early stage sinkhole formation in the acque albule basin of central italy from geophysical and geochemical observations abstract sinkhole occurrence along the tyrrhenian margin of the central apennines is of great importance for applied research land management and civil protection this study reports on gps altimetry magnetic gravity geoelectric seismic and soil gas measurements of a rapidly developing sinkhole near the guidonia military airport the measurements revealed an elliptical 2 m depression elongated 220 m in the nne ssw direction with the minor axis of 110 m in the spring of 2013 two vertical cavities formed in the eastern and northeastern flanks of the depression whose depths and shapes are rapidly evolving with the formation of widespread fracturing along the same side the geophysical observations image the developing sinkhole to a depth of some 50 m the presence of the travertino lithotype around the depression down to at least 40 m and the lack of this lithotype below the lowered area the sinkhole s evolution appears to be structurally controlled by local and regional faulting these results are useful for designing further geophysical geotechnical and geochemical studies to monitor the sinkhole s evolution and to assess the hazard it presents in densely urbanized area

mechanics of upward propagation of cover collapse sinkholes cover collapse sinkholes occur by failure of the walls of a soil void above cavernous bedrock i examine conditions for failure in compression by crack propagation and coalescence and for failure by sloughing in which pore water pressure produces a net tension perpendicular to the wall of the void compressive failure without relaxation of stress does not explain observed long term stability of thick soils nor failures in thin residual soils if stress relaxation occurs with compressive failure soil voids tend to stabilize and sinkholes are not predicted sloughing failure is not predicted for steady state pore pressure fields even for a perched water table at the surface over a drained void transient pore pressure conditions that could produce sloughing may result from 1 rapid drawdown causing soil consolidation and transient high pore pressure gradients 2 approach of a wetting front in unsaturated soil with high permeability behind the front 3 dissolution of air from bubbles in the soil and exsolution near the void producing a low permeability zone near the void

impacts of karst paleo sinkholes on mining and environment in northern china the karst paleo sinkhole is a special geological structure widely found in the coal measures of northern china some paleo sinkholes have high permeability and connectivity making them excellent connectors between the karst aquifer and the coal seam consequently during coal extraction disastrous water inrushes take place frequently which cause severe loss not only in mine submersions and personnel casualties but also in environmental quality locations and the geological and hydrogeological characteristics of paleo sinkholes in northern china are presented in situ drilling and excavation results show that paleo sinkholes have different hydrogeological behaviors in different regions and in different mines based on observed data mining induced strata failure in the seam floor is analyzed the existence of paleo sinkholes increases the floor strata failure zone numerical simulation then is adopted to model coal mining with the effects of both the paleo sinkholes and the water pressure in the confined aquifer analyses of the simulation conclude that the paleo sinkhole induces the increase in the strata failure and deformation these make water inrushes more likely to happen

recovery of undisturbed highly fractured bench scale 30 cm diameter drilled samples for laboratory investigation investigation of the hydraulic parameters of fractured rock in the laboratory is often undertaken on a small scale sample diameter to 10 cm due to the difficulty of recovering undisturbed highly fractured rock samples usually such samples contain only one or at the most two discrete fractures when investigating the hydraulic or mechanical parameters important for geotechnical applications e g large scale triaxial tests it is necessary to have an understanding of the integrated effects of the fractures forming the fracture networks in this paper a method is presented whereby undisturbed samples with a diameter of 30 cm were recovered from a highly fractured porous rock mass and prepared for investigation of the fracture network properties in a laboratory most of the samples recovered contained several differently orientated fractures forming an interconnected network the undisturbed nature of the recovered samples allows the hydrogeological and geotechnical characteristics of the fracture network to be investigated

prediction of undrained sinkhole collapse sinkholes are surface depressions or shafts resulting from the collapse of a submerged cavity in soil the cavities that lead to sinkholes form as a result of underlying geology in limestone areas or as a result of human activity such as mining or leakage from a sewer the formation of sinkholes is often sudden and can lead to extensive damage and loss of life especially in urban areas much of the literature on the subject of sinkhole formation is empirical in nature often being associated with specific locations this paper presents the results of a study using numerical modeling of the undrained stability of the submerged cavities that lead to sinkhole formation finite element limit analysis techniques using programs developed at the university of newcastle are used to obtain upper and lower bound values of a suitable load parameter which bracket the exact solution the results are compared to analytical solutions both from literature and derived independently

el cuchillo seismic sequence of october 2013 july 2014 in the burgos basin northeastern mexico hydraulic fracturing or reservoir induced seismicity

management and mitigation of sinkholes on karst lands an overview of practical applications when karst lands are developed for residential or commercial purposes sinkholes are to be properly managed or mitigated this paper discusses various types of sinkholes and their possible formation mechanisms presents some guidelines for sinkhole management and summarizes several engineering measures for sinkhole remediation because a sinkhole is often not an isolated feature but a component of an integrated groundwater and surface water system knowledge of the sinkhole geology and hydrology is essential in selection of the proper management tools and remediation options adverse effects including flooding additional sinkholes and groundwater contamination can result from poorly managed or improperly repaired sinkholes

origin and morphology of limestone caves limestone caves form along ground water paths of greatest discharge and solutional aggressiveness flow routes that acquire increasing discharge accelerate in growth while others languish with negligible growth as discharge increases a maximum rate of wall retreat is approached typically about 0 01 0 1 cm yr determined by chemical kinetics but nearly unaffected by further increase in discharge the time required to reach the maximum rate is nearly independent of kinetics and varies directly with flow distance and temperature and inversely with initial fracture width discharge gradient and pco2 most caves require 104 105 yr to reach traversable size their patterns depend on the mode of ground water recharge sinkhole recharge forms branching caves with tributaries that join downstream as higher order passages maze caves form where 1 steep gradients and great undersaturation allow many alternate paths to enlarge at similar rates or 2 discharge or renewal of undersaturation is uniform along many alternate routes flood water can form angular networks in fractured rock anastomotic mazes along low angle partings or sponge work where intergranular pores are dominant diffuse recharge also forms networks and spongework often aided by mixing of chemically different waters ramiform caves with sequential outward branches are formed mainly by rising thermal or h2s rich water dissolution rates in cooling water increase with discharge co2 content temperature and thermal gradient but only at thermal gradients of more than 0 01 c m can normal ground water co2 form caves without the aid of hypogenic acids or mixing artesian flow has no inherent tendency to form maze caves geologic structure and stratigraphy influence cave orientation and extent but alone they do not determine branch work versus maze character

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

true triaxial loading apparatus and its application to coal outburst prediction two generations of true triaxial loading ttal apparatuses are presented first generation apparatuses were intended primarily for true stress state imitation in rock or mineral specimens advanced second generation installations are designed to provide precise measurements in any stress and simulation of rock outburst at sudden relief of one sample face both ttal apparatuses can apply pressure up to 250 mpa corresponding to earth depth about 10 000 m independently along each of three axes experimental results are given on effect of absorbed water on ultimate state in coal as well as adsorbed methane influence on simulated coal outbursts

engineering geology and ground collapse mechanism in the chengchao iron ore mine in china abstract the engineering geological and hydrogeological conditions in the eastern mining area of the chengchao iron mine are analyzed in detail the results are combined with the results of site investigations and in situ monitoring data allowing the characteristics of the ground surface collapse events to be summarized the mechanism by which ground surface collapse is induced by underground orebody extraction or de watering activity was then investigated the results show that the ground surface in the mining areas experienced three collapse processes karst collapse mixed collapse and mining induced collapse karst collapse sinkholes were found during the construction stage of the mine and are generally formed in the marble part of the marble granite contact zone these sinkholes show a bead on a string distribution and lines connecting their centers are consistent with the strike of the marble such sinkholes are mainly formed due to changes in the dynamic conditions of groundwater caused by de watering activity furthermore the development level of the collapse mainly depends on the location and scale of the karst caves within the marble mixed collapse occurs in the initial mining stage and mainly results from the combined effect of underground orebody excavation and de watering activity mining induced ground surface collapse pits mostly develop in the diorite and hornstone and generally show a zonal distribution along the strike of the orebodies from east to west mining induced collapse occurs in the form of chimney caving first a caved pipe is formed where the rock masses above the caved zone are highly fractured then the rock masses around the caved pipe gradually cave and finally a large caved zone is formed above the mined out area mixed collapse is of particular interest as it is a peculiar type of subsidence involving the superposition of collapse processes related to both mining and karst cavities and it can provide some instructive insight into the collapsing behavior of the ground surface

natural and induced sinkholes of the obruk plateau and karapinar hotamis plain turkey abstract the number of sinkholes locally known as obruks has increased rapidly in recent years near karapinar located in the semi arid konya closed basin in central anatolia nineteen sinkholes have formed in the last 33 years 1977 2009 as a result of the collapse of cavity roofs in the neogene lacustrine limestone in the obruk plateau and beneath quaternary lake sediments in the karapinar hotamis plain of these 13 have formed within the past 4 years 2006 2009 the obruk plateau takes its name from the presence of several hundred paleo sinkholes which formed as a result of natural processes during the quaternary period more recently human activity has induced the formation of new sinkholes which presents a hazard to life and property changing agricultural patterns have led to the opening of thousands of deep wells in recent years and increased water pumping currently exceeds the sustainable yield of the aquifer thus the formation of sinkholes has been triggered by a combination of natural and human causes the groundwater level has dropped almost 24 m in the vicinity of karapinar during the last 26 years 1983 2008 approximately 8 m of this drop occurred within the 4 years prior to the study 2005 2008 legally binding precautions must be taken to prevent further water table decline in order to decrease sinkhole formation within the basin in the years to come

mechanism and mechanical model of karst collapse in an over pumping area through geological investigation of karst collapses at zaozhuang city china it was found that the mechanism of karst collapse in areas of excess water extraction is characterized by a seepage effect and that the seepage pressure effect is the initial factor that induces karst collapse the causation mechanisms for karst collapse can be divided into two phases the inter collapse phase and the surface collapse phase therefore based on the limit equilibrium theory this paper has established mechanical models for the surface collapse phase and determined values for the stability of the arch formed by the soil hole in an inter collapse phase in addition an evaluation of a karst collapses at zaozhuang city china was completed using mechanical models the results show that the mechanical models agree with the theory of karst collapse at zaozhuang city thus it is proved that the karst collapse models can be used for the evaluation of karst collapse in areas that are over pumped

characteristics detection and prevention of karst sinkholes a case study in laiwu iron ore mine areas shandong province china karst related sinkholes are globally recognized geohazards that can be triggered by mining activities totally 136 sinkholes have occurred in the laiwu iron ore mine area of shandong province china at the surface the sinkholes are mostly round or oval shaped most are ceiling collapse sinkholes and they have caused road and building damage destruction of farmland connection of surface and ground water and groundwater contamination based on analysis of characteristics on karst sinkhole geological and hydrogeological conditions the proposed key factors of the karst collapse in the study area include soil characteristics degree of karst development in soluble rocks faults folds groundwater dynamic conditions and human engineering and mining activities a 300 m long 40 m wide and 25 m high cavern was identified with high density electrical resistivity imaging complex solutions were proposed to mitigate karst collapse in the iron ore mining area

application of matrix analysis in delineating sinkhole risk areas along highway i 70 near frederick maryland sinkhole collapse in the area of maryland interstate 70 i 70 and nearby roadways south of frederick maryland has been posing a threat to the safety of the highway operation as well as other structures the occurrence of sinkholes is associated with intensive land development however the geological conditions that have been developing over the past 200 million years in the frederick valley control the locations of the sinkholes within an area of approximately 8 km 2 138 sinkholes are recorded and their spatial distribution is irregular but clustered the clustering indicates the existence of an interaction between the sinkholes the point pattern of sinkholes is considered to be a sample of a gibbsian point process from which the hard core strauss model is developed the radius of influence is calculated for the recorded sinkholes which are most likely to occur within 30 m of an existing sinkhole the stochastic analysis of the existing sinkholes is biased toward the areas with intensive land use this bias is adjusted by considering 1 topography 2 proximity to topographic depressions 3 interpreted rock formation 4 soil type 5 geophysical anomalies 6 proximity to geologic structures and 7 thickness of overburden based on the properties of each factor a scoring system is developed and the average relative risk score for individual 30 m segments of the study area is calculated the areas designated by higher risk levels would have greater risk of a sinkhole collapse than the areas designated by lower risk levels this risk assessment approach can be updated as more information becomes available

fluid injection and seismic activity in the northern montney play british columbia canada with special reference to the 17 august 2015 mw 4 6 induced earthquake in this article we analyzed the recent seismic activity in the northern montney play of british columbia in 2015 and its connection with fluid injection hydraulic fracturing and long term injection of gas and wastewater disposal in the region the earthquake sequence used in this study includes 676 events from 3 october 2014 to 31 december 2015 from the progress energy earthquake catalog with moment magnitude as small as 1 spatial and temporal correlation of seismic activity with the fluid injection in the region revealed that these events are better correlated with hydraulic fracturing correlation coefficient of 0 17 at confidence level close to 99 7 with a lag time between 0 and 2 days than other types of injection using the double difference relocation technique we obtained depth constraints for some of the events for which supplementary industry provided waveforms were available the depths of these events range from 0 5 to 2 5 km and are mostly constrained above the target zone where hydraulic fracturing was taking place the best fit moment tensor solution for the event on 17 august 2015 gives a moment magnitude of 4 6 and a predominantly thrust mechanism in the northwest southeast direction with a shallow focal depth of 4 km this is consistent with that obtained through double difference relocation for this event 1 3 km given the depth uncertainty of the moment tensor inversion electronic supplement 1 tables of injection volumes and seismicity parameters and figure of monthly distribution of seismic events and location of fluid injection sites in the vicinity of the 17 august 2015 m w 4 6 event 1 http www bssaonline org lookup suppl doi 10 1785 0120160175 dc1

late holocene episodic displacement on fault scarps related to interstratal dissolution of evaporites teruel neogene graben ne spain abstract the mio pliocene formations of the turolian type section teruel graben spain have sagged due to dissolution of the underlying triassic evaporites generating a 1 7 km long monocline and accompanying synform with 130 m of structural relief the crest of the monocline is affected by a graben that counterbalances the shortening caused by passive bending in the adjacent syncline this graben is controlled by a master synthetic fault and a swarm of antithetic and synthetic faults with a conspicuous geomorphic expression after acquiring ground penetrating radar gpr profiles three trenches were excavated in depressions associated with uphill facing fault scarps to our knowledge these are the first trenches excavated across faults caused by deep seated dissolution of evaporites the geometrical relationships observed in two trenches indicate late holocene episodic displacement as many as 3 events some of the parameters estimated for the investigated faults are clearly different from those expectable for tectonic faults in this intraplate area they include high apparent vertical slip rates 0 6 1 mm yr low average recurrence of faulting events 1 2 2 ka and very high displacement per event values 65 cm for surface ruptures less then 200 m long our findings suggest that considering evaporite collapse faults as creeping structures is not a reliable criterion to differentiate between tectonic faults seismogenic and dissolution induced gravitational faults nonseismogenic

subsidence rates and urban damages in alluvial dolines of the central ebro basin ne spain in the central ebro basin alluvial dolines develop on quaternary materials overlying neogene evaporites this process is very active analysing aerial photographs of different years important differences can be observed since the 1970s when the urbanisation of the area took place karst processes have damaged many buildings and infrastructures from the dates of construction and the repair of a number of buildings and pavements we calculate subsidence rates 12 120 mm year moreover we decided to monitor for around 4 years three dolines developed on urban areas to determine their subsidence behaviour a water level device with an error of 2 3 mm was utilised for this purpose the subsidence rates so obtained are 64 5 39 and 21 mm year which fit with the previous data from repaired zones

a preliminary sinkhole raveling chart abstract sinkholes are a major geohazard in karst areas where soluble carbonate bedrock exists downward seepage resulting from the groundwater recharge continuously erode cover soils into cavities within the underlying bedrock resulting in raveling of cover soils identifying these raveled soils or zones is critial in preventing and mitigating the sinkhole collapse in this study a proof of concept was performed to demonstrate the concept of a sinkhole raveling chart that can quantify the severity levels of raveling the raveling chart is constructed based on cone penetration test cpt data collected through multiple sinkhole active sites in central florida a preliminary analysis e g data preparation grouping and zoning was carried out to construct the prototype sinkhole raveling chart this prototype raveling chart as a function of tip resistance qc and sleeve friction fs could delineate not only the raveled and non raveled zones but also the areas that correspond to different levels of raveling severity

evaporite karst processes landforms and environmental problems evaporite karst is widespread but relatively unknown when compared with carbonate karst this special issue addresses that lack of familiarity evaporite rocks have much higher solubilities and faster dissolution rates than carbonate rocks and they also commonly have lower mechanical strengths and more ductile reheologies many of these factors are dependent on the local hydrogeology and when combined they can result in areas where karst features evolve on a human time scale rather than a geological timescale karst collapse and subsidence are common in such areas making them problematical for the local population the evaporite karst environment is very sensitive to changes in the local hydrology and hydrogeology so that human factors such as groundwater extraction drainage and irrigation can act as triggering events for karst collapses some evaporite karst features such as caves and saline springs have been beneficially exploited but most of them including sinkholes subsidence and groundwater degradation pose a threat to the local environment and a hazard to development the papers in this special issue of environmental geology arose from a successful session on evaporite karst convened by us at the sixth international conference on geomorphology this was held in zaragoza spain in september 2005 and was organised by zaragoza university and the international association of geomorphologists iag http www geomorph org authors of the twenty eight presented abstracts were invited to submit full papers to this special issue nineteen papers were proposed and sixteen papers have been accepted and are published here

water inrush and environmental impact of shallow seam mining shallow seam mining is very common in china for enhancing coal recovery however this may cause a series of severe problems in environment and mining safety in some cases because the alluvium aquifers are directly above the shallow coal seams some typical water and sand inrush incidents resulting from shallow mining in china are analyzed based on in situ observation the mining induced strata failures are investigated the height of the fractured zone decreases as the size of the outcrop pillar or mining depth decreases the spatial distributions of the failure zones in the shallow mining have specific features compared to the deep mining these provide an advantageous condition for the shallow mining under alluvial aquifers optimal designs for outcrop pillar sizes are also given in different hydrogeological conditions for environment friendly and production safe mining at shallow depths according to in situ mining experiments in several coalfields technical measures for shallow mining are presented these primarily include the lift mining for thick seams and reduction of the thickness of extraction in the first lift short wall mining and detection of faults and other potential hazards prior to mining

water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams summary karst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes matrix and fractures for more than a century various approaches have used flood recession curves which integrate all hydrodynamic processes in a karst aquifer to infer physical properties of the movement and storage of groundwater these investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves we present analyses of simultaneous discharge and water level time series of two distinctly different karst systems one with low porosity and permeability matrix rocks in southern france and one with high porosity and permeability matrix rocks in north central florida usa we apply simple mathematical models of flood recession using time series representations of recharge storage and discharge processes in the karst aquifer we show that karst spring hydrographs can be interpreted according to pressure transfer between two distinct components of the aquifer conduit and matrix porosity which induce two distinct responses at the spring water exchange between conduits and matrix porosity successively control the flow regime at the spring this exchange is governed by hydraulic head differences between conduits and matrix head gradients within conduits and the contrast of permeability between conduits and matrix these observations have consequences for physical interpretations of recession curves and modeling of karst spring flows particularly for the relative magnitudes of base flow and quick flow from karst springs finally these results suggest that similar analyses of recession curves can be applied to karst aquifers with distinct physical characteristics utilizing well and spring hydrograph data but information must be known about the hydrodynamics and physical properties of the aquifer before the results can be correctly interpreted

karst collapse in cities and mining areas china karst collapse is a dynamic geological phenomenon in which the rock mass or deposits overlying the karstified zone subsides down along the karst cavity resulting in a collapse pit or sinkhole after discussing the typical examples of collapse emerging in the karst cities and mines in provinces and regions of south china such as guangdong guangxi hunan hubei zhejiang yunnan guizhou and jiangxi it is considered that human activities of economy and production have become a major effect in causing karst collapse

sinkhole occurrence monitoring over shallow abandoned coal mines with satellite based persistent scatterer interferometry abstract unexpectedly occurring sinkholes caused by shallow submerged voids are one of the key problems of intensively built up post mining areas five percent of poland s territory is still under the influence of post mining deformation impending sinkholes which tend to develop randomly over very large areas cannot be detected by using traditional geophysical methods moreover geodetic measurement methods like global positioning system gps analyses tachymetry laser scanning or photogrammetry may be useful only for the registration of the dimensions and locations of sinkholes that have already occurred here we investigate an area in upper silesia poland where 345 sinkholes were recorded over a period of more than 20 years 1992 2013 most of the events occurred in intensively built up areas and thus these sinkholes posed a direct threat to the population in the test area 11 sinkholes were detected with a maximum depth of 16 m and maximum dimension of 25 m the root cause of sinkhole formation was the collapse of post mining shallow voids we used satellite radar technology to detect and monitor ground movements potentially associated with the impending sinkholes the findings showed that the application of persistent scatterer interferometry can support the identification of zones where sinkholes will occur given adequate spatio temporal sampling a stack of envisat synthetic aperture radar sar images acquired between march 2003 and august 2010 was used in the analysis and the results confirmed that precursory ground movements were detectable at an early stage of sinkhole development the land subsidence rate observed prior to sinkhole collapse was not constant in time accelerated ground movements within 100 m of an observed sinkhole were detected we conclude that satellite measurements may provide significant support in the early identification of areas prone to sinkhole occurrence

review on sinkhole monitoring and performance of remediation measures by high precision leveling and terrestrial laser scanner in the salt karst of the ebro valley spain abstract the need to apply sinkhole remediation and monitoring programs is increasing concurrently with the rising engineering impacts of sinkholes in many regions however there is a significant gap in the scientific literature regarding the assessment of the performance of remedial works through subsidence monitoring monitoring techniques have experienced significant advances in the last few years thanks to the advent of new technologies this work presents a review of sinkhole monitoring methods and discusses some practical considerations about their capabilities and limitations it also documents a monitoring program high precision leveling and terrestrial laser scanner and the concurrent remedial works cement based and polyurethane grouting carried out in a highly active sinkhole that affects a flood control dike and the adjacent village of alcala ne spain the subsidence activity in the sinkhole is characterised by progressive sagging and the development of catastrophic nested collapses monitoring data reveal subsidence expansion and acceleration in the sector of the dike treated by polyurethane grouting above the main cavities in contrast subsequent cement based grouting of the large cavities significantly reduced subsidence rates displacement data also indicate substantial subsidence enhancement following flood recession and the associated water table drop buoyancy loss this case study illustrates that high precision leveling and terrestrial laser scanning are adequate complementary methods for monitoring specific sinkholes characterised by very high accuracy and detailed spatial resolution respectively

delineating vulnerability of karst aquifers using hydrochemical tracers in southwestern china karst groundwater is particularly vulnerable to contamination long term hydrochemistry auto monitoring combined with laboratory analyses has shown that the chemograph demonstrates changes in the system in order to determine the primary groundwater vulnerability a relationship between hydrochemical changes and the origin of vulnerability in six karst spring catchments in southwestern china is discussed the reason and physical meaning of the hydrochemical changes in the spring are explained based on tracer tests and physical chemical process in the s31 spring the results prove that the hydrochemical changes show the origin of vulnerability and also can be its expression generally autogenic recharge in bare karst is concentrated in epikarst zone forming bypass flow and shaft flow which causes dilution of ca2 the chemograph reflects the percentage of concentrated and diffuse recharge the higher the ratio of concentrated recharge the higher the grade of groundwater vulnerability due to ca2 hco3 sec ph and temperature in water can change for kinds of reasons during their transport more karst systems with variable natural and human factors are discussed protective layer allogenic water recharge and transform of surface stream and subterranean river can change the origin shape of hydrochemical curve under this circumstance more indicators need to be monitored especially contaminant related ions such as nitrate in order to clearly understand the contribution of concentrated and diffuse recharge to water chemistry after comparing the traditional groundwater vulnerability assessment and the methods based on hydrochemical change rainfall protective layer epikarst transient storage and karst network should be more concerned when the work is done auto monitoring of karst is more and more popular in southwestern china therefore it is suggested that the hydrochemical methods should be used as a primary expression of vulnerability giving a direct reference for karst water management

sinkhole susceptibility mapping using the analytical hierarchy process ahp and magnitude frequency relationships a case study in hamadan province iran abstract since 1989 an increasing number of sinkhole occurrences have been reported in the kabudar ahang and razan qahavand subcatchments krq of hamadan province western iran the sinkhole related subsidence phenomenon poses a significant threat for people and human structures including sensitive facilities like the hamadan power plant groundwater over exploitation from the thick alluvial cover and the underlying cavernous limestone has been identified as the main factor involved in sinkhole development a sinkhole susceptibility model was produced in a gis environment applying the analytical hierarchy process ahp approach and considering a selection of eight factors each categorized into five classes distance to faults df water level decline wld groundwater exploitation ge penetration of deep wells into karst bedrock pka distance to deep wells ddw groundwater alkalinity ga bedrock lithology bl and alluvium thickness at relative weights were preliminarily assigned to each factor and to their different classes through systematic pairwise comparisons based on expert judgment the resulting sinkhole susceptibility index ssi values were then classified into four susceptibility classes low moderate high and very high susceptibility subsequently the model was refined through a trial and error process involving changes in the relative weights and iterative evaluation of the prediction capability independent evaluation of the final model indicates that 55 and 45 of the subsidence events fall within the very high and high susceptibility zones respectively the results of this study show that ahp can be a useful approach for susceptibility assessment if data on the main controlling factors have sufficient accuracy and spatial coverage the limitations of the model are partly related to the difficulty of gathering data on some important geological factors due to their hidden nature the magnitude and frequency relationship constructed with the 41 sinkholes with chronological and morphometric data indicates maximum recurrence intervals of 1 17 2 14 and 4 18 years for sinkholes with major axial lengths equal to or higher than 10 m 20 m and 30 m respectively

hydraulic fracturing and the crooked lake sequences insights gleaned from regional seismic networks within central alberta canada a new sequence of earthquakes has been recognized as of 1 december 2013 in a region of previous seismic quiescence near crooked lake 30 km west of the town of fox creek we utilize a cross correlation detection algorithm to detect more than 160 events to the end of 2014 which is temporally distinguished into five subsequences this observation is corroborated by the uniqueness of waveforms clustered by subsequence the crooked lake sequences have come under scrutiny due to its strong temporal correlation 99 99 to the timing of hydraulic fracturing operations in the duvernay formation we assert that individual subsequences are related to fracturing stimulation and despite adverse initial station geometry double difference techniques allow us to spatially relate each cluster back to a unique horizontal well overall we find that seismicity in the crooked lake sequences is consistent with first order observations of hydraulic fracturing induced seismicity

new advances in karst collapse research in china until 2000 more than 1 446 karst collapse events and 45 037 sinkhole pits have been documented in china in this paper focusing on new achievements of karst collapse research in china a large scale model experiment a method of risk assessment and data management of karst collapse based on geographic information system technology are introduced for the region

temporal relationship between injection rates and induced seismicity normalized cross correlation of effective functions was originally developed to differentiate induced and natural seismicity we apply this methodology to data sets acquired during hydraulic stimulation of shale gas to study temporal relationship between seismicity and the injection delays of seismicity induced by hydraulic fracturing are compared with delays of seismicity related to changes of the water level in a dam a new observation is made we show that seismicity induced by hydraulic fracturing and measured by the normalized cross correlation can have very positive to even short negative delay after the injection we explain this observation by rapid decline of induced seismicity after decrease of injection on the contrary we show that the seismicity triggered by water impounding in a dam is characterized by longer delays due to much greater distance between lake and the induced seismicity we show how it is possible to measure the delay by the cross correlation methodology despite periodicity of the signals

sinkholes pit craters and small calderas analog models of depletion induced collapse analyzed by computed x ray microtomography volumetric depletion of a subsurface body commonly results in the collapse of overburden and the formation of enclosed topographic depressions such depressions are termed sinkholes in karst terrains and pit craters or collapse calderas in volcanic terrains this paper reports the first use of computed x ray microtomography mu ct to image analog models of small scale similar to 2 km diameter high cohesion overburden collapse induced by depletion of a near cylindrical stock like body time lapse radiography enabled quantitative monitoring of the evolution of collapse structure velocity and volume moreover mu ct scanning enabled nondestructive visualization of the final collapse volumes and fault geometries in three dimensions the results illustrate two end member scenarios 1 near continuous collapse into the depleting body and 2 near instantaneous collapse into a subsurface cavity formed above the depleting body even within near continuously collapsing columns subsidence rates vary spatially and temporally with incremental accelerations the highest subsidence rates occur before and immediately after a surface depression is formed in both scenarios the collapsing overburden column undergoes a marked volumetric expansion such that the volume of subsurface depletion substantially exceeds that of the resulting topographic depression in the karst context this effect is termed bulking and our results indicate that it may occur not only at the onset of collapse but also during progressive subsidence in the volcanic context bulking of magma reservoir overburden rock may at least partially explain why the volume of magma erupted commonly exceeds that of the surface depression

water geochemical characteristic variations in and around a karst dominated natural reserve area southwestern china this paper reports original data on the physical and chemical parameters of precipitation river water and groundwater in and around the longhushan nature reserve area located in southwestern china karst region and provides a preliminary characterization of the hydrogeochemical process governing the natural water evolution in this area the rainfall and river water mainly pertain to the hco3 ca2 type and groundwater mainly pertain to the hco3 ca2 mg2 type the hco3 was the predominant anion and ca2 was the predominant cation in all waters respectively the gibbs boomerang envelop model the 1 1 relationship of na plus k versus cl as well as the 1 1 relationship of ca2 plus mg2 versus hco3 all suggested geochemical weathering is the main controlling factor for the geochemical compositions of this natural water in surface water the mg2 ca2 ratios ranged from 0 32 to 0 42 and the na ca2 varied between 0 04 and 0 05 in the groundwater the mg2 ca2 ratios varied from 0 37 to 0 62 and were below the ideal ratio of 0 8 these ratios showed the presence of a dolomite source analysis of trace elements showed that as b pb se sr v and zn elements were abundant in the natural water during summer in this region

evaluation of trenching ground penetrating radar gpr and electrical resistivity tomography ert for sinkhole characterization this paper explores the suitability and advantages of combining the trenching technique with geophysical surveys ground penetrating radar gpr and electrical resistivity tomography ert for sinkhole characterization in a mantled karst area the approach is applied to two active sinkholes concealed by anthropogenic deposits and formed by contrasting subsidence mechanisms collapse and sagging the ert section acquired across the collapse sinkhole images the clayey fill of the depression as an obvious low resistivity area showing the approximate location of the sinkhole edges spatially dense gpr surveys provide information on the position of the boundaries of the concealed subsidence structures and their three dimensional 3d internal geometry revealing the dominant subsidence mechanism we illustrate the impact of several factors on the quality of the gpr data such as sinkhole size nominal frequency of the antennas antenna shielding and the presence of backfilled excavations and above surface objects trenches provided detailed information on the subsurface structure of the sinkhole subsidence magnitude partitioning of the strain and the position of the sinkhole edges especially when they are deep enough and excavated across the central sector and perpendicular to the boundaries the stratigraphic and structural relationships observed in the trench were then used to infer the spatial evolution of the sinkholes e g enlargement their kinematic behavior episodic versus progressive and to differentiate discrete subsidence events and their associated magnitude numerical dates were used to estimate average subsidence rates and the recurrence of subsidence events such integrated data sets may be used as an objective basis to forecast the future behavior of potentially damaging sinkholes and to assess the associated hazard and risk copyright 2013 john wiley sons ltd

modeling of water rock interactions in an aquitard of sandy clay in the coastal area near beihai china unconsolidated sand gravel and clay deposits near beihai and in the leizhou peninsula in southern china form an unconfined aquifer aquitard and a confined aquifer water and soil samples were collected from the two aquifers in the coastal beihai area for the determination of chemical compositions minerals and soluble ions hydrogeochemical modeling of three flow paths through the aquitard are carried out using phreeqc to determine water rock interactions along the flow paths the results indicate that the dissolution of anorthite fluorite halite rhodochrosite and co2 and precipitation of potash feldspar and kaolinite may be occurring when groundwater leaks through the aquitard from the unconfined aquifer to the confined aquifer cation exchanges between na and ca can also happen along the flow paths

deep injection and closely monitored induced seismicity at paradox valley colorado the u s bureau of reclamation s paradox valley unit pvu extracts aquifer brine from nine shallow wells along the dolores river paradox valley in southwestern colorado and after treating high pressure injects the brine 4 3 4 8 km below the surface pvu injects at rates between 800 and 1300 l min since 1991 pvu has emplaced over 4 106 m3 of fluid and induced more than 4000 surface recorded seismic events the events are recorded on the local 15 station paradox valley seismic network the induced seismicity at paradox separates into two distinct source zones a principle zone 95 of the events asymmetrically surrounding the injection well to a maximum radial distance of 3 km and a secondary ellipsoidal zone 2 5 km long and centered 8 km northwest of the injection well the expansion of these zones has stabilized since mid 1999 about three years after the onset of continuous injection within the principal zone hypocenters align in distinct linear patterns showing at depth stratigraphy and the local wray mesa fracture and fault system the primary faults of the wray mesa system are aseismic striking subparallel to the inferred maximum principal stress direction with one or more faults probably acting as fluid conduits to the secondary seismic zone individual seismic events in both zones do not discernibly correlate with short term injection parameters however a 0 5 km2 region immediately northwest of the injection well responds to long term large scale changes in injection rate and the surpassing of a threshold injection pressure focal mechanisms of the induced events are consistent with simple double couple strike slip moments and subhorizontal extension to the northeast in addition the fault planes are consistent with principal stress directions determined from borehole breakouts more than 99 9 of the pvu seismicity is below human detection m 2 5 however approximately 15 events have been felt locally with the largest being a magnitude m 4 3 because of the m 4 3 and two earlier felt m 3 5 events and injection economics pvu changed injection strategies three times since 1996 these changes reduced seismicity from 1100 events year to as low as 60 events year

identification prediction and mitigation of sinkhole hazards in evaporite karst areas sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas this is because evaporites have a higher solubility and commonly a lower mechanical strength subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world but the causes are only well understood in a few areas to deal with these hazards a phased approach is needed for sinkhole identification investigation prediction and mitigation identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources detailed sinkhole maps can be constructed from sequential historical maps recent topographical maps and digital elevation models dems complemented with building damage surveying remote sensing and high resolution geodetic surveys on a more detailed level information from exposed paleosubsidence features paleokarst speleological explorations geophysical investigations trenching dating techniques and boreholes may help in investigating dissolution and subsidence features information on the hydrogeological pathways including caves springs and swallow holes are particularly important especially when corroborated by tracer tests these diverse data sources make a valuable database the karst inventory from this dataset sinkhole susceptibility zonations relative probability may be produced based on the spatial distribution of the features and good knowledge of the local geology sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation alignment and nearest neighbor analysis more objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes number of sinkholes km2 year such spatial and temporal predictions frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future are non corroborated hypotheses validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole prone areas corrective measures could be applied to reduce the dissolution activity and subsidence processes a more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence proof designs

the role of hydrogeology in solution subsidence development and its environmental impacts a case study for sazlica nigde turkey solution subsidence and other types of collapse failures developed in the vicinity of sazlica have been a major source of environmental problems such as groundwater pollution soil erosion and foundation failures extensive pumping of water from the lake dipsiz during irrigation seasons creates landslide developments at the shores of the lake five stages of landslide development were observed in the unconsolidated soils around lake dipsiz bowl shaped solution subsidence features with depths from 1 to 3 m and diameters between 1 and 60 m were formed due to excess pumping and recharge and discharge features of unconfined aquifer the pumping activities must be controlled to prevent further environmental problems lake dipsiz and other subsidence developments are the groundwater exposure areas highly vulnerable to contamination the proposed remedies for overcoming the environmental problems are the establishment of conservation areas around such natural features ceasing the removal of top soil controlling the urbanization and keeping the livestock farming away from the areas susceptible to pollution

identification remediation and analysis of karst sinkholes in the longest railroad tunnel in south korea abstract tunneling in karst terrains presents numerous challenges to the engineer including the unpredictable occurrence of cavities and well developed hydraulic conduits that could lead to sinkhole development during construction of the longest railroad tunnel in south korea excessive water inrushes and support collapses accompanying the formation of a couple of sinkholes and subsidence on the ground surface such cases of sinkhole formation during tunneling in south korea have been rarely reported various characterization methods were used at the tunneling site to identify the causes of the sinkholes and the subsidence on the ground surface especially noteworthy in this regard is that the massive limestone in this area contains a high degree of lime purity as high concentrations of lime are very corrosive a limestone micro scale cavity readily developed along the fault planes and joints due to weathering and chemical corrosion the data obtained from various types of geological and geophysical exploration methods identified the formation of micro scale cavity networks that served as conduits carrying reservoir water from the surface to the underground tunnel additional micro scale vertical cavity networks were detected for the unexcavated tunnel route through geophysical and horizontal probe core drilling methods ground reinforcement was applied to sinkhole and subsidence at the ground surface and the cavity inside the tunnel for remediation after the installation of underground waterproof grouting around the tunnel and of grouting walls around the sinkholes the groundwater level recovered and the ground surface settlement ceased seepage analyses were performed to provide an optimal drainage design for long term stability based on this case study and the lessons learned we suggest a risk reduction system for safe tunneling in karst terrains

sinkhole distribution in a rapidly developing urban environment hillsborough county tampa bay area florida sinkhole formation in florida is a common event the florida karst plain is significantly altered by human development and sinkholes cause considerable property damage throughout much of the state we present in this paper a morphometric analysis of karst depressions in the tampa bay area and the relation with the known distribution of sinkholes we selected the tampa bay area because it is particularly susceptible to the evolution of karst depressions in relation with development of the built up environment karst depressions were mapped from the 1 24 000 usgs topographic maps and a morphometric analysis was performed by using parameters such as shape circularity index perimeter area length width and orientation maps showing the distribution of depression density and the sectors with greatest areas of karst depression were produced using a gis these results were compared with data compiled from the database of sinkhole occurrences in florida maintained by the florida geological survey our analysis demonstrates that the distribution of new sinkhole occurrences differs from the distribution of existing sinkholes indicating that there are processes acting today that are influencing karst landscape formation that are different from those acting in the past

the formation of sinkholes in karst mining areas in china and some methods of prevention mining of coal lead and zinc gold and iron ore deposits in karst areas has been closely associated with sinkholes in china surface collapse causes an increase in mine water drainage and the possibility of major water inflow from karst aquifers which threatens the environment in mining areas and endangers mine safety the origin of such sinkholes is analyzed quantitatively in this paper and a combination of factors including soil weight buoyancy suffosion process and vacuum suction can contribute to surface subsidence the key measures to prevent sinkholes in mining areas are to control the amount of mine drainage reduce water level fluctuation seal off karst conduits and subsurface cavities in the overlying soil prevent water inflow and to increase gas pressure in the karst conduits

a genetic classification of sinkholes illustrated from evaporite paleokarst exposures in spain this contribution analyses the processes involved in the generation of sinkholes from the study of paleokarst features exposed in four spanish tertiary basins bedrock strata are subhorizontal evaporites and in three of the basins they include halite and glauberite in the subsurface our studies suggest that formation of dolines in these areas results from a wider range of subsidence processes than those included in the most recently published sinkhole classifications a new genetic classification of sinkholes applicable to both carbonate and evaporite karst areas is thus proposed with the exception of solution dolines it defines the main sinkhole types by use of two terms that refer to the material affected by downward gravitational movements cover bedrock or caprock and the main type of process involved collapse suffosion or sagging sinkholes that result from the combination of several subsidence processes and affect more than one type of material are described by combinations of the different terms with the dominant material or process followed by the secondary one e g bedrock sagging and collapse sinkhole the mechanism of collapse includes any brittle gravitational deformation of cover and bedrock material such as upward stoping of cavities by roof failure development of well defined failure planes and rock brecciation suffosion is the downward migration of cover deposits through dissolutional conduits accompanied with ductile settling sagging is the ductile flexure of sediments caused by differential corrosional lowering of the rockhead or interstratal karstification of the soluble bedrock the paleokarsts we analysed suggest that the sagging mechanism not included in previous genetic classifications plays an important role in the generation of sinkholes in evaporites moreover collapse processes are more significant in extent and rate in areas underlain by evaporites than in carbonate karst primarily due to the greater solubility of the evaporites and the lower mechanical strength and ductile rheology of gypsum and salt rocks

human induced seismicity and large scale hydrocarbon production in the usa and canada we compare current and historic seismicity rates in six states in the usa and three provinces in canada to past and present hydrocarbon production all states provinces are major hydrocarbon producers our analyses span three to five decades depending on data availability total hydrocarbon production has significantly increased in the past few years in these regions increased production in most areas is due to large scale hydraulic fracturing and thus underground fluid injection furthermore increased hydrocarbon production generally leads to increased water production which must be treated recycled or disposed of underground increased fluid injection enhances the likelihood of fault reactivation which may affect current seismicity rates we find that increased seismicity in oklahoma likely due to salt water disposal has an 85 correlation with oil production yet the other areas do not display state province wide correlations between increased seismicity and production despite 8 16 fold increases in production in some states however in various cases seismicity has locally increased multiple factors play an important role in determining the likelihood of anthropogenic activities influencing earthquake rates including i the near surface tectonic background rate ii the existence of critically stressed and favorably oriented faults which must be hydraulically connected to injection wells iii the orientation and magnitudes of the in situ stress field combined with iv the injection volumes and implemented depletion strategies a comparison with the seismic hazard maps for the usa and canada shows that induced seismicity is less likely in areas with a lower hazard the opposite however is not necessarily true

assessment of sediment and erosion rates by using the caesium 137 technique in a chinese polygonal karst depression karst depressions comprise geomorphologically important sources and sinks for sediments and associated pollutants yet the sedimentology of many depressions is not well understood in the world in this paper the 137cs technique was employed to estimate recent sedimentation rates in a chinese polygonal karst depression the results indicate that the sediment deposition rates ranged from 0 91 to 1 97 mm year 1 from 1963 to 2007 and the average sediment deposition rate and specific deposit yield were estimated to be 1 47 mm year 1 and 20 t km 2 year 1 respectively these results are consistent with the local monitoring data of runoff fields which confirms the validity of the overall approach this shows that the soil loss rate is very low in some karst areas of southwest china above all the approach appears to offer valuable potential to study surface erosion by estimating sediment deposition rates of karst depressions rather than the assessment of complicated soil erosion in stony soils of carbonate rock slopes in addition the space distribution of surface soil and 137cs inventories are affected remarkably by the inhomogeneous dissolution of limestone under the soil it may be an important phenomenon which exists widely in karst areas and it is significantly different from other places

environmental and engineering problems of karst geology in china karst terrane is generally regarded as a fragile and vulnerable environment its underground drainage system can aggrevate both drought and flood problems the lack of filtration in an underground conduit makes waste disposal more difficult and the lack of soil cover in bare karstland can enhance deforestation moreover karst terranes are quite often haunted by a series of engineering problems such as water gushing into mines or transportation tunnels leakage from reservoirs and failure of building foundations in china there are more than 200 cases of karst collapse which include many thousands of individual collapse points some of these are paleo and natural collapses but most of them are modern collapses induced by human activities and they have caused serious damage many factors such as geologic structure overburden thickness and character lithologic features of karstified rock and intensity of karstification are related to development and distribution of modern collapses however china s karst is mainly developed in pre triassic old phase hard compact carbonate rock consequently most modern collapses have occurred only in the overlying soil so it is understandable that the fluctuation of the water table in the underlying karstified strata plays an important role in the process of collapse nevertheless there are different explanations as to how the groundwater activities can induce collapse

evaluation of susceptibility for terrain collapse and subsidence in karst areas municipality of iraquara chapada diamantina ba brazil the morphological evolution of the karstic systems is associated with a set of physical and chemical processes triggered by the dissolution of the rocks related to percolation of groundwater and surface water which consequently open underground voids and carve out peculiar forms of relief due to environmental and geotechnical aspects this system is naturally more fragile and vulnerable than other natural systems and therefore has increasingly received the attention of the scientific community over the past decades the objective of the study was to delimit zones with varying degrees of susceptibility for collapses and subsidence of sinkholes in the municipality of iraquara chapada diamantina ba brazil and to understand their geological and morphological determinant factors geological data karst phenomenon map and visual analysis in the field were used to categorize zones with different types of susceptibilities to the nucleation of new sinkholes based on a hazard index this index was defined from the sum of geological hazard factors lineament density and sinkhole density the areas that presented the highest susceptibility for terrain collapse and subsidence corresponded to regions where carbonate rocks outcrop with high density of photolineaments and 2 62 sinkholes km2 processes associated with terrain collapse and subsidence in karst areas consisted of a combination of various factors hindering precise predictions however zones of different types of susceptibilities to terrain collapse and subsidence can be delimited when the relationships between these processes and their factors are understood the hazard index proposed does not provide quantitative values for the probability of hazard susceptibility but rather indicates areas that are more susceptible to terrain subsidence and collapse

basic processes and factors determining the evolution of collapse sinkholes a sensitivity study abstract collapse sinkholes are closed depressions appearing at the surface as a consequence of a complex interplay between dissolution erosion and mechanical stability in karst aquifers sinkholes are difficult to study and their locations are almost impossible to predict because of the multiple parameters involved and complex mechanisms controlling their evolution and collapse with this work we present a systematic theoretical research focused on the processes responsible for the development of collapse sinkholes splitting the evolution time in different stages we propose a conceptual model allowing decoupling of the main processes and a sensitivity study on the controlling parameters the conceptual framework is implemented with the help of a high resolution 2d karst evolution model and a simplified 3d dem mechanical model our results demonstrate that the development of a collapse sinkhole is controlled by dissolution throughout most of its evolution while the mechanical collapses occur during short time intervals the karstification is extremely sensitive to variations in the hydraulic conductivity or the amount of water flowing through the aquifer finally we discuss the hydro geological conditions which allow or not for systematic sensitivity studies

evolution of major environmental geological problems in karst areas of southwestern china karst terrains are generally regarded as a fragile and vulnerable environment china s karst is mainly developed in pre triassic old phase hard compact carbonate rock the lack of soil cover in bare karst land can enhance desertification its underground drainage system can aggravate both drought and flooding problems the interconnected surface and subsurface conditions allow for easy contamination by pollutants moreover karst terrains quite often suffer from a series of engineering problems such as water infiltrating into mines or transportation tunnels leakage from reservoirs and failure of building foundations as resources and energy exploitation intensified in recent years karst areas in southwest china faced some severe geo environmental problems in order to find out how the problems action and evolution in recent years field and laboratory investigations were conducted in guangxi autonomous region guizhou yunnan guangdong hunan hubei provinces and chongqing municipality about 100 experts from the provincial geological survey and graduate students took part in this project several symposiums were held during those 3 years besides the in situ survey data were collected from hydrogeological survey results since 2000 when the new round of land resources investigation began after analyzing these data rock desertification drought and flooding and contamination and engineering geological environmental problems were considered the most prevalent problems in karst areas in southwestern china the status of each problem is elaborated upon in this paper and should be considered for future sustainable development

drainage and flooding in karst terranes flooding in karst terranes is a commonly occurring geo hazard it causes damage to property businesses and roadways it can lead to the formation of cover collapse sinkholes and groundwater contamination generally three types of flooding or their combinations are related to karst recharge related sinkhole flooding flow related flooding and discharge related flooding understanding of the type of flooding is essential for solving the flooding problem areas prone to karst flooding should be recognized and restrictions and laws on land use should be implemented runoff and erosion control plans should address the unique characteristics of karst features digging out clogged sinkholes creating retention basins or installing class v injection wells are possible solutions to improve drainage of storm water solutions to flooding problems in karst areas should also be coordinated with the water quality control to prevent groundwater contamination

a multidisciplinary approach in sinkhole analysis the quinis village case study ne italy abstract during the last recent years in quinis a small village sited in the alta val tagliamento valley friuli venezia giulia region ne italy the inhabitants faced with instability phenomena related to the presence of soluble rocks in the subsurface the evaporite bedrock is mainly mantled in fact by high thickness deposit this paper explains the methodological approach that we used to identify the instabilities in a very complex geo structural environment where the urbanization limits the applicability of several investigation techniques different methods were used to define the bedrock morphology to characterize the mantling deposits and to identify the processes behind what emerged from the study is a mandatory multidisciplinary approach to characterize the subsoil because each technique is not able individually to take to a unique result the data collected allowed to draft a geo hydrogeological conceptual model of the quinis village the lessons learned even if with some site specific dependency demonstrate the importance of broad spectrum investigations which are essential to understand the subsurface characteristics avoiding relevant socio economic impact and supporting an adequate future territorial planning

water resource management in karstic catchments the case of the asso torrent basin southern italy in karstic endorheic basins the hydraulic works for runoff regulation marshland reclaiming and defense from inundations usually consist of channels tributary to sinkholes vertically connected to aquifers through karstic conduits and fractures the drainage capacity of such basins reduces as conduits and fractures are progressively clogged by sediments thus floodings may occur during heavy rains the sinks may also be utilized to inject treated wastewater underground this note concerns the management issues of the asso torrent basin italy where the recharge through water sinks preserves the deep aquifer from saltwater intrusion the basin represents a controversial case for which the sequence of infrastructures produced a critical system and nowadays it is difficult to find a compromise among mitigation of flood hazard safeguard of groundwater resources and preservation of human health the hydrogeological framework and the hydraulic works executed in the basin are described followed by considerations on the environmental effects of the decision making process finally statements concerning alternative measures for the management of the water resources are given management actions conforming to the integrated water resources management recommendations fail in the studied case because there is an intrinsic difficulty to transform the related concepts to practical and robust solutions

sedimentary record of pleistocene paleodoline evolution in the ebro basin ne spain abstract pleistocene fluvial deposits of the ebro river in ne spain are widely affected by faults fractures and tilting of beds based on the lithological geometrical and textural features of these deposits seven architectural elements have been differentiated gravel bars gb gravel filled channels ch sheets and channel fill sands sb are the most common elements and together with less frequent overbank fines ff characterize a gravel dominated braided fluvial system gravel lobes gl that draw progressive unconformities and are laterally related to u shaped or basin form mud deposits sediment gravity flow deposits sg and sands with slumps and convolute bedding sgs are not typical architectural elements of braided fluvial environments and they are interpreted in this work as related to syn sedimentary deformation our research proves that deformation is due to dissolution of the underlying tertiary evaporites with genesis of dolines the development of these karst structures involved both subsidence and sudden collapses that affected previous fluvial sediments small depressions dolines generated that were progressively filled by syn sedimentary deformed detrital deposits a model for the evolution of the doline fills is purposed that envisages several stages 1 gravitational processes caused remobilisation of previous fluvial gravels that were dragged to the created depression 2 flooding of the depression and development of a backswamp area that was progressively filled by fine sediments and gravel lobes as a consequence of the overflow of nearby channels 3 gravel lobes draw progressive unconformities revealing several subsidence episodes related to dissolution dragging and compaction 4 non deformed fluvial facies at the top of the series mark the end of the karstification influence osl optically stimulated luminiscence ages the first from the terraces of the ebro river demonstrate that karst has developed in this area at least since the late pleistocene and that the dolines have been filled in throughout several thousand years this large span time of doline evolution without anthropogenic influence should be considered for a better planning and management in hazardous areas

hydrogeological analysis and salvage of a deep coalmine after a groundwater inrush this paper presents a case history of the permanent salvage of the sanhejian coalmine in china after a sudden groundwater inrush which includes emergency responses hydrogeological analyses and design and performance of bulkheads the inrush accident occurred in october 2002 in the mined out area with a high water pressure of 7 6 mpa and a high water temperature of 51 c the emergency response quickly followed up to provide the time required to perform a detailed hydrogeological analysis to identify the source and pathway of groundwater the sanhejian coalmine is geologically located in the tengxian anticline hydrogeological setting the sunshidian fault the northern boundary of the mine was assumed impermeable in the original hydrogeological report after the accident and hydrogeological analysis this assessment was revised and the fault was considered to be permeable the sunshidian fault connects the strata in the mine and the excellent water productive middle ordovician majiagou formation in the core of the tengxian anticline it was concluded that the water inrush was from the underlying ordovician karst aquifer and the pathway was a hidden tectonic structure in the strata overlying the aquifer this assessment served as the guideline for salvaging the mine in this project after a detailed technical and economic analysis a concrete bulkhead design was selected from several alternatives including dewatering and surface grouting the performance of the bulkheads has been sufficient for the last 6 years since their construction this case history shows that the hydrogeological analysis plays an essential role in successfully salvaging the coalmine from the water inrush by identifying the source and pathway of groundwater

impact of karst water on coal mining in north china coalfields in north china encompass more than ten provinces they contain six to seven coal seams in the permo carboniferous strata the lower three seams account for 37 of the total reserves and are threatened with intrusion of karst water from the underlying ordovician limestone hundreds of water inrush incidences have occurred in which a large amount of water suddenly flows into tunnels or working faces under high potentiometric pressure over 50 mines have been flooded over the last 30 years large scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational this practice however has caused sinkholes dry springs water supply shortage and groundwater contamination in the surrounding areas one alternative water control measure is to make full use of the rock layer between the coal seam and the karst aquifer as a protective barrier to prevent or constrain water flow from the underlying aquifer into the mines grouting is effective when the hydrogeological conditions are favorable to this technique proper design of the grouting program and experience of the contractor are also important for a successful application

the 9 april 1993 earthquake in south central texas was it induced by fluid withdrawal an earthquake that occurred 9 april 1993 about 80 km south of san antonio is the largest earthquake known mblg 4 3 in south central texas in historic times the earthquake was felt over a 4000 km2 area and modified mercalli intensities were as high as vi at a gas production facility near fashing texas similar smaller events have occurred since 1973 at three sites near fashing pleasanton and falls city texas we propose a list of nine yes no questions to assess whether a sequence of earthquakes may have been induced by fluid withdrawal the criteria suggest that at least two sites fashing and pleasanton had earthquakes that were induced by fluid withdrawal related to ongoing oil and gas production an alternative possibility is that these events are the southwesternmost examples in a band of weak natural seismic activity between 135 and 240 km from the coast of the gulf of mexico and extending from this region east to the texas louisiana border in addition some injection occurs at all three sites although the volumes of fluid injected at fashing and pleasanton are low enough as to make injection an unlikely cause

sampling and preparation of c 200 mm diameter cylindrical rock samples for geomechanical experiments abstract experimental investigation of rock mechanical properties of real and artificial samples often requires much care and attention to detail during sample preparation this especially applies to high fidelity state of the art complex experimental apparatuses where sample tolerance is low due to the complexity of the measuring and stress control devices as well as the nature of the experiments to be conducted although sometimes mundane the sample preparation methodology is as equally important as the experimental apparatus itself and can require several new technological developments the methodology and technical developments required to prepare realistic heterogeneous fractured and natural reservoir analogue rock samples for coupled thermo hydro mechanical chemical process experimental investigation is described here we present the sample recovery and preparation procedures for large c 200 mm diameter cylindrical samples of 200 mm 5 mm length with variable composition and mechanical properties e g rock strength existing fractures fracture networks macro porosity or lithic fragments although the technology demonstrated is for a specific application the procedures developed equipment and methodology are applicable to multiple sizes of sample requirements

3 d transport and acoustic properties of fontainebleau sandstone during true triaxial deformation experiments abstract fontainebleau sandstone specimens have been tested in a true triaxial geophysical imaging cell under hydrostatic 1 2 3 traditional triaxial 1 2 3 and true triaxial 1 2 3 stress regimes the research objectives are to recognize the effect of various stress ratios 2 3 under varying magnitudes of 2 and 3 on 3 d stress strain responses 3 d transport 3 d ultrasonic wave velocities and acoustic emission properties comparison of the variation of 3 d directional permeability between the specimens shows that higher magnitude of 3 and 2 disrupts the 3 d interconnectivity of the pore spaces and intergranular cracks irrespective of the magnitude of applied stress ratio 2 3 the observed permeability anisotropy between the two specimens is a function of inherent oriented pores and cracks stress ratio 2 3 and the magnitude of applied 3 and 2 stresses temporal and spatial evolution of the ae hypocenter locations combined with the examination of micro ct and thin section images shows the timely development of polymodal fault systems during peak to post peak stresses and validates the development of the source mechanism inferred from the acoustic emission events

alluvial dolines in the central ebro basin spain a spatial and developmental hazard analysis abstract alluvial dolines are abundant in quaternary terraces and pediments overlying neogene gypsum in the zaragoza area central ebro basin spatial analysis and experimental simulation show that sulphate content in the groundwater grain size of the detrital cover topography of the tertiary quaternary boundary annual variation of the water table and thickness of the detrital cover are the main factors controlling their development taking into account these variables a theoretical spatial hazard model has been elaborated expressed as a mathematical equation and a hazard map both experiments and field data show a high correspondance between two basic mechanisms of evacuation and subsidence dragging slow subsidence and collapse of cavities and two basic types of morphology and internal structure of dolines basin doline funnel structure and well doline vault structures respectively a genetic classification of dolines and some evolutionary patterns based on these criteria are developed historical changes observed in doline distribution as well as field surveys of urban damage and microtopographic profiles allow us to evaluate the present day activity of dolines local subsidence rates measured in urban areas range from 2 5 to 10 cm year although doline generation and reactivation in the whole area tend to be compensated by filling by human activity

the impact of groundwater drawdown and vacuum pressure on sinkhole development physical laboratory models abstract a considerable proportion of the damaging sinkholes worldwide correspond to human induced subsidence events related to groundwater withdrawal and the associated water table decline e g aquifer overexploitation dewatering for mining buoyancy loss in pre existing cavity roofs is generally claimed to be the main underlying physical mechanism it has been also postulated that rapid water table drawdowns may create a vacuum effect in the subsurface and contribute to enhance sinkhole activity in karstic terrains with a low effective porosity cover our laboratory physical model explores the role played by vacuum pressure induced water table drops with different magnitudes and rates on sinkhole development simulating an invariable mantled karst comprising cavernous bedrock and a low permeability cover the multiple tests performed include real time monitoring of the water level drawdown magnitude duration rate the negative air pressures in the bedrock cavity and the cover and several features of the subsidence phenomena deformation style size magnitude rate the main findings derived from the test results include 1 vacuum pressure may trigger the development of cover collapse sinkholes in areas with low permeability covers 2 different water table decline patterns magnitude duration rate may result in different subsidence styles or rheological behaviours sagging versus collapse 3 ground fissuring frequently related to extension at the margin of sagging depressions may cancel or significantly diminish the vacuum effect 4 an overall direct relationship between the water table decline rate and the subsidence rate some possible strategies are proposed to ameliorate the adverse effect of the negative air pressure on sinkhole hazard which most probably has a local impact restricted by the concurrence of rapid water drawdowns and low permeability covers

temporal variation in the magnitude frequency distribution during the guy greenbrier earthquake sequence the recent increase in earthquake activity in the central u s has led to concerns about the hazard posed by induced earthquakes understanding earthquake phenomena and monitoring in all settings can be improved by the detection of small events however the catalog of induced earthquakes is incomplete for small events due to the sparse instrumentation this is particularly true in settings of low background seismicity like the central u s we apply single station template matching to detect small earthquakes during the guy greenbrier sequence in central arkansas and find over 100 times more earthquakes than are registered in the advanced national seismic system catalog between july 2010 and october 2011 a complete catalog over nearly 4 units of magnitude enables us to analyze the magnitude frequency distribution of induced earthquakes we find that earthquakes deviated from the gutenberg richter statistics during the operation of nearby injection wells but returned to gutenberg richter statistics after the wells were shut in

sinkhole investigation in an urban area by trenching in combination with gpr ert and high precision leveling mantled evaporite karst of zaragoza city ne spain abstract sinkhole risks are becoming particularly severe in urban areas that lack careful planning and where karst depressions are frequently filled and developed these built up areas are the most challenging for sinkhole investigation they are the ones that require the highest priority and the application of novel approaches aimed at reducing the epistemic uncertainties associated with hazard assessments this work illustrates the strengths of the rarely used trenching technique for the investigation of sinkholes in mantled karst areas the approach has been tested on a buried sinkhole in the evaporite karst of zaragoza city analysing and comparing data gathered by trenching ground penetrating radar gpr using shielded and unshielded antennas with different frequencies electrical resistivity tomography ert and high precision leveling the sinkhole is located beneath a street and has led to the demolition of buildings creating a risk situation that requires careful assessment and management trenching provided the largest amount of objective data required for hazard assessment 1 precise location of the sinkhole edges 2 internal structure cumulative displacement subsidence mechanisms and their contribution the trench exposed an asymmetric structure with a minimum vertical displacement of 6 2 m comprising a complex collapse with different generations of faults and two marginal zones affected by gentle inward tilting collapse faulting accommodates at least 70 of the subsidence 3 age of the sinkhole and average subsidence rate the sinkhole was initiated sometime before or within 337 435 cal yr ad indicating a long term subsidence rate of ca 3 7 4 2 mm yr 4 kinematic style characterised by episodic collapse events as supported by leveling data the retrodeformation analysis together with geochronological data indicates four collapse events with a recurrence of around 400 years and suggests enhanced activity since ca 1950 ad the performance of gpr was highly variable depending mainly on the type of antenna and the timing of data acquisition the best quality data were obtained with shielded antennas and during relatively drier conditions the rather poor performance of ert commonly an adequate method for resolving subsidence structures at depth is attributed to the complex structure of the collapse sinkhole with spatially dense and abrupt resistivity changes in resistivity this case study strongly substantiates the implementation of the relatively inexpensive and highly objective trenching technique in sinkhole investigations

slope form erosion and hydrology in some belizean karst depressions detailed slope surveys were made in seven karst depressions in central belize four major slope types were identified inclined bedrock slopes staircases broken cliffs and talus slopes depression bases are dominated by inclined bedrock and talus slopes midslopes largely by broken cliffs and near hill summits by staircases erosional weight loss tablets deployed in 1975 1981 and 1980 1985 show significant variations between the different slope types with a maximum near depression bases throughfall measurements in 1980 and 1985 show that midslope and near summit sites receive 10 20 per cent less water than do depression bases surface runoff monitored using coloured dyes is of limited distance and duration but still contributes to surface corrosion and morphology vadose seepage monitored by tracing water from the surface to a small shallow cave is rapid and subsurface corrosion exceeds that at the surface overall near surface form and process are consistent with hydrological models of depression development williams 1983 1985 and surface processes contribute significantly to overall depression form moreover surface activity complements that in the subcutaneous zone by directing recharge into the epikarstic aquifer

flash flood events recorded by air temperature changes in caves a case study in covadura cave se spain summary on 28th september 2012 more than 150 mm rain fell in just two hours in some points of southeastern spain triggering intense flash floods that resulted in the death of ten people and widespread material damage in the gypsum karst of sorbas rainfall intensity reached 33 mm h air temperature monitoring in different levels of covadura cave down to 85 m depth enabled the effect of this extreme episode on the cave microclimate to be evaluated in real time the cave air temperature increased by between 0 9 and 4 1 c as a result of water flow into the cavity and intense mixing of air masses in addition to the displacement of deeper air masses toward shallower levels produced by fast recharge of the surrounding karst aquifer the lag between peak rainfall intensity and the highest cave air temperature was 5 6 h indicating the response time of the karst to this rainfall event no trends with depth were observed suggesting that water not only flowed in through the main cave entrance but also through secondary accesses and fractures furthermore the size of the cave passages and the intensity of air turbulence generated by waterfalls in the cave played an important role in producing these temperature differences even though the rainfall event lasted 10 h cave air temperature did not return to pre flash flood values until more than 20 days later this indicates that while waterflow through the cave might stop a few hours after the rainfall event cave air temperature can be affected over a longer period this can be explained by slow groundwater level decreasing of the surrounding karst aquifer and latent heat liberation produced by moisture condensation on the cave walls our results show how continuous monitoring of air temperature in caves can be a useful tool for evaluating the short term effects of flash floods in subterranean karst systems