boulders, or sunken timber. If canting takes place during the first three lengths sunk it may be generally remedied, but beyond this it is almost hopeless to restore a canted well. When a well has once canted it is obvious that the tendency to cant is increased by the action of the dredger, which excavates precisely where it should not, and avoids that part which requires excavation to restore the well to the perpendicular, as indicated at N, Plate...show more

Product details

  • Paperback
  • 189 x 246 x 3mm | 104g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236967909
  • 9781236967909