Landslides are one among the important natural calamities, which commonly occur on slopes which causes serious damages to the property, livelihood, communication passages and lives.  Landslides are very complex phenomena involving multiple factors both natural and manmade. High intensity rainfall, steep slopes, soil thickness are the natural causes and urban development and deforestation are manmade causes. It also occurs in natural slopes influenced by various environmental parameters namely, rainfall and earthquakes. The factors like geological and geotechnical properties, duration and intensity of precipitation, aspect, slope inclination, vegetation and slope morphology will determine the type, dimensions, and process of slope movements. Steep terrain and high intensity rainfall make frequent occurrence of landslides in hilly terrains.

An assessment of landslide hazards is, therefore, a prerequisite for sustainable development of the hilly region. In cold regions, frequent incidents of soil slope failures occur due to snowmelt and rainfall. These failures are triggered by an increase in the degree of saturation of soil due to infiltration of water derived from rainfall and snowmelt. Hill slopes in mountainous areas are suffering from

human activities like building road network, urban development, deforestation, and rapid land use modification, leading to occurrence of landslides. An understanding of the conditions and processes which controlled past landslide event and their evidences is the most important factor in the prediction of future landslides.

The stability of slope is measured by its factor of safety using geometric and shear strength parameters. The stability of slopes depends on the soil shear strength parameters such as cohesion, angle of internal friction, unit weight of soil and slope geometry. Slope stability is analyzed by the limit equilibrium methods, boundary element methods, finite element methods, neural network methods, reliability methods, distinct element method and hybrid continuum- discontinuous methods. Limit equilibrium methods of slices are the most commonly used methods among others since simplicity and ease of use are the main advantages.

Predicting approximate earthquake-induced landslide displacements is helpful for assessing earthquake hazards and designing the slopes to withstand future earthquake shaking.

Pseudostatic analysis is useful for identifying yield accelerations and hence peak ground accelerations (PGA) below which no slope displacement will occur. In cases where the PGA does exceed the yield acceleration, pseudo-static analysis has proved to be vastly over conservative because many slopes experience transient earthquake accelerations well above their yield accelerations but experience little or no permanent displacement. Generally, shallower failures are associated with the development of positive pore pressures, while deeper failures are associated with loss in suction. However, it should be noted that the failure depth is governed not only by the strength characteristics, but also by the hydraulic characteristics of the soil and both should be investigated for detailed analysis. In the light of these problems, you have been asked to undertake Geotechnical Investigation and Analysis of Landslide Vulnerability in Accra

RESPONSIBILITY:

    Phase 1:

1. Discuss spatial slope stability.

2. Examine the landslide characteristics and spatial distribution.

3. Examine earthquake intensity.

4. Landslide susceptibility mapping.

5. Investigate community knowledge on pre-disposing factors to landslides.

Phase 2:

 

6. The extent and effects of mass wasting.

7. Hazard Analysis and Protection Measures.

8. Identify government and community preparedness to landslide disaster events.

9. Assess responses of government and communities to landslides risk and vulnerability reduction.

10. Assess the establishment level of collaboration between local government and community in landslide risk reduction.

 

 

 

 

 

 

 

 

                                                                                              

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