. Shield and compressed air tunneling . \ G-4-Elbe,Hamburg Highway -n- Rotherhithe,HighwoL|London R Seine mgrr, 5^^ ^?^e-ib-ElmTunnel F-E-Siphon De La Concorde, Railway P°^^5ewer Sco\es •Abod 0 10 20 30 40 SOFecf- eConcreh .li-l 1 I ^^^^ ?BauofHavdna 0 100 200 300 400 SOOFeet ^ I I I I ? I ? K^>^:^^ C-l-Havana Sewer 0 1000 2000 4000 5D00 Feet kys. (Facing Page 66.) ^f^? ?ri>;*^. Fig. 20.—-Cross sections and profiles of some tunnels which have been driven by shields unaer waterways. {Facing Page 66.) CHAPTER VI PRACTICAL MATTERS OF DESIGNA. LOCATION, ALIGNMENT AND GRADIENTS
. Shield and compressed air tunneling . \ G-4-Elbe,Hamburg Highway -n- Rotherhithe,HighwoL|London R Seine mgrr, 5^^ ^?^e-ib-ElmTunnel F-E-Siphon De La Concorde, Railway P°^^5ewer Sco\es •Abod 0 10 20 30 40 SOFecf- eConcreh .li-l 1 I ^^^^ ?BauofHavdna 0 100 200 300 400 SOOFeet ^ I I I I ? I ? K^>^:^^ C-l-Havana Sewer 0 1000 2000 4000 5D00 Feet kys. (Facing Page 66.) ^f^? ?ri>;*^. Fig. 20.—-Cross sections and profiles of some tunnels which have been driven by shields unaer waterways. {Facing Page 66.) CHAPTER VI PRACTICAL MATTERS OF DESIGNA. LOCATION, ALIGNMENT AND GRADIENTS 1. Character of Ground.—The type of tunnel to be used in anyparticular case is governed by the character of the ground inwhich it is to be built. The character of the ground must beknown, therefore, before the design can be commenced. It maybe determined by surface inspection, by consulting geologicalmaps or a geologist, and by borings. 2. Borings,—Borings should be made, not only close to theproposed centerline, but also for several hundred feet on each sideof this line. When the local conditions permit some freedomin the location of the center hne, such borings may disclose abetter location. In waterbearing ground the borings should notbe made immediately above the proposed tunnel location,because they may become sources of blows during construction. 3. Parallel Tunnels.—If the st
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