Water Retention Curve of Biocemented Sands Using MIP Results

Abstract

Biocementation is a soil treatment technique wherein bacteria living in soil pores promote the precipitation of calcium carbonate. One of the most recent applications of this treatment is to provide resistance against the erosion of slopes by creating a resistant cover but still allowing infiltration to avoid water runoff. For modeling infiltration, it is fundamental to know the water retention curve of the treated material. This may not be an easy task because the soils most suitable for biocementation treatment are sands, due to their large pore sizes and consequent high permeability. The water retention curves (WRCs) of such types of soil are characterized for having a very small air entry value, followed by an almost-horizontal zone, which cannot be measured by using the vapor equilibrium, most of the existing sensors, or a water dewpoint potentiometer. Data from mercury intrusion porosimetry (MIP) tests can be used as an alternative to find the WRC, and this is explored in this paper. The model for the water retention curve presented considers the deformability of the soil during the MIP test, assuming an isotropic elastic behavior. The WRC derived from the MIP tests is well-fitted to the points measured by using a water dewpoint psychrometer (only for suctions above 1 MPa) and vapor equilibrium.

Microbial Precipitation of Calcium Carbonate for Crack Healing and Stabilization of Sandy Soils

“…After four weeks, soil stabilization was confirmed by the formation of a soil cake, after which the soil hardness and the amount and mineralogical properties of CaCO 3 were evaluated. The amount of CaCO 3 in the soil cake was measured using a leaching method with 0.5 M hydrochloric acid [29]. The CaCO 3 content (%) was determined using Equation (2):…”

A simple model for the water retention curve of compressible biocemented sands using MIP results

“…Biocementation treatment consists in using bacteria or other biological agents to promote the precipitation of calcium carbonate (biocement) in the soil pores, improving overall mechanical behavior and reducing permeability [1]. The study of the water-retention properties of biocemented soils is scarce [2][3][4], however it is important to model water infiltration, as it occurs during the treatment and in service conditions. This is particularly important when the treatment is done to provide resistance against erosion of slopes [5].…”