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.