LANDSLIDE RIO DE JANEIRO

(FEBRUARY 1996)

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

Thanks for your Attention!!!

Any Question?