Experimental Investigation on Rheological Behaviors of Bentonite- and CMC-Conditioned Sands

Abstract

The rheological properties of sands conditioned with different conditioners and injection ratios were examined. The conditioned sands were prepared with a 40% and 60% volume injection ratio of a bentonite slurry or a carboxymethyl cellulose (CMC) solution. The experiment results show that the tested bentonite-conditioned sand exhibits the characteristics of a Herschel-Bulkley fluid at shear rates in the range of 0–10 s−1 while the CMC-conditioned sand conforms to the power law model. The flow curves of all of the samples show a marked shear-thinning behavior. They also indicated that the existence of a yield stress (τ0) depends only on the rheological behavior of the conditioner and that the yield stress (τ0 if present) and the plastic viscosity (μp) increase with an increase in the volumetric concentration of the sand. Furthermore, to characterize the thixotropy of the conditioned sand, experiments were carried out by using three loading histories with shear rate accelerations of 0.1, 0.2 and 0.4 s−1/s. In the measured results, the thixotropy of the conditioned sand is heavily dependent on the recent flow history. Based on the experimental data, a simple thixotropic prediction model was developed to analyze and predict the transient flow curves of bentonite-conditioned sands.