Article Published on January 18th 2009 

The
slopes which are susceptible to failure by various modes like, plane,
wedge or circular mode of failures can be stabilized by various methods.
These methods could be as simple as altering the geometry of the slope or
comparatively complicated and difficult like providing reinforcement and
retaining structures. The important factors which influence the stability
of the slope are; i) slope angle ii) dip of the failure plane or plunge
of the line of intersection of two wedge forming planes iii) shear strength
parameters, cohesion and angle of internal friction and finally the water
saturation condition.
For the stability condition either of the abovementioned factors may have comparatively high or low influence. Some of the factors may be responsible in inducing the forces for sliding where as, the others may contributes in providing the resistance to the sliding. The net result of these factors will defines whether the slope is going to slide, under the given conditions, or it will be stable. The relationship of the factors responsible for inducing sliding and the factors responsible to provide resistance to the sliding is defined by the limit equilibrium. Factor of safety can be defined as the ratio of the total forces available to resist sliding to the total forces available to induce sliding. If the factor of safety is less than unity, it implies that the resistive forces are less than that of the forces which induce sliding. Thus, for the condition when the FOS is less than 1.0 the slope may fail, provided it is subjected to a triggering factor, natural or man made. The factor of safety of a potential unstable slope may be improved by providing several methods such as, safe slope design by altering the geometry of the slope, reinforcement by providing rock bolts, retaining structures, shotcreating etc. Remedial Measures for Slope Slope Design A considerable stability can be achieved by making concave slope face. The safe slope angles for a given slope can be obtained by adopting technique proposed by Hoek and Bray, 1989. In this technique, the factor of safety is obtained by assuming different slope angles and slope heights. The factor of safety, as calculated for each combination of slope angle and slope height, is marked over a graph sheet by taking slope angles on Xaxis and height on Yaxis. Later, a contour curve corresponding to a factor of safety equal to 1.2 is drawn. Thus, the safe slope angles for different slope heights are obtained from this graph. Based on these safe slope angles a slope cross section is prepared in which height of the slope is considered from top to bottom. Rock Bolting Rock bolts are used to reinforce jointed rock much as reinforcing bars supply tensile resistance in reinforced concrete. In rock slope, tunneling and underground mining, steel rod inserted in a hole drilled in the face of a rock formation to support the sides or roof of the excavation.These are equally effective in natural and cut slopes, as these rock bolts act as a binding tools between the two rock blocks on the either sides of the discontinuity plane. The bolt may be provided with an expanding device to grip the rock at the far end of the hole or may be bonded to the rock by means of expanding cement. Rock bolts may be used singly or in rows.There are static and tensioned rock bolts. Tensioned rock bolts should be used only where a force is needed to counteract the forces making the structure unstable. 

