Concept of Reinforced Earth

Reinforcement in the form of steel or synthetic strips called geo-strips are placed within an embankment, containing soil in various layers compacted mechanically; the granular material of embankment is linked by means of friction. The embankment becomes a self supporting structure, such a structure is called reinforced earth structure.

Earth Reinforced with Geo-strips and Reinforced Earth Panels

Concept

Construction of reinforced earth is a very simple process. The principle concept of reinforced earth is similar to that of a reinforced concrete that contains steel, aggregates and fines. In reinforcing earth process we reinforce the earth by means of steel or synthetic geo-strips.

Stresses that are generated within the embankment is transferred and resisted by these reinforcing strips. 

Concept of Reinforced Earth Works (REW)

History

Constructions using these techniques are known to have existed in the 5th and 4th millenniums B.C. Since early civilizations, man has attempted to use soil with other materials to enable it for being used for his necessities. Typical early use includes us of branches of tree etc. to support tracks over marshy areas and to build hutments. Structures are also built by insects and birds using mud and leaves.  These are all familiar sights even today. This kind of principle is also used in building parts of Great Wall of China and the Babylonian Ziggurats i.e. temples.

Great Wall of China

In the 19th Century Passel used tree branches to reinforce back fills in order to reduce the earth pressure and thereby economize the retaining walls. 

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Textile material was perhaps first used in road construction in south Carolina in the early 1930s. The first use of a woven synthetic fabrics for erosion control was made in 1958 by Barrett.

Construction

Reinforced earth system consists of following items;

a) Facing or the skin of the embankment
b) Reinforcing geo-synthetic strips
c) Soil in lifts or layers

During the construction phase we first do a lean within the boundary of embankment upon which the reinforced earth panels or skin of the reinforcement is placed. In this boundary of panels we place the selected material containing fines and gravels in lifts or layers. Each lift is mechanically stabilized by using a roller. We in this case don’t use sheep foot roller or vibratory roller, we use simple steel drum roller to do the compaction as well as ensuring stability of the structure.

The skin or reinforced earth panels have a path or passage for geo-synthetic strips which is called connectors mostly they are in C shape so they are called C-Connectors.

A bridge Abutment

These strips after passing through C-Connector is jointed with a reinforced steel bars placed at center in a specified distance. With each lift the process repeats and as a result we get a well compacted reinforced earth embankment. Water sealant foam is applied between each panels to ensure it as a water tight structure.

Advantages

Following are some of few positivity in Reinforced Earth Works

Reinforced Earth Panels Facing

a) Easy Placement

Construction is repetitive and simple, panels, strips, granular fill and then compaction

b) Positive Connection

Galvanized reinforcing strips are connected to concrete panels with structural bolts

c)    Engineered Backfill

Alternating layer of reinforcing strips and backfill are applied and compacted.

d)   Structural Facing

TerraClass facing panels are easily handled by placement crew.