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Sinkholes are the most abundant surface features in karst areas worldwide. Understanding sinkhole occurrences and characteristics is critical for studying karst aquifers and mitigating sinkhole‐related hazards. Most sinkholes appear on the land surface as depressions or cover collapses and are commonly mapped from elevation data, such as digital elevation models (DEMs). Existing methods for identifying sinkholes from DEMs often require two steps: locating surface depressions and separating sinkholes from non‐sinkhole depressions. In this study, we explored deep learning to directly identify sinkholes from DEM data and aerial imagery. A key contribution of our study is an evaluation of various ways of integrating these two types of raster data. We used an image segmentation model, U‐Net, to locate sinkholes. We trained separate U‐Net models based on four input images of elevation data: a DEM image, a slope image, a DEM gradient image, and a DEM‐shaded relief image. Three normalization techniques (Global, Gaussian, and Instance) were applied to improve the model performance. Model results suggest that deep learning is a viable method to identify sinkholes directly from the images of elevation data. In particular, DEM gradient data provided the best input for U‐net image segmentation models to locate sinkholes. The model using the DEM gradient image with Gaussian normalization achieved the best performance with a sinkhole intersection‐over‐union (IoU) of 45.38% on the unseen test set. Aerial images, however, were not useful in training deep learning models for sinkholes as the models using an aerial image as input achieved sinkhole IoUs below 3%. Plain Language Summary: Sinkholes are very common in areas with limestone rocks. Sinkholes can damage roads, buildings, and other infrastructure and sometimes even cost human lives. Sinkhole maps are needed for land use planning and hazard mitigation. Because sinkholes often occur in large numbers, often in the thousands, accurately mapping each of them manually is expensive and laborious. In this study, we applied deep learning, a form of artificial intelligence, to build computer models to automatically locate sinkholes from images created from elevation data. These models used the image segmentation technique to label every pixel in an image as either sinkhole or non‐sinkhole. We used images of elevation, slope, elevation gradient, and shaded relief as inputs to models. Model results suggested that deep learning offered a viable way to automatically locate sinkholes from elevation data. In particular, models using elevation gradient information performed the best. We also evaluated aerial imagery to train the models and found that aerial images were not useful in training deep learning models for sinkhole identification. Key Points: Image segmentation models using elevation and aerial images were trained to locate sinkholesModel's out‐of‐distribution generalization was assessedElevation gradient images provide the best input for training sinkhole segmentation models [ABSTRACT FROM AUTHOR]

To ensure the safe operation of roads, it is necessary to periodically monitor the condition of road surfaces. Lately, near‐surface geophysics methods have been actively used to solve such problems. The seismoacoustic methods that are used to diagnose road surfaces are typically dynamic methods based on the excitation of body or surface elastic waves in the road surfaces. The purpose of this work is to assess the possibilities of using elastic standing waves for diagnosing a hard road surface. This article presents the results of field experiments that demonstrate the possibility of detecting cavities under an asphalt pavement using flexural standing waves. Such waves, like vibrations of a membrane fixed or partially fixed at its edges, can be formed on the hard surface cover above the cavity as a result of exposure to acoustic noise. In this article, the accumulation of amplitude spectra of a large number of noise records was used to extract standing waves from the acoustic noise recorded on the surface of the pavement. It is shown that the joint visualization of the averaged spectra obtained by profile observations over the cavity makes it possible to confidently identify several modes of flexural standing waves. Based on the areal measurements, a map of the distribution of the amplitudes of one of the modes of flexural standing waves in the asphalt pavement over the cavity was constructed. At a qualitative level, this distribution is consistent with the results of computer simulations using the finite element method. The fact that, under the influence of acoustic noise in the pavement, the flexural standing waves are formed which are absent at other places indicates the absence of rigid contact at its lower boundary. Thus, the horizontal dimensions of the cavity can be estimated from the size of the area on which flexural standing waves are formed. In addition, the article shows that the analysis of vertical compressional (but not flexural) standing waves arising in the pavement under the influence of noise allows us to investigate the thickness of the pavement and to qualitatively assess the ratio of acoustic stiffness of the pavement and the underlying layer. [ABSTRACT FROM AUTHOR]

The composition and content of necessary engineering-geological research providing accident-free operation of buildings and constructions in karst areas are considered. These studies include karst hazard assessment and rational selection of karst protection measures. The results of the prognostic assessment of karst sinkhole formation possibility on the territory of about 4 hectares, allocated for construction of the first stage of the complex of residential buildings of different numbers of floors in the northwest of Moscow, are presented. The basis was the results of site investigations, during which, in particular, several dozen boreholes were drilled to uncover soluble rocks. Karst hazard assessment included an in-depth analysis of engineering-geological conditions of the future construction site and adjacent territories and took into account the possibility of the occurrence of karst sinkholes of different genetic types in this city area. When building forecasts and karst risk assessment, calculated methods of probabilistic and deterministic character were used, allowing to determine the necessary conditions and parameters of karst sinkhole formation in quantitative terms. The results of the karst hazard assessment were considered when selecting karst protection methods.

In the past several years, the high frequency of cave-in failures of urban roadways has posed a serious threat to the safety of traffic, pedestrians, and existing structures and facilities in China, and they have often led to fatalities, injuries, and significant economic losses. First, this study collates 379 cases to characterize roadway cave-in failures. Then the major causes associated with these events are classified, which includes damage and defects on preexisting underground structures and facilities, washout and erosion of roadway subgrade by seepage water, underground construction, loose subgrade, excessive lateral wall movement and through-wall leaking of deep excavations adjacent to roadways, and rapid decline in water table levels. Then four enormously influential failure cases are described as typical examples. Finally, the primary characteristics of the cave-in failures are discussed, including their temporal and spatial distributions, sizes, and morphologies, as well as the number of casualties and injuries involved. This review concludes that it is of paramount importance to inspect healthy conditions of aging underground structures and pipelines and to adopt or develop reliable measures to check unseen loose zones, voids, and cavities underneath urban roadways, in particular those adjacent to construction sites, with erodible subsurface conditions, or frequently subject to disturbing forces (seepage flow and vibration). [ABSTRACT FROM AUTHOR]

The presence of formations containing gypsum layers could enhance the formation of gypsum karst forms. The thickness of the gypsum layers and the quality of the mentioned beds influence the formation of such landforms. The Maroon plain is located in the folded zone of the Zagros Mountains in Kohgiluyeh and Boyer-Ahmad Province. The existence of the Gachsaran Formation and the occurrence of the karst phenomena (among which sinkholes are the most significant) in this plain have a very destructive impact on the roads, facilities, farmlands, residential units, and the reservoir of the Maroon Dam located in the plain. However, this phenomenon is not well-known and well-studied. In the present study, the karst evolution zoning map was prepared using the fuzzy model. To produce this map, ten environmental factors including the slope, slope direction, geology, distance from the Knick line, distance from the flow line, distance from the river, elevation, land use, climate, and the NDVI Index were used. The results of this study demonstrated that 55.2% of the study area was situated in the zero-risk zone because it was situated out of the Gachsaran Formation realm and lacked the gypsum layer. Also, 11.2% of the area was in the high-risk zone, 18.5% in the medium-risk zone, and 15.1% in the low-risk zone. Field observations and studying the zoning map indicated that the main factors influencing the karst evolution of this area were slope and streamlines which were superimposed on the gypsum layers. [ABSTRACT FROM AUTHOR]

Closed depressions such as sinkholes and pits can form through various subsurface processes, leading to similar surface expressions. This study analyzes closed depressions in eastern Galilee, Israel, to evaluate their potential origins. Ten depressions were surveyed, including shallow bowl-like forms and steep-walled pits. The terrain comprises faulted Cretaceous carbonates intruded by Early Pleistocene basalts dated to around 2.25 Ma. The circular morphology of the depressions and lack of ejecta indicate collapse into subsurface voids. Field evidence and geophysical data reveal a complex interplay of tectonic and volcanic factors. Some depressions appear to be structurally controlled by dilational normal faults, while others appear to be associated with volcanic features like dikes. Karst processes in the soluble carbonates likely contributed, most probably by hypogene dissolution related to magmatic fluids which may have enhanced void development. A dike identified within depressions suggests void formation through inflation and deflation of intrusions. Progressive collapse and erosion modified steep pits into shallow bowl-like depressions over time. Our results highlight the equifinality of closed depressions, wherein similar morphologies can arise through multiple subsurface processes. Unraveling this complexity has significance for interpreting pit craters on planetary surfaces using remote sensing. • Depressions and pits in karst terrains are not always of karstic origin. • Volcanic and tectonic processes can produce voids which form sinkholes by collapsing. • The eastern Galilee, Israel, presents an example of depressions and pits with complex origin. [ABSTRACT FROM AUTHOR]

Two successive disastrous earthquakes occurred on February 6, 2023 in the province of Kahramanmaraş of Türkiye. These earthquakes resulted in loss of more than 50.000 lives and several cases of serious damage to various engineering structures. Some roadways and railway and underpass tunnels were also damaged by the earthquakes as a result of heavy shaking as well as faulting. In addition, many rockfalls occurred at the portals of railway and roadway tunnels. The faulting caused quite severe damage at the railway tunnel near Ozan village. The concrete lining of the new Erkenek tunnels ruptured at several places. The damage in the new Erkenek twin tunnels may be related to mass movements caused by heavy ground shaking as well as an inclined geological structure together with low overburden next to a valley. Sinkholes of man-made and natural cavities occurred in several locations including urbanized areas. In this study, the authors describe the damage to underground structures by the doublet Kahramanmaraş earthquakes with some detailed analyses of Erkenek tunnels. Furthermore, the causes of the damages are described and their implications on the seismic design of underground structures are discussed. The observations indicated that underground openings crossing by faults and fracture zones may be enlarged to accommodate relative slips along faults and fracture zones. Furthermore, the ductility of support should be high in such zones in order to prevent brittle failure, which may have very disastrous effects. In addition to man-made underground structures, natural underground rock structures may be damaged or sinkholes may be caused by earthquakes as observed in the 2023 Kahramanmaraş earthquakes. The computational results clearly explain why the valley-side of one of the tunnels was more damaged compared to that of the mountain-side tunnel. It is also noted that some of the sinkholes in the earthquake region can be explained using some techniques available in literature. • The characteristics of the earthquakes and faulting are presented. • The characteristics of strong ground motions nearby damaged structures are presented. • The damage to underground structures and its level by faulting or strong ground motions are described. • The collapse and sinkholes occurred in Aydınbaba Park are analyzed using some available techniques. [ABSTRACT FROM AUTHOR]

Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel traverses spaced at 6.1 m (20 ft) intervals across a karst sinkhole site in Greene County Missouri. The acquired ERT data were processed as both 2D data and pseudo-3D data. Based on the correlation with the available core hole control, multichannel analysis of surface waves (MASW) data and field observations, it is concluded that the subsurface structure of the sinkhole is more reliably imaged on the pseudo-3D dataset than in the 2D dataset. The interpretation results of the pseudo-3D ERT indicated that the sinkhole developed at the intersection of three vertical solution-widened joint sets.

Salento Peninsula (Apulia, southern Italy) is characterised by many active sinkholes, which represent the main geological hazard. The stretch of coastline between the village of Casalabate and Le Cesine wildlife reserve is highly affected, with a system of dunes separating the low beach from extensive wetlands, which were subject to uncontrolled urban development after reclamation. The overall morphology is characterized by flat topography, whilst from a hydrogeological standpoint, the mixing of inland freshwater with advancing brackish water favours the higher aggressivity with respect to soluble rocks, and the development of enhanced dissolution (hyperkarst). The relict landscapes within the protected areas still allow for the recognition of actively occurring sinkholes, which cause damage to houses, the road network and infrastructures. In this article the case of Aquatina di Frigole is described, where in the last 15 years numerous sinkholes have formed, with the processes still in rapid evolution. Detailed surveys allow for to identification of the mechanisms of sinkhole formation (suffusion sinkholes), the deriving cluster, and the main hydrogeological links among the different water bodies in the area. Acquatina di Frigole provides an excellent natural laboratory to observe development and evolution of sinkholes, and their relationships with the stratigraphic and hydrogeological elements. [ABSTRACT FROM AUTHOR]

Many buried karst areas in Iran, and in other parts of the world have not yet been mapped using detailed geological or geophysical studies to delineate susceptibility to sinkhole development. The purpose of this paper is to investigate the possibility of using the results of hydrogeochemical analysis with routine measurements of physicochemical parameters to evaluate and detect areas prone to sinkhole develop. Sixteen spatial maps were prepared using analyzed data from 77 water samples from monitoring water wells in the Kabudar Ahang, Razan, and Qahavand (KRQ) sub-catchments of the Hamadan province, western Iran. By use of geographic information system tools 16 thematic maps for physicochemical parameters (EC, pH., TDS, and groundwater temperature), major cations (Ca2+, Mg2+, Na+, and K+), anions (HCO−3, SO42−, NO3−, and Cl−), and calcite, dolomite, gypsum, and partial pressure of CO2 saturation indices (SIC, SID, SIG, and SIpCO2) were prepared. It was hypothesized that the anomalies of each parameter concentration could be consistent with sinkhole prone areas. To evaluate this assumption, the area under the Receiver Operating Characteristic (ROC) curve was calculated by 100 points as a true sinkhole pixel (50 positive true) and non-sinkhole point (50 true negative). The areas under curve of ROC for these thematic maps were calculated for the 16 variables. Results show that the dolomite and calcite saturation indices (0.49 and 0.43, respectively) are poor indicators, whereas HCO−3 and pCO2 saturation indexes (0.83 and 0.78, respectively) are good indicators of sinkhole susceptibility in the study area. The result confirmed application of hydrogeochemical anomaly analyses and the ROC validation method in covered karst can be a useful tool for prediction of sinkhole prone zones forming in region, where sparse data are available. [ABSTRACT FROM AUTHOR]

This study investigated eight metal (Cu, Pb, Zn, Ni, Mn, Fe, Cr, Al) and one metalloid (As) amounts in the sediment of Meyil Sinkhole Lake. The findings obtained were compared with the limit values of sediment quality guidelines (SQGs) such as PEL (probable effect level), TEL (threshold effect level), ERL (effects range low) and ERM (effects range median). In addition its probable toxic effects were investigated via different sediment evaluation methods. As a result, the value of the metal concentrations tested was below the limit value. The contamination factor of all the metal(loid)s tested was found to be below 1 (𝐶𝐶𝑓𝑓 𝑖𝑖 <1). In other words, the accumulation level of all metal(loid) was found to be low. Also the mean ERM quotient (m-ERM-q) and mean PEL quotient (m-PEL-q) values revealed that there was no risk for the lake. The total toxic unit (Σ TU) method revealing the toxic effect of the metal(loid)s, also supported this result. In the light of all these data, the sediment of the lake was found to be clean in terms of investigated meta(loid). The accumulation relations of metals (loids) are also revealed by correlation analysis. The correlations between Zn-Pb and Fe were remarkable. [ABSTRACT FROM AUTHOR]

Meridional shifts of the North Atlantic Subtropical High (NASH) western edge create a dipole that drives hydroclimate variability in the southeastern United States and Caribbean region. Southwest displacements suppress rainfall in the southern Caribbean. Northwest displacements drive southeast United States and northern Caribbean drying. Projections for the 21st century suggest a more meridionally displaced NASH, which jeopardizes Caribbean island communities dependent on rain‐fed aquifers. While recent work indicates that Atlantic and Pacific Ocean‐atmosphere variability influenced the NASH during the instrumental period, little is known about NASH behavior and subsequent hydroclimate responses over longer timescales. To address this limitation, we developed a ∼6000‐years long rainfall record through the analysis of calcite raft deposits archived within sediments from a coastal sinkhole in the northeast Bahamas (Abaco Island). Increased (decreased) calcite raft deposition provides evidence for increased (decreased) rainfall driven by NASH variability. We use simulations from the Community Earth System Model to support this interpretation. These simulations improve our understanding of NASH behavior on timescales congruous with the reconstruction and suggest an important role for the state of the Pacific Ocean. Furthermore, model simulations and a compilation of regional hydroclimate reconstructions reveal that the NASH‐driven dipole dominates northern and southern Caribbean rainfall on centennial timescales. These results bring Holocene Caribbean hydroclimate variability into sharper focus while providing important context for present and future changes to regional climate. Additionally, this study highlights the need for improved future predictions of the state of the Pacific Ocean to best inform water scarcity mitigation strategies for at‐risk Caribbean communities. Key Points: Centennial‐scale hydroclimate variability in the Northern Bahamas is anti‐phased with mid‐late Holocene hydroclimate over Grenada and BarbadosEvidence is presented for a Caribbean hydroclimate dipole caused by meridional displacements of the North Atlantic Subtropical HighCalcite raft sedimentation in sinkholes and caves on carbonate landscapes offers new opportunities to investigate rainfall variability [ABSTRACT FROM AUTHOR]

Examples of the application of microgravity mehtod for the detection of potentially hazardous (empty) underground cavities caused by the collapse of coal mines are presented. Within these areas some alteration by previous remediation activity had occurred. This was not documented earlier and, therefore, such alteration was often unknown prior to the current investigations. We show a successful application of microgravity, leading to the detection of an empty cavity, in close proximity to where concrete injection was earlier performed. This was subsequently verified thorugh measurements in a borehole. In contrast, two other examples delivered results where the microgravity data, along with signals from other geophysical methods, led to the interpretation that subsidence resulting in the formation of sinkholes had been in‐filled, and in these situations the detection of more recent cavities was considered to be unreliable. These results point to the conclusion that microgravity interpretation of cavities is an effective approach, but the success of this approach may be compromised at sites where remediation activity has already occurred; in such situations the approach should be supplemented by other geophysical methods. [ABSTRACT FROM AUTHOR]

Loss of stability of shafts liquidated in the past is a frequent cause of sinkhole creation on the surface. This manuscript presents such a case study. The sinkhole was created shortly after intense rainfall, so it can be assumed that displacement of the rock material in the shaft took place, i.e. the phenomenon of suffusion. One of the research aims was to confirm the assumption about the displacement of rock material filling the shaft on the basis of selected methods of sinking forecasting. Ex post forecast sinkhole creation was conducted using two methods (Bell and finite element method). It was assumed that the material filling the shaft lowered itself to a height determined on the basis of the sinkhole and shaft dimensions. Both methods gave the same results, consistent with the literature. The manuscript also presents a short overview of technologies used for decommissioning shafts and assesses their effectiveness in terms of preventing sinkhole creation. These methods have been used since the nineteenth century until present times. Considering the suffusion phenomenon, the paper proposes a way to drain rainwater from the shaft area, which was another purpose of the work. The necessity to find and verify the ways to secure decommissioned shafts from water is indicated as an important future direction of research. [ABSTRACT FROM AUTHOR]

Konya, which is located within the Konya Closed Basin, is the most important agricultural production region in Turkey. The future of agriculture is threatened in this region due to the decline in groundwater levels and the intensive agricultural activities that require high water consumption and are not suitable to the climate conditions of the region. In addition to these parameters, the geological structure of Konya also poses various environmental problems such as land subsidence and sinkhole formation. This study aimed to investigate the causes of the land subsidence problem in Konya and its surroundings with the help of the interferometric synthetic aperture radar (InSAR) technique and auxiliary data, namely optic, Coordination of Information on the Environment (CORINE), and groundwater monitoring station data. In order to investigate the land subsidence in the study area, 58 Sentinel-1A images acquired between 2014 and 2018 were processed by using the small baseline subset (SBAS) technique. In addition, the time series derived from the SAR data was validated by a global navigation satellite system (GNSS) station located in the study area. The results revealed that severe land subsidence, some of which reached 75 mm/year, occurred in certain areas of the study area over a period of three and a half years. High consistency was found between the land subsidence and the groundwater level change observed in the region, with a cross-correlation of over 95%. Moreover, the temporal and spatial patterns of the cultivated area and urbanization, which are the main reasons for the consumption of groundwater in the region, were revealed using the optic data. [ABSTRACT FROM AUTHOR]

This paper provides simulated datasets for different versions of small-scale physical sinkhole models that are essential to understand the sinkhole formation rate. These physical models were used in experiments to monitor ground settlement or collapse due to leakage from an underground pipeline. The factors under consideration were the subsurface soil profile, pattern of water flow, and leakage position in the pipeline. The experimental results and statistical analysis showed that the subsurface soil strata conditions dominated the sinkhole occurrence mechanism, although other factors also contributed to the settlement. The results also showed that the subsurface soil comprising strata sandy clay, limestone, and bedrock (SC-LS-BR) dominates the sinkhole mechanism. The data are organized and formated in a useful structure. Specifically, the dataset is presented in terms of tables to illustrate the settlements in different soil profiles under various conditions. This analysis was then used to predict the sinkhole risk level under different conditions. The formulated dataset and the results can be considered in developing a sinkhole risk index (SRI) and identifying sinkhole risk areas.

Introduction: At present, the increase in the Earth's population has led to an increase in consumption, and an abnormal harvest of water and soil resources.MaydavoodPlain is a very fertile plain with rich water resources in the east of Khuzestan Province.In recent years, water contamination and sinkholehazards have happened in this plain.To date, very few environmental studies have been carried out on this plain. Material and methods: In this study, field and laboratory studies have been used to study the environmental hazards of the Maydavood Plain. During field studies, many sinkholes around the Maydavood Plain were identified and their dimensions were measured. Samples were collectedfrom the rocks and water resources of the region. The solubility test was carried outon gypsum samplesof Gachsaran Formationusing the circulation method. By using the Geographic Information System (GIS), isopotential map of sulfate and calcium ions was prepared for the plain. The ICP-OES analysis was used to determine the amount of heavy metals in water.GISwas also used toprepare theisopotential map ofheavy metals in the Maydavood Plain. Results and discussion: According to the office studies, the MaydavoodPlain is surrounded by Asmariand Gachsaran Formation and the bedrock of this plain is Gachsaran Formation that consists of gypsum and marlstones.All of thesinkholes are formed near the Gachsaran Formation. Results of the solubility test showed that gypsums had high solubility. Base on the isopotential map of sulfate and calcium ions, the amount of these ions were more concentrated around Sarelah and Dogacheh villages than other parts of the plain due to the dissolution of Gachsaran Formation gypsum. Hydrological studies showed that during the last 15 years, the groundwater level of the Maydavood Plain has decreasedabout 5 meters. In recent years, a few sudden sinkholes were formed, especially around Sarelah and Dogacheh villages due to the high solubility of Gachsaran Formation gypsum and a decrease in groundwater level. The type of these sinkholes a is cover collapse. Hydrochemical analysis of groundwater showed that 81, 31, 44, and 100 % of deep wellshad concentrations greater than permissible valuesof arsenic, iron, manganese,and nickel, respectively.Also, concentrations of vanadium in all of the deep wells were lower than the permissible value. Base on heavy metals isopotential map, the amount of heavy metals around of South MaydavoodPlain (Sufla) and MaydavoodVasati villages were higher than other parts of the plain. The source of heavy metals in the plain was the petroleum material pollution from oil spring existing. Conclusion: By controlling the excessive pumping of groundwater and using artificial nourishment, it is possible to prevent the decrease of groundwater quality and the formation of new sinkholes in the plain. Otherwise, the new sinkhole may be formed and cause damage. High concentrations of heavy metals in groundwater can be hazardous for the health of people living in this region. To avoid this hazard, it is suggestedto providethe drinking water for the MaydavoodPlain’s populationfrom another area with a permissible value ofheavy metals.

The paper concerns an analysis of causes of sinkholes in the area of the former mines located in the Upper Silesia (Poland). The conducted statistical analysis allowed to determine the share of some types of shallow excavations in the formation of sinkholes. Analyses covered the period from 1966 to 2003 and records of more than 300 sinkholes. The research team determined—on the basis of the considerations—that the factor that poses the greatest threat and contributes to the formation of sinkholes during the operation of the mine is shallow goafs. Other such factors are dog headings that have not been decommissioned yet. It can be assumed that they will also generate a significant number of collapses in mines that are no longer in operation. The transition into the state of cave-in of old and shallow dog headings is often caused by loss of load-bearing capacity of a wooden roof support which biodegrades. Collapses linked to these excavations may be predicted with the use of tools such as the method presented in the paper. [ABSTRACT FROM AUTHOR]

Subsidence can result from the collapse of underground cavities. The impact of such subsidence on existing structures and infrastructures is generally dramatic. Geosynthetic reinforcement (GSY) is an attractive mitigation solution that can be used to reduce this impact. This paper focuses on the mitigation solutions over existing cavities mainly on the GSY mitigation method. A large-scale physical model (1-g) is used to study the subsidence mechanisms and to estimate the efficacy of GSY for both cohesive and granular overlying soils. The results show that the presence of GSY reduces the ground movement due to the cavity progress toward surface, even under significant overload (traffic, localised foundation, etc.). The deformation of the GSY and the scenario for ground surface movement (subsidence or sinkhole) depend on both the soil type and overload intensity. The experimental results are compared to the analytical solutions proposed to design the GSY for cohesive and granular soils. In particular, the influence of the vertical stress distribution acting on the GSY is investigated. Different geometries of stress distribution are proposed for granular soils as a function of the loading mode (self-weight or localised overload). For cohesive soils, the action of the collapsed soil on the GSY sheet is found to be well estimated by considering the effect of a simplified system composed of two well localised punctual forces. The analytical and experimental results obtained are rather similar, proving the relevance of the analytical models in predicting the behaviour of reinforced soil layers taking into consideration the real stress distribution deduced from the experimental results. [ABSTRACT FROM AUTHOR]

Sinkholes are natural phenomena caused by the dissolution of limestone rocks due to the infiltration of acidic surface water. Initially, this infiltration creates voids, and then a sudden collapse occurs when the roof structure fails to support the weight load of the overlying deposits. In Algeria, a sinkhole occurred in February 2015 after a severe snowstorm, on an agricultural field near the city of El Ouldja (South-Eastern Setif). The sinkhole occurred only after the dissolution of a quaternary lacustrine limestone. This dissolution created a karstic cavity, covered by an alluvial deposit. These alluvium deposits progressively pulled down from the base to the top through a sediment removal phenomenon at the deep karstic cavity opening. The sinkhole is circular with 16-m diameter and 16-m deep. This phenomenon represents a risk for local populations living with the fear of a worsening and expansion of the existing cavity or the formation of new sinkholes under the same circumstances. This work aims at identifying high-risk zones in the entire site surrounding the karstic collapse phenomenon through geological analysis of the sinkhole walls as well as two geophysical methods, namely, electrical resistivity tomography (ERT) and electromagnetic induction (EMI). Results revealed the existence of developing superficial karst cavities, in the NNW and SSE part, beneath the Quaternary alluvium of the study area, bordered by a fracture network. Such structures are a natural risk that needs to be considered not only for agricultural land management, but also for rural construction. [ABSTRACT FROM AUTHOR]

Determining water level changes in lakes is significant for sustainable water supply planning, flood control, water resource management, and economic development with ecosystem sustainability. Trend analysis is a commonly used tool for detecting changes in hydrologic time series of quantities such as lake level, precipitation and temperature. Trend analysis of meteorological variables is very important for assessing the long-term changes in lake levels. This study examines long-term changes in the lakes in the Central Anatolia region of Turkey. Kızören and Timraş sinkhole lakes and Lakes Tuz and Beyşehir are some of the lakes located in this region. Changes in these lakes were examined along with changes in precipitation trends and human effects. The precipitation stations representing these lakes were determined using Thiessen polygons. In this study, the well-known nonparametric Mann–Kendall trend test (MK) was used. Before performing trend analysis, homogeneity and autocorrelation tests were applied for the time series. The standard normal homogeneity test (SNHT) was used to evaluate homogeneity. Trend analysis was performed before and after the change points the inhomogeneous series for the period of the homogeneous series. In addition, the modified Mann–Kendall method (MMK) was performed to examine the strong autocorrelations seen in the entire time series. The results showed that precipitation station data are homogeneous and lake levels are inhomogeneous. Trend analysis was performed by determining the change points for the inhomogeneous lakes. There were no significant trends after the change points for the Lake Tuz and Timraş sinkhole lake. These results are supported by the insignificant trends in precipitation stations. Contrary to the trend analysis results, the increase in the water level of Beyşehir Lake was determined to increment from the water transferred to the lake. The decrease in the water level of Kızören sinkhole was a result of anthropogenic effect rather than precipitation. The results confirm that lake levels have been affected by precipitation trends and anthropogenic effects. [ABSTRACT FROM AUTHOR]

Centurion is a fast developing area facing severe karstic sinkhole development. The area is predominantly underlain by fractured dolomite formations that include Oaktree, Monte Christo, Lyttelton, and Eccles of the Malmani Dolomite Group (~ 2600 and ~ 2500 Ma). Fractures of the underlying dolomite formations were investigated as one of the most influencing factors in karstic sinkhole formation using fieldwork mapping, petrology, and remote-sensing techniques (automated lineament extraction methods). Fieldwork results indicate that the study area has two prevalent fracture orientations trending N–S and ENE–WSW with average orientations of 178°/86° E and 073°/67° N. The fieldwork mapping results coincide with those acquired using remote-sensing techniques by automated extraction of lineaments from colour-shaded image and from four Sobel directional filtered images. Remote-sensing techniques indicate that there are extra two prevalent lineament directions; NE–SW and E–W in the study area and majority of the sinkholes develop in areas with high lineament density. Eccles, Monte Christo, and Oaktree dolomite formations exhibit a unidirectional fracture system while Lyttelton dolomite formation exhibit bidirectional fracture system. It is, therefore, concluded that (1) geological lineaments extracted using remote sensing and fractures present in the underlying dolomite formations play a significant role in controlling fluid circulation and thus influencing karstic processes such as dissolution, and therefore, (2) sinkhole development is primarily structurally controlled; however, it is exacerbated by anthropogenic activities due to the influence of water ingress. [ABSTRACT FROM AUTHOR]

Internal erosion is one of the major causes of the failure of hydraulic structures, road pavement, and the naturally deposited ground as well. Except suffusion and piping, contact erosion is also a type of internal erosion that can mostly occur at the foundation of embankment dams and dikes, in the road pavement and the alluvial fan deposited valley. This phenomenon occurs when the seepage flow exists at the interface of fine and coarse soil layers where fine particles are detached and transported through the voids of the coarse soil layer. Between 2013-2017 numerous sinkholes have been observed in Armala area of Pokhara valley in central Nepal. The locations of the sinkholes mainly observed at paddy fields in the alluvial fan deposit. The sinkhole affected area was investigated twice in the year 2015, 2016, and 2017. Based on the subsurface ground condition and the location of the hidden cavity, it assumed that an internal contact erosion occurred, and this phenomenon leads to the formation of subsurface hidden cavity and collapse sinkholes in the Armala area. Mechanics of contact erosion was studied in the laboratory by performing a series of small-scale parallel flow contact erosion test. The physical model of the experiment was prepared with the soil having a similar grain size and physical properties to the onsite granulometry. A cavity was observed at the interface when the fine soil (DL clay) is overlying the coarse sand. Also, the amount of discharged soil decreases with the increase of overburden pressure. [ABSTRACT FROM AUTHOR]

A sinkhole ecosystem, as a refuge for plant diversity, has been subjected to intensive exploitation, leading to ecosystem destruction of sinkholes in China. Understanding the responses of bryophyte distribution to destruction of the sinkhole environment are crucial to implementing protection measures for bryophyte diversity. • Haolong sinkhole in Guangxi Zhuang Autonomous Region of China, the third largest sinkhole in the world, was selected as the study area. The Wilson Shmida index was used to analyse bryophyte species diversity; a Generalized Linear Model (GLM) was used to reveal species vertical distribution of bryophytes, the Single and Multiple Species Distribution Models (SSDM, MSDM) were used for analysis of the relationship between bryophyte species distribution, environmental factors and heavy metals. • A total of 183 species from 74 genera in 36 families of bryophytes were collected from Haolong sinkhole, of which 26 species are endemic to China. Bryophyte species diversity was ranked in the order: agricultural section < forest section < grassland. In the vertical direction, bryophyte distribution was divided into point, disjunctive and continuous distributions using the GLM. The SSMA and MSDM indicated that bryophyte species of each of these three distributions can be divided into a temperature-slope zone, light-depth-pH-humidity zone, Pb (B)-Hg (B) zone and mixed heavy metals zone according to the effect of environmental factors and heavy metals such as As. • Environmental factors or heavy metals, such as As, in Haolong sinkhole effectively cooperate in bryophyte distribution. An effective way to protect bryophyte diversity, in particular species endemic to China in the sinkhole environment, is through education and involvement of the local villagers to minimize further damage to the sinkhole environment. [ABSTRACT FROM AUTHOR]

The technique of karst susceptibility assessment in the territory of Ust-Kishert village is presented. The environmental conditions of predominantly gypsum and carbonate–gypsum karst area are analyzed. The zonation map of karst cavities and crushed zones density is created. The distribution of the overlying soil geotechnical property values within the classes of different subterranean karst form density is carried out and presented in the form of histograms and distribution curves. The computer simulation of the soil stress condition is used to demonstrate that karst cavity affects the mechanical properties of the overlying soils and alters the initial stress in the soils. In our research, the anomalous values of the overlying soil geotechnical properties are applied as the indicators of the karst cavities and crushed zones location. The anomalous value intervals are determined by one-dimensional statistical analysis. The analysis of the overlying soil geotechnical properties is resulted in the integral model of karst susceptibility in the research area. [ABSTRACT FROM AUTHOR]

This study addresses mechanical models of sinkhole formation and their criteria obtained via simulation test. Sinkholes are a common geohazard and are widely distributed throughout the world. Previous studies suggest that sinkhole formation is the result of complex interactions among geological conditions, with one or more factors triggering occurrence of sinkholes. We suggest that the existence of a void caused by soil loss is the premise of this issue. Therefore, we present soil loss is the mechanism of sinkhole formation in soils in this paper. Soil loss is caused by the interaction between groundwater and soils in nature. This interaction includes the groundwater condition and the characteristics of soils. In this study, we considered three types of groundwater conditions and two types of soils to discuss the mechanical model of sinkholes. There are three models of sinkhole formation in soils: the disintegration model in vadose zone, the seepage erosion model in unconfined aquifer, and the hydraulic fissures model in confined aquifer. A disintegration apparatus was designed to simulate the disintegration process and to obtain the criteria parameters of water content. Circular pipe flow equipment was designed to simulate the seepage erosion process to obtain the criteria parameter of groundwater velocity. The mechanical model of sinkholes in the confined aquifer was the hydraulic fissures model. The hydraulic equipment was designed to simulate the hydraulic fissure process to measure the criteria parameter of water pressure. [ABSTRACT FROM AUTHOR]

Empirical predictions of discharge rates for dry non-cohesive grains are commonly based on the Beverloo law (Chem Eng Sci 15:260–269, 1961). The present work extends this practical configuration to submerged and cohesive cases to investigate the flow behavior of granular media with applications in the geophysical process of sinkhole formation. The analysis of the hydrostatic collapse of soil in the presence of underground conduits is performed with a 2D GPU-parallelized simulation coupling the lattice Boltzmann method and the discrete element method to describe the fluid and the solid phases, respectively. The discharge rate of a large submerged granular sample is analyzed by varying orifice sizes and inter-particle cohesion strengths. For the submerged cohesionless case, we first study the revisited Beverloo relationship that includes the terminal velocity of a single falling particle in the fluid, proposed in the experimental work of Wilson et al. (Pap Phys 1307: 2812, 2014). We consistently take into account the interstitial fluid with an effective orifice size smaller than in the dry case. Then, the additional contribution of grain cohesion is examined. Our main finding is that the empirical prediction remains valid provided that the orifice cutoff increases with cohesion. Finally, the evolution of fluid pressure during the discharge, at the vicinity of the orifice, is studied and favorably compared with the recent experimental study of Guo et al. (Granul Matter 19(3): 1–8, 2017). By considering the pressure drop around the orifice as a driven-term, we succeed in predicting the solid flow rate with a similar Beverloo approach. [ABSTRACT FROM AUTHOR]

Reactivation of an inception doline shaft system through anthropogenic actions, precipitation, and possibly seismic activity induced subsidence in a hospital emergency room that was under construction in State College, PA. The convergence of Tropical Storm Lee and Hurricane Irene is interpreted to have caused the building's brick edifice to fall and induce vertical shifts in the reinforced concrete entrance floor slab. Microgravity mapping of the existing hospital emergency room entrance; the emergency room building under construction; and the parking lot in front of the emergency room entrance documented the presence of a doline shaft system (i.e., inter-connected sinkhole). Groundwork for the construction of the new emergency room included grading and leveling of the property. Surface water runoff entered the construction site from a parking lot that sloped toward the addition and to a non-functioning stormwater inlet. The grading for the new construction exposed an open fracture for surface runoff. Subsequent channeling of surface water to the conduit provided drainage for surface runoff, but it also initiated subsidence throughout the existing structure and the addition that was under construction. Engineering rehabilitation included a limited mobility (LM) grout program to plug subsoil fracture karren drainage systems and stabilize the surface. Drilling progressed in four stages, initially focusing on areas of greatest subsidence. In total, 60 injection points were completed to a mean depth of 24 m below grade in an area measuring approximately 370 m2. During LM grouting, 867 m3 of a sand-and-cement grout mixture were injected to stabilize the area. [ABSTRACT FROM AUTHOR]

The advances in the expanse of image sensors have made it conceivable to make high-resolution picture sensors easily accessible. The amelioration of wireless interactive media sensor networks are found to be greatly increased due to the day to day usage of cameras, microphones and smart devices. A secured multi-hop routing mechanism is addressed in surveillance areas which could be incorporated to the multimedia sensors that are capable of peruse the detected data comprises of recorded images and videos. Also, malevolent sensor hubs could be interjected into the vigilance area in an untrusted environment. In this contemplated venture, a novel lightweight trust decision-making framework is accomplished for QoS clustering to give secure routing in both intercluster and intracluster communication. A quantifiable aberrant trust value is the variable determined by the Cluster Head (CH) for its Cluster Member (CM) inside the cluster. The LEACH (Low Energy Adaptive Clustering Hierarchy) protocol is adopted for group formation and also for the exchange of the trust values among the master nodes, member nodes and Base station. In this way, the correspondence overhead, likelihood of dynamic assaults for example sinkhole and black hole assaults mount by eavesdroppers can be reduced by maintenance of trust values by cluster heads rather than cluster members. Besides, in wireless streaming video sensor networks this approach authorizes us to predict and counteract malicious untrusted and flawed nodes. Simulation results using NS-2 is examined and the suggested trust decision-making model escalates the dependability, elasticity and low memory aloft in comparison with the current trust models adopted for wireless video sensor network security. [ABSTRACT FROM AUTHOR]

Road subsidence and sinkhole failures due to shallow cavities formed by defective water main have increased in recent decades and become one of the important research topics in geotechnical engineering. The present paper numerically studies the stability and its associated failure mechanism of ellipse-shaped cavity above defective water mains using the finite element limit analysis technique. For a wide range of geometrical parameters, the pressure ratio method is used to formulate the stability solutions in both blowout and collapse scenarios. Even though there is no published solution for elliptical cavities under blowout failure conditions, the obtained numerical results are compared with available circular solutions. Several conclusions are drawn based on the failure mechanism study of the various ellipse shape transformations in this study, whilst design charts and equations proposed for practical uses.

The Jahani Salt Diapir (JSD), with an area of 54 km2, is an active diapir in the Simply Folded Belt of the Zagros Orogeny, in the south of Iran. Most of the available studies on this diapir are focused on tectonics. The hydrogeology, schematic model of flow direction and hydrochemical effects of the JSD on the adjacent water resources are lacking, and thus, are the focus of this study. The morphology of the JSD was reevaluated by fieldwork and using available maps. The physicochemical characteristics of the springs and hydrometric stations were also measured. The vent of the diapir is located 250 m higher than the surrounding glaciers, and covered by small polygonal sinkholes (dolines). The glacier is covered by cap soils, sparse trees and pastures, and contains large sinkholes, numerous shafts, several caves, and 30 brine springs. Two main groups of caves were distinguished. Sub-horizontal or inclined stream passages following the surface valleys and vertical shafts (with short inlet caves) at the bottoms of nearly circular blind valleys. Salt exposure is limited to steep slopes. The controlling variables of flow route within salt diapirs are the negligible porosity of the salt rocks at depth more than about ten meters below the ground surface and the rapid halite saturation along the flow route. These mechanisms prevent deep cave development and enforce the emergence points of brine springs with low flow rates and small catchment area throughout the JSD and above the local base of erosion. Tectonics do not affect karst development, because the distributions of sinkholes and brine springs show no preferential directions. The type of spring water is sodium chloride, with a TDS of 320 g/l, and saturated with halite, gypsum, calcite and dolomite. The water balance budget of the JSD indicates that the total recharge water is 1.46 MCM (million cubic meter)/a, emerges from 30 brine springs, two springs from the adjacent karstic limestone, and flows into the Firoozabad River (FR) and the adjacent alluvium aquifer. The FR cuts through the northern margin of the salt diapir, dissolving the glacier salts at the contact with JSD, increasing the halite concentration of the 17.7 MCM/a of the FR from 100 mg/l to 12,000 mg/l. This is a permanent process because the active glacier flows rapidly down the steep slopes into the river gorge from the nearby vent. The possible relocation of the FR channel would enhance the FR water quality, but disrupt the natural beauty of the diapir.

The significance of intra-mountain valleys to infrastructure and human settlements and the need to mitigate the geo-hazard affecting these assets are fundamental to the economy of Italian alpine regions. Therefore, there is a real need to recognize and assess possible geo-hazards affecting them. This study proposes the use of GIS-based analyses to construct a sinkhole susceptibility model based on conditioning factors such as land use, geomorphology, thickness of shallow deposits, distance to drainage network and distance to faults. Thirty-two models, applied to a test site (Enemonzo municipality, NE Italy), were produced using a method based on the Likelihood Ratio (λ) function, nine with only one variable and 23 applying different combinations. The sinkhole susceptibility model with the best forecast performance, with an Area Under the Prediction Rate Curve (AUPRC) of 0.88, was that combining the following parameters: Nearest Sinkhole Distance (NSD), land use and thickness of the surficial deposits. The introduction of NSD as a continuous variable in the computation represents an important upgrade in the prediction capability of the model. Additionally, the model was refined using a kernel density estimation that produced a significant improvement in the forecast performance.

Evaluation of karst hazards benefits from the integration of different techniques, methodologies and approaches. Each one presents a different signature and is sensitive to certain indicators related to karst hazards. In some cases, detailed analysis permits the evaluation of representativeness either from isolated approaches or by means of integrated analyses. In this study, we present the evaluation of an area with high density of karstic collapses at different evolutionary stages through the integration of surficial, historical, geomorphological and geophysical data in order to finally define the evolutionary model for karst activity development. The obtained dataset permits to identify different steps in sinkhole evolution: (i) cavities and open sinkholes, (ii) filling of these cavities, with materials having different signatures, (iii) the progression from collapses to subsidence sinkholes and (iv) enlargement through collapses in marginal areas of previous sinkholes. The presence of different stages of this evolutionary model permits to determine their own signatures that can be of application in contexts where analysis cannot be so systematic and also to evaluate the definition of the marginal areas of previous sinkholes as the most hazardous sectors.

The present research focuses on the definition of a novel methodology for sinkhole risk assessment above shallow salt mines. The research were carried out on the area above the salt mine, a World Heritage site. The study of vertical stresses on the basis of a theoretical state of rock mass deformation in the area of test chambers was performed. Furthermore, the risk of chamber collapse due to ventricular stress exceeding the limit specified in the zone were calculated based on the arch pressure theory. The final stage of the research consists of spatial analysis that leading to the identification of chambers potentially influenced by other risk factors. The research shown in the article strongly suggests that combined spatial analysis with analysis may lead to reliable sinkhole risk assessment methodology.

The unexpected collapse of land surface due to subsidence is one of the most significant geohazards that threatens human life and infrastructure. Kabudrahang and Famenin are two Iranian plains experiencing several sinkholes due to the characteristics of the underground soil layers and extreme groundwater depletion. In this study, space-based Synthetic Aperture Radar images are used to investigate the ground displacement behavior to examine the feasibility of Sentinel-1 data in detecting precursory deformation proceeding before the sinkhole formation. The selected sinkhole occurred in August 2018 in the vicinity of Kerdabad village in Hamedan province with a 40 m diameter and depth of ~40 m. Time series of the European constellation Sentinel-1 data, spanning from January 2015 to August 2018, is analyzed, and the results revealed a 3 cm annual subsidence (–3 cm/year) along with the line-of-sight direction. Time-series analysis demonstrated that the driving mechanism of the sinkhole formation had a gradual process. Displacement of persistent scatterers (PSs) near the cave area had an acceleration by approaching the sinkhole formation date. In contrast, other areas that are far from the cave area show linear subsidence behavior over time. Additionally, the one-kilometer deformation profile over the cave area indicates a high subsidence rate precisely at the location where the sinkhole was formed later on 20 August 2018.

Salento Peninsula (Apulia, southern Italy) is characterised by many active sinkholes, which represent the main geological hazard. The stretch of coastline between the village of Casalabate and Le Cesine wildlife reserve is highly affected, with a system of dunes separating the low beach from extensive wetlands, which were subject to uncontrolled urban development after reclamation. The overall morphology is characterized by flat topography, whilst from a hydrogeological standpoint, the mixing of inland freshwater with advancing brackish water favours the higher aggressivity with respect to soluble rocks, and the development of enhanced dissolution (hyperkarst). The relict landscapes within the protected areas still allow for the recognition of actively occurring sinkholes, which cause damage to houses, the road network and infrastructures. In this article the case of Aquatina di Frigole is described, where in the last 15 years numerous sinkholes have formed, with the processes still in rapid evolution. Detailed surveys allow for to identification of the mechanisms of sinkhole formation (suffusion sinkholes), the deriving cluster, and the main hydrogeological links among the different water bodies in the area. Acquatina di Frigole provides an excellent natural laboratory to observe development and evolution of sinkholes, and their relationships with the stratigraphic and hydrogeological elements.