Etude expérimentale sur l`impact du diamètre moyen sur la résistance au cisaillement des mélanges sables-granules de caoutchouc

Abstract

The stability of granular soils, crucial in geotechnical engineering, can be significantly improved by the addition of recycled materials, particularly rubber granules. However, combined effects of the average sand particle diameter (D₅₀) and rubber content on the mechanical behavior of these mixtures remain poorly explored. This experimental study aims to evaluate the influence of these two parameters on the shear strength of sand–rubber mixtures, using direct shear tests with the Casagrande box. Three sand particle sizes (D₅₀ = 1 mm, 2 mm and 3.15 mm) were mixed with five proportions of recycled rubber granules (0%, 2.5%, 5%, 7.5% and 10%), then subjected to three levels of normal stress (100, 200 and 400 kPa) at a high relative density (Dr = 90%). The results reveal that increasing the average sand grain diameter significantly improves the maximum shear strength, the angle of internal friction as well as the dilatancy, with a particularly marked effect under low normal stress. At the same time, the incorporation of rubber granules strongly influences the mechanical behavior of the mixtures, with a maximum improvement in strength observed for an optimal content of 5%, beyond which a decrease is observed. An exponential relationship was identified between the friction angle and the average diameter, while the beneficial effect of granules was more pronounced under normal stress (200 kPa). These results confirm on the combined role of grading and rubber addition in strengthening granular soils and open up promising prospects for their use in soil improvement in sustainable civil engineering projects