geotechnical and geological properties of mokattam limestones implications for conservation strategies for ancient egyptian stone monuments abstract geotechnical and geological properties of limestone samples from the mokattam quarry in cairo egypt were determined in order to provide prior information for the selection of suitable methods for the conservation of stone monuments around cairo a commercial chemical consolidant wacker oh 100 was applied to fill the pore spaces and to strengthen the weathered rock filling of pore spaces was confirmed by the decrease of both porosity and permeability of rock samples after the application of the consolidant analysis by mercury porosimeter showed most effective consolidation results for pore spaces from 0 75 to 1 0 m in diameter which were those mainly observed in the samples ultrasonic velocity did not show any significant evidence but an increase in strength observed as an increase in the point load index after the consolidation process was completed confirmed that the filling and consolidation process worked effectively point load testing can thus be used in preference when the number of samples available for laboratory testing is limited from the color analysis it was shown that there was no noticeable color change after the application of consolidant wacker oh 100 the combinations of laboratory tests adopted in this study can be applicable to the planning of conservation of other stone monuments

pore properties as indicators of breakdown mechanisms in experimentally weathered limestones the results are reported of four experimental weathering tests freeze thaw wetting and drying slake durability and salt weathering on five different types of limestone effective porosity mercury intrusion porosimetry and scanning electron microscopy were used to evaluate changes in pore properties while weight loss and fracture density were used to assess deterioration severity a primary aim was to observe modifications in porosity due to weathering and to draw inferences about the internal rock deterioration mechanisms taking place it is concluded that the five limestones not only show a wide range of resistance to weathering in general but considerable difference in resistance to particular weathering processes consequently when assessing durability it is essential to consider rock properties in the context of the weathering process to which the rock is subject the type of deterioration indicator used is also important in interpretation of durability a variety of pore modification mechanisms operate including changes in pore connectivity pore infilling and the introduction of additional void space there are indications that changes to the internal pore structure of rocks due to weathering may be a precursor to more substantial macrodeterioration copyright 2001 john wiley sons ltd

unravelling the development of a spheroidally weathered diorite gabbro santa margarita ecological reserve peninsular ranges southern california usa abstract within santa margarita ecological reserve smer southern california an 108 ma diorite gabbro pluton has weathered spheroidally resulting in the formation of concentric rindlets i e a rindlet zone around an unaltered ellipsoidal core of the parent rock to our knowledge little is known about how spheroidal weathering is produced in mediterranean climates like that characteristic of portions of the peninsular ranges hence we undertook a detailed study aimed at determining the textural and chemical changes associated with the spheroidal weathering of the diorite gabbro pluton the parental spheroidally weathered corestone is characterized by a hypidomorphic granular texture and consists primarily of plagioclase amphibole and biotite along with minor amounts of pyroxene and quartz within the corestone sericite and uncommonly calcite and chlorite replace plagioclase the latter mineral also infrequently replaces portions of amphibole and biotite such alteration products are derived from sub solidus deuteric alteration of the pluton xrd clay mineral analysis of the 13 rindlets indicates the presence of mostly kaolinite and vermiculite and a far lesser volume of green smectite thin section study of rindlet samples suggests that vermiculite is derived from the weathering of biotite the most extensively altered mineral in the rindlet zone such alteration is paralleled by statistically significant losses of k mass across the rindlet zone in addition statistically significant losses of ca and na mass across the rindlet zone likely reflect conversion of sericite to kaolinite in contrast the absence of statistically significant losses of mg fe and mn over most of the rindlet zone implies that fluids were mostly oxidizing and that any mg leached from amphibole was likely fixed within smectite while leached fe and mn precipitated out as oxides or oxyhydroxides though calcite was present in the corestone its absence in the rindlets indicates that fluids were sufficiently acidic to dissolve and remove it previous studies have shown that spheroidal weathering occurs when volume expansion produced by a positive v of reaction builds up internal elastic strain energy in the rock for example this type of reaction occurs when iron oxidizes within biotite resulting in an expansion of d 001 from 10 a to 10 5 a or when biotite is transformed into vermiculite leading to an expansion of d 001 from 10 a to 14 a data presented here suggest that the conversion of biotite to vermiculite and the resulting positive v produced the spheroidal fracturing of the corestone at smer hence these and other data discussed in this paper suggest that the weathering of biotite is the primary driving force in the formation of spheroidally weathered corestone in the mediterranean climate of the peninsular ranges

deep weathering of a group of thick argillaceous limestone rocks near three gorges reservoir central china rock mass characterization is one of the most basic and important tasks in rock mechanics and engineering literature review indicates that although there are many publications available on weathered rocks there are few reports in english on weathered argillaceous limestone rocks and their chemical and mechanical properties this paper presents a case study of characterizing a group of highly weathered thick argillaceous limestone rocks most importantly they can be easily and quickly decomposed into soils after they are exposed due to excavation consequently they would substantially lose their mechanical strengths geohazards such as landslides and sinkholes could occur in uncovered highly weathered argillaceous limestone rocks the problematic weathered rocks were found during the development of a new town in upper mountains above the three gorges reservoir on yangtze river in central china in the past 20 years the factual data are presented on the changes of chemical compositions and mechanical properties of the weathered argillaceous limestone rocks due to chemical weathering some empirical correlations are given to quantify the changes in their uniaxial compressive strength and deformation moduli in terms of their contents of calcium carbonate the data and findings presented in the paper can be useful to future urban development in geologically poor mountainous environments occupied by highly weathered argillaceous limestone rocks in the world

application of protective products to noto calcarenite south eastern sicily a case study for the conservation of stone materials noto is an important baroque urban center in south eastern sicily which was completely reconstructed after the severe earthquake of 1693 most of its monuments and historic buildings were built in pietra di noto stone a pale cream calcarenite quarried in outcrops located near the city this stone still currently used as building material is undergoing many forms of alteration and degradation which cause significant damage to monuments in this study three commercial protective products were tested on some noto calcarenite samples from quarries with the aim of assessing their protective effectiveness in particular petrographic analyses by optical microscopy were carried out for textural characterization of the stone materials capillary water absorption porosimetric and colorimetric procedures uv radiation and salt crystallization aging tests were performed to better evaluate interactions between protective products and substrate

effects of consolidation under a penetrating footing in carbonate silty clay abstractthe effects of consolidation under a footing are generally viewed as beneficial due to the resulting increased capacity consolidation may also be actively sought because it minimizes footing embedment which can be critical for the installation of mobile offshore jack ups because available leg length is limited however it can also set the platform footing up to subsequently punch through the strengthened zone with potentially serious consequences the problem is complex due to the three dimensional nature of consolidation further footing penetration leaves the soil above heavily remolded and generates large excess pore pressures below such that the soil state even prior to consolidation is significantly altered from its in situ conditions this study has taken an experimental approach to investigate the effects of consolidation around a footing penetrating into carbonate silty clay and following detailed discussion of the response offers a framework to predict the changes to the load pene

predicting peak resistance of spudcan penetrating sand overlying clay abstractaccurately predicting peak penetration resistance qpeak during spudcan installation into sand overlying clay is crucial to an offshore mobile jack up industry still suffering regular punch through failures this paper describes a series of spudcan penetration tests performed on medium loose sand overlying clay and compares the response to existing centrifuge data from tests performed on dense sand overlying clay together these data demonstrate that punch through is a potential problem for both dense and loose sand overlying clay soil stratigraphies using this experimental database a failure stress dependent model has been modified to account for the embedment depth and the depth of occurrence of qpeak is shown to be a function of the sand thickness hs the model then was recalibrated taking these findings into account for a larger range of material properties and ratios of sand thickness to spudcan diameter hs d finally the performance of the modified and recalibrated model is verified b

weathering of the oporto granite geotechnical and physical properties abstract this paper characterizes the weathering products of the two mica oporto granite in terms of its mineralogical chemical geotechnical and physical properties this information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties in outcrop the oporto granite is always weathered and weathering profiles frequently exceed 20 m within these profiles granitic saprolites are composed of quartz feldspars and some mica with kaolinite and gibbsite as final weathering products the average percentage of secondary minerals determined by bulk x ray diffraction xrd is low in both weathered rock 2 4 and saprolite 8 7 geotechnically the saprolites exhibit no or low plasticity plasticity index pi 12 the skeleton character of the saprolites is reflected in the significant proportion of fines 29 5

rbsr glauconite ages sabinian claibornian and jacksonian units southeastern atlantic coastal plain u s a abstract hand picked disordered to ordered authigenic glauconite from the nanjemoy formation virginia the santee limestone restricted and cross formation south carolina and the castle hayne limestone north carolina yield rb sr isochron ages 87rb 1 42 10 11 yr 1 for eocene units in the southeastern atlantic coastal plain the units zonal assignment of their contained nannofossil floras and radiometric age are 3 unit nannofossil zone age m y castle hayne limestone np 19 20 34 9 1 1 cross formation np 18 np 19 np 20 34 1 1 5 santee limestone upper part np 16 17 36 7 0 6 nanjemoy formation np 13 46 7 3 0 these ages and their nannofossil assemblages provide means of correlating southeastern atlantic coastal plain units with gulf coastal plain and european stratoypes correlation to gulf coast stratotypes based on nannofossil zones indicates that the nanjemoy formation in part is equivalent to the hatchetigbee formation the upper part of the santee limestone restricted is equivalent to the upper lisbon formation the gosport sand and the moodys branch formation upper claibornian lower jacksonian and the cross formation and the castle hayne limestone are equivalent to the yazoo group jacksonian previously reported k ar glauconite ages for the gulf coast units are different from the rb sr ages determined in this study as the rb sr age determinations show internal consistency when compared to their contained nannofossil zones whereas the k ar ages do not it is suggested that the previously reported k ar ages for the gulf coast claibornian and jacksonian are in error correlation of the southeastern atlantic coastal plain units to european stratoypes based on nannofossil zones indicates that the nanjemoy formation in part is equivalent to the type lutetian the upper part of the santee limestone restricted is equivalent to the upper bracklesham and barton beds and the cross formation and castle hayne limestone are equivalent to the lower and middle headon beds previously determined k ar and rb sr radiometric ages for the type lutetian the bracklesham and barton beds are identical to the ages determined in this study as a result it is suggested that rb sr glauconite isochron ages can be used for regional and inter regional correlation and that the eocene oligocene boundary is younger than 34 m y

generic transformation models for some intact rock properties a global intact rock database of nine parameters including uniaxial compressive strength and young s modulus is compiled from 184 studies this database labeled as rock 9 4069 consists of 27

using a thin sand layer to ease spudcan extraction in clay difficulties are encountered in soft clay and silt sediments during extraction of the spudcan foundations of mobile jack up rigs this paper reports results from centrifuge model tests undertaken to provide a simple effective and practical means for easing spudcan extraction in soft normally consolidated and lightly overconsolidated clay the tests were carried out on model spudcans of two different geometries typically used in the field the spudcans were extracted from penetrations of 2 3 diameters and after an operation period of 19 months the measured pore pressure at the bottom face of the spudcan during extraction process provided insight into the development of suction at the interface between the spudcan base and the underlying soil the tests were carried out with and without a sand layer placed locally in between the spudcan and the mudline at the onset of penetration in the field a gravel layer can be placed by means of a flexible fall pipe system the presence of a sand layer with a

origin of abundant moonmilk deposits in a subsurface granitic environment subsurface granitic environments are scarce and poorly investigated a multi disciplinary approach was used to characterize the abundant moonmilk deposits and associated microbial communities coating the granite walls of the 16th century paranhos spring water tunnel in porto city north west portugal it is possible that this study is the first record of moonmilk in an urban subsurface granitic environment the morphology and texture mineralogical composition stable isotope composition and microbial diversity of moonmilk deposits have been studied to infer the processes of moonmilk formation these whitish secondary mineral deposits are composed of very fine needle fibre calcite crystals with different morphologies and density calcified filaments of fungal hyphae or bacteria were distinguished by field emission scanning electron microscopy stable isotope analysis revealed a meteoric origin of the needle fibre calcite with an important contribution of atmospheric co2 soil respiration and hco3 from weathering of ca bearing minerals the dna based analyses revealed the presence of micro organisms related to urban contamination including actinobacteria mainly represented by pseudonocardia hispaniensis thaumarchaeota and ascomycota dominated by cladosporium this microbial composition is consistent with groundwater pollution and contamination sources of the overlying urban area including garages petrol stations and wastewater pipeline leakage showing that the paranhos tunnel is greatly perturbed by anthropogenic activities whether the identified micro organisms are involved in the formation of the needle fibre calcite or not is difficult to demonstrate but this study evidenced both abiotic and biogenic genesis for the calcite moonmilk in this subsurface granitic environment this article is protected by copyright all rights reserved

salt weathering influence of evaporation rate supersaturation and crystallization pattern micro and macroscale experiments which document the dynamics of salt damage to porous stone have yielded data which expose weaknesses in earlier interpretations previously unexplained differences are found in crystal morphology crystallization patterns kinetics and substrate damage when comparing the growth of mirabilite na2so4 10h2o and thenardite na2so4 versus halite nacl the crystallization pattern of sodium sulphate was strongly affected by relative humidity rh while a lesser rh effect was observed for sodium chloride macroscale experiments confirmed that mirabilite crystallizing at rh 50 per cent and thenardite crystallizing at rh 50 per cent tend to form subflorescence in highly localized areas under conditions of constant rh and temperature this crystallization pattern was more damaging than that of halite since halite tended to grow as efflorescence or by filling the smallest pores of the stone in a homogeneous fashion a result which contradicts wellman and wilson s theoretical model of salt damage low rh promoted rapid evaporation of saline solutions and higher supersaturation levels resulting in the greatest damage to the stone in the case of both sodium sulphate and sodium chloride crystallization at any particular crystallization condition sodium chloride tended to reach lower supersaturation levels resulting in the crystallization of isometric crystals and created negligible damage while sodium sulphate reached higher supersaturation ratios resulting in non equilibrium crystal shapes resulting in significant damage esem showed no damage from sodium sulphate due to hydration instead after water condensation on thenardite crystals rapid dissolution followed by precipitation of mirabilite took place resulting in stone damage by means of crystallization pressure generation it is concluded that salt damage due to crystallization pressure appears to be largely a function of solution supersaturation ratio and location of crystallization these key factors are related to solution properties and evaporation rates which are constrained by solution composition environmental conditions substrate properties and salt crystallization growth patterns when combined with a critical review of salt damage literature these experiments allow the development of a model which explains variations in damage related to combinations of different salts substrates and environmental conditions

chemical and mineralogical characterisation of weathered historical bricks from the venice lagoonal environment surficial and bulk samples of historical bricks of different age from xii to xviii centuries recovered from a campaign of archaeological excavations recently carried out at the site of a medieval monastery in the s giacomo in paludo island in thevenice lagoon have been characterised by ft ir tga dtg and dta xrd sem eds the samples belong to a particular brick type commonly used in the venice region the altinella brick the bulk relative abundance of primary i e calcite and dolomite and secondary firing minerals i e diopside and wollastonite in the bricks coupled with their relative geometrical dimensions allows placing the samples in a chronological sequence according to known historical changes in brickmaking firing temperatures and practices most of the bricks were used as paving material and have been exposed to the action of seawater salts chlorides and sulphates due to periodical submersion following high tide episodes salt laden gypsum halite mirabilite surficial patinas are indeed present but salt weathering does not appear to have affected the overall structural soundness of the bricks in this now abandoned island as it is the case with brickwork located in other more populated and polluted areas in venice and its lagoon

predicting the resistance profile of a spudcan penetrating sand overlying clay assessment of the risk of punch through failure of spudcan foundations on sand overlying clay requires prediction of the full penetration resistance profile from touchdown and through punch through to equilibrium of the vertical resistance at depth in the underlying clay layer this study uses the coupled eulerian lagrangian approach a large deformation finite element analysis method to model the complete penetration resistance profile of a spudcan on sand overlying clay the sand is modeled using the mohr coulomb model while the clay is modeled using a modified tresca model to account for strain softening the numerical method is then used to simulate a series of spudcan penetration tests performed in a geotechnical centrifuge on medium dense sand overlying clay the punch through behavior observed in the experiments is replicated and the penetration resistance profiles from numerical analyses are generally a reasonable match to the experimental measure ments the influences of the sand layer height to foundation diameter ratio sand clay interface shear strength and strength gradient in clay on the penetration resistance profiles are explored in a complementary parametric study the penetration resistance in the underlying clay layer is well predicted using a simple linear expression for the bearing capacity factor for the spudcan and underlying sand plug this expression is combined with an existing failure stress dependent model for predicting peak resistance to form a simplified method for prediction of the full penetration resistance profile this new method provides estimates of the vertical penetration that the spudcan will run during the punch through event it is validated against both medium dense and dense sand centrifuge tests

biogenic mn oxide minerals coating in a subsurface granite environment abstract this paper reports the results of a study of biogenic mn oxide minerals coating in a subsurface granite environment this subterranean environment corresponds to galleries of a 16th century spring water tunnel dug throughout the granite bedrock located in porto city nw portugal several techniques xrd ftir raman icp ms tem eds fesem eds stem eds and stxm nexafs were used to assess the mechanisms involved in the formation of manganese oxides specifically birnessite and todorokite these manganese oxides presented peculiar shapes nano dimensions low degree of crystallinity and high levels of some trace elements such as p ca c al si ba and zn they were associated with large amounts of extracellular polymeric substances exuded by filamentous bacterial communities which serve as nuclei for preferential precipitation of manganese oxides on the extracellular sheaths scientific assessment revealed that biological activity played a major role in the development of these manganese oxides

numerical investigation of spudcan penetration in multi layer deposits with an interbedded sand layer for calculating spudcan penetration resistance in an interbedded sand layer between two clay layers the recently developed mechanism based design methods for surface sand over clay deposits are extended to account for the influence of the overlying clay layer a series of large deformation finite element ldfe analyses were carried out varying layer geometries and strength parameters the numerical results and existing centrifuge test data are used to calibrate the extended design methods the performance of the modified design methods and those suggested in the iso standard 19905 1 is compared confirming the accuracy of the former methods in estimating the peak penetration resistance in the sand layer ldfe analyses were also carried out adding a strong fourth layer with the corresponding effects on the increasing peak resistance in the second sand layer and squeezing behaviour or limiting squeezing depth in the third soft clay layer discussed design formulas are also developed to estimate th

lithostratigraphy of shell 272 1 and 273 1 wells implications as to depositional history of baltimore canyon trough mid atlantic ocs geologic note upper jurassic gray and red brown shale sandstone and coal are the oldest strata penetrated by the shell 272 1 and 273 1 wells located approximately 66 mi 106 km southeast of atlantic city new jersey in the northwest part of the baltimore canyon trough the lower cretaceous section consists of gray shale that is overlain by a sequence of thick bedded sandstones interbedded with thin bedded shales the upper cretaceous section is dominated by slightly calcareous mudstone but also contains a coniacian to campanian sandstone the cenozoic section is mainly mudstone and overlying unconsolidated sand seven major lithologic units were established and correlated to the cost b 2 and b 3 wells the depositional environments of the upper jurassic rocks range from an upper delta plain facies penetrated in the two shell wells and the b 2 well to a back reef facies penetrated in the b 3 well the lower cretaceous strata in a vertical sequence consist of upper delta plain lower delta plain interdistributary bay and or marginal marine and distributary mouth bar deposits a cenomanian sandstone penetrated in the b 3 well is the youngest indicator of deltaic deposition marine strata dominate the remainder of the upper cretaceous and cenozoic

on the variations of geo engineering properties of dunites and diorites related to weathering geo engineering properties of rocks including discontinuity properties physical and mechanical properties and crack propagation under axial loads are affected by weathering all of these rock properties have an impact on various scales on engineering applications therefore weathering related variations on rocks and rock masses are of great importance in this study dunites and diorites are compared from the view of weathering related geo engineering property variations both on field and on laboratory scales the studies were initiated in the field by measuring the discontinuity properties including spacing aperture fill material roughness and schmidt hammer rebound tests mineralogical and petrographic investigations were performed on thin sections gathered from different weathering grades the quantitative petrographic studies were concentrated on the micropetrographic index and the quantification of microcracks at this stage of the study a new method to quantify microcracks was proposed basic physical and mechanical properties e g specific gravity dry and saturated unit weights water absorption effective porosity p wave velocity uniaxial compressive strength and slake durability index test were also investigated on samples of all of the weathering grades where the sample preparation was available the data obtained from the field studies suggest that dunite discontinuity spacing decreases from 577 to 1 cm and ranges from 487 to 1 cm for diorite schmidt hammer rebound test values shv in the field were only obtained for fresh slightly weathered and moderately weathered grades shv values range from 54 to 41 for dunite and 63 to 32 for diorite the quantitative microcrack data obtained during the petrographic studies indicated that microcracks for diorite increase with increasing weathering but a decrease was observed for dunite which was related to the formation of serpentine minerals with weathering furthermore with increasing weathering the changes in the physical properties of dunite specimens exhibit a wider range than in the diorite specimens unconfined compressive test results for the rocks showed similar decreasing trends with weathering but the dunite specimen started to slake by the highly weathered stage where the diorite exhibited a considerable slaking by the completely weathered stage this research concludes that the micropetrographic index and quantitative microfracture data provide useful input to recognize the weathering grades of studied rocks it is also emphasized that serpentinization is the distinct process for dunite weathering and has a high impact on the weathering process influencing physical and mechanical properties considerably however the increase of micro and macrocracks is the dominant distinctive feature for diorite weathering

bayesian prediction of peak resistance of a spudcan penetrating sand over clay assessing the potential for a punch through failure during spudcan installation in sand over clay is crucial for reducing risk in the operations of mobile jack up platforms typically in the offsh

behaviour of li isotopes during regolith formation on granite massif central france controls on the dissolved load in water saprolite soil and sediment abstract lithium li contents and isotopes were studied in all environments of a small river catchment draining granite in the margeride mountains of the french massif central this covered surface waters primary and accessory minerals of the granites the whole rock and soil and sediment samples developed in the catchment completed with regional data for mineral waters and rainwater the integrated investigation aimed at evaluating the potential of li isotopes as effective tracers of water rock interaction processes within a granitic environment the 7li values and li concentrations were measured on sediment and soil samples following standard acid dissolution procedures and chemical purification of li using the cationic exchange resin protocol in a clean lab lithium isotope compositions were measured with a neptune mc icp ms and li concentrations by icp ms the samples represented different stages of granite weathering including fresh granite weathered rock surface saprolite and sediments in riverbanks and fields bordering the streams the extent of li mobility during granite weathering was first evaluated through determining the percentage change relative to ti with a range from 31 to 66 in the collected samples the weathered rock was depleted by 47 for li with negative 7li values ranging from 1 9 to 3 4 soil to riverbank sediment samples were characterized by less negative 7li values indicating that li is enriched in soil with fractionation of li isotopes and changes of the mineral abundance in the samples to complement this first view we i modelled the theoretical li isotope signature of water interacting with granite using a weathering model based on dissolution ii applied an atmospheric input correction to surface waters iii applied a raleigh equation for modelling the li isotope fractionation when compared with corrected surface water and mineral water and iv compared li isotopes with sr isotope data in a larger weathering framework

the development and application of the alteration strength index equation abstract we have developed an alteration strength index asi equation to address the effect of hydrothermal alteration on mechanical rock properties this equation can be used to estimate a range of rock strengths comparable to uniaxial compressive strength ucs based on rapid analysis of mineralogy and microstructure we used rock samples from three geothermal fields in the taupo volcanic zone tvz to represent a range of alteration types these are sedimentary intrusive and extrusive rocks typical of geothermal systems from shallow and deep boreholes 72 measured depth md to 3280 md the parameters used in asi were selected based on literature relating these aspects of mineralogy and microstructure to rock strength the parameters in asi define the geological characteristics of the rock such as proportions of primary and secondary mineralogy individual mineral hardness porosity and fracture number we calibrated the asi against measured ucs for our samples from the tvz to produce a strong correlation r2 of 0 86 and from this correlation we were able to derive an equation to convert asi to ucs because the asi ucs relationship is based on an empirical fit the ucs value that is obtained from conversion of the asi includes an error of 7 mpa for the 50th percentile and 25 mpa for the 90th percentile with a mean error of 11 mpa a sensitivity analysis showed that the mineralogy parameter is the dominant characteristic in this equation and the asi equation using only mineralogy can be used to provide an estimated ucs range although the error or uncertainty becomes greater this provides the ability to estimate strength even when either fracture or porosity information are not available for example in the case of logging drill cuttings this research has also allowed us to provide ranges of rock strengths based solely on the alteration zones mineralogy and depth of lithologies found in a typical geothermal field that can be used to update conceptual models of geothermal fields

paleogene calcareous nannofossil biostratigraphy of the atlantic coastal plain abstract reconnaissance nannofossil sampling of outcrops well cuttings and cores from new jersey to north carolina reveals strata representative of the entire paleogene except for np 3 and np 24 25 lowest paleocene strata np 1 2 occur in the subsurface of central new jersey and equivalents may exist in north carolina mid to upper paleocene beds np 5 9 occur in central new jersey virginia and north carolina cropping out as the vincentown aquia and beaufort formations respectively lower eocene assemblages appear to occur only in the subsurface of virginia where a section representing continuous open marine deposition from np 4 5 to np 23 exists middle eocene strata np 14 17 occur in new jersey delaware maryland virginia and north carolina whereas upper eocene beds are represented only in virginia and north carolina the virginia section is mainly clastic whereas that of north carolina seems to represent wave influenced carbonate banks exhibiting several hardgrounds castle hayne formation nannofossil assemblages of np 15 and np 18 20 but not np 16 17 suggest that the castle haynes formation might represent two separate marine transgressions separated by a hiatus lower oligocene assemblages np 21 22 were found only in the subsurface of virginia and north carolina and mid oligocene ones only in virginia samplings of the atlantic coast onshore sequence is continuing and undoubtedly some of the many apparent marine hiatuses we encountered might be filled in nonetheless the lower paleocene upper paleocene middle eocene and lower oligocene appear to represent marine transgression whereas the middle paleocene lower and upper eocene and upper oligocene represent marine regressions these oscillations correlate well with global relative sea level history but differ in detail owing to local tectonic overprinting

causes of scaling on bush hammered heritage ashlars a case study plaza mayor of madrid spain masons have traditionally used granite anisotropy to cut and lay the stone scaling a common type of granite decay is observed worldwide this study explored the relationship between weathering and cut planes in heritage ashlars specifically in the stone on madrid s plaza mayor whose construction dates back to 1590 the 71 rectangular granite columns that support its porticoes are oriented towards the four cardinal points all 71 have one exposed side that faces the square one protected side facing inward and two semi protected sides perpendicular to the other two the sides of the columns are also oriented to the points of the compass this study aimed to identify the prevailing orientation of scaling if any in the granite ashlars and to determine how this process is affected by climate microclimate orientation use hewing and exfoliation microcracks all four sides of the 71 columns were mapped 284 in all to analyse scaling height distribution and orientation the findings showed that the microcracks are vertically oriented and decline in density and length with depth from the surface scaling was observed on the lower ashlars in the columns to a maximum depth of 3 mm determining the direction of exfoliation microcracks is imperative to understanding decay mechanisms in granite ashlars and sculptures and that information must be taken into consideration when applying conservation treatments

random finite element method for spudcan foundations in spatially variable soils abstract spudcans are large diameter 20 m conical foundations holding up mobile jack up platforms for offshore oil and gas developments in shallow to moderate water depths during self installation the spudcan often penetrates several tens of meters into seabed soils where large variations often occur in the shear strength of the soils although the failure mechanisms and bearing capacity of spudcan foundations have been studied in homogeneous soil and layered uniform soil the effect of the spatial variability in soil strength on the spudcan response is still unclear this study presents a random finite element method rfem for assessing the failure mechanisms and the bearing capacity of a spudcan foundation embedded in spatially varied seabed soils a comprehensive review of seabed soils discusses typical ranges of the mean the coefficient of variation and the scale of fluctuation of the undrained shear strength random fields are generated and mapped into a non linear finite element analysis to reveal the failure mechanisms of the spudcan in spatially varied soils the influence of the scale of fluctuation in different directions is investigated the results indicate that ignoring the spatial variability of soil strength leads to an overestimation of the bearing capacity it is unconservative for the foundation design to assume an isotropic random field model in the rfem analysis

geomechanical and geochemical changes during early stages of weathering of karamu basalt new zealand abstract variations in geochemical and geomechanical characteristics were measured through a basalt weathering sequence exposed at an abandoned quarry at karamu near hamilton new zealand geochemical measurements show that at the early stages of weathering fresh to slightly weathered reductions in the concentrations cao and mgo are rapid although they are not accompanied by major mineralogical change during later stages of weathering secondary clay minerals form following well described mineralogical changes fresh basalt is strong uniaxial compressive strength 262 mn m 2 point load index 5 59 with well developed closely spaced columnar jointing slightly weathered material is distinguished in the field only by slight discolouration along joint planes but laboratory tests show a dramatic loss of strength in slightly weathered rock point load index 0 41 cbr 43 a causal relationship between the loss of cations and loss of strength in the early stages of weathering is suggested this stage of weathering is diffusion controlled whereby cations are lost from the constituent primary minerals and replaced by h this process disrupts the lattice structure and causes a marked loss of strength implications are that slightly weathered rock which appears competent in the field is likely to have much lower strength and durability than assumed from field evidence

petrographic features influencing basic geotechnical parameters of carbonate soft rocks from apulia southern italy abstract a multidisciplinary petrographic and geotechnical approach aimed at understanding the conditioning by rock fabric on the mechanical properties of carbonate soft rocks is shown in this paper the analysed rocks extensively crop out in the apulia region and can be referred to three geological units pietra leccese late burdigalian early messinian calcarenite di gravina middle pliocene early pleistocene and salentino supersynthem midde late pleistocene 69 specimens of carbonate soft rocks belonging to all these units were selected from different sectors of apulia region and characterized according to petrographic physical and mechanical properties petrographic data allowed us to group all specimens in the following six classes i wackestone ii mud dominated packstone iii packstone iv grainstone v floatstone vi rudstone differently uniaxial compression strength ucs values classify the most part of specimens in very low and low strength revealing a dominant weak resistance and high deformability particular attention has been given to the relationships between petrographic features and physical and mechanical parameters of the apulian soft rocks by means of statistical tests based on the univariate analysis of variance one way anova and on the principal component analysis pca at first statistical analysis revealed that the rock geotechnical values are strictly dependent from the geological units particularly the samples of pietra leccese show significantly higher means of ucs young s modulus et and dry unit weight than samples of the calcarenite di gravina fm conversely samples of this latter unit have significantly higher means of porosity imbibition coefficient and permeability coefficient than those ones of the pietra leccese fm moreover statistical analysis was applied to estimate if geotechnical values differ according to the petrographic classes of the calcarenite di gravina fm and to verify the covariance between the geotechnical parameters of this unit the following results have been remarked i floatstone and rudstone have significantly higher means of ucs and dry unit weight and lower means of porosity than finer grained classes ii mud dominated packstone has significantly lower means of ucs dry unit weight et and permeability coefficient and higher means of porosity and imbibition coefficient than other petrographic classes iii grain dominated matrix free rudstone and grainstone have significantly higher values of permeability coefficient than mud dominated classes iv the occurrence of carbonate lithoclasts and of different dominant couples of sparry cement in pore spaces are two of the most important controlling factors of the rock strength and can also explains much of the intraformational variability observed in geotechnical data total porosity has not a clear correlation with permeability this means that the contribution of isolated pore spaces to the total porosity is relevant in apulian soft rocks as also suggested by the relatively low values of permeability compared to the relatively high percentages of total porosity a multidisciplinary characterization of carbonate soft rocks based on petrographic analysis and geotechnical determination of physical and mechanical properties is here recommended for future studies since this approach can give useful information to understand the peculiar behaviour of carbonate soft rocks and to drive the subsequent geotechnical investigations

centrifuge model study of spudcan penetration in sand overlying clay a series of centrifuge model tests has been conducted to investigate the bearing resistance of spudcan foundations of offshore jack up rigs in sand overlying normally consolidated clay the spudcan bearing resistance profiles measured in most of the tests recorded a peak resistance at a shallow depth within the upper sand layer followed by an abrupt post peak reduction in resistance causing the spudcan to plunge into the underlying soft clay this phenomenon is commonly termed as spudcan punch through hazard which potentially leads to severe structural damage of jack up rigs in the field the centrifuge test results revealed that the ratio of upper sand layer thickness over spudcan diameter and the ratio of bearing resistance between the upper sand and underlying clay affect the development of spudcan bearing resistance the limitations of existing design methods which were derived for the ultimate bearing capacity of pre embedded shallow foundation to assess the spudcan bearing resistance depth prof

a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase weathering summary the weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas these weathering profiles generally develop under both stable geodynamic conditions weathering rate erosion rate and a hydrolysing climate they are composed of thick stratiform layers that follow the paleo landscape paleotopography and thus present a gently dipping sequence at a regional scale the structure and the hydrodynamic properties of the weathering profile of a granitic area 53 km 2 maheshwaram catchment state of andhra pradesh india were characterized in detail and mapped from observations on outcrops 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones the structure of the weathering profile results from a multiphase process an ancient weathering profile was partly eroded down to its fissured layer it was later re weathered more or less parallel to the current topographic surface this peculiar structure is linked to the geodynamic history of the indian peninsula that underwent alternate weathering and erosion dominated phases the profile is thus composed from top to bottom up to a total depth of 35 m of sandy regolith saprolite 1 3 m 10 15 m of laminated saprolite containing unusual preserved fissures and a 15 20 m thick fissured layer by comparing various case studies in similar terrain a generalized 3 d geological and hydrogeological conceptual model of granite type aquifers granites gneisses etc is proposed in granite type rocks single weathering or multiphase weathering and erosion processes induce similar geological structures a few main geological differences arise from the comparison of single phase and multiphase weathering profiles i in the later the respective thicknesses of the various layers can be deeply modified ii the ancient fissured layer can be re weathered and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures and iii the upper part of the fissured layer is more densely fissured as a result of the same weathering processes the fissures from the fissured layer of single phase or multi phase profiles exhibit very similar hydraulic conductivities and show both a higher density of conductive fissures at the top of the layer the preserved ancient fissures within the laminated layer of a multiphase profile are partly obliterated by the recent weathering their hydraulic conductivity is thus significantly reduced nevertheless they do significantly contribute to borewell yield these weathering induced fissures provide most of the aquifer permeability the use of such a conceptual model for the precise geological mapping of the weathering structure appears to be a prerequisite for groundwater development and management in hard rock areas as it answers to several key issues

lithological effects in soil formation and soil slips on weathering limited slopes underlain by granitic bedrocks in japan abstract soil slips occur every few years due to heavy rains on biotite granite gb and hornblende biotite granite ghb slopes in the taga mountains ibaraki prefecture japan the occurrence density of soil slips per unit area is 2 7 times greater in the gb slopes than that in ghb slopes we examined the chemical mineral physical and mechanical properties of two soil profiles on soil slip scars in these slopes to study the effect of bedrock mineral composition on the density of soil slips for a given size of mineral grain the amount of biotite which is susceptible to chemical weathering in granitic bedrocks strongly influenced the density of soil slips in the gb slope the soil layer becomes thinner because of the smaller proportion of biotite in the bedrock this restricts the downward movement of soil water into the material below the slip plane during heavy rainfall the water surface then rises toward the slope surface above the slip plane this promotes soil slips increasing the density of soil slip scars in contrast in the ghb slope with more biotite in the bedrock the soil layer becomes thicker so that soil water moves easily into the material beneath the slip plane this limits the rise of water surface toward the slope surface above the slip plane even during heavy rainfalls there are consequently fewer soil slips and density of soil slip scars

extraction response of skirted foundations and a spudcan on sand over clay deposits this paper presents a comparison of extraction resistance between spudcan and skirted foundations in sand over clay deposits a series of centrifuge model tests was undertaken on a spudcan and two skirted foundations varying the length of the skirt relative to the foundation diameter the thickness of the sand layer was also varied to cover a range of practical interest it was found that the ultimate breakout forces of the spudcan and sealed skirted foundations in the sand over clay deposits are lower than that of a spudcan in a single layer clay deposit on the sand over clay deposits when the skirted foundations are sealed the breakout forces are 60 61 higher than that of the spudcan however when the skirted foundations are vented this difference becomes minimal regardless of the skirt length and the effective sand layer thickness beneath the foundation with the height of the sand plug left in the clay layer being similar to the thickness of the sand layer

observations of the effects of a clay layer on suction bucket installation in sand abstractsuction buckets are becoming established as a viable foundation solution for offshore wind turbines in sand suction induced seepage flow reduces effective stresses at the skirt tips whic

cirriped assemblage zones of the eocene claibornian and jacksonian stages southeastern atlantic and gulf coastal plains abstract two eocene cirriped assemblage zones are recognized in the gulf coastal plain of alabama and mississippi the arcoscalpellum subquadratum zone is characterized by a subquadratum meyer and aldrich aporolepas americana withers euscalpellum eocenense meyer and solidobalanus antiquus meyer and ranges through the upper claibornian stage the arcoscalpellum jacksonense zone is characterized by a jacksonense withers a choctawensis weisbord aporolepas howei cheetham and solidobalanus sp aff s antiquus meyer and ranges through the jacksonian stage representative species of one or both of these cirriped zones are found also in texas georgia south carolina and north carolina and afford an additional means for correlating claibornian and jacksonian marine units between the atlantic and gulf coastal plains the arcoscalpellum subquadratum zone is represented in the cook mountain formation of texas and mississippi the upper lisbon formation and overlying gosport sand of alabama the mcbean formation of georgia and the cubitostrea sellaeformis beds of the restricted santee limestone of south carolina the a jacksonense zone is represented in the moodys branch formation of mississippi and alabama the cocoa sand of alabama the pachuta marl of either mississippi or alabama the shubuta clay equivalents in alabama the clinchfield sand and dry branch formation of georgia the cross formation of south carolina and the biosparrudite and biomicrudite members of the castle hayne limestone in north carolina some cirriped species found in these zones in the southeastern atlantic coastal plain are not represented in the gulf coastal plain solidobalanus n sp 1 a species unrelated to the s antiquus group occurs in the mcbean formation of georgia arcoscalpellum subquadratum zone kathpalmeria georgiana ross is found in the griffins landing member of the dry branch formation of georgia and has tentatively been identified from the inglis formation of northern florida arcoscalpellum jacksonense zone euscalpellum carolinensis zullo and baum and solidobalanus n sp 2 related to solidobalanus n sp 1 are found in the cross formation of south carolina and the castle hayne limestone of north carolina arcoscalpellum jacksonense zone recognition of the a jacksonense zone in the cross formation and the castle hayne limestone supports recent conclusions based on calcareous nannofossil zonation and radiometric determinations that these units are jacksonian rather than claibornian in age

the use of cation packing index for characterizing the weathering degree of granitic rocks the weathering state and weatherability of rocks are highly important for engineering geology projects and the use of rocks as building stones the weathering state of rocks can be described by various chemical and petrographical weathering indices to determine weathering state of a rock considerable amount of chemical analyses is required weatherability of rocks depends on not only their mineral composition but also the number of cation replaceable with hydrogen in a mineral in this study the use of the k value cation packing index is defined as the number of cation in a mole for characterizing the degree of weathering of granitic rocks is investigated for the purpose of the study the kurtun granitic rocks are selected as the material of the study the study contains three main stages and these are field investigations laboratory studies and regression analyses during the field studies in situ weathering descriptions and sampling are carried out the samples are subjected to chemical and petrographic analyses and physical and mechanical tests at the final stage of the study a series of regression analyses between the cation packing index and other properties of the samples are performed the results show that the k value can be used as a weathering indicator when compared with the other chemical weathering indices the k value can be used as a weathering index without chemical analyses because it can be determined by mineralogical analyses

control of porosity on durability of limestone at the great sphinx egypt the study of the porosimetric data obtained from intrusion extrusion and reintrusion of mercury in limestone samples from the region of the sphinx reveals the characteristics of the pore system and allows analysis of durability factors

weathering of granites in a temperate climate nw portugal granitic saprolites and arenization abstract saprolites or in situ weathering products from granitoid rocks of northwest portugal were studied by means of x ray diffraction xrd of their clay fraction and observations of polished thin sections combined with transmission electron microscopy tem scanning electron microscopy with energy dispersive spectrometer sem eds microanalyses their principal features are 1 depths of more than 10 m 2 mean material loss of 40 as calculated by an isovolumetric method 3 low clay content mean value of 7 and a high degree of mineralogical evolution the clay fraction is characterized by a predominance of kaolinite and gibbsite with subordinate 2 1 minerals illite chlorite vermiculitic mixed layers vermiculite the significance of the secondary minerals in granitic saprolites from northwest portugal is compared to published data from atlantic europe this allows the definition of a climatic zonality for weathering products and identifies arenization as an important weathering process

improved prediction of spudcan penetration resistance by an observation optimized model abstractthe prediction models of penetration resistances of spudcan footings on sand overlying clay have been established by extensive centrifuge tests and large deformation numerical simulations

revealing the bearing capacity mechanisms of a penetrating spudcan through sand overlying clay the safe and economic use of mobile jack up structures is still hindered by limited understanding of the installation of their large conical spudcan footings in layered sand over clay sites this paper addresses this by detailing experimentally observed bearing failure modes induced during the penetration of a spudcan through a layer of sand into underlying normally consolidated clay digital images were captured continuously by installing a half spudcan against a transparent window and analysed using a particle image velocimetry technique coupled with close range photogrammetry correction as the experiments were performed in a geotechnical centrifuge the observed mechanisms occurred in stress conditions of similar magnitude to the offshore case the experimental evidence provides a failure modes at different spudcan penetration depths b the transitional failure mechanism at the event of peak bearing resistance and c the changes in overall failure mechanism due to varying geometric and streng

numerical modeling of the evolution of arcades and rock pillars abstract arcades i e lenticular and other specifically shaped hollows controlled by discontinuities have recently been recognized as a weathering form typical for sandstones weathered quartzites granites or tuffs they are produced by accelerated weathering and erosion in stress shadows related to the redistribution of gravity induced stress along planar discontinuities in the rock these forms occur worldwide in various settings inland humid arid and coastal the origin of arcades has been demonstrated via physical experiments and supported by a relatively simplistic numerical modeling however details on their shaping and the evolution of related forms have not been explained we performed an advanced numerical modeling to produce various shapes of arcades and rock pillars during the erosion of rock masses dissected by discontinuities we demonstrate that the erosion model in which erosion takes place when the maximum principal stress is below a certain critical value can adequately describe the formation of arcades in the modeling we set higher critical values for stresses at discontinuities than in a homogeneous material representing a rock mass to represent the higher tendency for disintegration of the discontinuity material which was weakened by the discontinuity formation processes by applying various discontinuity geometries and values of critical stresses we were able to reproduce the formation of various arcade shapes and complex three dimensional clusters of arcade cavities with rock pillars discontinuities and stress controlled erosion weathering are the only necessary conditions for arcade formation

erosion of a high altitude low relief area on the korean peninsula implications for its development processes and evolution the processes involved in the development of high altitude low relief areas hlas are still poorly understood although cosmogenic nuclides have provided insights into the evolution of hlas interpreted as paleo surfaces most studies focus on estimating how slowly they erode and thereby their relative stability to understand actual development processes of hlas we applied several techniques of cosmogenic nuclides in the daegwanryeong plateau a well known hla in the korean peninsula our denudation data from strath terraces riverine sediments soils and tors provide the following conclusions 1 bedrock incision rate in the plateau 127 m myr 1 is controlled by the incision rate of the western part of the korean peninsula and is similar to the catchment wide denudation rate of the plateau 93 m myr 1 2 the soil production function we observed shows weak depth dependency that may result from highly weathered bedrock coupled with frequent frost action driven by alpine climate 3 a discrepancy between the soil production and catchment wide denudation rates implies morphological disequilibrium in the plateau 4 the tors once regarded as fossil landforms of the tertiary do not reflect tertiary processes and 5 when compared with those of global paleo surfaces 20 m myr 1 our rapid denudation rates suggest that the plateau cannot have maintained its probable initial paleo landscape and thus is not a paleo surface our data contribute to understanding the surface processes of actively eroding upland landscapes as well as call into question conventional interpretations of supposed paleo surfaces around the world copyright 2015 john wiley sons ltd

deep weathering of granitic rocks a case of tunnelling in nw spain abstract this paper highlights a case of extensive development of saprolith from granitic bedrock in nw spain the weathering front at the study area extends to more than 250 m in depth the drilling of a railway tunnel madrid galicia high speed line through the bedrock and saprolith resulted in significant technical issues and economic losses cross sections revealing the 3d complexity of saprolith development are mainly based on fieldwork boreholes laboratory tests and the excavation works saprock is always observed overlying unweathered igneous bedrock two saprolite facies one clay rich and the other clay poor overlie the saprock the recognition is based on several criteria these deposits gradually thicken from the boundaries between the granitoid and metasedimentary roof pendants factors controlling saprolith development are discussed and the chemical and mineralogical changes and trends that occur are described variations in some geotechnical properties and the loss of quality of the rock masses from an engineering perspective are also quantified

assessing the punch through hazard of a spudcan on sand overlying clay a complete analytical method to describe the full load penetration resistance profile of a mobile jack up spudcan footing penetrating a sand over clay stratigraphy is described it is based on both large deformation finite element analyses and geotechnical centrifuge experiments the coupled eulerian lagrangian cel approach is used to accommodate the large deformations of a spudcan footing penetrating sand overlying clay modified mohr coulomb and tresca models describe the sand and clay behaviour with modifications accounting for the effects of strain softening on the response of the soil the cel results are shown to match centrifuge tests well allowing the numerical study to be extended parametrically and with confidence to cover the range of layer geometries sand relative densities and footing shapes that are of practical interest to offshore jack ups the results are used to a assess the performance of an existing model to predict the peak resistance in the sand layer extending its range of

impact of chemical weathering on micro macro mechanical properties of oolithic iron ore this article concerns the problem of collapses of abandoned underground room and pillar iron mines in lorraine north eastern france a study on the ageing of iron ore was carried out using different analytical techniques sem eds empa x ray diffraction mossbauer and icp spectroscopy as iron ore is a reactive environment in an oxidizing atmosphere created by anthropic activity this kind of weathering is triggered or activated by chemical processes and differs from diagenetic evolution under reducing conditions the weathering is characterized by the chemical alteration oxidation of reduced minerals siderite and berthierine in the inter oolithic cement mechanical disaggregation of oolithes recrystallization of berthierine and neo crystallization of a honeycombed hematite crust i e rust on all mineral surfaces this corrosion of iron ore was found to occur at a large scale in pillars especially in very old pillars which have been exposed to the mine atmosphere for 70 100 years the alteration of the inter oolithic cement which ensures material cohesion was not found to have been compensated by the crystallization of new minerals thus inducing the decrease in the micro macro mechanical properties of iron ore microindentation tests at millimetric scale micro compression triaxial tests at centimetric scale and macrocompression triaxial tests at decimetric scale this chemical weathering of anthropic origin plays a large scale and major role in the long term behavior of pillars and is probably one of the main causes of mine collapses that occured in lorraine therefore the decision to stop pumping of mine drainage thus inducing flooding of iron mines by groundwater was the correct decision since oxidation reactions in iron ore are necessarily less important under anaerobic condition than under aerobic condition in addition the knowledge of iron ore ageing allows for improved assessment of the long term stability of iron mines which have yet to collapse i e flooded iron mines and also iron mines which are still above the ground water table

environmental impact on construction limestone at humid regions with an emphasis on salt weathering al hambra islamic archaeological site granada city spain case study al hambra is an immense and valuable archaeological site in spain built on sabika hill with red brick and natural sandy limestone it exhibits weathering features indicating salt weathering process the main aim of this study is to examine weathering processes and intensity acting on al hambra rock petrography and mineralogical composition have been examined using thin sections scanning electron microscope x ray diffraction and x ray fluorescence limits of rock s physical parameters using ultrasonic waves and mercury porosimeter rock salt content through hydrochemical analysis salts attacking this structure are mainly from wet deposition of air pollutants on the long term chemical alteration of rock s carbonate content to its equivalent salts the salts concentration limit within the examined rock samples is considerably low but it is effective on the long run through hydration of sulphate salts and or crystallization of chloride salts rock texture type and its silica as well as clay content reduces its resistance to internal stresses by salts as well as wetting and drying cycles at such humid area the recession in limits of physical parameters examined for deep seated and weathered limestone samples quantitatively reflects weathering intensity on al hambra

suction stress characteristics in granite red soils and their relationship with the collapsing gully in south china abstract the main goal of this research is to study the relationship between the soil suction stress and soil properties within four different soil profiles of collapsing gullies in the hilly granitic region of southern china large differences were found in the four soil layers between granite red soils which are manifested in terms of soil bulk density porosity particle composition clay minerals micromorphology organic matter cation exchange capacity permeability oxide and hydraulics properties the suction stress of the upper soils increases rapidly and almost linearly monotonously with the increase of matric suction whereas c layers increases rapidly first followed by a slow increase the suction stress of the lower soils is significantly smaller than the upper soils under the same matric suction these findings illustrate that the collapsing gully starts from the lower part of the granite red soil and finally caused the gravity collapse in the upper soils which is the main aspect that is different from the other types of soil erosion furthermore suction stress has a very significant correlation with soil properties with a positive correlation to the fine particle content iron and aluminum oxide and a negative correlation to coarse particles in addition suction stress can also be explained as being directly proportional to weathering degree our research provides a theoretical basis for the mass failures of the granite derived red soil in southern china

bearing capacity on sand overlying clay soils a simplified conceptual model the derivation of a new conceptual model for predicting the peak penetration resistance of circular footings installed vertically into sand overlying soft clay is presented in this paper based on visualisation experiments and finite element analyses a failure mechanism of a frustum of sand being forced into the underlying clay with the outer angle reflecting the dilation in the sand is assumed the analytical basis of the new conceptual model follows the approach for silo analysis and takes into account the stress level and dilatant response of the sand a comprehensive analysis of the performance of the new model and other existing analytical methods in retrospectively predicting the peak resistance of a database of 49 geotechnical centrifuge tests is provided significant improvements over existing punching shear and load spread models are shown as a result of incorporating the strength properties of the sand in a consistent manner the new model has application to the offshore mobile jack up

undrained bearing capacity factors for conical footings on clay introduction the bearing capacity of circular foundations on undrained clay is of fundamental importance in many geotechnical problems in particular there are a number of designs of offshore foundations where the foundation can be treated approximately as a large circular footing for instance some gravity bases the spudcan foundations of jack up units and the more recently developed caisson foundations in most cases the footing is not placed at the ground surface and it is important to take into account the depth of embedment furthermore the base of a spudcan is generally not flat but approximates a shallow cone for foundations on soft clays the effect of the increase of strength of the soil with depth needs to be taken into account and this is particularly important for large foundations the purpose of this note is to present calculations of bearing capacity factors for shallow circular foundations accounting for embedment cone angle rate of increase of strength with depth and surface roughness of the foundation the results have widespread application particularly in the offshore industry the soil is assumed to be rigid plastic with yield determined by the tresca condition with an undrained strength su the method of characteristics is used for the bearing capacity calculation as described by shield 1955 eason shield 1960 houlsby 1982 and houlsby wroth 1982a for application to undrained axisymmetric problems some previous results have been published for this problem using similar numerical techniques e g houlsby wroth 1982b salencon matar 1982 houlsby wroth 1983 tani craig 1995 martin 2001 but the study presented here involves a much more comprehensive coverage of the parameters where comparisons can be made with the previous solutions the factors differ by up to about 0 5 which gives some indication of the level of accuracy attainable with this numerical technique exceptionally the rough footing results given by tani craig 1995 are higher by up to about 5 but this may be due to a problem with their numerical integration procedures see martin randolph 2001

geotechnical characterization of limestones employed for the reconstruction of a unesco world heritage baroque monument in southeastern sicily italy a detailed laboratory characterization of limestones employed for the reconstruction of saint nicholas cathedral a unesco world heritage monument in southeastern sicily is presented herein with the purpose of achieving a complete knowledge on the behavior of such rocks under stress whose engineering geological aspect had not been investigated before for scientific purposes specimens were sampled at three sites where this rock is quarried from two lithofacies of the same geological formation and are similar to other limestone varieties quarried worldwide and employed as construction material although slight differences between the samples occur at a macroscopic scale geotechnical tests highlighted relevant differences from the physical and mechanical points of view in order to look for one or more factors responsible of such dissimilarities a statistical analysis was carried out and interesting outcomes were achieved with the help of a microscopic analysis of the specimens moreover attention was paid on the modes of failure of tested specimens under compression whose attitude was described and correlated to selected properties of the rock results have both a practical implication because of the employment of this rock type as engineering material worldwide and a scientific relevance due to the peculiar behavior that such rock offered under stress

geologic features and durability of limestones at the sphinx geologic features considered to influence durability of the limestone at the sphinx are depositional history evolution of porosity and development of joints these strata have two orthogonal groups of vertical joints where these joints intersect wedge shaped blocks are separating causing loss of material from the core major reduction of the sphinx however is occurring due to salt crystallization aided by the ink bottle pore systems prevailing in these rocks

peak punch through capacity of spudcan in sand with interbedded clay numerical and analytical modelling the presence of a thin soft clay layer inside a bed of sand may significantly reduce the bearing capacity of the sand layer imposing a risk of punch through failure in this paper finite element fe simulations are reported using a hardening soil hs model for sand the fe model has been verified against centrifuge tests involving loose and dense sand layers overlying clay soil the effects of sand stiffness foundation roughness sand friction angle undrained clay strength clay strength nonhomogeneity and sand and clay layer geometries on the foundation peak capacities have been studied punch through failure is initiated with an inclined sand plug being sheared and pushed into the underlying soft clay during punch through the clay layer fails due to significant radial squeezing existing analytical models do not capture the combined failure mechanism of sand shearing and clay radial squeezing a new analytical model is developed to estimate the peak punch through capacity of a spudcan in sand w