Van Nostrand's engineering magazine . ace MNO, which has been leftopen until now, is filled with thin, hard,flat stone, loosely hand laid on their flatsurfaces. In this way the lateral press- STONE ARCHES UNDER EMBANKMENTS. 211 ure is kept from the arch as far as pos-sible, since the walls have moved as faras they are likely to, and the flat stone,while they will transmit any amount ofvertical pressure, will move on themselvesbefore transmitting very much lateralpressure. If this is deemed insufficientthe space MNO could be built solid withstone laid in mortar, and an opening afew inches wide
Van Nostrand's engineering magazine . ace MNO, which has been leftopen until now, is filled with thin, hard,flat stone, loosely hand laid on their flatsurfaces. In this way the lateral press- STONE ARCHES UNDER EMBANKMENTS. 211 ure is kept from the arch as far as pos-sible, since the walls have moved as faras they are likely to, and the flat stone,while they will transmit any amount ofvertical pressure, will move on themselvesbefore transmitting very much lateralpressure. If this is deemed insufficientthe space MNO could be built solid withstone laid in mortar, and an opening afew inches wide left on the line NO andcovered with large stone laid over the arch ring, the true line would lie betweenA and C, depending on the depth of thecrown below the surface of the embank-ment. This, it is scarcely safe to expect, inview of the elasticity of the materialscomposing the walls and of the tendencyof the material between the walls andthe ring to become somewhat compactunder the vertical pressure and so trans-mit lateral top to keep the earth from filling it this arrangement of the load,the arch is drawn almost if not whollyfor vertical pressures, depending on theengineers confidence in his arrangementfor securing such pressures. In the cut are given the various formsof the pressure lines for extreme cases inan arch of the general form of the oneshown. For a very high embankment, suppos-ing the pressure to be equally distributed,and all pressures vertical, we have theline A. Supposing the pressure equallydistributed, but allowing pressure, inaddition to the vertical, at one half theusual angle of repose (56-2° with thevertical) as in the calculations for retain-ing walls, we have the line B. Takingall vertical pressures but proportioned inamount to the amount of material belowthe line PQ, we have the line C. Allow-ing for pressures at the same angle asbefore, but proportioned to the amountof material below the line PQ, we havethe line D. It will be o
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectenginee, bookyear1879
