Kinematic stability analysis of multi-faced rock slopes in the Himalayas

摘要

For the assessment of natural stability of rock slopes, Kinematic analysis technique is extensively used. This technique makes use of dominant discontinuity planes within slope mass to forecast the probability of sliding, wedging and falling. This probability is given in the context of the attitude of slope face which is generally supposed to be of a planar geometry. Such kind of analysis is named as single faced slope (SFS) analysis. Although in nature the probability of finding such simple cases is often less compared to slopes in which the strike direction changes, as in the case of cut slopes; and the slope surface turns to be non-planar. When rock slope surface is either concave or convex shaped, its changing strike also plays an important role in the kinematic analysis (which is generally not used). These slopes will have two or more planar surfaces and are termed as multi-faced slopes (MFS). During the investigation conducted along national highway (NH-21) between District Manali (32o14'21"N-77o11'43"E) and Village Dundi (32o21'25"N-77o07'55"E), in the Himalayas; the majority of slopes encountered are MFS. This paper describes the details of kinematic analysis performed on these MFS and gives the stability index for these slopes with the change in strike direction. Three cases are used for the further analysis. Case 1 (Planar sliding), when the failure is based on only one joint set and is planar in nature. Case 2 (Double plane sliding/Wedging), when wedge block is formed and sliding is along both planes, formed by either, the intersection of dominant joint sets or by two slope surfaces. Case 3 (Toppling), when the block topples, either showing flexural toppling or direct toppling. Results of the cases study are presented in this paper.