File:Image from page 113 of "Shield and compressed air tunneling" (1922).jpg

English: Identifier: shieldcompressed00hewerich

Title: Shield and compressed air tunneling Year: 1922 (1920s) Authors: Hewett, Bertram Henry Majendie Johannesson, Sigvald, joint author Subjects: Tunneling Publisher: New York [etc.] McGraw-Hill book Co. Contributing Library: Prelinger Library Digitizing Sponsor: Internet Archive

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Text Appearing Before Image: 96 SHIELD TUNNELING B. CAST IRON LINING 5. General Description.—In its usual form cast iron lining is acylindrical structure with a circular cross-section Iniilt up of aseries of rings, and each ring is made of a number of sections. Figure 27 shows a cast iron lining erected. Each segmenthas a web or skin conforming to the curvature of the tunnel andprovided with flanges along its four edges. When erected theskin forms an enveloping cylinder which is stiffened by the cir-cumferential flanges. The segments and rings are connectedby means of bolts through the flanges.

Text Appearing After Image: Fig. 28.—One segment of a cast iron lining. 6. General Details (Fig. 28).—In British linings the skinhas a uniform thickness from flange to flange while in Americanlinings the thickness is often increased toward the flanges. Forcasting reasons the circumferential flanges are tapered and theend flanges, which are commonly called the cross or horizontalflanges, are usually of identical cross-section. To secure fullbearing for the bolt heads and nuts on the tapered flanges thebolt holes are bossed. To provide means for waterproofing thejoints the flanges are recessed along their inner edges so as toform, when erected, a groove between adjacent segments whichmay be filled with a waterproofing material. Exceptions to thisarrangement will be mentioned later. Triangular bracings orfeathers are frequently used to stiffen the flanges against theskin. All intersecting surfaces are filleted. For grouting pur-poses a tapped and plugged hole is generally provided in the skinof each segment. 7.

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