long term surface temperature modeling of pluto abstract nasa s new horizons reconnaissance of the pluto system has revealed at high resolution the striking albedo contrasts from polar to equatorial latitudes on pluto as well as the sharpness of boundaries for longitudinal variations these contrasts suggest that pluto must undergo dynamic evolution that drives the redistribution of volatiles using the new horizons results as a template we explore the surface temperature variations driven seasonally on pluto considering multiple timescales these timescales include the current orbit 248 years as well as the timescales for obliquity precession peak to peak amplitude of 23 over 3 million years and regression of the orbital longitude of perihelion 3 7 million years these orbital variations create epochs of extreme seasons where one pole receives a short relatively warm summer and long winter while the other receives a much longer but less intense summer and short winter we use thermal modeling to build upon the long term insolation history model described by earle and binzel 2015 and investigate how these seasons couple with pluto s albedo contrasts to create temperature effects from this study we find that a bright region at the equator once established can become a site for net deposition we see the region informally known as sputnik planitia as an example of this and find it will be able to perpetuate itself as an always available cold trap thus having the potential to survive on million year or substantially longer timescales meanwhile darker low albedo regions near the equator will remain relative warm and generally not attract volatile deposition we argue that the equatorial region is a preservation zone for whatever albedo is seeded there this offers insight as to why the equatorial band of pluto displays the planet s greatest albedo contrasts

developments in the characterization of complex rock slope deformation and failure using numerical modelling techniques recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms processes involved and the associated risk this paper illustrates how rock slope analyses may be undertaken using three levels of sophistication level i analyses include the conventional application of kinematic and limit equilibrium techniques with modifications to include probabilistic techniques coupling of groundwater simulations and simplistic treatment of intact fracture and plastic yield such analyses are primarily suited to simple translational failures involving release on smooth basal rear and lateral surfaces where the principle active damage mechanisms are progressive failure and or asperity breakdown level ii analyses involve the use of continuum and discontinuum numerical methods in addition to simple translation level ii techniques can be applied to complex translational rock slope deformations where step path failure necessitates degradation and failure of intact rock bridges along basal rear and lateral release surfaces active damage processes in this case comprise not only strength degradation along the release surface e g asperity breakdown but also a significant component of brittle intact rock fracture level iii analyses involve the use of hybrid continuum discontinuum codes with fracture simulation capabilities these codes are applicable to a wide spectrum of rock slope failure modes but are particularly well suited to complex translation rotational instabilities where failure requires internal yielding brittle fracturing and shearing in addition to strength degradation along release surfaces through a series of rock slope analyses the application of varied numerical methods are discussed particular emphasis is given to state of the art developments and potential use of level iii hybrid techniques d 2005 elsevier b v all rights reserved

numerical simulation of sand waves in a turbulent open channel flow we develop a coupled hydro morphodynamic numerical model for carrying out large eddy simulation of stratified turbulent flow over a mobile sand bed the method is based on the curvilinear immersed boundary approach of khosronejad et al adv water resour vol 34 2011 pp 829 843 we apply this method to simulate sand wave initiation growth and evolution in a mobile bed laboratory open channel which was studied experimentally by venditti church j geophys res vol 110 2005 f01009 we show that all the major characteristics of the computed sand waves from the early cross hatch and chevron patterns to fully grown three dimensional bedforms are in good agreement with the experimental data both qualitatively and quantitatively our simulations capture the measured temporal evolution of sand wave amplitude wavelength and celerity with good accuracy and also yield three dimensional topologies that are strikingly similar to what was observed in the laboratory we show that near bed sweeps are responsible for initiating the instability of the initially flat sand bed stratification effects which arise due to increased concentration of suspended sediment in the flow also become important at later stages of the bed evolution and need to be taken into account for accurate simulations as bedforms grow in amplitude and wavelength they give rise to energetic coherent structures in the form of horseshoe vortices which transport low momentum near bed fluid and suspended sediment away from the bed giving rise to characteristic boil events at the water surface flow separation off the bedform crestlines is shown to trap sediment in the lee side of the crestlines which coupled with sediment erosion from the accelerating flow over the stoss side provides the mechanism for continuous bedform migration and crestline rearrangement the statistical and spectral properties of the computed sand waves are calculated and shown to be similar to what has been observed in nature and previous numerical simulations furthermore and in agreement with recent experimental findings singh et al water resour res vol 46 2010 pp 1 10 the spectra of the resolved velocity fluctuations above the bed exhibit a distinct spectral gap whose width increases with distance from the bed the spectral gap delineates the spectrum of turbulence from the low frequency range associated with very slowly evolving albeit energetic coherent structures induced by the migrating sand waves overall the numerical simulations reproduce the laboratory observations with good accuracy and elucidate the physical phenomena governing the interaction between the turbulent flow and the developing mobile bed

numerical analysis of initiation and progressive failure in natural rock slopes the 1991 randa rockslide the 1991 randa rockslide in the swiss alps involved several complex mechanisms relating to geological mechanical and hydrological processes for which no clear trigger can be asserted this paper investigates the concept of progressive failure and the numerical modelling of rock mass strength degradation in natural rock slopes using the randa rockslide as a working example results from continuum i e finite element modelling are presented to illustrate a hypothesis suggesting that initiation of a progressive rock mass degradation process ultimately leading to failure began following deglaciation of the valley below discontinuum distinct element modelling is then applied to investigate the underlying mechanisms contributing to the episodic nature of the rockslide finally the use of a hybrid method that combines both continuum and discontinuum techniques to model fracture propagation are discussed in the context of modelling progressive slide surface development linking initiation and degradation to eventual catastrophic failure

thermal properties of rhea s poles evidence for a meter deep unconsolidated subsurface layer abstract cassini s composite infrared spectrometer cirs observed both of rhea s polar regions during a close 2000 km flyby on 9th march 2013 during orbit 183 rhea s southern pole was again observed during a more distant 51 000 km flyby on 10th february 2015 during orbit 212 the results show rhea s southern winter pole is one of the coldest places directly observed in our solar system surface temperatures of 25 4 7 4 k and 24 7 6 8 k are inferred from orbit 183 and 212 data respectively the surface temperature of the northern summer pole inferred from orbit 183 data is warmer 66 6 0 6 k assuming the surface thermophysical properties of the two polar regions are comparable then these temperatures can be considered a summer and winter seasonal temperature constraint for the polar region orbit 183 will provide solar longitude ls coverage at 133 and 313 for the summer and winter poles respectively while orbit 212 provides an additional winter temperature constraint at ls 337 seasonal models with bolometric albedo values between 0 70 and 0 74 and thermal inertia values between 1 and 46 j m 2 k 1 s 1 2 otherwise known as mks units can provide adequate fits to these temperature constraints assuming the winter temperature is an upper limit both these albedo and thermal inertia values agree within the uncertainties with those previously observed on both rhea s leading and trailing hemispheres investigating the seasonal temperature change of rhea s surface is particularly important as the seasonal wave is sensitive to deeper surface temperatures tens of centimeters to meter depths than the more commonly reported diurnal wave typically less than a centimeter the exact depth difference dependent upon the assumed surface properties for example if a surface porosity of 0 5 and thermal inertia of 25 mks is assumed then the depth of the seasonal thermal wave is 76 cm which is much deeper than the 0 5 cm probed by diurnal studies of rhea howett et al 2010 the low thermal inertia derived here implies that rhea s polar surfaces are highly porous even at great depths analysis of a cirs focal plane 1 10 600 cm 1 stare observation taken during the orbit 183 encounter between 16 22 33 and 16 23 26 ut centered on 71 7 w 58 7 s provides the first analysis of a thermal emissivity spectrum on rhea the results show a flat emissivity spectrum with negligible emissivity features a few possible explanations exist for this flat emissivity spectrum but the most likely for rhea is that the surface is both highly porous and composed of small particles

back analysis of the joss bay chalk cliff failure using numerical modelling use of numerical modelling for back analysis of slope failure can provide a valuable insight into the underlying failure mechanisms and improve our understanding of factors controlling instability and geomorphology of slopes this paper provides a brief overview of the range of methods that are available for slope instability analyses and their respective benefits using the back analysis of the joss bay chalk cliff failure as a case example a variety of analytical and numerical approaches are used to back analyse the failure to assess the potential impact of both the rock mass strength and discontinuity controlled behaviour on the potential failure mechanism limit equilibrium analysis approaches are used to assess the sensitivity of the simulated model to variation in input parameters numerical simulation constrained by the limit equilibrium models is then used to evaluate the progressive nature of failure mechanism and directly simulate the trigger mechanism importantly the modelling demonstrates that shear strain initiates at the base of the cliff and subsequently extends upwards resulting in tensile failure in the upper part of the slope the case example demonstrates the capability of numerical models to simulate the progressive nature of slope failure and their ability to evaluate the detrimental effects of a wave cut notch at the base of a cliff

global color and albedo variations on triton global multispectral mosaics of triton have been produced from voyager approach images six spectral units are defined and mapped the margin of the south polar cap spc is scalloped and ranges in latitude from 10 deg to 30 deg a bright fringe is closely associated with the cap s margin form it diffuse bright rays extend north northeast for hundreds of kilometers thus the rays may consist of fringe materials that were redistributed by northward going coriolis deflected winds from 1977 to 1989 triton s full disk spectrum changed from markedly red and uv dark to nearly neutral white and uv bright this spectral change can be explained by new deposition of nitrogen frost over both the northern hemisphere and parts of a formerly redder spc frost deposition in the southern hemisphere during southern summer is possible over relatively high albedo areas of the cap stansberry et al 1990 which helps to explain the apparent stability of the unexpectedly large spc and the presence of the bright fringe

a new discrete fracture modelling approach for rock masses a method for modelling discrete fracture in rock masses under tensile and compressive stress fields is presented based on a mohr coulomb failure surface in compression and three independent anisotropic rotating crack models in tension extension fracturing is modelled by coupling the softening of the anisotropic rotating crack failure criterion to the compressive plastic strain evolution an explicitly time integrated coupled discrete element finite element approach is employed with an explicit lagrangian contact algorithm to enforce non penetration of the surfaces created when the tensile strength is depleted the geomechanical model is applied to naturally fractured rock masses which are characterised by field mapping and borehole data integrated in a stochastic 3d discrete fracture network model this approach maximises the utility of the field data and provides a direct approach to the determination of rock mass strength and deformability it also provides a realistic insight into complex failure me

thermal inertia and bolometric bond albedo values for mimas enceladus tethys dione rhea and iapetus as derived from cassini cirs measurements abstract spectra taken by cassini s composite infrared spectrometer cirs between 10 and 600 cm 1 17 1000 m of surface thermal emission of mimas enceladus tethys dione rhea and iapetus have been used to derive the thermal inertia and bolometric bond albedo values only an upper limit for the bolometric bond albedo of iapetus dark leading side could be determined due to the insensitivity of the thermal model to albedo when albedos are very low the thermal inertia in this region however is better constrained the cirs coverage of enceladus is extensive enough that the latitudinal variation in these values from 60 s to 70 n has been determined in 10 wide bins the bolometric bond albedos determined here are consistent with literature values which show the surface of the saturnian icy moons to be covered in ice contaminated to varying degrees the thermal inertia of the moons is shown to be in the range 9 20 j m 2 k 1 s 1 2 approximately 2 6 times lower than that of the galilean satellites implying a less well consolidated and more porous surface the thermal inertias of iapetus and phoebe are somewhat higher suggesting that the very low thermal inertias of satellites from rhea inwards may be related to their probable coating of e ring material latitudinal variations on the surface of enceladus show that the bolometric bond albedo and thermal inertia increase towards the active plume source at the south pole

dynamics of triton s atmosphere the recent voyager encounter established certain facts about triton s atmosphere the surface pressure is in the range 1 5 1 9 pa 15 19 bar the surface temperature is 38 3k ref 2 molecular nitrogen is the dominant atmospheric constituent hazes and clouds are visible not only on the limb but also against the surface the wind in the southern hemisphere is to the northeast at low altitudes as shown by streaks on the surface and to the west at high altitudes as shown by geyser like plume tails triton rotates with a period of 5 877 days in a right hand sense about the south pole where the season now is late spring4 here we argue that these features can be explained if triton like mars has a global well structured atmosphere in equilibrium with surface frosts the subliming frost cap produces a polar anticyclone at low altitudes with northeastward winds of 5 m s 1 within the ekman boundary layer the temperature contrast between the cold frost covered pole and the warm unfrosted equator produces westward winds at high altitudes

challenges in the characterisation of intact rock bridges in rock slopes abstract intact rock bridges have been recognised as of critical importance in the stability of rock slopes but still remain a poorly understood and challenging engineering problem both in respect to their measurement and their incorporation into design analyses the objective of this paper is not to provide conclusive answers as to the definition and measurement of rock bridges and the manner that they can be accounted for in rock slope stability analysis rather we highlight important and as yet unanswered questions to allow review of fundamental rock bridge concepts and then proceed to provide new insight into how rock bridges may be incorporated into slope stability analysis early definitions of what constitute a rock bridge are somewhat limited and the authors suggest that they could be improved by including important constraints such as block forming potential and block kinematics in this context this paper introduces an improved terminology rbij commonly used by the discrete fracture network dfn community to define rock bridge intensity relative to the sampling region in rock engineering the measurement of rock bridges is exacerbated by the fact that rock bridges are not visible unless the rock mass is exposed by human activities or by natural events such as rockfalls this constitutes a major problem for engineering design scenarios since it would not be possible to validate any assumption made with respect to extent of rock bridges without performing some form of field testing or back analysis the results of a of the finite discrete numerical analysis are presented to support our conclusions with respect to the limitations current methods used to characterise rock bridge strength the role of scale effects block theory kinematics and what we term negative rock bridges in stability analysis is discussed

the influence of thermal inertia on temperatures and frost stability on triton abstract seasonal subsurface heat conduction can have a large influence on triton s n2 frost distribution increasing surface thermal inertia reduces the thickness and extent of seasonal n2 frosts if the thermal inertia of the nonvolatile substrate is greater than about 30 of the value for nonporous h2o or co2 or if nonporous h2o or co2 is overlaid by a porous regolith of low thermal inertia but less than a few meters thick the northernmost latitudes visible to voyager should have been frost free at the time of the encounter possibly accounting for their relatively low albedo if the substrate in the northern hemisphere has sufficiently low albedo and or emissivity and also has a thermal inertia comparable to that of nonporous h2o or co2 there may be no seasonal or permanent n2 deposits in the northern hemisphere at all because this model like previous ones predicts a monotonic recession of permanent n2 deposits toward the poles and very limited seasonal n2 frost in the southern hemisphere at voyager time and because of new spectroscopic evidence for nonvolatile co2 on triton s bright southern hemisphere we consider it possible that much of the bright material on triton s southern hemisphere is not n2 bright nonvolatiles in the southern hemisphere may allow seasonal n2 frosts to form there during the southern summer possibly helping to explain triton s spectroscopic changes during the past decade all the models considered here predict 10 fold or greater seasonal variations in atmospheric pressure with pressure currently increasing in high thermal inertia models and decreasing in models with low thermal inertia

thermal evolution of kuiper belt objects with implications for cryovolcanism abstract we investigate the internal thermal evolution of kuiper belt objects kbos small radii 2500 kg m 3 bodies orbiting beyond neptune focusing on pluto s moon charon in particular our calculations are time dependent and account for differentiation we review evidence for ammonia hydrates in the ices of kbos and include their effects on the thermal evolution a key finding is that the production of the first melt at the melting point of ammonia dihydrate 176 k triggers differentiation of rock and ice the resulting structure comprises a rocky core surrounded by liquids and ice enclosed within a 100 km thick undifferentiated crust of rock and ice this structure is especially conducive to the retention of subsurface liquid and bodies the size of charon or larger radii 600 km are predicted to retain some subsurface liquid to the present day we discuss the possibility that this liquid can be brought to the surface rapidly via self propagating cracks we conclude that cryovolcanism is a viable process expected to affect the surfaces of large kbos including charon

the effect of surface roughness on triton s volatile distribution calculations of radiative equilibrium temperatures on triton9s rough surface suggest that significant condensation of n 2 may be occurring in the northern equatorial regions despite their relatively dark appearance the bright frost is not apparent in the voyager images because it tends to be concentrated in relatively unilluminated facets of the surface this patchwork of bright frost covered regions and darker bare ground may be distributed on scales smaller than that of the voyager resolution as a result the northern equatorial regions may appear relatively dark this hypothesis also accounts for the observed wind direction in the southern hemisphere because it implies that the equatorial regions are warmer than the south polar regions

thermal convection as a possible mechanism for the origin of polygonal structures on pluto s surface high resolution pictures of pluto s surface obtained by the new horizons spacecraft revealed among other surface features a large nitrogen ice glacier informally named sputnik planitia the surface of this glacier is separated into a network of polygonal cells with a wavelength of 20 40 km this network is similar to the convective patterns obtained under certain conditions by laboratory experiments suggesting that it is the surface expression of thermal convection here we investigate the surface planform obtained for different convective systems in 3d cartesian geometry with different modes of heating and rheologies we find that bottom heated systems as assumed by previous studies do not produce surface planforms consistent with the observed pattern alternatively for a certain range of rayleigh roberts number rah a volumetrically heated system produces a surface planform similar to this pattern we then combine scaling laws with values of rah within its possible range to establish relationships between the critical parameters of sputnik planitia in particular our calculations indicate that the glacier thickness and the surface heat flux are in the ranges 2 10 km and 0 1 10 mw m 2 respectively however a difficulty is to identify a proper source of internal heating we propose that the long term variations of surface temperature caused by variations in pluto s orbit over millions of year produces secular cooling equivalent to internal heating we find that this source of heating is sufficient to trigger thermal convection but additional investigations are needed to determine under which conditions it can produce surface patterns similar to those of sputnik planitia

on interfacial instability as a cause of transverse subcritical bed forms 1 recent experimental results suggest there are at least two distinct bed form initiation processes bed forms may be generated from local bed defects that are propagated down and across stream by flow separation processes when sediment transport is patchy and sporadic alternatively bed form development may occur over the whole bed at once when sediment transport is general and widespread herein we critically test a simple model for this latter bed form initiation mode that was originally presented by h k liu in 1957 but not tested because of the complex nature of the measurements required the theory is based on the idea that a moving sand bed might be likened to a dense fluid and that a hydrodynamic instability develops at the interface between the sediment transport layer and the near bed fluid leading to the organization of the transport system into laterally extended discrete bed forms our predicted initial bed form lengths are within 10 of the lengths observed in a series of flume experiments suggesting that transverse waveforms on sand beds sheared by unidirectional currents can be initiated as an interfacial hydrodynamic instability of kelvin helmholtz type when the current is sufficiently vigorous to produce general sediment movement that is to create a sediment transport layer that acts as a pseudofluid with density composed of solid and fluid components

triton s streaks as windblown dust the encounter of the voyager 2 spacecraft with neptune s satellite triton revealed many dark about 10 20 darker than the adjacent frost surface streaks in triton s southern hemisphere1 resembling the streaks that are due to windblown dust on mars2 it seems therefore that dust transport by winds in triton s tenuous atmosphere is required the main question being the mechanism for raising dust from the surface or sub surface the two obvious candidates are geyser like eruptions and direct lofting by surface winds1 here we show that despite triton s tenuous 16 3 bar atmosphere3 low cohesion grains with diameters of 5 m may be carried into suspension by aeolian surface shear stress given expected geostrophic wind speeds4 of l0ms 1 the wind velocities needed to lift grains as cohesive as those found on earth however are implausibly high for erupting plumes we show that dust settling timescales and expected wind velocities yield streak length scales in good agreement with those observed both candidate mechanisms therefore seem to be consistent with present observations of triton

photometry of triton 1992 2004 surface volatile transport and discovery of a remarkable opposition surge abstract triton the large satellite of neptune was imaged by the voyager 2 spacecraft in 1989 with dark plumes originating in its volatile rich south polar region southern summer solstice a time when seasonal volatile transport should be at a maximum occurred in 2001 ground based observations of triton s rotational light curve obtained from table mountain observatory in 2000 2004 reveal volatile transport on its surface when compared with a static frost model constructed from voyager images the light curve shows an increase in total amplitude an earlier light curve obtained in 1992 from mauna kea observatory is consistent with the static frost model this movement of volatiles on the surface agrees with recent imaging results from the hubble space telescope bauer j m buratti b j li j y mosher j a hicks m d schmidt b e goguen j d 2010 astrophys j 723 l49 l52 the changes in the light curve can be explained by the transport of nitrogen frost on the surface or by the uncovering of bedrock of less volatile methane we also find that triton exhibits a large opposition surge at solar phase angles less than 0 1 this surge cannot be entirely explained by the effects of coherent backscatter

the impact cratering record on triton impact craters on triton are scarce owing to the relatively recent resurfacing by icy melts the most heavily cratered surface has a crater density about the same as the lunar maria the transition diameter from simple to complex craters occurs at a diameter of about 11 kilometers and the depth diameter relationship is similar to that of other icy satellites when gravity is taken into account the crater size frequency distribution has a differential 3 slope cumulative 2 slope and is the same as that for the fresh crater population on miranda the most heavily cratered region is on the leading hemisphere in triton s orbit triton may have a leading trailing asymmetry in its crater population based primarily on the similarity of size distributions on triton and miranda and the relatively young surface on triton the source of triton s craters is probably comets the very peculiar size distribution of sharp craters on the cantaloupe terrain and other evidence suggests they are volcanic explosion craters

saltation threshold on earth mars and venus new formulations valid for wide ranges of particle diameter and density and gas density are presented for prediction of saltation threshold speed for small particles a low air density wind tunnel was used to extend the range of previous investigations and to separate the effects of reynolds number and interparticle forces of cohesion the new formulations are used to predict saltation threshold for atmospheric conditions on the surface of the earth mars and venus

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

implications of using broadband photometry for compositional remote sensing of icy objects water ice has such a low absorption coefficient at visual wavelengths 0 01 cm 1 that a very small amount of particulate material can significantly darken an icy surface a variety of ice plus particle mixtures were studied to show that particulate contaminations of 1 by weight even 0 1 or less in some cases in ice or frosts result in reflectance levels close to that of the contaminants in a very clear ice no bubbles it is plausible to have a reflectance 0 05 for particulate contaminations 10 7 by weight for submicron dark particles such as carbon lampblack scattering conditions compete for domination with contaminants for control of visual reflectance implying that the apparent reflectivity level and color of a surface is a poor indicator of ice content a dark surface e g albedo 0 05 does not necessarily imply that there us very little water ice present infrared jhk colors of water ice and other minerals including ice mineral mixtures show that some orthopyroxenes can have jhk colors very similar to fine grained water frosts in general it is possible that the jhk colors of an ice plus particulate mixture can fall anywhere in the classical j h versus h k diagram thus the diagram cannot be used to distinguish a predominately rock surface from one which is predominantely ice for one specific case an important exception is the case where both the j h and h k colors are 0 2 it appears that such colors indicate a relatively pure icy surface in some cases the diagram might be used as a statistical tool to distinguish between the compositions of surfaces within a class of objects but the validity of such comparisons decreases for different classes such as the main belt asteroids when compared to outer solar system satellites where water ice is more stable

pluto s climate modeled with new observational constraints abstract pluto has a nitrogen atmosphere in vapor pressure equilibrium with surface ice n 2 is mobile and is transported seasonally even at pluto s cold temperatures in the outer solar system a thermal model developed by hansen and paige in 1996 to model pluto s climate has been re deployed in response to new data and in anticipation of the new horizons flyby of pluto in 2015 a number of stellar occultations have been observed in the last 11 years as pluto has crossed the galactic plane new hubble space telescope images show a variegated surface these recent observations allow us to model pluto s climate with much tighter constraints our findings suggest that pluto s atmosphere will not collapse prior to the arrival of new horizons although pressure will be dropping as n 2 condenses on the south polar cap this finding is in contrast to the olkin et al olkin et al 2013 arxiv1309 0841o prediction that permanent volatiles in the northern hemisphere maintain pluto s atmospheric pressure throughout its orbit the range of surface pressures predicted for 2015 for nine cases with very good matches to observables is 0 3 3 2 pa the best match predicts that new horizons will detect an atmospheric pressure of 2 4 pa

numerical modeling of influence parameters in cavabililty of rock mass in block caving mines abstract the prediction of rock mass cavability is needed in the design of block caves to estimate the undercut size required to achieve continuous caving the cavability of the rock mass will control mine design and economic issues for a given geological environment and is a fundamental issue in establishing a successful block caving mine with recent interest in applying caving techniques to stronger rock masses the reliable prediction of rock mass cavability is becoming increasingly important the two most universally applied methods for cavability prediction are the empirical stability graph approach developed by laubscher and numerical methods empirical approaches developed to predict rock mass cavability have been based on the assessment of rock mass conditions using recognized rock mass classification schemes rock mass classification is the first stage in empirical approaches to predicting rock mass cavability the numerical approaches also commonly utilize rock mass classification schemes to assign rock mass properties and apply failure criteria within the models a reliable prediction of cavability of rock mass depends on the accurate identification of the influence parameters in rock mass cavability the cavability of a rock mass is based on many factors such as natural and induced factors affect the caving performance in this paper the effect of seven parameters the compressive strength of intact rock ucs joint orientation joint persistence joint density p32 joint friction confined stress and hydraulic radius hr is investigated using numerical technique named the synthetic rock mass srm the srm is a numerical modeling technique which combines the bonded particle model pfc for intact rock and discrete fracture network dfn simulation to assess the influence of each parameter in numerical modeling the value of one parameter is changing while the values of other six parameters are fixed it is found that in situ stress and hydraulic radius are the most effective parameters in cavability of rock mass in block caving mines

bed waves generated by internal waves in alluvial channels the flow in an alluvial channel is conceived as a stratified flow both with respect to the velocity and density distribution in such flows internal waves may occur which influence the generation of bed elevations this paper presents a theory that explains for low froude number flows the initiation of dunes and ripples by these waves on a flat bed the theory is demonstrated by comparing theoretical and experimental results for the case of bed load transport however an extension to the case of suspended load transport is straightforward