Effect of slippery bentonite

[Kiri Robbie]

When the pile is in place, it could be surrounded by a slippery bentonite layer along its full length. What is the effect of this layer if you are relying on friction as part of the load bearing strength of the pile?

[Martin Larisch]

Great question. Depending on your ground conditions and the quality of your bentonite fluid, the ground surrounding the pile could be subject to reductions in shear strength due to a potential bentonite layer covering your soil particles.

With high quality bentonites and sandy soil conditions, such effects are less likely to have an impact. However, pile load testing can provide some evidence.

If you would use bentonite fluid (or water) in swellable clays or shale formations, you should expect surface deuteriation of the clay with reduced shaft resistance compared with the undisturbed ground conditions. For clay soils, polymer systems are more suitable as they won't disturb the clay/ shale at the inside of the borehole.