The pressuremeter test in boreholes has proven itself as a useful tool in geotechnical explorations, especially comparing its results with those obtained from a mathematical model ruled by a soil representative constitutive equation. The numerical model shown in this paper is aimed to be the reference framework for the interpretation of this test. The model analyses variables such as: the type of response, the initial state, the drainage regime and the constitutive equations. It is a model of finite elements able to work with a mesh without deformation or one adapted to it.
Model uncertainty is present in many engineering problems but particularly in those involving geotechnical behavior of pile foundation. A wide range of soil conditions together with simplified numerical models makes it a constant necessity to review the accuracy of the predictions. In this paper, the outputs of some seventy (70) pile axially-loaded tests have been reviewed with a classic numerical model to assess pile deformation. Probabilistic approach has been used to quantify uncertainties coming from soil tests, statistic uncertainty and also from the model itself. In this way, a critical review of the prediction method and a way to quantify its uncertainty is presented. The method is intended to be used in a wide range of engineering problems.
An analysis of the geotechnical information obtained from a large number of field tests (pressuremeter) and laboratory tests (identification, state, and mechanics) on the clay deposits in the small tertiary basins associated with the Alentejo-Plasencia fault in the province of Caceres (Spain) has made it possible to classify them and predict their response to different levels of stress and strain. This geotechnical classification process must consider an appropriate model of constitution. The present article is based on the use of the Hardening Soil Model to facilitate predictions of the stress-strain behaviour of these tertiary clay deposits.
Probabilistic approaches to deal with uncertainty on soil mechanic predictions are on the rise. We developed a procedure to deal with uncertainty coming from soil conditions. It was applied to an analytical model to simulate the behavior of a soil improvement work based on rigid inclusion below a slab foundation. The model can predict the settlements of the slab. Even more, it was also able to provide a confidence level based on a probabilistic approach to the input’s variables. Outputs were compared to large-scale tests. The agreement is outstanding. We try to encourage the use of probabilistic models to solve complex geotechnical problems.
Izvleček V članku je opisano geotehnično obnašanje modrih laporjev iz porečja reke Guadalquivir (južna Španija), ki so opredeljeni kot gline z visoko plastičnostjo in se obnašajo kot trdna prekonsolidirana glinasta zemljina. Obravnavani modri laporji so na splošno opredeljeni kot neustrezni material za njihovo ponovno uporabo v različnih zemeljskih delih. V tej študiji smo na podlagi različnih laboratorijskih preiskav preučili primerjavo med geotehničnimi lastnostmi njenega naravnega in zgoščenega pregnetenega stanja z dodatki in brez njih. Izvedle so se številne laboratorijske preiskave, vključno s triosnimi preizkusi v konsolidiranih nedreniranih pogojih. Da bi določili različno obremenitveno-deformacijsko obnašanje, smo v triosnih aparatih preizkusili tri vrste preizkušancev: neporušene in pregnetene preizkušance »in situ« glinastega materiala, kot tudi pregnetene preizkušance gline, pomešane z apnom. Stabilizacija z apnom se pogosto uporablja za izboljšanje geotehničnih lastnosti glinastih tal za uporabo v različnih zemeljskih delih. Za celovito oceno varnosti pobočij, sestavljenih iz teh predelanih materialov, zmešanih z apnom in brez apna, so bile izvedene povratne stabilnostne analize. Rezultati retrospektivne analize takšnih umetnih pobočij omogočajo analizo dejanskih geotehničnih parametrov strižne trdnosti, ki so potrebni pri načrtovanju pobočij ter primerjavo z rezultati triosnih konsolidiranih nedreniranih preizkusov. Izboljšanje parametrov strižne trdnosti v stabilnostni analizi pobočij je bila potrjena za pregnetene pogoje, tako z kot brez dodatka majhne količine apna.NAPETOSTNO DEFOR-MACIJSKI ODZIV MODRIH LAPORJEV IZ POVODJA GUADALQUIVIRJA (ŠPANIJA) Ključne besedeGuadalquivirski modri lapor; sedimentirana glina; triosni preizkus; neporušeni in pregneteni vzorci; stabilizacija z apnom; odziv napetost-deformacija KeywordsGuadalquivir blue marls, sedimentary clay, triaxial test, undisturbed and remolded samples, lime stabilization, stress-strain behavior Abstract This paper describes the geotechnical behavior of the Blue Marls from the Guadalquivir River Basin in Southern Spain, defined as high-plasticity clays that behave as a stiff, over--consolidated clayey soil. These Blue Marls are, in general, classified as an inadequate material for reuse in various earthworks. In this study the comparison between the geotechnical properties of its natural and compacted remolded state, with and without additives, is studied based on different laboratory tests. A great variety of laboratory tests were performed, including triaxial tests under consolidated undrained conditions. Three types of samples were tested in triaxial tests to define different stress-strain behaviors: undisturbed and remolded samples of the in-situ clay material, as well as remolded clay samples mixed with lime. Lime stabilization is frequently used to improve the geotechnical properties of clayey soils for application in different earthworks. The back-analysis of the slope stability is performed for a comprehensive assessment of the condit...
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