geometry and distribution of regional joint sets in a non homogeneous stress field case study in the ebro basin spain abstract three regional joint sets striking n s e w and wnw ese affect the tertiary rocks of the central ebro basin from analysis of their chronological relationships and spatial distribution it is concluded that they correspond to two different tectonic events the n s set oldest and the e w set younger are present in the southern and central sectors while the wnw ese joint set predominates in the northern one the n s joints propagated in response to joint normal and fluid loads under an intraplate stress field with shmax oriented near n s related to forces caused by the convergence of africa iberia and europe and rifting at the valencia trough during the sedimentary infilling of the basin these joints are only present in the southern part of the area the e w joint set in the southern central sector records the same fracturing event as the wnw ese set does in the northern one its orientation was modified by the presence of the older n s set in the south which perturbed the regional stress field the younger wnw ese and e w joint sets are interpreted as unloading joints these propagated as a consequence of flexural uplift and exhumation related to isostatic rebound at the pyrenees and the ebro foreland basin a numerical approach is used to explain the inhomogeneous distribution of the n s joint set in terms of their absence being controlled by the depth of the water table at the time of their formation

evaluation of possible gas microseepage mechanisms petroleum microseepage anomalies over petroleum accumulations are commonly explained by rapid vertical migration of colloidal gas bubbles through fracture networks this article is a theoretical anal ysis of this mechanism and of continuous gas phase flow in frac tures the gas bubble ascent mechanism is much slower than re ported microseepage velocities so it cannot account for observed microseepage in contrast continuous gas phase flow through frac tures can equal or exceed reported microseepage velocity while maintaining total flux low enough so that petroleum accumulations can exist for geological lengths of time fracture entry pressure for bubbles is more than twice that of a continuous gas phase so con tinuous gas phase migration also requires a lower pressure threshold before initiating seepage vertical microseepage is therefore best explained by the same mechanism interpreted for macroseepage although this article provides a theoretically justified mecha nism for microseepage it also shows why interpretation of surface microseepage signals is problematic fracture geometry controls seepage velocity and flux so geochemical anomalies may indicate an increase in fracture aperture as well as possible subsurface ac cumulations larger fractures require very low gas capillary entry pressures so in some settings surface seepage could result from fractures over stratal migration pathways as well as over petroleum accumulations

displacement based seismic design of a shallow strip footing positioned near the edge of a rock slope abstract this paper presents a displacement based dynamic design of shallow strip footings located close to the edge of homogeneous and isotropic rock slopes the analysis is conducted using the generalized tangential technique in which the hoek brown strength is replaced by an optimal tangential mohr coulomb domain within the framework of the kinematic approach of limit analysis theory in order to better understand the influence of these factors including geometrical features rock strength parameters and seismic loading a parametric study is carried out an expression is derived and used to obtain a least upper bound solution for the bearing capacity of a footing on a rock slope considering a kinematically admissible log spiral failure mechanism in addition a similar expression of the horizontal yield seismic coefficient is derived for a given load acting on the foundation the assessment of earthquake induced permanent displacement is performed by a simplified procedure this requires the knowledge of a ground motion parameter that can be evaluated by site specific seismic hazard analyses or ground motion prediction equations and that considers the actual sliding surface the calculated displacement should not be greater than a selected limiting tolerable displacement for the specific case an example is presented illustrating the application of the design procedure for the bridge foundations

joint development normal to regional compression during flexural flow folding the lilstock buttress anticline somerset england alpine inversion in the bristol channel basin includes reverse reactivated normal faults with hanging wall buttress anticlines at lilstock beach joint sets in lower jurassic limestone beds cluster about the trend of the hinge of the lilstock buttress anticline in horizontal and gently north dipping beds j3 joints 295 2858 strike are rare while other joint sets indicate an anticlockwise sequence of development in the steeper south dipping beds j3 joints are the most frequent in the vicinity of the reverse reactivated normal fault responsible for the anticline the j3 joints strike parallel to the fold hinge and their poles tilt to the south when bedding is restored to horizontal this southward tilt aims at the direction of s1 for alpine inversion finite element analysis is used to explain the southward tilt of j3 joints that propagate under a local s3 in the direction of s1 for alpine inversion tilted principal stresses are characteristic of limestone shale sequences that are sheared during parallel flexural flow folding shear tractions on the dipping beds generate a tensile stress in the stiffer limestone beds even when remote principal stresses are compressive this situation favors the paradoxical opening of joints in the direction of the regional maximum horizontal stress we conclude that j3 joints propagated during the alpine compression caused the growth of the lilstock buttress anticline q 2001 published by elsevier science ltd

analysis of light hydrocarbons in soil gases lost river region west virginia relation to stratigraphy and geological structures analyses of 471 near surface soil gas samples for light hydrocarbons c1 c4 c2l c3l and h2 from the lost river gas field in hardy county west virginia reveal sites or clusters of sites containing anomalously high concentrations of light hydrocarbon gases which occur directly over the faulted eastern limb of the whip cove anticline compositional changes in the soil gases data clearly define major changes in the maturity and locations of potential source beds grids placed on botanically defined anomalies confirm a possible correlation between these two independent indicators statistical analysis shows that samples from 45 sites contain anomalously large concentrations of light hydrocarbons in the soil gas constituents large concentrations coupled with high saturate to olefin ratios further confirms that this active seepage is near macroseep levels variations in soil gas compositional trends separate the soil gas data into two domains with oilier compositions to the west and gassier compositions to the east although the composition of the shallow soil gases above the lost river gas field are oilier than the reservoir gases they occur directly over the eastern faulted limb of the producing anticlinal structure suggesting that the dry gases from the oriskany reservoir are probably mixed with oilier gases from organic rich strata among devonian shales the eastern anomalies are much gassier and are very similar to the oriskany gases produced by the lost river gas field the eastern anomalies directly overlie near vertical beds of devonian and older age formations that are likely conduits for deeper mature thermal gases

side resistance of large diameter bored piles socketed into decomposed rocks the design of large diameter bored piles socketed into rock has received considerable attention in sedimentary rocks but has only occasionally been addressed in igneous and metamorphic rocks design methods based on the performance of sockets in sedimentary rocks have been proposed in literature but it is uncertain how applicable they are to other rock types large diameter 600 mm rock socketed piles were used in several recent developments in hong kong which involved 13 large scale pile load tests in various decomposed rocks the test piles varied in length from 20 to 60 m and in diameter from 1 0 to 1 3 m the test loads were as high as 30 mn this provides a golden opportunity for a study of the performance of piles socketed in igneous volcanic and metasedimentary rocks decomposed as a result of subtropical weathering in total 35 pile tests including 13 in hong kong in decomposed rocks together with 44 other tests in sedimentary rocks are reviewed side resistance is analyzed with regard to rock type and is compared to the findings and correlations published by others the rate of mobilization of side resistance was generally scattered in the test results as were the general shapes of the resistance displacement relationships a trend line was established relating the unconfined compressive strength to side resistance for granitic rocks during bidirectional multistage tests a reduction in the socket stiffness was observed with the second test stage for a given displacement the side resistance mobilized in the second stage was less than in the first

the offshore morpho structure and tsunami sources of the viti levu seismic zone southeast viti levu fiji abstract new high resolution seabat 8160 multibeam bathymetry data reveal in detail the complex offshore morphology over part of the viti levu seismic zone vlsz in southeast viti levu the mapped seafloor is scarred by a complex network of linear submarine canyons and numerous submarine slides the submarine canyons are morphologic expressions of graben structures in the underlying basement rock submarine canyon faults are continuous with nearshore shelf faults and onshore fault controlled valleys and structural lineaments together these define continuous onshore offshore fault zones which combined form a structurally complex fault mesh of composite origin we attribute the development of the principal fault sets in the fault mesh to progressive distributed faulting in response to anticlockwise tectonic block rotations within the fiji platform during the neogene low occurrence of large earthquakes and a diffused pattern of seismicity currently observed in the vlsz may reflect complex coseismic faulting through the fault mesh the abundance of submarine slides over the vlsz which typically occur on the outer barrier reef edge as well as the submarine canyon heads and walls and mid slope imply that seismic shaking may be an important factor for triggering slope failure morphometric analysis and empirical modelling of the slides show that slides triggered in shallow water depths within 5 km of the coastline at the outer barrier reef edge and submarine canyon heads produce the largest near field tsunami amplitudes we interpret that such slides represent a significant local tsunami hazard

geomorphic expression of midcrustal extension in convergent orogens 1 channel orientation gradient drainage basin spacing drainage patterns and alluvial fan sedimentology define a set of geomorphic observables for fingerprinting modes of extensional tectonism in convergent settings anomalous finely textured trellis drainage patterns in the alps are spatially coincident with the low angle simplon and brenner detachments the detachment footwalls are characterized by numerous high angle brittle faults which are etched out by low order stream gullies and channels we quantify the relationship between these faults and watershed scale geomorphology using high resolution digital topography to extract channel and basin metrics topographic data are complemented by a field data set of channel gradients and the integrated erosional response of the watersheds preserved in valley bottom alluvial fans in footwall regions adjacent to the detachments channels are steeper more closely spaced have statistically coherent orientations and feed coarse steep alluvial fans drainage spacing increases in the footwall away from the detachment and the trellis pattern diminishes in the detachment hanging walls which typically lack high angle brittle faults there is a poor correlation between channel steepness density or orientation and hanging wall alluvial fans tend to be relatively larger gentler and debris flow dominated comparisons are made to the ticino dome region of the alps as well as to the pioneer core complex of central idaho in both cases our analysis suggests high angle brittle faulting of the footwall is particularly well preserved in the region adjacent to a detachment these results are consistent with a subvertical simple shear model for footwall extrusion as well as annealing or a lack of reactivation of brittle structures in the footwall distal to the rolling hinge

geomechanical characterisation of rock masses in alpine regions the basque arc basque cantabrian basin northern spain the geomechanical characterisation of rock masses in alpine regions is one of the main challenges currently facing rock mechanics these rock masses made up of very different materials and frequently tectonically disturbed are affected by engineering works giving rise to potentially important problems thus in the basque country these materials are at the cause of important fatalities occurring in recent years in this context we aim at characterising these materials with the ultimate purpose of predicting their behaviour the characterisation is initially approached based on the gsi mi and ci parameters following the hoek brown failure criterion this information is supplemented with field and laboratory measurements and by obtaining the rqd and rmr indices using the information obtained from 99 metering stations we develop a graphic classification procedure which allows us to distinguish materials based on their characteristics behaviour type and degree of associated problems and type and effectiveness of solutions provided eight classes of material are established

an integrated interpretation for the origin of the patrick draw oil field sage anomaly 1 the patrick draw oil field has been the site of research into surface and remote sensing methods for hydrocarbon exploration for nearly 10 yr the oil field is a stratigraphic trap with conspicuous sage vegetation on the surface and an associated tonal anomaly within that sage visible via landsat overlying the field s gas cap this paper attempts to resolve the controversy of whether the patrick draw sage anomaly is related to oil field factors or to other independent factors geology and production history of the field show the sage die out anomaly results from upward migration of injected gases and waters used to maintain reservoir pressures in the field these gases and waters produced anoxic low eh oxidation potential high ph and high salinity soils that are toxic to the overlying sage population stunted sage associated with the anomaly commonly occurs in marginal terrains in the western united states and is not tied uniquely to oil fields a velocity for the seeping gases of 250 1000 ft yr 76 305 m yr was calculated from the reservoir to the surface failure to account for the lag time associated with movement of seepage to the surface has been a source of misinterpretation

seismic bearing capacity of a strip footing on rock slopes most of the seismic calculations currently used for the evaluation of seismic bearing capacity are formulated in terms of a linear mohr coulomb failure criterion however experimental evidence sho

excavation damaged zone division and time dependency deformation prediction a case study of excavated rock mass at xiaowan hydropower station abstract rock mass excavation is accompanied by rock deformation during unloading which degrades the quality of rock mass and significantly affects the safety and stability of rock mass engineering taking the excavated rock mass from the dam foundation of xiaowan hydropower station as the study object long time single hole acoustic tests shat were conducted in the dam abutment rock mass with the changes in the acoustic wave velocity recorded then a new method quantifying the excavation damaged zone edz was proposed according to the cumulative degradation rate of acoustic wave velocity and a time dependency model for evaluating the evolution of the excavation heavily damaged zone ehdz was established the results indicated that the cumulative degradation rate curves of the wave velocity along the boreholes exhibited significant differences in time and space the depth corresponding to the inflection point on the curve can be regarded as the bottom boundary of the ehdz which could be used to generate time dependency curves and demonstrate the spatiotemporal evolution process for the ehdz the time dependency curves can be classified into three categories the differences between the classified curves are related to the depth of the initial ehdz ehdz0 rock mass elastic modulus e and unloading stress u the time dependency model for the ehdz evolution process follows a negative exponential function the ehdz0 depth e and u can determine the coefficients of the model the model provides an effective method to predict ehdz depths at different times after rock mass excavation the prediction results are of considerable significance for researches on the unloading failure and the selection of rock mass reinforcement which would ensure the stability and safety of the rock mass engineering during construction and operation

hydrocarbon microseepage related geobotanical analysis in and around oil fields hydrocarbon microseepage can be detected by its altering effect on rocks soils and overlying vegetation this study examines the impact of hydrocarbon seepage on vegetation microseeping hydrocarbons alter soil chemistry often creating an environment that can impact the health of overlying vegetation these effects can be observed using remote sensing blackburn and eagle springs oil fields in nevada patrick draw and little buffalo basin oil fields in wyoming and cement oil field in oklahoma were selected for this study because previous investigations confirmed the presence of microseeping hydrocarbons in these locations in this study moderate resolution imaging spectroradiometer s modis monthly average normalized difference vegetation index ndvi data from january 2003 to december 2012 were used to observe vegetation health inside oil fields average ndvi was calculated for these locations the typical range of ndvi in desert environments such as those observed in semi arid desert environments

strike slip fault propagation cleavage in carbonate rocks the mattinata fault zone southern apennines italy disjunctive spaced solution cleavage in carbonate rocks is genetically associated with the propagation of the left lateral strike slip mattinata fault in the gargano promontory italy typical cleavage development is restricted within the 200 300 mwide fault zone which is bounded by virtually unfractured wall rocks the cleavage consists of sub parallel solution surfaces which are often reactivated as sheared solution planes geometrical and kinematic relationships exist between the fault and the associated cleavage planes thus 1 cleavage fault intersection lines lie parallel to the fault and the sheared cleavage rotational axes and 2 the cleavage fault angle is almost constantly equal to 408 a model for the development of the mattinata fault is proposed in which the cleavage surfaces are interpreted as fault propagation deformations cleavage nucleates as solution planes at the front of the advancing fault as the result of stress concentration in this region two distinct time sequential processes are shown to operate during the fault propagation 1 typical millimetre to centimetre spaced solution surfaces form in the distal tip zone of the advancing fault plane 2 as the tip advances the fault plane breaks through the cleavage as minor shear displacements reactivate some of these nascent surfaces these observations may prove useful in understanding mechanisms for fault controlled enhanced reduced permeability and fluid pathways 1999 elsevier science ltd all rights reserved

seismic and static 3d stability of two stage rock slope based on hoek brown failure criterion two stage slope is beneficial to improve slope stability in comparison with single stage slope based on nonlinear hoek brown criterion a three dimensional failure mechanism is employed to estimate the stability of two stage rock slope with the effect of seismic inertia force being taken into account a generalized tangential technique is used to formulate the stability factor problem as a classical optimization problem corresponding to the dissipated energy the upper bound solutions are obtained by minimizing the objective function with respect to the location of sliding body center and the location of tangency point the seismic inertia force is considered and incorporated into the objective function in comparison with previously published solutions using the linear mohr coulomb criterion the validity of the present solutions is shown the analytical expressions for two stage slope are derived to estimate the seismic stability of slopes numerical results for different types of rocks are presented

a new method of fracture analysis azimuth versus traverse distance plots traditional fracture analysis emphasizes the statistics of fracture orientations at individual stations a new method the azimuth versus traverse distance plot avtd is proposed whereby map patterns and fracture domain boundaries receive much greater emphasis the method can be applied to any area where outcrop is nearly continuous and map data can be represented by strike alone ideal features for the method are nearly vertical joint sets which can be plotted on the proposed avtd diagrams and contoured with concentration factor statistics somewhat analogous to those used for equal area plots examples of avtd plots are given for jointing in the southern beartooth mountains wyoming illustrating ways in which generally overlooked joint set patterns may be identified and ways in which joint domain boundaries may be integrated in geologic mapping using the plots the examples show the utility of the method in assigning relative ages to fracture domains in relating the domain distributions to other structures and in testing for tectonic heredity of older fractures by upward propagation through an unconformity

solution of the ultimate bearing capacity at the tip of a pile in inclined rocks based on the hoek brown criterion abstract to investigate the bearing mechanism of piles in inclined slope this paper proposed an analytical method through geometric transformation to calculate the ultimate bearing capacity at the tip of a pile in inclined rocks based on the characteristic line method it was found that there were five failure modes for piles in inclined rocks depending on the embedment ratios slope angles average overburden load and tensile strength parameter of the rock mass when the pile failure mode was under the modes of deep pile with minor overburden dl and deep pile with major overburden dh the ultimate bearing capacity had no change as the slope angle and the pile embedment ratio changed when the pile was under the failure modes of semi deep pile with minor overburden sl semi deep pile with major overburden sh or shallow pile ss the ultimate bearing capacity decreased with an increasing rate as the slope angles increased and to get the same ultimate bearing capacity at the pile tip the pile embedment ratio should increase the proposed analytical method can be served as an efficient method to estimate the bearing capacity of piles in inclined slope with small slope angle typically less than 40

stress perturbations registered by jointing near strike slip normal and reverse faults examples from the ebro basin spain stress perturbation patterns created by coeval and preexisting fault planes are characterized by means of detailed mapping and analysis of joint sets in miocene carbonates of the tudela area strike and spacing of the pervasive n s joint set have been specially surveyed for this purpose their spatial variations have been analyzed and interpreted in the light of different theoretical models proposed by other authors perturbations inferred near strike slip faults correspond to the classical examples related to compressional and extensional fault tips a normal fault striking oblique to the horizontal stress axes deflects the latter toward making 2 and 3 trajectories parallel and perpendicular respectively to the fault strike while causing an abrupt stress release within the footwall near a reverse fault with a small dextral component the deflection of 1 trajectories is gentle but a significant increase of differential stress occurs in the hanging wall

stability of highly fractured infinite rock slopes with nonlinear failure criteria and nonassociated flow laws the effect of the dilatancy phenomenon on rock masses is not usually considered when calculating slope stability a theoretical analysis has been conducted on the stability of infinite rock slopes

distinct element method simulations of rock socketed piles estimation of side shear resistance considering socket roughness abstractrock socketed piles are foundational elements designed to transmit large concentrated loads to stronger materials located at greater depths the rock socket side shear resistance is commonl

combined geological and surface geochemical methods discovered agaritta and brady creek fields concho county texas from december 1987 to march 1991 25 prospects in the lower king sand upper pennsylvanian cisco play in concho county texas were tested by several operators they used combinations of subsurface geology reconnaissance airborne gas sensing surface radiometrics soil magnetic susceptibility and soil gas hydrocarbon measurements to define prospects six new king sand discoveries or extensions and three deeper goen discoveries resulted in a 36 exploratory success rate the total exploration and development cost was approximately 0 67 bbl of proven producing oil reserves final locations for the discovery wells on each of the nine successful prospects were selected primarily on the basis of combined subsurface geology and surface geochemical data as examples we present information about the discovery of brady creek and agaritta fields agaritta field is one of the two largest of the new field discoveries with estimated proven producing recoverable reserves of 6 million bbl of oil its discovery was based on a combination of 1 regional subsurface geologic projection 2 airborne hydrocarbon sensing 3 interstitial soil gas hydrocarbon data 4 soil magnetic susceptibility measurements and 5 surface potassium and uranium concentrations measured by gamma ray spectrometry

morphostructural analysis and cenozoic evolution of elephant island southern scotia arc antarctica elephant island located in the vicinity of the present day active boundary of the south shetland block and the antarctic and scotia plates is a region of particular interest for understanding the past and present geodynamic evolution of the southern scotia arc lineament from different data sources field measured fractures and geomorphological evidences have been analysed in this context the lineaments extracted from aerial photographs 1 624 from a dem 348 and from radarsat 2 satellite data 1 365 indicate four dominant lineament sets with ne sw nw se n s and w e strikes all data sources identified similar lineament families but differences in the frequency distributions and subsequently on the dominant orientations were observed the measurements direct of fractures were obtained from 23 sites in the field at which 278 planes were measured fracture planes indicate main modes trending in the nne ssw and nnw sse directions and a secondary mode in the e w the major trends of the fracture measurements and the lineaments display a good correlation in the e w direction however there is an angular variation in the azimuth values of the nne sse and nnw sse fractures with respect to the n s ne sw and nw se orientations of the lineaments of approximately 20 this trend deviation may be due to the fact that mapped lineaments are composed of small fracture sets that may be related to shear fractures that cannot be distinguished at the aerial photograph or radar satellite data scales submerged sea floor morphological feature orientations match the studied morphostructures on the island and the main tectonic structures in this part of the scotia arc a linkage of the main lineament families to the tectonic stages from the oligocene to the present has been proposed taking into account the information of the orientation and sense of movement of the fractures and stresses in the elephant island region

tests of the interface between sand and steel in the simple shear apparatus the simple shear apparatus is used for tests on the interface between soil and other construction materials a comparison was made of its advantages and disadvantages as well as of the test results for sand steel interfaces with respect to three other types of interface testing apparatuses the direct shear the annular shear and the ring torsion types a simple shear apparatus is less sophisticated than a ring torsion apparatus mainly in the non uniformity of the stress distributions but it can be used with much less technical difficulty good agreement was observed between the results from the three types on the correlations between the coefficient of friction and the roughness of the steel surface the sliding displacement measured in simple shear tests showed good agreement with the observation in the ring torsion type of apparatus but the tangential displacement in the direct shear test was larger possibly because it included the displacement due to the strain in the sand mass inside the shear b

detailed compositional analysis of gas seepage at the national carbon storage test site teapot dome wyoming usa abstract a baseline determination of co2 and ch4 fluxes and soil gas concentrations of co2 and ch4 was made over the teapot dome oil field in the naval petroleum reserve no 3 npr 3 in wyoming usa this was done in anticipation of experimentation with co2 sequestration in the pennsylvanian tensleep sandstone underlying the field at a depth of 1680 m the baseline data were collected during the winter 2004 in order to minimize near surface biological activity in the soil profile the baseline data were used to select anomalous locations that may be the result of seeping thermogenic gas along with background locations five 10 m holes were drilled 3 of which had anomalous gas microseepage and 2 were characterized as background these were equipped for nested gas sampling at depths of 10 5 3 2 and 1 m depths methane concentrations as high as 170 000 ppmv 17 were found along with high concentrations of c2h6 c3h8 n c4h10 and i c4h10 much smaller concentrations of c2h4 and c3h6 were observed indicating the beginning of hydrocarbon oxidation in the anomalous holes the anomalous 10 m holes also had high concentrations of isotopically enriched co2 indicating the oxidation of hydrocarbons concentrations of the gases decreased upward as expected indicating oxidation and transport into the atmosphere the ancient source of the gases was confirmed by 14c determinations on co2 with radiocarbon ages approaching 38 ka within 5 m of the surface modeling was used to analyze the distribution of hydrocarbons in the anomalous and background 10 m holes diffusion alone was not sufficient to account for the hydrocarbon concentration distributions however the data could be fit with the addition of a consumptive reaction first order rate constants for methanotrophic oxidation were obtained by inverse modeling high rates of oxidation were found particularly near the surface in the anomalous 10 m holes demonstrating the effectiveness of the process in the attenuation of ch4 microseepage the results also demonstrate the importance of ch4 measurements in the planning of a monitoring and verification program for geological co2 sequestration in sites with significant remaining hydrocarbons i e spent oil reservoirs

roughness and unit side resistances of drilled shafts socketed in clay shale and limestone rock socketed drilled shafts are being used increasingly to support heavily loaded structures rock sockets provide resistance to the load through a combination of side and base resistances in this study the effect of drilling tools such as an auger and a core barrel on the unit side resistance was investigated a total of four field studies were performed on clay shale compressive strength of 1 2 mpa and limestone compressive strength of 10 mpa borehole roughnesses produced by the different types of drilling tools in clay shale and limestone were measured using a laser borehole roughness profiler developed in this study to measure roughness to 0 5 mm in the boreholes based on the results of this study it was observed that the drilling tools developed different socket roughnesses which in turn affected the side resistances of the rock socketed drilled shafts

distinct element method simulations of rock concrete interfaces under different boundary conditions abstract the shear behaviour of concrete rock interfaces has been the aim of extensive research in geotechnical engineering applications such as rock socketed piles rock bolts and concrete dam arch bridge foundations several experimental studies through direct shear tests have been conducted to evaluate the shear behaviour of rock concrete interfaces under cnl constant normal load and cns constant normal stiffness conditions in this paper pfc2d numerical simulations of unbonded rock concrete planar and saw tooth triangular joints under cnl and cns boundary conditions are conducted using the shear box genesis sbg approach proposed by bahaaddini et al 2013b the numerical simulation results are compared with experimental data published by gutierrez 2013 and gu et al 2003 results indicate that the sbg approach reproduces suitably the shear behaviour failure mode and asperity damage of unbonded planar and triangular rock concrete interfaces specially under cnl conditions

kerogen maturation data in the uinta basin utah usa constrain predictions of natural hydrocarbon seepage into the atmosphere natural seepage of methane from the lithosphere to the atmosphere occurs in regions with large natural gas deposits according to some authors it accounts for roughly 5 of the global methane budget i explore a new approach to estimate methane fluxes based on the maturation of kerogen which is the hydrocarbon polymer present in petroleum source rocks and whose decomposition leads to the formation of oil and natural gas the temporal change in the atomic h c ratio of kerogen lets us estimate the total carbon mass released by it in the form of oil and natural gas then the time interval of active kerogen decomposition lets us estimate the average annual formation rate of oil and natural gas in any given petroleum system which i demonstrate here using the uinta basin of eastern utah as an example obviously this is an upper bound to the average annual rate at which natural gas seeps into the atmosphere after adjusting for biooxidation of natural gas i conclude that the average annual seepage rate in the uinta basin is not greater than 3100 900 tonne yr 1 this is 0 5 0 15 of the total flux of methane into the atmosphere over the basin as measured during aircraft flights i speculate about the difference between the regional 0 5 and the global 5 estimates

a study of joints and stress release buckles in palaeozoic rocks of the niagara peninsula southern ontario joint sets in palaeozoic bedrock of the niagara peninsula occur at 005 045 085 and 135 orientations there is no consistent change in joint orientation with lithology rock age or location within the area drainage pattern analysis using airphotos and topographic maps indicates that glacial drift effectively masks underlying joint systems rare calcite and gypsum mineralization occurs along joints of 085 and 135 trend stress relief buckles indicate a contemporary maximum principal stress along an 050 trend joint systems in the niagara peninsula are similar in trend to those on the appalachian plateau

remote sensing and geochemistry for detecting hydrocarbon microseepages this work tests the hypothesis that chemical and mineralogical alterations in rocks and soils are related to hydrocarbon microseepages above some of the major oil fields in this study we used hyperion hyperspectral imaging sensors to map alterations that appear to be associated with hydrocarbon microseepages in the patrick draw area of wyoming our mineralogical geochemical and carbon isotope data support the presence of hydrocarbon microseepages satellite imagery training classifications defined by areas of hydrocarbon microseepage have resulted in the successful identification of the areal extent of an anomalous area geochemical characteristics of samples that define this anomalous area were then compared to the remaining non anomalous samples using x ray diffraction xrd reflectance spectroscopy and carbon isotope techniques xrd analyses demonstrated the increased presence of feldspars in non anomalous samples compared to anomalous samples spectroscopy results demonstrated higher proportions of clays within the anomalous samples compared to non anomalous samples the 13 c values range from 2 88 to as low as 45 32 indicating hydrocarbon sources these methods may provide a foundation upon which further hydrocarbon exploration techniques can develop

the 1983 landsat soil gas geochemical survey of patrick draw area sweetwater county wyoming the geosat test site at patrick draw wyoming was resampled during the summer field season of 1983 to conduct a more detailed soil gas survey on and around the area s producing fields the results of this study agree with the 1980 geosat assessment that the faults and fractures visible as linear features on satellite and aircraft imagery provide paths for active microseepage of hydrocarbons from depth to the near surface this association is particularly true near the earlier described blighted sage zone where extensive resampling reveals a much wider area of anomalously high free soil gas values and fluorescence than was previously reported discriminant analysis suggests that the geochemical seepage signature found over the fields differs statistically from that present for adjacent areas of no known production this observation was found to be true for all three soil gas techniques used in this study anomaly patterns appear to be related to the type of soil gas sample studied data obtained from shallow free soil gas samples reveal that direct anomalies controlled by faults and fractures formed over production whereas data obtained from samples treated by acid extraction or thermal mechanical disaggregation techniques exhibit magnitude lows over the producing areas such patterns indicate halo features around the composite producing areas at present this conflicting behavior cannot be explained

analysis of lineaments and their relationship to neogene fracturing se viti levu fiji the fiji archipelago lies along a complex active section of the pacific and australian plate boundary zone in the sw pacific the availability of a range of remotely sensed imagery and recent field studies have permitted the exploration of the link between lineaments as seen on such imagery and tectonic fractures observed on the ground in se viti levu the main island of fiji comparisons of statistical orientation peaks as well as the spatial extent of lineaments with field mapped fractures indicate that the lineaments are largely a reflection of tectonic fractures in the bedrock emphasized on the surface by topography drainage and vegetation surface lineaments correspond to broad zones of intense fracturing and strongly influence the landform features of the area it appears that surface fracture sets are open upward splay zones that merge downward into single planar discontinuities represented by sparse uninterrupted magnetic lineaments at depth fault correlated lineament sets extend over greater geographical distances than the equivalent mapped fault zones and these lineament sets represent more complex regional structural patterns than previously known this study provides an approach to mapping fracture patterns where outcrop is limited and where conventional field mapping techniques of structural geology are impractical it highlights the benefits of mapping lineaments from multiple sets of remote sensing imagery of the surface and bedrock mapping them at regional and larger scales as well as linking lineaments to detailed field mapped structures lineament data derived using such an approach can be used effectively to characterize regional structural patterns which in turn may provide better understanding of the structural and tectonic evolution and seismic hazards of the region this approach may also find useful application in groundwater mineral and oil and gas exploration

investigation of a surface spectral anomaly at table rock gas field wyoming airborne spectroradiometer data reveal an unusual pattern of near infrared reflectance at the exposed center of table rock anticline sweetwater county wyoming the feature is represented by a reflectance minimum near 2200 nm characteristic of areas with abundant clay minerals smectite and mixed layer illite smectite were found associated with the anomalous spectral feature concentrations of iron and sulfate minerals in the soils at the center of the clay rich zone correspond roughly to an area of red coloring in the wasatch formation exposed at the highest structural elevation in the center of the anticline a photogeologic interpretation of thematic mapper simulator tms image data was made for the table rock area stratigraphic and structural details of the interpretation are excellent and provide greater detail than do available maps of the area structural analysis suggests that at least two episodes of stress affected the area the greatest concentration of fractures occurs at the crest of the

biogenic thermogenic near surface gas anomaly over gingin and bootine gas fields western australia anomalous concentrations of methane 5 to 1 000 ppm sgrc2 c4 0 5 16 2 ppm ethylene 0 00 23 0 ppm helium 5 30 6 4 ppm and hydrogen 25 ppm to approx5 are found in overburden gases from depths of 6 m 19 7 ft over the subcrop of a major fault that intersects the gingin gas reservoir western australia a helium anomaly 5 5 5 8 ppm with no associated hydrocarbon anomaly is present over the subcrop of a fault within the nearby bootine structure normalization of the helium data with neon 20 eliminates much of the anomaly leaving only two sites over gingin and the single site at bootine with above background helium concentrations at other sample sites the elevated helium concentrations are reduced to near atmospheric values and thus must be due to residual enrichment resulting from the consumption of major gas components presumably by near surface biologic processes ethylene hydrogen and perhaps some methane are products of these processes however the restricted occurrence of the overburden gas anomaly over a fault and the presence of anomalous c2 c4 alkanes and helium suggest that gas is leaking from the reservoir therefore the biologic activity causing the helium enrichments is probably due to alkane oxidizing microorganisms such microorganisms are likely to be present in all oil and gas seeps hence the expression of such seeps shown by surface gas surveys will always be a combination of near surface biogenic effects and deep seated thermogenic effects

tectonic processes and geomorphological design abstract deep seated geodynamic processes are the cause of the existence of the geotectonic stress field the influence of the latter and therefore of deep seated processes in surface geomorphology is investigated it is noted that the features caused by deep seated geotectonic processes can be distinguished from those caused by exogenic agents weather erosion etc by their statistical characteristics all statistically systematic features are of geotectonic origin random features are of exogenic origin in this paper various types of morphological features are analyzed with regard to their origin it is shown that lineaments seen on air photographs may not be of recent geotectonic origin specific examples of such lineaments being erosion scarps are given next it is shown that the orientation patterns inherent in fluvial and glacial valleys are indeed affected to a large extent by neotectonic processes the same is naturally the case for rift valleys and chains of volcanoes a further interesting subject is presented by the so called tectonic landforms inselbergs cirques the shapes of mountain summits etc are all shown to be directly or indirectly caused by deep seated processes the mass movements on slopes are also of great importance although it is often thought that these are triggered by meteorological conditions it is shown that their basic design is influenced to a large extent by deep seated processes amongst other things this is borne out by a correlation between landslide and earthquake activity finally it is mentioned that the common joints on rock outcrops are also designed by the neotectonic stress field and that the latter can in fact be determined by an analysis of joint orientations in summary it may be stated that although exogenic agents may be responsible for many morphological features deep seated processes have nevertheless a great influence on the fundamental design of such features

the role of tectonic inheritance in the morphostructural evolution of the galicia continental margin and adjacent abyssal plains from digital bathymetric model dbm analysis nw spain the identification of recent major tectonic structures in the galicia continental margin and adjacent abyssal plains was carried out by means of a quantitative analysis of the linear structures having bathymetric expression on the seabed it was possible to identify about 5800 lineaments throughout the entire study area of approximately 271 500 km2 most lineaments are located in the charcot and coruna highs in the western sector of the galicia bank in the area of the marginal platforms and in the northern sector of the margin analysis of the lineament orientations shows a predominant ne sw direction and three relative maximum directions nw se e w and n s the total length of the lineaments identified is over 44 000 km with a mode around 5000 m and an average length of about 7800 m in light of different tectonic studies undertaken in the northwestern margin of the iberian peninsula we establish that the lineaments obtained from analysis of the digital bathymetric model of the galicia continental margin and adjacent abyssal plains would correspond to fracture systems in general the orientation of lineaments corresponds to main faults tectonic structures following the directions of ancient faults that resulted from late stages of the variscan orogeny and mesozoic extension phases related to triassic rifting and upper jurassic to early cretaceous opening of the north atlantic ocean the n s convergence between eurasian and african plates since palaeogene times until the miocene and nw se convergence from neogene to present reactivated the variscan and mesozoic fault systems and related physiography

side resistance rock sockets in sandstone mudstone and shale the fundamental parameters of rock strength rock mass stiffness and interface roughness that control the development of side shear in a rock socketed pile are discussed on the basis of results fr

ultimate bearing capacity at the tip of a pile in rock based on the modified hoek brown criterion a method for calculating the ultimate bearing capacity at the tip of a pile is presented

model for hydrocarbon microseepage and related near surface alterations despite recent advances in surface and near surface geochemical methods there continues to be a need for improved understanding of the scientific basis relating these methods to petroleum deposits we have reviewed the literature pertinent to the several methods we have used and integrated that information with some 100 man years of our experience to contribute to that end evidence indicates that hydrocarbon micro seepage from reservoirs most probably involves buoyant colloidal size microbubbles of light hydrocarbons principally methane through the butanes ascending relatively rapidly through a water filled network of fractures joints and bedding planes bacterial consumption of these hydrocarbons creates carbon dioxide and hydrogen sulfide which may alter sediments producing detectable modifications in geomorphic seismic magnetic and radiometric properties we have used combinations of 1 airborne microwave sensing and laboratory analyses of soil gas hydrocarbons 2 shallow source aeromagnetic and soil magnetic susceptibility measurements 3 aerial and surface gamma ray measurements and 4 geomorphology to find productive oil and gas deposits results suggest that using these methods can substantially increase the probability of wildcat success and reduce finding costs in selected geologic settings however these surface methods cannot reveal depth size or quality of reservoirs or even if producible hydrocarbons will be found

anomaly may not reflect hydrocarbon seepage patrick draw field wyoming revisited researchers cite the patrick draw wyoming section of the joint nasa geosat test cast project as an example of a vegetation community influenced by hydrocarbon microseepage the community presumed to be so influenced is visible as a tonal anomaly on satellite imagery this study and the nasa geosat study indicate that evidence supporting this assumption is not yet substantiated examination of the dominant sagebrush subspecies at patrick draw shows its general growth form is stunted both inside and outside the study area therefore stuntedness is not a specific indicator of hydrocarbon microseepage the sparse distribution of vegetation results in more soil exposure and this rather than the stuntedness of the sagebrush best accounts for the appearance of the area as tonal anomaly on imagery air photos and images taken on various dates indicate that vegetation began to deteriorate to the point that it became visible on unenhanced imagery sometime between 1978 and 1983 corresponding to a period of increased annual average precipitation soils within the anomaly had a high sodium absorption ratio compared to soils outside the anomaly indicating soil osmotic factors may be stressing the vegetation soil gas surveys and a biogeochemical survey provide the strongest evidence that the area is influenced by hydrocarbons however the die off of sagebrush and interspace grass and hence the appearance of the tonal anomaly on imagery may be specifically related to anaerobic conditions in the root zone and or dissolved salts in the soil water solution re ulting from the increased precipitation the coincidence of a fault and contact of the wasatch and fort union formations within the anomaly may explain why the anomaly occurs where it does but we do not see distinctive evidence linking when the anomaly appeared on imagery to when gas and water reinjection occurred in wells

an equivalent continuum model for coupled stress and fluid flow analysis in jointed rock masses to provide a set of governing equations for solving the coupled stress and fluid flow a rock mass which commonly contains a large number of geological discontinuities is treated as an anisotropic elastic porous medium with the corresponding elastic compliance and permeability tensors hydro mechanical equivalents to the discontinuous mass the hydromechanical equivalents with the special emphasis on the permeability tensor are formulated on the assumption that any crack can be replaced by a set of parallel planar plates connected by two springs two dimensional numerical analyses on seepage flow networks support the validity of the permeability tensor some field evidence is analyzed to examine the applicability of the present model for the practical purpose of rock hydraulics

stability analysis of rock slopes subjected to seepage forces using the modified hoek brown criterion abstract the paper deals with the stability analysis of a water saturated rock slope by means of the kinematic approach of limit analysis theory particular emphasis is first given to the effects of pore water pressure on the global stability of geotechnical structures the rock strength properties being formulated in terms of effective stresses it is shown how the effect of seepage flow may be accounted for such an analysis through driving body forces derived from the gradient of excess pore pressure distribution is shown the latter is obtained as the solution to a hydraulic boundary value problem and then incorporated as external loading in the subsequent stability analysis the rock strength properties are modeled by a modified hoek brown failure criterion for which closed form expressions of the support functions have been derived in a previous paper the approach is then applied to investigate the stability of rock slopes computational results are given providing ample evidence of the destablizing effects induced by the seepage forces the influence of relevant geometrical strength and loading parameters is also discussed

landsat and soil gas geochemical study of patrick draw oil field sweetwater county wyoming adsorbed free and headspace soil gas samples collected from the patrick draw field wyoming were analyzed by routine geochemical techniques gas chromatography was used to determine the light hydrocarbon c1 to c7 paraffins concentrations in the samples anomalous hydrocarbon concentrations appear in those areas near lineaments mapped from landsat images of the patrick draw field these lineaments represent extensional faults and fractures produced during development of the rock springs uplift to the west because several of these mapped lineaments extend to depth they are able to serve as conduits allowing the preferential microseepage of hydrocarbons to the surface from the reservoir rock these effusive soil gases in the patrick draw area i dicate the nature of the expected hydrocarbons at depth further by targeting easily observable pervasive lineaments studies of this nature might be useful as a fast and economical means to screen out or high grade areas of potential hydrocarbon plays this approach should prove particularly helpful in frontier areas where predictive information would be valuable

ultimate bearing capacity of rock masses based on modified mohr coulomb strength criterion a method for calculating the bearing capacity of spread foundations in rock is presented bearing capacity of spread foundations on rock masses based on modified mohr coulomb strength criterion charts and figures are presented for a quick obtaining of bearing capacity for shallow foundations comparison of the ultimate bearing capacity using the hoek and brown criterion and the modified mohr coulomb strength criterion