March ,. 19, 1915. THE COLLIERY GUARDIAN. 595 LINING SHAFTS WITH FERRO-CON- CRETE SEGMENTS OF Z SECTION.* By M. G-fllieaux. - ( Of all ,the systems employed for lining shafts, ferro- concrete has the. advantage of being the cheapest in proportion to' the resistant, properties of the material, and in respect of the. space occupied by the lining, a thickness of 8 to 10 in. being as efficient as 14 in. of brickwork.. The plan of using, segments with butt top and bottom joints, which is the usual method, is attended with certain inconveniences, including ‘ leaky joints and the necessity for providing temporary sup- ports or staging when, as is generally the case, the work of lining the shaft is commenced at the top and con- tinued downward. To obviate these defects, the author has devised a form of construction in which the seg- ments are of Z section, each being hooked on to the next higher member, and thus making closer joints than are possible in the ordinary way. The method of attaching the segments to form a lining is illustrated in fig. 1. A strong crown ring is let into the,standing rock at the head of the lining, and when the sinking has sufficiently progressed, a series of specially shaped segments is suspended from this ring, to form the first ring of tubbing. The sectional, shape of the segments is that of an angular S or Z, the rib (1, fig. 1) forming the upper hook being directed outward, and that forming the lower hook inward. ' As the sink- ing proceeds fresh rings of segments are hooked on to those already in position; and when several rings have been set up, the annular space (2, fig. 1) between the lining and the shaft wall is plugged, and a semi-fluid mixture of cement and sand is injected into the cavity Fig. 1.—Vertical Section of Lined Shaft. Fig. 2.—Cross Section through Lining. through holes (3) provided in the segments. "When the cement has set, it binds the lining firmly to the external rock, and fresh segments can be hung on below without fear of straining the upper portion. The^ reason for the adoption of the S or Z section was that this type is the one most suitable for obtaining satisfactory auto-suspension, though in certain special cases ribs of X or I section, arranged at right angles to the shaft wall, might be preferable. Fig. 3 gives a vertical section of the Z type of seg- ment, showing a downwardly inclined hole in the lower portion of the segment for the injection of the cement grouting, and also for suspending the segments whilst being lowered into position, and for the insertion of clamping irons. The vertical joints are stepped, as shown in fig. 2, to give a better hold, and ensure tight- ness; and the outer surface of the segments is roughened to enable the cement grouting to adhere more firmly. The reinforcement consists of S irons, extending from the top to the bottom rib of the segment, with auxiliary simple hooks, arranged symmetrically to the first-named, in the nose pieces and narrow or throat sections. With regard to the weight and dimensions, it is advantageous that each unit should cover the largest possible surface, within reasonable limits in point of weight. Usually it is not desirable for the weight of a segment to exceed 5 to 6 cwt.; and the corresponding superficial area is about 7 sq. ft. To facilitate the injection, of thick grouting, the inject- ing holes are tapered outward, and sloped in the same direction. Their position should be as low down in the segment as is practicable, and their diameter should correspond to that of the feed pipe. To enable the segments to be hooked on to - those above, a small amount of . play must be allowed for. between, the upper sloping, surface of the top. rib, and the corresponding slope of the bottom recess into which it fits, so that the nose can slip'into the channel pre- pared for it without these upper surfaces seizing. The same applies to the lower slope of the bottom rib and * Bull. Teclin. Association des Ingenieurs sortis de 1’Ecole Polytechnique de Bruxelles. • the correspondinglower slope of the .recess.in the upper; portion of the next • lower ‘ segment. ■ -This play is' indi- cated by the dotted lines in fig. 3. .. la -; The key segment of a ring of the ..tubbing is‘ neces-- sarily of somewhat different shape to the rest, to facili- tate its< insertion. With this object, :the inner flange on one lateral edge of the first segment of .each; -ring (fig. 4) is suppressed, the -edge being, bevelled inwards. This, arrangement, it, is true, results in..a /weak spot .in each ring; but the effect 'of this may be minimised by staggering these joints. ■ The segments are cast in ordinary moulds (figs. 5 and 6), wooden liners being inserted to produce the necessary recesses and shape the nose pieces. To obviate the need for cutting through the segments to provide lodgments for the ends of the traverses for the shaft compartments, a prismatic core of slightly larger size may be inserted into each, mould, and the passage thus formed in each block may be used for the introduc- tion of the cement grouting, or the reinforcing irons may be suppressed at the point where the hole is intended to be. cut. Any mixture capable of furnishing a good concrete may be employed for making the segments; for example, equal parts of small gravel and quarry dust, with an addition of 6 cwt. of cement per cu. yd. The mixture should be made up with the smallest possible quantity of water, in order to enable the blocks to be taken out Sheet iron 4 mm. Outer xrib of mould. 40 mm. sq. 0 ids’ id o *S°z iw •ido? S&b Cotton Fig. 3.—Vertical Section of a Z Segment. 6S? Wood fittings Fig. 5.—Vertical Section of Mould. Fig. 4.—Joint of Key Segment. of the moulds without delay. The author does not consider granulated slag a good substitute for quarry dust. .. The concrete is introduced in an almost dry state by small quantities at a time, and is wrell rammed. The reinforcing irons are laid on. the concrete one by one, and as soon as the segment is completed it is taken out of the mould. The suspension ring or crown consists of a channel iron ring (fig. 7) carrying radial external arms, which are bedded perfectly horizontal in a thick layer of good concrete at the mouth of the shaft. Tie rods (old pit rail ends, or the like) are driven through the unused cement channels in the segments into the standing rock. Being subsequently embedded in the grouting, they serve as a reinforcement, and they may, to some extent, play the part of spikes helping to hold the segments in place, though this is not their real purpose, and must not be counted upon. In order to prevent or. correct any deformation of the circular section of the- shaft, it is well to. put in after the: segments a rigid ring of the same.diameter;as the-shaft. . The. bottom rib; of the. last, ring of ..tubbing should be protected from injury, through blasting debris, by brush- wood. faggots . held in. place by. special hooks , (fig.. 8), which are suspended from the..central channel of' each segment. The segments are lowered down the' shaft,■ and put into position by means of a cradle attached to the winch .hooka. - It is triangular in shape, -and bent over at the -bottom to form a support for the block. . .To prevent: the-latter from slipping, a hinged ledge at the bottom, of the cradle is turned up, and secured by means of a wire: cord passed through the central channel. A hinged claw at the top of the cradle hangs down: over and secures the upper rib of the. segment, while .the block is being lowered into the shaft, but is drawn up to enable the segment to bo put in position, which is done by pushing the block up against the recess in the lowest ring of tubbing, and then - . lowering away gently. Vertically is ensured, if necessary, by the insertion of small wedges behind the segment. To detach, the. segment from the rope, the retaining cord is loosened, and as soon as the rope is slackened,-the cradle, comes Rib of mould Core Ground Fig. 6.—Cross Section through Mould. Wood fittings Rib of mould uu* □c \ Bolts ,0^=r' Fig. 7.—Suspension Ring. Concrete Concrete ■Faggots - ! OO r\°ooooO O 00 °o°td o%°0% ... \W/O OOoo 0 °C o3oA>0000 0 OO is begun.