Development of a Design Model for Selecting Optimal Parameters for Permeation Grouting Based on Soil Permeability Coefficient and Grout Rheological Behavior

Abstract

This study aimed to determine the optimal parameters of cement grout for permeation grouting and to develop a practical design model for selecting the water-to-cement ratio, injection pressure, and grout permeability coefficient according to soil permeability and grout rheological behavior. An experimental laboratory study was conducted using reconstituted sandy soils with different gradations and fines contents and cement grouts prepared at water-to-cement ratios of 0.6, 0.8, 1.00, 1.20, and 1.50. Grain-size distribution, soil permeability, grout rheology, stability, and permeation-grouting behavior were evaluated. Soil permeability tests were performed according to ASTM D2434-87, while rheological testing measured shear stress, shear rate, apparent viscosity, and yield stress. A specially designed laboratory grouting chamber was constructed to simulate grout injection through porous media under different pressures and to determine the grout permeability coefficient (KG). Data were analyzed using regression, curve fitting, correlation analysis, comparison with classical permeability relationships, and assessment of Darcy’s law. Cement grout exhibited Bingham non-Newtonian behavior across all tested mixtures. The fitted rheological equations showed high coefficients of determination, including R² = 0.9812, 0.9949, and 0.9881 for W/C ratios of 0.6, 0.8, and 1.00, respectively. Increasing the water-to-cement ratio reduced yield stress and plastic viscosity and improved penetrability. The hydraulic-gradient–flow-velocity relationship was linear at low pressure (i = 287.85v, R² = 0.8467) but became nonlinear at high pressure (i = 1773.9v^1.5152, R² = 0.9944), indicating deviation from Darcy behavior. KG increased with the water-to-cement ratio and was strongly governed by grout viscosity. Increasing injection pressure enhanced flow only up to a threshold, after which viscosity became the dominant controlling factor. The results demonstrate that successful permeation grouting depends on the coupled effects of soil permeability, grout rheology, water-to-cement ratio, and injection pressure; accordingly, the proposed design model provides a practical framework for selecting appropriate grouting parameters and evaluating groutability in sandy soils.