Speculations on methods of stabilizing slopes

Economic pressures dictate that most artificial slopes are formed as steeply as possible, and natural slopes revert to the maximum angle consistent with stability. Structural methods of slope stabilization are well established and their limitations known. This paper speculates on some of the more esoteric methods recently, or yet to be, applied. Shallow and deep instability mechanisms in embankments and cuttings are outlined, noting the influence of ground water and rainfall. Some aspects of relatively new methods of stabilization are described, for which longterm experience is lacking. This paper also speculates on longevity of soil nails and on methods of their protection from corrosion; and it gives data on two case histories monitored for 4 and 6 years. Test results are given on pullout resistance of quicklime nails and dowels in clay, comparing with those for cement-grouted reinforcements on the same site. A technique that was used to stabilize an active railway embankment is described which used horizontal mixed-in-place 600 mm diameter grouted inserts. The mechanism of stabilization of clay embankments by cement grout injection is proposed, and a scheme for controlling annual cycles of shrinkage and swelling in clay embankments by electro-osmotic processes is suggested.