Publicação
Continuous monitoring of deformability of stabilized soils based on modalidentification
| Resumo: | Soil stabilization with chemical binders is a technique that aims to improve the mechanical behaviour of soils in order to meet design requirements. In this context, the E-modulus is one of the most important properties for design of structures that involve stabilized soils. There has been a recent proposal of a technique termed as EMM-ARM (Elasticity Modulus Measurement through Ambient Response Method), which allows to continuously monitor the E-modulus evolution of cement-based materials. Such technique relies on placing the sample to be tested in a specific mould, under known support conditions, and apply modal identification techniques to infer the evolution of E-modulus of the tested material during cement hydration. It is remarked that before this PhD work, there had been a set of exploratory experiments using EMM-ARM applied to stabilized soils (made by the author of this thesis), which had pointed to the feasibility of this technique in the context of stabilized soils. This thesis presents a set of subsequent developments of the EMM-ARM technique applied to soils stabilized with binders. The validation of EMM-ARM was made by comparing the results obtained with different testing techniques, such as unconfined cyclic compression testing and techniques based on the propagation of mechanical waves. A sampler was developed to allow the collection of samples from stabilized layers, immediately after compaction, in order to increase the representativeness of the tested samples. The use of alternative materials and geometries of the EMM-ARM test mould, involving polyvinyl chloride (PVC) tubes, aimed the increase of robustness and to simplify its application on sampling operations. A variant approach to EMM-ARM was further proposed, involving modal identification with explicit excitation of small amplitude of the testing beam. This adaptation aimed to increase the robustness of the technique under conditions with contamination of the ambient noise. Moreover, EMMARM was systematically applied to three types of soils stabilized with three different proportions of cement. EMM-ARM was also applied to a soil stabilized with lime for the first time, including curing at distinct temperatures, revealing an interesting Emodulus evolution with two phases and allowing to estimate apparent activation energies of the reactions involved. The final part of the thesis presents a methodology based on Bayesian inference to predict the E-modulus results at the reference age of 28 days, using the results obtained during the first 2 to 7 days of age. |
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| Autores principais: | Silva, Jacinto João Rosário |
| Ano: | 2017 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Soil stabilization with chemical binders is a technique that aims to improve the mechanical behaviour of soils in order to meet design requirements. In this context, the E-modulus is one of the most important properties for design of structures that involve stabilized soils. There has been a recent proposal of a technique termed as EMM-ARM (Elasticity Modulus Measurement through Ambient Response Method), which allows to continuously monitor the E-modulus evolution of cement-based materials. Such technique relies on placing the sample to be tested in a specific mould, under known support conditions, and apply modal identification techniques to infer the evolution of E-modulus of the tested material during cement hydration. It is remarked that before this PhD work, there had been a set of exploratory experiments using EMM-ARM applied to stabilized soils (made by the author of this thesis), which had pointed to the feasibility of this technique in the context of stabilized soils. This thesis presents a set of subsequent developments of the EMM-ARM technique applied to soils stabilized with binders. The validation of EMM-ARM was made by comparing the results obtained with different testing techniques, such as unconfined cyclic compression testing and techniques based on the propagation of mechanical waves. A sampler was developed to allow the collection of samples from stabilized layers, immediately after compaction, in order to increase the representativeness of the tested samples. The use of alternative materials and geometries of the EMM-ARM test mould, involving polyvinyl chloride (PVC) tubes, aimed the increase of robustness and to simplify its application on sampling operations. A variant approach to EMM-ARM was further proposed, involving modal identification with explicit excitation of small amplitude of the testing beam. This adaptation aimed to increase the robustness of the technique under conditions with contamination of the ambient noise. Moreover, EMMARM was systematically applied to three types of soils stabilized with three different proportions of cement. EMM-ARM was also applied to a soil stabilized with lime for the first time, including curing at distinct temperatures, revealing an interesting Emodulus evolution with two phases and allowing to estimate apparent activation energies of the reactions involved. The final part of the thesis presents a methodology based on Bayesian inference to predict the E-modulus results at the reference age of 28 days, using the results obtained during the first 2 to 7 days of age. |
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