Engineering Wonders of the World
Volume I

THE TUBE RAILWAYS OF LONDON. 237 by this method the timber used is left per- manently in the ground. In the case of a stairway shaft at Kenning- ton Road Station, a shield of simple form was used. The excavators loosened the ground at the cutting edge‘of the shield by working it with bars and picks ; while ten bottle screw- jacks, placed round the cir- one at the junction of each pair of cutting-edge segments, were screwed so as to force the shield down into the gravel, the upper ends of the jacks bearing against the bottom of the last shaft ring. When the shield had been advanced sufficiently for an 18-inch-deep ring to be fixed, the screw-jacks were successively removed and replaced by the segments of the new ring. The Shield Method. cumference, The greatest success attended this method of working, which, it is believed, is quite novel as regards shaft-sinking in the manner effected and under the conditions named, for it was found that the shaft when completed was perfectly plumb from top to bottom. There is every probability that, when en- gineers get to know of its feasibility, the shield method will find general favour, since even this small experience has proved the system to be cheaper, „ * x Success, quicker, and better in every respect than the old-fashioned method of loading shafts, which in so many cases has been productive of considerable delays through the shaft being bound on one side or the other, and has also produced costly fractures of the shaft segments. contractors’ electric haulage train. (Photo, Bolas and Co., 5 and 7 Old Queen Street, £.TF.)