predicting the crest height of a gravel beach the beach crest is a common morphological feature formed by the deposition of sediment carried up slope by wave swash the elevation to which waves can pile gravel is a function of the size and density of the material relative to the hydraulic components of swash velocity wave frequency and runup height two equations 17 and 21 that predict the height of the beach crest to the wave forces and the beach material are derived the first derivation compares the wave force acting to move a stone up the beach face with a weight force acting to hold the stone in place the second derivation relates the potential energy per unit area of the beach crest to the total wave energy that lifted and deposited the material above a given sea level datum as a test of the derived equations the actual crest height of one natural gravel beach was accurately estimated by both equations derived further research and testing on other natural beaches are needed to fully verify eqs 17 and 21 a comparison of other equations eqs 2 3 and 4 that predict crest height is also made the poor fit of the other equations are a result of using values for the coefficients that were established in wave tank experiments another shortcoming of eqs 3 and 4 is that they do not include variables related to the beach material hence they predict that all particle sizes from sand to boulders would be piled to the same elevation by the same wave forcing eq 2 includes a particle size variable but predicts increasingly higher beach crests for larger particles more realistic results for all three equations eqs 2 3 and 4 would be expected with field tested values for the coefficients but a range in values for each different beach would be necessary the advantage of eqs 17 and 21 is that equations are not dependent on coefficients whose values come from correlation with other data sets

the origin and implications of variations in soil related properties within macrotermes falciger mounds the differing properties of termite mound material compared to the surrounding soils are well documented far less is known about their variability within the mounds themselves detailed sampling and physico chemical analysis of four large macrotermes mounds around lubumbashi d r congo revealed soil related properties are far from uniform within the mounds the total variability is highest perpendicular to the mound s surface based on mound morphology and variations in soil related properties four zones can be distinguished within the mounds i the outer mantle characterized by intense varied biological activity and by a well developed soil structure ii the active nest and chimney found at the top with the nest area as a site of organic matter mineralization iii the accumulation zone located in the lower central part of the mound where compounds derived from the nest area are concentrated and iv a transition zone situated between the outer mantle and the other zones intermittent leaching plays a key role in the development of this zoning the steep and smooth surface of the mound and the fine texture of the mound material limit the amount of percolating water in the rainy season as a mound grows larger this amount is no longer sufficient to leach mobile compounds to below ground level at this stage of mound development they accumulate in the lower central part of the structure in view of their large size and high spatial density a considerable part of the total nutrient stock of the ecosystem is likely contained within these large mounds

a pragmatic approach to rock toe stability abstract a new stability formula is proposed for the toe protection of rubble mound structures the new approach is based on a critical stability number that refers to the initial movement of armour stones on the toe berm damage progression is subsequently described by the ratio of actual and critical stability numbers the ratio of toe berm submergence and incoming wave height has been identified as the governing parameter for the toe stability other parameters including sea bed gradient wave steepness and toe berm geometry were found to be of minor importance the new toe stability formula has been validated against model test results and has been compared with the widely used formula of van der meer 1998 the new approach appears more accurate and more physically meaningful the practical application of the new formula for toe berm design is briefly described

stone mobility and longshore transport at reshaping breakwaters abstract physical model tests have been performed in two different wave flumes to analyse the threshold of stone movement and quantify the frequency and length of displacements due to head on wave attacks at a reshaping breakwater data on stone movements were obtained from the observation of cumulative displacements at the end of each wave attack and from video records during the attack threshold conditions frequency of movement and displacement length are expressed as function of a suitably modified stability number a simple model is defined relating longshore transport due to oblique wave attack to stone mobility the transport model is based on the assumption that movement statistics is affected by obliquity only through the appropriate mobility index and that stones move during up and down rush in the direction of incident and reflected waves without any calibration results compare favourably with experimental data available in literature in the range of low mobility conditions where movement statistics was observed a calibration is provided in order to obtain an accurate transport formula valid in a wide mobility range i e for reshaping breakwaters and up to gravel beaches

hydraulic stability of nominal and sacrificial toe berms for mound breakwaters on steep sea bottoms abstract when mound breakwaters are placed on steep sea bottoms in combination with very shallow waters the design of the toe berm becomes a relevant issue toe berms built close to the water surface on a steep sea bottom must withstand such high wave loads that their design may not be feasible with available quarrystones in this study a new design method was developed to reduce the rock size by increasing the toe berm width the analysis involved specific 2d small scale tests with toe berms of different rock sizes and widths placed on a m 1 10 bottom slope with the water surface close to the toe berm crest two new concepts were introduced to better characterize damage to wide toe berms 1 the most shoreward toe berm area which effectively supports the armor layer in this study referred to as the primary or nominal toe berm and 2 the most seaward toe berm area which serves to protect the nominal toe berm in this study called the secondary or the sacrificial toe berm damage to the nominal toe berm was used to describe hydraulic stability of wider toe berms given a standard toe berm of three rocks wide nominal toe berm an equivalent toe berm with damage similar to the nominal toe berm was defined by increasing the berm width and decreasing the rock size the reduction in rock size showed an inverse 0 4 power relation with the relative berm width

singular points at berm breakwaters scale effects rear round head and longshore transport abstract design aspects other than the profile development of the seaward side have been investigated in this paper aspects such as scale effects rear stability round head design and longshore transport have been treated here based on extensive test series on two different berm breakwater designs a first conclusion is that scale effects were not present in a 1 35 scale model compared with a 1 7 large scale model with wave heights up to 1 7 m a first design rule was assessed on the relationship between damage at the rear of a berm breakwater and the crest height wave height wave steepness and rock size tests on a berm breakwater head showed that enlarging the berm height at the crest and therefore the amount of rock in the berm was effective with regard to stability finally the onset of longshore transport due to oblique wave attack was studied and compared with literature formulae were derived for this onset of transport and also for the range of more serious transport up to longshore transport of coarse gravel

stability of the seaward slope of berm breakwaters abstract an extensive research on stability of statically and dynamically stable rock slopes and gravel beaches was reanalysed and focussed on berm breakwaters berm breakwaters are initially dynamically stable under severe wave attack but become more or less statically stable after reshaping the effects on the seaward profile of wave height period storm duration spectral shape initial slope rock size rock shape and grading water depth and angle of wave attack are described in a qualitative way relationships between these variables and the profile parameters are described leading to a computer program this program was verified with independent data of berm breakwaters from various international institutes the program showed to give a good prediction of the behaviour of the seaward slope of berm breakwaters and can therefore be used as a conceptual design tool

suction removal of sediment from between armor blocks iii breaking waves abstractwhen a sediment beach covered by stones or an armor layer is exposed to breaking waves the turbulence generated by the breaking waves can cause mobilization and removal of the sediment underneath the stones in two earlier studies by the technical university of denmark dtu group the suction removal of sediments from between armor blocks has dealt with the case of steady current and nonbreaking waves the present study is an extension of these studies and the results will be presented in a similar way the critical conditions for removal of sediment are determined it is found that the onset of removal of sediment is governed by three parameters 1 the sediment mobility based on the sediment size wave height and wave period 2 the ratio between the sediment size and the stone size d d and 3 surf similarity parameter tan h0 l0 0 5 the variation of the critical mobility number for removal of sediment as function of d d and is determined for the range 0 001 d d 1 0 and 0 15

the age of large termite mounds radiocarbon dating of macrotermes falciger mounds of the miombo woodland of katanga dr congo abstract the age of four large termite mounds has been determined by 14c dating the acid insoluble organic carbon fraction of samples taken along the central vertical axis of two active and two abandoned mounds the age sequence in the active mounds is erratic but the results for the abandoned mounds show a logical increase of 14c age with depth the ages measured at 50 cm above ground level were 2335 2119 cal yr bp for the large abandoned mound 630 cm high and 796 684 cal yr bp for the small abandoned mound 320 cm high cold water extractable organic carbon cweoc measurements combined with spectroscopic analysis revealed that the lower parts of the active mounds may have been contaminated with recent carbon that leached from the active nest nonetheless this method appears to provide reliable age estimates of large abandoned termite mounds which are older than previously estimated furthermore historical mound growth rates seem to correspond to past temperature changes suggesting a relation between past environmental conditions and mound occupancy

a new formula for front slope recession of berm breakwaters the front slope stability of breakwaters with a homogeneous berm was studied in a large number of two dimensional model tests at aalborg university denmark the results are presented together with a new formula for prediction of the berm recession which is the most important parameter for describing the reshaping the formula has also been calibrated and validated against model test data from other researchers the significance of the new design formula is that it predicts berm recession much better than the existing methods especially in case of more stable structures

empirical model for probabilistic rock stability on flat beds under waves with or without currents abstract an empirical formula was developed for predicting the stability of isolated quarry rocks on relatively flat beds under waves with or without current in terms of the damage ratio the damage ratio was examined using 100 crushed stones median mass m50 293 g and mass density s 2 62 g cm3 as scale models of quarry rocks and replicas with a lower density s 1 38 g cm3 by placing them on beds of different roughness in a wave flume not only under periodic waves with periods of 2 3 5 s but also in symmetric and asymmetric oscillatory flows periods 8 12 s simulating waves without and with current in a circulating water channel comparison between hydrodynamic forces expressed in terms of three non dimensional mobility indices the maximum velocity maximum semi velocity amplitude ua and maximum acceleration relative to the friction force expressed in terms of the median coefficient of friction suggested that the damage ratio was most closely related to the ua based mobility index 2 nevertheless significant differences remained between data from the wave flume and circulating water channel tests the variation in the damage ratio which included the effects of the oscillatory velocity asymmetry oscillation period superimposed steady current mass density of stones and bottom friction was reasonably well described via the product of 2 and a function of a keulegan carpenter number the results of the field tests on quarry rocks with m50 2 04 t placed on a thin sand layer overlaying hard substrate show that the minimum stable mass is consistent with the prediction

extended characterization of damage in rubble mound scour protections abstract the analysis of damage in rubble mound scour protections is crucial for the armour stability assessment former methodologies focused on the analysis of the maximum damage number this work introduces a complementary methodology to determine and characterize damage statistical distribution based on a flexible arrangement of sub areas the sub areas are overlapping and can be varied in size allowing a refined damage analysis to capture the variation of damage with changing sub area layout the methodology is coupled with a statistical evaluation of damage numbers which is enabled by the definition of a grid ratio between armour stone size and sub area size dn50 2 asub the methodology is applied to high resolution bathymetric surveys from two stability tests of large scale rip rap scour protection around a monopile foundation and combined wave and current loading results show that the methodology provides a complementary understanding of damage distribution to the maximum damage acquired from previous methodologies in addition it allows a comparison of damage characteristics between tests despite different shapes of the foundation research concludes that the size of the sub areas influences significantly the damage description characteristic measures as the maximum damage number and standard deviation become stable at a grid ratio dn50 2 asub equal to 1 4

effects of gradation on the long shore transport processes and reshaping of rubble mound breakwaters under construction exposed to head on and oblique waves abstract breakwaters under construction are prone to undesired reshaping because their core is not designed to withstand severe or moderate wave loads while the reshaping of a finished breakwater was subject of comprehensive research few studies dealt specifically with the reshaping mechanisms of a breakwater under construction i e of the breakwater core this paper presents a set of experimental tests focused on the reshaping of rubble mound breakwater trunks and roundheads undergone during the construction phase the study accounts for oblique wave attacks and grading of the construction material better insights on how and how far such reshaping takes place are derived in the perspective of providing coastal designers and constructors with valuable information for optimising the selection of the fractions and volumes of the construction materials and for taking into account potential damages within the construction schedule and therefore additional costs

clay composition and properties in termite mounds of the lubumbashi area d r congo article i nfo the influence of macrotermes falciger activity on clays sesquioxides and water dispersible clay wdc con tent was investigated by a physico chemical mineralogical and micromorphological study of termite mound and control soil profiles at various sites near lubumbashi se katanga d r congo x ray diffraction reveals that the termite mound materials are enriched in 2 1 clays especially mica and expandable clay min erals and selective dissolution analyses show that they contain greater relative amounts of mn oxides and poorly crystalline fe oxides relative to the surrounding ferralsols the water dispersible clay wdc content is much higher 4 87 fold in epigeal mound parts than in the control soils enrichment in 2 1 clays of the mounds is attributed to upward transport of mica and smectite as part of soil aggregates or saprolite mate rials used in mound construction the difference in nature and abundance of sesquioxides between termite mound and control soil is related to a difference in moisture regime whereby the basal part of the mounds are characterized by conditions with alternating reducing oxidizing conditions in contrast to the surround ing well drained ferralitic soils the much greater degree of clay dispersibility in termite mound materials than in the surrounding soils is mainly due to differences in clay properties primarily surface charge charac teristics and to differences in fe oxide content and mode of occurrence the high water dispersible clay con tent of termite mound materials is confirmed by micromorphological features including abundant clay coatings and fragments of coatings

the modelling of wave action on and in coastal structures description of the wave action on and in coastal structures can lead to a prediction of flow properties and forces on elements of those structures for permeable structures several aspects concerning the interaction between the external flow and the internal flow have to be described accurately to predict for instance velocities and run up levels the p c model odiflocs developed at delft university of technology within the framework of the european mast coastal structures project describes the wave motion on and in several types of structures this structure can be an impermeable or a permeable structure for instance dikes breakwaters and submerged structures can be dealt with the model is a one dimensional model based on long wave equations the program takes various phenomena into account such as reflection permeability infiltration seepage overtopping varying roughness along the slope linear and non linear porous friction darcy and turbulent friction added mass internal set up and the disconnection of the free surface and the phreatic surface satisfactory results were obtained with modelling of run up surface elevations and velocities other applications show more possibilities of the model

influence of toe berm geometry on stability of reshaping berm breakwaters reshaping berm breakwaters have been mainly designed and built for water depth less than 20 m in such conditions a toe structure may be needed to reduce bottom settlements and increase geotechnical stability in the loose subsoil condition also a toe berm can be deployed to reduce the berm recession and increase the stability of the reshaping berm breakwater especially in deep water although many studies have been conducted to study the effects of toe berms on stability of conventional breakwaters investigations on the influence of a toe berm on stability of reshaping berm breakwaters are rare this paper presents results of an experimental work that has been carried out to investigate the influence of a toe berm on the hydraulic stability of reshaping berm breakwaters in a 2d physical test setup in a wave flume a total of 207 tests were conducted to systematically examine the effects of toe berm configuration on the reshaping of berm breakwaters with three types of armor stones the experimental program covers the influence of different geometrical parameters of the toe berm on the berm recession under various sea state conditions comparing results of berm recession of the cases having a toe structure with the cases without a toe berm shows that the amount of berm recession with toe berm is considerably less than the analogous amount for without toe structure it is observed that an increasing toe berm width and thickness both have considerable influence on recession reduction however the toe depth has a relatively larger influence on recession than the toe width and the influence is larger for higher stability numbers it is concluded that a toe berm in front of reshaping berm breakwater not only does have influence on recession due to the depth influence and the changing wave conditions but also the toe depth has a direct influence on the reshaped profile by preventing the displaced rocks to fall down to deeper parts using the test results a new formula is developed for estimation of berm recession by taking into account the influence of the toe berm configuration given an acceptable stability number ho as a design criterion for reshaping berm breakwaters the present method predicts that the recession can be reduced up to 35 by the application of a toe berm thus the main berm width can be shortened resulting in reduction of the required armor stones volume so by using a smaller stone size for the toe berm the stability of the structure is secured and also the total cost of the breakwater can be reduced

weddellite occurrence in peats and other organic rich sediments of florida abstract the mineral weddellite calcium oxalate dihydrate is rarely reported in sediments although it is common in biologic materials including plants forest soils and the urinary stones of mammals research designed to evaluate the factors influencing the fuel grade potential of peat deposits in florida has now documented the occurrence of weddellite as a primary constituent in the inorganic ash fraction of peat and other organic rich soils weddellite is believed to originate within the peat forming basin rather than as a product of sample storage or laboratory preparations the mineral s origin is genetically related to the metabolic activity of abundant plant life at the depositional site and its concentration in the basin is directly related to the percentage of organic matter pr served in the sediments scanning electron micrographs reveal that the mineral s characteristic prismatic needle shape is preserved in peat differential thermal analysis shows initial water loss endotherms at approximately 100 c and 200 c followed by exothermic transformations to caco3 at 300 c and to cao near 780 c

evaluation of scale effects in hydraulic models by analysis of laminar and turbulent flows abstract the paper presents an analysis of laminar and turbulent flow in porous stone material in order to evaluate the order of magnitude of scale effects in hydraulic models hydraulic model tests such as for example breakwater model tests are normally carried out at such small scales that the flow through the various layers of the breakwater is not completely turbulent for this reason scale effects occur a well known method to compensate for the scale effects is to use larger stones than calculated by froude s model law in certain regions of the model the paper presents formulae for the calculation of the compensated stone sizes based on earlier work by engelund further an evaluation of the energy dissipation in hydraulic models is made in order to determine the scale effect due to laminar flow

an experimental study on the hydraulic stability of icelandic type berm breakwaters abstract one of the key aspects of breakwater design and safety assessment is their stability evaluation in the present paper hydraulic stability of a multi layer berm breakwater mlbb has been studied through varying the parameter of eroded area to this end a 2 d experimental model has been carried out in the wave flume of tarbiat modares university using irregular waves with a jonswap spectrum a total of 150 tests have been performed to cover a wide range of sea state conditions and geometrical parameters such as wave height wave period water depth berm width berm elevation stone class i height front slope and nominal diameter of stone class i in this study a new dimensionless parameter is introduced to indicate that the wave breaking type plays a fundamental role in stability of mlbbs eventually a new formula is derived to estimate the damage of mlbbs based on different sea state conditions and various geometrical parameters comparisons are made between the estimated damage parameter of mlbbs by the proposed formula and those estimated by existing formulae the results denote that the present formula not only performs well for mlbbs experimental data but also indicates a reliable performance for some of lykke andersen s 2006 data in statically homogenous berm breakwaters hbbs outside the range of given formula furthermore an innovative approach is presented to examine the eroded area based on the berm recession and the intersection point of reshaped and initial profile from swl which performs faultlessly rather than the existing one

a micromorphological view through a namaqualand termitaria heuweltjie a mima like mound heuweltjies occur throughout namaqualand and the western and southern cape coasts broad low relief termitaria of the harvester termite microhodotermes viator which show different vegetation patterns to the surrounding soils distinguishable even in satellite images there is a direct relationship between soil hardpan occurrence and the heuweltjies characteristically in the semi arid areas the hardpans grade outwards from a central sepiolitic petrocalcic horizon laterally through petro sepiolitic palygorskitic variable in the degree of cementation to the petroduric horizon on the edges in a landscape in which these hardpans are otherwise absent the aim of the study was to investigate the genesis of these hardpans associated with the heuweltjie mound with a particular focus on the build up of calcite and sepiolite the micromorphological study examined a transect through a representative sepiolite bearing heuweltjie on the coast near the olifants river mouth and revealed evidence of termite activity in the central petro calcic part of the mound this concentration of calcite and mg rich clay in the centre can be explained by termite foraging as the regionally characteristic ca and mg rich foliage is moved into the centre of the mound facilitating the precipitation of calcite and sepiolite as bacterial decomposition and subsequent leaching modify the soil solution in the mound the increase in coarse fine ratio from the centre outward showed that accumulation of calcite and sepiolite displaced the original sand matrix by a greater degree than the silica accumulation consistent with the topographically raised surface in the centre limpid yellow low birefringent nodules some with pseudo negative uniaxial interference figures showed a fibrous nature under esem and their low ca and molar mg si ratios of 0 64 to 0 68 esem edx were consistent with sepiolite the presence of the sepiolite with its mg rich composition and hydrophilic character together with organic acids generated from the vegetation collected by the termites is considered to be an explanation for the formation of ooids radial calcite crystals associated with a core of sepiolite colourless non calcareous pseudo uniaxial negative spherulites were present in fresh termite excrement from an active heuweltjie near stellenbosch these were either produced in the termite gut itself or had been ingested along with herbivore dung by the termites the presence of faecal spherulites in termite excrement is significant since it shows that faecal spherulites can be distributed over a wider area than that directly associated with mammalian herbivores

southeast anatolian orogenic belt revisited geology and evolution the southeast anatolian orogenic belt consists of the arabian platform a zone of imbrication and a nappe zone the arabian platform is represented by a thick marine succession the zone of imbric

stable isotopic evidence for latest pleistocene and holocene climatic change in north central texas abstract a paleoclimatic record for a southern great plains locality the aubrey clovis site in north central texas has been established using stable carbon and oxygen isotopes detailed composite stratigraphic sections constrained by 14 c ages place the age of these deposits between 14 200 and 1600 yr b p calcium carbonate samples of lacustrine and pedogenic origin were analyzed oxygen isotopic compositions of most of these in situ carbonates reflect equilibrium precipitation from local meteoric waters oxygen isotope values reflect changes in the composition of meteoric waters tied to changes in the isotopic composition of moisture derived from the gulf of mexico oxygen isotopic variability at the aubrey site is coincident with marine isotopic records from the gulf that vary due to changes in laurentide ice sheet volume and meltwater influx the stable carbon isotopic record reflecting changing biomass through time corroborates humid versus arid interpretations based on sedimentology and rates of alluviation a middle holocene arid period was in contrast to moist early and late holocene climate affirming interpretations of other workers studying southern great plains holocene climate history

hydraulic stability of reshaping berm breakwaters using the wave momentum flux parameter abstract an empirical new berm recession formula is derived based on the assumption that the maximum wave force causing armor movement and berm recession is proportional to the maximum wave momentum flux near the structure toe this concept introduces a more physics based first principles approach to estimate the berm recession recession seems well predicted by the new formula for reshaping berm breakwaters the results from this formula show a better estimation than earlier formulae used for estimating the berm recession

armor stability of hardly or partly reshaping berm breakwaters abstract this paper deals with stability of hardly or partly reshaping berm breakwaters a simple physical argument is used to derive a new stability formula based on the assumption that the maximum wave force causing damage of armor layer is proportional to the maximum wave momentum flux near the structure toe the main goal of the present paper is to provide an estimation technique based on this physical principle to predict the deformation of the front slope in terms of the eroded area the proposed method is verified by comparison with model test data it is found that by using the maximum wave momentum flux approach the damage to the front slope eroded area can be very well predicted moreover a simple method to estimate the eroded area based on measured or calculated berm recession rec and depth of intersection of reshaped and initial profile h f is presented the performance of the simple method based on measured data of rec and h f is better than the presented stability equation based on wave momentum flux parameter when using the best prediction formulae for recession and depth of intersection the simple method and the momentum flux stability equation provide similar uncertainty

an experimental study on the parameterization of reshaped seaward profile of berm breakwaters abstract berm breakwaters are rubble mound structures in which the seaward slope of the initial profile may be reshaped to become more stable under severe wave attack the stones in the seaward slope move from the initial slope to an equilibrium profile a 2d experimental study has been carried out in a wave flume at a hydraulic laboratory of tarbiat modares university to study the effects of sea state and structural parameters on the reshaped profile parameters of such breakwaters a series of 287 tests have been performed to cover the effect of various sea state conditions such as wave height wave period number of waves and water depth at the toe of the structure and structural parameters such as berm width berm elevation above still water level and armor stone size all the tests have been done employing irregular waves with a jonswap spectrum in this paper first the reshaped profiles are schematized and then the key parameters of the reshaped seaward profiles such as step height step length and depth of intersection point of initial and reshaped profile are investigated using results of this experimental work eventually formulae that include some sea state and structural parameters are derived for estimation of the reshaped profile parameters to assess the validity of the proposed formulae comparisons are made between the estimated parameters of reshaped profiles by these formulae and earlier formulae given by other researchers the comparisons show that the estimation procedure foretells reshaping parameters well and with less scatter according to the present data and also other experimental results within the range of parameters tested

comparison of new large and small scale overtopping tests for rubble mound breakwaters abstract many breakwaters are due to functional requirements designed for small wave overtopping discharges from the ec research projects opticrest and clash it is known that overtopping discharges determined from conventional froude scale models of rubble mound breakwaters are smaller than measured in corresponding prototypes the present study examines this scale effect by comparing overtopping discharges in small scale and large scale tests the length scale ratio between the models was 5 7 the reason for using a large scale model instead of a prototype is the difficulties in accurate reproduction of prototype conditions for waves and structure in the model as prototype conditions are not known in sufficient details the model was designed to avoid as many model effects as possible despite this some differences in wave kinematics were detected most probably due to differences in wave generation hardware and software this demonstrates that even under controlled conditions it is very difficult to reproduce similar conditions from the present test results it is concluded despite the model effect that a significant scale effect on small overtopping discharges exists also when wind effects are absent the scale effect seems to be very dependent on the top geometry of the breakwater with much larger scale effects for a low crown wall than for a high one the paper presents an explanation of this difference

soil stability analysis for wave induced momentary liquefaction beneath porous bonded revetments abstract the highly porous revetments made of polyurethane bonded aggregates pba are an ecologically friendly alternative to conventional revetments for protection against coastal erosion no information has yet been reported for these structures on failures from field applications however a well documented collapse of a pba revetment observed in large scale tests gwk tests and a first stability analysis were reported by oumeraci et al 2010 2012 based on these results a methodology is proposed for stability analysis of the embankment subsoil beneath pba revetments against momentary liquefaction considering the results of the comprehensive parametric study alcerreca huerta 2014 using a recently developed cfd csd computational fluids dynamics computational solid dynamics model waveporegeofoam alcerreca huerta and oumeraci 2016a 2016b it will be shown that the proposed stability analysis is able to reproduce the failure observed in the gwk tests so that it can be applied for pba revetment under field conditions in this paper the failure observed in the gwk tests is first briefly reported followed by a description of the numerical parametric study using the validated waveporegeofoam model in order to extend the conditions tested in gwk then the processes underlying soil liquefaction of pba revetments are outlined showing that the excess pore pressure development in the sand core beneath pba revetments is crucial the latter is therefore examined and a formula to predict excess pore pressures in terms of the wave conditions is developed moreover a methodology for the stability analysis of the soil beneath the revetment against soil liquefaction is proposed and implemented to reproduce the failure observed in the gwk tests finally the main results are summarized and implications for further research are drawn

pedogenesis in a pleistocene fluvial system of the northern pantanal brazil sedimentology and hydrology seem to play a predominant role in soil formation in the pantanal since the fluvial systems of this wetland provided quaternary sediments and shaped the landscape however pedogenic processes are active in this region mainly due to the floods that occur during the summer and fall season the goal of this work was to study the pedogenesis in a representative transect on the sao lourenco fluvial fan which has an area of about 16 000 km2 and is one of the largest sedimentary compartments of the northern pantanal west central brazil a transect of 125 m was studied in the late pleistocene sedimentary lobe of the fluvial fan where four landform elements were identified paleo channel paleo levee paleo floodplain and mound and described to show the soil horizon boundaries along the landform unit samples were collected from trenches auger holes and boreholes and were analyzed for soil description and characterization soil analyses carried out were macro and micromorphological physical chemical mineralogical c isotope fractionation and osl dating analyses the set of evidence shows that the studied transect originated from pleistocene sediments due to the activity of the sao lourenco fluvial fan the following soil landform element relationships developed quartzipsamments in the paleo channel plinthaquults in the paleo levee and paleo floodplain and natrustalfs in the mound evidences of pedogenic processes in the transect are a clay eluviation and illuviation resulting in formation of the bt horizon in the soils at the lower part of the transect and mound b gleization and plinthization mainly at the lower part of the transect resulting in formation of mottles reduced soil matrix and nodules plinthite and petroplinthite c bioturbation responsible for addition of materials at the soil surface assisting in the formation maintenance of the mound and d the sodium concentration observed in soils that have higher clay contents which are highest in the mound has the highest levels

oil source rock correlation of the lower paleozoic petroleum system in the baltic basin northern europe the correlation of lower paleozoic marine source rocks with reservoired oils by biomarkers is complex because of the uniform early phanerozoic biomass bacteria and algae and the lack of land plant and animal input accordingly the main source rocks for the most prolific oil province in the baltic basin are still a matter of debate the 10 source rocks and 15 oil samples from 5 northern european countries bordering the baltic sea basin were analyzed by gas chromatography gc with flame ionization detector gc mass spectrometry gcms and gcms ms to detect acyclic isoprenoids and aliphatic aromatic and nitrogen sulfur and oxygen biomarkers chemometric tools were applied to screen for meaningful source and age related biomarkers and to highlight genetics extended tricyclic terpane ratios c24 tetracyclic terpane c26 tricyclic terpane ratios and relative c29 sterane concentrations are considered the most promising biomarkers in differentiating llandovery shales from cambrian to ordovician alum shale and for correlation with expelled oil the uranium irradiation related c26 c28 triaromatic steroid concentrations provide possible distinguishing criteria for the source potential of the different alum shale units enhanced oil maturation by volcanic intrusion is highlighted by sterane biomarkers and polycyclic aromatic hydrocarbons the alum shale is here considered the main source rock for oil accumulations in lower paleozoic reservoirs of the baltic basin oil seepage occurring in ordovician limestone was mainly generated by the middle cambrian alum shale and middle cambrian sandstone reservoirs were mainly sourced by upper cambrian and lower ordovician alum shale with higher maturity considerations about the assessment of migration distance are based on carbazole concentrations and c29 sterane isomerization advanced studies to unravel detailed lower paleozoic oil source rock correlations are based on meaningful biomarkers offer approaches to significantly reduce the exploration risk in this area and could be applied to similar early paleozoic petroleum systems in other basins

spatial patterns and morphology of termite macrotermes falciger mounds in the upper katanga d r congo this study examines the spatial distribution patterns and morphological characteristics of macrotermes falciger mounds in the peri urban zone of lubumbashi d r congo spatial patterns of mounds were assessed using high resolution satellite images for 24 plots of variable size 3 to 27 ha soil morphological features were described for five termite mound profiles of 5 to 9 m depth height a mean areal number density of 2 9 0 4 mounds ha 1 is estimated for the degraded miombo woodland of the study area spatial statistical analyses document that termite mounds are regularly distributed in all studied plots the overall mean nearest neighbour distance between termite mounds is 44 6 0 6 m the high relative number of inactive mounds in the region with regular distribution patterns suggests that current termite mound occurrences are largely relict features there are no clear indications for an impact of the nature of the parent material on the spatial distribution of the mounds one aspect of differences in morphology between the studied mounds is that the stone layer occurs at greater depth in topographic low areas than at crest and slope positions this is interpreted as being mainly conditioned by erosion mn fe oxide concentrations occurring in all studied termite mound profiles reflect a seasonally high perched water table beneath the mound which is more pronounced at lower landscape positions in summary mound positions in the habitat are consistent with intraspecific competition rather than soil and substrate characteristics as controlling factor whereas variation in morphological characteristics between termite mound profiles appears to be a function of the parent material

pressure induced forces and shear stresses on rubble mound breakwater armour layers in regular waves abstract this paper presents the results from an experimental investigation of the pressure induced forces in the core material below the main armour layer and shear stresses on the armour layer for a porous breakwater structure two parallel experiments were performed which both involved pore pressure measurements in the core material 1 core material with an idealized armour layer made out of spherical objects that also allowed for detailed velocity measurements between and above the armour and 2 core material with real rock armour stones the same core material was applied through the entire structure i e no additional filter layers were applied for both experiments high speed video recordings were synchronised with the pressure measurements for a detailed investigation of the coupling between the run up and run down flow processes and the measured pressure variations outward directed pressure gradients were found which exerted a lift force up to 60 of the submerged weight of the core material these maximum outward directed pressure gradients were linked to the maximum run down event and were in general situated at or slightly below the maximum run down level detailed velocity and turbulence measurements showed that the large outward directed pressure gradients in general coincide both in time and space with the maximum bed shear stresses on the armour layer based on the reynolds stresses the bed shear stresses were found to result in a shields parameter in the same order of magnitude as the critical value for movement of the armour stones

occurrence and transformations of iron and manganese in a colluvial terra rossa toposequence of northern italy abstract a soil toposequence in ne italy was studied which consists of a terra rossa on cretaceous limestone on the upper slope grading downwards into a colluvial fan with terra rossa material and finally into alluvial river sediments it is postulated that the red colluviated terra rossa material has come under a moister hydroregime which provided reducing conditions because hematite of the terra rossa dissolved preferentially over goethite as shown by quantitative fe oxide mineralogy soil color changed from 2 5yr to 7 5yr the soils contained two types of concretions red ones with a low feo fed ratio and a high content of hematite and low content of mn oxides and black ones with a high feo fed ratio a small amount of hematite and abundant mn oxides the red concretions are therefore considered as inherited from an earlier period of pedogenesis whereas the black ones are neoformed in the present pedoenvironment this is further supported by the lower al for fe substitution of goethite in the black concretions as compared to a higher al substitution in the goethite inherited from the terra rossa

trends in stability of dynamically stable breakwaters the reshaping of dynamically stable breakwaters was studied subject to variations in armour stone gradation and shape wave characteristics and duration of wave attack from head on waves in a two dimensional wave flume tests were undertaken at the coastal engineering research laboratory of queen s university kingston canada using irregular waves profiles of the structure during the various stages of reshaping were measured using a semi automatic profiler developed for this study the volume of stones and the initial berm width required for development of a stable profile along with the extent to which the toe of the structure progressed seaward were chosen as the characteristic parameters of the reshaped breakwater the results indicated that the toe width formed as a result of reshaping and the area of stones required for reshaping were dependent on the wave height gradation of the armour stone and duration of the storm the initial berm width required for reshaping was also found to be dependent on the wave height armour stone gradation percentage of rounded stones in the armour and the duration of the storm

flow and sediment transport induced by a plunging solitary wave 1 two parallel experiments involving the evolution and runup of plunging solitary waves on a sloping bed were conducted 1 a rigid bed experiment allowing direct hot film measurements of bed shear stresses and 2 a sediment bed experiment allowing for the measurement of pore water pressures and for observation of the morphological changes the two experimental conditions were kept as similar as possible the experiments showed that the complete sequence of the plunging solitary wave involves the following processes shoaling and wave breaking runup rundown and hydraulic jump and trailing wave the bed shear stress measurements showed that the mean bed shear stress increases tremendously with respect to that in the approaching wave boundary layer by as much as a factor of 8 in the runup and rundown stages and that the rms value of the fluctuating component of the bed shear stress is also affected by as much as a factor of 2 in the runup and hydraulic jump stages the pore water pressure measurements showed that the sediment at or near the surface of the bed experiences upward directed pressure gradient forces during the down rush phase the magnitude of this force can reach values as much as approximately 30 of the submerged weight of the sediment the experiments further showed that the sediment transport occurs in the sheet flow regime for a substantial portion of the beach covering the area where the entire sequence of the wave breaking takes place the bed morphology is explained qualitatively in terms of the measured bed shear stress and the pressure gradient forces

rare earth and trace element geochemistry of termite mounds in central and northeastern namibia mechanisms for micro nutrient accumulation abstract rare earth element ree and trace element concentrations of ten termite mounds and adjacent topsoil from central and northeastern namibia were used to investigate the processes underlying the alteration of soil chemical and physical properties by termites macrotermes spp accumulation of micro nutrients in the mounds was of particular interest because of the ecological implications of the enhanced availability of these scarce elements the absolute concentrations of ree and trace elements including nine micro nutrients b fe mn ni cu zn se mo and cd were greater in termite mounds compared to topsoil suggesting a possible external supply of enriched materials or accumulation of in situ weathering products of the underlying bedrock similarities between the chondrite normalized ree patterns of the samples and those of the average upper continental crust ucc and post archaean average australian shale compositions indicated that the mounds and topsoil at each site originated from the same host bedrock coherent behavior between two incompatible elements th and la in both topsoil and mound samples suggested that the two sets of samples were exposed to two different weathering processes the relatively low zr sc ratios fine particle sizes and the persistence of positive eu anomalies of the mounds relative to ucc were interpreted as reflecting 1 a lack of grain sorting effects and 2 active transport of materials rich in primary clay minerals and trace elements from the deeper regolith to the surface by termites lower permeability of mound materials may also prevent leaching of primary minerals and trace elements titanium and zr enrichment in most mound samples 8 samples was attributed to the decomposition of biotite by macrotermes with the concomitant release of ti and zr into the mounds suggesting the termites ability to transform soil minerals and enhance chemical weathering this was further corroborated by a substantial increase in th u ratios in most mounds relative to topsoil because of the oxidizing conditions of the mounds ti and zr are likely to be adsorbed onto fe oxides positive ce anomalies relative to ucc and the high ph values in the mounds indicate calcrete aggradation or mound aeration as a result of burrowing activities of the termites and evaporation from mounds the impacts of the changes in environmental conditions and the termite activities on the mound geochemistry are highlighted by heavy ree hree as well as fe and mn retentions in the mounds heavy ree and light ree lree are likely to coprecipitate with carbonate complexes and fe and mn oxyhydroxides and in the process scavenge a series of micro nutrients such as zn cu cd and co a substantial enrichment of se in mounds despite the oxidizing conditions of the mounds could be attributed to active transport of se enriched materials from deep soil horizons the study demonstrated the suitability of ree and trace element geochemistry for assessing the influence of macrotermes on the physico chemical properties of semi arid soils

on front slope stability of berm breakwaters abstract the short communication presents application of the conventional van der meer stability formula for low crested breakwaters for the prediction of front slope erosion of statically stable berm breakwaters with relatively high berms the method is verified burcharth 2008 by comparison with the reshaping of a large norwegian breakwater exposed to the north sea waves as a motivation for applying the van der meer formula a discussion of design parameters related to berm breakwater stability formulae is given comparisons of front erosion predicted by the use of the van der meer formula with model test results including tests presented in sigurdarson and van der meer 2011 are discussed a proposal is presented for performance of new model tests with the purpose of developing more accurate formulae for the prediction of front slope erosion as a function of front slope relative berm height relative berm width method of armour stone placement and hydraulic parameters the formulae should cover the structure range from statically stable berm breakwaters to conventional double layer armoured breakwaters

an improved calculation model for the wave induced pore pressure distribution in a rubble mound breakwater core abstract the spatial distribution of the wave induced pore pressure height in the core of a conventional rubble mound breakwater is studied in this work use is made of existing theoretical and experimental knowledge to establish a calculation model for the pressure distribution on the front core slope and the attenuation of pore pressures within the breakwater core the new model formulae are derived empirically and calibrated by means of a non linear regression analysis of pore pressure measurements in a large scale conventional breakwater model under non overtopping and non breaking wave conditions they relate the spatial distribution of pore pressure height to the sea state in front of the breakwater considering a homogeneous breakwater core but do not contain any material properties related to the porous flow resistance the new calculation model predicts the pore pressure distribution with higher accuracy than the existing method generally employed and is applicable in a broad range of wave conditions the calculation model is validated with additional experimental data from pore pressure measurements on a small scale model confirming the capability of predicting the pore pressure height under varying wave conditions the comparison between both models moreover provides insight into the general applicability of the calculation model

laboratory experiments on low crested breakwaters abstract new unique laboratory experiments on low crested structures lcss have been performed within the delos project the experiments were carried out in three european laboratories aiming at extending and completing existing available information with respect to a wide range of engineering design properties such as structural stability wave and current flows and wave transmission 3d wave basin tests were performed to provide information especially about the wave obliquity where almost no research has been done before flow velocities inside and close to the surface of structures were studied in a wave channel at small scale and scale effects regarding wave transmission and reflection were studied in a wave channel at a large scale facility the paper describes the experiments and associated databank with respect to objectives test program set ups and measurements results guidelines and recommendations elaborated from the tests are included in the other companion papers of the coastal engineering special issue on delos

three dimensional investigations of wave overtopping on rubble mound structures to study the influence of wave obliquity and directional spreading on wave overtopping of rubble mound breakwaters a total of 736 three dimensional model tests were carried out at aalborg university the results of these tests are presented and analysed in this paper yielding a new empirical reduction factor to describe the influence of wave obliquity and directional spreading on the average wave overtopping discharges the study shows that perpendicularly incident long crested waves result in conservative values of the overtopping discharge for the tested cross section

laboratory observations of flow and sediment transport induced by plunging regular waves 1 two parallel experiments involving the evolution and runup induced by plunging regular waves near the shoreline of a sloping bed are considered 1 a rigid bed experiment allowing direct hot film measurements of bed shear stresses and 2 a sediment bed experiment allowing for the measurement of pore water pressures as well as observation of sediment suspension and bed morphological changes both experiments utilize the same initial bed profile and wave forcing the experiments show that the mean bed shear stresses experienced onshore of incipient breaking are amplified by nearly a factor of 2 relative to prebreaking conditions whereas their corresponding turbulent fluctuations are amplified even more strongly by a factor of 5 6 the plunging processes lead to a series of vortices whose formation may be explained as the result of shear layer instability measurements show that these vortices can significantly enhance peaks in the offshore directed bed shear stresses moreover near bed pore pressure measurements indicate that these vortices cause large upward directed pressure gradients which in turn produce a corresponding series of suspended sediment plumes shoreward of the initial breaking event these findings are related to the induced morphological changes over both short and long time scales the present results are also compared and contrasted with previous experiments utilizing a similar methodology but involving plunging solitary waves

toe berm design for very shallow waters on steep sea bottoms abstract the toe berm is a relevant design element when rubble mound breakwaters are built on steep sea bottoms in breaking conditions different design formulas can be found in the literature to predict the damage caused to submerged toe berms placed on gentle bottom slopes however these formulas are not valid for very shallow waters in combination with steep sea bottoms where toe berms receive the full force of breaking waves to guarantee breakwater stability in these conditions new design formulas are needed for toe berms to this end physical model tests were carried out and data were analyzed to characterize rock toe berm stability in very shallow water and with a bottom slope m 1 10 based on test results a new formula was developed with three parameters to estimate the nominal diameter d n 50 of the toe berm rocks water depth at the toe h s deep water significant wave height h s0 and deep water wave length l 0p

differentiation of pedogenic and lithogenic carbonate forms in texas abstract sixteen pedons representing soils developed from limestone and fluvial deltaic sediments were sampled in central and western texas 300 800 mm annual precipitation to differentiate pedogenic secondary and lithogenic inherited carbonate forms by field and laboratory techniques lithogenic carbonate forms identified in the field included indurated limestone bedrock and coarse limestone fragments lithorelicts field identified pedogenic forms included petrocalcic horizons thin laminar cappings on indurated limestone carbonate joint seams pendants on pebbles and carbonate films and threads on ped faces small

on rubble mound breakwaters of composite slope abstract the geometrical properties of the armor layer of rubble mound breakwaters were investigated by observations made on two cases the first case is a laboratory scaled model of natural rock designed with a composite slope the second is a breakwater in the sea constructed with a uniform slope of tetrapods in both cases the cross section underwent changes resulting in an apparently stable profile of composite slope this implied that for stability the optimal armour layer should be of composite slope the general nature of this profile was implied by the geometrical similarity between the two cases which were basically so different

a new formula for the sea state and structural parameters influencing the stability of homogeneous reshaping berm breakwaters the berm recession of a reshaping berm breakwater has a very important role for the stability of this kind of structure based on a 2d experimental modeling method in a wave flume the recession of the berm due to sea state and structural parameters has been studied irregular waves with a jonswap spectrum were used a total of 215 tests have been performed to cover the impact of sea state conditions such as wave height wave period storm duration and water depth at the toe of the structure and structural parameters such as berm elevation from still water level berm width and stone diameter on berm recession in this paper first a new dimensionless parameter is introduced to evaluate the combined effect of wave height and wave period on berm recession using results of the experimental work then a formula that includes some sea state and structural parameters is derived using the new dimensionless parameter for estimating the berm recession a comparison is made between the estimated berm recessions by this new formula and formulae given by other researchers to show the preference of using the new dimensionless parameter the comparison shows that the recession estimated by the new formula has not only a better correlation with the present experimental data but also has an improved correlation with other experimental results within the range of parameters tested outside the range of parameters tested the lykke andersen 2006 formula performed best

stone movement on a reshaped profile physical model tests were carried out aiming to provide information on armor stone movements in a berm breakwaters the following items were examined displacement threshold frequency and length of stone displacements data were obtained from the observation of cumulative displacements at the end of each wave attack and from video records during the attacks basic statistical analysis was performed threshold conditions moving frequency and cumulative displacements are expressed as function of a modified mobility number as stone mobility increases with both wave height and wave period information on mobility and displacement is eventually used to estimate longshore transport and abrasion the longshore model is based on the assumption that stones move during up and down rush in the direction of incident and reflected waves the model compares favourably with experimental existing results the abrasion model is based on a proportionality assumption between abrasion volume and abrasion work the proportionality coefficient characterizing the stone material resistance to abrasion is derived from latham and poole mill abrasion tests

anhydrite pseudomorphs and the origin of stratiform cu co ores in the katangan copperbelt democratic republic of congo the stratiform cu co ore mineralisation in the katangan copperbelt consists of dispersed sulphides and sulphides in nodules and lenses which are often pseudomorphs after evaporites two types of pseudomorphs can be distinguished in the nodules and lenses in type 1 examples dolomite precipitated first and was subsequently replaced by cu co sulphides and authigenic quartz whereas in type 2 examples authigenic quartz and cu co sulphides precipitated prior to dolomite and are coarse grained the sulphur isotopic composition of the copper cobalt sulphides in the type 1 pseudomorphs is between 10 3 and 3 1 relative to the vienna canyon diablo troilite indicating that the sulphide component was derived from bacterial sulphate reduction bsr the generation of text hco 3 during this process caused the precipitation and replacement of anhydrite by dolomite a second product of bsr is the generation of h2s resulting in the precipitation of cu co sulphides from the mineralising fluids initial sulphide precipitation occurred along the rim of the pseudomorphs and continued towards the core precipitation of authigenic quartz was most likely induced by a ph decrease during sulphide precipitation fluid inclusion data from quartz indicate the presence of a high salinity 8 18 eq wt nacl fluid possibly derived from evaporated seawater which migrated through the deep subsurface 87sr 86sr ratios of dolomite in type 1 nodules range between 0 71012 and 0 73576 significantly more radiogenic than the strontium isotopic composition of neoproterozoic marine carbonates 87sr 86sr 0 7056 0 7087 this suggests intense interaction with siliciclastic sedimentary rocks and or the granitic basement the low carbon isotopic composition of the dolomite in the pseudomorphs 7 02 and 9 93 relative to the vienna pee dee belemnite v pdb compared to the host rock dolomite 4 90 and 1 31 v pdb resulted from the oxidation of organic matter during bsr

on berm breakwaters recession crown wall wave forces reliability abstract the paper reviews different formulae lykke andersen 2006 lykke andersen and burcharth 2010 torum 2007 and moghim et al 2011 for recession of berm breakwaters and compares calculated recession with previous and new recession test data there are differences of the results by different formulae but by and large all the formulae give reasonable results on the recession for shallow water berm breakwaters it seems that the lykke andersen 2006 formula works best for the deep water cases although the torum 2007 formula seems to work as good for the homogenous berm breakwater case the moghim et al 2011 formula was not included in the comparison for the deep water cases because the deep water cases are outside the validity of the formula results of tests on different alternative berm breakwater designs which may be considered as practical economic designs have also been included but without any comparison with any formulae simply because the formulae do not cover the specific designs wave forces from model tests on crown walls on berm breakwaters are presented and compared with an existing formula for wave forces on a crown wall on conventional rubble mound breakwaters pedersen 1995 it appears that the wave forces on a crown wall on a berm breakwater are smaller than the wave forces on a crown wall on a conventional rubble mound breakwater finally a probability of failure analysis of a site specific berm breakwater the sirevag berm breakwater norway is presented using monte carlo simulations the probability of failure analysis shows that the sirevag berm breakwater is extremely strong

rock stability of rubble mound breakwaters with a berm the stability of rock slopes with a horizontal berm has been studied by means of physical model tests this paper is focussed on the rock slope stability of the slopes above and below the berm by applying a berm the rock size can be reduced compared to the required rock size for a straight slope without a berm this reduction can be significant for the slope above the berm the influence of the slope angle 1 2 and 1 4 the width of the berm the level of the berm and the wave steepness have been investigated based on the test results prediction formulae have been derived to quantify the required rock size for rubble mound breakwaters with a berm

tectonic evolution of the lufilian arc central africa copper belt during neoproterozoic pan african orogenesis abstract the lufilian arc of central africa also called katangan belt or copperbelt is a zone of low to highgrade metasedimentary and subsidiary igneous rocks of neoproterozoic age hosting highgrade cucou and pbzn mineralizations the lufilian arc is located between the congo and kalahari cratons and defines a structure which is convex to the north three major phases of deformation characterize the construction of the lufilian arc the first phase d1 called the kolwezian phase developed folds and thrust sheets with a northward transport direction d1 deformation occurred in the lufilian arc between ca 800 and 710 ma with a peak in the range 790 750 ma it is here correlated with the main deformation in the zambezi belt southward verging folds with the same trends as the d 1 structures were previously linked to a second tectonic event named kundelunguian phase of the lufilian orogeny we show in this paper that they are backfolds developed during d1 along katangan ramps and especially along the kibaran foreland the second phase d2 of the lufilian orogeny is the monwezi phase including several large leftlateral strikeslip faults which have been activated successively during this deformation phase the eastern block of the belt rotated clockwise giving the present day nwse trend of d1 structures in this part of the lufilian arc and generating its convex geometry the mwembeshi dislocation the major transcurrent shear zone separating the zambezi and lufilian arc was mostly active during the d2 deformation phase d2 deformation occurred between ca 690 and 540 ma such a long time interval is attributed to the migration of strikeslip faults developed sequentially from south to north and probably to a slow convergence velocity during the collision between the congo and kalahari cratons the third phase d3 of the lufilian orogeny is a late event called the chilatembo phase marked by structures transverse to the trends of the lufilian arc this deformation and the post d 2 uppermost kundelungu sequence ks3 plateaux group are younger than 540 ma and probably early paleozoic

the influence of a berm and roughness on the wave overtopping at dikes abstract a reliable estimation of average wave overtopping discharge is important for dike design and safety assessment berms and roughness elements are widely applied to reduce the overtopping discharge over dikes in this study the effects of a berm and roughness on the wave overtopping discharge are investigated by means of physical model tests new empirical formulae are derived from the analysis of the experimental data in order to provide more accurate estimations of reductive influence of berms and roughness on the wave overtopping discharge additionally a new formula is developed to estimate the reductive influence of varying roughness along the waterside slopes with a berm the new equations show a significantly better performance within the tested range when compared with existing formulae for the average overtopping discharge

role of calcium oxalate biomineralization by fungi in the formation of calcretes a case study from nazareth israel abstract biomineralized fungal filaments often referred to as calcified filaments are of interest because of their role in the calcium cycle in calcretes the mineralogy of the crystals associated with these filaments and the evolution of their numerous crystal habits in a calcrete from nazareth israel are the subject of this study removing the be window from an energy dispersive spectrometry eds microprobe coupled with a scanning electron microscope sem permitted the measurement of the light elements c and o us well as ca comparison of crystal spectra to those of known standards demonstrated that the great majority of needles associated with the fungal filaments are calcium oxalate based on these results a model of fungal filament mineralization is proposed that describes the e olution of weddellite polyhydrate calcium oxalate into whewellite monohydrate calcium oxalate in a sequence that includes all of the crystal morphologies observed by sem followed by a less well understood diagenetic transformation of monohydrate calcium oxalate into calcium carbonate

on berm breakwaters stability scour overtopping abstract experimental studies on the stability of multilayer berm breakwaters have been carried out two stone mass densities have been used the results have been compared with the results of homogenous berm breakwaters and with other results of multilayer berm breakwaters an equation for the berm recession for homogenous berms has been derived including the effect of stone gradation and water depth erosion at and erosion protection of berm breakwaters have been investigated as well as wave overtopping discharges

the contribution of termites to the microgranular structure of soils on the uasin gishu plateau kenya abstract the structure of many clay soils in tropical africa is composed of microaggregates that range in size from 0 03 to 1 mm these structural units are often very stable and known as pseudo sand or pseudo silt their presence is detected from the loamy feel of the soil this paper tests the hypothesis that termites contribute to a stable microgranular i e finely aggregated soil structure a termite mound was selected on pedologically unaffected clayey weathering material derived from phonolite the fate of microaggregates produced by termites has been followed through the various stages of mound building field evidence was supplemented with microscopic analysis development of the mound begins when lumps of soil are detached from the subsoil by termites and carried as microaggregates up to the surface in the next stage the microaggregates are cemented to form the nest breakdown begins when the nest is abandoned and disintegrates by splash and runoff producing colluvium or is demolished by ants in the final stage this material is integrated in the soil of the mound soil aggregates produced by splash ants and soil forming processes have different size characteristics but the original microaggregates produced by the termites are preserved in the matrix throughout it is assumed that they owe their stability to impregnation with saliva or other body fluid excreted by the termites termites produce also microaggregates in the form of fecal pellets but these appear to be unstable and are found only in the voids of the soil developed during the last stage

wave loads on rubble mound breakwater crown walls abstract crown walls are primarily built to reduce wave overtopping of mound breakwaters several methods have been proposed to calculate wave loads on the crown wall e g iribarren and nogales iribarren r nogales c 1964 obras maritimas dossat ed madrid 376 pp jensen jensen o j 1984 a monograph on rubble mound breakwaters danish hydraulic institute and gunbak and gokce gunbak a r gokce t 1984 wave screen stability of rubble mound breakwaters international symposium of maritime structures in the mediterranean sea athens greece pp 2 99 2 112 in this paper a new method based on those previous results and on further experimental work using monochromatic waves is presented the application of the new method requires waves breaking on the armour layer i e only broken waves will reach the crown wall the method is extended to irregular waves via the hypothesis of equivalence introduced by saville saville t 1962 an approximation of the wave run up frequency distribution proc 8th international conference on coastal engineering mexico city and is applied to the crown walls of gijon and bilbao breakwaters in spain the comparison of the probability force distributions obtained by the present method to that measured by burcharth et al burcharth h f frigaard p berenguer j m gonzalez b uzcanga j villanueva j 1995 design of the ciervana breakwater bilbao in t telford ed proc 4th coastal structures and breakwaters chap 3 institution of civil engineers and jensen 1984 is relatively good

theoretical and experimental study on wave damping inside a rubble mound breakwater wave decay in a rubble mound breakwater has been analysed theoretically for various types of damping functions linear quadratic and polynomial the applicability of these damping functions for wave decay in the landward part of the breakwater core has been investigated in large scale model tests the properties of the rock materials that have been used in the model tests have been determined to provide a rational basis for the damping coefficients the analysis is based on detailed measurements of wave conditions and pressure distributions inside the breakwater the theoretical approaches have been validated and where necessary extended by empirical means the wave decay inside the breakwater can be reasonably approximated by the commonly applied linear damping model resulting in exponential wave height attenuation an extended polynomial approach provides a slightly better fit to the experimental results and reflects more clearly the governing physical processes inside the structure

rock toe stability of rubble mound breakwaters abstract the toe structure of a breakwater provides support to the armour layer and protects the structure from damage due to scour at the toe often a toe structure consists of rock material several design formulae exist to predict the amount of damage to the toe structure under wave loading these design formulae for the required rock size include effects of the wave height and the water depth above the toe structure here rock toe stability has been studied by means of physical model tests to provide information on the required rock size in the toe structure the tests and analysis are focussed not only on the influence of the wave height and the water depth above the toe structure but also on the influence of the width of the toe structure the thickness of the toe and the wave steepness the wave steepness width of the toe and the thickness of the toe appear to affect the damage to the toe these parameters need to be taken into account in order to derive accurate predictions of the damage to the toe structure based on the test results a prediction formula has been derived including these effects the formula can be used to determine the required rock size in the toe of rubble mound breakwaters within the ranges of the performed tests

the origin of carbonates in termite mounds of the lubumbashi area d r congo article i nfo the origin of carbonate accumulations in termite mounds is a controversial issue this study is an attempt to elucidate the processes of carbonate precipitation in macrotermes mounds built on ferralsols in upper katanga d r congo whereby a differentiation between pedogenic and inherited carbonates is considered carbonate features were investigated for a 9 m deep termite mound profile and for an 18 m wide cross section through a termite mound and the adjacent soil using field and laboratory techniques field evidence for a pedogenic origin includes morphological type soft powdery materials nodules and coatings on ped surfaces and distribution patterns of the carbonates thin section studies reveal that the carbonates occur predominantly as impregnative orthic nodules and less commonly as coatings both clearly pedogenic calcareous pellets are interpreted as locally reworked pedogenic carbonates x ray diffraction xrd scanning electron microscopy energy dispersive x ray spectrometry sem eds and stable isotope 13 c analyses show that all isolated carbonate features consist of high mg calcite 4 9 12 3 mol mgco3 with 13

stability of rubble mound slopes under random wave attack the objective of the present research project is to give new practical design formulae for rubble mound slopes under random wave attack the study is based upon a series of model tests more than two hundred tests have been performed in order to vary systematically all the relevant variables the main shortcomings in hudson type formulae have been solved as a result of the present series of investigations stability formulae are given which include the influence of wave period number of waves armour grading spectrum shape groupiness of waves and the permeability of the core

the influence of armour stone gradation on dynamically stable breakwaters abstract dynamically stable or berm breakwaters are structures in which the armour layer is comprised of a wide range of stone sizes and undergoes reshaping in response to wave action as a result of this wave action a stable profile is achieved the effect of gradation of armour stones and the amount of rounded stones in the armour on dynamically stable breakwaters was assessed in a two dimensional wave flume a total of 52 series of tests were undertaken at the coastal engineering research laboratory of queen s university kingston canada using irregular waves profiles of the structure during the various stages of reshaping were measured using a semi automatic profiler developed for this study four gradations of armour stones were used giving a range in uniformity coefficient d 85 d 15 of 1 35 to 5 4 the core of the breakwaters was relatively permeable the volume of stones and the initial berm width required for development of a stable profile along with the extent to which the toe of the structure progressed seaward were chosen as representative parameters of the reshaped breakwater the results indicated that the toe width formed as a result of reshaping and the volume of stones required for reshaping were dependent on the gradation of the armour stone the initial berm width required for reshaping was also found to be dependent on the gradation and the percentage of rounded stones in the armour

structural stability of detached low crested breakwaters abstract the aim of the paper is to describe hydraulic stability of rock armoured low crested structures on the basis of new experimental tests and prototype observations rock armour stability results from earlier model tests under non depth limited long crested head on waves are reviewed results from new 2 d and 3 d model tests carried out at aalborg university are presented the tests were performed on detached low crested breakwaters exposed to short crested head on and oblique waves including depth limited conditions a formula that corresponds to initiation of hydraulic damage and allows determining armour stone size in shallow water conditions is given together with a rule of thumb for the required stone size in depth limited design waves rock toe stability is discussed on the basis of prototype experience hard bottom 2 d tests in depth limited waves and an existing hydraulic stability formula toe damage predicted by the formula is in agreement with experimental results in field sites damage at the toe induced by scour or by sinking is observed and the volume of the berm is often insufficient to avoid regressive erosion of the armour layer stone sinking and settlement in selected sites for which detailed information is available are presented and discussed

effects of submerged berms on the stability of conventional rubble mound breakwaters abstract berms deployed at the toe of conventional breakwaters may be needed to reduce bottom settlements and to limit scour in front of the structure due to coastal currents in the mean time they may be effective in increasing the stability of the armor layer and also in minimizing the wave overtopping discharge compared to straight sloped conventional breakwaters without a berm this research aims to provide a new design criterion for the armor layer of conventional breakwaters with submerged berms marked by small thickness compared to water depth indeed past researches focused on the influence of relatively high berms on the stability of the armor layer the design of the berm itself is not tackled herein the effects of submerged berms on the incident waves transformation have been evaluated by means of a numerical model validated by using experimental data then a parametric correction factor of the incident significant wave height at the toe of the structure is provided and included in well established design criteria the experimental comparison confirms the reliability of the proposed method by highlighting the importance to use design criteria within their validity ranges in order to avoid an unsafe dimensioning of the armor elements

numerical modelling of wave interaction with dynamically stable structures wave interaction with dynamically stable structures is simulated by means of a numerical model based on finite amplitude shallow water wave equations the model can simulate wave motion on and inside permeable structures for dynamically stable structures including berm breakwaters reef type structures and gravel beaches a procedure is developed to simulate the natural response to wave attack this procedure is extended for instance by implementing effects of grading and effects of seawalls to increase the applicability for practical applications

biologically induced accumulations of caco3 in orthox soils of biga ivory coast biologically induced accumulations of calcium carbonate have been found inside orthox soils under and around the native iroko tree milicia excelsa moraceae in biga ivory coast the nature of these accumulations and their origin were studied in two soil profiles directly under the tree and at a distance of 30 cm from the trunk microscale forms of caco3 include 1 wood pseudomorphic structures such as parenchyma cells cellulose fibers and calcitic vessel infillings 2 three types of rhombohedra and 3 needle fiber calcite nfc in addition large scale blocks exhibit three types of textures 1 micritic calcite which seems to be the original material 2 light colored sparite in moldic voids and 3 asymmetrical radiaxial laminated fibrous cement some micritic aggregates and hemi spherulites vaterite were found in the sap on the trunk as well as in soils on silica grains and the wood itself the mineralogy of all these carbonate forms is mainly a stoichiometric calcite or a moderately enriched mg calcite however some samples contain monohydrocalcite as well as two polymorphs of calcium oxalate weddellite and whewellite calcite precipitation is facilitated by the oxidation of oxalate by soil bacteria that contributes to the increase in ph in biga soils this is in contrast to conventional orthox soils therefore three conditions are necessary for biologically induced precipitation of calcium carbonate in orthox soils associated with iroko trees the presence of a large amount of oxalate originating from the tree and fungi the existence of an oxalotrophic flora for oxalate oxidation into carbonate and a dry season

investigations on the porous media equations and resistance coefficients for coastal structures abstract this paper considers the flow in porous media that occurs in coastal and offshore engineering problems over the past decades numerous formulations of flow equations for porous media have been presented the present work re examines the porous media equations of the most recent form and corrects some shortcomings which were identified the applied type of porosity models relies on empirical resistance coefficients which often need to be measured or calibrated only few examples of calibration for numerical models which are present in the literature often applied the same experimental results in this study new calibration cases were introduced to the calibration procedure in order to achieve a better understanding of the variation of the resistance coefficients hereby the coefficients were determined with a better description over the entire parameter space for the resistance coefficients than previously found in the literature constant values for the resistance coefficients for a broad range of flow conditions were recommended based on the new calibrations the model was validated for the main physical processes that occur in wave structure interaction in coastal structures including three dimensional wave structure interaction run up run down and pressure damping regular and irregular wave conditions and evaluation of overtopping simple two and three dimensional uniform caisson structures and breakwater layouts were investigated the model was implemented in the open source cfd library openfoam and has been made publicly available to the engineering community as part of the wave generation framework waves2foam