failure process and modes of rockfall induced by underground mining a case study of kaiyang phosphorite mine rockfalls abstract the analysis of the failure processes and mechanisms of rockfalls that are associated with underground mining activities is presented the study area is located in kaiyang phosphorite mine in southwest china where the geological condition is dominated by anti dip slopes with layers inclined backward into the natural slope with decreasing strength in the rock mass from the upper dolomite rich to the lower shale rich strata the analysis is based on field investigation and laboratory experimental study using a gravitational simulation device the results support the proposed failure mechanism by demonstrating the process of failure from the deformation of the roof and floor in the stopes to the development of surface cracks near the top of slopes and eventually to the formation of rockfalls as the surface cracks propagate along pre existing joints the rockfalls are classified into one of three failure modes crack toppling crack sliding and crack slumping in which the failures are governed by the corresponding characteristics of the rock mass structure the study of the failure process and their spatial and temporal correlation with the underground workings reveals warning signs or indicators of impending slope instability improved understanding of the failure process and indicators can aid in early identification and timely warning of geohazards in phosphorite mines

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

recent progress in snow and ice research a review of snow and ice research in 1987 1990 is presented focusing on the effects of layers in seasonal snow covers ice mechanics on fresh water and sea ice and remote sensig of polar ice sheets these topics provide useful examples of general needs in snow and ice research applicable to most areas such as better representation in models of detailed processes controlled laboratory experiments to quantify processes and field studies to provide the appropriate context for interpretation of processes from remote sensing

karst collapse susceptibility assessment a case study on the amalfi coast southern italy abstract this paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the amalfi coast southern italy and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse in the study area several natural karst caves with volumes varying between 1000 and 10 000 m 3 were inventoried and the most likely genetic processes were identified some of them proved to be remnants of already collapsed caves while others were in precarious stability conditions the caves are usually located upslope or very close to the main populated resorts a detailed geological geomorphological and geostructural study was performed on a very wide deep cave called the saraceno cave on which the resort town of conca de marini has been built the study was carried out through a multidisciplinary approach which included classical field geological observations sometimes requiring the support of rock climbing geologists experts in photogrammetric surveys and terrestrial laser scanning techniques tls tls surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope conca de marini resort furthermore it allowed the thickness of the cave overburden to be determined in detail ground surfaces most susceptible to collapse were also identified in the event of possible widespread collapse several buildings and transportation infrastructures could be involved as the cave is located on a very steep slope a debris avalanche could be triggered in the event of a catastrophic failure and the landslide debris characterized by a presumably high magnitude and velocity could involve a wide slope area down to the coast the failure evolution could be very similar to that which took place in amalfi in the late 19th century

collapse of caves at shallow depth in gaziantep city center turkey a case study this paper focuses on an investigation of the possible causes for the collapse of limestone caves in gaziantep turkey the city contains a lot of man made caves at a shallow depth of various width and length these caves were mainly excavated to provide work or storage space as the city has been growing fast with increased population many structures were constructed over these caves recently two caves collapsed and five houses were damaged these caves are all made of limestone and it was observed after the collapse that the limestone was saturated with water due to sewer pipe leakage and surface water tests were carried out on the limestone and it was determined that the compressive strength of limestone decreases by about 50 and the tensile strength decreased by about 80 when saturated with water it was concluded that the reduced strength of the limestone combined with additional loads due to the factors mentioned above seem to be the main reason for these collapses

development and morphometry of sinkholes in coastal plains of apulia southern italy preliminary sinkhole susceptibility assessment abstract evolution of coastlines in karst areas may be strongly controlled by dissolution processes which favour the development of surface and subsurface landforms the generation of caves in these environments is commonly favoured by the mixing between fresh and brackish waters the sinkholes resulting from the upward propagation of the caves may interfere with the anthropogenic environment and cause damage to human elements property and activities to highlight the often underestimated importance of karst phenomena in coastal areas we have analyzed a coastal stretch of apulia in southern italy the study area covering an extension of about 6 km 2 is situated in the ionian coast and presents several interesting karst landforms that are generally connected to caves tens of sinkholes were mapped through field surveys multi year aerial photographs dating back to the 1940s and archival research we have performed a morphometric analysis of the sinkholes the analysis describes the main parameters of the sinkholes area length width and depth and the control exerted by the main discontinuity systems in the area the detrimental effects derived from interaction between human environment and these karst landforms is also under consideration a sinkhole susceptibility map which may provide useful information for planners developers and the insurance industry has eventually been produced through application of a decision tree model

recent underground investigations of abandoned chalk mine workings beneath norwich city norfolk abstract the city of norwich is underlain at shallow depth by abandoned mineworkings made for the extraction of chalk and flints early workings took the form of surface pits and quarries with later working of underground mines the latter often several hundred years old are liable to collapse and may reach the ground surface most of the mines are now inaccessible although the recent investigation of two such mines has included the use of direct mining techniques to gain access to the old workings stability at harford mine has been found to be adequate due to adequate rock cover moderate age and a rural setting collapses at earlham road mine have been found to be well developed due to inadequate rock cover great age poor rock quality and disturbance due to the urban location the principal collapse mechanism is identified as localised void migration following roof collapse with a possible secondary contribution from pillar over stressing

discrete element modeling of progressive failure in a wide coal roadway from water rich roofs abstract progressive failure of roadway roofs is a common failure mechanism in underground coal mines especially when water rich roofs are in close proximity to the roadway in this case study at a chinese coal mine the udec voronoi method was used to investigate the process of progressive roof failure in a wide coal roadway from water rich roofs in the numerical scheme the studied domain was partitioned into polygonal blocks bonded through contacts with pre defined dimensions the parameters of polygons and contacts in the voronoi program were calibrated to rock mass properties obtained through laboratory tests based upon laboratory tests and previous research findings a time dependent strength degradation process from water absorption was assumed and implemented in the numerical modeling next the progressive failure of a roadway from water rich roofs was analyzed in detail the numerical results agreed well with field measurements and observations this method was demonstrated to reproduce the real phenomenon of roof failure in all of its complexity the numerical results revealed that the progressive failure mechanism was characterized by an initial fracturing of the roof due to strength degradation which was followed by significant dilation as fractures grew the large span of the roadway further contributed to the roof failure process the results also clearly showed that shear cracks were predominant in the roof and played a major role in the behavior of the roadway roof additionally support and excavation schemes that affect roof stability were observed

structural geometry and kinematic evolution of the eastern cascades foldbelt washington and british columbia the eastern cascades foldbelt is one of three structural domains lying within the complex collision zone between the insular and intermontane composite terranes in northern washington and southern british columbia the foldbelt resides between the high grade metamorphic backbone of the cascade orogen on the west and rocks of the composite intermontane terrane to the east it encompasses the stratigraphically coherent basalt floored jura cretaceous methow basin as well as more chaotically disposed permian jurassic oceanic rocks of the hozameen terrane methow basin rocks are thought to have been sutured above the oceanic rocks prior to the middle cretaceous contractional episode described in this report based on the analysis presented herein between ca 100 and 88 ma the rocks in the foldbelt underwent shortening in an east northeast west southwest direction by 50 km or more largely by displacement on the east vergent jack mountain chuwanten thrust system the early stages of contraction occurred by

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

collapse mechanism of the overlying strata above a salt cavern by solution mining with double well convection in solution mining of salt formations unreasonable salt cavities formed may lead to surface collapse hazards in this paper a mathematical model was proposed to analyze the collapse mechanism of the overlying strata above a salt cavern induced by solution mining with double well convection in the proposed model the collapses of the overlying strata were supposed to occur layer by layer and a thin plate with four edges clamped was introduced to calculate the critical collapse span of each layer the limit breaking distance of the thin plate can be solved by setting the corresponding surrounding condition according to the solution the limit breaking distance is related to the dimensions the mechanical properties of the rock the buried depth and the force status for the convenience of calculation a span criterion was introduced to distinguish the limit breaking distance to keep the immediate roof more stable the span criterion should be larger as a case study the collapse incidents at dongxing salt mine were analyzed by the proposed model and the collapses were verified to be inevitable under its mining and geological conditions discussions were finally carried out to study the influences of the thickness of the immediate roof tension strength poisson ratio and buried depth on the collapses above all the collapses will occur more easily with the decrease of the thickness tension strength and poisson ratio of each stratum especially the collapse depth will not increase linearly with the buried depth because of the bulking effect of the overlying strata

viscoelastic damage modeling of sinkhole formation abstract the sinkholes along the dead sea coast are observed in two main sedimentary environments alluvial fan sinkholes which usually form abruptly as deep 20 m and narrow 3 m sinkholes and mud flat sinkholes which usually form as shallow a few centimeters and wide 5 m sinkholes and deepen later the mechanical collapse of all sinkholes is triggered by cavities created by the dissolution of an underlying salt layer by relatively fresh groundwater the processes attributed to the mechanical formation of the sinkholes are viscous flow and brittle fracture failure we use a two dimensional viscoelastic damage rheology numerical model to quantitatively explain the brittle and ductile aspects of collapsed sinkholes three cases of the rheology of the collapsed sediments are simulated 1 damage controlled failure 2 viscoelastic controlled failure and 3 an intermediate damage viscoelastic case results show that viscoelasticity cannot be the sole process acting on the deformed layer because all sinkholes are characterized by sharp boundaries the damage accumulation progresses until arched cavities are created in the soil layer because of the geometric heterogeneity of the layer represented by the heterogeneity of the mesh smaller blocks continue to fall after the first breakup into the cavity advancing the arched cavity upwards this propagation finally stops when the cavity is shallow enough to hold the irregular arch the combination of these two processes creates competition within the stress reduction mechanism that may lead to either magnified or reduced deformation the deformation is magnified in high shear stress locations where the dispersion of the viscous flow spreads damage failure and it is reduced in low shear stress locations where viscous flow disperses shear stress before the onset of damage

fuzzy models for analysis of rock mass displacements due to underground mining in mountainous areas the displacement and deformations of rock mass due to underground mining has often resulted in major disasters throughout the world frequently inflicting heavy losses of life and damage to property and these disasters have motivated the development of rock mass mechanics the prediction of displacement of rock mass and their surface effects is an important problem of the rock mass mechanics in the excavation activities especially the coal and metal mining in mountainous areas based on results of the statistical analysis of a large amount of measured data in mining engineering the fundamental fuzzy model of displacements and deformations of rock mass is established by using the theory of fuzzy probability measures the theories of both two and three dimensional problems are developed and applied to the analysis of engineering problems in excavation and underground mining in mountainous areas the agreement of the theoretical results with the field measurements shows that our model is satisfactory and the formulae obtained are valid and thus can be effectively used for predicting the displacements and deformations and the safety evaluation of the buildings on the ground

observing the yield curve of compacted pack ice 1 a method for observing the yield curve of compacted pack ice is developed based on the characteristic analysis of the stress field within the pack ice the analysis shows that the slope of the yield curve is associated with the angle between intersecting linear kinematic features thus by measuring the intersection angles we can inversely estimate the yield curve applying this method to the observed angles generates a curved diamond yield curve which possesses almost all the advantages identified by the other methods however due to the limited data available more observations are favored to refine this yield curve

is air pollution causing landslides in china abstract air pollution in china often exceeds unhealthy levels but chinese air is not only a threat from being breathed the pollutants may also be causing fatal landslides very acid rain from severe air pollution falls widely in southwest china where coal is a major energy source we discuss where acid rain may provide an unsuspected link between mining and the fatal 2009 jiweishan landslide in southwest china it may have reduced the strength of a thin calcareous black sapropelic shale in jiweishan mountain by removing cementing carbonate minerals and sapropel matrix mining beneath the potential slide mass may not have directly triggered the landslide but collapse of abandoned adits drained a perched aquifer above a regional black shale aquiclude inflow of acid oxygenated water and nutrients into the aquiclude may have accelerated the reduction of strength of the weakest rocks and consequently led to rapid sliding of a large rock mass on a layer of weathered shale left composed largely of soft and slippery talc

investigation of fracture behaviour during rock mass failure the main characteristic behaviour of rock mass fractures are studied their importance in the application and investigation of rock mass failure is demonstrated through some preliminary investigation of rock mass fracture mechanics by the authors firstly in the study of rock fracture features the mechanisms and non linear phenomenon of a fragmented belt of rock fracturing have been investigated several new ideas can be used to construct a new system of rockmass fracture mechanics secondly in the investigation of rock mass structure controlled rock mass fracturing the importance of true mixed mode fracturing is emphasized a primary criterion to predict the propagation of rock mass cracks has been established thirdly in the investigation of non singular stress effects on rock mass fracture a new fracture criterion for the generalized crack opening displacement of rock is proposed this can be used to analyze the influence of the normal stress and the crack orientation on the fracturing process in a rock mass finally the rock mass fracture mechanics investigation and methodology was used to analyze the stability of the mabukan high slope in the upper reaches of a large hydro power station in the south west of china it is shown that the results of this study have created a more solid foundation for the application of rock mass fracture mechanics to rock engineering

the 2009 jiweishan rock avalanche wulong china precursor conditions and factors leading to failure abstract this study investigates the predisposing geological and anthropogenic factors and indicative precursors preceding the fatal 5 june 2009 jiweishan rock avalanche it began as a rockslide and transformed into a rock avalanche that killed 74 people and caused major property loss due to misdiagnosis of the failure mode and underestimation of volume and travel distance besides topography structure and stratigraphy that favoured failure mining below the failed rock mass had changed the state of stress and altered groundwater flow the anthropogenic factors caused deformation and accelerated failure of the slope and therefore were important contributions cracks and a karstic zone had developed along regional joints and defined several boundaries of the failed rock mass furthermore a 2 m wide crack developed since 1958 revealed a potential basal failure surface at the contact between karstic limestone and an underlying pre sheared thin shale aquiclude increasing magnitude and frequency of rockfalls and tension cracks at the front end of the sliding block appeared three days before the event and implied the likely movement direction of the sliding rock mass these could have warned of a developing giant failure topography included a large elevation difference between the toe of the failure surface and the cliff base a narrow valley to channel debris and the steep gradient of the downstream tiekuang creek could have suggested that failure might lead to a rapid and long runout rock avalanche however access to the densely vegetated source area before the failure was difficult and local investigators did not have all of the evidence that might have led them to recognize that potential danger was more than continuing rockfalls

ground subsidence and its socio economic implications on the population a case study of the nakuru area in central rift valley kenya several areas of nakuru town and its environs often undergo subsidence along the parallel fault zones during and after heavy rainfall during the rainy season when most of the subsidence occurs the overlying unconsolidated volcanoclastic sediments become oversaturated with water the water reduces the shear strength of the sediments and also introduces extra loading through saturation leading to subterranean erosion along faults the unconsolidated sediments then collapse into the subsurface water channels which closely follow the fault zones leading to formation of sinkholes the frequent incidences of ground subsidence in the study area have caused several fatalities destroyed settlements and physical infrastructure furthermore persistent subsidence has increased the cost of construction and the repair of the destroyed properties apart from being hazardous ground subsidence degrades environment when sewage water refuse and garbage enter into the groundwater systems through the sinkholes the fissures formed after subsidence also stand prominently as ugly features from the rest of the terrain mitigation measures including control channelizing of drainage proper engineering practices and appropriate land use are suggested in this paper

compression of floating ice fields the compression of ice fields made up of thin floes is central to the processes of ice jam formation in northern rivers pressure ridge formation in northern seas and the dynamics of ice fields in arctic and antarctic marginal seas this work describes the results of computer simulations in which a floating layer of circular floes confined in a rectangular channel is compressed by a pusher plate moving at a constant speed the accuracy of the simulations is assessed by comparison with a series of similar physical experiments performed in a refrigerated basin following this comparison the computer model is used to perform an extensive series of simulations to explore the effect of variations in channel length and width the ratio of floe diameter to thickness floe on floe friction coefficients and the distribution of floe diameters on the force required to compress the floes the results show that reducing the aspect ratio of the floes or increasing the friction coefficient increases the force needed to compress the floes both changes increase the force by changing the dominant failure mechanism in the layer of floes from rafting to underturning increasing channel width reduced the compressive force per unit channel width by reducing the relative importance of frictional drag at the channel edges last the results of a simulation using a distribution of floe diameters was indistinguishable from those of a simulation using floes with a single diameter equal to the average diameter of the distribution

marginal ice zone rheology comparison of results from continuum plastic models and discrete particle simulations computer simulations of ice behaviour in the marginal ice zone miz are described two cases were studied a constant velocity wind blowing at certain angle with respect to the coast in what can be considered a simplified miz problem and a vortex wind force field the viscous plastic approach of hibler has been used to model the ice rheology we study the effects of adopting two different rheologies cavitating fluid and mohr coulomb the introduction of shear strength effects through a mohr coulomb yield criterion plays an important role in determining ice drift velocities in the miz the effects that ice floe collisions can have in determining the ice rheological behavior have been tested by using discrete particle simulations in order to do so simulations for the miz were performed using different mean floe sizes as well as different miz widths and wind conditions the predictions of the discrete particle simulations are in general agreement with the results obtained by using the mohr coulomb rheology in the viscous plastic model the continuum models were solved by using a fully lagrangian method known as smoothed particle hydrodynamics sph the method has the advantage of the lagrangian techniques in avoiding problems of numerical diffusion an additional advantage of sph in comparison with classical lagrangian approaches is that sph does not need grids and this makes it well suited to handle problems of large deformations

a three dimensional back analysis of the collapse of an underground cavity in soft rocks abstract the assessment of stability of man made underground caves excavated in the past and later on abandoned represents a serious challenge for land and urban planning operations especially for the areas of possible interaction of the caves with overlying structures and infrastructures several areas of southern italy are characterized by the presence of abandoned underground quarries for the extraction of soft calcarenite rocks which now threatens the overlying environment due to the risk of collapse and the consequent generation of sinkholes this work presents a back analysis of a sinkhole occurred in 2011 in the town of marsala caused by the collapse of an underground quarry as a representative case study of these phenomena based on the available geometrical and geological dataset as well as the field observations of the phenomenon in this article the assumptions and the results about the genesis of the 2011 sinkhole as derived from a three dimensional finite element back analysis aimed at reconstructing the stress strain evolution that brought to the ground failure collapse is discussed in particular the 3 d numerical analyses have been performed in order to identify the factors responsible of the genetic mechanism of the sinkhole the finite element analysis has been carried out by accounting for the geotechnical characterization of the marsala calcarenites derived from both specific laboratory tests performed on samples taken from the site and literature data available on the same rock material the numerical results have been then validated by means of the comparison with field observations and also compared with those achieved through a 2 d model of the same case study

the assessment of rockfall hazard at the base of talus slopes fragmental rockfall is characterized by the independent movement of individual rock fragments after detachment from a rock face the continued operation of the process leads to the accumulation of talus slopes on talus slopes the rockfall shadow extends beyond the base of the talus and consists of scattered boulders that have run out beyond the base of the slope the landing probability of boulders in the shadow is examined return periods of the order of 1000 years relative to a house site are typical rockfall behaviour particularly with respect to run out into the shadow can be assessed using geological evidence empirical methods physical modelling and computer based analytical models an empirical minimum shadow angle of 27 5 i e the angle between the distal limit of the shadow and the top of the talus slope is suggested and would be useful in rockfall vulnerability studies at the base of talus slopes as a first approximation to shadow limits it is preferable to the use of the rockfall fahrb

effect of quarrying on the slope stability in banasuramala an offshoot valley of western ghats kerala india the narippara area which is nestled in the banasuramala of wayanad district witnessed initiation of landslide which was manifested in the form of curvilinear cracks running for a length of 170 m in the event of continuous rainfall these cracks may get reactivated leading to a major landslide this could affect the life and livelihood of a large number of families living downslope and could cause extensive damage to property extensive mining for building stones in this area has been a cause for much concern amongst the local population this study aims at understanding the impact of quarrying on slope stability through geotechnical geophysical and environmental impact assessment eia geotechnical analysis shows that the area is stable under dry condition but parts of the area are critical under wet and saturated conditions moreover resistivity studies revealed that the cracks that had developed extend up to the bedrock and the suspected mechanism of failure will be translational in nature eia reveal that due to quarrying and mining operations the possibility of land disturbances cannot be ruled out during the monsoon season in the present study an attempt is also made to suggest management strategies for mitigating further effects of landslides in this area

late cretaceous and early tertiary plutonism and deformation in the skagit gneiss complex north cascade range washington and british columbia the skagit gneiss complex forms a more or less continuous terrane within the northern more deeply eroded part of the north cascade range the complex comprises abundant plutons intruded at mid crustal depths into a variety of metamorphosed supracrustal rocks of both oceanic and volcanic arc origin a plethora of syntectonic pegmatite small plutons and granitic dikes gives the complex a migmatitic aspect u pb zircon ages from gneissic plutons within and near the skagit gneiss complex indicate magmatic crystallization between 75 and 60 ma deformation recrystallization and migmatization in part postdate intrusion of the 75 60 ma plutons this latest cretaceous and earliest tertiary plutonism and migmatization may reflect thermal relaxation following early late cretaceous orogeny documented else where in the north cascades the complex was ductilely extended northwest southeast shortly after intrusion of granite dikes at 45 ma but before emplacement of the earliest 34 ma plutons of the cascade arc outcrops of late cretaceous and earliest tertiary plutons migmatites of the skagit gneiss complex and rocks with young ductile deformation are roughly coextensive all apparently marking a region of greater middle eocene unroofing unroofing was apparently contemporaneous with east west extension in the okanogan region to the east and north south and northwest southeast strike slip faulting within the north cascades

ridging and strength in modeling the thickness distribution of arctic sea ice a theory describing evolution of the ice thickness distribution the probability density of ice thickness was proposed by thomdike et al 1975 and has been used in several sea ice models the advantage of this theory over the widely used two level formulation is that it treats ridging explicitly as a redistribution of ice thickness and ice strength as a function of energy losses incurred by ridge formation however the parameterization of these processes remains rather speculative and largely untested and so our purpose here is to explore these parameterizations using a numerical model based on this theory the model uses a 160 km resolution grid of the arctic and 7 years of observed atmospheric forcing data 1979 1985 monthly oceanic heat flux and current fields are obtained from a 40 km resolution coupled ice ocean model run separately with the same forcing by requiring the computed monthly mean ice drift to have the same magnitude as observed buoy drift we estimate the primary strength parameter the ratio of total to potential energy change during ridging this ratio depends on the value of other parameters however the standard case has a ratio of 17 which is within the range estimated by hopkins 1994 in simulations of individual ridging events the effects of ridge redistribution and shear ridging parameters are illustrated by a series of sensitivity studies and comparisons between observed and modeled ice thickness distributions and ridge statistics in addition these comparisons highlight the following shortcomings of the thickness distribution theory as it is presently implemented first the process of first year to multiyear ridge consolidation is ignored and second the observed preferential melt of thick ridged ice is not reproduced

a review of discrete element simulation of ice structure interaction sea ice loads on marine structures are caused by the failure process of ice against the structure the failure process is affected by both the structure and the ice thus is called icestructure int

reconciliation of two sided thrusting burial metamorphism and diachronous uplift in the cascades of washington and british columbia several recently published data sets have shed new light on many of the fundamental kinematic aspects of mid cretaceous orogeny in the cascades of northwestern washington and southwestern british columbia specifically a it is now clear that contractional deformation associated with this orogeny affected rocks east of the crystalline core of the range to a greater degree than had previously been suspected and b geobarometric data from the crystalline core of the range now permit a quantitative reconstruction of the crustal thickening event responsible for core metamorphism to be attempted i propose a new kinematic model for mid cretaceous orogeny that reconciles these data with previously collected data sets that focused on deformation in the northwest cascades san juan islands thrust system the model derived from this analysis suggests that the cascades underwent a minimum of between 400 and 500 km of east west shortening between about 115 and 85 ma owing to the collision of the greater insular terrane which probably included rocks of the chilliwack nooksack terrane with the western edge of the greater intermontane terrane which included the methow basin and bridge river hozameen terrane on the basis of their relative and absolute times of uplift i assign the deepest part of the metamorphic core the skagit gneiss to the greater insular terrane and the structurally higher carapace of the core the settler nason metapelites and the cogburn creek mad river metabasalt metachert to the westernmost intermontane terrane the contact between the skagit gneiss and the overlying assemblages must represent a fault or suture across which at least 120 km of displacement took place this fault is also the root zone from which many of the nappes in the northwestern cascades and san juan islands were derived i concur with previous workers who suggested that the collisional event was not precipitated by the closure of a several thousand kilometer wide ocean but was rather due to a short lived margin normal convergence event that both followed and was followed by periods during which the continental margin was highly influenced by oblique subduction and strike slip faulting

geotechnical precursors to large scale ground collapse in mines abstract analysis of instances of large scale ground collapse in underground and open pit mines shows that geotechnical precursors to rock mass failure appear over time recorded geotechnical precursors in cases of ground collapse larger than 100 000 tonnes were examined results indicated that a sequence leading to rock mass collapse existed ground movement was observed at the periphery of each impending collapse over extended periods in some case years months before collapse the main precursor is deterioration of ground conditions in hard rock mass within weeks before collapse precursors in the form of high stress signs were noticed in close proximity to the centre of the eventual collapse area hours before the collapse the most common precursors were rock noises and large falls of ground close to the centre of the imminent collapse

on the applicability of geomechanical models for carbonate rock masses interested by karst processes rock mass classification and geomechanical models have a particular importance for carbonate rocks due to their peculiar fabric variability of the main features and scarce availability of experimental data carbonates are particularly sensitive to syn depositional and post depositional diagenesis including dissolution and karstification processes cementation recrystallisation dolomitisation and replacement by other minerals at the same time as most of sedimentary rocks they are typically stratified laminated folded faulted and fractured the strength and deformability of carbonate rock masses are therefore significantly affected by the discontinuities as well as by their pattern and orientation with respect to the in situ stresses further discontinuities generally cause a distribution of stresses in the rock mass remarkably different from those determined by the classical elastic or elasto plastic theories for homogeneous continua goal of this work is the description of the difficulties in elaborating geomechanical models to depict the stress strain behavior of karstified carbonate rock masses due to such difficulties a high degree of uncertainty is also present in the selection of the most proper approach the discontinuum one or the equivalent continuum and in the numerical model to be used within a specific engineering application as well the high uncertainty might cause wrong assessments as concerns the geological hazards the design costs and the most proper remediation works even though recent developments in the application of numerical modeling methods allow to simulate quite well several types of jointed rock masses as concerns carbonate rock masses many problems in representing their complex geometry in the simulation models still remain due to peculiarity of the structural elements and the presence of karst features in the common practice the improper use of the geomechanical models comes from a superficial geological study or from the lack of reliable geological and structural data that as a consequence bring to erroneous evaluations of the influence of the geological structural features on the in situ stress state and the stress strain rock mass behavior

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

karst geosites at risk of collapse the sinkholes at nociglia apulia se italy this paper focuses on the impacts of contemporary geomorphological processes on fruition activities in a karst area of salento apulia southeastern italy the work illustrates the results of studies in a sinkhole field at nociglia in the lecce province recently recognized as a geosite and where shallow phreatic speleogenesis operates close to the water table level with the formation of karst caves successive roof collapse formation of wide caverns and sinkhole development at the surface all these features threaten the nearby infrastructures including a province road salento has a great number of active sinkholes related to natural and anthropogenic cavities their presence is at the origin of several problems in the built up environment due to increasing population growth and development pressures in such a context the detection of cavities and the assessment of sinkhole hazards present numerous difficulties to assess the potential danger from sinkholes it is important to identify and monitor the main factors contributing to the formation process a multi disciplinary approach comprising geological geomorphological and geophysical analyses is necessary to obtain a comprehensive knowledge of these complex phenomena in karst areas geophysical methods can be of great help to monitor the processes and for identifying and mapping features related to the underground voids by detecting contrasts in physical properties such as density and electrical resistivity with the surrounding sediments at the same time recognition of the presence of sinkholes by geophysical methods has to adapt to the local geological conditions and take advantage of the integration of the several methodologies available the territory of nociglia demonstrates that monitoring is essential for the safe exploitation of these type of geomorphosites

a preliminary analysis of failure mechanisms in karst and man made underground caves in southern italy abstract natural and anthropogenic caves may represent a potential hazard for the built environment due to the occurrence of instability within caves that may propagate upward and eventually reach the ground surface inducing the occurrence of sinkholes in particular when caves are at shallow depth the effects at the ground surface may be extremely severe apulia region southern italy hosts many sites where hazard associated with sinkholes is very serious due to presence of both natural karst caves and anthropogenic cavities the latter being mostly represented by underground quarries the pliocene pleistocene calcarenite a typical soft rock was extensively quarried underground by digging long and complex networks of tunnels with time these underground activities have progressively been abandoned and their memory lost so that many apulian towns are nowadays located just above the caves due to urban expansion in the last decades therefore a remarkable risk exists for society which should not be left uninvestigated the present contribution deals with the analysis of the most representative failure mechanisms observed in the field for such underground instability processes and the factors that seem to influence the processes as for example those causing weathering of the rock and the consequent degradation of its physical and mechanical properties aimed at exploring the progression of instability of the cavities numerical analyses have been developed by using both the finite element method for geological settings represented by continuous soft rock mass and the distinct element method for jointed rock mass conditions both the effects of local instability processes occurring underground and the effects of the progressive enlargement of the caves on the overall stability of the rock mass have been investigated along with the consequent failure mechanisms in particular degradation processes of the rock mass as a consequence of wetting and weathering phenomena in the areas surrounding the caves have been simulated the results obtained from the numerical simulations have then been compared with what has been observed during field surveys and a satisfactory agreement between the numerical simulations and the instability processes as detected in situ has been noticed

a random field model for surface roughness and aperture of rock fractures present constitutive models for rock fracture behaviour require information concerning the fracture geometry on which the mechanical and hydraulic properties of the rock mass are greatly dependent in this paper measurements of rock fracture surfaces and aperture using a 3 d laser scanning technique are reported in order to check the validity of a fractal model for fracture geometry this formulation incorporates fractal descriptions of roughness angularity and aperture fractal patterns can be persistent if an increasing increment implies an increase in the next increment or anti persistent if increasing increments follows decreasing increments persistence and anti persistence are recognised as descriptors of the geometrical complexity of roughness and aperture the analysis of the data also shows that the fractal models apply until stationarity occurs for sufficiently large samples which behave as random variables these sample sizes are defined as stationarity thresholds of roughness and aperture moreover the study of the cross correlation between the asperity height and aperture provides the link between fracture roughness and aperture geometry a theoretical model of fracture aperture during shearing is developed and successfully compared with experimental and numerical studies reported in the literature

on the mesoscale interaction of lead ice and floes the plasticity of the arctic ice pack depends on its granular nature in particular on the size and distribution of areas of thin ice and open water surrounding multiyear ice floes the paper begins with construction of a mesoscale 10 100 km granular model of the central arctic ice pack the mesoscale model is based on a dynamic particle simulation in which individual multiyear ice floes and surrounding parcels of first year ice are explicitly modeled as discrete convex polygons in a two dimensional domain deformation of the domain produces areas of localized failure and areas of open water the areas of localized failure are modeled as pressure ridging events using the results of numerical experiments performed with a computer simulation of the ridging process the paper focuses on the results of numerical experiments performed with the mesoscale model in the experiments the model ice pack is biaxially deformed at constant strain rates the principal strain rates are varied to create deformation states ranging from pure shear to uniform compression the results define the shape and magnitude of the plastic yield surface the strain rate vectors associated with points on the yield surface the partition of energy dissipation between ridging and in plane sliding and the changes in the ice thickness distribution associated with various deformation states

the role of floe collisions in sea ice rheology a collisional rheology for an idealized two dimensional flow of a fragmented ice field is derived this fragmented ice field is modeled as an assembly of identical smooth disks collisions between neighboring disks are caused by the mean deformation field these collisions transfer momentum which produces the internal stresses in the deforming ice field by equating the collisional energy losses to the deformational energy a relationship between the stress and strain rate is quantified to demonstrate the essential idea an analytical derivation is first given under quite restricted assumptions a monte carlo simulation is then developed to provide a more general approach for the analysis it is found that the collisional stresses are proportional to the square of disk diameter and the square of the deformation rate the magnitude of stresses is also found to increase rapidly as the collisional restitution of disks increases the collisional rheology yields zero tensile strength the associated normal flow rule commonly used in the plastic rheology is not valid in the collisional rheology it is found that the collisional stresses are very small consequently the resulting stress divergence is estimated to be much lower than the air stress typically encountered in the marginal ice zone however these collisional stresses become singular as the maximum compactness is reached indicating that a different mechanism may exist in that extreme

roads over lava tubes in cheju island south korea there are 59 known lava tubes in the basalts of cheju island south korea they have formed by either crusting or injection and the structural properties of the rock over them vary with their formative processes two tubes are crossed by roads that stand on very thin rock arches one road has been built on a bridging concrete slab the other is unprotected but both appear to be stable a ratio of 3 1 for tube width to roof thickness appears to ensure integrity under normal engineering loads

insar based modeling and analysis of sinkholes along the dead sea coastline sinkholes commonly form by subsurface dissolution cavities that collapse after the overlying layers become mechanically unsupported sinkholes along the dead sea shorelines are preceded by associated with and followed by gradual surface subsidence that accompanies the cavities growth we exploit satellite radar interferometry interferometric synthetic aperture radar to resolve temporal and spatial relationships between gradual subsidence and sinkhole collapse the geometry of the deflating cavity roof is determined by elastic inverse modeling of the surface displacements a coulomb failure stress criterion is applied to calculate the stress field induced by the deflating cavity at the ground surface we find that the induced stress field favors generation of sinkholes at the perimeters of the subsiding areas rather than at their centers in agreement with field observations providing important information for sinkhole hazard assessment further our analysis suggests that short term deformation in consolidated gravel layers at shallow depths could be approximated by simple elastic modeling

three dimensional characterization of complex mantled karst structures decision making and engineering solutions applied to a road overlying evaporite rocks in the ebro basin spain abstract at mantle cover evaporite karst settings evidences of surficial subsidence are usually strongly dependent on geomechanical properties and spatial inhomogeneities within the cover series in infrastructure assets affected by karst processes the evaluation of mitigation or engineering solutions requires a 3d reconstruction of the underground karst affected materials analysis and surveillance are also required to avoid deterioration of natural conditions and the migration or the increase in rate of karst features in the central ebro basin fluvial deposits cover soluble salts mainly gypsum located below the regional water table variations of geomechanical parameters of the cover mainly related to carbonate crusts and the contemporaneous sedimentation of fluvial deposits during karst activity can complicate the characterization of affected volumes in this work an integrated analysis including the available information 3d characterization by means of gpr and three boreholes in a peri urban road was carried out to finally define the geometry and evolution of karst phenomena an evaluation of metastable situations is also considered in order to define the zoning for hazard mitigation this evaluation shows that the volumetric affection to the cover series is in the range of tens of thousands of cubic meters a proposed list of factors related to social aspects infrastructure relevance and budget is analyzed

structure and chronology of the oval peak batholith and adjacent rocks implications for the ross lake fault zone north cascades washington the 200 km long ross lake fault zone rlfz forms the northeastern border of the crystalline core of the north cascades this late cretaceous and paleogene structure is an 15 km wide system of faults and fault zones several of which deform the paleocene 65 ma u pb zircon oval peak batholith the southern segment of the gabriel peak tectonic belt of the rlfz is defined by strongly deformed rocks of the foliated southwestern margin of the oval peak batholith structurally underlying pre late cretaceous twisp valley schist and structurally highest part of the subjacent skagit gneiss which here consists of late cretaceous 87 ma and paleocene 60 ma orthogneiss kinematic indicators in moderately steeply northeast dipping mylonitic orthogneiss record reverse slip the strong solid state flattening fabric in the foliated margin of the oval peak batholith formed during or shortly after emplacement and overprinted a magmatic fabric observed in the core of the batholith foliation and associated stretching lineation within the gabriel peak tectonic belt are oblique to the regional structural grain but concordant with the contacts of the batholith these patterns in part record emplacement of the batholith as an expanding diapir into the tectonic belt reverse slip in the tectonic belt occurred before during and shortly after emplacement but ended by 55 58 ma the core of the oval peak batholith intruded a large tongue of twisp valley schist on the north porphyroblast microstructures and ar ar and k ar geochronology indicate that amphibolite facies dynamothermal metamorphism of the schist occurred during intrusion the foggy dew and twisp river fault zones separate the batholith and its wall rocks on the northeast from weakly metamorphosed strata of the methow basin the foggy dew fault zone contains mylonitic gneiss derived from the oval peak batholith skagit gneiss and tonalitic rock that displays u pb zircon systematics suggestive of an eocene age sillimanite schist and amphibolite are also present mylonites record dextral strike slip with a component of normal slip down to the northeast movement in the fault zone continued subsequent to deformation in the gabriel peak tectonic belt and ended by 48 ma mylonites in the twisp river fault zone also reveal dextral strike slip but apparently with less normal slip the rlfz experienced a diachronous history from at least 65 to 45 ma this history was dominated by dextral strike slip but there were significant components of normal slip and reverse slip on some structures during the latter part of this interval 57 45 ma the rlfz probably recorded a transtensional tectonic regime transitional between extension to the east in omineca metamorphic core complexes and dextral strike slip to the west related to oblique convergence along the continental margin early cenozoic plutonism metamorphism and ductile deformation have strongly overprinted any of the major cretaceous deformation postulated in previous tectonic models for the rlfz

cretaceous crustal section through the proposed insular intermontane suture north cascades washington the north cascades of washington consist of rocks that were deformed and recrystallized during a middle cretaceous orogeny that was driven by the collision of the insular and intermontane superterranes we reconstruct a composite vertical crustal section through the orogen on the basis of geobarometric data from the skagit gneiss and on stratigraphic and structural data from supracrustal rocks exposed east of the skagit gneiss we propose that at the end of the orogeny the upper 30 km of crust consisted of skagit gneiss overlain by two structural couplets each composed of methow basin strata underlain by hozameen terrane rocks we suggest that the insular intermontane suture lies between the skagit gneiss and the overlying hozameen terrane rocks

effects of mineral suspension and dissolution on strength and compressibility of soft carbonate rocks abstract calcarenites are highly porous soft rocks formed of mainly carbonate grains bonded together by calcite bridges the above characteristics make them prone to water induced weathering frequently featuring large caverns and inland natural underground cavities this study is aimed to determine the main physical processes at the base of the short and long term weakening experienced by these rocks when interacting with water we present the results of microscale experimental investigations performed on calcarenites from four different sites in southern italy sem thin sections x ray ct observations and related analyses are used for both the interpretation definition of the structure changes and the identification quantification of the degradation mechanisms two distinct types of bonding have been identified within the rock temporary bonding tb and persistent bonding pb the diverse mechanisms linked to these two types of bonding explain both the observed fast decrease in rock strength when water fills the pores short term effect of water identified with a short term debonding std and a long term weakening of the material when the latter is persistently kept in water saturated conditions long term effect of water identified with a long term debonding ltd to highlight the micro hydro chemo mechanical processes of formation and annihilation of the tb bonds and their role in the evolution of the mechanical strength of the material mechanical tests on samples prepared by drying partially saturated calcarenite powder or a mix of glass ballotini and calcarenite powder were conducted the long term debonding processes have also been investigated using acid solutions in order to accelerate the reaction rates this paper attempts to identify and quantify differences between the two types of bonds and the relative micro scale debonding processes leading to the macro scale material weakening mechanisms

rock mass behaviour prior to failure abstract changes in stress around mining excavations can result in changes in the behaviour of the rock mass which in turn may lead to damage failure and consequent collapse of the rock mass analysis of documented case studies of regional scale collapses indicates that each rock mass failure is preceded by a precursory manifestation of rock mass behaviour structural damage and progressive failure are manifested by the presence of geotechnical warning signs indicators and precursors and can be exacerbated by triggers indicators suggest that the rock mass may be prone to damage whereas geotechnical precursors demonstrate that the rock mass has been disturbed possibly preceding failure geotechnical analysis of large scale rock mass behaviour also indicates that the failures do not happen at random and are not unpredictable in terms of the type of failure and its location indicators and precursors have to be interpreted in conjunction with mine design mining activities and potential triggers geotechnical monitoring of the precursory behaviour of the rock mass provides timely warning and allows for implementation of remedial measures in this paper these issues are discussed and illustrated in the context of geotechnical risk management

influence of petrographic parameters on geotechnical properties of tertiary sandstones from taiwan while tunneling through tertiary sandstones in taiwan tunnel squeezing occurred in some of the sandstones e g mucha tunnel and chungho tunnel in northern taiwan but not in all of them this phenomenon indicates that the geotechnical properties of tertiary sandstones differ from one sandstone to another and further characterization is of interest laboratory experiments were conducted to explore the geotechnical characteristics including strength deformational behavior and wetting softening phenomena of more than 13 tertiary sandstones from northern taiwan it was found that these sandstones differ from hard rocks in having significant shear dilation and wetting softening behavior which is defined as the reduction of both strength and stiffness of dry sandstone due to wetting such distinct behavior can occur even when the sandstones have medium to moderate strength based on the degree of wetting softening behavior as well as the deformational behavior two types of sandstones types a and b were identified relative to type a sandstone the type b sandstone is characterized by more deformation shear dilation and more significant wetting softening in addition how the microscopic parameters or petrographic parameters affect the macroscopic mechanical behavior including the deformational behavior uniaxial compressive strength ucs and strength reduction r due to wetting was studied by petrographic analysis among the petrographic and physical parameters evaluated the grain area ratio gar and porosity are found to be the key parameters as a result empirical relations of ucs and strength reduction r due to wetting expressed in terms of porosity and grain area ratio respectively are proposed comparisons were made to sandstones worldwide from published data and it is found that these two empirical relations are also applicable to other sandstones finally a classification method based on ucs and r on the one hand and the petrographic parameters grain area ratio and porosity on the other is proposed for tertiary sandstones to indicate the geotechnical characteristics of sandstones this proposed classification method can also be expressed in terms of grain matrix porosity content of sandstones it is also found that porosity has more influence on the ucs than grain and matrix content does d 2004 elsevier b v all rights reserved

mid cretaceous thrusting in the southern coast belt british columbia and washington after strike slip fault reconstruction a major thrust system of mid cretaceous age is present along much of the coast belt of northwestern north america thrusting was concurrent and spatially coincided with emplacement of a great volume of arc intrusives and minor local strike slip faulting in the southern coast belt 52 to 47 n thrusting was followed by major dextral slip faulting which resulted in significant translational shuffling of the thrust system in this paper we restore the displacements on major dextral slip faults of the southern coast belt and then analyze the mid cretaceous thrust system two reconstructions were made that use dextral faulting on the yalakom fault 115 km castle pass and ross lake faults 10 km and fraser fault 100 km the reconstructions differ in the amount of dextral offset on the straight creek fault 160 and 100 km and how much the ne part of the cascades crystalline core expanded 30 km and 0 km during eocene extension reconstruction a produces the best match of lithotectonic units and thrust systems our synthesis shows that the southern coast belt thrust system was 250 180 km wide after thrusting the thrust system was mainly southwest vergent but had a belt of northeast vergent back thrusts on the northeast side associated with the tyaughton methow basin which may indicate large scale tectonic wedging thrust faults are commonly low to moderate angle but high angle faults also occur especially as late stage out of sequence structures involving plutons the amount of thrust displacement across the system is unknown but must be at least 100 km and may be many hundreds of kilometers most thrusting occurred from 100 to 80 ma and did not migrate systematically until after 90 ma when thrusting and magmatism shifted to the northeast for a few million years widespread thrusting occurred both near plutons and where there are no or small plutons which strongly suggests that thrust faulting was caused by regional to plate scale forces such as rapid plate convergence and or arc continent collision

geotechnical properties of weak sandstones weak sandstones are here defined as having a saturated uniaxial compression strength of 0 5 20 mpa the mineralogy texture density porosity and saturated moisture content of these materials have

intra arc crustal loading and its tectonic implications north cascades crystalline core washington and british columbia widespread high pressure cretaceous metamorphism in the coast plutonic complex of southeast alaska and british columbia and its southeast extension the cascades crystalline core is commonly attributed to thrust loading during superterrane collision however terrane boundaries within the cascades core are intruded by relatively shallow mid cretaceous plutons and crustal loading of 2 5 kbar postdates these plutons these observations are not consistent with proposed collisional models and we suggest that loading occurred by structural and or plutonic processes operating within a magmatic arc such loading may be an important process in arc tectonics although it has not been widely reported

engineering geology ground surface movement and fissures induced by underground mining in the jinchuan nickel mine the jinchuan nickel mine is the largest underground mine with cut and fill mining in china in 1999 there appeared evident ground surface movement and many ground fissures in jinchuan no 2 mine following an introduction to the engineering geology and mechanical properties of the rock mass in the jinchuan mine areas this paper reveals the features of the measured in situ stresses and puts emphasis on an analysis of the mechanism of surface movement and ground fissures induced by the underground mining with backfill it is indicated that both the fault structures and the alteration contact zones are well developed as the dominant engineering geological characteristics in the jinchuan mine areas the stress redistribution in surrounding rocks resulting from the mining the low stiffness of the filling body the existence of the void space and the influence of on going mining activities is the main reason for the occurrence of surface movement and ground fissures

physical properties and textural parameters of calcarenitic rocks qualitative and quantitative evaluations abstract petrophysical and mechanical properties of sedimentary rocks are influenced by size shape and packing of grains porosity cement and matrix content all controlled strongly by depositional fabric and postdepositional processes this paper presents a study on the textural characteristics of soft and porous calcarenites and the main methods to determine petrophysical data the examined calcarenites sampled from three quarry districts located in apulia southeastern italy are fine grained and coarse grained grainstones a and d and medium grained packstones b belonging to a plio pleistocenic formation calcarenite di gravina outcropping in the whole region the study involved particularly textural analysis on thin sections using optical petrographic microscopy and evaluation of total and effective porosity by means of standard geotechnical laboratory tests mercury intrusion porosimetry and image analysis grain size frequency distribution was also carried out by traditional sieve and sedimentation analysis on disaggregated materials and image analysis computer analysis of digital images was performed on photomicrographs applying the methods of quantitative stereology to pore size and grain size distributions a comparison between results showed that each technique used has its limitations linked to the textural characteristics primarily geometry and topology of the pore network granulometry grain shape and packing of calcarenites

carbonate karst and its relationship with geodynamic conditions of the odessa city ukraine a connection between karst and geodynamic features in the area of the city of odessa black sea karst region was considered the geodetic geological and hydrogeological researches showed divergent vertical and horizontal movements of the individual units of the neogene quaternary structural stage it was found that the main orientations of passages in the caves in the moldavansky and kryvobalkovsky sites are nnw sse wnw ese and nne ssw this agrees well with the direction of the diagonal lineament network disclosed in recent years the main directions of cave passages in the bugaevsky site coincide with the main directions of the lineaments wnw ese nnw sse located in the immediate vicinity of the zones of influence of the lineaments of the orthogonal networks n s ssw nne and w e these findings suggest that caves developed along the directions of the lineaments of two tectonic networks of neogene structural stage diagonal and orthogonal these networks of tectonic fractures were mapped and analyzed previously by applying the geological and hydrogeological methods and analyzing digital maps of the neogene surfaces results of the research were compared to a map of isolines of long term average velocity of vertical deformations of ground surface and of zones of influence of lineaments identified in the surface topography of upper miocene clay limestone and pliocene red brown clay they show that the karst areas are mainly located in the gradient zones of vertical deformation of ground surface and zones where upper miocene limestone is compartmentalized by diagonal and orthogonal lines of fracture these areas could be considered as tectonically weakened

comment on mid cretaceous thrusting in the southern coast belt british columbia and washington after strike slip fault reconstruction by paul j umhoefer and robert b miller

behavior of rock in slopes the behavioral modes to which a rock slope is susceptible are many and complex this article discusses a long but not exhaustive list of common failure styles highlighting observable characteristics that distinguish one from another slopes in both strong and weak rock masses are considered principles are stated to explain how and why different failure modes develop in different rocks the discussion is illustrated with examples of diverse failure modes in foliated metamorphic rocks developed in the walls of an eroded spillway runout

sinkholes subsidence and subrosion on the eastern shore of the dead sea as revealed by a close range photogrammetric survey abstract ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide the rapid development of such phenomena around the dead sea in the last four decades poses a major geological hazard to the local population agriculture and industry nonetheless many aspects of this hazard are still incompletely described and understood especially on the eastern dead sea shore in this work we present a first low altitude our analysis reveals a kilometer scale sinuous depression bound partly by flexure and partly by non tectonic faults the estimated minimum volume loss of this subsided zone is 1 83 106 m3 with an average subsidence rate of 0 21 m yr 1 over the last 25 years sinkholes in the surveyed area are localized mainly within this depression the sinkholes are commonly elliptically shaped mean eccentricity 1 31 and clustered nearest neighbor ratio 0 69 their morphologies and orientations depend on the type of sediment they form in in mud sinkholes have a low depth to diameter ratio 0 14 and a long axis azimuth of nne ne in alluvium sinkholes have a higher ratio 0 4 and are orientated nnw n from field work we identify actively evolving artesian springs and channelized sediment laden groundwater flows that appear locally in the main depression consequently subrosion i e subsurface mechanical erosion is identified as a key physical process in addition to dissolution behind the subsidence and sinkhole hazard furthermore satellite image analysis links the development of the sinuous depression and sinkhole formation at ghor al haditha to preferential groundwater flow paths along ancient and current wadi riverbeds