Deformation prediction of geosynthetic reinforced soil retaining walls

Abstract

A program to investigate the behavior of geosynthetic reinforced soil and the deformation of geosynthetic reinforced soil retaining walls is presented. This investigation included laboratory testing of geosynthetic reinforcements and geosynthetic reinforced cohesionless soils, and finite element analysis of reinforced soil retaining walls.Two sands, two polypropylene nonwoven needle-punched geotextiles, three polypropylene woven slit-film geotextiles, and a multi-filament polyester woven geotextile were the focus of the testing program. In-soil testing of the geotextiles was performed using a plane strain unit cell device. Tension induced in the reinforcement during loading of reinforced soil specimens increased the confining pressure acting on the soil, which permitted the soil to support a greater load than it could when unreinforced. Soil dilation played an important role in defining the stress-strain behavior of the reinforced soil composite. Higher modulus reinforcements were able to restrict soil dilation.The woven geotextiles experienced creep and stress relaxation at low strains and over short time periods in tests conducted in the unit cell device. To further study these mechanisms, a series of in-isolation wide width tests, conducted at various strain rates, as well as short term creep tests on the woven geotextiles were performed. In-isolation wide width tests on the nonwoven geotextiles were conducted because the changing normal pressure conditions which occurred in unit cell device tests complicated determination of the in-soil modulus for these reinforcements. The in-isolation tests determined that the strength and modulus of the woven geotextiles decreased with decreasing strain rate and that the modulus of the nonwoven geotextiles increased with decreasing specimen gage length.The deformation of geosynthetic reinforced soil retaining walls was investigated using the finite element method. Assuming linear elastic material properties, the influence of wall geometry, applied loads, and boundary conditions were investigated. It was determined that these factors played a major role in defining the pattern of deformation and reinforcing strains observed in reinforced soil retaining walls.The findings of the laboratory tests and finite element analysis were applied to the Rainier Avenue wall. Conclusions reached from earlier investigations of this wall were evaluated. Recommendations for determining soil and geosynthetic properties and using them for predicting reinforced soil retaining wall deformations were also made. The finite element method was determined to be the best means for accurately predicting deformations of individual reinforced soil walls.