Independant study on Reinforced soil retaining wall
1. DEPARTMENT OF CIVIL ENGINEERING
Dr B R AMBEDKAR NATIONAL INSTITUTE OF TECHNOLOGY
JALANDHAR – 144011
Reinforced Soil Retaining Walls
Independent Study Work
Supervisor-
Dr A K Agnihotri
Dr Akash Priyadarshee
Submitted by-
Gurjeet Kumar
14217009
2. Retaining wall
Retaining walls are used to retain earth or
other materials which have the tendency to
slide and repose at a particular inclination.
They provide lateral support to the earthfill,
embankments or other materials in order to
hold them in a vertical position.
Retaining walls also have application in
buildings and bridges such as basement,
foundation wall, bridge abutment etc.
3. Reinforced soil
Reinforced earth is a combination of earth and linear reinforcing strips
that are capable of bearing large tensile stresses.
The reinforcement provided by these strips enable the mass to resist
the tension in a way which the earth alone could not. The source of this
resistance to tension is the internal friction of soil, because the stresses
that are created within the mass are transferred from soil to the
reinforcement strips by friction.
4. Idea of Reinforced Soil
IT ALL BEGAN LIKE A GAME, when Henri Vidal, a highway engineer
and architect, was trying to built a sandcastle on the beach. But the sand
kept on falling off and this led to the idea of reinforcing the construction
with pine needles. That is how the general principle of Reinforced Earth
came about.
7. Load Transfer Mechanism
The flexible reinforcement interacts frictionally with the soil resisting
the shear stresses in the soil mass
The shear stress at the interface of the soil and the reinforcement
generates strains in the reinforcement and a tensile force is mobilised
in the reinforcement
If this tensile force exceeds the tensile capacity of the reinforcement,
rupture failure occurs – Tensile failure
If deformations are high or if the interface is smooth, it is likely that a
slip occurs between the soil and reinforcement – Pullout Failure
For stability, Tensile failure and Pullout failure to be examined
8. Principles
If a vertical stress (v) is applied on a soil element, it undergoes a
vertical compression (v) associated with a lateral deformation (h).
If a reinforcement is added to the soil in the form of horizontal layers,
the soil element will be restrained against lateral deformation as it
acted by a lateral force.
12. Soil
It should be granular, cohesion less material, not too much silt or clay
having particle size not more than 125 mm.
Not more than 10 percent of the particles shall pass 75 micron sieve &
the earth reinforcement coefficient of friction to be either higher than
or equal to 0.4 & Plasticity Index < 6.
The soil must have a moisture content suitable for compaction.
13. Skin
Skin is the facing element of the reinforced soil wall.
These elements support the backfill and keeps the reinforcement at a
desired elevation in the reinforced soil wall and also protect the
granular at the edge falling off.
Made of either metal units or precast concrete panels.
14. Reinforcement
A variety of materials can be used as reinforcing materials such as-
Steel
Concrete
Glass fibre
Wood
Rubber
Aluminium
Geosynthetics
22. Seismic Stability
High performance during the 1995 Kobe Earthquake of a GRS RW of
this type that had been constructed at Tanata validated its high seismic
stability
29. Benefits of using RS-RW
Lateral thrust on the wall is almost eliminated due to the development
of soil-reinforcement interface friction.
Thin wall element known as skin is found adequate to retain the
backfill resulting in considerable economic savings.
Simple construction.
Faster construction than traditional concrete walls.
Can be built in confined areas or areas where a concrete wall is almost
impossible to be constructed.
High seismic load resistance.
Various shapes and forms can be made.
30. Literature Review
Year Author Summary of work
1992 Swami Saran et al. Unattached reinforcing strips, embedded in the
cohesionless backfill behind a rigid retaining wall,
are effective in reducing the lateral earth
pressure(upto 50%) on the wall.
1998 K.G. Garg Retaining wall with geogrid reinforced earthfill
was constructed only at 79 per cent of the cost of
the retaining wall with conventional earthfill.
2000 Robert M. Koerner 35,000 RS-RW exists and they cover the entire
range of practical wall heights and it is seen that
geosynthetic reinforced walls are the least
expensive of all wall categories and at all wall
heights.
31. Year Author Summary of work
2004 Satyendra Mittal et
al.
Unattached reinforcing strips, embedded in the
cohesionless backfill behind a rigid retaining wall are
effective in reducing the lateral earth pressure on wall. The
extent of reduction in the resultant pressure will depend on
the amount of reinforcement present in the backfill. The
optimum length of reinforcing strips is found to be around
0.6–0.8 times the height of wall for most practical cases.
2005 Hoe I. Ling et al. Earthquake performance of RS-RW improved by
increasing the length of top reinforcement layer, reducing
vertical reinforcement spacing and grouting the top block
to ensure firm connection to the reinforcement.
2006 Iqraz Nabi Khan and
Swami Saran.
Presented an experimental study on a model reinforced
earth wall with sand backfill with aluminium reinforcing
stirps and found that Rankine’s theory of earth pressure
was close to the observed values.
32. Year Author Summary of work
2007 G. Madhavi Latha
and A. Murali
Krishna
Damage to RS-RW will be more in case of stronger seismic
events if the backfill is not properly compacted.
2007 Iqraz Nabi Khan
and Swami Saran.
Presented a model study, different lengths of bamboo strips and
geogrids were used for strengthening the backfill. Results
indicated decrease in moments up to about 65 percent due to
reinforcing the backfill.
2012 H. Ahmadi and M.
Hajialilue-Bonab.
Presented a study focuses on the experimental and analytical
investigations of small-scale physical model tests. Experimental
results shows that the bearing capacity of footings located on the
backfill can be increased significantly by including geotextile
layers on the top of the backfill.
2013 Christopher Y.
Tuan.
Presented Full-scale explosive test data from 4.6-m-high and 24-
m-wide reinforced soil walls and found that the use of RS-RW
wall systems for protective structures has received attention for
their energy absorbing capability and blast resistance
33. Gaps in Study
Several additional studies should be carried out to further the knowledge
and use on reinforced soil retaining walls and these are mentioned below:
1. Settlement of the backfill while performing different analysis or
behaviour of surface of backfill under different conditions.
2. Replacing backfill with some waste material like pond ash and fly
ash and introduce reinforcements in the same backfill.
3. Wrap face backfill with geotextile behind a rigid wall need to be
studied.
4. Inclusion of geocell and tire chips in the backfill.
5. Reinforcing the backfill with two or more reinforcements.
34. Conclusion
Reinforced soil retaining walls have evolved as viable technique and
contributed to infrastructure in terms of speed, ease of construction,
economy, aesthetics etc.
It is a technology that needs to be understood well in terms of its
response, construction features etc. Failures of RE walls have also been
noted in a few places due to lack of understanding of behaviour of
reinforced soil walls.
FHWA, NCMA guidelines need to be studied in detail for seismic
stability and deformation issues.
35. References
1. Swami Saran, K. G. Garg and R. K. Bhandari. “Retaining Wall with Reinforced
Cohesionless Backfill”. Journal of Geotechnical Engineering, Vol. 118, No. 12, December,
1992.
2. Hoe I. Ling, Yoshiyuki Mohri, Dov Leshchinsky, Christopher Burke, Kenichi Matsushima
and Huabei Liu. “Large-Scale Shaking Table Tests on Modular-Block Reinforced Soil
Retaining Walls”. Journal of Geotechnical and Geoenvironmental Engineering, Vol. 131,
No. 4, April 1, 2005.
3. Christopher Y. Tuan. “Ground Shock Resistance of Mechanically Stabilized Earth Walls”.
International Journal of Geomechanics, Vol.14, 2014.
4. Robert M. Koernera and Te-Yang Soong. “Geosynthetic reinforced segmental retaining
walls”. Geotextiles and Geomembranes 19 (2001) 359–386.
5. G. Madhavi Latha and A. Murali Krishna. “Seismic response of reinforced soil retaining
wall models:Influence of backfill relative density”. Geotextiles and Geomembranes 26
(2008) 335–349.
36. Contd.
6. Iqraz Nabi Khan and Swami Saran. “A Model Study on Retaining Wall with Reinforced
Backfill”. Journal - The Institution of Engineers, Malaysia (Vol. 68, No. 2, June 2007).
7. Iqraz Nabi Khan and Swami Saran. “A Model Study on Metallic Strip-Reinforced Earth
Wall”. Malaysian Journal of Civil Engineering 18(1) : 38-45 (2006).
8. H. Ahmadi and M. Hajialilue-Bonab. “Experimental and analytical investigations on
bearing capacity of strip footing in reinforced sand backfills and flexible retaining wall”.
Acta Geotechnica 7 (2012) 357–373.
9. K.G. Garg. “Retaining wall with reinforced backfill-a case study”. Geotextiles and
Geomembranes 16 (1998) 135-149.
10. Satyendra Mittal, K. G. Garg and Swami Saran. “Analysis and design of retaining wall
having reinforced cohesive frictional backfill”. Geotechnical and Geological Engineering
24 (2006) 499–522.
