Influence of carbonate content on the stress–strength behaviour of neogene marls from the betic cordillera (Spain) in cu triaxial tests using a quasilinear elastic (hyperbolic) model

The stress–strain behaviour of 135 samples of calcareous silt and clay soil, known as marl, from three quarries is presented and discussed in connection with its adjustment to a hyperbolic non-elastic constitutive model. The marl samples were classified and identified, following conventional soil-mechanics procedures and tested under triaxial CU (consolidated undrained) stresses. Also the carbonate, sulphate, and soluble salts contents were analysed by chemical and X-ray methods. Considering the obtained strength parameters and chemical compositions, a high correlation between the carbonate content and the parameters of the hyperbolic model, was observed, indicating a parallel increase in the brittle behaviour, and carbonate content, with a slight increase in bearing capacity. Nevertheless, when all the samples were considered, the parameters of the hyperbolic model seemed not to be clearly related to the carbonate content, this being interpreted as expressing a hyperbolic model influenced not only by the carbonate content but also by several other variables such as the percentage of fine particles or the dilatationing behaviour of the soil particles expressed by the dry density. Given the extensive use of marly soils in the construction of earth dam cores and slope banks, the main interest of the results is to present new insights into its mechanical behaviour not usually considered in common engineering practice.