In order to effectually remedy a disease it is necessary to ascertain its character. Many of the primary causes of slips in cuttings and embankments are, therefore, here enumerated; but, of course, they are not named in their order of importance, which cannot be established.
Heads of the Chief Causes of Slips and Subsidences in Cuttings.
1. The want of uniformity of the earth, particularly as regards percolation, cohesive power, and resistance to change by the action of water or meteorological influences.
2. The temporary or permanent exposure of the earth to the effects of the atmosphere, rain, frost, and snow.
3. The opening to the air and weather, &c., of thin seams of an unstable character, which, when unsupported, gradually crumble away and cease to support superimposed strata.
4. The tapping of springs.
5. The lower portion of a slope being impaired or undermined through an infiltration and flow of water.
6. The erosion of the slope.
7. The earth having intermediate unstable seams.
8. The unprotected surface of a cutting in light soil being loosened and blown away by a storm of wind, especially when it is accompanied by rain.