Studies on the influence of water filtration on the strength parameters of lime-stabilized soil

The stabilization of cohesive soils intended for use in water-retaining embankments with quicklime is not a popular technology in the hydrotechnical industry. This is associated with the potential for lime to leach from the soil structure, thereby reducing the strength of the material used. An experiment was designed and carried out to force water to flow through cohesive soil compacted at the optimum moisture content. The strength parameters of the soil were determined on the basis of a test in a large-scale direct shear apparatus. Even in its natural form, the tested soil was characterized by high cohesion (average 103.47 kPa) and a high internal friction angle (average 27.05◦). As a result of water filtration, a slight average increase in these parameters was observed, by 13.01% (cohesion) and 11.87% (internal friction angle). Between 2.75 and 8.0 dm3 of water was filtered through the individual samples, and the lime concentrations were low, between 53.7 and 98.9 mg/dm3. After the soil was stabilized with lime, both analysed parameters increased – cohesion averaged 148.98 kPa and internal friction angle 33.53◦. As a result of water filtration through the stabilized soil, the increase in cohesion was inhibited and the average internal friction angle decreased by 16.49%. Between 3.05 and 11.5 dm3 of water was filtered through the individual samples, and the lime concentrations ranged between 380.8 and 915.4 mg/dm3. No correlation was found between the amount of lime leached and the maximum shear strength values obtained for a given soil sample. Despite the high water pressure (4.5 meters of water gauge), long filtration time (40 days), and short period between compaction and the start of flow (approx. 3 days), the tests did not confirm any risk of a significant reduction in the strength parameters of the lime-stabilized soil as a result of water impact.