“Borehole Stabilization” for Deep Excavation, An Essentials Part in Bored Piling / Diaphragm Wall Construction-PPT Presentation

PPT Presentation

Pdf Summary

The presentation explains why borehole stabilization is essential to deep excavations and bored-pile or diaphragm-wall construction. Stable excavations require support pressure from the drilling fluid to exceed the combined earth and water pressures acting on the borehole. The fluid must remain in the excavation, be removable before concreting, and be displaced cleanly during concrete placement.<br /><br />Bentonite and polymer slurries provide this support through different material properties. Bentonite hydrates over several hours, swells, and develops a thixotropic gel. At the borehole wall it can form a low-permeability filter cake, helping retain slurry pressure. Polymer slurry mixes more quickly and can achieve high viscosity with relatively little material. Its long-chain molecules bind water and can form a membrane within soil pores. Polymer slurries are lighter than bentonite slurries, which allows solids to settle faster.<br /><br />The appropriate slurry depends on site conditions, including soil permeability, excavation depth, groundwater, water chemistry, and available logistics. Relevant guidance and specifications provide slurry parameters, but often offer limited help in selecting the most suitable fluid.<br /><br />Bentonite is well-established and suitable for many foundation projects, but deep, large-diameter excavations can make its use time-consuming, complex, and costly. Slurry recycling may take many hours, leaving limited time for installing reinforcement and placing concrete. The presentation emphasizes that slurry selection and management affect construction time, safety, environmental impact, cost, and foundation quality. It also highlights the need to consider plant capacity, desanding and recycling, disposal, testing, and quality control.

Keywords

borehole stabilization

deep excavations

bentonite slurry

polymer slurry

drilling fluid

diaphragm wall

bored pile

filter cake

groundwater pressure

slurry selection