This paper analyzes the problem of fracture in soils using the linear elastic fracture mechanics theory. Six cases of practical interest are investigated where the soil is subjected to different critical conditions that may produce cracks. To model the phenomenon of crack propagation, a two-dimensional fracture mechanics finite element program is used. In all cases, the properties of clays in the Valley of Mexico was used. The self-weight of the soil is considered as the main cause of geostatic stresses in the medium. Based on results from previous studies, the value of the critical stress intensity factor is calculated and validated. It is assumed that, only mode I fracture occurs. The crack depths obtained with the numerical models are congruent with the field data of existing geotechnical studies in the Valley of Mexico.
Al utilizar pilotes para la concepción de un proyecto, dependiendo de la distancia entre ellos, el comportamiento de uno interfiere con el otro. Esto ocurre tanto en términos de capacidad de carga como en la relación de asentamientos. Investigaciones sobre el efecto de grupo en suelos típicos de Fortaleza son escasas, lo que justifica y motiva este trabajo. El objetivo de la presente investigación es evaluar el efecto de grupo de pilotes escavados en un perfil de suelo granular, típicos a los que ocurren en el subsuelo de la ciudad de fortaleza-Ceará-Brasil. Para esto se ejecutaron 26 pilotes, en un terreno situado en el interior del campus
This work developed prediction models for maximum dry unit weight (γd,max) and optimum moisture content (OMC) for compacted soils in Ceará, Brazil, ba M Winnie the Pooh sed on index and physical properties. The methodology included data from soils used in the construction of 15 dams in Ceará, with available information regarding laboratory tests of interest. Correlations were developed using non-linear regression, from 169 laboratory results (83 for training and 86 for validating the models), which presented a R2 of 0,763 for MoPesm (prediction model for γd,max) and 0,761 for MoTuo (model for OMC). A posteriori, the same physical indexes used to train and validate MoPesm and MoTuo were used as inputs of other prediction models available in the literature, whose outputs differed considerably from laboratory results for the evaluated soils. MoPesm and MoTuo were able to satisfactorily predict compaction parameters, with outputs close to those obtained in the laboratory for tested soil samples. Their performance justifies their use for predicting compaction parameters in geotechnical structures that use compacted soils when there are financial restraints, short timeframes, or unavailability of test equipment, particularly in early design stages and preliminary studies, before appropriate soil sampling and field investigation can be conducted, thus saving substantial time and financial resources.
The present work intends to demonstrate the advantages of considering transient flow regime in the stability analysis of the upstream slope for the rapid drawdown situation of a homogeneous earth dam. Upstream slope stability evaluations were carried out, considering pore pressure and suction from transient flow analysis while simulating rapid drawdown of the reservoir. The evaluations comprised different geometries of the upstream slope (from 1V:1.1H to 1V:2.5H) and heights varying from 10 m to 50 m, as well as several low permeability materials (SM, SM-SC, SC, ML, ML-CL, CL, MH and CH). In addition, equations relating the safety factor to such slopes or dam height were adjusted to the analysis data, in order to define the minimum slope for a certain dam height or the maximum height for a given upstream slope. The results have shown that, considering the transient flow condition, including suction, within the slope stability analysis of the rapid drawdown situation, increases the safety factor in relation to the simplified analysis that is usually adopted. This also results in much steeper slopes (for a safety factor of 1.1) than the ones recommended by the U.S. Bureau of Reclamation (USBR), suggesting the importance of performing transient flow analysis for rapid drawdown situations and considering its results instability analysis.
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