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Soil Replacement

Terefil® Raft for Soft Soils

Overview

The Better Alternative to a Gravel Raft

Improving ground conditions in areas with soft, compressible, or liquefiable soils.

New Zealand has a complex geology including soft, compressible and liquefaction-prone soils. In recent years, New Zealand has experienced a growing demand for ground improvement due to increasing population and urbanisation. This has resulted in an increase in the construction and retrofit of buildings and infrastructure, which need suitable foundations to ensure their long-term durability and safety. 

Soil replacement involves the excavation and removal of unsuitable soil and its replacement with engineered fill material. This method is effective for improving ground conditions in areas with soft, compressible, or liquefiable soils. Mainmark uses Terefil to create lightweight, cellular concrete rafts prior to building construction, which aids in offsetting the structure’s weight.

Terefil is a Mainmark technology to create a lightweight foamed or cellular concrete.

Foamed concrete has found extensive use in construction and civil engineering applications due to being lightweight while still retaining good compressive strength.

Terefil is created when a foaming agent is added to a cementitious slurry, forming a large number of air bubbles within the mixture. These air voids give foamed concrete its characteristic low density. The lower density makes it much lighter than traditional concrete, while its highly fluid nature makes it easy to uniformly fill areas around pipes and other obstacles.

In a ground improvement application, Terefil is used to create a lightweight raft prior to building construction. Weak, compressible or liquefiable soils are excavated to a designed depth and replaced with foamed concrete. This reduces the weight on the underlying soils and provides an engineered fill material with consistent strength and stiffness properties.

Terefil® light-weight raft numerical modelling

Mainmark and Tetra Tech carried out numerical modelling to compare the performance of an unimproved soft soil site to both gravel raft and Terefil raft solutions.

The modelling takes into account the thickness and density of the Terefil, as well as site specific variables like the depth of groundwater.

Results show that a Terefil raft performs twice as well as a reinforced gravel raft. Additionally, the Terefil raft was able to reduce differential settlement at only half the thickness of the reinforced gravel raft.

If you would like a copy of this modelling for your future project, get in contact with us today and one of our Technical Sales Managers will be in touch with further information. 

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© 2024 The Mainmark group of companies. ‘Mainmark®’, ‘Terefil®’, ‘Terefirm®’ and ‘Teretek®’ are trademarks of the Mainmark group of companies.

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