Structural foundation or deep foundation is a type of foundation that is used to transferring the structural loads in to the subsoil. These are several ways of transferring structural loads into the subsoil on sites where ground conditions are unfavourable. The bearing capacity of the subsoil can be increased by ground improvement techniques such as :

• replacement of non-load bearing layers of soil close to the surface.
• soil consolidation using pre-loading or vertical drains.
• soil compaction using grout injection; deep vibration or stone columns.

Alternatively, structural loads can be transferred to stronger competent strata at depth by the use of :

• bored piles
• diaphragm wall elements
• mixed in place (MIP) piles
• piles reinforced by steel bars
• vibrated concrete columns

Technical literature on all these special alternative construction techniques is available on request from foundation contractor. There are several ways to build structural foundation or deep foundation, they are retaining wall and bored piles.

Retaining Wall

Retaining wall is a type of structural foundation or deep foundation, which is used to transfer the structural into the subsoil. The problem of providing stable retaining structures close to existing buildings or of constructing watertight excavation pits can be solved in a number of ways. However, the most appropriate solution is almost always the installation of a bored pile retaining wall.

Bored Piles

In general bored piles offer the most economical foundation as they can be constructed in a wide choice of diameters, typically ranging from 300mm to 1800mm, and to depths of up to 70m at rakes of up to 1:4. They can thus be tailored precisely to the particular requirements of the building or excavation. This flexibility means that bored piles can provide solid foundation elements suitable for almost all site conditions.

* Friction Pile

* End Bearing Pile

Bored piles can be classified into two main groups, according to their load bearing behaviour: friction piles, which transfer loads mainly by frictional resistance along the shaft; and endbearing piles in which load is primarily transferred to the surrounding soil of through the pile base. Depending on the structural requirements, bored piles may be constructed singly, in groups or as walls using secant, contiguous or king piles, with or without infill.

* Single Piles

* Pile Groups

* Vertical And Raked Piles

* Piled Wall

Contractors use sheet pile as a temporary supportive wall which is used to support the soft soil collapsed from higher ground to lower ground. Sheet pile is commonly used in the construction and has variety types of material for sheet pile. The price for variety types of material for sheet pile is different, the driving method can be in variety ways as well. Contractors might need to determine the condition of soil then only can decide which type of sheet pile can be used.

Simple Guide On How To Install Sheet Pile

Sheet pile installation can’t be done by piling contractor while there is specialist contractor for sheet pile to do the installation. Here is a rough installation procedure for sheet pile :

1) Pile Driving Equipment
Before starting driving sheet pile, a few equipments have to be prepared such as driving hammers and jetting equipment. The driving energy for hammers shall be recommended by the manufacturer so that it’s applicable to relevant sheet pile. While jetting equipment shall have a minimum of two removable or fixed jets of the water or be a combination of air a water type.

2) Placing and Driving
After preparing all the sheet pile driving equipments, sheet piles can be started to place on the location that shown in the construction drawings. Temporary wales, templates, or guide structures have to be carried on to ensure the sheet pilings are placed and driven to the correct alignment.

After the sheet piles is set on place, jetting machine will be starting to driving the sheet piles. Sheet piles have to be driven with the proper size of hammer and by approved methods to ensure no damage to the sheet piles and proper interlocking throughout their lengths. A protecting cap shall be employed on the tops of sheet pile to prevent damage during driving with hammer.

3) Cutting-Off and Splicing
After driving the sheet piles into the ground, if contractor find that they need additional penetration, splicing or jointing works will be carried on. Driving works will be done again for the sheet piles until it reaches its’ limit on the ground. After this, excessive of sheet pile will be cutting-off and removed from the site. All cutting-off work must be done in a neat and workmanlike manner for safety purpose.

4) Inspection of Driven Piling
The contractor shall inspect the interlocked joints of driven sheet piles extending above ground. If contractor find out that the sheet piles are out of interlock, then the sheet piles have to be removed and replaced with a new sheet pile.

5) Pulling and Redriving
After the inspection of driven piling, another similar process has to be carried on which is called pulling and redriving. The contractor shall pull selected sheet piles to determine the condition of the underground portions of sheet piles. If contractor found any damages to the extent that its usefulness in the structure is impaired, then the sheet piles have to be removed and replaced with a new sheet pile.

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Source : Sheet Pile

Sheet pile is one of type of piling, one of the difference between normal pile and sheet pile is sheet pile used as temporary while normal pile used as permanent. Sheet pile can be made from many types of materials such as steel, plastic, wood, vinyl, recast concrete, and fiberglass. While the most common material to be used for sheet pile is steel sheet pile.

Sheet pile is act as a temporary supportive wall that been driven into a slope or excavation to support the soft soils collapse from higher ground to lower ground.

Sheet Pile Applications

Sheet piling can be applied in many common environmental applications, sheet piles are wisely used in the following fields of application :

* Retaining walls
* Bridge abutments
* Tunnels
* Pumping station
* Water treatment plants
* Basements
* Underground car parks
* Port facilities
* Locks and dams
* Waterfront structures
* Piled foundations
* Excavations and trenches
* Landfill
* Cofferdams
* Ground Water Diversion/Control
* Barrier for Ground Water Treatment Systems
* Containment Walls
* Flood Protection
* Coastal Protection
* Tunnel Cut and Cover
* Bulkheads and Seawalls
* Weir Walls
* Slope Stabilization
* Baffle Walls

Driving Method

There is few driving method for sheet pile driving such as pitch and drive, panel driving and staggered driving.

1) Pitch and Drive
Pitch and drive is the simplest method for sheet pile driving, it involves driving each sheet pile to full depth before pitching the next one. However it is only suitable for loose soils and short piles.

2) Panel Driving
The purpose of using panel driving is to ensure that the sheet piles are driven with good alignment and verticality. The risks of driving difficulties and problems of de-clutching also can be minimised.

Because a whole panel of piles has been pitched there is no need to drive all piles fully to maintain piling operations. If obstructions are encountered, individual piles can be left high without fear of disruption to the overall efficiency.

Panel driving is suitable for dense sands and stiff cohesive soils or in the case of potential obstructions.

3) Staggered Driving
In difficult soil conditions, panel installation combined with staggered driving is more suitable in driving process.

The piles are installed between guide frames and then driven in short steps as follows: piles 1, 3 and 5 first; then piles 2 and 4.

If the soil is very dense sand, gravel or rock, piles 1, 3 and 5 can be reinforced at the toe. In this case, these piles are always driven first and piles 2 and 4 in the second stage.

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Source : Napier | Sheet Pile