Modern Gasworks Practice

FOUNDATIONS, GAS WORKS BUILDINGS, ETC. 53 given applies to the larger houses of (say) more than 150 mouthpieces. For a medium-sized stage house take £70 to £100 per mouthpiece. THE DESIGN OF COAL STORES Although. the brick-panelled or plastered-steel structure admirably serves the purpose of afEording a covering to the retort bench, the whole question requires somewliat serious consideration wlien tlie storage of coal is concerned. Thin plaster, or 4-J-inch brickwork walls are in no sense capable of withstanding for long the lateral thrusts of a deep coal heap, and although. cases are known where such, buildings are being used for the purpose without visible detriment, there is little doubt that the factor of safety is extremely low, and considerable risks must be run. For all this, there is no reason why the light concrete house should not be employed for storage purposes, so long as those portions acting as retaining walls are effectively reinforced on the inner or tension side. A good plan is to employ old railway metals, these being rigidly interlaced witli piping or iron rods of about J-inch to 1-inch diameter. In the light panelled buildings the Steel framing must be doser and stronger, whilst a thin wall can be made of many of the patent reinforcements on the market. If large coal-stocks are to be regularly maintained under cover it cannot be disputed that the entire brick building, panelled and buttressed, provides the best form of shelter. Formerly these structures were erected almost without exceptioa, and the fact that l.hey are still doing chity as both coal stores and houses to-day speaks well for their design and durability ; and the same may be said of thick concrete or stone walls. If perfect reliance is to be feit, it is essential tliat the walls of coal stores should be designed on scientific lines, and the pressures due to the coal carefully computed. For this purpose the well-known Rankine formula for eartli pressures may be employed, and the wall will be sufficiently stable if the middle-third condition is neglected, and the resultant pressure cuts the various sections within the width of the base at any one section. In working out the pressure the weiglit of ordinary bituminous coal may be taken as 54- 1b. per cubic foot, and tlie angle of repose as 45°. Then the formula is :— p __ WA2/1 — Sin 2 \1 + Sin 9?/ Where P = total pressure per foot run at a depth of h feet. W = weigh.t of coal per cubic foot = 54 1b. < p = tlie angle of repose of coal = 45°. For instance, suppose it is required to find the thickness of walls necessary for stacking coal to a deptli of 15 feet. Then—- • p 54 x 225/1 - Sin 45\ /„. ,.o 1\ 2 \1 + Sin 45/ \ yV From this, P is found to be 1,042 1b. at a depth. of 15 feet, or an average pressure of 69 1b. per square foot. This gives the total horizontal pressure at the bottom