Analysis Of Soil Stability Problems Such As Reinforced Slopes By Geotechnical Numerical Methods

The soil slope stability is a classic topic of soil mechanics. The limit equilibriummethod is a widely used method in engineering practice for stability analysis andpeople have accumulated abundant and reliable experiences about it. But this stillneeds to be improved and further studied. With the development of our nationalhighway construction, building embankments on soft soil foundation is usuallyencountered. Preloading and geogrid reinforcement are feasible and effective methodsfor weak foundation treatment of embankments. However, the reinforcement theoryof the geogrid is not very clear. The research still lags behind the development ofengineering practice, which limits its application.In this paper, by employing the principle of engineering mechanics and thetheory of limit equilibrium of soil, a general method for slope stability, reinforcedembankment and bearing capacity of the foundation is provided, which theequilibrium of forces and moments, and the yield conditions on the sliding plane willbe reached. And if the sliding surface is a logarithm spiral curved surface, an accurateformula can be obtained. After this, the concept of soil failure within the sliding planeis given and corresponding equations are formulated. The computation of earthpressure on a retaining wall is discussed with the horizontal slice method and acombination plane of plane-logarithm spiral curved surface.Because the limit equilibrium theory makes the assumption that stress-strainrelationship of soil is rigid or rigid-plastic, the deformation of the soil cannot beobtained. Therefore, by employing elastic-plastic finite element method, a geogridreinforced embankment is analyzed in this paper. Mohr-Coulomb model is used tosimulate the soil's stress-strain behavior, and one dimension elastic bar unit to imitatethe geogrid. A contact interface unit is introduced to simulate the interaction betweenthe soil and the reinforcement material. The magnitude of settlement, unevensettlement and stress level in the soil mass are compared with two different cases. Thefirst case is the natural foundation without reinforcement and the other is thereinforced soil with geogrid. And by comparison, the mechanism and significanteffects of geogrid reinforcement are discussed. For example, it can reduce the unevensettlement of the embankment, decrease its deformation and increase its stability. Theinfluence of the modulus of reinforcement material and the friction factor of interfaceon reinforcement effects is analyzed. In addition, treatment of soft soil foundation bygeogrid reinforcement and piles is also studied. Furthermore, by employing thePLAXIS software in combination with Biot's consolidation theory, geogrid reinforcedand plastic board-drained foundation is analyzed. The results show that the geogridreinforcement cooperated by plastic drain boards can quicken the consolidation rate ofsoft soil foundation, increase the shearing strength of soft soil. The research andcorresponding conclusions are useful for the design and the construction of theembankments.