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No description available.

A major instrumented geosynthetic reinforced approach embankment was constructed to 5.5 m elevation above ground, with prefabricated vertical drains, over a soft compressible clay deposit at Leneghan, Newcastle, Australia in May 1995. The field monitoring of settlements for over six years shows that the embankment manifests significant creep. The instrumentation, field performance and the finite element analyses for predicting the long-term performance of this embankment are described in this thesis. The maximum settlement of 1.1 m was observed one year after the completion of construction. However, the embankment continued to settle at a rate of 0.4 mm/day for the next 5 years. The horizontal displacements of 0.09-0.14 m at various locations and the maximum reinforcement strains of 0.67% were recorded. A numerical model was developed to perform a fully coupled large deformation elasto-viscoplastic finite element analysis for this performance prediction based on creep model proposed by Kutter and Sathialingam (1992). The foundation soil was modelled with creep material behaviour using six noded linear strain triangular elements. A well-documented case history ??? Sackville embankment, New Brunswick, Canada was analysed using this model as a benchmark problem and the model was found to predict all the behaviour characteristics reasonably well. The results obtained from finite element analysis using this model are shown to be in reasonable agreement with the observed performance of Leneghans embankment in terms of settlements, horizontal displacements, excess pore pressures and geosynthetic strains. But, the prediction of settlements was less than satisfactory beyond April 1999. Finite element analyses were performed to study the sensitivity of this embankment behaviour on the variation of hydraulic conductivity values and geosynthetic reinforcement properties. This sensitivity study indicated that the kv variation, the kh/kv ratio and the nominal values of geosynthetic properties adopted in the benchmark analysis are reasonable enough for the long-term behaviour prediction.

Sn-Pb solder has long been used in the Electronics industry. But, due to its toxic nature and environmental effects, certain restrictions are made on its use and therefore many researchers are looking to replace it. Sn-3.0Ag-0.5Cu (SAC) solders are suggested as lead-free replacements but their coarse microstructure and formation of hard and brittle Inter-Metallic Compounds (IMCs) like Ag₃Sn and Cu₆Sn₅ have limited their use in high temperature applications. In this research work, RE elements, mostly lanthanum (La), are used as potential additives to SAC alloys. They reduce the surface free energy, refine the grain size and improve the mechanical and wetting properties of SAC alloys. An extensive experimental work has been performed on the microstructure evolution, bulk mechanical properties, individual phase (matrix and IMCs) mechanical properties, creep behavior and wettability performance of the SAC and SAC-La alloys, with different (La) doping. SEM and EDS have been used to follow the continuous growth of the IMCs at 150°C and 200°C and thus provide a quantitative measure in terms of their size, spacing and volume fraction. Grain size is measured at regular intervals starting from 10 hours up to 200 hours of thermal aging using Optical Microscope with cross polarized light. Bulk mechanical properties are evaluated using tensile tests at low strain rates. Individual phase mechanical properties like Young's modulus, hardness, strain rate sensitivity index and bulge effects are characterized with nanoindentation from 100 µN up to 5000 µN loadings at different temperatures of 25°C, 45°C, 65°C and 85°C. Creep experiments are performed at elevated temperatures with good fitting of Dorn creep and back-stress creep models. Activation energy measurements are made at 40°C, 80°C and 120°C. Wettability testing on copper substrates is used for surface tension, wetting force and contact angle measurements of SAC and SAC-La doped alloys at 250°C and 260°C.

A major instrumented geosynthetic reinforced approach embankment was constructed to 5.5 m elevation above ground, with prefabricated vertical drains, over a soft compressible clay deposit at Leneghan, Newcastle, Australia in May 1995. The field monitoring of settlements for over six years shows that the embankment manifests significant creep. The instrumentation, field performance and the finite element analyses for predicting the long-term performance of this embankment are described in this thesis. The maximum settlement of 1.1 m was observed one year after the completion of construction. However, the embankment continued to settle at a rate of 0.4 mm/day for the next 5 years. The horizontal displacements of 0.09-0.14 m at various locations and the maximum reinforcement strains of 0.67% were recorded. A numerical model was developed to perform a fully coupled large deformation elasto-viscoplastic finite element analysis for this performance prediction based on creep model proposed by Kutter and Sathialingam (1992). The foundation soil was modelled with creep material behaviour using six noded linear strain triangular elements. A well-documented case history ??? Sackville embankment, New Brunswick, Canada was analysed using this model as a benchmark problem and the model was found to predict all the behaviour characteristics reasonably well. The results obtained from finite element analysis using this model are shown to be in reasonable agreement with the observed performance of Leneghans embankment in terms of settlements, horizontal displacements, excess pore pressures and geosynthetic strains. But, the prediction of settlements was less than satisfactory beyond April 1999. Finite element analyses were performed to study the sensitivity of this embankment behaviour on the variation of hydraulic conductivity values and geosynthetic reinforcement properties. This sensitivity study indicated that the kv variation, the kh/kv ratio and the nominal values of geosynthetic properties adopted in the benchmark analysis are reasonable enough for the long-term behaviour prediction.