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Shield and Compressed Air Tunneling (Classic Reprint)
Bertram Henry Majendie Hewett
No preview available - 2017
air lock air pressure angles Average progress axis Blackwall Blackwall tunnel bolts bottom built bulkhead calking carried cars cast iron lining center line circumferential compressed air concrete lining construction Copperthwaite cost cross-section cutting edge decompression diaphragm door East River East River tunnels engineer equation erection erector excavation external diameter face flange gravel groove grout grummets heading holes horizontal hydraulic internal leakage length linear foot London clay material method normal air Pennsylvania Railroad pipe placed plant plates platform plumb-bob possible Railroad tunnels ring rock roof shield Rotherhithe tunnel sand segments Sewer shaft shield driven tunnel shield jacks shove shown in Fig side silt single track skin soft ground square inch steel Street stress surface taken tensile stress thickness thrust timbering Top of tunnel Tower Subway transit tunnel lining tunnel shield tunnels driven usually vertical waterbearing ground weight width
Page 422 - ... shall be at the average rate of not more than two pounds per minute ; (d) Where the air pressure is more than thirty-three pounds per square inch, decompression shall be at the average rate of not more than one pound per minute; (e) Where the air pressure is more than fifteen pounds per square inch, a stage decompression shall be used in which a drop of one-half of the maximum gauge pressure shall be at the rate of five pounds per minute. The remaining decompression shall be at a uniform rate...
Page 110 - Two sets of two bars shall be cast from each heat, one set from the first and the other set from the last iron going into the castings. Where the heat exceeds twenty tons, an additional set of two bars shall be cast for each twenty tons or fraction thereof above this amount.
Page 418 - C. Are there any Indications of Disease of this Organ or of the Blood Veesels? A. IS THEfSIGHT good? B. Is the Hearing good? is THE APPLICANT
Page 422 - ... compressed air shall be permitted to pass from the place in which the work is being done to normal air, except after decompression in the intermediate lock as follows: A stage decompression shall be used in which a drop of one-half of the maximum gauge pressure shall be at the rate of five pounds per minute. The remaining decompression shall be at a uniform rate and the total time of decompression shall equal the time specified for the original maximum pressure.
Page 225 - Congress repealed all previous acts authorizing transfers and stipulated that "no money appropriated for one purpose shall hereafter be used for any other purpose than that for which it is appropriated."72 Nevertheless, during periods of great emergency, Congress delegates broad transfer authority to the executive branch.
Page 259 - ... Stockwell by mechanical power was constructed and held in readiness for use; but the method first tried was found to work well and was employed throughout. The shield having been brought to the water-bearing strata, a small heading was driven at the top in advance of the shield, stout poling-boards being used to support the top, resting at one end upon the forward end of the shield ; the heading was then widened out and the polings continued until about three-fourths of the circumference and...
Page 421 - On the other hand, decompression should evidently be as rapid as is possible, consistently with safety. A pressure of 1 to 1.25 atmospheres above normal corresponds to from 2 to 2.25 times the normal atmospheric pressure; but the volume (not the mass) of gas (measured at the existing pressure) which would be liberated if the whole excess of gas present in supersaturation were given off is the same whether the absolute pressure is reduced from two to one atmospheres, or from four to two, or from eight...
Page 110 - This is a bar IJ4 in. in diameter and 15 in. long. It shall be prepared as stated further on and tested transversely. The tensile test is not recommended, but in case it is called for, the bar as shown in Fig.
Page vii - So much tunneling has been done with the aid of the shield and the art of such work has been developed to such a point that it is possible now to formulate, to some extent at least, certain principles and rules of practice on which to base the design and construction methods of future work.
Page 204 - ... small scale. The Author, some years later, devised the grouting apparatus first used in the City and South London tunnels, Fig. 17, Plate 2. A cylindrical vessel, capable of withstanding a pressure of 70 Ibs. or 80 Ibs. per square inch, has through its axis a shaft or spindle working in a stuffing-box at each end of the vessel, and provided at one or each end with a handle outside, and carrying, inside the vessel, a number of paddles. The lime and water are introduced through an opening at the...