layer thicknesses and velocities of wave overtopping flow at seadikes abstract seadikes often fail due to wave overtopping and a failure of the landward slope therefore these aspects have to be taken into account for the design of seadikes in present design the calculation of the crest height of seadikes is essentially based on using a design water level and the corresponding wave run up height an average overtopping rate is generally considered for wave overtopping which can not account for the stresses and other effects due to extreme individual overtopping events landward slope design is more or less based on experience it can be concluded from failure analysis that dike failures on the landward slope are rather initiated by individual overtopping events in particular by the related overtopping flow velocities and layer thicknesses which are relevant for the prediction of erosion infiltration and slip failure therefore overtopping flow velocities and layer thicknesses are required in addition to average overtopping rates as hydraulic boundary conditions for the geotechnical stability analysis of seadikes the objective of the present paper is the theoretical and experimental determination of overtopping flow velocities and layer thicknesses on the seaward slope the dike crest and the landward slope of a seadike overtopping parameters are derived on the basis of small scale model tests which are required for the design of the landward slope and to avoid dike failures by wave overtopping in the future for the prediction of the layer thicknesses and the velocities of the overtopping flow on the seaward slope the dike crest and the landward slope a set of theoretical formulas is derived and validated by hydraulic scale model tests

liquefaction and post liquefaction assessment of lightly cemented sands post liquefaction response of lightly cemented sands during an earthquake may change and become similar to uncemented sands due to bonding breakage in the current study the effect of degree of ce

quantifying damage saturation and anisotropy in cracked rocks by inverting elastic wave velocities crack damage results in a decrease of elastic wave velocities and in the development of anisotropy using non interactive crack effective medium theory as a fundamental tool we calculate dry and wet elastic properties of cracked rocks in terms of a crack density tensor average crack aspect ratio and mean crack fabric orientation from the solid grains and fluid elastic properties using this same tool we show that both the anisotropy and shear wave splitting of elastic waves can be derived two simple crack distributions are considered for which the predicted anisotropy depends strongly on the saturation reaching up to 60 in the dry case comparison with experimental data on two granites a basalt and a marble shows that the range of validity of the non interactive effective medium theory model extends to a total crack density of approximately 0 5 considering symmetries up to orthorhombic in the isotropic case kachanov s 1994 non interactive effective medium model was used in order to invert elastic wave velocities and infer both crack density and aspect ratio evolutions inversions are stable and give coherent results in terms of crack density and aperture evolution crack density variations can be interpreted in terms of crack growth and or changes of the crack surface contact areas as cracks are being closed or opened respectively more importantly the recovered evolution of aspect ratio shows an exponentially decreasing aspect ratio and therefore aperture with pressure which has broader geophysical implications in particular on fluid flow the recovered evolution of aspect ratio is also consistent with current mechanical theories of crack closure in the anisotropic cases both transverse isotropic and orthorhombic symmetries were considered anisotropy and saturation patterns were well reproduced by the modelling and mean crack fabric orientations we recovered are consistent with in situ geophysical imaging

monotonic behavior of mississippi river valley silt in triaxial compression the static behavior of mississippi river valley silt was characterized using triaxial compression testing silt specimens especially overconsolidated ones showed dilation behavior there was no unique critical state among specimens with different overconsolidation ratios ocrs with ocrs of 1 2 and 8 the specimens exhibited normal behavior and dilated more as effective consolidation pressure dropped however for an ocr of 4 the specimens showed opposite behavior and dilated more as effective consolidation pressure rose the friction angle of the silt was computed on the basis of several failure criteria and the limiting strain was found to be the best one owing to better consistency and rational results of the friction angle the silt showed a unique behavior compared with sand and clay the critical state line was not parallel to the normal consolidation curve in the e lnp 0 space the stress strain behavior can be normalized by effective consolidation pressure the normalized shear strength of overconsolidated specimens was correlated to that of a normally consolidated specimen using ladd et al s equation with an mvalue of 0 58 for low plasticity silts however the normalized shear strength of overconsolidated silts cannot be related to ocr directly it was indicated that at least the normalized shear strength of a normally consolidated specimen needs to be tested for low plasticity silts to obtain the normalized shear strength of overconsolidated specimen using ladd et al s equation doi 10 1061 asce gt 1943 5606 0000603 2012 american society of civil engineers

the mechanics of an italian silt an example of transitional behaviour by controlling the particle size distribution of an italian silt the influence of grading on its behaviour was investigated as the clay content was reduced the behaviour changed from a typical clay mode to a transitional form between that of clays and sands that had previously been seen only for gap graded soils emphasising that this type of behaviour is possibly much more extensive than previously thought the work has highlighted several features of transitional behaviour and in particular that unique normal compression and critical state lines do not exist that rendulic s principle does not apply and that drained and undrained tests do not reach unique ultimate states

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

undrained cyclic shear behaviour of weathered tephra weathered tephra is prevalent across volcanic islands like the north island of new zealand and is composed of volcanic airfall materials that have been subjected to various soil processes understa

an analytical model of wave overtopping flow velocities on dike crests and landward slopes abstract an accurate description of the maximum flow velocity across flood protective structures is necessary in order to determine the stability of the landward slope and the amount of cover erosion in this paper two new formulas are derived to describe the change in the maximum overtopping flow velocity along the dike crest and the adjacent landward slope these formulas are coupled in an effort to accurately predict the velocities in wave overtopping events this analytical model is validated using 244 data points from flume tests and 300 data points from field tests on river dikes in the netherlands the modelled flow velocity shows good agreement with the measured flow velocity with a nash sutcliffe efficiency factor varying from 0 49 to 0 87 also the derived formulas are compared with existing formulas for wave overtopping flow velocities and overall showed a better performance for a wide range of geometries and covers

wave reflection from coastal structures in design conditions based on an extensive database of more than 4000 data this paper analyses wave reflection for various types of coastal structures in design conditions such as smooth rock and armour unit slopes a new simple formula has been developed that relates the reflection coefficient to the breaker parameter and seems to fit all kinds of revetment materials by changing two coefficients these coefficients depend only on the correct roughness factor provided by recent research on overtopping discharges the effects on reflection due to composite slopes and to low crests are also examined and proper extensions of the formula are provided 2008 elsevier b v all rights reserved

postcyclic recompression stiffness and consolidated cyclic strength of silt low plasticity silts are liquefiable and the dissipation of pore pressures after an earthquake will be accompanied by densification and compression of the soil skeleton anisotropic rather than isotropic stress distributions are commonly found to exist in slopes or silty fills placed under k0 conditions and this can be enhanced further by the weight of overlying structures compression after an earthquake generally increases soil resistance but it can still be liquefied by aftershocks the postcyclic recompression of silt and postdrainage monotonic and cyclic strength and stiffness have therefore been investigated with respect to the effect of initial anisotropic consolidation the compressibilities during postcyclic recompression were similar to those for isotropic consolidation samples with a greater initial anisotropy had less volumetric strain but larger axial strains during postcyclic drainage under stress reversal conditions failure occurred as a result of the development of double amplitude cycl

anisotropic poroelasticity in a rock with cracks deformation of a saturated rock in the field and laboratory may occur in a broad range of conditions ranging from undrained to drained the poromechanical response is often anisotropic and in a brittle rock closely related to preexisting and stress induced cracks this can be modeled as a rock matrix embedded with an anisotropic system of cracks assuming micro isotropy expressions for three of the poroelastic coefficients of a transversely isotropic rock were derived in terms of the crack density tensor together with published results for the five effective elastic moduli this provides a complete micromechanical description of the eight independent poroelastic coefficients of such a cracked rock relatively simple expressions were obtained for the skempton pore pressure tensor which allow one to infer the crack density tensor from undrained measurement in the laboratory and also to infer the biot willis effective stress coefficients the model assumes a dilute concentration of non interactive penny shaped cracks and it shows good agreement with experimental data for berea sandstone with crack density values up to 0 6 whereas predictions on the storage coefficient and normal components of the elastic stiffness tensor also seem reasonable significant discrepancy between model and measurement was observed regarding the off diagonal and shear components of the stiffness a plausible model had been proposed for development of very strong anisotropy in the undrained response of a fault zone and the model here placed geometric constraints on the associated fracture system

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

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

a performance test of nearshore wave height prediction with clash datasets abstract the clash database was analyzed for extraction of a set of data having the measured wave heights at both the deep station and the toe of the structure for wave overtopping tests yielding 1214 data from 29 datasets wave heights in front of the toe of the structure were estimated with the goda formulas and compared with the measured ones comparison yielded the overall mean of 1 106 with the standard deviation of 0 155 for the ratio of the estimated to the measured heights which support the use of the goda formulas for prediction of nearshore wave heights another set of 1215 data having the measured wave heights at the deep station and the wave heights calculated with the swan model was also extracted from the clash database a comparative test of the swan model using the wave height estimated with the goda formulas in lieu of the measured height indicated the performance of the swan model being similar to that of the goda formulas but a tendency of underestimation was noticed in shallow water on a beach of very gentle slope

microcrack induced elastic wave anisotropy of brittle rocks the failure of brittle rocks during compression is preceded by the formation growth and coalescence of microcracks elastic wave velocities are reduced in the presence of open microcracks and fractures and may therefore be used to monitor the progressive damage of the rock in general these microcracks are not randomly oriented and the rock displays an elastic anisotropy the elastic anisotropy due to cracks can be expressed in terms of a second rank and fourth rank crack density tensor for open cracks the contribution of the fourth rank crack density tensor to the elastic wave velocities is small these results are compared with recent measurements of the ultrasonic compressional and shear wave velocities for propagation parallel and perpendicular to an increasing axial stress applied at constant confining stress to berea sandstone inversion of the velocity measurements indicates that the microcracks propagate parallel to the maximum compressive stress in agreement with current rock mechanics theory a reasonable fit to the data is obtained using only the second rank crack density tensor even though at high confining stress the cracks are expected to be in partial contact along their length this is consistent with the model of elastic wave propagation in a medium containing partially contacting fractures published by white however measurements of off axis wave velocities are required to fully quantify the contribution of the fourth rank crack density tensor

influence of directional spreading on wave overtopping of sea dikes with gentle and shallow foreshores abstract the work highlights the importance of directional spreading effects on wave overtopping estimation in shallow and mild sloping foreshores wave short crestedness leads in general to a reduction of mean overtopping discharges on coastal structures in the present work the case of a sea dike with gentle foreshore in very and extremely shallow water conditions is analysed physical model tests have been carried out in order to investigate the effect of directional spreading on overtopping and incident wave characteristics in the present experimental campaign the effect of wave spreading has only been investigated for perpendicular wave attack results show that directional spreading is proved to cause a reduction of average discharge of sea dikes with gentle and shallow foreshore expressions for the reduction factor for directional spreading are derived fitted on the tested database the use of this reduction factor leads to more accurate prediction and avoids overtopping overestimation however reduction factor formulations are overtopping formula depending

low friction and fault weakening revealed by rising sensitivity of tremor to tidal stress at subduction zones deep parts of the fault can slip slowly generating tremor analysis of tremor in cascadia reveals increasing sensitivity of slip to tidal stresses over several days implying that the fault is weak and weakens as it slips

undrained poroelastic response of sandstones to deviatoric stress change deformation of porous crustal rock through diagenesis tectonic loading or other processes can change pore volume and affect fluid pressure the largest stress induced pore pressure changes occur when fluid is trapped in pores in an undrained condition we have measured the undrained poroelastic response of two sandstones to changes in mean and deviatoric stress pore pressure was found to respond to mean stress m in the usual manner p b m b ranging from 0 4 to 0 7 nearly independent of the ambient deviatoric stress state however variations in deviatoric stress d 1 3 2 at constant mean stress were also found to induce a reversible elastic pore pressure response to stress levels up to and exceeding 80 percent failure stress i e p d m const the coefficient became more negative with increasing deviatoric stress level in sandstone and ottawa sand samples that is represents a dilatant response where increased deviatoric stress causes a decrease in pore pressure the poroelastic response to deviatoric stress is explained in terms of anisotropic matrix stiffening due to closure of crack like pore space or flattening of grain contacts at high ambient stress levels and can be important in calculations of earthquake stress transfer

extreme coastal responses using focused wave groups overtopping and horizontal forces exerted on an inclined seawall abstract total wave group overtopping and maximum horizontal force responses are investigated for an idealised seawall dike on a plane beach subject to compact focused wave attack using both laboratory and numerical wave flumes the wave group interactions have very short durations such that extraneous reflections from the wavemaker arrive long after the main interaction these short test durations facilitate the use of large ensembles of tests to explore the sensitivity of overtopping and force responses to variations in focus location phase angle at focus and linear focus wave amplitude the scope of the laboratory wave flume tests is broadened by accurate numerical simulation based on a 1dh hybrid boussinesq nlsw model for a given focus location and linear focused wave amplitude variations in phase lead to an order of magnitude change in the group overtopping volume substantial increases in overtopping volume owing to the use of linear wavemaker theory compared to second order theory are also observed these observations have implications for phase independent empirical relationships derived using linear paddle signals in physical experiments examination of the incidence of wave groups parametrically optimised for maximum and minimum overtopping volumes indicates that the overtopping volume may be optimised by minimising reflections of pre overtopping waves within the group while maximising the amplitude of the first overtopping bore numerical predictions of horizontal seawall forces are obtained using fluid impulse derivatives and hydrostatic pressures obtained from the shallow water model within the shallow water model framework hydrodynamic force contributions included in the fluid impulse method are observed to be small relative to the hydrostatic pressure force the parametric dependence of the horizontal non impulsive forces on the seawall is very similar to that of the overtopping volumes with clear bands of large values observed as a function of phase and focus location for a given amplitude this suggests that the parametric optimisation of focused wave groups is a robust method for the investigation of multiple coastal responses such as overtopping forces and runup

swash overtopping on plane beaches reconciling empirical and theoretical scaling laws using the volume flux abstract existing empirical and theoretical models for swash overtopping are considered and reconciled by using the positive volume flux of the incident waves and the deficit in freeboard as scaling parameters this scaling holds for solitary waves monochromatic waves and random waves the empirical model of battjes 1974 the eurotop model eurotop 2016 and the theoretical model of peregrine and williams 2001 can all be written in terms of the positive volume flux with consistent coefficients this scaling can be rationalised physically by equating the positive volume flux to the volume of fluid displaced by a wavemaker the empirical exponential vertical scaling in eurotop is very similar to the empirical vertical scaling identified by battjes 1974 here it is shown that the latter can be rationalised theoretically from a simple ballistic swash model new experiments on swash overtopping a truncated plane beach are presented for monochromatic and random waves and shown to scale well with these two parameters data for equivalent smooth planar beaches from the clash database are compared to the new scaling with good agreement the influence of beach slope on overtopping has some uncertainty between the theoretical and empirical models and in the present data particularly for high deficit in freeboard as the truncation point approaches the still water line this is likely to be a result of different processes occurring in the surf and swash zones or over the subaqueous beach face and sub aerial beach face

effect of anisotropic consolidation stress paths on the undrained shear behavior of reconstituted wenzhou clay abstract naturally deposited clays are generally k0 consolidated in some cases such as embankment construction and foundation pit excavation the loading or unloading will lead to the re consolidation of clays which can be simulated by a simplified consolidation stress path with a certain ratio of vertical to horizontal consolidation stresses in this study a series of triaxial shear tests was conducted on a reconstituted wenzhou clay to investigate the effects of consolidation stress paths on the stress strain pore water pressure strain and effective stress path behaviors of overconsolidated samples based on the test results the shear strength and pore water pressure coefficient at failure are found to grow and reduce linearly with the increase of the ratio of vertical to horizontal consolidation stresses respectively more strain softening and shear dilation are observed for the anisotropically consolidated samples compared to isotropically consolidated ones the slope of failure line is approximately 1 25 for all specimens tested in this study

wave run up and overtopping reduction by block revetments with enhanced roughness abstract block revetments that are placed in special patterns in a way that lower standard sets are surrounded by sets of higher protruding units have been studied by means of physical model tests this paper focuses on prediction formulae for the wave run up and wave overtopping reduction by means of special pattern block revetments this reduction is significant and leads to lower crest levels of dikes reducing or limiting crest levels without reducing safety is often a preferred solution in areas where dikes form an integral part of the existing area and where raising dikes will lead to social drawbacks or a negative impact on the landscape

influence of oblique wave attack on wave overtopping at smooth and rough dikes with a berm abstract oblique wave attack can significantly reduce the amount of wave overtopping at coastal structures compared to perpendicular wave attack guidelines exist to estimate the influence of oblique waves on wave overtopping guidelines to estimate the influence of a berm in the seaward slope are also available these guidelines for the reducing effects of oblique waves and the reducing effects of a berm are frequently applied in combination although limited data is available for this combination of reducing effects to develop a method that can account for the reducing effects of oblique waves and a berm in the seaward slope of a dike physical model tests have been performed in a wave basin on structures with smooth and rough slopes based on these data wave overtopping guidelines for breaking waves on dikes have been validated and one of the guidelines has been extended to take the influence of oblique waves berms and roughness into account

anisotropic effective medium modeling of the elastic properties of shales shales are complex porous materials normally consisting of percolating and interpenetrating fluid and solid phases the solid phase is generally comprised of several mineral components and forms an intricate and anisotropic microstructure the shape orientation and connection of the two phases control the anisotropic elastic properties of the composite solid we develop a theoretical framework that allows us to predict the effective elastic properties of shales its usefulness is demonstrated with numerical modeling and by comparison with established ultrasonic laboratory experiments the theory is based on a combination of anisotropic formulations of the self consistent sca and differential effective medium dem approximations this combination guarantees that both the fluid and solid phases percolate at all porosities our modeling of the elastic properties of shales proceeds in four steps first we consider the case of an aligned biconnected clay fluid composite composed of ellipsoidal inclusion

strength of undisturbed versus reconstituted silt and silty sand specimens the differences in undrained stress strain strength behavior between undisturbed and reconstituted silt and silty sand specimens tested at the same void ratio and initial stress state may be dramatic in all tests reported herein the undisturbed specimens showed dilative and ductile behavior whereas in all but a very few cases the accompanying reconstituted specimens at the same or lower density showed contraction much lower undrained strength and brittle behavior the test series included samples from a natural fluvial silt deposit as well as from silty sand hydraulically placed in a tailings dam when reconstituting specimens for laboratory testing it is not sufficient to only satisfy the criteria of correct density and grain size distribution but somehow the same fabric also must be reproduced otherwise deformation and stability analyses based on the results of reconstituted specimens or on in situ tests calibrated against such results may be misleading most of the reconstituted specimens

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

earthquake induced liquefaction features in a late quaternary fine grained lacustrine succession fucino lake italy implications for microzonation studies abstract the fucino lacustrine basin in central italy is a large flat area mostly devoted to agriculture with urbanization along the perimeter of the ancient lake in 1915 a strong earthquake struck the area mw 7 0 producing large damages and geological effects including surface faulting ground failures and liquefaction a channel excavated in the lacustrine sediments exposed ground failure with dykes of fine grained sediment that we interpret as the result of earthquake induced liquefaction we present the results of a multidisciplinary work aimed at characterizing in detail the geology of the buried stratigraphic succession its susceptibility to liquefaction and the likely source of the fine grained liquefied material the succession down to 20 m deep is formed by fine grained sediments younger than 170 180 kyrs mostly late pleistocene holocene prevailingly silt or silt clay mixtures the geological field analysis indicates that the dykes are filled by prevailing silt liquefied and transported by upward directed flow of short duration as for earthquake induced liquefaction tilting and lateral spreading accompanied the process the overall liquefaction potential derived from the simplified methods is high correlations of x ray powder diffraction mineralogy of samples from drilling cores with those from dykes allowed us to identify the most likely source layer filling dykes corresponding to a silt layer at 7 8 m depths this layer and the dykes lack illite and montmorillonite clay particles these results contribute to improve studies of liquefactions in sediments that differ from typical liquefiable loose sands they have also implications for microzonation studies most samples show grain size curves that do not fit within the field of potentially liquefiable soils suggesting that criteria based on grain size can be poorly significant in seismic microzonation studies of recent late pleistocene holocene lacustrine fine grained successions

prediction formula for the spectral wave period t m 1 0 on mildly sloping shallow foreshores during the last decades the spectral wave period tm 1 0 has become accepted as a characteristic wave period when describing the hydraulic attack on coastal structures especially over shallow foreshores in this study we derive an empirical prediction formula for tm 1 0 on shallow to extremely shallow foreshores with a mild slope the formula was determined based on flume tests and numerical calculations mainly for straight linear foreshore slopes it is shown that the wave period increases drastically when the water depth decreases up to eight times the offshore value the bed slope angle influences the wave period slightly for short crested wave fields the strong increase of tm 1 0 starts closer to shore at smaller water depths than for long crested wave fields

wave overtopping of sea dikes with very shallow foreshores abstract wave overtopping is one of the key parameters for designing coastal structures the crest level is usually determined using admissible overtopping discharges several formulae already exist for wave overtopping assessment that predict the average overtopping discharge per meter width of the coastal defence generally for deep or intermediate water depths at the toe of the dike however the process of wave overtopping on sea dikes with shallow and very shallow foreshore is not yet fully understood gentle foreshores in combination with very shallow water conditions lead to heavy wave breaking and a significant change of the wave spectra from offshore to the toe of the dike the wave steepness is assumed as one of the main criteria to identify cases of severe wave breaking on shallow and very shallow foreshores for these conditions van gent s formula generally used for wave overtopping with shallow foreshores has been implemented and validated against experimental data it is the purpose of this paper to show that van gent s formula overestimates the average overtopping discharge for cases of very shallow foreshores moreover the existing formula cannot be applied to cases with an emergent toe the present work therefore introduces a new equivalent slope concept to obtain an estimation of average wave overtopping discharges on sea dikes with shallow and very shallow foreshores this study uses data from clash database and experimental campaigns specifically carried out at flanders hydraulics research belgium in order to validate this approach results indicate that this concept shows better performance compared to other empirical formulae which suggests that the influence of the very shallow foreshore on the average wave overtopping discharge should be included

in situ liquefaction resistance of clean sands over a wide density range the paper describes a method of obtaining undisturbed samples of saturated clean sand by freezing it in situ using a single freezer pipe tests have shown that the method can yield high quality samples that retain the density and the undrained cyclic strength of the sand in situ undrained cyclic triaxial tests were run on in situ frozen samples and on samples obtained with conventional tube samplers the liquefaction resistance of the frozen samples of clean sands correlates well with a normalized iv value of the standard penetration test over a wide range of tv values the in situ liquefaction resistance of the clean sands estimated from the results of the undrained cyclic tests on the frozen samples is consistent with a criterion based on field performance data during earthquakes for dense sands the samples obtained with the tube samplers are looser and much weaker than those obtained by the in situ freezing method the reverse is true for very loose sands the correlation between relative density an

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

the mechanics of a saturated silty loess and implications for landslides the results from an intensive experimental investigation on a loess that was retrieved from a typical silty loess zone in the north western chinese loess plateau are presented and interpreted triaxial and oedometer tests were performed on intact and reconstituted samples in a saturated condition the soil behavior was found to be strongly affected by structure the compression paths of the intact samples crossed the intrinsic compression line of the reconstituted soil and reached well defined gross yield points after which the compression paths converged towards the intrinsic compression lines two critical state lines were defined for the intact and reconstituted soils in the volumetric plane as a result of a robust element of natural structure comparisons were made with a structured clayey loess retrieved from the south eastern loess plateau it was found that the effects of structure on the behavior of the two loess soils are similar though they are very different in natural properties this indicates that their natural structures might have experienced similar forming processes perhaps related to their common origin catastrophic flowslides commonly occur in the study area and the patterns of behavior observed in the laboratory tests may create some new insights into mechanisms of landslide initiation and subsequent movement as discussed in the study

oblique wave attack on rubble mound breakwaters abstract stability formulae for armour layers of rubble mound breakwaters are usually being applied assuming perpendicular wave attack often the effects of oblique waves are neglected this is however a conservative assumption since the stability of armour slopes generally increases for oblique waves new wave basin tests have been performed to assess the effects of oblique waves on the stability of rock slopes and the stability of cube armoured rubble mound breakwaters the physical model tests were focussed on wave directions between perpendicular 0 and parallel 90 the test programme included tests with long crested waves and tests with short crested waves the results show that for rock slopes the influence of oblique waves is larger for long crested waves based on the test results a design guideline is provided to account for effects of oblique waves on the stability of rock slopes armour layers with a double layer of cubes and armour layers with a single layer of cubes

derivation of unified wave overtopping formulas for seawalls with smooth impermeable surfaces based on selected clash datasets a set of unified formulas for prediction of the mean rate of wave overtopping at coastal structures with smooth impermeable surfaces have been derived through the analysis of the selected clash datasets the mean wave overtopping rate is expressed as the function of the significant wave height at the structural toe and the relative freeboard the formulas are applicable for both vertical walls and inclined seawalls with smooth transition between them the formulas are simple but cover the full range of water depth from the shoreline to deep water the effects of the toe depth and the seabed slope on wave overtopping rate are duly incorporated in the formulas prediction performance of the new formulas is better than the eurotop formulas for both vertical walls and inclined seawalls

measured and modeled wave overtopping on a natural beach abstract the rate of wave overtopping of a barrier beach is measured and modeled unique rate of wave overtopping field data are obtained from the measure of the carmel river california lagoon filling during a time when the lagoon is closed off with no river inflow volume changes are based on measured lagoon height changes applied to a measured hypsometric curve wave heights and periods are obtained from directional wave spectra data in 15 m fronting the beach beach morphology was measured by gps walking surveys three empirical overtopping models by van der meer and janssen 1995 hedges and reis 1998 and pullen et al 2007 with differing parameterizations on wave height period and beach slope and calibrated using extensive laboratory data obtained over plane impermeable beaches are applied in a quasi 2d manner and compared with the field observations three overtopping events are considered when morphology data were available less than 2 weeks prior to the event the models are tuned to fit the data using a reduction factor to account for beach permeability berm characteristics non normal wave incidence and surface roughness influence in addition the run up model by stockdon et al 2006 based on field data is examined and found to underestimate run up as the calculated values were too small to predict any of the observed overtopping the three overtopping models performed similarly well with values of 0 72 0 87 for the two narrow banded wave cases with an average reduction factor of 0 78 the european model pullen et al 2007 performed best overall and in particular for the case of the broad banded double peaked wave spectrum

effective stress response of clay to undrained cyclic loading the effective stress response of a natural marine clay to slow undrained symmetrical cyclic reversal in shear stress is presented the effects of cyclic principal stress difference amplitude cyclic principal effective stress ratio amplitude initial direction of loading and step increase in cyclic stress level on the clay stress strain response are studied under stress conditions of the triaxial test characteristic behaviour patterns are identified in terms of effective stresses key words clay cyclic loading effective stress hysteretic work loading direction step loading

assessment of the liquefaction susceptibility of fine grained soils observations from recent earthquakes and the results of cyclic tests indicate that the chinese criteria are not reliable for determining the liquefaction susceptibility of fine grained soils fine grained soils that liquefied during the 1994 northridge 1999 kocaeli and 1999 chi chi earthquakes often did not meet the clay size criterion of the chinese criteria cyclic testing of a wide range of soils found to liquefy in adapazari during the kocaeli earthquake confirmed that these fine grained soils were susceptible to liquefaction it is not the amount of clay size particles in the soil rather it is the amount and type of clay minerals in the soil that best indicate liquefaction susceptibility thus plasticity index pi is a better indicator of liquefaction susceptibility loose soils with pi 0 85 were susceptible to liquefaction and loose soils with 12 0 8 were systematically more resistant to liquefaction soils with pi 18 tested at low effective confining stresses

dispersion and anisotropy of elastic waves in cracked rocks 1 rocks in the earth s crust contain variable amount of cracks depending on the deviatoric and confining stress levels pore pressure and temperature conditions crack damage results in effects that have been investigated for a long time in particular a decrease in elastic wave velocity and the development of anisotropy in this paper we focus on cracked rocks and develop a method to calculate both the elastic wave anisotropy and the dispersion in a fluid saturated cracked rock we show that analytic expressions can be derived for both properties in terms of the crack density tensor components two fundamental theoretical tools are used in this purpose the first one is the effective medium theory and the second one is the anisotropic poroelastic theory using both it is possible from first principles to predict anisotropy and dispersion results are shown to be valid up to a total crack density of 0 5 the failure threshold appears close to a total crack density of 1 between 0 5 and 1 the model still gives reasonably good results anisotropy can increase up to 60 and dispersion up to 30 depending on the crack distribution these results point out important differences that could exist in fluid saturated rocks between laboratory high frequency data and field low frequency results

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

pre and post cyclic behavior of mixed clayey soils soil structures are often comprised or supported by soils that are mixtures of cohesive and granular geomaterials these soils are termed as intermediate or mixed soils and are widely found in natu

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

effect of initial consolidation condition on postcyclic undrained monotonic shear behavior of mississippi river valley silt abstractthe postcyclic undrained monotonic shear behavior of mississippi river valley mrv silt is investigated by carrying out triaxial tests under various initial consolidation conditions results show that the variation of cyclic shear strength of mrv silt against initial overconsolidation ratio ocr and mean effective consolidation pressure c was consistent with previous studies i e it increased with both increase in ocr and decrease in c the cyclic stress ratio csr had no apparent effect on postcyclic shear behavior for mrv silt at higher ocrs the postcyclic reconsolidation behavior was more similar to recompression unlike the specimens not previously subjected to cyclic loading the initial ocr did not influence effective stress path of the postcyclic reconsolidated specimens at the early stages of shearing the normalized undrained shear strength su oc su nc of mrv silt reconsolidated after cyclic loading increased with ocr stress strain curves of mrv silt reconsolidated after c

injection induced seismicity poroelastic and earthquake nucleation effects the standard model of injection induced seismicity considers changes in coulomb strength due solely to changes in pore pressure we consider two additional effects full poroelastic coupling of stress and pore pressure and time dependent earthquake nucleation we model stress and pore pressure due to specified injection rate in a homogeneous poroelastic medium stress and pore pressure are used to compute seismicity rate through the dieterich 1994 model for constant injection rate the time to reach a critical seismicity rate scales with t r2 cfc where r is distance from the injector c is hydraulic diffusivity and fc is a factor that depends on mechanical properties and weakly on r the seismicity rate decays following a peak consistent with some observations during injection poroelastic coupling may increase or decrease the seismicity rate depending on the orientation of the faults relative to the injector if injection induced stresses inhibit slip abrupt shut in can lead to locally sharp increases in seismicity rate tapering the flux mitigates this effect the maximum magnitude event has been observed to occur postinjection we suggest the seismicity rate at a given magnitude depends on the nucleation rate the size distribution of fault segments and if the background shear stress is low the time varying volume of perturbed crust this leads to a rollover in frequency magnitude distribution for larger events with a corner that increases with time larger events are absent at short times but approach the background frequency with time larger events occurring post shut in are thus not unexpected

high modulus columns for liquefaction mitigation this paper presents the performance of a shopping complex in turkey where the soils were improved with jet grout columns and preload fills and subjected to the 1999 kocaeli earthquake m57 4 under construction at the time of the earthquake the carrefour shopping center covers an area of 55 000 m 2 and is founded on shallow footings mats and slabs on grade that rest on soft saturated alluvial sediments consisting of clays silts and sands high modulus columns constructed by jet grouting were installed at close to moderate spacings to reduce anticipated static settlements in the clays and mitigate liquefaction in the sands the site was subjected to a peak acceleration of approximately 0 2g during the earthquake grouting had been completed for about two thirds of the site when the earthquake struck following the event a field reconnaissance found stark contrast between the performance of the improved and unimproved sections the jet grout treated areas suffered no apparent damage whereas the unimproved sections of the complex along with nearby untreated building sites commonly suffered liquefaction related settlements of up to 10 cm this is the only case history known to the authors that documents the field performance of high modulus columns used in this manner for liquefaction mitigation and direct instrumented measurement of liquefaction induced settlements

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

void redistribution in sand under post earthquake loading a mechanism for void redistribution in an infinite slope under post earthquake loading conditions is described by consideration of the in situ loading paths that can occur under post earthquake conditions and the results of triaxial tests designed to represent specific in situ post earthquake loading paths the mechanism is illustrated by application to an example problem void redistribution is shown to be a phenomena that may be more pronounced at the field scale than at the laboratory scale key words liquefaction earthquake void redistribution triaxial sand

fourth avenue landslide during 1964 alaskan earthquake this paper presents a reevaluation of the fourth avenue landslide in anchorage that occurred during the 1964 alaskan earthquake laboratory constant volume ring shear and field vane shear tests were used to measure the undrained peak and residual shear strength of the bootlegger cove clay the results of these tests are presented and compared to back calculated shear strengths of the bootlegger cove clay the comparison shows that slide blocks that moved less than 0 15 m mobilized at least 80 of the undrained peak shear strength slide blocks that moved between 0 15 to 2 5 m mobilized an undrained shear strength between the peak and residual shear strengths slide blocks that displaced more than 2 5 m mobilized the undrained residual strength

influence of oblique wave attack on wave overtopping and forces on rubble mound breakwater crest walls abstract at the crest of rubble mound structures a crest wall is often present to reduce the consumption of material compared to breakwaters without a crest wall to design the crest wall several methods based on estimates of the hydraulic wave loads are available these methods are focussed on waves that approach breakwaters perpendicular in practice the dominant wave conditions are often not perpendicular but approach the breakwater under an angle oblique waves can significantly reduce the amount of wave overtopping and reduce the wave loads on coastal structures compared to perpendicular waves therefore physical model tests have been performed in a wave basin where the wave loads on crest walls and the wave overtopping discharges have been measured under oblique wave attack design guidelines have been developed to take the reduction due to oblique waves into account together with available methods to predict the wave forces and wave overtopping for perpendicular wave attack the obtained results enable a more advanced design of crest walls

laboratory measurements of a complete set of poroelastic moduli for berea sandstone and indiana limestone measurements have been completed for eight different poroelastic moduli of water saturated berea sandstone and indiana limestone as a function of confining pressure and pore pressure the poroelastic moduli for indiana limestone are generally consistent to 10 which was verified by a formal inversion procedure for independent moduli from the eight measurements for indiana limestone best fit values were drained bulk modulus 21 2 gpa the undrained bulk modulus 31 7 gpa drained poisson s ratio 0 26 undrained poisson s ratio 0 33 and pore pressure buildup coefficient 0 47 at 20 35 mpa effective stress the poroelastic moduli for berea sandstone are generally consistent to 20 the greater inconsistency is most likely caused by the nonlinear variation of the moduli at different strains for berea sandstone best fit values were drained bulk modulus 6 6 gpa undrained bulk modulus 15 8 gpa drained poisson s ratio 0 17 undrained poisson s ratio 0 34 and pore pressure buildup coefficient 0 75 at 10 mpa effective stress

efficient and robust wave overtopping estimation for impermeable coastal structures in shallow foreshores using swash abstract estimation of wave overtopping over the crest of coastal structures is crucial to design effective and cost efficient countermeasures against storms semi empirical formulas are often used for wave overtopping assessment but they are not always applicable for complex structures which exist in reality e g a storm wall on a dike in a shallow or very shallow foreshore detailed numerical models such as eulerian and lagrangian rans models have potential to simulate overtopping of complex coastal structures with good accuracy however such models require significant computational resources the use of such models is often not feasible for the design of coastal structures which often requires multiple iterations and model runs over a reasonably long period of time e g wave trains with 1000 individual waves in this paper we investigated the applicability of the simplified depth integrated wave transformation model swash for wave overtopping estimation of impermeable coastal structures in shallow foreshores the validation results demonstrate the capability of swash to predict mean wave overtopping discharge with good accuracy compared to results from four different overtopping experimental campaigns comprising 124 individual cases the overall performance of swash to estimate mean wave overtopping discharge is as accurate as those obtained by semi empirical equations in literature however in order to obtain accurate mean wave overtopping discharge with the swash model the incident wave properties at the toe of the dike need to be accurately reproduced for cases where this is not possible a correction method is proposed in this paper detailed validation of the instantaneous wave overtopping also shows a good agreement with physical model data in one example a single intensive overtopping event was not well resolved by the swash model and the instantaneous wave overtopping was under predicted however this did not contribute significantly to the mean wave overtopping discharge an additional advantage of the swash model is that specific coastal structure geometries can be modelled in swash if they are not covered by semi empirical equations even in a case with rapidly varied flow e g vertical wall on a dike the model shows sufficient robustness in this paper the details on the swash model configuration and post processing methods are outlined to enable the reader to reproduce reliable wave overtopping estimation over impermeable coastal structures in shallow foreshores

behavior of a fine grained soil during the loma prieta earthquake results of an investigation into the behavior of a fine grained clayey soil at moss landing during the 1989 loma prieta earthquake are presented a deposit of this soil underlies portions of the mo

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

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

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

examination of the influence of several factors on longshore current computation with random waves abstract influence of various factors affecting the longshore currents induced by obliquely incident random waves is examined through numerical calculation seven numerical models for random wave breaking process are found to yield large differences in the wave heights in the surf zone and longshore current velocities the turbulent eddy viscosity formulation by larson and kraus larson m and kraus n c 1991 numerical model of longshore current for bar and trough beaches j waterway port coastal and ocean eng asce 117 4 pp 326 347 functions almost equal to that by battjes battjes j a 1975 modeling of turbulence in the surf zone proc symp modeling techniques pp 1050 1061 but the formulation by longuet higgins longuet higgins m s 1970 longshore current generated by obliquely incident sea waves 1 and 2 j geophys res 75 33 pp 6779 6801 produces excessive diffusion of longshore currents into the offshore zone the generation and decay process of the surface roller is indispensable in the longshore current analysis the random wave transformation model called pegbis parabolic equation with gradational breaker index for spectral waves by goda goda y 2004 a 2 d random wave transformation model with gradational breaker index coastal engineering journal jsce and world scientific 46 1 pp 1 38 produced good agreement with several laboratory and field data of longshore currents

postcyclic degradation of strength and stiffness for low plasticity silt stress controlled undrained cyclic triaxial tests followed by strain controlled monotonic compressive shear tests were carried out on normally consolidated and overconsolidated reconstituted keuper marl silt to investigate the strength and stiffness degradation characteristics of a low plasticity silt special attention was paid to the changes in undrained strength and deformation modulus after undrained cyclic loading it was observed that cyclic degradation in stiffness for low plasticity silt is more marked than that of strength and this tendency increases with increasing overconsolidation ratio it was found that a previously proposed model for predicting postcyclic degradation in strength and stiffness of normally consolidated fine grained soils could be applied to that of overconsolidated silt but not however to the postcyclic degradation in young s modulus thus an attempt was made to correlate postcyclic degradation of overconsolidated silt to the equivalent cyclic shear strain instead of the normalized excess pore pressure it was concluded that cyclic shear strain was a better parameter than cyclic induced excess pore pressure for correlating the postcyclic stiffness degradation not only for normally consolidated but also for overconsolidated silt

liquefaction and flow failure during earthquakes two aspects of seismically induced liquefaction are discussed which are of vital engineering significance the triggering condition and the consequences of liquefaction the triggering condition is examined with respect to liquefaction analysis note being taken of the onset condition which is governed by cyclic strength consequences of liquefaction are discussed with respect to post seismic stability analysis in which the residual strength plays a major role procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced and the applicability of this method for estimating associated ground settlements is discussed the evaluation of residual strength requires a better understanding of undrained sand behaviour results of extensive laboratory rests on japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better the results of laboratory tests on silty sands are examined in the same way ah the results are

liquefaction susceptibility criteria for silts and clays new liquefaction susceptibility criteria for saturated silts and clays are presented that are based on the mechanics of their stress strain behavior and which provide improved guidance for selecting engineering procedures for estimating potential strains and strength loss during seismic loading monotonic and cyclic undrained loading test data for silts and clays show that they transition over a fairly narrow range of plasticity indices pi from soils that behave more fundamentally like sands sand like behavior to soils that behave more fundamentally like clays clay like behavior with the distinction having a direct correspondence to the type of engineering procedures that are best suited to evaluating their seismic behavior it is recommended that the term liquefaction be reserved for describing the development of significant strains or strength loss in fine grained soils exhibiting sand like behavior whereas the term cyclic softening failure be used to describe similar phenomena in fine grained soils exhibiting clay like behavior for practical purposes clay like behavior can be expected for fine grained soils that have pi 7 although a slightly lower transition point for soils with a cl ml classification perhaps pi 5 or 6 would be equally consistent with the available data issues related to the practical application of these criteria are discussed