عباس انساني

Access to suitable materials for the construction of reinforced earth structures in some areas may challenge the economic feasibility of the project. In such areas, replacing the common embankment materials with materials containing many fine grains available on site can lead to significant cost savings. In technical literature, these soils are referred to as marginal soil. Providing solutions for the use of this type of material has always been the focus of researchers. Finding suitable reinforcement and correct eva‎luation of shear strength parameters of soil-reinforcement interaction are among these solutions. In this thesis, the effectiveness of geosynthetic reinforcements on the resistance of the interface of soil and reinforcement materials at different moisture content percentages, as well as the analytical and numerical analysis of the behavior of the soil-reinforcement interface has been done. The effect of fine particles in the soil, the type of reinforcement, the presence of sand drainage, the percentage of soil moisture and the overburden pressure imposed on the samples has been studied by conducting 216 large-scale direct shear tests. The tested materials include 3 types of soil including soil containing 5% fine grains (SP-SC), soil containing 20% fine grains (SC), and soil containing 40% fine grains (SC) in contact with 5 types of geosynthetic reinforcements including geogrid, geotextile Non-woven, geocomposite with large opening, geocomposite with small opening and geotextile with a sand drainage layer. Each of the samples has been tested under the overhead pressures of 50, 100 and 150 kPa, at the optimum moisture content, at 2% higher than ωopt, at 4% higher than the ωopt, and also under fully submerged conditions. The permeable geosynthetics in soil with 20% fines produced 0-29% more interface shear strength than the geogrid layer. The amount of this enhancement in soil with 40% fines was 0-100% more than that of the geogrid layer. The shear strength interface parameters dramatically decreased at fully wet condition in comparison with optimum moisture content. In soil with 5% fines in fully wet state، the shear strength of the soil-reinforcement interface increased between 0 and 25% compared to the geogrid. In soil with 20% fines، the increase was between 35% to 60% and in soil with 40% fines، this increase was between 10% and 32%. Based on the experimental results، it was concluded that geosynthetic reinforcement، with high drainage capability، can effectively increase the shear strength parameters of the interface in marginal soils at high moisture content. A hyperbolic theoretical model was proposed to simulate the soil-geosynthetic interface behavior. Moreover، a three-dimensional finite element model of the direct shear test was developed using ABAQUS software. A user-defined subroutine was implemented to consider a hyperbolic elastic perfectly plastic interface constitutive model for the soil-geosynthetic interface simulation. The results indicated a very good agreement between the experimental data and the predicted finite element simulations of the direct shear tests and analytical solutions. Further a numerical simulation of a pullout test was presented in this paper with application of the hyperbolic interface model. The results of this study are of value for future research in advanced numerical modelling of geosynthetic reinforced soil structures with marginal soils.

ژئوسينتتيك , خاك حاوي ريزدانه , اندركنش خاك-ژئوسينتتيك , مدل هايپربوليك , مدلسازي اجزاء محدود

Geosynthetics , marginal soil , Soil-geosynthetic interface , Hyperbolic model , Finite element modelling

abbas ensani

hamid reza razeghi