نتایج جستجو برای: sheeted dike
تعداد نتایج: 1429 فیلتر نتایج به سال:
In analogy with hydrothermal processes on Earth’s seafloor, Martian hydrothermal systems may provide a mechanism for transporting water, chemicals, and energy to the surface. We model magmatic dike driven hydrothermal systems in which we consider changes to the surrounding permeability resulting from the emplacement of the dike (Craft, 2010) and calculate water fluxes to the surface. When compa...
Wadi Ghadir ophiolite in the Egyptian Eastern Desert, which forms northern part of Nubian Shield, is considered as one best-preserved segments Neoproterozoic oceanic lithosphere on Earth. Primary melt calculations and thermodynamic modeling new geochemical data for pillow lavas dike complexes, integrated with comprehensive petrographic investigations, are here employed to unravel geodynamic evo...
Dike emplacement in volcanic rift zones is often associated with the injection of “bladelike” dikes, which propagate long distances parallel to the rift, but frequently remain trapped at depth and erupt only near the tip of the dike. Over geologic time, this style of dike injection implies that a greater percentage of extension is accommodated by magma accretion at depth than near the surface. ...
Shallow dike intrusion and widening was proposed several decades ago as a cause of surface faulting and graben formation on Earth. This hypothesis was subsequently applied to the spectacular linear and/or radial graben systems visible on Mars. However, a recent study has suggested that shallow dike intrusion on Mars results in contractional folding and uplift adjacent to dike walls rather than ...
As continental rifts evolve towards mid-ocean ridges, strain is accommodated by repeated episodes of faulting and magmatism. Discrete rifting episodes have been observed along two subaerial divergent plate boundaries, the Krafla segment of the Northern Volcanic Rift Zone in Iceland and the Manda-Hararo segment of the Red Sea Rift in Ethiopia. In both cases, the initial and largest dike intrusio...
In the Netherlands the current dike design policy is to design flood defence structures corresponding to an agreed flooding probability with an extra safety board of at least 0.5 m. For river dikes a return period of 1,250 years is used to determine the design water levels. A problem with this strategy is that it builds on assumptions with regard to the intrinsically uncertain probability distr...
In this study, the effect of the secondary flow strength and vorticity on variations of bed shear stress for different positions of spur dike are compared through a mild 90˚ bend along with a T-shaped spur dike in a rigid bed. To carry out these experiments, three dimensional velocimeters (ADV) have been used for measuring velocity. Moreover, a comparison has been made between velocity vectors ...
This work aims to model the optimal control of dike heights. The control problem leads to so-called Hamilton-Jacobi-Bellman (HJB) variational inequalities, where the dike-increase and reinforcement times act as input quantities to the control problem. The HJB equations are solved numerically with an Essentially Non-Oscillatory (ENO) method. The ENO methodology is originally intended for hyperbo...
Dike height optimization is of major importance to the Netherlands since a large part of the country is below sea level and high water levels in rivers may cause floods. In this paper we propose a cost-benefit analysis to determine optimal dike heights. We improve the model proposed by Van Dantzig (1956) after a devastating flood in the Netherlands in 1953. For one important class of the dike i...
Statistical evaluation of historical dike failure mechanism The failure mechanism of flood protection dikes includes physical (geotechnical, seepage) processes leading to a dike breach. An awareness of the failure mechanism is required directly in dike stability calculations and indirectly for risk calculations. Statistics of historical data indicate among others the distribution and frequency ...
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