Study On Stress-Strain Relationship For Soils Reinforced By Geosynthetics

Because reinforcement can improve the tensile strength of soils, many reinforced soil structures had been built since a French engineer Vidal proposed the modern concept of reinforced soil and a lot of experiments and researches had been carried out. Now, reinforced soils have been used widely in road, railway subgrade, slope, retaining wall, bank protection and so on. In order to make use of this structure more widely and more effectively, it is necessary to study the behavior of the reinforced soil under loading.On the base of the review of anteceded research results, lots of triaxial compression tests had been carried out to study the stress-strain relationship of the reinforced soils. Two soils reinforced by five different geosynthetics with three different layers were used in the tests. The finite element numerical simulation for the triaxial compression tests also had been carried out using the commercial software ANSYS.According to the test results, the reinforcement could improve the failure strength for both sand and clay, and the strength increased with the increase of the layer numbers of the reinforcement. However, the extensibility did not always increase with the increase of layer numbers.The reinforcement effect reduced with the increase of confining pressure. There were two failure modes during triaxial compression mainly, one was tensile failure and another was friction failure. When it was tensile failure, the curve of stress-strain relationship was softening and the reinforcement only increased the angle of internal friction of soil. When it was friction failure, the curve of stress-strain relationship was hardening and the reinforcement increased not only the angle of internal friction but also the cohesion of the soil.The results of triaxial compression test indicated that the Duncan-Chang model which is widely applied to sand and clay delete also could be applied to reinforced soil. The stress-strain relationship obtained by the numerical simulation using the Drucker-Prager model and software ANSYS were agree with the test results well, which demonstrated that the Drucker-Prager model could well predict stress-strain behaviour of reinforced soil. The failure sample was like a drum which was similar to the experiment results. The normal stresses on the surface of the reinforcement were maximum at the center, and then decreased gradually along the radial direction, finally increased again. The shear stresses on the surface of the reinforcement increased firstly from the center to surrounding and then decreased.