In Cameroon in general and in the Highlands of Cameroon in particular, there is no fracture map since its realization is not easy. The region’s harsh accessibility and climatic conditions make it difficult to carry o...In Cameroon in general and in the Highlands of Cameroon in particular, there is no fracture map since its realization is not easy. The region’s harsh accessibility and climatic conditions make it difficult to carry out geological prospecting field missions that require large investments. This study proposes a semi-automatic lineament mapping approach to facilitate the elaboration of the fracture map in the West Cameroon Highlands. It uses neural networks in tandem with PCI Geomatica’s LINE algorithm to extract lineaments semi-automatically from an ALOS PALSAR 2 radar image. The cellular neural network algorithm of Lepage et al (2000) is implemented to enhance the pre-processed radar image. Then, the LINE module of Geomatica is applied </span><span style="font-family:Verdana;">to</span><span style="font-family:Verdana;"> the enhanced image for the automatic extraction of lineaments. Finally, a control and a validation of the expert by spatial analysis allows elaborat</span><span style="font-family:Verdana;">ing</span><span style="font-family:Verdana;"> the fracture map. The results obtained show that neural networks enhance and facilitate the identification of lineaments on the image. The resulting map contains more than 1800 fractures with major directions N20<span style="white-space:nowrap;">°</span> - 30<span style="white-space:nowrap;">°</span>, NS, N10<span style="white-space:nowrap;">°</span> - 20<span style="white-space:nowrap;">°</span>, N50<span style="white-space:nowrap;">°</span> - 60<span style="white-space:nowrap;">°</span>, N70<span style="white-space:nowrap;">°</span> - 80<span style="white-space:nowrap;">°</span>, N80<span style="white-space:nowrap;">°</span> - 90<span style="white-space:nowrap;">°</span>, N100<span style="white-space:nowrap;">°</span> - 110<span style="white-space:nowrap;">°</span>, N110<span style="white-space:nowrap;">°</span> - 120<span style="white-space:nowrap;">°</span> and N130<span style="white-space:nowrap;">°</span> - 140<span style="white-space:nowrap;">°</span> and N140<span style="white-space:nowrap;">°</span> - 150<span style="white-space:nowrap;">°</span>. It can be very useful for geological and hydrogeological studies, and especially to inform on the productivity of aquifers in this region of high agro-pastoral and mining interest for Cameroon and the Central African sub-region.展开更多
Pressure and tilt data are jointly inverted to simultaneously map the orientation and dimensions of a hydraulic fracture.The deformation induced by a fracture under internal pressure is modeled using the distributed d...Pressure and tilt data are jointly inverted to simultaneously map the orientation and dimensions of a hydraulic fracture.The deformation induced by a fracture under internal pressure is modeled using the distributed dislocation technique.The planar fracture is represented by four quarter ellipses,joined at the center and sharing semi-axes.This configuration provides a straightforward model for characterizing asymmetric fracture geometry.The inverse problem of mapping the fracture geometry is formulated using the Bayesian probabilistic method,combining the a priori information on the fracture model with updated information from pressure and tilt data.Solving the nonlinear inverse problem is achieved by pseudo-randomly sampling the posterior probability distribution through the Markov chain Monte Carlo method.The resulting posterior probability distribution is then explored to assess uncertainty,resolution,and correlation between model parameters.Numerical experiments are conducted to verify the accuracy and validity of the proposed analysis method in mapping the fracture geometry using synthetic pressure and tilt data.展开更多
Finite element analysis is developed to simulate the breakage of capsule in capsule-based self-healing concrete.A 2D circular capsule with different core-shell thickness ratios embedded in the mortar matrix is analyze...Finite element analysis is developed to simulate the breakage of capsule in capsule-based self-healing concrete.A 2D circular capsule with different core-shell thickness ratios embedded in the mortar matrix is analyzed numerically along with their interfacial transition zone.Zero-thickness cohesive elements are pre-inserted into solid elements to represent potential cracks.This study focuses on the effects of mismatch fracture properties,namely fracture strength and energy,between capsule and mortar matrix into the breakage likelihood of the capsule.The extensive simulations of 2D specimens under uniaxial tension were carried out to investigate the key features on the fracture patterns of the capsule and produce the fracture maps as the results.The developed fracture maps of capsules present a simple but valuable tool to assist the experimentalists in designing appropriate capsule materials for self-healing concrete.展开更多
文摘In Cameroon in general and in the Highlands of Cameroon in particular, there is no fracture map since its realization is not easy. The region’s harsh accessibility and climatic conditions make it difficult to carry out geological prospecting field missions that require large investments. This study proposes a semi-automatic lineament mapping approach to facilitate the elaboration of the fracture map in the West Cameroon Highlands. It uses neural networks in tandem with PCI Geomatica’s LINE algorithm to extract lineaments semi-automatically from an ALOS PALSAR 2 radar image. The cellular neural network algorithm of Lepage et al (2000) is implemented to enhance the pre-processed radar image. Then, the LINE module of Geomatica is applied </span><span style="font-family:Verdana;">to</span><span style="font-family:Verdana;"> the enhanced image for the automatic extraction of lineaments. Finally, a control and a validation of the expert by spatial analysis allows elaborat</span><span style="font-family:Verdana;">ing</span><span style="font-family:Verdana;"> the fracture map. The results obtained show that neural networks enhance and facilitate the identification of lineaments on the image. The resulting map contains more than 1800 fractures with major directions N20<span style="white-space:nowrap;">°</span> - 30<span style="white-space:nowrap;">°</span>, NS, N10<span style="white-space:nowrap;">°</span> - 20<span style="white-space:nowrap;">°</span>, N50<span style="white-space:nowrap;">°</span> - 60<span style="white-space:nowrap;">°</span>, N70<span style="white-space:nowrap;">°</span> - 80<span style="white-space:nowrap;">°</span>, N80<span style="white-space:nowrap;">°</span> - 90<span style="white-space:nowrap;">°</span>, N100<span style="white-space:nowrap;">°</span> - 110<span style="white-space:nowrap;">°</span>, N110<span style="white-space:nowrap;">°</span> - 120<span style="white-space:nowrap;">°</span> and N130<span style="white-space:nowrap;">°</span> - 140<span style="white-space:nowrap;">°</span> and N140<span style="white-space:nowrap;">°</span> - 150<span style="white-space:nowrap;">°</span>. It can be very useful for geological and hydrogeological studies, and especially to inform on the productivity of aquifers in this region of high agro-pastoral and mining interest for Cameroon and the Central African sub-region.
基金supported by the National Natural Science Foundation of China under Grant Nos.52374033 and U23A20596.
文摘Pressure and tilt data are jointly inverted to simultaneously map the orientation and dimensions of a hydraulic fracture.The deformation induced by a fracture under internal pressure is modeled using the distributed dislocation technique.The planar fracture is represented by four quarter ellipses,joined at the center and sharing semi-axes.This configuration provides a straightforward model for characterizing asymmetric fracture geometry.The inverse problem of mapping the fracture geometry is formulated using the Bayesian probabilistic method,combining the a priori information on the fracture model with updated information from pressure and tilt data.Solving the nonlinear inverse problem is achieved by pseudo-randomly sampling the posterior probability distribution through the Markov chain Monte Carlo method.The resulting posterior probability distribution is then explored to assess uncertainty,resolution,and correlation between model parameters.Numerical experiments are conducted to verify the accuracy and validity of the proposed analysis method in mapping the fracture geometry using synthetic pressure and tilt data.
基金Supported and financed by RISTEKDIKTI(Directorate General of Resources for Science,Technology and Higher Education.Ministry of Research,Technology and Higher Education of Indonesia)under funding agreement No:153.39/E4.4/2014the German Academic Exchange Program(DAAD).
文摘Finite element analysis is developed to simulate the breakage of capsule in capsule-based self-healing concrete.A 2D circular capsule with different core-shell thickness ratios embedded in the mortar matrix is analyzed numerically along with their interfacial transition zone.Zero-thickness cohesive elements are pre-inserted into solid elements to represent potential cracks.This study focuses on the effects of mismatch fracture properties,namely fracture strength and energy,between capsule and mortar matrix into the breakage likelihood of the capsule.The extensive simulations of 2D specimens under uniaxial tension were carried out to investigate the key features on the fracture patterns of the capsule and produce the fracture maps as the results.The developed fracture maps of capsules present a simple but valuable tool to assist the experimentalists in designing appropriate capsule materials for self-healing concrete.
