Sealing mechanism of slurry materials considering temporal and spatial variation of viscosity

The borehole sealing technique is an important method for anti-seepage and grouting reinforcement of soft soil strata. However, the bottom-up injection method and the time-varying characteristics of viscosity will cause the viscosity of sealing slurry to present a nonuniform spatial distribution in through range. The rheological parameters and flow patterns of the sealing slurry are obtained through rheological tests. The sealing model for concentric annular fracturing sealing slurry of Bingham fluid is established considering the temporal and spatial variation of viscosity, and the relevant governing equations are deduced. The sealing capacity of slurry is quantitatively analyzed, and the research results are successfully applied to the anti-seepage and grouting reinforcement of a levee. The results show that the temporal and spatial variation of viscosity of slurry has a great influence on its sealing capacity which is related to the rheological parameters of slurry, plastic strength of slurry and height of borehole. The ultimate grouting pressure of the sealing slurry increases with the increasing amount of curing agent or its increasing plastic strength and such phenomenon is obviously reflected with the increasing height of borehole. Considering the issues of grouting plugging and pipe pulling, the water-solid ratio of the sealing slurry should be controlled to be about 1:1, the clay content should not exceed 50%, and the content of curing agent should be controlled in the range of 1.2% to 1.8%. The on-site borehole sampling and pump-in tests show that the continuity and integrity of the soil strata are significantly improved after grouting and the anti-seepage reinforcement standards are achieved. Although the theoretical derivations have certain errors with the measured results, they can conform to the actual engineering requirements. The research results are conducive to the further application of the slurry sealing technique, and they may provide theoretical guidance for engineering practice.