geohazard map of cover collapse sinkholes in the tournaisis area southern belgium abstract this paper reports the methodology developed to draw up a geohazard map of cover collapse sinkhole occurrences in the tournaisis area in this area carboniferous limestones are overlain by a mesocenozoic cover mainly consisting of marls sand and clay the thickness of this cover ranges from a few meters to more than 100 m the surficial morphology of the area does not show any karstic evidence except for the occurrence of these collapses from a paleogeographical point of view a developed quaternary karst is not conceivable in the area recent works suggested that the collapses are set off from reactivated paleokarsts the paleokarsts studied in the area proved to be the result of a particular weathering of the limestone the organization of these paleokarsts seems very low and mainly guided by the limestone fracturing as for most induced sinkholes the reactivation of these paleokarsts is linked to the lowering of piezometric heads in most of the area a thick cover and intensive land use mask potential surface hints of the buried paleokarsts and of the fracturing of the bedrock aerial photographs and remote sensing techniques have therefore shown little results in delineating collapse hazard zones up to now the study of the surficial morphology is also of little help in order to draw up the geohazard map in such a difficult context hydrogeological data and geological mapping information could only be used these informations are based on a limited number of boreholes and piezometers and are thus only valid on a regional scale records of former collapses were also available these records were of great interest since sinkhole distribution is obviously clustered in the area bedrock roof and cover formation floor altitudes were digitized and adapted to produce digital thematic maps piezometric heads were imported from a calibrated groundwater model of the aquifer these data and a digital elevation model of the area were integrated into a geographical information system gis to produce a coherent 3 d description of the area on a regional scale parameters such as the dewatering of the limestone and the thickness of the cover formation where sinkholes occurred were then estimated density of former collapses was also computed this showed that zones of high sinkhole occurrence coincide with zones of heavy lowering of piezometric heads combining the density of former collapses with the dewatering of the limestone enabled us to delineate zones of low moderate and high collapse hazard

the influence of loess cave development upon landslides and geomorphologic evolution a case study from the northwest loess plateau china abstract loess caves landslides collapses bank erosion and soil erosion which are independently and interactively shaping the modern loess landscape are widely distributed across the chinese loess plateau the study area is located in a small watershed in huining county gansu province which is one of the areas with the strongest development of loess caves across the loess plateau this area is an ideal site for studying geological hazards and geomorphic evolution on the loess plateau seventeen landslides and 176 loess caves with a density of 887 units km2 were investigated with a uav unmanned aerial vehicle and mapped by gis geographic information system using high resolution uav images and topographic data we carried out an interpretation of loess caves bank erosion and landslides studied the spatial distribution and developmental patterns of loess caves landform morphology and the relationship between loess caves and landslides based on gis spatial analysis mathematical statistics and field surveys and analyzed the influence of loess microtopography on slope landforms finally six typical evolutionary models of soil erosion loess cave development landslide occurrence barrier dam formation are preliminarily proposed the primary slope stage early cave stage accelerated cave stage cave connecting stage landslide creeping stage and landslide dam forming stage this study is a useful exploration and an attempt to reveal the influence of loess cave development on slope stability and disaster chain effects

experimental study on the critical triggering condition of soil failure in subsidence sinkholes subsidence sinkholes in karst terrain are a common geological hazard which can lead to natural disasters in the natural and built environment groundwater ingress is the main factor leading to subsidence previous research has focused on the qualitative analysis of the influence of groundwater although limited research into critical triggering conditions of groundwater has been undertaken quantitatively water seepage into soil is the starting condition in the development of subsidence sinkholes this paper focuses on testing the anti permeability strength as the critical triggering condition in the formation of subsidence sinkholes and develops a design and methodology to test its value quantitatively the methodology is applied in an industrial park of guilin china to assess the probability of forming subsidence sinkholes results indicate that there is a low susceptibility to the formation of subsidence sinkholes under current conditions in the ground truth investigation

hazard mapping of karst along the coast of the algarve portugal abstract the engineering geology of the west algarve coastline between cape st vincent in the west and faro in the east varies considerably from the high limestone cliffs between salema and burgau to the lower but more problematic karstic cliffs around lagos and east of portimao geotechnical problems vary from toppling failure and rockfalls in the higher more heavily jointed limestone and sandstone cliffs between salema and burgau to sinkhole collapse subsidence and gullying within the miocene calcarenites and pleistocene sands east of portimao this latter area is the subject of this paper field mapping was completed on scales of 1 2000 and 1 5000 to encompass geomorphology geology and vegetation cover both sinkhole and sea cliff formation controlling factors are discussed and subsequently nine factors affecting potential hazard location are identified the relative importance of these ten factors is determined and then each cell 100 m2 in size is assessed for its individual score relative to the presence of or degree of influence of each of the hazard forming processes the resulting composite hazard map is aimed at planners and developers as a multipurpose map for general use

unusual cases of mining subsidence from great britain germany and colombia subsidence involves sinking of the ground surface the movement generally is localised and may or may not involve some amount of horizontal movement it may be rapid or take place gradually over a period of time subsidence may be brought about by natural causes as for example when the roof of a cavern in limestone is weakened to the extent that it is no longer self supporting and so collapses other more exotic examples are associated with volcanism and earthquakes perhaps however subsidence is more frequently associated with movements caused by mining activities that is the removal of mineral deposits be they in solid liquid or gaseous form from within the ground mining is one of the earliest activities of man and has taken place in every continent subsidence also can result from subsurface excavations such as tunnels caverns cellars and sewers one of the added problems of some forms of subsidence is that it is impossible to predict this coupled with the fact that the presence of potentially collapsible voids may be unknown unrecorded or simply forgotten about further complicates the problem the objectives of this paper are to document and draw attention to a number of unusual examples of subsidence these have been generated due to the mining of chalk in southern england the collapse of slate mines and caverns in germany the underground extraction of evaporites in northern ireland fault reactivation in wales and northern england and the extensive extraction of pumice on the flanks of galeras volcano in colombia

solving the production diffusion equation for finite diffusion domains of various shapes part 2 application to cases with alpha ejection and non homogeneous distribution of the source abstract in this paper numerical methods derived in part i chem geol 2002 are expanded to accommodate the effects of emission and zonation of u and th as relevant for u th he thermochronology expressions for the required coefficients are derived for spheres finite and infinite cylinders and rectangular blocks for parent nuclide distributions which are either uniform or have stepwise zoning we show that the effects of emission and zonation on the he retention in a nonspherical crystal of modest aspect ratio can be approximated by a sphere of identical surface to volume ratio s v if the zonation is transposed on to the sphere the currently usual correction method is to perform first a diffusive calculation without considering emission and zonation and to multiply afterward with a correction factor that has been derived originally for nondiffusive calculations our results demonstrate that more accurate calculations yield different results and that the differences are often too large to be ignored in practice especially for thermal histories that include a protracted residence in the partial retention zone the difference between the usual correction and our correction can be as high as 20 for homogeneous sources for zoned crystals the difference can be even larger

earth fissures triggered by groundwater withdrawal and coupled by geological structures in jiangsu province china earth fissures in jiangsu province china have caused serious damages to properties farmlands and infrastructures and adversely affected the local or regional economic development under the geological and environmental background in jiangsu province this paper presents the earth fissures caused by excessive groundwater withdrawal and coupled by distinctive geological structures such as ancient yellow river fault in xuzhou karst area and ancient yangtze river course and bedrock hills in suzhou wuxi and changzhou area although all the earth fissures are triggered by groundwater exploitation the characteristics are strongly affected by the specific geological and hydrogeological settings in particular in the water thirsty xuzhou city the cone of depression caused by groundwater extraction enlarged nearly 20 times and the piezometric head of groundwater declined 17 m over a decade as groundwater is extracted from the shallowly buried karst strata in the ancient yellow river fault zone the development of earth fissures is highly associated with the development of karstic cavities and sinkholes and their distribution is controlled by the ancient yellow river fault with all the 17 sinkholes on the fault on the other hand in the rapidly developing southern jiangsu province groundwater is mainly pumped from the second confined aquifer in the quaternary which is distributed neither homogeneously nor isotropically the second confined aquifer comprises more than 50 m thick sand over the ancient yangtze river course but this layer may completely miss on the riverbank and bedrock hills with a typical drawdown rate of 4 6 m per annum the piezometric head of groundwater in the second confined aquifer has declined 76 m at maocunyuan since 1970s and 40 m at changjing since mid 1980s and a large land subsidence e g 1 100 mm at maocunyuan is triggered coupled with the dramatic change of the bedrock topography that was revealed through traditional geological drilling and modern seismic reflection methods the geological structure controlled differential settlement and earth fissures are phenomenal in this area

deep permeable fault controlled helium transport and limited mantle flux in two extensional geothermal systems in the great basin united states this study assesses the relative importance of deeply circulating meteoric water and direct mantle fluid inputs on near surface 3 he 4 he anomalies reported at the coso and beowawe geothermal fields of the western united states the depth of meteoric fluid circulation is a critical factor that controls the temperature extent of fluid rock isotope exchange and mixing with deeply sourced fluids containing mantle volatiles the influence of mantle fluid flux on the reported helium anomalies appears to be negligible in both systems this study illustrates the importance of deeply penetrating permeable fault zones 10 12 to 10 15 m 2 in focusing groundwater and mantle volatiles with high 3 he 4 he ratios to shallow crustal levels these continental geothermal systems are driven by free convection

apatite u th he thermochronometry as an innovative geothermal exploration tool a case study from the southern wassuk range nevada abstract extensional type geothermal systems are complicated by the interrelation between footwall advection during exhumation and the subsequent redistribution of heat by migrating hydrothermal fluids in the hanging wall the southern wassuk range wr hanging wall hosts a moderate temperature extensional type geothermal system and is ideal for studying this duality by analyzing a suite of apatite ahe and zircon zhe helium samples from the footwall and hanging wall of the southern wr young 3 4 ma ahe ages along the wr front are concentrated along the se corners of segmented footwall blocks marking the location of focused mio pliocene transtension fracture dilation and advection hydrothermally reset ahe ages along the footwall range front suggest that the hawthorne geothermal system 85 135 c is long lived and has resided at a prominent structural boundary in the wr footwall marked by localized advection and range front deformation in contrast the presence of both hydrothermally reset and non reset ahe ages from a 1 4 km deep borehole in the hanging wall basin probably indicate that the geothermal plumbing system and current manifestation as a thermal anomaly 113 c are juvenile and are controlled by the generation of newly formed faults in the hanging wall ahe ages have been shown here to greatly enhance the focusing of regional scale geothermal exploration efforts and for the first time have been used to identify and estimate the temperature of unseen hydrothermal fluids

study of the time space strength relation for mining seismicity at laohutai coal mine and its prediction mining seismicity is akin to an arti cial earthquake caused by mining activities mining seismicity has a long history in chinese coal mines among which laohutai coal mine in fushun city which is located in liaoning province northeast of china is a typical one 1 laohutai mine is located at the south edge of fushun city its geographical coordinates are east longitude 123o54 42 123o58 17 north latitude 41o51 07 41o52 10 the mine is 4 95 km from east to west and about 2 km from south to north so the mine area is about 10 km2

analytical solution of energy redistribution in rectangular openings upon in situ rock mass alteration abstract this paper aims at deriving analytical expressions of mining induced energy redistribution around rectangular openings that involve local alteration of rock mass properties as energy combines the effects of strains and stresses simultaneously this research work is intended to complement existing approaches that rely on stress based stability criteria the energy density on the boundaries and its distribution within the domain obtained analytically through direct derivation is compared to numerical solutions obtained by finite element simulation for a given hypothetical field case the analytical and numerical solutions show a good agreement and reflect the importance of analytical solutions especially in the vicinity of severe geometrical singularities our parametric study shows that the initial stress coefficient and opening span height ratio have great influence on the variation of strain energy density we found that the energy density concentrates on the excavation corners and that the energy density concentration index value on the opening side boundary decreases when the span height ratio decreases areas of energy reduction appear on the excavation boundaries which transform from the top centers to the side centers as the initial stress coefficient increases our study indicates that both energy density concentration and reduction areas need to be considered in excavation design the derived expressions of mining induced energy redistribution can be considered as a tool to assess the stability of rock masses and predict failure conditions such as rock burst and mine seismicity around non circular shaped openings

land subsidence and caprock dolines caused by subsurface gypsum dissolution and the effect of subsidence on the fluvial system in the upper tigris basin between bismil batman turkey abstract karstification based land subsidence was found in the upper tigris basin with dimensions not seen anywhere else in turkey the area of land subsidence where there are secondary and tertiary subsidence developments reaches 140 km 2 subsidence depth ranges between 40 and 70 m the subsidence was formed as a result of subsurface gypsum dissolution in lower miocene formation although there are limestones together with gypsum and eocene limestone below them in the area a subsidence with such a large area is indicative of karstification in the gypsum the stratigraphical cross sections taken from the wells and the water analyses also verify this fact the lower miocene gypsum which shows confined aquifer features was completely dissolved by the aggressive waters injected from the top and discharged through by zellek fault this resulted in the development of subsidence and formation of caprock dolines on loosely textured upper miocene pliocene cover formations the tigris river runs through the subsidence area between batman and bismil there are four terrace levels as t1 40 m t2 30 m t3 10 m and t4 4 5 m in the tigris river valley it was also found that there were some movements of the levels of the terraces in the valley by subsidence the subsidence developed gradually throughout the quaternary however no terrace was formed purely because of subsidence

paleosubsidence and active subsidence due to evaporite dissolution in the zaragoza area huerva river valley ne spain processes spatial distribution and protection measures for transport routes abstract the lowest 17 km long reach of the huerva river valley down to its confluence with the ebro river in zaragoza city flows across salt bearing evaporites of the ebro tertiary basin ne spain upstream the horizontally lying miocene evaporites are interfingered with non soluble distal alluvial fan facies shales and sandstones the proportion of soluble facies in the huerva river valley increases in a downstream direction towards the basin depocenter on the basis of the type and magnitude of the paleosubsidence features the valley has been divided into four reaches along reach i undeformed terrace deposits less than 4 m thick rest on insoluble detrital bedrock in reaches ii and iii dissolution at the alluvium bedrock boundary has generated local thickening deformation and paleocollapse structures which only affect the alluvial mantle in reach iv terrace deposits thicken to over 60 m resulting from a large scale synsedimentary subsidence in this sector subsidence locally affects to both the alluvium and the underlying bedrock this indicates that dissolution acts at the rockhead beneath the alluvial cover alluvial karst and within the evaporitic substratum interstratal karst the development of an intraevaporitic karst in reach iv is attributed to gypsum and salt dissolution irregular terrace gravel bodies gravel pockets embedded in a fine grained matrix associated with paleocollapse structures have been interpreted as liquefaction fluidization structures resulting from ground acceleration and suction induced by catastrophic collapses subsidence is currently active in the region affecting areas with a thin alluvial cover in reaches iii and iv the low subsidence activity in most of zaragoza city is explained by the presence of thickened around 50 m and indurated alluvial deposits in the surrounding area numerous buildings in cadrete and santa fe villages have been severely damaged by subsidence natural and human induced subsidence favours the development of slope movements in the gypsum scarp overlooking cadrete village several transport routes including the imperial canal irrigation canal and the recently completed madrid barcelona high speed railway are affected by human induced sinkholes the paleocollapse structures exposed in the trenches of this railway and a ring road under construction point to hazardous locations underlain by cavities and collapse structures where special protection measures should be applied rigid structures are recommended beneath the high speed railway with sufficient strength to span the larger sinkholes with no deformation electronic monitoring devices linked to a warning system can detect subtle subsidence induced deformations in carriageways or railways this research demonstrates that the study of the paleokarst helps to understand the processes involved in the present day subsidence phenomena and their general spatial distribution

subsidence hazards due to evaporite dissolution in the united states evaporites including gypsum or anhydrite and salt are the most soluble of common rocks they are dissolved readily to form the same type of karst features that typically are found in limestones and dolomites and their dissolution can locally result in major subsidence structures the four basic requirements for evaporite dissolution to occur are 1 a deposit of gypsum or salt 2 water unsaturated with caso4 or nacl 3 an outlet for escape of dissolving water and 4 energy to cause water to flow through the system evaporites are present in 32 of the 48 contiguous states of the united states and they underlie about 35 40 of the land area karst is known at least locally and sometimes quite extensively in almost all areas underlain by evaporites and some of these karst features involve significant subsidence the most widespread and pronounced examples of both gypsum and salt karst and subsidence are in the permian basin of the southwestern united states but many other areas also are significant human activities have caused some evaporite subsidence development primarily in salt deposits boreholes may enable either intentionally or inadvertently unsaturated water to flow through or against salt deposits thus allowing development of small to large dissolution cavities if the dissolution cavity is large enough and shallow enough successive roof failures above the cavity can cause land subsidence or catastrophic collapse

geologic setting and genesis of the mule canyon low sulfidation epithermal gold silver deposit north central nevada the mule canyon mine exploited shallow low sulfidation epithermal au ag deposits that lie near the west side of the northern nevada rift in northern lander county nevada mule canyon consists of six small deposits that contained premining reserves of about 8 2 mt at an average grade of 3 81 g au tonne it is an uncommon mafic end member of low sulfidation au ag deposits associated with tholeiitic bimodal basalt rhyolite magmatism the ore is hosted by a basalt andesite eruptive center that formed between about 16 4 to 15 8 ma during early mafic eruptions related to regionally extensive bimodal magmatism hydrothermal alteration and au ag ores formed at about 15 6 ma and were tightly controlled by north northwest to north striking high angle fault and breccia zones developed during rifting emplacement of mafic dikes and eruption of mafic lava flows hydrothermal alteration assemblages are zoned outward from fluid conduits in the sequence silica adularia adularia smectite smectite intermediate argillic and smectite carbonate propylitic all alteration types contain abundant pyrite and or marcasite arsenopyrite field relations indicate that silica adularia alteration is superimposed on argillic and propylitic alteration little or no steam heated acid sulfate alteration is present probably the result of a near surface water table during hydrothermal alteration and ore deposition two distinct ore types are present at mule canyon early replacement and later open space filling replacement ores consist of disseminated and vesicle filling pyrite marcasite and arsenopyrite in argillically altered or weakly silicified rocks ore minerals consist of au bearing arsenopyrite and arsenian pyrite overgrowths on earlier formed pyrite and marcasite open space filling ores include narrow stockwork quartz adularia veins banded and crustiform opaline and chalcedonic silica adularia veins silica adularia cemented breccias and sparse carbonate pyrite and or marcasite veins ore minerals consist mostly of electrum and ag sulfide and selenide minerals with minor to major amounts of pyrite marcasite and arsenopyrite and local stibnite both types of ores have similar geochemical signatures characterized by high au ag as sb and se contents locally high hg mo tl and w contents and low cu pb and zn contents stable isotope data indicate that ore fluids consisted dominantly of meteoric water that evolved by deep circulation through paleozoic sedimentary rocks at low water rock ratios about 1 and high temperatures 200 c calculated isotopic compositions of ore fluids are 18oh2o 3 to 7 per mil dh2o 107 to 124 per mil 13cco2 0 to 6 per mil and 34sh2s 3 to 8 per mil the ore fluids obtained much of their h2s and co2 and probably scavenged ore metals and trace elements from the paleozoic sedimentary rocks some h2s and co2 may have been derived from degassing miocene magmas mule canyon formed at shallow depths probably about 100 m below the paleosurface ore fluids were dilute nearly neutral in ph reduced h2s rich and co2 bearing peak temperatures in ore zones reached 230 to 265 c at nearly lithostatic pressures when some crystalline quartz adularia precipitated but most ore formed at temperatures 200 c at near hydrostatic pressures and was accompanied by precipitation of opaline and chalcedonic silica adularia calcite and dolomite deposition of gold in as rich overgrowths on pyrite and or marcasite in disseminated ores occurred owing to decreasing h2s in the ore fluids resulting from sulfidation reactions later electrum and ag selenide precipitation in open spaces occurred owing to boiling loss of h2s to the vapor phase and cooling mule canyon is similar to most other low sulfidation au ag deposits associated with miocene tholeiitic bimodal basalt rhyolite magmatism in the great basin such as sleeper midas and buckhorn major differences at mule canyon are the high fe sulfide contents of some ores and altered wall rocks the paucity of silicification and the presence of only narrow and discontinuous gold bearing siliceous veins these differences primarily are due to the mafic composition of the host rocks mule canyon differs from low sulfidation deposits associated with subduction related calc alkaline porphyry intrusions such as the comstock lode in that a much smaller proportion of water salts and metals was derived from crystallizing magmas

the formation of cover collapse sinkholes in north of hamedan iran abstract most sinkholes in the hamedan region central plain in western iran are developed in partially unconsolidated sediments overlying oligo miocene limestone analyses of hydrologic and hydrogeologic conditions from 1988 to 2008 show that conditions were favourable for sinkhole development these sinkholes developed in groundwater discharge areas near the base of karstic oligo miocene limestone in zones with major groundwater circulation thick overburden and a close proximity to deep source carbon dioxide gas high carbon dioxide partial pressures caused by rising gases from pneumatolytic and hydrothermal phase sources renew the aggressiveness of the water in the vicinity of the discharge zone the acidic water dissolves limestone especially along the fractures and joints moreover the presence of large conduits below the surface allows for the transport of unconsolidated sediments and the continual development of sinkholes

distribution and morphology of sinkholes triggered by flooding following tropical storm alberto at albany georgia usa abstract flooding of the flint river in july 1994 triggered the collapse of at least 312 sinkholes in the karstic dougherty plain at albany georgia we examined the distribution and morphology of these new sinkholes to evaluate the mode of formation to characterize early stages of the evolution of sinkhole form and to estimate the lowering of the surface associated with the development of new sinkholes eighty eight percent of sinkholes occur inside the limits of flooding especially in areas of sandy overburden and they often follow joint controlled linear trends sinkhole dimensions are log normally distributed with median values of circumference 5 7 m length 1 8 m width 1 6 m and depth 0 7 m asymmetry l w 1 2 cross sectional forms range from narrow cylinders to large bowls with many sinkholes having undercut sides flooding triggered the formation of sinkholes by saturating and liquefying overburden which caused soil arches to collapse and flow into cavities in bedrock the prevalence of sinkholes near the periphery of flooding suggests that drainage and loss of buoyant support as flood waters subsided may also have contributed to failure a volume ratio index is used to quantify the three dimensional geometric form of sinkholes initially small cylindrical shafts open over a bedrock joint followed by progressive slumping that leads to widening and increases in volume to a final bowl form estimates of the aggregate volume of overburden transported underground in flooded areas range from 7 990 to 11 130 m3 averaged over flooded areas this accounts for 0 26 to 0 37 mm km2 lowering of the surface based on a 500 year recurrence interval for the flood event values for lowering of the surface range from 0 52 to 0 74 mm per 1 000 years these values are an order of magnitude less than estimates of carbonate dissolution and suggest that transport of overburden underground is limited by triggering events

cainozoic evolution of the state of stress and style of tectonism of the basin and range province of the western united states cainozoic evolution of the modern plate boundary along the western united states from subduction to a predominantly transform boundary coincided with a change from compressional to extensional deformation in the western united states extensions tectonism responsible for the modern basin and range province appears to represent a unique late stage episode of a much longer period of extension initiated in an in tra arc setting contemporaneously with calc alkaline magmatism basin range extension is distinguished from early extension on the basis of angular unconformities differences in fault trends and spacing and associated magmatism basaltic prebasin range extension i e extension preceding the break up of the region into ranges resembling the modern ones was under way locally by at least 30 ma and is now recognized by faulted and highly tilted strata exposed in uplifted range blocks by large regions of the crust underlain by passively emplaced subvolcanic batholiths and by the thickness and distribution of stratigraphic units locally high strain rates that accompanied early extensions of as much as 50 100 are implied data on preferentially orientated dyke swarms and fault slip vectors indicate a strikingly uniform wsw ene least principal stress orientation in the period ca 20 10 ma during this early extension the change from early extension to basin range style faulting of the upper 15 km of crust which resulted in broadly spaced ranges 25 35 km crest crest spacing was time transgressive and probably not abrupt locally both types occurred concurrently southern basin and range block faulting occurred largely in the period 13 10 ma in response to a stress field orientated similarly to that responsible for the early extension in contrast northern basin and range block faulting developed after 10 ma and continues to the present in response to a stress field orientated approximately 45 clockwise to the earlier stress field this modern stress field with a wnw ese to e w directed least principal stress characterizes the entire modern basin and range province and rio grande rift region the 45 change in least principal stress orientation is consistent with superposition of dextral shear associated with the development of the san andreas transform fault inclusion of pre basin range extension may help resolve the discrepancy between estimates of 15 30 for basin range block faulting and total extension estimates of 100 300 for the basin and range province

use of mining and seismological parameters as premonitors of rockbursts abstract comprising one of the deepest mines in the world the gold mining region of the kolar gold fields kgf in southern india is known to be confronted with the acute problem of rockbursts that pose a hazard to workmen and cause disruptions in the production schedule in combination with mining parameters seismological data of these rockbursts events systematically monitored over the years using a regional seismic network have been employed to examine and model premonitory characteristics of the events linear empirical relations are established relying on correlations seen between the seismic energy released due to a rockburst total tonnage of ore mined out and total number of rockbursts as well as seismic events in some shallow and deep workings currently active at kgf the deterministic model although not free from certain limitations at present has been applied to predict rockburst activity with some success

halite karst geohazards natural and man made in the united kingdom in the united kingdom permian and triassic halite rock salt deposits have been affected by natural and artificial dissolution producing karstic landforms and subsidence brine springs from the triassic salt have been exploited since roman times or possibly earlier indicating prolonged natural dissolution medieval salt extraction in england is indicated by the names of places ending in wich indicating brine spring exploitation at northwich middlewich nantwich and droitwich later victorian brine extraction in these areas accentuated salt karst development causing severe subsidence problems which remain a legacy the salt was also mined but the mines flooded and consequent brine extraction caused the workings to collapse resulting in catastrophic surface subsidence legislation was enacted to pay for the damage and a levy is still charged for salt extraction some salt mines are still collapsing and the re establishment of the post brine extraction hydrogeological regimes means that salt springs may again flow causing further dissolution and potential collapse

road construction over voids caused by active gypsum dissolution with an example from ripon north yorkshire england sudden subsidence problems caused by gypsum karst developed in the permian sequence of northern england have caused difficult conditions for road construction this paper presents the design strategy mathematical modelling and parameters used to construct roads to cope with such difficult ground conditions because it is impossible to locate all the subsidence features along a route the road design has to cope with potential future problems this is achieved by using reinforcement comprising layers of tensile membrane material within the earth embankment this will prevent dangerous catastrophic collapse and maintain serviceability but will allow sagging to show where major problems exist the modelling showed that for the situation at ripon two layers of tensile membrane material within the earth embankment fulfilled the design brief for the road

karst database implementation in minnesota analysis of sinkhole distribution this paper presents the overall sinkhole distributions and conducts hypothesis tests of sinkhole distributions and sinkhole formation using data stored in the karst feature database kfd of minnesota nearest neighbor analysis nna was extended to include different orders of nna different scales of concentrated zones of sinkholes and directions to the nearest sinkholes the statistical results along with the sinkhole density distribution indicate that sinkholes tend to form in highly concentrated zones instead of scattered individuals the pattern changes from clustered to random to regular as the scale of the analysis decreases from 10 100 km2 to 5 30 km2 to 2 10 km2 hypotheses that may explain this phenomenon are 1 areas in the highly concentrated zones of sinkholes have similar geologic and topographical settings that favor sinkhole formation 2 existing sinkholes change the hydraulic gradient in the surrounding area and increase the solution and erosional processes that eventually form more new sinkholes

closed depressions in the european loess belt natural or anthropogenic origin abstract closed depressions cds are typical geomorphological features of the loess belt in europe cds have been reported in several regions of the european loess belt where they are described as hollows mardeles wymoki crovuri bludtsa and zapadiny the natural and anthropogenic origins of cds are debated in literature moreover no comprehensive review of the geomorphic properties or the evolution of these depressions exists therefore this paper reviews the characteristics of cds in the european loess belt and attempts to better understand their genesis based on detailed case studies the main morphometric features as well as sediment deposits within cds in several sub regions of europe were analysed and compared morphometric properties of cds from the west european and east european loess belt were investigated through a comparison of cds from two representative regions i e east poland and central belgium in both study areas cds under cropland are similar however a comparison of morphological features of cds under forest revealed clear differences suggesting a different origin of cds from both regions infilled sediments in cds show various litho genetical features in different regions of the european loess belt the morphometric features ages and stratigraphy of infillings clearly indicate that both anthropogenic and natural processes have shaped these landforms within the loess belt of europe cds observed in eastern europe may have a very different origin than those documented in western europe detailed analysis of cds in poland and in neighbouring regions of east europe suggest that cds are natural landforms thermokarst deflation and dissolution of loess are reported as probable genetic processes in contrast several studies in western europe indicate a dominant anthropogenic origin i e digging of calcareous loess or marls bomb and mining craters collapse of underground limestone quarries although cds formed by natural processes i e piping dissolution of limestone and salt lenses below the loess cover are reported as well cds act as important archives allowing one to reconstruct both natural and anthropogenic processes operating in the past as cds store most sediments eroded within their catchment they provide ideal sediment traps to assess long term erosion rates in these environments which have hitherto been under researched more research is needed to unravel the genesis and evolution of these depressions to better understand the importance of the late glacial and holocene stages for the morphogenesis of the loess belt in europe

thermochronological constraints on the timing and magnitude of miocene and pliocene extension in the central wassuk range western nevada apatite fission track and u th he thermochronological data provide new constraints on the timing of faulting and exhumation of the wassuk range western nevada where east dipping normal faults have accommodated large magnitude ene wsw oriented extension extensional deformation has resulted in the exhumation of structurally coherent fault blocks that expose sections of preextensional mostly granitic upper crust in the grey hills and central wassuk range these fault blocks display westward tilts of 60 and expose preextensional paleodepths of up to 8 5 km based on the structural reconstruction of tilted preextensional tertiary andesite flows that unconformably overlie mesozoic basement rocks apatite fission track and u th he thermochronological data from the fault blocks constrain the onset of rapid footwall exhumation at 15 ma fission track modeling results indicate rapid fault block exhumation occurred between 15 and 12 ma which is in agreement with miocene volcanic rocks that bracket the tilting history in addition fission track and u th he data suggest reduced rates of cooling following major extension as well as renewed cooling related to active high angle faulting along the present day range front starting at 4 ma thermochronological data from structurally restored fault blocks indicate a preextensional miocene geothermal gradient of 27 5 c km the thermochronological constraints on the timing of extensional faulting and the eruptive history in the wassuk range imply a model for extension where crustal heating and volcanism precede the onset of rapid large magnitude extension and where synextensional magmatism is suppressed during the highest rates of extension

geothermal mineralization i the mechanism of formation of the beowawe nevada siliceous sinter deposit the siliceous sinter deposit at beowawe nev has a volume of 7 71 x 10 sup 7 m sup 3 and contains 1 28 x 10 sup 11 kg silica this silica precipitated from geothermal solutions that welled up along the malpais fault a graben bounding fault sinter formation involved three steps 1 geothermal solutions saturated with quartz in the reservoir moved to the surface where they cooled and became supersaturated with amorphous silica 2 amorphous silica particles nucleated heterogeneously to produce a colloidal suspension 3 the amorphous silica particles agglomerated and were cemented together by amorphous silica precipitating in the embayments between the particles at least 5 58 x 10 sup 14 kg of geothermal solution must have been produced over time to account for the mass of silica in the beowawe deposit this fluid would have carried at least 4 95 x 10 sup 17 kj of heat to the surface 21 references 6 figures 1 table

sinkhole formation above underground limestone quarries a case study in south limburg belgium abstract historical records were used for the compilation of a database of sinkholes resulted from collapses of abandoned shallow underground limestone quarries mines in two villages in belgian south limburg during the last 350 years the formation of such sinkholes caused at least 38 casualties but more often it caused a change in topography and damage to public and private property the objective of this study is to better understand the spatial and temporal patterns of quarry collapse related sinkholes in the study area apart from sinkhole locations and ages the compiled database provides information on the dimensions of the area affected and the damage caused by sinkhole formation as well as the causal factors of sinkholes one hundred seventy three sinkholes have been reported since 1665 but most 80 reported sinkholes postdate 1965 sinkhole dimensions provided information on the type of collapse seven large sinkholes displacing a total sediment volume of 480 000 m3 resulted from large scale roof breakdown after pillar failure the smaller sinkholes were the result of fall of the overburden into galleries after local roof collapse or suffosion of a solution pipe in total these small sinkholes displaced 12 300 m3 of sediment at present almost all large underground quarries in the study area have been affected by sinkholes these features were caused by natural and anthropogenic factors and occur in zones with thin roofs where pillars were affected by pillar robbing or on locations with inappropriate sewerage systems above quarries the formation of sinkholes was often reported in spring during years with high moisture contents in the overburden caused by high groundwater recharge or above average precipitation with increasing time since quarry abandonment quarries become more susceptible to pillar creep and bending of the roof hence if no appropriate mitigation measures are taken to reduce such deterioration processes the number of sinkholes is expected to increase

mining induced seismicity seismic measurement using multiplet approach and numerical modeling the volume of influence of mining works is essentially determined from in situ observations field measurements particularly surface subsidence measurements as well as from numerical investigations seismic monitoring is the primary requirement for mining in rock burst environment a micro seismic network is systematically used to monitor coal extraction in the provence colliery south eastern france a significant database of seismic events is now available a further advancement in this sequence was added by the development of doublets technique or multiplet selections the technique uses with the database to identify families of seismic events and to work out the relative locations of these events the analysis of location of these multiplet families showed a particular spatial distribution locations of the epicentre follow the direction in which the coalface is advancing numerical models are used in the paper to show the overstress distribution by comparing the seismic activity and results of the numerical modeling of the advancing coalface with observations a close correlation can be established between the location of seismic activity and induced stresses in the ground surface of the working areas by combining micro seismic monitoring with the numerical modeling the volume of influence of long wall mines is determined results show that such a coupling can be an efficient way for detecting areas subjected to rock burst hazards this can also prove to be a powerful tool for assisting the planning of underground workings in complex geological and mining conditions

the origin of closed depressions in northeastern france a new assessment over 10 000 closed depressions cds are found in the silty plains of northeastern france these small wetlands support the growth of rare plant species although their origins which could be anthropogenic or geologic due to salt gypsum lens dissolution have been debated for 150 years they have not yet been the focus of an integrated study in 39 geological borings along a 15 km strip no salt gypsum lenses and more than 260 cds were recorded using lidar all of the investigated cds have a bathtub form with a flat bottom complete excavations clearly showed a cut contact between the sediment and the horizontal marl substratum at the bottom and a cut at the edges of the upper marl layers radiocarbon dating of sediment bottoms showed that sedimentation began between the second iron age and the roman period the frequencies of pollen and sporormiella type depict an open landscape with grassland pasture and cropland these convergent findings challenge the hypothesis that cds formed naturally and suggest that they area instead anthropogenic because no soil deposits were found around the cds digging may have been intended to marl the surrounding acidic silty soils the high density and small size of cds will allow the detailed reconstruction of landscape and biodiversity modifications in the region for the two last millennia

influence of geomorphological constraints and exploitation techniques on stone quarry spatial organisation abstract the lutetian limestones were used to build numerous historical monuments in the north east part of france in rheims laon and soissons areas more than 400 underground quarries have been inventoried by research in the regional archives on old maps and by several months of ground prospecting actually most of these underground quarries are abandoned only 3 are now open in the soissons area in the rheims region the last active quarry located at courville village was closed in 2005 because of the safety conditions the aim of the study was to demonstrate the importance of geomorphological context on the fracturing network and on the quarry spatial organisation underground topography fracturing network measurement aerial mapping and analysis of the geomorphological features show the high connection between natural constraints and extraction choices and may explain the progressive disappearance of building stone quarries in a part of the studied area in the east of the studied area where the usable limestone has a weak thickness and important mechanical distension stress the galleries direction depends on fracturing network in contrast in the west soissons area limestone shows thick homogeneous facies that allow a rational extraction using room and pillars mining system

characterization and quantification of active faulting in the roer valley rift system based on high precision digital elevation models the roer valley rift system rvrs is located in the northern prolongation of the upper rhine graben during the cenozoic the evolution of the rvrs was influenced by two different rift systems situated in the north and in the south the north sea rift system and the west european rift system respectively during the last decades moderate seismicity revealed the continuous activity of the graben border faults the peel boundary fault zone pbfz and the feldbiss fault zone ffz we use a high precision digital elevation model dem to characterize and quantify the present day deformation along these faults the fault pattern shows similarity to a strike slip structure however analysis of the dem reveals that the recent to quaternary formations and landforms affected by the fault activity are only vertically offset this suggests a pure normal faulting mode for the main border faults and a direction of extension perpendicular to the graben i e ne sw quantification of the offset dated markers allows the determination of the displacement rates along the fault segments in the southeastern part of the rvrs the vertical displacement rates inferred for the ffz and the southeastern pbfz range between 55 and 65 mm ky and around 65 mm ky respectively in contrast the displacement rates determined for the northwestern segment of the pbfz are around 200 mm ky we explain these differences between the northwestern and southeastern parts of the rvrs by the large scale geometry of the graben the rvrs being symmetric in the south east and asymmetric half graben in the north west the deformation is accommodated by two border faults ffz and the south eastern part of the pbfz in the south east and by only one fault in the north west the north western segment of the pbfz in addition the thickness of the neogene main depocentre in the northwestern half of the rvrs indicates a larger amount of extension in this part of the graben than in the south east the combination of the graben geometry and the amount of extension can explain the differences in the displacement rate

geological and geophysical evidence for large palaeo earthquakes with surface faulting in the roer graben northwest europe from the analysis of geological geodetic and geophysical data we provide clear evidence of seismogenic faults capable of producing large earthquakes in intraplate europe previous studies paulissen vandenberghe gullentops 1985 van den berg et al 1994 geluk et al 1994 have yielded some constraints on the rate of crustal deformation along the roer valley a graben structure crossing the netherlands belgium and germany and have allowed us to address the fundamental questions can intraplate earthquakes rupture the surface in this part of stable continental europe and if so what is their return period detailed palaeoseismic investigations have been carried out in belgium along a 10 km long fault scarp which is the morphological expression of the feldbiss fault the southwestern border fault of the roer graben camelbeeck meghraoui 1996 the scarp is multiple and the frontal fault scarp offsets young deposits and alluvial terraces field investigations using geological and geomorphological methodologies combined with geophysical prospecting provide evidence of holocene seismic surface faulting from 14c dating it is suggested that the last earthquake along the fault scarp occurred between 610 ad and 890 ad levelling profiles across the scarp suggest that it produced a vertical coseismic displacement of 0 5 1 m along the scarp if we suppose that the last surface faulting earthquake ruptured the whole seismogenic layer 17 km thickness over a minimum length 10 km corresponding to the length of the bree scarp with an average slip of 0 6 m its seismic moment was at least 3 1 1018 n m mw 6 3 for an average rigidity 3 1010 pa by estimating the offset of the main terrace of the maas river by slippage along the feldbiss fault we calculate the average late pleistocene vertical deformation rate as 0 08 0 04 mm yr 1 palaeoseismic information combining the trench and geomorphic observations suggests the occurrence of two surface faulting earthquakes during the last 20 kyr a third dates before 28 35 kyr bp then if the time distribution of earthquakes is uniform a return period of 12 5 ka and a vertical deformation rate of 0 06 0 04 mm yr 1 are inferred