Processes of Speleogenessis

Dreybrodt, Wolfgang; Gabrovšek, Franci; Romanov, Douchko

doi:10.3986/9789610503125

Cited by 82 publications

(58 citation statements)

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“…Compared to that scenario, however, the bimodal features apparent in the aperture distribution (Figure 9) suggest that conduit enlargement proceeds less uniformly here. It should be noted though that the positive‐feedback mechanism between conduit enlargement and increasing flow rates becomes weaker if the input concentrations are further increased above the switch concentration [ Dreybrodt et al , 2005]. Thus the aperture distribution might become more similar to that of the low‐permeability scenario if higher input concentrations were used.…”

Section: Resultsmentioning

confidence: 99%

“…A multiplicity of field observations and laboratory dissolution experiments have contributed to the general understanding of the chemical and hydraulic processes involved in conduit evolution [cf., Ford and Williams , 2007; Klimchouk et al , 1996, 2000; Palmer , 1991; White , 1988]. Several numerical models have been developed to simulate conduit evolution in karst terrains and to understand and analyze these mechanisms of speleogenesis [e.g., Andre and Rajaram , 2005; Bauer et al , 2005; Birk et al , 2003, 2005; Bloomfield et al , 2005; Clemens et al , 1996, 1999; Dreybrodt , 1990, 1996; Dreybrodt et al , 2005; Gabrovšek and Dreybrodt , 2000,2001; Groves and Howard , 1994a, 1994b; Howard and Groves , 1995; Kaufmann , 2003a, 2003b, 2005; Kaufmann and Braun , 1999, 2000; Liedl and Sauter , 1998; Romanov et al , 2003; Siemers and Dreybrodt , 1998]. These models demonstrated that early karst genesis is governed by a positive‐feedback mechanism involving the mutual enhancement of flow rate and solutional conduit enlargement.…”

Section: Introductionmentioning

confidence: 99%

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Conduit evolution in deep‐seated settings: Conceptual and numerical models based on field observations

Rehrl

Birk

Klimchouk

2008

Water Resources Research

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[1] To examine the interrelation between hydrogeological environment and conduit development in deep-seated settings, a conceptual model is tested by numerical modeling. Based on field observations, simplified model settings are designed and crucial parameters are varied. A coupled continuum-pipe flow model is employed for simulating conduit development within the soluble unit of a multilayer aquifer system. In agreement with field observations, the evolving cave patterns are characterized by pronounced horizontal passages and multiple vertical conduits at the bottom of the soluble unit but only few at the top. The frequency distribution of conduit diameters is found to be bimodal if the permeability of the rock formation is sufficiently high to allow competitive conduit development governed by the feedback between increasing flow and dissolution rates. This feedback, however, is suppressed in low-permeability formations. As a consequence, conduit development is uniform rather than competitive.Citation: Rehrl, C., S. Birk, and A. B. Klimchouk (2008), Conduit evolution in deep-seated settings: Conceptual and numerical models based on field observations, Water Resour. Res., 44, W11425,

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Conduit evolution in deep‐seated settings: Conceptual and numerical models based on field observations

Rehrl

Birk

Klimchouk

2008

Water Resources Research

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“…The linear void space growth function relating initial void space area with the removed area at further intervals stands as an approximation for real fracture or void growth by physio-chemical processes in karst aquifers. Pure chemical dissolution of limestone or gypsum hereby shows a linear behaviour as long as the concentration of the under saturated incoming fluid is lower than 90 % of the equilibrium concentration for that mineral (Dreybrodt et al, 2005;Kaufmann and Dreybrodt, 2007;Romanov et al, 2010).…”

Section: Appendix Amentioning

confidence: 89%

Distinct Element geomechanical modelling of the formation of sinkhole cluster within large-scale karstic depressions

Al-Halbouni¹,

Holohan²,

Taheri³

et al. 2019

Preprint

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Abstract. The 2D Distinct Element Method (DEM) code (PFC2D_V5) is here used to simulate the evolution of subsidence-related karst landforms, such as single and clustered sinkholes, and associated larger-scale depressions. Subsurface material in the DEM model is removed by a feedback loop to produce an array of cavities; this simulates a network of subsurface groundwater conduits growing by chemical/mechanical erosion. The growth of the cavity array is coupled mechanically to the surroundings such that cavities can grow also in part by material failure at their margins, which in the limit can produce individual collapse sinkholes. Two end-member growth scenarios of the cavity array and their impact on surface subsidence were examined in the models: (1) cavity growth at the same level and at the same individual growth rate; (2) cavity growth at progressively deepening levels with varying individual growth rates. These growth scenarios are characterised by differing stress patterns across the cavity array and its overburden, which are in turn an important factor for the formation of sinkholes and uvala-like depressions. For growth scenario (1), a stable compression arch is established around the cavity array, hindering sinkhole collapse into individual cavities and favouring block-wise subsidence across the whole cavity array. In contrast, for growth scenario (2), the stress system is more heterogeneous, such that local stress concentrations exist around individual cavities leading to stress interaction. Consequently, sinkhole collapses into individual cavities occurs by shear or tensile failure of the overburden, and these sinkholes lie within a larger scale depression linked to the cavity array as a whole. The results from models with growth scenario (2), which also account for variations in mechanical properties of the overburden, are in close agreement with surface morphological and subsurface geophysical observations from a karst area on the eastern shore of the Dead Sea.

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“…While our model does not take the mass balance approach, it does employ the commonly used sediment transport equation of Fernandez Luque and van Beek (1976), and as such the scaling laws derived should be identical. Since we are only modeling a single cross-section we also cannot include longitudinal chemical effects, such as dissolution rate decreasing downstream with increasing dissolved load, a fundamental part of the pre-breakthrough speleogenesis models (e.g., Dreybrodt, 1996;Dreybrodt et al 2005;Groves and Howard, 1994;Palmer, 1991).…”

Section: Cross-section Evolution Modelmentioning

confidence: 99%

“…While mathematical models of speleogenesis (cave formation) have been around since the 1980s (Dreybrodt, 1988;Palmer, 1984), they have primarily focused on flow network pattern development during the pre-breakthrough stage, with individual conduit widths at or below the centimeter scale. Such models typically neglect the evolution of passage cross-sectional shape and instead treat incipient cave passages as fractures or tubes (e.g., Dreybrodt et al 2005). There are several barriers to the development of models for cross-section evolution.…”

Section: Introductionmentioning

confidence: 99%

Modeling cave cross‐section evolution including sediment transport and paragenesis

Cooper

Covington

2020

Earth Surf Processes Landf

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Summary Deposits within caves are often used to interpret past landscape evolution and climate conditions. However, cave passage shapes also preserve information about past conditions. Despite the usefulness of passage shape, no previous models simulate cave cross‐section evolution in a realistic manner. Here we develop a model for evolving cave passage cross‐sections using a shear stress estimation algorithm and a shear stress erosion rule. Our model qualitatively duplicates observed cave passage shapes so long as erosion rates vary with shear stress, as in the case of transport limited dissolution or mechanical erosion. This result provides further evidence that erosion rates within caves are not typically limited by surface reaction rates, even though current speleogenesis models predict surface‐rate limitation under most turbulent flow conditions. By adding sediment transport and alluviation to the model we successfully simulate paragenetic channels. Simulations duplicate the hypothesized dynamics of paragenesis, whereby: 1) the cross‐section of a phreatic passage grows until shear stress is sufficiently reduced that alluviation occurs, 2) the floor of the passage becomes armored and erosion continues on the ceiling and walls, 3) negative feedback produces an equilibrium cross‐sectional area such that shear stress is sufficient to transport incoming sediment. We derive an approximate scaling relationship that indicates that equilibrium paragenetic channel width scales with the square root of discharge, and weakly with the inverse of sediment supply. Simulations confirm this relationship and show that erosion mechanism, sediment size, and roughness are secondary controls. The inverse scaling of width with sediment supply in paragenetic channels contrasts with surface bedrock channels, which respond to larger sediment supplies by widening. Our model provides a first step in simulating cave cross‐section evolution and points to the need for a better understanding of the dominant erosion mechanisms in soluble bedrock channels. © 2020 John Wiley & Sons, Ltd.

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Processes of Speleogenessis

Cited by 82 publications

References 0 publications

Conduit evolution in deep‐seated settings: Conceptual and numerical models based on field observations

Conduit evolution in deep‐seated settings: Conceptual and numerical models based on field observations

Distinct Element geomechanical modelling of the formation of sinkhole cluster within large-scale karstic depressions

Modeling cave cross‐section evolution including sediment transport and paragenesis

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