29. By unequal pressure upon the foundations of a retaining wall at the foot of a slope caused by lateral over-pressure tilting it, or by its unequal settlement.
30. In sidelong ground, by the removal of support against the action of sliding, which, without artificial aid, may not be arrested until the slope of a cutting on the higher side approaches the steepest inclination of the face of the hill.
31. By blasting laminated rock dipping at a considerable angle towards a cutting in the side of a hill; the result sometimes being that a cavity is made depriving the upper beds of support and causing them to overhang, and a mass extending to the top surface of the hill to slip along the unsupported stratum.
The first ten “heads of the chief causes of slips in cuttings” might be classed as NATURAL, i.e. produced or effected by nature and, therefore, beyond the power of man to entirely prevent; the remaining heads as ARTIFICIAL, and therefore, in some degree to be prevented, unless obviously the result of the unavoidable exigencies of construction.
Heads of the Chief Causes of Slips and Subsidences in Embankments.
1. The percolation of surface water into the toe and under an embankment upon the original surface of the ground, and also downwards through the formation.
2. Unequal percolation of water through the formation or the slopes.
3. The surface of the ground upon which an embankment is tipped inclining in one direction, or falling on each side from the centre.
4. The effects of rain, frost, snow, and the atmosphere on the deposited earth.
5. By a crumbling of the lower portion of a slope.