A method proposed for the assessment of failure envelopes of cemented sandy soils

This study aims at quantifying the influence of the amount of cement (C), the porosity (η) and the porosity/cement ratio (η/Civ) in the assessment of the Mohr–Coulomb failure envelope of artificially cemented sands centered on splitting tensile strength (σt) and unconfined compressive strength (σc). Based on the concept previously established by Consoli et al. that the σt/σu relationship is unique for each specific sandy soil and cement agent, it is shown that the effective angle of shearing resistance of a given cemented sandy soil (Ø′) is independent of the porosity and the amount of cement of the specimen and that effective cohesion intercept (c′) is a direct function of the unconfined compressive strength (σc) [or splitting tensile strength (σt)] of the improved granular material, which depends on the porosity/cement ratio (η/Civ) of the soil–cement blends. These concepts are tested with success for a uniform fine sand treated with early strength Portland cement and a silty sand treated with ordinary Portland cement, considering weak, moderate and strong cementation levels, as well as for a volcaniclastic formation deposit composed of moderately cemented fine sand and silt-size particles (naturally cemented soil). The methodology developed herein allows estimating c′ and Ø′ for any specific condition comprised inside the range of porosity and amount of cement employed during basic testing, without the necessity of carrying out triaxial testing or any other complex and time consuming tests.