Abstract: To investigate the influence of temperature and humidity on the mechanical behavior of earth materials, a triaxial apparatus, which can accurately control the temperature and relative humidity of earth materials, was independently developed. Based on the conventional triaxial pressure chamber, a deformation measuring system was set up with the assistance of eddy-current type noncontact deformation sensor, thereby fulfilling the capture of continuous strain variation of earth specimen under the change of environmental condition. A series of cyclic loading-unloading triaxial tests was carried out on the earth material located in Lyon, France, while considering the effects of humidity, confining pressure and temperature. The failure strength, stress-strain curves and the volumetric change were measured through the aforementioned tests, and the Young’s modulus and residual strain under different stress levels were also studied by means of hysteresis loop occurred in the experimental results. Additionally, a vapor migration test of earth material under relative humidity action was also conducted. The results show that the new developed instrument can well control the environmental condition variation and simulate the real working state of earth specimen. The mechanical and environmental indexes are accurately measured, which preliminarily verifies the reliability and accuracy of this apparatus. The relevant research results can provide technical support for understanding the thermal-hydro-mechanical coupling deformation mechanism and constitutive modelling of unsaturated earth materials.

Key words: earth material, temperature and humidity controlling, triaxial tests, cyclic loading-unloading, mechanical behavior