Engineering and Contracting . en is of some inter- 2. LoQCjfmif lower drift. By turning up on the jacksthe weight of the upper drift was carriedentirely upon the two longitudinal end of the mud sills were then sawedoff and the next lower section of the sidestruts inserted and carried upon a newmud sill. The jacks were then removedand the 10x10 in. cross timber was drivendown to cover the joint, as shown by The finished appearance of the timbersets of the two upper drifts is shown inFig. 4. The second method, and one whichwas adopted for most of the work, wassuperior to the o
Engineering and Contracting . en is of some inter- 2. LoQCjfmif lower drift. By turning up on the jacksthe weight of the upper drift was carriedentirely upon the two longitudinal end of the mud sills were then sawedoff and the next lower section of the sidestruts inserted and carried upon a newmud sill. The jacks were then removedand the 10x10 in. cross timber was drivendown to cover the joint, as shown by The finished appearance of the timbersets of the two upper drifts is shown inFig. 4. The second method, and one whichwas adopted for most of the work, wassuperior to the one described, and is as fol-lows : The longitudinal timbers were laidon top instead of under the mud sill. Theadvance end of the timbers, as before, rest-ed upon the floor of the upper drift, andthe rear ends were carried on the top ofthe cross brace of a completed bent oftunnel timbering. Chains were wrappedaround the cross brace and timbers, andthe weight was carried by wedging up un-der the chains. In this way two bents of. Encf-Contr Fig. 1—Sketch Showing Method of Excavating and Bracing Tunnel. est. For example, the side struts for thetop heading were carried on a 3x10 sill, the timber set appearing as inFig. 2. Two methods were used for holding upthe upper timbers, the first being as fol-lows: .\ 10x10 in. cross brace was fittedbetween the lower ends of the side postsand immediately above the mud sill, andheld down by heavy cleats at the timbers were then slipped un-der the mud sill, the advance ends of thetimbers being carried on the ground floorof the top drift and the rear ends uponjacks which rested on the floor of the upper timbers were supported. The methodis illustrated in Fig. 5. About midway in the tunnel an oldstone culvert was encountered, which ex-tended diagonally across the work. Theculvert was supported upon a solid layerof transverse 12x12 in. oak timbers, with aflooring of 3x12 in. oak longitudinal plank-ing. Old stumps were als
Size: 1623px × 1539px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherchicago, bookyear19
