Geological controls on the geometry of incised-valley fills: Insights from a global dataset of late-Quaternary examples

Incised valleys that develop due to relative sea-level change are common features of continental shelves and coastal plains. Assessment of the factors that control the geometry of incised-valley fills has hitherto largely relied on conceptual, experimental or numerical models, else has been grounded on case studies of individual depositional systems. Here, a database-driven statistical analysis of 151 late-Quaternary incised-valley fills has been performed, the aim being to investigate the geological controls on their geometry. Results of this analysis have been interpreted with consideration of the role of different processes in determining the geometry of incised-valley fills through their effect on the degree and rate of river incision, and on river size and mobility. The studied incised-valley fills developed along active margins are thicker and wider, on average, than those along passive margins, suggesting that tectonic setting exerts a control on the geometry of incised-valley fills, likely through effects on relative sea-level change and river behaviour, and in relation to distinct characteristics of basin physiography, water discharge and modes of sediment delivery. Valley-fill geometry is positively correlated with the associated drainage-basin size, confirming the dominant role of water discharge. Climate is also inferred to exert a potential control on valley-fill dimensions, possibly through modulations of temperature, peak precipitation, vegetation and permafrost, which would in turn affect water discharge, rates of sediment supply and valley-margin stability. Shelves with slope breaks that are currently deeper than 120 m contain incised-valley fills that are thicker and wider, on average, than those hosted on shelves with breaks shallower than 120 m. No correlation exists between valley-fill thickness and present-day coastal-prism convexity, which is measured as the difference in gradient between lower coastal plains and inner shelves. These findings challenge some concepts embedded in sequence stratigraphic thinking, and have significant implications for analysis and improved understanding of source-to-sink sediment route-ways, and for attempting predictions of the occurrence and characteristics of hydrocarbon reservoirs

Static-explicit FE modeling of 3-d large deformation multibody contact problems on parallel computer

A static-explicit method is employed to simulate static or quasi-static multi-deformation-body contact problems with friction. Based on the characteristics of the explicit time integration algorithm, a reliable and efficient contact element strategy is developed to handle the multi-deformation-body contact with friction. The friction behaviour is governed by the Coulomb friction model with an additional limit on the allowable shear stress, which is treated as a flow plasticity rule. The penalty method is adopted to impose the normal and the sticking contact. Meanwhile, with choosing contact interfaces as sub-domain boundaries, a parallel algorithm for contact is proposed based on domain decomposition method and implemented for the large scale computation. In addition, a contact searching algorithm is also introduced. Finally, numerical examples of contact between finite deformation bodies are presented to show the efficiency and stability of this algorithm

Finite element analysis of Tube hydroforming using static explicit method

Recently Tube hydroforming is getting increasing attention due to the preservation of global environment and demand for impact-damage resistant in automobile body structure. In this paper modification of FEM code for tube hydroforming simulation is presented and the comparison of experimental results and simulation results is made to confirm the validity of the code. An algorithm to deal with hydrostatic pressure applied in the tube is newly implemented in ITAS3D, a sheet forming simulation program using static explicit method. Hydrostatic copper tube bulging with cylindrical die is calculated with the code, and analytical results show good agreement with experimental ones. In this calculation, only very small difference is found between the results of calculation with using solid element and shell element