A treatise on highway construction . de of stone laid dry, whenstone can be procured in tlocks of sufficient size to render thiskind of construction of sufficient stability to resist the pressure ofthe earth. But when the blocks of stone do not offer this security,they must be laid in mortar. The wall which forms the slope ofthe excavation should be carried up as high as the natural surfaceof the ground. Unless the material is such that the slope may besafely formed into steps or benches as shown in Figs. 61 and 63, the-wall that sustains the embankment should be built up to the surfaceof the
A treatise on highway construction . de of stone laid dry, whenstone can be procured in tlocks of sufficient size to render thiskind of construction of sufficient stability to resist the pressure ofthe earth. But when the blocks of stone do not offer this security,they must be laid in mortar. The wall which forms the slope ofthe excavation should be carried up as high as the natural surfaceof the ground. Unless the material is such that the slope may besafely formed into steps or benches as shown in Figs. 61 and 63, the-wall that sustains the embankment should be built up to the surfaceof the roadway, and a parapet wall or fence raised upon it, to pro-tect pedestrians against accident. (See Figs. 56 and 63.) 660. Roadways on Rock-slopes.—On rock-slopes when theinclination of the natural surface is not greater than one perpen-dicular to two base, the road may be constructed partly in excava-tion and partly in embankment in the usual manner or, as shownin Figs. 63, 64, 65, by cutting the face of the slope into horizontal. Rg. 63. SHOWING METHOD OF CONSTRUCTION ON HILLSIDES. steps with vertical faces, and building up the embankment in theform of a solid stone wall in horizontal courses,either dry or laidin mortar. Care is required in proportioning the steps, as all attempts EAKTH-WOEK, 509 to lessen the quantity of excavation by increasing the number anddiminishing the width of the steps require additional precautionsagainst settlement in the build-up portion of the roadway.
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