Foundation underpinning in Australia is a ground improvement process performed by soil stabilisation experts. It’s a construction technique, yet many structural engineers and ground repair specialists contend there is art to the planning and designing of the ground improvement.

Since the goal is to strengthen the soils on which the existing foundation stands, the underpinning process has to be well-planned and carefully supervised. It’s important that the correct technique, the right approach, and the proper procedures be applied. Otherwise, the results of a poorly installed or faulty underpinning system could lead to a disastrous outcome.

Comprehend Why Soil Structure Changes

When the ground on which the foundation of a house or any kind of building shows signs of instability and caving in, it denotes that adverse changes are happening to the soil structure. Whether the changes are due to a poor assessment of the land before the building was constructed, or certain external influences have caused the soil structure to change, the ground must be reinforced to prevent the existing building from sinking or caving in.

Comprehend that reference to soil structure denotes the arrangement and combination of the solid particles and aggregates forming the underground soil. Aggregates are different mineral and organic matters such as plant and root litter that formed into large secondary units composing the soil structure.

However, aggregates tend to create voids that allow the introduction of large amounts of water and air into the ground. If so, such occurrences can adversely change the suitability of the soil in use as a building foundation. In time, the aggregates providing the spaces will make the underground soil unstable and at risk of eroding, once too much water and air fill up the voids.

Aside from citing climate change as the current main cause, there are actually numerous factors that influence the occurrence of changes in soil structures. The type of plants and roots making up the vegetation, the tillage, the fertilisation method, the microorganisms inhabiting the soil and other elements brought on by air and water, can all cause soil instability. Their presence can alter the porosity, consistency, density and bulk of the soil structure and affect ground ability to function as a stable foundation.

Damaged plumbing systems or flooded basements can cause water to seep into the ground and fill the voids created by aggregates. That is why basement waterproofing is also an important aspect of building constructions.

Examples of Underpinning Techniques to Improve Soil Structure

Three of the most common underpinning techniques that structural engineers and ground specialists consider as effective solutions, include Mini-Pile, Beam and Base and Mass Concrete

The Mini-pile technique aims to provide deep foundation support as this method uses high strength threaded bars or mini steel casings that reach far below ground level. They then anchor the building’s foundation to a more stable underground surface.

Beam and Base as the caption denotes, is an underpinning technique involving the installation of supporting beams and mass concrete base as support for the foundation. The design of the base and beams must ensure the even distribution of the building load.

Mass Concrete Underpinning is recommended for shallow ground improvements, of which chemical grouting systems are the most common solutions for strengthening soil structures.