1. RISK ANALYSIS AND REMEDIAL WORKS AT KAAIMANS PASS
Monyake Mohlabane

3. According to the climatic data for the George area for the 30-year period from 1961 to 1990:
the average rainfall for the month of August is 68mm
the highest 24 hour rainfall measured for the month of August is 116mm
the highest 24 hour rainfall measured for any month is 132mm, and
the recorded rainfall for Knysna during August 2006 was 377mm.
From the above it is evident that the rainfall of August 2006 in the George to Knysna area was abnormal compared to the statistics of the past 30 years.

6. METHODOLOGY OF INVESTIGATION
Visual Inspection of Failures (walkover survey)
Visual Inspection of Structures (distress)
Aerial Inspection (full extend of failures)
Route Mapping (geology & mapping)
Aerial Photography (stereo-pairs & contours)
High Resolution Aeromagnetic Survey (faults)
Rotary Core Borehole Drilling (remedial works)
Exploratory Trenches (failure surface)
Installation of Inclinometers (monitoring)

10. Several modes of failure were evident along the National Road N2/7, including:
translational failures (i.e. sloughs) in relatively shallow soil overburden,
slip circle failures in moderately thick soil layers,
plane failures in rock slopes,
wedge failures in rock slopes,
undercutting (erosion) of embankments and talus slopes,
hillcreep on steep slopes, and in addition,
significant erosion gulleys occurred along some of the preferential drainage paths

11. A probability of failure analyses was carried out at each of the analytical sections along the route. The probability of failure type analysis was chosen because it can evaluate the sensitivity of more than one design parameter and its overall contribution to slope stability.

15. The most significant types of failure encountered along the route were:
Translational slides in relatively shallow soils
Wedge failures in rock masses
Planar failures in rock masses.

17. Major Planar Failure (Ch35+180)

18. Failure surfaces with Sub-vertical Release Joints (Ch35+180)

19. Meshing and Pinning of Colluvium at Crest of Slope (Ch35+180)

20. Rockbolting of Rock Slabs (Ch35+180)

21. Slope Cleared of all Failure Debris (Ch35+180)

22. Granite Corestones / Soil Matrix on Foliation Plane (Ch35+950)

23. High Pressure Water Jetting of Talus Face (Ch35+950)

24. Scaffold Structure utilised to Access Talus Face (Ch35+950)

26. THANK YOU