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  • 1
    Online Resource
    Online Resource
    Distinct element geomechanical modelling of the formation of sinkhole clusters within large-scale karstic depressions
    Copernicus GmbH ; 2019
    In:  Solid Earth Vol. 10, No. 4 ( 2019-07-29), p. 1219-1241
    Details
    In: Solid Earth, Copernicus GmbH, Vol. 10, No. 4 ( 2019-07-29), p. 1219-1241
    Abstract: Abstract. The 2-D distinct element method (DEM) code (PFC2D_V5) is used here 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 progressively 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 gravitationally loaded 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 depth level and growth rate; (2) cavity growth at progressively deepening levels with varying 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 entire cavity array, hindering sinkhole collapse into individual cavities and favouring block-wise, relatively even 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 interactions and local wall/overburden fractures. Consequently, sinkhole collapses occur in individual cavities, which results in uneven, differential subsidence within a larger-scale depression. Depending on material properties of the cavity-hosting material and the overburden, the larger-scale depression forms either by sinkhole coalescence or by widespread subsidence linked geometrically to the entire cavity array. The results from models with growth scenario (2) are in close agreement with surface morphological and subsurface geophysical observations from an evaporite karst area on the eastern shore of the Dead Sea.
    Type of Medium: Online Resource
    ISSN: 1869-9529
    URL: Article
    URL: Article
    DOI: 10.5194/se-10-1219-2019
    DOI: 10.5194/se-10-1219-2019-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2545676-3
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  • 2
    Online Resource
    Online Resource
    Geomechanical modelling of sinkhole development using distinct elements: model verification for a single void space and application to the Dead Sea area
    Copernicus GmbH ; 2018
    In:  Solid Earth Vol. 9, No. 6 ( 2018-11-23), p. 1341-1373
    Details
    In: Solid Earth, Copernicus GmbH, Vol. 9, No. 6 ( 2018-11-23), p. 1341-1373
    Abstract: Abstract. Mechanical and/or chemical removal of material from the subsurface may generate large subsurface cavities, the destabilisation of which can lead to ground collapse and the formation of sinkholes. Numerical simulation of the interaction of cavity growth, host material deformation and overburden collapse is desirable to better understand the sinkhole hazard but is a challenging task due to the involved high strains and material discontinuities. Here, we present 2-D distinct element method numerical simulations of cavity growth and sinkhole development. Firstly, we simulate cavity formation by quasi-static, stepwise removal of material in a single growing zone of an arbitrary geometry and depth. We benchmark this approach against analytical and boundary element method models of a deep void space in a linear elastic material. Secondly, we explore the effects of properties of different uniform materials on cavity stability and sinkhole development. We perform simulated biaxial tests to calibrate macroscopic geotechnical parameters of three model materials representative of those in which sinkholes develop at the Dead Sea shoreline: mud, alluvium and salt. We show that weak materials do not support large cavities, leading to gradual sagging or suffusion-style subsidence. Strong materials support quasi-stable to stable cavities, the overburdens of which may fail suddenly in a caprock or bedrock collapse style. Thirdly, we examine the consequences of layered arrangements of weak and strong materials. We find that these are more susceptible to sinkhole collapse than uniform materials not only due to a lower integrated strength of the overburden but also due to an inhibition of stabilising stress arching. Finally, we compare our model sinkhole geometries to observations at the Ghor Al-Haditha sinkhole site in Jordan. Sinkhole depth ∕ diameter ratios of 0.15 in mud, 0.37 in alluvium and 0.33 in salt are reproduced successfully in the calibrated model materials. The model results suggest that the observed distribution of sinkhole depth ∕ diameter values in each material type may partly reflect sinkhole growth trends.
    Type of Medium: Online Resource
    ISSN: 1869-9529
    URL: Article
    URL: Article
    DOI: 10.5194/se-9-1341-2018
    DOI: 10.5194/se-9-1341-2018-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2545676-3
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  • 3
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    Sinkholes, subsidence and subrosion on the eastern shore of the Dead Sea as revealed by a close-range photogrammetric survey
    Elsevier BV ; 2017
    In:  Geomorphology Vol. 285 ( 2017-05), p. 305-324
    Details
    In: Geomorphology, Elsevier BV, Vol. 285 ( 2017-05), p. 305-324
    Type of Medium: Online Resource
    ISSN: 0169-555X
    URL: Article
    DOI: 10.1016/j.geomorph.2017.02.006
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
    detail.hit.zdb_id: 2001554-9
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  • 4
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    Shear wave reflection seismic yields subsurface dissolution and subrosion patterns: application to the Ghor Al-Haditha sinkhole site, Dead Sea, Jordan
    Copernicus GmbH ; 2018
    In:  Solid Earth Vol. 9, No. 5 ( 2018-09-21), p. 1079-1098
    Details
    In: Solid Earth, Copernicus GmbH, Vol. 9, No. 5 ( 2018-09-21), p. 1079-1098
    Abstract: Abstract. Near-surface geophysical imaging of alluvial fan settings is a challenging task but crucial for understating geological processes in such settings. The alluvial fan of Ghor Al-Haditha at the southeast shore of the Dead Sea is strongly affected by localized subsidence and destructive sinkhole collapses, with a significantly increasing sinkhole formation rate since ca. 1983. A similar increase is observed also on the western shore of the Dead Sea, in correlation with an ongoing decline in the Dead Sea level. Since different structural models of the upper 50 m of the alluvial fan and varying hypothetical sinkhole processes have been suggested for the Ghor Al-Haditha area in the past, this study aimed to clarify the subsurface characteristics responsible for sinkhole development.For this purpose, high-frequency shear wave reflection vibratory seismic surveys were carried out in the Ghor Al-Haditha area along several crossing and parallel profiles with a total length of 1.8 and 2.1 km in 2013 and 2014, respectively. The sedimentary architecture of the alluvial fan at Ghor Al-Haditha is resolved down to a depth of nearly 200 m at a high resolution and is calibrated with the stratigraphic profiles of two boreholes located inside the survey area.The most surprising result of the survey is the absence of evidence of a thick (〉 2–10 m) compacted salt layer formerly suggested to lie at ca. 35–40 m depth. Instead, seismic reflection amplitudes and velocities image with good continuity a complex interlocking of alluvial fan deposits and lacustrine sediments of the Dead Sea between 0 and 200 m depth. Furthermore, the underground section of areas affected by sinkholes is characterized by highly scattering wave fields and reduced seismic interval velocities. We propose that the Dead Sea mud layers, which comprise distributed inclusions or lenses of evaporitic chloride, sulfate, and carbonate minerals as well as clay silicates, become increasingly exposed to unsaturated water as the sea level declines and are consequently destabilized and mobilized by both dissolution and physical erosion in the subsurface. This new interpretation of the underlying cause of sinkhole development is supported by surface observations in nearby channel systems. Overall, this study shows that shear wave seismic reflection technique is a promising method for enhanced near-surface imaging in such challenging alluvial fan settings.
    Type of Medium: Online Resource
    ISSN: 1869-9529
    URL: Article
    DOI: 10.5194/se-9-1079-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2545676-3
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  • 5
    Online Resource
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    Sinkholes and uvalas in evaporite karst: spatio-temporal development with links to base-level fall on the eastern shore of the Dead Sea
    Copernicus GmbH ; 2019
    In:  Solid Earth Vol. 10, No. 4 ( 2019-08-30), p. 1451-1468
    Details
    In: Solid Earth, Copernicus GmbH, Vol. 10, No. 4 ( 2019-08-30), p. 1451-1468
    Abstract: Abstract. Enclosed topographic depressions are characteristic of karst landscapes on Earth. The developmental relationship between depression types, such as sinkholes (dolines) and uvalas, has been the subject of debate, mainly because the long developmental timescales in classical limestone karst settings impede direct observation. Here we characterize the morphometric properties and spatio-temporal development of ∼1150 sinkholes and five uvalas formed from ∼1980 to 2017 in an evaporite karst setting along the eastern coast of the hypersaline Dead Sea (at Ghor Al-Haditha, Jordan). The development of sinkhole populations and individual uvalas is intertwined in terms of onset, evolution and cessation. The sinkholes commonly develop in clusters, within which they may coalesce to form compound or nested sinkholes. In general, however, the uvalas are not defined by coalescence of sinkholes. Although each uvala usually encloses several clusters of sinkholes, it develops as a larger-scale, gentler and structurally distinct depression. The location of new sinkholes and uvalas shows a marked shoreline-parallel migration with time, followed by a marked shoreline-perpendicular (i.e. seaward) growth with time. These observations are consistent with theoretical predictions of karstification controlled by a laterally migrating interface between saturated and undersaturated groundwater, as induced by the 35 m fall in the Dead Sea water level since 1967. More generally, our observations indicate that uvalas and the sinkhole populations within them, although morphometrically distinct, can develop near-synchronously by subsidence in response to subsurface erosion.
    Type of Medium: Online Resource
    ISSN: 1869-9529
    URL: Article
    URL: Article
    DOI: 10.5194/se-10-1451-2019
    DOI: 10.5194/se-10-1451-2019-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2545676-3
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  • 6
    Online Resource
    Online Resource
    Dynamics of hydrological and geomorphological processes in evaporite karst at the eastern Dead Sea – a multidisciplinary study
    Copernicus GmbH ; 2021
    In:  Hydrology and Earth System Sciences Vol. 25, No. 6 ( 2021-06-16), p. 3351-3395
    Details
    In: Hydrology and Earth System Sciences, Copernicus GmbH, Vol. 25, No. 6 ( 2021-06-16), p. 3351-3395
    Abstract: Abstract. Karst groundwater systems are characterized by the presence of multiple porosity types. Of these, subsurface conduits that facilitate concentrated, heterogeneous flow are challenging to resolve geologically and geophysically. This is especially the case in evaporite karst systems, such as those present on the shores of the Dead Sea, where rapid geomorphological changes are linked to a fall in base level by over 35 m since 1967. Here we combine field observations, remote-sensing analysis, and multiple geophysical surveying methods (shear wave reflection seismics, electrical resistivity tomography, ERT, self-potential, SP, and ground-penetrating radar, GPR) to investigate the nature of subsurface groundwater flow and its interaction with hypersaline Dead Sea water on the rapidly retreating eastern shoreline, near Ghor Al-Haditha in Jordan. Remote-sensing data highlight links between the evolution of surface stream channels fed by groundwater springs and the development of surface subsidence patterns over a 25-year period. ERT and SP data from the head of one groundwater-fed channel adjacent to the former lakeshore show anomalies that point to concentrated, multidirectional water flow in conduits located in the shallow subsurface (〈 25 m depth). ERT surveys further inland show anomalies that are coincident with the axis of a major depression and that we interpret as representing subsurface water flow. Low-frequency GPR surveys reveal the limit between unsaturated and saturated zones (〈 30 m depth) surrounding the main depression area. Shear wave seismic reflection data nearly 1 km further inland reveal buried paleochannels within alluvial fan deposits, which we interpret as pathways for groundwater flow from the main wadi in the area towards the springs feeding the surface streams. Finally, simulations of density-driven flow of hypersaline and undersaturated groundwaters in response to base-level fall perform realistically if they include the generation of karst conduits near the shoreline. The combined approaches lead to a refined conceptual model of the hydrological and geomorphological processes developed at this part of the Dead Sea, whereby matrix flow through the superficial aquifer inland transitions to conduit flow nearer the shore where evaporite deposits are encountered. These conduits play a key role in the development of springs, stream channels and subsidence across the study area.
    Type of Medium: Online Resource
    ISSN: 1607-7938
    URL: Article
    URL: Article
    DOI: 10.5194/hess-25-3351-2021
    DOI: 10.5194/hess-25-3351-2021-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2100610-6
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