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Numerical modeling of the evolution of arcades and rock pillars
Geomorphology ( IF 3.1 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.geomorph.2020.107260
Alexander Safonov , Michal Filippi , David Mašín , Jiří Bruthans

Abstract Arcades, i.e. lenticular and other specifically shaped hollows controlled by discontinuities, have recently been recognized as a weathering form typical for sandstones, weathered quartzites, granites, or tuffs. They are produced by accelerated weathering and erosion in stress shadows related to the redistribution of gravity-induced stress along planar discontinuities in the rock. These forms occur worldwide in various settings (inland humid, arid, and coastal). The origin of arcades has been demonstrated via physical experiments and supported by a relatively simplistic numerical modeling. However, details on their shaping and the evolution of related forms have not been explained. We performed an advanced numerical modeling to produce various shapes of arcades and rock pillars during the erosion of rock masses dissected by discontinuities. We demonstrate that the erosion model, in which erosion takes place when the maximum principal stress is below a certain critical value, can adequately describe the formation of arcades. In the modeling, we set higher critical values for stresses at discontinuities than in a homogeneous material (representing a rock mass) to represent the higher tendency for disintegration of the discontinuity material, which was weakened by the discontinuity formation processes. By applying various discontinuity geometries and values of critical stresses, we were able to reproduce the formation of various arcade shapes and complex-three-dimensional clusters of arcade cavities with rock pillars. Discontinuities and stress-controlled erosion/weathering are the only necessary conditions for arcade formation.

中文翻译:

拱廊和岩柱演化的数值模拟

摘要 拱廊,即由不连续性控制的透镜状和其他特殊形状的空洞,最近被认为是砂岩、风化石英岩、花岗岩或凝灰岩的典型风化形式。它们是由应力阴影中的加速风化和侵蚀产生的,这些应力阴影与重力引起的应力沿岩石平面不连续面的重新分布有关。这些形式出现在世界各地的各种环境中(内陆潮湿、干旱和沿海)。拱廊的起源已经通过物理实验得到证明,并得到了相对简单的数值模型的支持。然而,关于它们的形成和相关形式的演变的细节还没有得到解释。我们执行了先进的数值建模,以在被不连续性解剖的岩体侵蚀过程中生成各种形状的拱廊和岩柱。我们证明了当最大主应力低于某个临界值时发生侵蚀的侵蚀模型,可以充分描述拱廊的形成。在建模中,我们为不连续处的应力设置了比均质材料(代表岩体)更高的临界值,以表示不连续材料分解的更高趋势,这被不连续形成过程削弱。通过应用各种不连续几何形状和临界应力值,我们能够重现各种拱廊形状的形成和带有岩柱的拱廊空腔的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。其中当最大主应力低于某个临界值时发生侵蚀,可以充分描述拱廊的形成。在建模中,我们为不连续处的应力设置了比均质材料(代表岩体)更高的临界值,以表示不连续材料分解的更高趋势,这被不连续形成过程削弱。通过应用各种不连续几何形状和临界应力值,我们能够重现各种拱廊形状的形成和带有岩柱的拱廊空腔的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。其中当最大主应力低于某个临界值时发生侵蚀,可以充分描述拱廊的形成。在建模中,我们为不连续处的应力设置了比均质材料(代表岩体)更高的临界值,以表示不连续材料分解的更高趋势,这被不连续形成过程削弱。通过应用各种不连续几何形状和临界应力值,我们能够重现各种拱廊形状的形成和带有岩柱的拱廊空腔的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。可以充分描述拱廊的形成。在建模中,我们为不连续处的应力设置了比均质材料(代表岩体)更高的临界值,以表示不连续材料分解的更高趋势,这被不连续形成过程削弱。通过应用各种不连续几何形状和临界应力值,我们能够重现各种拱廊形状的形成和带有岩柱的拱廊空腔的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。可以充分描述拱廊的形成。在建模中,我们为不连续处的应力设置了比均质材料(代表岩体)更高的临界值,以表示不连续材料分解的更高趋势,这被不连续形成过程削弱了。通过应用各种不连续几何形状和临界应力值,我们能够重现各种拱廊形状的形成和带有岩柱的拱廊空腔的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。我们为不连续处的应力设置了比均质材料(代表岩体)更高的临界值,以表示不连续材料分解的更高趋势,这被不连续形成过程削弱了。通过应用各种不连续几何形状和临界应力值,我们能够重现各种拱廊形状的形成和带有岩柱的拱廊空腔的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。我们为不连续处的应力设置了比均质材料(代表岩体)更高的临界值,以表示不连续材料分解的更高趋势,这被不连续形成过程削弱了。通过应用各种不连续几何形状和临界应力值,我们能够重现各种拱廊形状的形成和带有岩柱的拱廊空腔的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。我们能够重现各种拱廊形状的形成和带有石柱的拱廊空洞的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。我们能够重现各种拱廊形状的形成和带有石柱的拱廊空洞的复杂三维集群。不连续性和受应力控制的侵蚀/风化是拱廊形成的唯一必要条件。
更新日期:2020-09-01
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