L ANDSLIDE R IO D E J ANEIRO (F EBRUARY 1996)

Geological features Gneissic Rock Pre-Cambrian bedrocks Unloading and Tectonic fractures R IO D E J ANEIRO – L ANDSLIDE – F EBRUARY Natural Hazard Western portion of Tijuca Massif 131 dead bodies 222 house loss 144,900 km 2 affected

L ANDSLIDE F ACTORS 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

L ANDSLIDE F ACTORS Unloading Fractures Slope Deposit Hydraulic Conductivity Slope Stability Destabilizing existing Landslide Engineering Project Excavation Inappropriate Control Measure Geological Condition

L ANDSLIDE E FFECTS 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 methods structured wells, supported by reinforced earth column ground nailing Landslide Mitigation

T HE SOLUTION ADOPTED – R ETAINING WALLS 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

T HE SOLUTION ADOPTED – R ETAINING WALLS 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

T HE SOLUTION ADOPTED – R ETAINING WALLS 3. Tires wall – 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

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