Roberto Francisco de Azevedo

Validation of Coupled Simulation of Excavations in Saturated Clay: Camboinhas Case History

This paper presents the results of an elastoplastic finite-element back analysis of an excavation made on a saturated soft organic clay deposit in Rio de Janeiro, Brazil. The excavation was conducted as part of an urbanization program, in which artificial islands were to be created in a swamp along the margins of the Camboinhas Lagoon. An extensive laboratory testing program was performed on undisturbed soil samples to characterize the stress-strain-strength behavior of the involved materials. Results from this laboratory testing program were used to calibrate a nonassociated elastoplastic constitutive model implemented in the ANLOG (Nonlinear Analysis of Geotechnical Problems) code. This code is based on the finite-element method and is capable of conducting fully coupled analyses by using a variety of constitutive models. Coupled analyses were performed to simulate the Camboinhas excavation, which was conducted under plane strain condition. Field mea- surements of both displacements and pore-water pressures obtained during the excavation are compared with the results of the numerical simulation. Analyses of the results show that monitored in situ and numerical results are in good agreement. DOI: 10.1061/(ASCE)GM .1943-5622.0000077.

Determinação de parâmetros de transporte de metais pesados em Latossolo compactado

In this work, values of hydrodynamic dispersion coefficient and retardation factor, for zinc, manganese and cadmium in a mature Oxisol (horizon B) determined through the traditional and the cumulative mass approaches of column tests are compared. A computer program, which uses an optimization procedure, was developed to facilitate the interpretation of the results obtained from cumulative mass approach. The transport parameter values obtained in this work were not affected by the determination methodology employed, even when a reduced number of effluent samples were used for the cumulative mass approach. The use of the cumulative mass method, based on a reduced number of pore volumes, in the determination of transport parameters, reduces time and costs involved in tests.

Influence of laboratory techniques on the geotechnical characterization of mining and industrial wastes

The design of fine-grained tailing reservoirs requires the determination of their physical, mechanical and hydraulic characteristics to predict both the reservoir filling operation and its reclamation. Once these characteristics are properly determined, moderately realistic tailings behavior prediction, such as its self-weight consolidation, can be obtained from numerical analysis. However, if a simple grain size analysis is not adequately carried out, one can find substantially large discrepancies between the analytical predictions and the actual field behavior. This paper presents results of an extensive laboratory program executed to obtain geotechnical parameters of mining and industrial wastes. Different residues from mining and industrial processing of bauxite were studied. The results of geotechnical characterization tests carried out on all materials are presented and compared. The effects of the testing technique utilized on the geotechnical characterization results are discussed. It is shown that the prediction of the sedimentation/consolidation behavior of these tailings when discharged as slurry using parameters obtained from characterization tests must be done with care.