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Bio Engineering for Slope Stabilization

What is Bio-engineering?

 Bio-engineering technique is the use of living vegetation or vegetation parts, either alone or in conjunction with civil engineering structures and non living plant materials, to reduce shallow- seated instability and erosion on slopes.



Soil bio-engineering can be divided into threes categories: 

  • Vegetative plantings

  • True Bio-engineering

  • Bio Technical Techniques (engineering) 

Vegetative plantings 

Vegetative plantings are conventional plantings of grasses & shrubs in order to prevent surface erosion.

  • The living material is not used with structural meaning.
  • The erosion prevention function is carry out only once the vegetation is established.

 

True Bio-engineering 

 Plants or part of plants (seeds, seedlings, cuttings, branches etc.) etc itself provide both the vegetative and structural components of the design.

  • Brush layers, wattling, Bamboo fencing etc.
  • Cutting or branch parts as initial and primary soil reinforcing and stabilizing material
  • During the growing season develop roots and sprouts foliage. It becomes a major structural component which grows stronger with time

True Bio-engineering Examples

  • Brush Layering
  • Bamboo Fencing

Bio-technical Engineering 

  • Living materials (plants) are combined or integrated with non living or structural materials
  • Vegetative and structural components work together in mutually reinforcing and complimentary roles.
  • Live crib walls, vegetated gabions, vegetated stone pitching etc.
  • Structural elements provide immediate resistance to sliding, erosion, and wash out
  • As vegetation becomes established, roots invade and penetrate the slope, binding it together

 

 Engineering Function of Vegetation

  • Catch
  • Reinforcing
  • Anchoring
  • Armoring
  • Supporting
  • Drainage

 

Application of Bio Engineering

  • Prevention of scour
  • Protection of bare soil
  • Stabilization of gullies, prevention of risk of gullying;
  • All slopes where there is a risk of shallow slumps
  • Any slope that remains bare; • any area that has failed and needs to be restored
  • Rehabilitation of quarry sites and borrow pits

 

Scope / Field of Bio Engineering

  • Mining and reclamation
  • Highways and railways
  • Construction sites
  • Waste disposal and public health
  • Airfields and helipads
  • Waterways
  • Land drainages
  • Reservoirs and dams
  • Coastal and shoreline protection
  • Buildings and recreation
  • Pipelines and site appraisal

 

Advantages of Bio Engineering

  • Protect all slopes against erosion
  • Low-cost and lower long-term maintenance cost
  • Environmental benefits to wildlife habitat, water quality, and aesthetics
  • Improved strength over time
  • Improve surface drainage and reduce slumping
  • Reduces shallow plane failure
  • Compatible with environmentally sensitive sites
  • Socially and economically advantageous to local communities
  • Cost effective

 

Limitations of Bio Engineering

  • Depth of root zone limits the performance of vegetation or bio engineering
  • Not able to function in its initial stage
  • Root penetration into foundations and drains
  • Choking of waterways with plant growth
  • Vegetation growth on structure cause adverse effect on the performance of structural material
  • Needs aftercare, regular repair and maintenance. 


Justification

  • Less cost and less impact on slope
  • Provide economic savings and minimize potential impacts to the slope and adjoining resources.
  • Use of native plant materials and seed are well adapted to local climate and soil conditions.
  • Useful on sensitive or steep sites where easy accessibility is not feasible.
  • Grow stronger with time as vegetation becomes established.
  • Even if plants die, organic litter helps growth of other plants.

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