Preliminary evaluation of the stability of al-Haddah rock slopes

Abstract EN

The stability of natural and man-made rock slopes of the Al-Haddah area was studied.

Two methods of stability analysis were used.

These were, the stereographic projection approach and the morphometric rating approach.

The former approach was used to define the kind of possible failure and the magnitude of safety factor on each slope, while the latter method was applied to define the areas of stable and unstable ground by superimposing the slpoe angle, relative relief, favourability of joints to cause failure, strength and drainage de- nsity maps.

The area is mainly composed of dioritic, granodioritic and granitic rocks of Precambrian age.

These rocks are cross-cut by a number of dykes which range from acidic to basic in com- position.

There are four major sets of joints which, in addition to a few strike slips faults, con- stitute the planes of weakness which give rise to a variety of possible modes of failure.

After carrying out the necessary stability analyses, it was found that large parts of the area, particularly those at higher elevations, are unstable.

The maximum safe slope angle for dry slopes was found to be between 57° and 74°.

This study further shows that there is a great similarity between the results of the stereog- raphic and morphometric rating approaches of stability analyses.

The morphometric approach can only be used for making preliminary evaluation of the stability in an area,,while the stereographic approach is effective in the solution of actual problems such as the design of cuts.