Journal of Geoscience and Eco Agricultural Studies

Abstract

Bentonite support fluid plays a crucial role in the temporary stabilization of excavation walls during the construction of deep foundations or underground structures, primarily through the formation of a filter cake that limits fluid loss and transfers lateral pressure to the surrounding soil. While the effects of fluid properties and soil permeability have been widely studied, the impact of the initial water content of the host soil remains underreported. Thus, the results of a preliminary experimental study concerning the effects of soil water content on bentonite fluid filtration are presented here. Tests were conducted in a laboratory cell filled with sand in which a bentonite fluid was injected under a constant pressure of 100 kPa. Two initial water contents were tested: 2% and 8%, corresponding to degrees of saturation of 6% and 26%, respectively. Results revealed a three-phase filtration process: rapid infiltration, clogging and internal cake formation, and progressive filtration (external cake formation and thickening). At a water content of 2%, no filtrate was collected, indicating immediate pore clogging. At a water content of 8%, more than 3.2 L of filtrate was recovered. At the end of the bentonite injection, the final water content profiles in the soil (sand + retained bentonite fluid) were more uniform in the drier soil (water content = 2%) than for the wetter one (8%). Bentonite retention was uniform throughout the sand depth at 2%, while at 8%, the retention was greater across the soil depth. The filter cake was thicker in the drier soil than in wetter one. These results demonstrate that the initial water content of the studied soil influences filtration behavior and cake formation. Ongoing studies aim to further quantify this effect and support field practices adapted to site-specific moisture conditions.