Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de e... more Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de escavação em rocha. O modelo proposto foi desenvolvido recorrendo a cadeias de Markov, em particular a uma abordagem Markoviana sem memória. O modelo parte de um índice de qualidade que é atribuído ao talude em fase de exploração, o qual varia entre 1 e 5, e prevê a sua evolução ao longo do tempo. O modelo proposto caracteriza-se pela não necessidade do conhecimento do historial do talude, permitindo, assim, estimar o estado de condição de um dado talude ao longo do tempo, conhecendo apenas o seu estado atual. Esta característica representa uma mais-valia nas atuais condições de historial disponível sobre o estado de condição de taludes ao longo do tempo. De facto, o modelo proposto foi desenvolvido sobre uma base de dados sintética, a qual procurou refletir o mais fielmente possível a realidade. Os resultados obtidos, os quais representam a primeira iteração no desenvolvimento de um modelo de previsão do estado de condição de taludes durante a sua fase de exploração, mostram que será possível modelar o processo de degradação de taludes de escavação em rocha com relativa fiabilidade utilizando uma abordagem Markoviana.
ABSTRACT This paper assesses the adhesion capacity of unmodified mud grouts used to repair struct... more ABSTRACT This paper assesses the adhesion capacity of unmodified mud grouts used to repair structural cracks on medium and large scale rammed earth specimens. Beam and wallet-specimens were manufactured using a soil from Alentejo (Portugal), whose particle size distribution had to be first corrected due to its high clay content. An “artificial” (composed by kaolin and limestone powder) and a “natural” (composed by sieved soil and limestone powder) mud grout were used to repair the specimens, which were previously tested under three-point bending and diagonal-compression and then retested. The grout injection shown to provide satisfactory results regarding the adhesion capacity, but only if it is performed with the “natural” mud grout.
The rehabilitation and repair of existing structures requires inspection. This generally includes... more The rehabilitation and repair of existing structures requires inspection. This generally includes in situ non-destructive testing. A very economical test is the non-destructive ultrasonic pulse velocity test (UPV). Lower information is available in the literature in relation to the use of this technique for the estimation of the tensile strength of materials. Therefore, this paper aims at using artificial neural networks (ANN) in the prediction of the mechanical behaviour of granites under tensile loading. The parameters under analysis are the tensile strength, displacement at peak stress and critical crack opening. For this, experimental results obtained from the physical and mechanical characterization under tension of distinct types of granites are combined and the performance of the developed models using the UPV index alone and combined with other physical parameters is analysed. The results of the ANN models are also compared with respect to the results of regression models. The criteria used to evaluate the predictive performances of the models were the coefficient of correlation (R) and root mean square error (RMSE).
This paper addresses the performance analysis of an optimization algorithm from the field of evol... more This paper addresses the performance analysis of an optimization algorithm from the field of evolutionary computation, namely an Evolution Strategy, in back analysis to evaluate the geomechanical parameters of the formation surrounding an underground structure. The algorithm is first tested using a synthetic case of a tunnel excavation. In this case, different scenarios are considered through a parametric study. Then the algorithm is tested using real data from the excavation of an underground structure built in the North of Portugal using a 3D model. The results show that the Evolution Strategy algorithm is robust in the identification of geomechanical parameters related to underground engineering.
Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de e... more Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de escavação em rocha. O modelo proposto foi desenvolvido recorrendo a cadeias de Markov, em particular a uma abordagem Markoviana sem memória. O modelo parte de um índice de qualidade que é atribuído ao talude em fase de exploração, o qual varia entre 1 e 5, e prevê a sua evolução ao longo do tempo. O modelo proposto caracteriza-se pela não necessidade do conhecimento do historial do talude, permitindo, assim, estimar o estado de condição de um dado talude ao longo do tempo, conhecendo apenas o seu estado atual. Esta característica representa uma mais-valia nas atuais condições de historial disponível sobre o estado de condição de taludes ao longo do tempo. De facto, o modelo proposto foi desenvolvido sobre uma base de dados sintética, a qual procurou refletir o mais fielmente possível a realidade. Os resultados obtidos, os quais representam a primeira iteração no desenvolvimento de um modelo de previsão do estado de condição de taludes durante a sua fase de exploração, mostram que será possível modelar o processo de degradação de taludes de escavação em rocha com relativa fiabilidade utilizando uma abordagem Markoviana.
ABSTRACT The construction of masonry with compressed earth blocks (CEBs) is a modern earth constr... more ABSTRACT The construction of masonry with compressed earth blocks (CEBs) is a modern earth construction technique with current growing interest, but its environmental sustainability is many times depreciated by the use of traditional chemical stabilisation techniques (lime and cement addition). This paper presents an experimental program where the possibility of manufacturing CEBs using granitic residual soils (GRS) from northern Portugal is addressed. The GRS were shown to be inadequate and their use for manufacturing CEBs requires chemical stabilisation. A composition study involving stabilisation by addition of cement and addition of geopolymeric binders resulting from the alkaline activation of fly ash or of calcinated sludge was carried out. Then, CEBs stabilised with alkaline activation of fly ash were manufactured and their mechanical properties were tested. In addition, the compressive behaviour of masonry built with these CEBs was also characterized. In general, the stabilisation with alkaline activation of fly ash revealed excellent results with respect to the improvement in strength.
O presente artigo aborda uma aplicação do método observacional na engenharia de túneis para a ada... more O presente artigo aborda uma aplicação do método observacional na engenharia de túneis para a adaptação em tempo real do método de escavação e suporte. O método observacional é utilizado há muitos anos, no entanto não existe uma metodologia consistente e estruturada para a incorporação dos dados da monitorização na adaptação do sistema de suporte em tempo real. A metodologia proposta possibilitará a otimização do sistema de suporte e do custo total da obra, tal como um aumento da segurança nos trabalhos de escavação.
Vibrations in rock masses can be a significant hazard, leading to human discomfort and structural... more Vibrations in rock masses can be a significant hazard, leading to human discomfort and structural damage. Recent cases of subway or tunnel excavation near existing dams in Portugal have raised again the importance of this topic. Traditional statistical tools have been used to study wave propagation in rock, but fall short when rock fracturing or faulting radically changes the way vibration propagates. Numerical models such as finite-element or finite-difference models also have some insufficiencies, namely in the way discontinuities are represented. We propose the utilization of bonded particle models based on the Particle Discrete Element Method. Synthetic rock samples are generated and their static elastic properties are calibrated by manipulating microproperties (assembly organization and normal and shear contact stiffness). The static and dynamic properties of the rock cores are tested and the complete elastic response of the model is evaluated and discussed.
Southern Portugal presents a rich heritage constituted by several constructions made from unstabi... more Southern Portugal presents a rich heritage constituted by several constructions made from unstabilised rammed earth (URE), which are threatened by several factors, ranging from lack of conservation to a non-negligible seismic hazard. These threatens are enhanced by the fact that little is known about the shear behaviour of URE constructions. The preservation of this heritage requires definitely the development of this knowledge and, in addition, the development of adequate intervention solutions. This paper presents an experimental program where the shear behaviour of URE is assessed by means of diagonal compression tests on representative wallet-specimens. Furthermore, the use of mud grouts in repairing cracks was also assessed. The results showed that the shear behaviour of URE depends on the binding capacity promoted by the clay fraction and on the friction and interlocking promoted by the coarse aggregates. The repair by injection was shown to promote satisfactory shear strength recovery of the specimens, but was less effective in recovering the initial shear stiffness.
Como material de construção não normalizado, a terra é ainda associada à construção de subsistênc... more Como material de construção não normalizado, a terra é ainda associada à construção de subsistência dos países em desenvolvimento. Porém, as vantagens da construção em terra têm sido cada vez mais reconhecidas, nomeadamente a sua sustentabilidade. Esta mudança de paradigma tem levado ao desenvolvimento de técnicas modernas de construção em terra, particularmente a alvenaria de blocos de terra comprimida (BTC). A estabilização química tradicional do solo é um processo de melhoramento frequentemente utilizado, mas que também aumenta significativamente a energia incorporada dos BTC. Este artigo apresenta uma solução de estabilização alternativa para BTC, baseada na ativação alcalina de cinza volante. O comportamento mecânico dos BTC e da respetiva alvenaria de junta seca é estudado através de um programa experimental, que inclui a caraterização do comportamento ao corte da alvenaria.
The aim of this work is to use Data Mining tools to develop models for the prediction of hard roc... more The aim of this work is to use Data Mining tools to develop models for the prediction of hard rock tunnel boring machine (TBM) penetration rate (ROP). A database published by was used to develop these models. The parameters of the database were the uniaxial compressive strength (UCS), an index used to quantify the brittleness and toughness and denominated peak slope index (PSI), the distance between the planes of weakness (DPW), the angle between tunnel axis and the planes of weakness (α) and the output parameter rate of penetration (ROP). The R program environment was used as a modeling tool to apply the artificial neural networks (ANN) and the support vector machine (SVM) algorithms and the corresponding models. These models were compared with two equations presented by Yagiz and . It was concluded that the ANN model has the best performance. Moreover, these new models allowed computing the importance of the different input parameters for predicting machine performance. It was concluded that PSI is the most important parameter and UCS is the less important parameter.
In this paper, a study is performed to evaluate the main advantages and limitations of different ... more In this paper, a study is performed to evaluate the main advantages and limitations of different types of optimization algorithms for the identification of geomechanical parameters in underground structures. The main goal was to evaluate their main differences in terms of robustness and efficiency in diverse circumstances. Two different types of algorithms were tested: i) classical algorithms which use the gradient of the error function to guide the search, namely the steepest descent, conjugate gradient and quasi-Newton; and ii) an innovative evolutionary algorithm, from the artificial intelligence field, called evolution strategy. The first was coupled with a 3D model of a tunnel while for the latter analytical solutions were used for a much higher number of calculations and tests were expected to perform due to its nature. The algorithms were tested in both elasticity and elasto-plasticity using the Mohr-Coulomb constitutive model. In elasticity both types of algorithms showed a good performance but in elasto-plasticity the classical algorithms revealed a poor behaviour mainly in terms of robustness, failing to converge in several situations. It was found that in many situations these limitations were avoided by the innovative algorithm presented in this work showing an interesting potential for future developments.
A alargada rede de infraestruturas viárias existente atualmente em Portugal, tem contribuído para... more A alargada rede de infraestruturas viárias existente atualmente em Portugal, tem contribuído para uma crescente melhoria nas condições de mobilidade. De todas as componentes constituintes da rede, os taludes são os que apresentam um défice maior em termos de sistemas de avaliação de qualidade.
... JORNADAS LUSO-ESPANHOLAS SOBRE OBRAS SUBTERRÂNEAS, Madrid, 2003 – “Jornadas Luso-Espanholas s... more ... JORNADAS LUSO-ESPANHOLAS SOBRE OBRAS SUBTERRÂNEAS, Madrid, 2003 – “Jornadas Luso-Espanholas sobre nas obras subterraneas : relevancia da prospecção e da observação geotecnicas e primeira lição internacional Jiménez Salas.” [Madrid] : CEDEX, 2003. ...
In this paper a KBS computational system, designated by GEOPAT, for the calculation of geomechani... more In this paper a KBS computational system, designated by GEOPAT, for the calculation of geomechanical parameters for modelling underground structures in rock and soil formations is presented. To congregate the specialists' knowledge in rock and soil domains, and in particular in the tunnel engineering, causal nets have been established for decision support. GEOPAT determines the parameters for rock and soil formations, as well as heterogeneous rock formations. The developed GEOPAT system was applied to a large underground station in urban environment, excavated in granite formations, in order to obtain the deformability and strength parameters of the surrounding rock masses. Numerical models were developed considering either the obtained geomechanical parameters using artificial intelligence techniques or the parameters used in design. The numerical results obtained with the two sets of parameters are compared, as well as with the monitoring results. Some conclusions are drawn.
Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de e... more Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de escavação em rocha. O modelo proposto foi desenvolvido recorrendo a cadeias de Markov, em particular a uma abordagem Markoviana sem memória. O modelo parte de um índice de qualidade que é atribuído ao talude em fase de exploração, o qual varia entre 1 e 5, e prevê a sua evolução ao longo do tempo. O modelo proposto caracteriza-se pela não necessidade do conhecimento do historial do talude, permitindo, assim, estimar o estado de condição de um dado talude ao longo do tempo, conhecendo apenas o seu estado atual. Esta característica representa uma mais-valia nas atuais condições de historial disponível sobre o estado de condição de taludes ao longo do tempo. De facto, o modelo proposto foi desenvolvido sobre uma base de dados sintética, a qual procurou refletir o mais fielmente possível a realidade. Os resultados obtidos, os quais representam a primeira iteração no desenvolvimento de um modelo de previsão do estado de condição de taludes durante a sua fase de exploração, mostram que será possível modelar o processo de degradação de taludes de escavação em rocha com relativa fiabilidade utilizando uma abordagem Markoviana.
ABSTRACT This paper assesses the adhesion capacity of unmodified mud grouts used to repair struct... more ABSTRACT This paper assesses the adhesion capacity of unmodified mud grouts used to repair structural cracks on medium and large scale rammed earth specimens. Beam and wallet-specimens were manufactured using a soil from Alentejo (Portugal), whose particle size distribution had to be first corrected due to its high clay content. An “artificial” (composed by kaolin and limestone powder) and a “natural” (composed by sieved soil and limestone powder) mud grout were used to repair the specimens, which were previously tested under three-point bending and diagonal-compression and then retested. The grout injection shown to provide satisfactory results regarding the adhesion capacity, but only if it is performed with the “natural” mud grout.
The rehabilitation and repair of existing structures requires inspection. This generally includes... more The rehabilitation and repair of existing structures requires inspection. This generally includes in situ non-destructive testing. A very economical test is the non-destructive ultrasonic pulse velocity test (UPV). Lower information is available in the literature in relation to the use of this technique for the estimation of the tensile strength of materials. Therefore, this paper aims at using artificial neural networks (ANN) in the prediction of the mechanical behaviour of granites under tensile loading. The parameters under analysis are the tensile strength, displacement at peak stress and critical crack opening. For this, experimental results obtained from the physical and mechanical characterization under tension of distinct types of granites are combined and the performance of the developed models using the UPV index alone and combined with other physical parameters is analysed. The results of the ANN models are also compared with respect to the results of regression models. The criteria used to evaluate the predictive performances of the models were the coefficient of correlation (R) and root mean square error (RMSE).
This paper addresses the performance analysis of an optimization algorithm from the field of evol... more This paper addresses the performance analysis of an optimization algorithm from the field of evolutionary computation, namely an Evolution Strategy, in back analysis to evaluate the geomechanical parameters of the formation surrounding an underground structure. The algorithm is first tested using a synthetic case of a tunnel excavation. In this case, different scenarios are considered through a parametric study. Then the algorithm is tested using real data from the excavation of an underground structure built in the North of Portugal using a 3D model. The results show that the Evolution Strategy algorithm is robust in the identification of geomechanical parameters related to underground engineering.
Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de e... more Neste trabalho é apresentada uma proposta de modelo para a previsão da degradação de taludes de escavação em rocha. O modelo proposto foi desenvolvido recorrendo a cadeias de Markov, em particular a uma abordagem Markoviana sem memória. O modelo parte de um índice de qualidade que é atribuído ao talude em fase de exploração, o qual varia entre 1 e 5, e prevê a sua evolução ao longo do tempo. O modelo proposto caracteriza-se pela não necessidade do conhecimento do historial do talude, permitindo, assim, estimar o estado de condição de um dado talude ao longo do tempo, conhecendo apenas o seu estado atual. Esta característica representa uma mais-valia nas atuais condições de historial disponível sobre o estado de condição de taludes ao longo do tempo. De facto, o modelo proposto foi desenvolvido sobre uma base de dados sintética, a qual procurou refletir o mais fielmente possível a realidade. Os resultados obtidos, os quais representam a primeira iteração no desenvolvimento de um modelo de previsão do estado de condição de taludes durante a sua fase de exploração, mostram que será possível modelar o processo de degradação de taludes de escavação em rocha com relativa fiabilidade utilizando uma abordagem Markoviana.
ABSTRACT The construction of masonry with compressed earth blocks (CEBs) is a modern earth constr... more ABSTRACT The construction of masonry with compressed earth blocks (CEBs) is a modern earth construction technique with current growing interest, but its environmental sustainability is many times depreciated by the use of traditional chemical stabilisation techniques (lime and cement addition). This paper presents an experimental program where the possibility of manufacturing CEBs using granitic residual soils (GRS) from northern Portugal is addressed. The GRS were shown to be inadequate and their use for manufacturing CEBs requires chemical stabilisation. A composition study involving stabilisation by addition of cement and addition of geopolymeric binders resulting from the alkaline activation of fly ash or of calcinated sludge was carried out. Then, CEBs stabilised with alkaline activation of fly ash were manufactured and their mechanical properties were tested. In addition, the compressive behaviour of masonry built with these CEBs was also characterized. In general, the stabilisation with alkaline activation of fly ash revealed excellent results with respect to the improvement in strength.
O presente artigo aborda uma aplicação do método observacional na engenharia de túneis para a ada... more O presente artigo aborda uma aplicação do método observacional na engenharia de túneis para a adaptação em tempo real do método de escavação e suporte. O método observacional é utilizado há muitos anos, no entanto não existe uma metodologia consistente e estruturada para a incorporação dos dados da monitorização na adaptação do sistema de suporte em tempo real. A metodologia proposta possibilitará a otimização do sistema de suporte e do custo total da obra, tal como um aumento da segurança nos trabalhos de escavação.
Vibrations in rock masses can be a significant hazard, leading to human discomfort and structural... more Vibrations in rock masses can be a significant hazard, leading to human discomfort and structural damage. Recent cases of subway or tunnel excavation near existing dams in Portugal have raised again the importance of this topic. Traditional statistical tools have been used to study wave propagation in rock, but fall short when rock fracturing or faulting radically changes the way vibration propagates. Numerical models such as finite-element or finite-difference models also have some insufficiencies, namely in the way discontinuities are represented. We propose the utilization of bonded particle models based on the Particle Discrete Element Method. Synthetic rock samples are generated and their static elastic properties are calibrated by manipulating microproperties (assembly organization and normal and shear contact stiffness). The static and dynamic properties of the rock cores are tested and the complete elastic response of the model is evaluated and discussed.
Southern Portugal presents a rich heritage constituted by several constructions made from unstabi... more Southern Portugal presents a rich heritage constituted by several constructions made from unstabilised rammed earth (URE), which are threatened by several factors, ranging from lack of conservation to a non-negligible seismic hazard. These threatens are enhanced by the fact that little is known about the shear behaviour of URE constructions. The preservation of this heritage requires definitely the development of this knowledge and, in addition, the development of adequate intervention solutions. This paper presents an experimental program where the shear behaviour of URE is assessed by means of diagonal compression tests on representative wallet-specimens. Furthermore, the use of mud grouts in repairing cracks was also assessed. The results showed that the shear behaviour of URE depends on the binding capacity promoted by the clay fraction and on the friction and interlocking promoted by the coarse aggregates. The repair by injection was shown to promote satisfactory shear strength recovery of the specimens, but was less effective in recovering the initial shear stiffness.
Como material de construção não normalizado, a terra é ainda associada à construção de subsistênc... more Como material de construção não normalizado, a terra é ainda associada à construção de subsistência dos países em desenvolvimento. Porém, as vantagens da construção em terra têm sido cada vez mais reconhecidas, nomeadamente a sua sustentabilidade. Esta mudança de paradigma tem levado ao desenvolvimento de técnicas modernas de construção em terra, particularmente a alvenaria de blocos de terra comprimida (BTC). A estabilização química tradicional do solo é um processo de melhoramento frequentemente utilizado, mas que também aumenta significativamente a energia incorporada dos BTC. Este artigo apresenta uma solução de estabilização alternativa para BTC, baseada na ativação alcalina de cinza volante. O comportamento mecânico dos BTC e da respetiva alvenaria de junta seca é estudado através de um programa experimental, que inclui a caraterização do comportamento ao corte da alvenaria.
The aim of this work is to use Data Mining tools to develop models for the prediction of hard roc... more The aim of this work is to use Data Mining tools to develop models for the prediction of hard rock tunnel boring machine (TBM) penetration rate (ROP). A database published by was used to develop these models. The parameters of the database were the uniaxial compressive strength (UCS), an index used to quantify the brittleness and toughness and denominated peak slope index (PSI), the distance between the planes of weakness (DPW), the angle between tunnel axis and the planes of weakness (α) and the output parameter rate of penetration (ROP). The R program environment was used as a modeling tool to apply the artificial neural networks (ANN) and the support vector machine (SVM) algorithms and the corresponding models. These models were compared with two equations presented by Yagiz and . It was concluded that the ANN model has the best performance. Moreover, these new models allowed computing the importance of the different input parameters for predicting machine performance. It was concluded that PSI is the most important parameter and UCS is the less important parameter.
In this paper, a study is performed to evaluate the main advantages and limitations of different ... more In this paper, a study is performed to evaluate the main advantages and limitations of different types of optimization algorithms for the identification of geomechanical parameters in underground structures. The main goal was to evaluate their main differences in terms of robustness and efficiency in diverse circumstances. Two different types of algorithms were tested: i) classical algorithms which use the gradient of the error function to guide the search, namely the steepest descent, conjugate gradient and quasi-Newton; and ii) an innovative evolutionary algorithm, from the artificial intelligence field, called evolution strategy. The first was coupled with a 3D model of a tunnel while for the latter analytical solutions were used for a much higher number of calculations and tests were expected to perform due to its nature. The algorithms were tested in both elasticity and elasto-plasticity using the Mohr-Coulomb constitutive model. In elasticity both types of algorithms showed a good performance but in elasto-plasticity the classical algorithms revealed a poor behaviour mainly in terms of robustness, failing to converge in several situations. It was found that in many situations these limitations were avoided by the innovative algorithm presented in this work showing an interesting potential for future developments.
A alargada rede de infraestruturas viárias existente atualmente em Portugal, tem contribuído para... more A alargada rede de infraestruturas viárias existente atualmente em Portugal, tem contribuído para uma crescente melhoria nas condições de mobilidade. De todas as componentes constituintes da rede, os taludes são os que apresentam um défice maior em termos de sistemas de avaliação de qualidade.
... JORNADAS LUSO-ESPANHOLAS SOBRE OBRAS SUBTERRÂNEAS, Madrid, 2003 – “Jornadas Luso-Espanholas s... more ... JORNADAS LUSO-ESPANHOLAS SOBRE OBRAS SUBTERRÂNEAS, Madrid, 2003 – “Jornadas Luso-Espanholas sobre nas obras subterraneas : relevancia da prospecção e da observação geotecnicas e primeira lição internacional Jiménez Salas.” [Madrid] : CEDEX, 2003. ...
In this paper a KBS computational system, designated by GEOPAT, for the calculation of geomechani... more In this paper a KBS computational system, designated by GEOPAT, for the calculation of geomechanical parameters for modelling underground structures in rock and soil formations is presented. To congregate the specialists' knowledge in rock and soil domains, and in particular in the tunnel engineering, causal nets have been established for decision support. GEOPAT determines the parameters for rock and soil formations, as well as heterogeneous rock formations. The developed GEOPAT system was applied to a large underground station in urban environment, excavated in granite formations, in order to obtain the deformability and strength parameters of the surrounding rock masses. Numerical models were developed considering either the obtained geomechanical parameters using artificial intelligence techniques or the parameters used in design. The numerical results obtained with the two sets of parameters are compared, as well as with the monitoring results. Some conclusions are drawn.
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