Load-bearing capacity and its relationships with the physical and mechanical attributes of cohesive soil

• Soil moisture and organic carbon were negatively related to the σp.
• Bulk density and penetration resistance were positively related to the σp.
• Bulk density had the largest effect on the variation in the σp.

In north-eastern Brazil, sugarcane is mostly explored in coastal tablelands, where the soil has a particular feature that is called the “cohesive character”. This study aimed to analyse the relationship between physical properties of the soil and the preconsolidation pressure (σp) variation in cohesive soil. The work was performed in the Ultisol area, where sugarcane is cultivated. On a single plot, 42 points were delimited to obtain samples at depths of 0.10–0.13 and 0.30–0.33 m, which resulted in 84 samples in total. Deformed and undeformed samples were collected to measure the following variables: water content, bulk density, soil penetration resistance, organic carbon, clay content, liquid limit, plastic limit, and the σp. For each layer, a principal component analysis was performed. After the scores for those components were obtained, a linear multiple regression model was fitted for the σp data to establish the relationships between the variables. The water content and the organic carbon showed negative relations with σp. The bulk density, soil penetration resistance, clay content, liquid limit and plastic limit were positively related. Higher σp values are associated with higher values of bulk density, soil penetration resistance, clay content, liquid limit and plastic limit, and smaller values are linked to an increase in water content and organic carbon.