Donzala D. Some^{1, 2,}, Ohindemi G. Yameogo³, Magai N. Thon⁴

In the domain of soil-cement, especially within the deep mixing method (DMM), various factors influence the strength of cement-stabilized soft soils. These factors include soil candidate consistency parameters, cement content, water-cement ratio (W/C), mixing time, and curing time. Notably, a lower W/C ratio resulted in a higher unconfined compressive strength (q_u). However, in the context of improving soft and cohesive soils through DMM, a W/C ratio of 1.0 has conventionally been recommended due to its favorable resistance. In the case of the Saga lowland, where a soft cohesive soil with high compressibility and low strength is prevalent, the standard practice employs a W/C ratio of 1.0 with a selective amount of cement for different layers, in most projects. This research introduces an innovative approach: utilizing a higher W/C ratio of 1.5 with a cement content of 110 kg/m³, to fulfill the standard strength requirement and above all, to have a well-distributed strength inside the material. This could prevent the lateral displacement of the soil-cement columns. Through laboratory experiments, this paper investigates the effects of increasing W/C on the strength distribution. As result, the comparison between the needle penetration strength (q_unp) /C= 1 and 1.5 showed that the latter represents a slight reduction in strength, but it is more uniformly distributed. This approach is designed to a bolster support for the existing infrastructure in the Saga lowland. The significance of this study in the field of DMM lies in advocating for an increased W/C ratio to ensure not only the quality of the mixture but also, more importantly, the uniformity of strength within the soil-cement columns.

water-cement ratio, strength distribution, soil-cement material, needle penetration index