A Filtration Model for Constant Flux Permeation of Bentonite Grout through Granular Soil

The flow of suspensions through porous media is a complex phenomenon owing to the diversity of the mechanisms involved. It is important to determine the filtration behavior to understand the decline in injectivity of suspension as flow progresses and for that, knowledge of the rate of particle deposition is crucial. In this paper, a numerical model has been developed for the permeation of bentonite suspension grout through granular soil. The filtration model defines the rate of deposition of solid particles which depends on the rheology and concentration of grout, particle size and shape of suspended particle, grain size distribution of porous media, and physio-chemical interaction of grout with the porous medium through which it is flowing. The novelty of the newly proposed numerical model is that it accounts for the change in rheology of grout and the porosity and permeability of the porous medium as a function of the deposition of particles, none of which has been considered in the past. In this paper, six filtration models were used with different filtration coefficients and solid deposition empirical relationships. It was found that using a filtration coefficient that increases linearly with cumulative solid deposition was best suited to model the filtration mechanism of bentonite suspension grout permeation in granular soil. Bentonite content profile along the height of the sand column determined numerically using the proposed filtration model was similar to that obtained from the experimental results from post-permeation analysis.