عنوان مقاله [English]
Sand-bentonite mixtures are usually utilized as liners for municipal waste disposal facilities. These widespread liners are constructed in thin layers and, therefore, indicate an oedometric behavior. Experimental study of the t-rest ateral pressure of these soils is an important step in understanding the hydro-mechanical ehavior f he bovementioned barriers. Despite the huge amount of research on the oedometric volume change of expansive clay, little work has been done to date on the K0-coefficient of these soils, and the effect of hydraulic loading on their mechanical behavior has been rarely studied.In this paper, a novel oedometer is introduced to determine the coefficient of the lateral pressure of soil. The almost rigid ring of the modified apparatus has three circular diaphragms, with a diameter of 15mm and a thickness of 0.35mm. Three LVDTs are installed in contact with these diaphragms to measure the horizontal deformation of the thin diaphragms induced by the horizontal pressures. The diaphragms are calibrated using the water hydrostatic pressure, and pressure and deformations are correlated. Adopting the osmotic method to impose the matric suction, the modified oedometer apparatus accommodates the circulation of the PEG solution beneath the soil sample. A semi permeable membrane is introduced between the sample and the PEG solution to prevent the PEG macromolecules from passing towards the sample.Twenty five percent of the studied material is composed of bentonite and the rest of the soil is well graded sand. The coefficient of the at-rest lateral pressure of the material is determined at various stress states, and the influence of hydraulic loading on the lateral pressure of the soil is discussed in detail. A single effective stress approach is employed to determine the at-rest lateral pressure of the soil particles. The outcomes indicate that the K0-parameter decreases significantly with suction increase. Furthermore, drying-wetting cycles harden the soil, reducing the amount of compressibility indices and the K0-parameter of the material.