A laboratory scale model analysis of stock raft foundations and ventilated foundation systems constructed on expansive clay soils.
Bester, Dirk M. Theron, Elizabeth Stott, Philip R. Snyman, Jacques
Bester, Dirk M.
Theron, Elizabeth
Stott, Philip R.
Snyman, Jacques
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Abstract
Constructing raft foundations for houses on expansive clay soils has gained popularity. Raft foundations evenly distribute the building's weight over the entire footprint rather than at individual points like a traditional strip foundation. They offer advantages such as enhanced stiffness, moisture control underneath the foundation, and structural integrity. However, they are not without drawbacks. Raft foundations typically have higher initial costs, increased excavation depth, and the potential for heaving underneath the foundation. To address these challenges, some designers have recently proposed and implemented solutions from companies like Geoplast or VoidForms, which involve creating ventilated foundation systems where the foundation slab is suspended with a cavity underneath it. These ventilated foundation systems incorporate large voids that allow the heaving of expansive clay soil inside and air circulation to aid in moisture evaporation. It is proposed that allowing the expansive clay soils to heave inside the foundation system will reduce overall movement and potential structural damage to the house. The study employs scaling laws to compare the performance of a standard raft foundation typically used in South Africa with a ventilated foundation system in a controlled laboratory environment. The study seeks to determine which foundation system performs more effectively under expansive soil conditions. By evaluating the advantages and disadvantages of both foundation types and their behaviour on expansive clay soils, this research aims to contribute to informed decision-making in the context of South African construction practices. The findings of this comparative study hold the potential to guide designers and builders in selecting the most suitable foundation system, taking into consideration local soil conditions and the desire for long-term structural stability.
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Date
2024-06-16
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Science and Education Publishing (SciEP)
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Keywords
Raft foundation, Ventilated foundation, Heave, Expansive clay, Small-scale models