One of the most common problems I hear from contractors in the drilled shaft industry is having issues with material sloughing in and losing the bottom half of a hole. A few simple steps can go a long way when you begin assessing the issues you're encountering using polymer slurry.
Viscosity is measured using a Marsh funnel and cup. Most manufacturers have thresholds they recommend for different soil types. The more cohesive the soil is (silt and clay), the lower the viscosity can be. The looser the soil is (sand, gravel and cobbles), the higher the viscosity should be. It is important to run this test because viscosity is what holds it all together and will identify whether more product needs to be added because of fluid loss, degradation or contamination. Monitor the slurry's pH to ensure itÕs between an 8 and 10 to optimize its performance. This already is assuming you're adding soda ash to your mix water. Make sure you follow the manufacturer's instructions and mix ratios, as these have been established in a lab to cover you in most, if not all, situations. If the viscosity is higher than what is recommended, it is not necessarily a bad thing, but more of an insurance policy. It will just take more time for fines to settle out, which can cause some issues if you are required to run a sand content test before placing a cage. It is when your viscosity is too low that you may encounter issues with sloughing or even excessive fluid loss into the formation.