Cement-Based Rock Grouting: Shear Rate Dependencies-Paper

Paper

Pdf Summary

The paper examines how shear-rate-dependent behavior affects the use of the Bingham model to predict cement-grout spread in rock fractures. Although the model is widely used in grouting design, it does not inherently account for wall slip, thixotropy, or unstable flow at low shear rates.

The authors identify two important flow-curve parameters: the <strong>no-slip shear rate</strong>, above which wall-slip effects are minimal and Bingham fitting is more reliable, and the <strong>critical shear rate</strong>, below which stable flow cannot be maintained and grout may stop abruptly. They incorporate these parameters into the Real Time Grouting Control (RTGC) design process and present a nomogram connecting relative grout spread, time, and wall shear rate. Comparing predicted wall shear rate with the critical value can help assess whether grout will continue flowing at a target distance.

An example using rheometry data shows that fitting Bingham parameters over a range affected by wall slip can substantially distort design estimates. It predicts a greater maximum propagation distance and lower flow rates than fitting only above the no-slip threshold, potentially leading to inaccurate stop criteria and assessments of grout progress.

For commonly used Swedish grouts with water-to-cement ratios of 0.6–1.1, the authors suggest a Bingham fitting range of 20–300 s⁻¹, alongside longer-duration tests to estimate the critical shear rate. They conclude that standardized shear-rate measurement protocols could improve consistency and design reliability. Future research should test more realistic rheological models and fracture conditions.

Keywords

Bingham model

cement grout

rock fractures

shear-rate-dependent behavior

wall slip

thixotropy

critical shear rate

no-slip shear rate

Real Time Grouting Control

rheometry data