The dispersion observed in soil data comes both from the spatial variability which greatly influences the behavior of large structures and from errors in testing. Thus, the geotechnical engineering deals with uncertainties for which deterministic approaches are not suitable. The resort to probabilistic techniques, enables modeling uncertainties by analyzing their dispersion effect on the global behavior of the structure. The scope of this paper is analyzing settlement and differential settlement variability of a pair of foundations on random heterogeneous medium. The random soil properties of interest are the elastic modulus, and the Poisson ratio. The elastic modulus is modeled as a spatially random field by adopting the lognormal distribution, which enables analyzing its large variability. Because soil Poisson ratio is bounded in practice between two extreme values, its random field is obtained by using the Beta distribution. In this study, one proposes for the Beta field determination, a mapping technique on the probability distribution function diagram, by solving a non-linear equation. However, the mean and variance are unchanged through the mapping operation. Because the soil Poisson ratio is a positive parameter, one prefers to perform the mapping operation with the probability function of the lognormal distribution. Also, the proposed technique can be used for other bounded soil properties such as the porosity. In this paper, settlement and differential settlement statistics prediction are carried out using Monte Carlo simulations combined with deterministic finite element method (DFEM). A performed parametric study shows the following: (i) as the variability of the elastic modulus increases as settlement and differential settlement statistics are important, also, settlement statistics decreases as the Poisson ratio variability increases, and differential settlement statistics do not seem be affected by its variability. (ii) settlement and differential settlement statistics are important for positive inter-property correlation. (iii) a great influence of the correlation lengths on settlement and differential settlement statistics. 相似文献
Fine-grained, more or less cohesive carbonate materials are extremely widespread in terms of surface area and are, therefore, commonly used as materials to construct impermeable cores for dams. However, it has not been adequately documented whether the carbonate content in fine-grained soils significantly affects their engineering behaviour. The present study shows that the carbonate content substantially influences the engineering behaviour of clayey material. For this, we subjected 32 samples to different laboratory tests, such as the normal Proctor, the Atterberg limits, granulometric analysis, oedometric and undrained triaxial tests. The resulting parameters were correlated with the carbonate content of the samples.
The materials studied in this work had been used in the construction of the impermeable core of the San Clemente Dam, belonging to the hydrographic basin of the Guadalquivir River (southern Spain). These marls present, as their prime characteristic, a carbonate content of the fine fraction consistently exceeding 50%, giving them special importance in the study of this phenomenon.
In this study, a direct relationship was found between the geotechnical properties of the soils studied and their degree of compaction, with the carbonate content and the type of minerals in the clay being the main factors determining the behaviour of these soils. Finally, we conclude that the percentage of carbonates should be used as a classification criterion for the soils used to construct the cores of earth-filled dams. 相似文献
FEBEX is a demonstration and research project, which is being carried out by an international consortium led by the Spanish agency ENRESA and simulates components of the engineering barrier system in accordance with the ENRESA's AGP (Deep Geological Disposal) Granite reference disposal concept. The project includes tests on three scales: an “in situ” test at full scale in natural conditions; a “mock-up” test at almost full scale in controlled conditions; and a series of laboratory test to complement the information from the two large-scale test.The components of the mock-up test are similar to those of the “in situ” test: two electric heaters, a clay barrier consisting of highly compacted bentonite blocks, instrumentation, automatic control of heaters, and a data acquisition system for the data generated. The heterogeneities of the natural system (granite formation) are avoided, the hydration process is controlled with unlimited amount of water at constant pressure, and the boundary conditions are better defined than in the “in situ” test.The operational phase -hydration and heating- started in February 1997. It was initially planned to last for three years, but it has been decided to extend the operational phase to get as close as possible complete saturation of the buffer.Fifty-five months after the start of the operational phase, it can be concluded that the synergy achieved from the simultaneous, integrated performance of tests at different scales, is a valuable approach to establishing the viability of the reference concept, and making progress in the understanding and evaluation of the behaviour in the near field, especially the clay barrier. 相似文献
Polynomial expressions for the elastic tensor coefficients, the bulk, the shear and Young’s moduli, the speed of sound for
longitudinal and transverse waves, the equation of state and the x coordinate of the sulfur atom in pyrite are reported based on ab initio calculations in the range of 0–135 GPa. Comparison
with published experimental data indicates good agreement for the equation of state and for values at 0 GPa as well as reasonable
agreement for first derivatives. All modeling and interpretation was performed with Materials Toolkit v.2.0 and all ab initio
computations with VASP. 相似文献