L ANDSLIDE R IO D E J ANEIRO (F EBRUARY 1996). Geological features Gneissic Rock Pre-Cambrian...
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Transcript of L ANDSLIDE R IO D E J ANEIRO (F EBRUARY 1996). Geological features Gneissic Rock Pre-Cambrian...
Geological features
Gneissic Rock
Pre-Cambrian bedrocks
Unloading and Tectonic fractures
RIO DE JANEIRO – LANDSLIDE – FEBRUARY 1996
1996 Natural Hazard
Western portion of Tijuca Massif
131 dead bodies
222 house loss
144,900 km2 affected
LANDSLIDE FACTORS Heavy Rainfall
Heavy Storm (intense summer rainstorm) & cloudbursts
Often 1000 mm/month (January)
In 1996 rainfall was 380mm in 24 hours
Effects Soil saturation, Soil strength
& stability reduction Landslide & Debris-Flow
LANDSLIDE FACTORS
Unloading Fractures Slope Deposit Hydraulic Conductivity Slope Stability
Destabilizing existing Landslide
Engineering Project Excavation Inappropriate Control Measure
Geological Condition
LANDSLIDE EFFECTS Catastrophic debris-flows
Extensive rock-debris Structurally hanging plateaus
Flood
Worst Rainstorm Landslide
Water disease
Large No. Dead bodies Outbreak of Leptospirosis
Re-profiling
Lowering the slope
Positioning infill at the foot of the slope
1. Geometric methods
Also to prevent surface erosion:
Geomats, Geogrids and BrushwoodMats are used
They control erosion due to: • Containment and reinforcement of the slope surface• A barrier against drag from material carried by surface water
Slope stabilisation methods can be put into three categories:
Landslide Mitigation
Lowering of the water level inside the ground, reducing the pore pressure hence increasing the shear strength of the soil
Drainage systems can be adopted to reduce the ground stresses
2. Hydro-geological methods
shallow drains (5-6m slipping) deep drains (deeper surface slipping)
Landslide Mitigation
Mechanical methods are constructed to contrast the destabilising forces in the ground
These include:• Retaining walls• Anchors• Rock or ground nailing• Jet-grouting • Structured wells• Piles or reinforced ground• Steel nets or wire meshes
3. Mechanical methodsstructured
wells, supported by
reinforced earth
column
ground nailing
Landslide Mitigation
THE SOLUTION ADOPTED – RETAINING WALLS
1. Conventional anchored concrete wall 1. Conventional anchored concrete wall
Prevent downslope movement
- Lateral earth pressure
- Hydrostatic pressure
- Reactive force
Anchors: driven into the material and expanded at the end of the cable to form a bulb in the soil
Useful for high loads to retain but cannot sustain large unstable slopes
Not usually economic to build massive retaining walls at the toe of major natural landslides
THE SOLUTION ADOPTED – RETAINING WALLS
2. Recycled tires wall 2. Recycled tires wall
Tire: very high tensile strength and suitable mechanical properties
Tires Wall: More effective at stopping landslides than a concrete retaining wall
Allows higher horizontal displacements than an anchored concrete retaining wall
Economically viable
Environmentally sustainable
Low cost structure Help to raise the living standards in the favelas of Rio de Janeiro
THE SOLUTION ADOPTED – RETAINING WALLS
3. Tires wall 3. Tires wall –– Construction Methods Construction Methods
a. Slice off one sidewall in each tire
b. Cleaned and levelled the base surface
c. Placed the tires and tied them together in a honeycomb pattern
d. Packed them full of compacted earth
e. Installed of gullies and drainage
Caution: Maximum height of the wall and Evolution of the wall
Easy &short construction work, Light equipment