processes of selective grain transport and the formation of placers on beaches placers are found on many beaches of the oregon coast in the beach that is the focus of this study the principal placer minerals are ilmenite 22 0 epidote 20 0 garnet 18 7 augite 15 5 hypersthene 8 1 hornblende 5 8 and zircon 2 0 the ilmenite fraction actually being partly chromite a series of beach face sand samples was obtained along a profile when sand was being eroded from the upper beach and transported to offshore bars since the processes of grain selective sorting leading to placer formation were probably most active at such a time the landward most sample contained 96 heavy minerals being part of the placer this concentration systematically decreased offshore to a 6 heavy mineral content in the seaward most sample 54 m offshore determinations of individual heavy mineral concentrations revealed that although they all tended to become concentrated within the placer with light quartz and feldspar dominating the offshore transport the sorting processes were m

melbourne s southbank interchange a permanent excavation in compressible clay the southbank interchange of the melbourne city link project links major freeways and access roads the permanent excavation covers an area of 3 ha and extends to a maximum depth of 9 m which is 6 m below the ground water table design and construction approaches were developed to i control seepage into the excavation to limit groundwater lowering beyond the site and ii limit the effects of potentially damaging base heave during construction lateral flow of groundwater into the excavation was controlled by a cut off wall extending through the compressible clay with a surrounding line of closely spaced recharge wells analyses showed the recharge wells in combination with the wall would be effective in limiting drawdown outside the site monitoring showed that pore water pressures were maintained within the design criteria with the assistance of deep recharge of an underlying aquifer to control vertical seepage survey showed settlements outside the site were minimal shallow pressure relief drains

effect of carbon dioxide sequestration on the mechanical properties of deccan basalt carbon dioxide sequestration is considered to be an efficient method of curbing the release of carbon dioxide emissions into the atmosphere and to mitigating corresponding effects on climate change in this regard basaltic rocks are among the potential repositories due to their ability to trap carbon dioxide in form of carbonate minerals a series of laboratory scale saturation experiments was conducted on three types of basalts that were collected from different horizons of the deccan volcanic province dvp india the basalt cores were treated in a saturation chamber for different exposure periods under low pressure and room temperature conditions a set of key mechanical physical and chemical properties of the pre and post treated samples were analyzed to identify saturation related changes the results show that exposure of the basalts to carbon dioxide has a strong effect on their strength however the extent of the effect is different for different types of basalts and is strongly controlled by the exposure time the mineralogical composition and rock texture x ray diffraction and scanning electron microscopy sem show that saturation leads to dissolution of the mafic minerals and precipitation of new carbonate minerals in the cracks and vesicles of the host rock these changes in the mineralogical content and the development of micro cracks in the samples are interpreted as being the primary factors that affect the loss of integrity in the rock

co2 percolation experiment through chlorite zeolite rich sandstone pretty hill formation otway basin australia underground co2 sequestration is highly recommended as an effective means of significantly decreasing co2 concentration in the atmosphere mineral storage is the more secure technology but requires the presence of high concentration of divalent cations in the pore fluid results from co2 percolation experiments through chlorite zeolite rich sandstone samples from the pretty hill formation otway basin australia are presented the dissolution of the laumontite 7 wt and chamosite 7 wt are the potential sources of calcium iron and magnesium required for carbonate precipitation the percolation experiment was setup to reproduce at laboratory scale the in situ temperature and pressure conditions t 95 degrees c and p 10 mpa the fluid injected at constant flow rate is a rock equilibrated brine subsequently enriched in co2 up to partial pressure of 6 mpa we observe feldspars laumontite and chamosite dissolution kaolinite and silica precipitation and a noticeable sink of co2 in the sample which is attributed to the precipitation of both amorphous carbon due to the reduction of co2 and fe rich carbonate permeability decreases of about one order of magnitude due to the localization of the kaolinite precipitation in the main flow paths while porosity increases the high reactivity of this sandstone makes this reservoir a valuable target for co2 mineralization but the associated permeability decrease may limit the injection rate and the spreading of the co2 in the reservoir

the effects of selective sorting on factor analyses of heavy mineral assemblages abstract an investigation has been undertaken of the effects of selective grain sorting on the ability of factor analyses to identify source end members within heavy mineral assemblages q mode factor analysis of samples randomly collected from the beach at otter rock oregon yielded two factors one is dominated by augite hornblende and hypersthene and the second consists of garnet plus zircon these factors correspond closely to selective sorting patterns of minerals on this beach determined from a series of samples along a beach profile collected during a period of beach face erosion factor analysis of those profile samples showed that the garnet and zircon are associated with the high density opaques which tend to concentrate at the landward limit of wave run up while the lower densit augite etc are transported to the outer surf zone factor analyses were also performed on a synthetic data set which simulates the along coast mixing of mineral assemblages from four spatially distinct sources analyses involved pure mixtures of source end members mixtures where random errors were introduced to simulate counting uncertainties and mixtures of the end members where systematic changes were added to simulate the effects of local grain sorting the results indicate that sorting can significantly affect the results from factor analyses with new factors introduced and with random irregularities produced in the spatial patterns of the factors

sediment sorting and beach erosion along a coastal foreland magnetic measurements in point pelee national park ontario canada abstract in situ and laboratory based magnetic measurements were made on sand samples from the beach on the eastern side of point pelee national park ppnp in northwestern lake erie in order to examine both the composition and spatial distribution of magnetic minerals magnetic remanence measurements on bulk and particle size fractions showed that the magnetic properties were dominated by multidomain ferrimagnetic grains probably magnetite and or maghemite particle size specific measurements on different grain size fractions showed that the

shoreline changes along the rosetta nile promontory monitoring with satellite observations abstract a study to test the effectiveness of satellite data for monitoring shoreline change is reported the rapidly changing rosetta promontory of the nile delta egypt being selected as the study area landsat multispectral scanner mss image data in the near infrared 0 8 1 1 m 80 m resolution covering a 15 year period 1972 1987 at roughly 3 year intervals were compiled these were digitally overlain registered and differenced relative to the initial 1972 shoreline and composite changes erosion and accretion are mapped the area studied is one undergoing both aggradation and degradation depending on location sediment supply and man made barriers it was found that the general trend of the regional processes can be monitored with landsat imagery due to its repetitive coverage and good spectral contrast of land and sea improved satellite imagery with higher resolution should be a valuable tool for complementing traditional shoreline monitoring surveys in easily eroded lowlying areas such as the nile delta

late quaternary evolution of the burullus lagoon region north central nile delta egypt abstract the evolution of late quaternary stratigraphic sequences in the burullus lagoon region of the north central nile delta egypt is determined by petrological analysis of radiocarbon dated sediment borings shallow marine lagoonal and fluvial deposits accumulated during the late pleistocene and delta plain to coastal facies during the holocene since about 7500 yrs b p the latter sequence is characterized primarily by an irregular succession of delta plain deposits i e distributary channel fill marsh and lagoon complete coarsening upward sequences formed by prodelta to coastal units and previously defined in the northeastern nile delta are not observed in this region long term sediment accumulation rates for holocene facies during the build up of the delta range from about 100 to 300 cm 1000 yrs the location and ages of three nile distributary channel systems are recognized by means of cores from east to west sebennitic saitic and bolbitine rosetta the mouth of the sebennitic which is oldest of the three was located on what is now the inner to middle shelf this would explain the absence of prodelta and delta front sequences and a presence of a belt of medium to coarse grained sands extending seaward of the coast the distribution in time and space of the holocene facies is interpreted in terms of the interplay of factors controlling sedimentation i e eustatic sea level oscillations climatic changes and land subsidence minor in this region 0 04 cm yr of the three sea level changes dominate paleogeographic maps show through a series of time slices the changing configuration of this region during the past 30 000 years maps indicate the shifting channel systems and the major displacement of associated marshes and lagoons this study suggests that without the emplacement of coastal protection barriers and containment structures an expansion of burullus lagoon may be expected in the near future

spatial variations in heavy minerals and patterns of sediment sorting along the nile delta egypt abstract sand samples were collected along 34 beach profiles spanning the 240 km length of the nile delta in order to examine the sorting patterns of heavy minerals that develop during cross shore and alongshore sediment transport factor analysis of the heavy mineral contents shows that two mineral factors or groups result from sorting due to the contrasting densities and sizes of the grains one factor is dominated by augite hornblende and epidote while the second factor consists of opaques garnet zircon rutile and monazite minerals of factor 1 are of lower densities and coarser sizes and represent the grains that are selectively entrained by waves and currents in areas of beach erosion and preferentially transported to zones of beach accretion where they are deposited the higher density minerals of factor 2 tend to become concentrated in areas of beach erosion accounting for the formation of black sand placers where the erosion has been greatest the spatial distributions of these two factors reflect the grain sorting patterns of the heavy minerals which coincide with the general trends of shoreline erosion versus accretion that exist along the length of the delta there is also a distinctive pattern of cross shore sorting with factor 2 containing the denser minerals being best developed within the inner surf zone generally with a maximum at the shoreline its development corresponds to the formation of black sand concentrates on the beach face where erosion has been greatest implying that grain sorting has taken place mainly within the swash zone there is a general decrease in factor 2 relative to factor 1 toward the offshore often with oscillations that are congruent with the beach topography factor 1 with the lower density minerals is greatest over offshore bars where deposition has prevailed

evaluation of the impact of co2 co contaminant gas aqueous fluid and reservoir rock interactions on the geologic sequestration of co2 lowering the costs of front end processes e g separation in the geologic sequestration of co2 can dramatically lower the overall costs one possible approach is to sequester less pure co2 waste streams that are less expensive or require less energy to separate from flue gas or a coal gasification process etc the objective of this research is to evaluate the impacts of co2 itself as well as an impure co2 waste stream on geologic sequestration using reaction progress models reactive transport simulators and analogous reactive transport experiments run in a plug flow reactor specifically we are investigating the potential for co injecting the sox nox and h2s present in coal fired waste streams along with the co2 we present here the results of reactive transport simulations made to investigate the long term impact of dissolved co2 h2s and so2 on carbon sequestration in the frio fm tx the results suggest that addition of relatively large amounts of h2s to a co2 injection should not adversely impact injectivity or sequestration compared to the injection of co2 alone the co injection of so2 however could produce significantly different results if conditions are such that so2 can oxidize to sulfate in the long term the simulations suggest that carbonate mineral formation can sequester a significant fraction of the injected carbon through the formation of calcite magnesite and dawsonite

long term shoreline changes and the concentration of heavy minerals in beach sands of the nile delta egypt abstract analyses have been undertaken of shoreline positions established from beach profile surveys at 65 positions along the coastline of the nile delta spanning the years 1971 to 1990 the analyses identify long term linear trends as well as any cycles in the horizontal movement of shoreline positions the results reveal longshore patterns wherein erosion along a stretch of coast gives way to accretion in an adjacent stretch defining a subcell within the overall littoral system of the delta the rate of shoreline retreat has been greatest along the rosetta promontory 106 m yr and damietta promontory 10 4 m yr significant erosion has also occurred along the central bulge of the delta coast but at a lesser rate 6 5 m yr areas of accretion exist within the saddles or embayments between the promontories with the maximum shoreline advance averaging about 13 m yr the identified patterns of erosion versus accretion along the delta reflect the natural processes of wave induced longshore currents and sediment transport associated with this longshore sediment movement is a selective transport of different minerals according to their densities and grain sizes with the light minerals quartz and feldspar having the highest advection rates and the dense opaque minerals the lowest rates tending to remain behind as a lag within the erosion areas as a result of this longshore grain sorting paralleling the patterns of shoreline erosion versus accretion there are correlations between the rates of shoreline change and the heavy mineral contents and mean grain sizes of the beach sediments these large scale delta wide patterns are affected somewhat by local shoreline changes and mineral variations induced by the construction of jetties or shoreline protection structures

magnetic mineral transport and sorting in the swash zone northern lake erie canada a combined field and laboratory study in northern lake erie has provided new insights into the origin and dynamics of heavy mineral placer deposits on beaches consisting primarily of non magnetic sediment work was conducted on the cross shore and longshore transport of heavy magnetic minerals using magnetic susceptibility and fluorescent paints to trace the movement in the field of samples of magnetic magnetite and non magnetic quartz and calcite grains respectively laboratory experiments examined how the burial of small dense magnetic minerals is affected by the grain size of the non magnetic host material and how grain burial affects magnetic susceptibility measurements at the surface the field experiments demonstrated that the magnetic mineral tracers were buried rapidly beneath coarser non magnetic grains under low to moderate wave conditions and subsequently were unable to move in the longshore or cross shore directions the laboratory experiments showed that the magnetic susceptibility rapidly decreased with the rate and depth of burial of the magnetic minerals and that magnetic grain burial was most effective beneath coarser rather than finer non magnetic sand and for the latter sediments under less rather than more energetic conditions the results imply that magnetic mineral concentrations develop in this area through magnetic grain burial under fairly mild conditions and subsequent settling exposure and concentration in the upper swash zone during more energetic periods when the non magnetic grains are eroded it is probably during these erosional periods when the magnetic minerals are exposed in fairly homogeneous deposits that longshore and cross shore transport takes place

determining effective wellbore permeability from a field pressure test a numerical analysis of detection limits we propose a simple pressure test that can be used in the field to determine the effective permeability of existing wellbores such tests are motivated by the need to understand and quantify leakage risks associated with geological storage of co2 in mature sedimentary basins if co2 is injected into a deep geological formation and the resulting co2 plume encounters a wellbore leakage may occur through various pathways in the disturbed zone surrounding the well casing the effective permeability of this composite zone on the outside of the well casing is an important parameter for models of leakage however the data that exist on this key parameter do not exist in the open literature and therefore specific field tests need to be done in order to reduce the uncertainty inherent in the leakage estimates the test designed and analyzed herein is designed to measure effective wellbore permeability within a low permeability caprock bounded above and below by permeable reservoirs by pressurizing the reservoir below and measuring the response in the reservoir above alternatively a modified test can be performed within the caprock without directly contacting the reservoirs above and below we use numerical simulation to relate pressure response to effective well permeability and then evaluate the range of detection of the effective permeability based on instrument measurement error and limits on fracture pressure these results can guide field experiments associated with site characterization and leakage analysis

patterns of beach sand sorting and shoreline erosion on the nile delta abstract rapid erosion has occurred on the beaches of the nile delta in response to dam construction that has cut off the river sediment supply this erosion is greatest adjacent to the two distributary mouths with shoreline retreat rates up to 60 m per year the eroded sand is carried alongshore away from the river mouths and deposited in areas of shoreline accretion these patterns of shoreline erosion and deposition are reflected in the mineralogy of the beach sands on a delta wide scale high density opaques garnet and zircon are concentrated in the erosion areas to form black sand placers lower density hornblende as well as quartz and feldspars are preferentially transported out of the erosion areas and deposited in the stretches of accreting shoreline a detailed analysis of these sorting patterns has been undertaken with beach samples from abu quir bay at the western end of the delta concentrations of opaques zircon rutile and garnet decrease exponentially with longshore distance from the river mouth while augite and hornblende increase exponentially the coefficients in the exponential equations are found to be a function of mineral density demonstrating the importance of this grain property in mineral sorting leading to the observed compositional variations along the shores of the nile delta

geochemical monitoring for potential environmental impacts of geologic sequestration of co2 carbon dioxide sequestration is now considered an important component of the portfolio of options for reducing greenhouse gas emissions to stabilize their atmospheric levels at values that would limit global temperature increases to the target of 2 c by the end of the century pacala and socolow 2004 ipcc 2005 2007 benson and cook 2005 benson and cole 2008 iea 2012 romanak et al 2013 increased anthropogenic emissions of co2 have raised its atmospheric concentrations from about 280 ppmv during pre industrial times to 400 ppmv today and based on several defined scenarios co2 concentrations are projected to increase to values as high as 1100 ppmv by 2100 white et al 2003 ipcc 2005 2007 eia 2012 global ccs institute 2012 an atmospheric co2 concentration of 450 ppmv is generally the accepted level that is needed to limit global temperature increases to the target of 2 c by the end of the century this temperature limit likely would moderate the adverse effects related to climate change that could include sea level rise from the melting of alpine glaciers and continental ice sheets and from the ocean warming increased frequency and intensity of wildfires floods droughts and tropical storms and changes in the amount timing and distribution of rain snow and runoff ipcc 2007 sundquist et al 2009 iea 2012 rising atmospheric co2 concentrations are also increasing the amount of co2 dissolved in ocean water lowering its ph from 8 1 to 8 0 with potentially disruptive effects on coral reefs plankton and marine ecosystems adams and caldeira 2008 schrag 2009 sundquist et al 2009 sedimentary basins in general and deep saline aquifers in particular are being investigated as possible repositories for the large volumes of

relative stability and significance of dawsonite and aluminum minerals in geologic carbon sequestration 1 computer simulations predict dawsonite naalco3 oh 2 will provide long term mineral sequestration of anthropogenic co2 whereas dawsonite rarely occurs in nature or in laboratory experiments that emulate a carbon repository resolving this discrepancy is important to determining the significance of dawsonite mineralization to the long term security of geologic carbon sequestration this study is an equilibrium based experimental and modeling evaluation of underlying causes for inconsistencies between predicted and observed dawsonite stability using established hydrothermal methods 0 05 molal nahco3 aqueous solution and synthetic dawsonite were reacted for 18 7 days 449 2 hours at 50 c 20 mpa temperature was increased to 75 c and the experiment continued for an additional 12 3 days 295 1 hours incongruent dissolution yielded a dawsonite gibbsite nordstrandite assemblage geochemical simulations using geochemist s workbench and the resident database thermo com v8 r6 incorrectly predicted a dawsonite diaspore assemblage and underestimated dissolved aluminum by roughly 100 times higher aqueous aluminum concentrations in the experiment suggest that dawsonite or diaspore is less stable than predicted simulations employing an alternate database thermo dat correctly predict dawsonite and dawsonite gibbsite assemblages at 50 and 75 c respectively although dissolved aluminum concentrations are still two to three times lower than experimentally measured values correctly reproducing dawsonite solubility in standard geochemical simulations requires an as yet undeveloped internally consistent thermodynamic database among dawsonite gibbsite boehmite diaspore aqueous aluminum complexes and other al phases such as albite and kaolinite these discrepancies question the ability of performance assessment models to correctly predict dawsonite mineralization in a sequestration site

spatial patterns of diagenesis during geothermal circulation in carbonate platforms geothermal convection of seawater deep in carbonate platforms could provide the necessary supply of magnesium for dolomitization at temperatures high enough to overcome kinetic limitations we used reactive transport simulations to predict the rates and spatial patterns of dolomitization during geothermal convection in a platform that was 40 km across and 2 km thick in the simulations porosity and permeability decrease with depth to account for sediment compaction dolomitization of a platform consisting of medium grained 0 0 5 mm sediments occurred in a broad band ranging from 2 5 km depth near the margin to 1 5 km depth near the platform center the area of dolomitization is deep enough that temperatures exceed 50 c but not so deep that low permeabilities restrict mass transport complete dolomitization in the center of this zone is estimated to require at least 60 my incorporation of permeability contrasts permeable beds and reactive beds focused dolomitization strongly and reduced the estimated time required for dolomitization by as much as 50 percent dolomitization created magnesium depleted calcium rich fluids in less than 10 ky and results support a link between dolomitization and anhydrite precipitation where adequate sulfate is available

numerical simulation of porosity and permeability evolution of mount simon sandstone under geological carbon sequestration conditions abstract a numerical model was developed with the use of reactive transport code crunchflow to estimate porosity permeability and mineral composition changes of mount simon sandstone under typical geological carbon sequestration conditions p 23 8 mpa and t 85 c the model predicted a permeability decrease from 1 60 md to 1 02 md for the mount simon sandstone sample in a static batch reactor after 180 days of exposure to co 2 saturated brine which is consistent with measured permeability results model predicted solution chemistry results were also consistent with laboratory measured solution chemistry data sio 2 am was the primary mineral that causes permeability decrease followed by kaolinite both sio 2 am formation and kaolinite formation were attributed to the dissolution of quartz and feldspar this study shows that the formation of sio 2 am and kaolinite in the pore space of host rock is possible under typical co 2 sequestration conditions sio 2 am and kaolinite precipitation at the co 2 plume extent could reduce the permeability of host rock and improve lateral containment of free phase co 2 contributing to overall security of co 2 storage

initiation and failure mechanism of base instability of excavations in clay triggered by hydraulic uplift excavations in clay overlying an aquifer may cause catastrophic basal failure due to hydraulic uplift although case histories with hydraulic uplift failures are reported worldwide from time to time the initiation and failure mechanism of the base instability are not well studied and understood to address these two issues dimensional analysis is firstly conducted to propose dimensionless groups dgs possibly relevant to this subject effects of these dgs on the initiation and failure mechanism of base instability are then investigated by carrying out a series of finite element analyses in which constitutive models and model parameters have been previously validated against centrifuge test results it is revealed that the initiation and failure mechanism of base instability due to hydraulic uplift is mainly governed by a ratio of excavation width over the thickness of soft clay inside excavation b d as excavation becomes narrower i e b d decreases the hydraulic pressure pi required to initi

influence of reaction kinetics and mesh refinement on the numerical modelling of concrete clay interactions large quantities of cements and concretes need to be incorporated in geological disposal facilities for long lived radwaste an alkaline plume diffusing from an aged concrete ph 12 5 through argillite type rocks has been modelled considering feedback of porosity value variations on transport properties using the reactive transport code toughreact the mineralogical composition of the argillite is modified at the interface with the concrete diffusion of cementitious elements leads to rapid and strong porosity occlusion in the argillite numerical results show that both reaction rates and spatial refinement affect mineralogical transformation pathways the variations in porosity and the extension of the zone affected by the alkaline perturbation are compared at different times the major effects of mineral precipitation under kinetic constraints rather than local equilibrium are a delay in the porosity clogging and an increase in the extension of the alkaline perturbation in the clay formation the same time delay rise for the porosity occlusion also appears for the roughest spatial resolutions a simulation as representative as possible of temporal and spatial scales of cementation processes must then be supported by more comparative data such as long term experimental investigations or natural analogues

integration of bed characteristics geochemical tracers current measurements and numerical modeling for assessing the provenance of beach sand in the san francisco bay coastal system abstract over 150 million m3 of sand sized sediment has disappeared from the central region of the san francisco bay coastal system during the last half century this enormous loss may reflect numerous anthropogenic influences such as watershed damming bay fill development aggregate mining and dredging the reduction in bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches wetlands and submarine environments a unique multi faceted provenance study was performed to definitively establish the primary sources sinks and transport pathways of beach sized sand in the region thereby identifying the activities and processes that directly limit supply to the outer coast this integrative program is based on comprehensive surficial sediment sampling of the san francisco bay coastal system including the seabed bay floor area beaches adjacent rock units and major drainages analyses of sample morphometrics and biological composition e g foraminifera were then integrated with a suite of tracers including 87sr 86sr and 143nd 144nd isotopes rare earth elements semi quantitative x ray diffraction mineralogy and heavy minerals and with process based numerical modeling in situ current measurements and bedform asymmetry to robustly determine the provenance of beach sized sand in the region

computer simulation of co2 trapped through mineral precipitation in the rose run sandstone ohio abstract equilibrium path of reaction and kinetic modeling of co2 brine mineral reactions in the rose run sandstone one of ohio s deep saline aquifers was conducted in order to investigate the factors that are likely to influence the capacity of this formation to trap injected co2 as solid carbonate mineral phases equilibrium modeling was applied to investigate the impact of temperature pressure mineralogy brine composition and co2 fugacity on mineral dissolution and precipitation the amount of co2 sequestered and the form of sequestration path of reaction and kinetic modeling were used to evaluate intermediate products and reaction progress as a function of time as well as to investigate the impact of brine to rock ratio the results of equilibrium modeling demonstrate that dissolution of albite k feldspar and glauconite and the precipitation of dawsonite and siderite are potentially very important for mineral trapping of co2 according to the path of reaction and kinetic modelling the stability of carbonate rocks is controlled by the brine to rock ratio the ph of the system the fugacity of co2 and the kinetic rate of dissolution in kinetic modeling with a brine to rock ratio of 1 25 reactive surface area of 10 cm2 g 10 mpa f co 2 and 12 porosity 1 5 2 g of co2 per kg of reacted rock significant quantities 10 40 g of carbonate minerals were precipitated from both the sandstone and mixed rock assemblages the rose run sandstone has the potential to store co2 over millennia as a negatively buoyant aqueous solution and ultimately as immobile carbonate minerals

groundwater control around a large basement melbourne s crown casino was constructed on a site bordering the yarra river and underlain by problem soils of the coode island silt formation the development needed to provide two levels of basement car park over the entire site an innovative approach to groundwater control around the excavation was required to avoid depressurisation of adjoining soils leading to settlements analysis showed a conventional bentonite cut off wall would still allow depressurisation by lateral flow through the coode island silt during the construction period the high cost and construction difficulty of a very low permeability wall mitigated against it an hydraulic wall was proposed in conjunction with a conventional cut off wall this comprised a curtain of wick drains surrounding the cut off wall and charged with water control of seepage through an underlying aquifer by a cut off wall was considered but a more cost effective method using recharge by wells was adopted when shown necessary monitoring of groundwater p

surface settlements at a soft soil site due to bedrock dewatering abstract construction of a 16 m deep 55 m wide almost square underground structure through 8 m of soft soils and 8 m of sandstone and siltstone led to the development of widespread settlements the affected area extended to distances of over 200 m from the perimeter of the structure the floor slab of the underground structure was not designed for water pressure thus operation of the structure requires continuous pumping of seepage water collected at a sump located at the lowermost elevation within the structure subsurface investigation and monitoring data obtained over 5 75 year period following the construction of the structure indicated that the settlement resulted from consolidation of soft soils due to depressurization of an aquifer within the underlying bedrock caused by continuous dewatering needed for the operation of the structure an analytical study was undertaken to project the long term settlement a simple analytical model could be used to simulate the complex hydrogeological problem reasonably the details of hydrogeologic setting subsurface investigation and monitoring activities and the analytical model for projecting long term settlements are presented in this paper

climate and induced changes in relation to shoreline migration trends at the nile delta promontories egypt abstract an analysis of changing shoreline positions has been conducted for the rosetta and damietta nile promontories the analysis was based on several shoreline positions over the 19th and 20th centuries the shoreline positions were determined from ground surveys maps and aerial and satellite photos generally the analysis reveals two remarkable shoreline migration trends prograding shorelines during the 19th century and a more recent retrograding shoreline trend during the 20th century a relationship exists between shoreline changes nile hydrology and rainfall indicators which indicates that the change from progradation to retrogression was partly controlled by the annual fluctuation of high or low nile floods in early historical times because of climatic changes precipitation and partly by human induced changes differences in precipitation patterns in east africa altered the hydrology of the nile including the sediment load the water level and discharge a remarkable difference occurred in the nile hydrology around 1900 the prograding shoreline trends coincided with higher nile floods during the 19th century the retrograding shorelines with low floods during the 20th century

patterns of nearshore sediment transport along the nile delta egypt abstract the nearshore sediment transport system along the nile delta has been determined from the response of beaches to the construction of engineering structures from the forms of geomorphological shoreline features from large scale changes in shoreline orientations due to erosion and accretion and from longshore variations in beach sand mineralogy and grain sizes the analyses reveal local patterns of erosion and accretion that have resulted from the interruption of the longshore sediment transport by jetties and groins as well as the major erosion of the promontories adjacent to the mouths of the rosetta and damietta branches of the nile river brought about by the cutoff of the supply of river sand by construction of the high aswan dam major zones of shoreline accretion are positioned to the east of the eroding promontories demonstrating that there are strong longshore gradients in the quantities of the eastward sand transport the variation east of the rosetta branch has been quantitatively evaluated from the patterns of erosion and accretion based on sediment continuity considerations a similar delta wide comparison is made between the patterns of longshore sediment movements found in this study and those calculated by others from wave refraction diagrams based on the various lines of evidence for beach erosion longshore sediment transport and shoreline accretion four nearly self contained cells have been identified in the littoral zone of the nile delta abu quir bay the eastern flanks of the rosetta and damietta promontories and the burullus central delta region