Restrained bending of thin-walled box beam with honeycomb core is analyzed on the basis of rigid profile assumption. The method of variable separation is applied and two ordinary differential governing equations are e...Restrained bending of thin-walled box beam with honeycomb core is analyzed on the basis of rigid profile assumption. The method of variable separation is applied and two ordinary differential governing equations are established and solved. The boundary conditions are satisfied rigorously and the solutions are expressed by means of eigen function expansions. The diagram of shearing force is formulated by trigonometric series and used to determine the coefficients in above expansions. The computational resuits give the chord and span wise distributions of nomal and shear stress in the cover plate and the honeycomb core. At the same time, the attenuation of additional stress from fixed end to free end along the length of beam is shown clearly.展开更多
Notable differences in the structural characteristics and evolution of three adjacent sub-sags,i.e.,the Wenchang sub-sags A,B,and C,on the downthrown side of the Zhu IlI South Fault in the Wenchang Sag,are significant...Notable differences in the structural characteristics and evolution of three adjacent sub-sags,i.e.,the Wenchang sub-sags A,B,and C,on the downthrown side of the Zhu IlI South Fault in the Wenchang Sag,are significant as they affect the formation and distribution of the oil and gas in these three sub-sags.However,the differences in their tectonic evolutions and formation mechanisms have not yet been adequately explained.In this paper,stress analysis,equilibrium profiles,and paleogeomorphic restora-tion,are used to investigate the dynamic settings,formation mechanisms,and influencing factors of the structural deformation related to the formation of the Wenchang Sag based on interpretation of seismic data.The results of the stress analysis suggest clockwise deflection of the regional tensile stress direction from a WNW-ESE trend during the Early Paleocene to NW-SE and NNW-SSE trends during the Eocene,to a nearly N-S trend during the Oligocene,and finally to a NNE-SSW trend during the Miocene.This clockwise rotation of the regional tensile stress direction led to the formation of a dextral strike-slip stress component parallel to the NE-trending Zhu I South Fault.This strike-slip stress component formed a releasing bend in sub-sag A,and may be associated with the continuous subsidence of a thick sedimentary layer in sub-sag A.It also created a restraining bend in sub-sag B,which underwent multiple structural inversions during its extension and subsidence and has a relatively s mall sedimentary thick-ness.The double restraining bend in sub-sag C is considered to have been strongly uplifted and eroded in response to this strike-slip stress component.Four obvious structural inversions in sub-sag B are iden-tified in this paper.These structural inversions correspond to the last four regional tectonic movements.This interpretation suggests that the formation of the structural inversions was likely related to the strong tensile stress and the small intersection angle between the direction of the regional tensile stress and the pre-existing boundary fault.The rotation of the tensile stress direction was responsible for the strike-slip movement on the pre-existing boundary fault and the formation of the releasing bend and restraining bend,which controlled the structural evolutions of the sub-sags.This reasonably explains the differential tectonic evolution of these three sub-sags in the Wenchang Sag,and provides a crucial idea forstructuralanalysisof similarbasins.展开更多
The study aims to understand geometry and evolution of accommodation zones along restraining and releasing bends in strike slip systems which is often complex and characterized by sharp change in polarity,resulting in...The study aims to understand geometry and evolution of accommodation zones along restraining and releasing bends in strike slip systems which is often complex and characterized by sharp change in polarity,resulting in a difficult characterization of traps location.A batch of sandbox modelling experiments was performed using a layered scaled sand material.The setup parameters of the wooden baseplates used in the first two experiments(SS1 and SS2)are basement offset of 6.5 cm/3 cm,90/90stepovers in releasing and restraining bends of total 96 cm length and 25 cm width.The third experiment(SS3)was performed with basement offset of 6.5 cm/3 cm,156/126stepovers in releasing and restraining bends of total 96 cm length and 25 cm width.The experiments were performed with special attention to the role of syn-kinematic sedimentation and the pre-existing structure of the basement.A sequence of pop-up and pull-apart structures was produced.Along the main structures,complex fault trend was compatible with a sinistral riedel distribution and a counterclockwise rotation of pre-existent elements.Change of fault's polarity at depth and dip direction flipping of high angle faults in accommodation zones were clearly observed.Even more,progressive propagation of the pop-up structures produces a spectacular inversion of adjacent extensional structures.Comparing results of the model with the Seagap fault zone,it is possible to put in evidence similar fault orientation and distribution.Internal structures developed were strongly influenced by syn-kinematic sedimentation as observed by characteristic helicoidal shape of growth faults.The analogue models clearly describe how boundary faults of the pull-apart basin along a paired bend,initially characterized by a normal kinematic can be subsequently inverted in the later stages,which can potentially have a strong impact on the petroleum system.展开更多
文摘Restrained bending of thin-walled box beam with honeycomb core is analyzed on the basis of rigid profile assumption. The method of variable separation is applied and two ordinary differential governing equations are established and solved. The boundary conditions are satisfied rigorously and the solutions are expressed by means of eigen function expansions. The diagram of shearing force is formulated by trigonometric series and used to determine the coefficients in above expansions. The computational resuits give the chord and span wise distributions of nomal and shear stress in the cover plate and the honeycomb core. At the same time, the attenuation of additional stress from fixed end to free end along the length of beam is shown clearly.
基金supported by the National Natural Science Foundation of China(Grant No.9132820142006068)Shandong Special Fund of Qingdao National Laboratory of Marine Science and Technology(No.2021QNLM020001-1).
文摘Notable differences in the structural characteristics and evolution of three adjacent sub-sags,i.e.,the Wenchang sub-sags A,B,and C,on the downthrown side of the Zhu IlI South Fault in the Wenchang Sag,are significant as they affect the formation and distribution of the oil and gas in these three sub-sags.However,the differences in their tectonic evolutions and formation mechanisms have not yet been adequately explained.In this paper,stress analysis,equilibrium profiles,and paleogeomorphic restora-tion,are used to investigate the dynamic settings,formation mechanisms,and influencing factors of the structural deformation related to the formation of the Wenchang Sag based on interpretation of seismic data.The results of the stress analysis suggest clockwise deflection of the regional tensile stress direction from a WNW-ESE trend during the Early Paleocene to NW-SE and NNW-SSE trends during the Eocene,to a nearly N-S trend during the Oligocene,and finally to a NNE-SSW trend during the Miocene.This clockwise rotation of the regional tensile stress direction led to the formation of a dextral strike-slip stress component parallel to the NE-trending Zhu I South Fault.This strike-slip stress component formed a releasing bend in sub-sag A,and may be associated with the continuous subsidence of a thick sedimentary layer in sub-sag A.It also created a restraining bend in sub-sag B,which underwent multiple structural inversions during its extension and subsidence and has a relatively s mall sedimentary thick-ness.The double restraining bend in sub-sag C is considered to have been strongly uplifted and eroded in response to this strike-slip stress component.Four obvious structural inversions in sub-sag B are iden-tified in this paper.These structural inversions correspond to the last four regional tectonic movements.This interpretation suggests that the formation of the structural inversions was likely related to the strong tensile stress and the small intersection angle between the direction of the regional tensile stress and the pre-existing boundary fault.The rotation of the tensile stress direction was responsible for the strike-slip movement on the pre-existing boundary fault and the formation of the releasing bend and restraining bend,which controlled the structural evolutions of the sub-sags.This reasonably explains the differential tectonic evolution of these three sub-sags in the Wenchang Sag,and provides a crucial idea forstructuralanalysisof similarbasins.
基金This research paper was prepared from the experimental data simulated with Sandbox analogy modelling machine in the Geomodel laboratory of College of Earth sciences,University of Dodoma.Our appreciation goes to senior LabEngineer Mr Audax Kiwango for his tireless technical support in operating the Sandbox machine and Statoil Tanzania(Equinor)for providing information of structural architecture of their play。
文摘The study aims to understand geometry and evolution of accommodation zones along restraining and releasing bends in strike slip systems which is often complex and characterized by sharp change in polarity,resulting in a difficult characterization of traps location.A batch of sandbox modelling experiments was performed using a layered scaled sand material.The setup parameters of the wooden baseplates used in the first two experiments(SS1 and SS2)are basement offset of 6.5 cm/3 cm,90/90stepovers in releasing and restraining bends of total 96 cm length and 25 cm width.The third experiment(SS3)was performed with basement offset of 6.5 cm/3 cm,156/126stepovers in releasing and restraining bends of total 96 cm length and 25 cm width.The experiments were performed with special attention to the role of syn-kinematic sedimentation and the pre-existing structure of the basement.A sequence of pop-up and pull-apart structures was produced.Along the main structures,complex fault trend was compatible with a sinistral riedel distribution and a counterclockwise rotation of pre-existent elements.Change of fault's polarity at depth and dip direction flipping of high angle faults in accommodation zones were clearly observed.Even more,progressive propagation of the pop-up structures produces a spectacular inversion of adjacent extensional structures.Comparing results of the model with the Seagap fault zone,it is possible to put in evidence similar fault orientation and distribution.Internal structures developed were strongly influenced by syn-kinematic sedimentation as observed by characteristic helicoidal shape of growth faults.The analogue models clearly describe how boundary faults of the pull-apart basin along a paired bend,initially characterized by a normal kinematic can be subsequently inverted in the later stages,which can potentially have a strong impact on the petroleum system.
