Importance of Geotechnical Instrumentation

Introduction

Foundations provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics. There are a very wide range of foundation types available, suitable for different applications, depending on considerations such as:

• The nature of the load requiring support.
• Ground conditions.
• The presence of water.
• Durability of the materials.
• Cost.
• Accessibility.
• Sensitivity to noise and vibration.
• Proximity to other structures.

Very broadly, foundations can be categorised as shallow foundations or deep foundations. Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils. Deep foundations are necessary where the bearing capacity of the surface soils is insufficient to support loads imposed and so they are transferred to deeper layers with higher bearing capacity.

Pile foundations are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber. A foundation is described as 'piled' when its depth is more than three times its breadth (Atkinson, 2007).

Pile foundations are principally used to transfer the loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth, increasing the effective size of a foundation and resisting horizontal loads. They are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement.

Pile classifications

Piles may be classified by their basic design function (end-bearing, friction or a combination) or by their method of construction (replacement (driven) or displacement (bored)).

End-bearing piles develop most of their friction at the toe of the pile, bearing on a hard layer. The pile transmits load direct to firm strata, and also receives lateral restraint from subsoil.

Friction (or floating) piles develop most of the pile-bearing capacity by shear stresses along the sides of the pile, and are suitable where harder layers are too deep. The pile transmits the load to surrounding soil by friction between the surface of the pile and soil, which in effect lowers the bulb of pressure.

Driven piles

Driven (or displacement) piles are driven, jacked, vibrated or screwed into the ground, displacing the material around the pile shaft outwards and downwards instead of removing it.

Driven piles are useful in offshore applications, are stable in soft squeezing soils and can densify loose soil.

There are two groups of driven piles:

• Driven in situ: Either with a permanent concrete or steel casing, or with temporary casing.
• Preformed: Prefabricated off-site from timber, concrete or steel.

For more information, see Driven piles.

Bored piles

Bored (or replacement) piles remove spoil to form a hole for the pile which is poured in situ. They are used primarily in cohesive subsoils for the formation of friction piles and when forming pile foundations close to existing buildings.

Bored piles are more popular in urban areas as there is minimal vibration, they can be used where headroom is limited, there is no risk of heave and where it may be necessary to vary their length.

For more information, see Bored piles.

If the boring and pouring takes place simultaneously, piles are called continuous flight auger (CFA) piles.

Screw piles

Screw piles have a helix near the pile toe so they can be screwed into the ground. The process and concept is similar to screwing into wood.

For more information, see Screw pile foundations.

Micropiles

Micropiles (or mini piles) are used where access is restricted, for example underpinningstructures affected by settlement. They can be driven or screwed into place.

For more information, see Micropiles.

Pile walls

Pile walls can be used to create permanent or temporary retaining walls. They are formed by placing piles directly adjacent to one another. These can be closely-spaced contiguous pile walls or interlocking secant walls; which depending on the composition of the secondary intermediate piles can be hard/soft, hard/firm or hard/hard secant walls.

For more information, see Sheet piles.

Geothermal piles

Geothermal piles combine pile foundations with closed-loop ground source heat pump systems. They provide support to a structure, as well as acting as a heat source and a heat sink.

In effect, the thermal mass of the ground enables the building to store unwanted heat from cooling systems and allows heat pumps to warm the building in winter. Generally, ground source heat pumps extract heat from the ground by way of underground pipes which are laid either horizontally or vertically in the ground. In geothermal piles, the pipe loops are laid vertically, within the piles themselves.

Importance of Geotechnical Instrumentation

Geotechnical instrumentation presents data and other important information which is generally used by engineers when they are working on any project. The information driven from instruments helps then in every phase of a project. Below we have listed reasons why we should use geotechnical instrumentation during construction.

1. The data retrieved from instruments can be used to verify design assumptions. It helps in recognizing need for any improvement in design in the future.
2. Geotechnical instrumentation tells engineers to characterize initial site conditions. The bore water pressure as well as slope stability are one of the common parameters of interest during site investigation.
3. Performance checking used during investigation process offers data that can be used while monitoring performance of any structure such as dam. During this investigation monitoring parameters may include deformation, leakage, etc.
4. It’s very important that projects follow quality norms, which are laid down by concerned authorities. With the help of geotechnical instrumentation, engineers are in a good position to enforce quality of the workmanship on any project and makes sure that things are matching the specifications.

5. The data fetched from the survey assists engineers as well as contractors when owners of the adjacent properties claim that construction has caused major harms to their buildings in the court.

Datum is a well-known name in the field of monitoring. If you have been looking for the best monitoring or instruments services, then taking help from Datum monitoring is a great idea. They offer geotechnical monitoring, slope monitoring, railway monitoring, tunnel monitoring, etc. for a safer and easier work.