2.1 Introduction

Slope failure occurs when the downward movements of material due to gravity and shear stresses exceeds the shear strength. Therefore, factors that tend to increase the shear stresses or decrease the shear strength increase the chances of failure of a slope. Different processes can lead to reduction in the shear strengths of rock mass. Increased pore pressure, cracking, swelling, decomposition of clayey rock fills, creep under sustained loads, leaching, strain softening, weathering and cyclic loading are common factors that decrease the shear strength of rock mass. In contrast to this the shear stress in rock mass may increase due to additional loads at the top of the slope and increase in water pressure in cracks at the top of the slope, increase in soil weight due to increased water content, excavation at the bottom of the slope and seismic effects. In addition to these reasons factor contributing in failure of slope are properties of rock mass, (slope geometry), state of stress, temperature and erosion. The factors affecting in slope failure have been shown in Table 2.1 and important factors have been described in this chapter.

 

Sr. No

Name of the parameters and properties

Details

1

Geological Discontinuities

Fault, Joint, bedding plane, etc

2

Water

Ground water, drainage pattern, rainfall, permeability, aquifer, etc

3

Strength

Shear strength, compressive strength, tensile strength, etc

4

Geotechnical parameters

Gran size, moisture content, atterberg limit, etc.

5

Method of construction

Shovel, dumper, BWE or combination, etc

6

Dynamic forces

Blasting and Seismic activity

7

Geometry of slope

Angle of slope, bench height, etc