Diametric splitting strength of compacted expansive soils and modified soils at different water contents

The tensile strength of expansive soils is crucial to control the formation of cracks within the soil. Analyzing the tensile strength of such soils under different water contents has both theoretical significance and practical engineering applications for ensuring canal slope stability in the Middle Route of South-to-North Water Diversion Project. The expansive soil and cement-modified expansive soil (modified soil) collected from the high fill canal slope were made into samples with a water content of 3% to 24%, respectively, and water holding and splitting tests were conducted on the two soils using a WP4C soil water potential lab instrument (WP4C), pressure plate, and Particle Image Velocimetry (PIV) splitting test system. The results of this study show that with increased water content, the peak splitting load of the samples shows a trend of first increasing and then decreasing, while the peak splitting load and the peak load corresponding to the turning point water content are lower in expansive soils than those in modified soils. Under different water contents, these soils exhibit notable strain softening, and each corresponding load–displacement curve can be divided into linear load increase, tensile failure, and residual stages. According to the displacement vector fields of expansive and modified soil samples, all the fractures are tensile failures. The soil–water characteristic curves of the two types of soil exhibit similar trends. The water content and void ratio of the two soils decrease with increasing suction. This study provides practical guidance for selecting the appropriate water content in canal slope construction.