Bio Engineering
Frequent losses of life and property are observed in
Nepal due to natural and artificially caused landslides. Natural ones take
place due to loose geographical structure, steep slopes and heavy rainfall etc.
while due to ignorance of people, population density, deforestation etc.
artificial landslides take place from time to time. Civil engineering alone has
not been able to get rid of this problem. On this light, bio-engineering has
been introduced as an effective, economical & sustainable solution -
About Bio- Engineering:
Bio- Engineering is that branch which deals with the use
of vegetations alone or in combination with small scale civil engineering
structures or non-living plant materials for the purpose of reducing the
shallow seated instability and then on tolling erosion of slopes thereby
reducing the chances of landslides from occurring and/or causing heavy damages.
Civil engineering structures are
heavy, costly and need skilled technical manpower due to which sustainable
solutions can't be achieved.
Also, civil structures have their load taking capacity
regarding with time due to various reasons. As such, if vegetations are used
jointly with civil structures, they share load imposed on the structures as time
passes, thereby increasing
efficiency of the system
overall
efficiency of the overall system.
Advantages of Bio -
Engineering
1) Protects almost all slopes against erosion,
2) Reduces the instance of slow seated instability,
3) Locally available vegetations
4) Cost-effective & sustainable method,
5) Versatility in application i.e. high technology and skilled manpower not required,
6) Improves surface drainage I reduces slumping ?
7 Easy to prepare and maintain,
8) Physical flexibility,
9) Some vegetations yield fruits /products, enhance economy
10.) The only solution for some problems.
11) Environmentally and socially advantageous,
12) Diversity in vegetations is obtained,
13) Stability of landslides and slope can be checked from even the lower level of
remote areas
14) Assist civil structures by sharing load on passage of time when their residual
strength decreases.
Functions of Bio-Engineering
System:
Bio-engineering alone or along with some small scale
civil engineering structures are used for fulfilling of following engineering
functions.
1) Engineering functions:
–
Catch process of holding thin layer of soil part hereby
restricting their movement. Bio-Eng. plants: Multi stemmed shrubs and bamboos, Civil Structures. Catch
walls, catch wattle fences, netting,
–
Armor: Providing protective cover to protect soil surface
particles from
movement. Bio-engs: - grass carpets Civil Structures: Pitching, revetment, breast walls,
–
Reinforce: Mechanism of providing strength to bind the soil particles by densely rooted
trees and grass. Bio-engineering: Dense rooted shrubs, grass and trees Civil Structures: Reinforced
earth soil, nailing
–
Anchor: firmly fixing of the soil particles and debris by the action anchoring action a
deep long and throng roots. Bio-Engineering: Deep long and strong roots, civil structures: Rock Anchor
– Support: Support to soil mass debris
from flowing by mechanical action of root system Bio- Eng, Shrubs, large trees Civil Str: Prop wall, toe
wall
– Drain: Process & draining at the
water quickly to remove
excess load of water and soil system Bio-Engs: Diagonal plantation I drain cable drain
sub-surface
2.) Hydrological functions:
The multiple stems and think of bio- engineering plants
trap soils particles and debris from morning down the hill slope. The root
systems bind and hold scale particles, rock and debris reducing the rate of erosion and
hand slides. Vegetations play a major role in manipulating the hydrological
regime by changing the quantities of water circulating from land and water
bodies to atmosphere. The help in slope stability reducing the changes a
erosion I landslides by:
-
Interception of rain drops, protecting ground surface from the direct impact of raindrops,
-
Leaf drip and stem flow reduces velocity,
-
Evaporation of water from leaf & stem surface,
-
Storage of water in canopy and stems,
-
Transpiration through leaves,
-
Vegetations decrease surface runoff and overland flow by
increasing infiltration, soil water storage and sub-surface flow.
3.) Ecological functions:
-
transforming harsh environment of degraded slope into a better
ecological condition which in turn generates better micro-environment of the
establishment and growth a plants, micro-organisms and small animals.
-
Helps increase the biodiversity of the site.
Limitations of Bio-Engineering
1) Preferably used for shallow seated failures, mostly favorable for depths 1-1.5m depths. Shouldn't be used for deep seated failures i.e. failure depths more than 3m.
2) Not able to fully function at its initial stage,
3) Checking of waterways with plant growth might cause damage to other structures,
4) Vegetation growth on structures cause adverse effect on the performance of structural material,
5) Needs after care, regular repair & maintenance.
Bio engineering
limitation of bio engineering
vegetation
living plants
civil engineering
land slide
shallow landslide
erosion
ecological function
social benefits
shallow sheated failure
sleep zonegully erosion
anchor
support
drain
reinforces earth soil
nailing of soil
root zone
rock anchor
hydrological function
armour
catch
reinforce
