An apparatus has been developed to carry out two- and three-dimensional tests on interfaces between soils and structural materials. The soil container facilitates both the sliding displacement at the interface and the shear deformation in the soil mass. The apparatus has the capability of maintaining the normal stiffness constant during shearing. In constant normal stiffness tests, the normal stress is adjusted continuously by a computer-controlled system to keep the normal stiffness at a desired value. In addition to constant normal stiffness tests, conventional types of tests can be performed during which the average normal stress acting on the interface is kept constant. In all types of three-dimensional tests, the interface can be subjected to tangential loading in two orhtogonal directions simultaneously. Experiments were conducted to study the two- and three-dimensional behaviour of an interface between a dense sand and a rough steel surface under both constant normal stress and constant normal stiffness conditions. The influence of various stress paths on the stressdisplacement relations and shear strength characteristics of the interface are investigated. The experimental results indicate that the coefficients of friction corresponding to the resultant peak and residual shear strengths are independent of stress paths. The shear stress tangential displacement and volume change behaviour of the interface, however, are significantly influenced by stress paths. Key words: interface testing, simple shear, peak and residual shear strength, three-dimensional, constant normal stiffness, stress path.
Hydrogeochemical investigations had been carried out at the Amol-Babol Plain in the north of Iran. Geochemical processes and factors controlling the groundwater chemistry are identified based on the combination of classic geochemical methods with geographic information system (GIS) and geostatistical techniques. The results of the ionic ratios and Gibbs plots show that water rock interaction mechanisms, followed by cation exchange, and dissolution of carbonate and silicate minerals have influenced the groundwater chemistry in the study area. The hydrogeochemical characteristics of groundwater show a shift from low mineralized Ca-HCO3, Ca-Na-HCO3, and Ca-Cl water types to high mineralized Na-Cl water type. Three classes, namely, C1, C2, and C3, have been classified using cluster analysis. The spatial distribution maps of Na+/Cl−, Mg2+/Ca2+, and Cl−/HCO3
− ratios and electrical conductivity values indicate that the carbonate and weathering of silicate minerals played a significant role in the groundwater chemistry on the southern and western sides of the plain. However, salinization process had increased due to the influence of the evaporation-precipitation process towards the north-eastern side of the study area.
This paper presents numerical modeling verification of a block-faced geogrid-reinforced soil bridge abutment (‘segmental bridge abutment’), subjected to construction-induced loads and seismic loads. The static response of the well-instrumented Founders/Meadow segmental bridge abutment, near Denver, USA, during different stages of construction and in-service behavior, and also the static/seismic response of a carefully instrumented reduced-scale reinforced soil-retaining wall tested on a shaking table at the Royal Military College of Canada (RMC), have been used for numerical modeling verification purposes. A 2-D, explicit dynamic finite difference program was used to perform the analyses, with user-defined static/seismic constitutive models. The comparisons between the predicted results from the numerical models and the measured physical results from instrumented prototypes were judged to show good agreement for vertical and horizontal displacements, reinforcement forces, and vertical/horizontal soil pressures. The lessons learned to model the physical structures were used to investigate the seismic response of the Founders/Meadow segmental bridge abutment.
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