P R E S E N T E D B Y

M O H A N K U M A R . P

A J A Y . R

R A J U . M

G O W T H A M A N . V

M O H A N K U M A R . L

V A Z H V I N I Y A N

REINFORCED EARTH WALLS

Objective:

Our objective is to do a brief study on various reinforced earth

walls and to identify the various defects and improvement

techniques.

To explain in detail about the construction methodology of

Reinforced Earth Wall.

Reinforced earth wall is a combination of earth and linear

reinforcing strips that are capable of bearing large tensile stresses.

Soil :- strong in compression.

Reinforcement:-strong in tension.

Ancient reinforcement:-tree branches , roots of vegetation , tree

trunks , straw , bamboo etc.,

Modern reinforcement:-Steel , Concrete , Glass fibre , Wood ,

Rubber , Aluminium.

What is a reinforced earth wall?

History

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.

Components of Reinforced Earth

1.Soil

2.Skin

3.Reinforcement

It should be granular, cohesion less material, not too much silt or clay having

particle size not more than 125 mm.

Plasticity Index (PI) shall not exceed 6.

The materials shall be substantially free of shale or other soft, poor durability

particles.

The material shall have a magnesium sulfate soundness loss (or an equivalent

sodium sulfate value) of less than 30 percent after four cycle.

The fill material must be free of organic matter and other deleterious substances, as

these materials not only enhance corrosion but also result in excessive settlements.

Pea gravel ( a backfill material of good quality in terms of both friction and

drainage )is recommended to prevent buildup of high lateral pressures from the

compaction and to prevent facing panel movement.

Selection of soil for the Reinforced Zone

Back Fill requirements for the Reinforced Zone

Recommended limits of electrochemical

properties for backfills when using steel

reinforcement

Recommended backfill requirements for

MSE & RSS construction

Skin is the facing element of the reinforced soil wall.

These elements 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.

Skin or Facing

Reinforcing Material

A variety of materials can be used as reinforcing materials e.g,

Steel

Concrete

Glass fibre

Wood

Rubber

Aluminium

Reinforcement may take the form of strips, grids, anchors & sheet material, chains,

planks, rope, vegetation and combinations of these or other material forms.

Image of some geogrids

In the reinforced earth wall two type of stability checked:

External stability : It consider the reinforced structure as whole and check the stability for

sliding, overturning, bearing/tilt and slip by considering the effects of dead loads, other loads

(live load, dynamic load etc.) and forces acting on the structure.

Internal stability:

It cover internal mechanism ( tension and pull out failure) such as shear within the structure ,

arrangement and behavior of the reinforcement and backfill. It checks the stability for each

reinforcement layers and stability of wedges within the reinforced fill

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

Design of Reinforced Earth Retaining Wall

WORK CARRIED OUT SO FAR:

Visited the flyover near green circle-New Bus Stand –Vellore.

Gathered information about reinforced earth walls on web.

We have concentrated only on the basic concepts.

RESULTS:-

Reinforced earth 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.

Do not require experienced craftsmen with special skills for construction.

Require little site preparation.

Need little space in front of the structure for construction operations.

Do not need rigid, unyielding foundation support, because reinforced or

mu1tianchored structures are tolerant to deformations.

Discussions:-

Require a relatively large space behind the wall face to obtain enough wall

width for internal and external stability.

Require granular fill (At sites where there is a lack of granular soils, the cost

of importing suitable fill material may render the system uneconomical).

Usually require a drainage system for ground nailing which may be difficult

to construct and maintain.

Corrosion of steel reinforcing elements, deterioration of certain types of

exposed facing elements such as fabrics or plastics by ultra violet rays, and

degradation of plastic reinforcement in the ground may occur so it must be

addressed in each project by means of suitable design criteria.

THANK YOU