The construction of diaphragm walls and large-diameter bored piles is normally carried out using drilling support fluids to temporarily stabilise the .. Read more deep excavation prior to concrete placement. In most cases such drilling fluids are either mineral-based slurries (bentonite), polymer support fluid systems or simply water. The working mechanisms of these three fluid types are fundamentally different. Even though fluid stabilized deep excavations are often not categorized as temporary works, reliable assessment methods and material specifications for the stability evaluation of such deep excavations are required. Robust design principles for bentonite slurry supported temporary excavations have been developed in the last few decades and the working principles and associated risks of such mineral-based slurries are understood reasonably well. However, polymer supported excavations follow different principles to assess the temporary stability of deep excavations and different assessment methods are required. The possible fluid related impacts on the permanent design performance of bored piles or other deep foundations need to be considered by permanent works designers to ensure the performance criteria are met.
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