Types of sheet piles and Uses, classification Of sheet piles

08 Aug.,2022

 

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Types of sheet piles and Uses, classification, sheet piles walls

Sheet piles walls are also called bank heads. There are two types of cantilever sheet pile and an Anchored sheet pile. They are coming to some forces acting on sheet pile walls.

What is Sheet piles?

Sheet piles are generally thin piles. They make plates of concrete, timber, and steel. These piles are driven into the ground for either separating members or for stopping the seepage of water, they are not meant for carrying the vertical load.

Sheet piles walls and bulkheads

Sheet piles are sections of sheet material with interlock edges that are driven into the ground of providing earth retention and excavation support.

Generally, the sheet piles are made of steel or timber. However, sometimes R.C.C. Sheet piles also adopt. Steel piles are suitable for permanent structures in which the depth of driving exceeds 3 m.

Generally, the use of timber piles limits temporary structures in which the depth of driving is not greater than 3 m.

A sheet piles wall comprises a series of sheet piles driven side by side into the ground, thus producing a continuous vertical wall for the purpose of retaining an earth bank.

Types of sheet piles and Uses, classification, sheet piles walls

Types of sheet piles walls

  • Cantilever sheet pile
  • Anchored sheet pile

Cantilever sheet piles

There are two types of sheet pile

  • Free cantilever sheet piles
  • Cantilever sheet piles

Free cantilever sheet piles

It a sheet pile subject to a concentrated horizontal load at its top. Above the dredge level, there is no backfill. The free cantilever sheet pile obtains its stability wholly from the larger passive resistance of the soil below the dredge level into which it is driven.

Cantilever sheet piles

A cantilever sheet pile maintains backfill at a higher level on one side. The stability is wholly from the lateral passive resistance of the soil into which the sheet pile being driven, also similar to the free cantilever sheet pile.

Anchored sheet piles

Anchored sheet pile kept above its drive depth by anchors provided at a proper level. For the stability of the sheet pile, the anchors provide forces, in addition to the lateral passive resistance of the soil into which the sheet piles drive. The anchored sheet pile also divide into two types-

  • Free-earth support piles
  • fixed-earth support piles

Free-earth support piles

An anchored sheet pile has free-earth support when the depth of tip. Thus, in the pile, there is no point of contra flexure.

Fixed-earth support piles

An anchored sheet pile says to have fixed earth support when the depth of embedment is large. The bottom tip of the pile fixes against rotations. In the pile an, inflection point occurs because there is a change in the curvature of the pile.

Classification of sheets piles Walls

Sheets piles and bulkheads are classified as

As per the mode of Establishing the retaining system

As per the mode of establishing the retaining system, a bulkhead may be classified as

Fill Bulkhead

Dredged bulkhead

A fill bulkhead is the one that is built-in open water and then backfilled. If the bulkhead is built in the natural ground by driving and then the earth remove by dredging from its face, it is known as the dredged bulkhead.

Structural type and boarding scheme

This is an important classification, as per this criterion bulkhead may either be cantilever type of being anchored type. When a cantilever bulkhead drives its stability completely from the lateral resistance of the soil into which the sheet piling drive. An anchored bulkhead keep above its also driving depth by or more tie rods or anchored at or near its upper level.

As per sheet piles material

According to the sheet pile material a bulkhead may be classified as flexible or rigid. When a Flexible bulkhead, usually made of steel piles, deflects and bends under the effect of a lateral force. Its also stability depends upon the formation of enough lateral resistance of soil adjacent to the embedded length of the bulkhead, and upon the anchor rods. A rigid bulkhead, built of reinforced concrete sheet pile, derives its stability against lateral forces generally from its intrinsic structural strength.

The condition of the End support

As per the condition of end support, the bulkheads may be classified into two groups-

  • Bulkhead with free earth support
  • Bulkhead with fixed earth support

The classification applies only to the anchored bulkhead. In bulkhead with free earth support, the sheet piling drive to a short depth so that the bulkhead deflection is somewhat identical to that of a vertical elastic beam whose bottom end simply support. In bulkhead with fixed earth support the sheet piles drive to a considerable depth so that the bottom end of the bulkhead practically fixes in position.

Uses of sheet piles

  • Light in weight
  • Can reuse again and again
  • Easier to raise the pile length
  • Resistant to high driving stresses
  • Long service
  • Lesser deformation of joints when wedged full with soil stones during driving.

Forces acting on a sheet pile or Bankhead

Various forces act over a bulkhead, few of them act constantly while others only occasionally. There are various types of lateral pressures, which may be acting on to a sheet pile wall or bulkhead, namely-

  • Active and passive earth pressures
  • Lateral pressure earth pressure
  • Seepage pressure and unbalanced water pressure.
  • Mooring pull, ship impact, etc.
  • Wave pressure
  • Earthquake pressure

The classical earth pressure theories of coulomb or Rankine, which based on the condition of full mobilization of the shear strength of soil because of yielding of the wall laterally by sliding or by rotation about its bottom, do not apply for bulkheads where the conditions of deformation are different.

When the earth pressure against the sheet pile wall can found by theories that take into account the conditions of the yield of the wall. Various empirical and semi-empirical methods have designed based on classical earth pressure theories.

They are usually adopted for

  • Temporary construction
  • Waterfront structures
  • Lightweight construction where sub-soil is poor for supporting a retaining wall.

A bulkhead is a sheet pile retaining wall of waterfront, banked up by the ground. They are widely adopted for dock and harbor structures.

A bulkhead serves as a vertical wall so that shops may tie-up alongside. A bulkhead may also act as a pier structure that may just out into the water.

In contrary to the retaining walls, bulkheads flexible usually made of a single row of partially embedded sheet piles with a large portion of the lateral support furnished externally.

Practically, the upper and lower bulkhead edges fix on account of the anchorage at the upper level and the passive resistance of the soil adjoining the bottom part of the bulkhead.

The use of the anchor member tends to decrease the bending moment, the lateral deflection, and also the penetration depth of the pile.                                  

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