Influence of the Amount of Cement on the Drained Shear Strength Parameters of Clay Soil Obtained Through the Direct Shear Test

The subject of this paper is the way, in which the amount of cement and the curing time influences the parameters of shearing resistance of clay soil obtained through the direct shear experiment that is routinely conducted in geotechnical laboratories. The direct shear test was performed on silty clay soil samples compacted according to the standard Proctor test, with the compaction degree equal to 95% of the maximum achievable compaction. The shear strength of samples containing 0, 3, 5, 7, and 9% of added cement was tested, and for curing times of 3, 7, and 14 days. The drained shear strength parameters ϕ′ and c′ were obtained by processing the results in Excel. The drained cohesion increases with increasing the percentage of cement and curing time. The internal friction angle increases with the increase of the percentage of cement up to a certain limit, while a decrease in the internal friction angle value is recorded between 5 and 7% of added cement. In contrast to cohesion, the internal friction angle decreases with the extension of the curing time of the samples.