Limestone Surface Research Articles

Technology to Freeze Time at Lassus and Viollet-le-Duc's Notre-Dame of Paris: Learning from the Past for the Cathedral of the Future

This article considers the use of plaster casting, an artistic technology, and silicatization, a scientific technology, in Jean-Baptiste Lassus and Eugène-Emmanuel Viollet-le-Duc’s nineteenth-century restoration of Notre-Dame of Paris. Plaster casting, practiced widely in academic artistic circles in the century prior to the restoration campaign, facilitated the work of the sculptors who toiled in the lodge just south of the cathedral’s southern face. The technology was employed in the early years of the restoration campaign and merited mention in an entry recorded by Lassus in the architects’ daybook of 1847. Entries in the 1853–59 daybooks from Viollet-le-Duc’s pen attest to the sustained use of silicatization, a process that involved coating the building’s limestone surfaces in a protective layer of water-soluble sodium silicate. Its practitioners touted it as a miraculous technology that would “stop the ravages of time on monuments.” Plaster casting was a tried-and-true artistic technology, exploited at Notre-Dame to a novel end, whereas silicatization was a cutting-edge application of water glass, the German chemist Johann von Fuchs’s early-nineteenth-century invention. This article places Lassus and Viollet-le-Duc’s restoration practice of the 1840s and 1850s at the crossroads between art and science, between nationalist competition and international collaboration, and considers what we might learn from their approach for the twenty-first-century restoration following the 2019 cathedral fire.

ГИДРОТЕРМАЛЬНОЕ МОДЕЛИРОВАНИЕ ФОРМИРОВАНИЯ ВТОРИЧНЫХ КОЛЛЕКТОРОВ В КРЕМНИСТЫХ ИЗВЕСТНЯКАХ (СИСТЕМА Н2О–СО2)

We have discussed the first results of hydrothermal modeling of the formation of secondary reservoirs (hydrothermal silicites) in siliceous limestones, which are widespread in the Pre-Jurassic complex of West Siberia, namely, in the H2O-CO2 system, in which the mole fraction of CO2 varied from 0.0 to 1.0, and the temperature from 215 to 410оС. It has been found that in this system there is a predominant dissolution of carbonates and, first of all, dolomite, as a result of which the surface of siliceous limestone is silicified and secondary porosity is formed in them. In some samples, quartz microcrystals with varying degrees of perfection of crystal faceting are shaped. It is found that pyrite is also unstable under these hydrothermal conditions and decomposes forming iron-containing carbonates at its sacrifice. Its transformation into pyrrhotite and copper and nickel sulfides is also observed. Biogenic quartz dissolved by a hydrothermal fluid is released from it either in the form of microcrystalline quartz, or in the form of quenching phases represented by cristobalite and/or amorphous silica. It is also found that at temperatures above 360°C, instead of iron-containing carbonates, chlorite is formed due to pyrite, while kaolinite also decomposes along with pyrite. It was experimentally established for the first time that at a high temperature (410°C), carbon dioxide acquires oxidizing properties and, as a result of its interaction with copper, oxide and red oxide of copper are formed. In addition, under these conditions, pyrite passes into iron-containing carbonates rather than chlorite. The main regularities of the formation of secondary reservoirs, i. e. hydrothermal silicites, in the Paleozoic siliceous limestone have been revealed.

Satellite imagery detection of land destruction in Klapanunggal Karst Landscape induced by limestone surface mining

Limestone mining activities in the Klapanunggal Karst Landscape were carried out at surface level. This method induced several adverse impacts on the environment. This study aimed to detect land destruction in the Klapanunggal Karst Landscape triggered by open limestone mining on the surface in the 2014-2020 period. The supervised classification method of Maximum Likelihood Estimation (MLE) was used to detect the change in land cover from Landsat 8 imagery, and Differential Interferometric Synthetic Aperture Radar (DInSAR) was applied to detect the change in landform from Sentinel 1A imagery. As a result, between 2014 to 2020, open limestone mining in the Klapanunggal Karst Landscape was confirmed to have a significant impact on the land cover changes in Klapanunggal, from an area with full of vegetation to a mining area with 4.0 x 106 m2 wide, and eroded landform with a dominant land deformation rate in the range of -47.75 to -39.50 cm/year and -39.50 to -31.25 cm/year. The limestone mining activity in the period of 2014 2020 was estimated to have mined limestone with a volume of 30.7 x 106 m3. Limestone surface mining has destructed Klapanunggal Karst Landscape, further research was needed to examine the adverse impacts on the hydrogeological system.

Assessment of the Current State of Qanibay al-Rammah Complex (908 AH/1502 AD), as a Procedure Precedes the Restoration Process

An assessment should be made of the current state of the historic buildings before starting in any intervention procedures. Where, any procedures of conservation of the building must be outrun by a perfect diagnosis according to the international conventions. Chemical, physical, mechanical properties and structural status are extremely important to give information about the current condition of Qanibay al-Rammah madrasa, which situated within Saladin square in Historic Cairo. This building has been affected by several deterioration factors since the construction and still suffering damage factors at the moment, which led to the occurrence of several damage aspects to the building, such as fissures in architectural elements, granular disintegration, loss of stone material, peeling of limestone surface, splitting in building material, the efflorescence of salts, pitting in limestone surface, black spots in stone surface, hard black crust, etc. The aim of this study is evaluation of the condition of Qanibay al-Rammah madrasa by two methods, firstly by different scientific techniques such as X-Ray Diffraction (XRD), EDX analytical methods, Scanning Electron Microscopy (SEM), Polarizing Light Microscopy (PLM), and Stereo Microscopy, and secondly by Numerical analysis based on 3D finite elements analysis to determine the critical places of the building. The followed methodology in this study allowed us to the assessment of the current status of the building by various scientific techniques to determine the real causes of damage, which must be taken into account during the intervention procedures.

Experimental study on secondary bearing mechanism of weakly cemented broken rock mass

In order to study the secondary bearing mechanism of weakly cemented broken surrounding rock, the surface of granite, limestone and mudstone broken rock samples were poured by cement slurry, and the weakly cemented rock mass was formed by static pressure infiltration method, and then an uniaxial loading test was carried out. The results show that the weakly cemented broken rock mass has a certain bearing capacity, but the bearing capacity is low, and the dispersion is high. The secondary bearing capacity of weakly cemented rock mass is affected by factors such as broken rock strength, rock particle size and rock gradation. The larger the rock particle size and strength are, the higher the secondary bearing capacity of the weakly cemented rock mass is. The average bearing capacity of the mudstone weak cementation specimen is 18.77 kN, and the residual bearing capacity is 1.46 kN, and a dispersion coefficient is 0.34. The average bearing capacity of granite is 343.65 kN, and the residual carrying capacity is 25.81 kN, and a dispersion coefficient is 0.11. The average bearing capacity of limestone is 367.22 kN, and the residual carrying capacity is 22.78 kN, and a dispersion coefficient is 0.3. After a certain grading, the average residual secondary bearing capacity of the weakly cemented rock mass is obviously improved, and the dispersion coefficient of peak bearing capacity is reduced. The grading scheme 1 has an average peak carrying capacity of 330.06 kN, a residual carrying capacity of 34.56 kN, and a dispersion coefficient is 0.07. The averaging scheme 2 has an average peak carrying capacity of 297.8 kN, a residual carrying capacity of 29.86 kN, and a dispersion coefficient is 0.14. The cementation regeneration mechanism of the broken rock mass mainly includes the cement-bonding effect of the cement slurry inside and on the broken rock mass. Under the loaded condition, the internal load-bearing network of the broken rock mass is the main mechanism for the secondary load of the broken rock mass, and the stability of the force-chain network is affected by the constraint. After the loss of the confinement, the force chain network fails, and the residual secondary bearing mechanism of the weakly cemented broken rock mass is transformed into the friction between the broken rock masses in the residual core rock pillar.

Effect of salinity, Mg2+ and SO42− on “smart water”-induced carbonate wettability alteration in a model oil system

HypothesisWe present a systematic study of the “smart water” induced wettability alteration. This process is believed to be greatly affected by the brine salinity and the presence of Mg2+ and SO42− in the brine. Experiments and modellingTo characterize the wettability alteration, we perform spontaneous imbibition measurement using Indiana limestone cores and a model oil with added naphthenic acid. Both single-electrolyte-based and seawater-based “smart water” are tested to investigate the effect of Mg2+, SO42− and salinity on wettability alteration. Rock/brine and oil/brine zeta potentials are measured, and the electrostatic component of disjoining pressure is calculated to understand the role of electrostatics in the wettability alteration. The surface concentration of charged species on the limestone surface is analyzed based on a natural carbonate surface complexation model (SCM). FindingsBoth the reduction of Na+ and addition of SO42− are found to contribute to wettability alteration. Mg2+ is found to be unfavorable for wettability alteration. Ca2+ is believed to facilitate SO42− with wettability alteration based on the comparison between the single-electrolyte-based and seawater-based brines. The reduction of the Na+ surface complexation (>CaOH⋯Na+0.25) in low salinity brines is believed to be a critical mechanism responsible for wettability alteration based on the SCM calculations.

Experimental research on deterioration of mechanical properties of carbonate rocks under acidified conditions

Understanding the relationship among the individual factors (i.e., carbonate rock types, acid rock reaction kinetics, deterioration of rock mechanical properties) can provide practical guidelines that can be used for the design and optimization of acid fracturing operation. A comprehensively experimental study was conducted to investigate the acid rock reaction kinetics of carbonate rocks under acidified conditions, and how the acid rock reaction would influence the carbonate rock mechanical properties. In addition, the deterioration mechanism of the carbonate rock mechanical properties is determined by the qualitative analysis of casting thin section images.Results show that the limestone rock is more susceptible to acid dissolution than limy dolomite rock under the same acidified conditions. The limestone rock has relatively large reaction rate constant and low activation energy, however, it is reverse in limy dolomite rock. As a result, the mechanical properties of rocks with relatively low cementation strength could be highly or lowly weakened. The reduction (in percentage, %) in mechanical properties of the limestone rocks with relatively high cementation strength is greater than that of the limy dolomite rocks with relatively high cementation strength.Casting thin section images show that the cementation and fillings of limestone and limy dolomite rocks are calcite and calcite-dolomite, respectively. The non-uniform (i.e., superficial and local deep) and uniform etched pattern (i.e., superficial and symmetrical) occur on the end surface of limestone and limy dolomite, respectively. Consequently, the mechanical properties of relatively high cemented limestone rocks are more significantly reduced than that of relatively high cemented limy dolomite rocks. This work is of great practical guidelines for the design and optimization of acid fracturing operations, as well as the efficient stimulation of carbonate reservoirs.

Electrokinetics at calcite-rich limestone surface: Understanding the role of ions in modified salinity waterflooding

Despite recent efforts to understand the wettability alteration process in limestone rocks during low salinity waterflooding, the findings related to wettability alteration due to changes in salinity and in the presence of a thin water film are still inconclusive. In this work, the effect of ions, temperature and solution pH on the rock and oil surface charges were explored by measuring zeta potential and predicting it using double layer surface complexation modelling (SCM).SCM fitted the trends of the measured zeta potential for both rock-brine and oil-brine interfaces by varying the surface equilibrium constants, particularly the equilibrium constant for the Ca2+ binding site. The SCM was used to predict 32 zeta potential values either measured experimentally or extracted from the literature.Zeta potential and isoelectric potential of rock-brine interface is dependent on brine salinity, sulfate concentrations and solution pH. The isoelectric point (IEP) for rock-brine interface decreased from pH of 8.5 for formation water to 7.8 for low salinity brine. Increasing the sulfate concentration in the seawater brine resulted in shifting the IEP to a lower pH value, indicating that sulfate ion shifts the zeta potential of rock-brine interface to negative over a wide pH range, due to the increased site density of >CaSO4− and the simultaneous reduction in the site densities of both CaOH2+ and CO3− as sulfate concentration increases.Bond product sum (BPS), together with total disjoining pressure calculations were used to predict wettability trends, supported by contact angle measurement, where the total BPS was observed to be the lowest and repulsive disjoining pressure generated at the COBR for LSW brines. This was observed to be significantly influenced by [COOCa+][CO3−] and [COOMg+][CO3−] bond linkages at low pH (below 8) whiles the bond linkages of [COOCa+][CaCO3−] and [COOMg+][CaCO3−] dominated the COBR interface at higher pH (above 8).

Fungal deterioration of limestone false-door monument

Unfortunately, monuments all over the world may become discolored and degraded as a result of the growth and activity of fungi. Biodeterioration is an irreversible damage that is caused by microbial colonization on the surface of buildings. Different fungi were isolated from limestone False-door in Kom Aushim museum- El-Fayoum governorate, Egypt. These include; Aspergillus niger, A. fumigatus, A. sulphureus, A. flavus, Alternaria alternata, Alternaria spp., and Cladosporium herbarium. Fungal grow on modern limestone surfaces after 60 days of infection. Transmission electron microscope demonstrated the penetration and presence of fungal threads inside limestone. Environmental Scanning electron microscope attached with EDX Unit revealed an increase in carbon and magnesium ions from 9.16 to 12.17% and 1.41–1.51%, respectively after fungal infection of limestone, while other ions decreased after infection; aluminum from 1.96 to 1.39%, silicon from 7.40 to 3.57%, potassium from 0.44 to 0.41%, calcium from 41.41 to 35.04 % and iron from 1.08 to 0.90 %. p-Chloro-m-crysol is the most potent to inhibit the growth of isolated fungi at MIC 50 ppm for most fungal species.

Geological and geomorphological structure and geoecological conditions of Noginsky-Klyazminsky district of Moscow region

In connection with the construction of industrial centers on the territory of the Noginsko-Klyazminsky district, we conducted out material-structural, structural-geomorphological (neotectonic) and geodynamic studies. Studies have revealed a weak protection of this territory from irrational use. The buried limestone surface is characterized by excessive fissuring and powerful weathering, and limestone is cavernous, which indicates the development of leaching processes.Thin and predominantly sandy composition of Quaternary deposits, overlying bedrock, is permeable to atmospheric and surface sediments, including technologically polluted runoff. Closed depressions, funnels, subsidence, flooding, etc. were found in the relief.Changes in the terrain under construction adversely affect the geological environment, since this leads to a point-like pollution of groundwater near to the surface, and the barrage effect - to disruption of the groundwater flow.These features of the geological structure are unfavorable for placement on the territory of Noginsk and, in the valley of the river Vassa industrial centers.

Hurricanes, Storm Surge, and Pine Forest Decline on a Low Limestone Island

Hurricanes are a frequent disturbance in the western Atlantic impacting coastal forest structure and persistence. This study addressed the hypothesis that periodic hurricane-associated winds and storm surges can interact with sea-level rise to cause the demise of coastal pine forests, based on the response of the Florida Keys’ last extensive tract of slash pine (Pinus elliottii var. densa) following Hurricane Irma (September 2017). Irma’s winds reached Category 4 strength in the study area on Big Pine Key, and storm surge flooded the island’s low limestone surface with salt water for the third time in 20 years, including Hurricanes Georges in 1998 and Wilma in 2005. Total mortality was 32% and was concentrated in the largest trees. Broken and uprooted trees that died immediately were distributed randomly across the elevation gradient, but trees without major stem damage that succumbed later occupied lower elevations. The extensive salt water flooding at low elevations was likely an agent of the mortality of slash pine, a fresh water–dependent species. Mortality due to Hurricane Irma contributed to a 1998–2018 decline in pine tree density and biomass of 74% and 80%, respectively. These dynamics were characterized by pine recruitment that was minimal in comparison with the three hurricane-driven mortality episodes. The data suggest that the 6 cm sea-level rise over the period exacerbated storm surge mortality by ponding salt water over more of the land surface, and the resulting scarcity of mature trees contributed to recruitment failure. In effect, the population declined at each disturbance, sea-level rise magnified these losses, and the local resilience of the population, i.e., its capacity to recover, was exceeded.

The effect of the reciprocal relations of the deterioration symptoms in different building materials in some of historic Cairo's buildings

In the present study, since historic Cairo established, limestone and woods have been used for building construction alongside. The building materials representingcase studies in historic Cairo are affected by different deterioration factors, such as rising ground water level, the salt weathering, air pollution, frequency between temperatureandrelative humidity, and microbiological deterioration.From case studies survey various types of weathering forms were observed, such as granular disintegration, splitting in the wooden lintel, the efflorescence of salt, pitting in limestone surface, black spots in limestone surface due to microbiological deterioration, black crust and peeling, flaking of painting layers, etc. The aim of this study is to identify on the reciprocal relations ofthe deterioration symptoms in different building materials (limestonewood) used in some of historic Cairo's buildings. The samples were collected from different sites, investigated by several scientific techniques such as X-Ray Diffraction (XRD), EDX analytical methods, Fourier Transform Infrared Microscopy (FTIR) to detect the changes of the main wood components (cellulose,, lignin), Scanning Electron Microscopy (SEM), Polarizing Light Microscopy (PLM), Stereo Microscopy, and microbiological investigation were also done. The results of the study indicated that there was a fungal infection on the surface of limestone, in particular which is found close to the wooden elements, microbiological investigation was shownthe following fungi:,,,,,. From investigation of wood samples are shown that there is a rise moisture content in the wood materials, due to direct connection between them and adjacent the stones, in addition to crystallized salts found in wood fiber and internal structure of limestone, such as NaCl, CaSO4.2H2O, CaSO4; due to the effect ofbuilding material properties on each other. Furthermore, the physical and mechanical properties tests of building materials indicated that reduction in its properties.

Micro-weathering of limestone surfaces in a foreland of Hallstätter Glacier (Dachstein, Austria)

ABSTRACTSince the end of LIA climatic amelioration results in retreat of glaciers worldwide and the development of glacial forelands with freshly abraded rock surfaces undergoing weathering. When the timing of glacier retreat is known, glacier forelands are highly valuable study sites to investigate initial and short-term weathering processes. The aim of this study is to quantify limestone surface decay in the foreland of Hallstätter Glacier in Dachtein massif, Austria, based on the measurement of surface micro-roughness and weathering rind characteristics. By establishing a post-LIA chronosequence we seek to gain insight into initial stages of weathering in a cold alpine environment. Micro-roughness was measured with a use of Handysurf E-35B electronic profilometer, and weathering rind characteristics were determined based on SEM equipped with a microprobe. The micro-roughness increases from locations close to the glacier front towards the LIA moraine. The greatest measured increase occurs within the first 50 years since deglaciation. Weathering rinds are manifested as zones of micro-cracks and micro-pits, and accumulation of mineral grains at the rock surface and along the micro-voids. Increasing rounding of the grains and their development along micro-fissures is attributed to limestone dissolution, which is probably responsible for the development of micro-pits, best observed after c. 100 years since deglaciation. No protecting shield in a form of a weathering coating was observed. Instead, the weathering rind thinning is attributed to the weathering rind erosion. Results obtained provide further insight into initial stages of limestone weathering in a cold alpine environment.

Pengujian Geser Limestone Untuk Menghitung Angka Keamanan Terhadap Kelongsoran Di Utama Mandala Pura Uluwatu

The shear strength value is one of the important points in calculation of slope stability. One way to obtain the shear strength value is to do a direct shear test in laboratory. Like the cliff reinforcement study at Utama Mandala Uluwatu temple which is currently experiencing crack, it is necessary to test the shear strength of the limestone material at the cliff of the temple . There is no limestone testing equipment in the laboratory of the Civil Engineering Department, so that innovation is needed on the existing sliding test equipment. In this study innovation was carried out on how to test the soil shear strength so that it could be used to test the limestone shear strength. The test is done by moving two limestone surface that have been formed based on the mold tool which shape is circle. The shear strength slope at Uluwatu temple, which is currently experiencing crack in dry condition is . The shear strength value is used for calculating slope stability at Uluwatu Temple which is currently experiencing crack wich . The calculation used is curved slope stability by only calculate the life load and dead load. From the calculation of the stability of the slope, the safety factor is 1.15.

Investigation on the relationship between the environment and istria stone surfaces in Venice

Architectural limestone surfaces are particularly susceptible to decay from natural and anthropogenic acidifying gases and particulates. This investigation evaluates environmental conditions, air quality, and decay patters on Istria stone surfaces of four palaces in Venice (Italy): Ca’ Bembo, Ca’ Bottacin, Ca’ Foscari, Ca’ Dolfin. Climate parameters and air quality indicators are used to discuss the atmospheric influence on limestone and to calculate the related theoretical recession rate. Graphic assessment, surface profiling, digital microscopy, infrared spectroscopy, and x-ray fluorescence are used to assess stone surface textures and degradation patterns associated with stone decay. The morphological analysis via surface profiling using silicon mould, digitization and statistical analysis of the roughness is proposed for the assessment of stone deterioration. In particular, the methodology is used for understanding stone morphological variations in relation to parameters such as sites, exposure (sheltered or exposed area), and location (overlooking a Canal or inner court).In relation to increasing rain amount and intensity, decreasing SO2 and increasing NOx concentrations, theoretical limestone recession rate compatible with an urban environment (around 8 μm/year) are calculated. The morphological analysis of the sites evidences the role of the stone original texture and finish, the façade location and the specific exposure on the formation of crusts or eroded area. Buildings not recently restored (Ca’ Bottacin and Ca’ Bembo) present thick dendritic crusts, in particular on court side and in sheltered positions. Ca’ Foscari surfaces, subjected to cleaning intervention after 2000s, show thin grey crust only in sheltered areas, reflecting the reduced presence of SO2. Large eroded areas have been found on exposed surfaces in relation to the rain wash-out action and to high levels of NOx.

Long term stability of biodegradable polymers on building limestone

Synthetic polymers can be replaced by biodegradable ones as adhesives, water repellents and consolidants on the stone surfaces and facades of the historic buildings in their conservation to minimize future deterioration. In this study, the long-term stability of two biodegradable polymers, polyhydroxybutyrate (PHB) and poly-l-lactide (PLA), and an acrylic polymer (Paraloid B72) which is commonly used in conservation works of artefacts, were evaluated on limestone using a UV lamp-weathering chamber (up to 104 days) for future protection studies. Chemical and morphological changes induced by an accelerated weathering test were examined by Fourier Transform Infrared spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) analyses. Protection efficiency of the polymers was determined by the changes in color, capillary water absorption, static contact angle on limestone. Paraloid B72, PHB, and PLA coatings significantly increased hydrophobicity while decreasing capillarity water absorption and caused negligible change in the color of the limestone. Protection efficiencies of PLA and PHB polymers were almost the same as that of Paraloid B72, a widely used acrylic polymer. However, PLA and PHB seemed to be favorable polymers as protective agents due to their reversibility and biodegradability, low chromatic changes, good hydrophobic behavior and good stability to weathering in reducing the effects of outdoor exposure on limestone surfaces.

Evaluation of the applicability of nano-biocide treatments on limestones used in cultural heritage

Abstract One of the main problems in the conservation of historical buildings and archaeological sites is the one caused by biodeterioration. Biopatina, biocrust or biofouling generate aesthetical changes and induce degradation processes within the stone matrix. In this work, three treatments based on silver nanoparticles and silver/titanium dioxide nanocomposites have been studied as potential biocides for limestones: citrate-stabilized silver nanoparticles, silver/TiO2 nanocomposites and citrate-stabilized silver/TiO2 nanocomposites. These treatments were synthesized following a bottom-up method, using or not a stabilizing agent (citrate), and have been characterized by UV-Visible spectrophotometry, Dynamic Light Scattering and Raman spectroscopy. These treatments were applied on limestones from three different Spanish quarries located in Utrera (Seville), El Puerto de Santa Maria (Cadiz) and Novelda (Alicante). The aesthetical modification of limestone surfaces was studied by colorimetric techniques and the effectiveness of protection against biofouling formation was tested using an accelerated biofouling growth assay. The best results were obtained for the treatments based on citrate-stabilized silver nanoparticles. The effectiveness of the treatments depends on their penetration depth in the stone matrix and in this study, we have used Laser Induced Breakdown Spectroscopy to determine the depth profiles of nanocomposite presence in the stone matrix. Our results demonstrate that nanocomposites based on citrate-stabilized silver nanoparticles can be useful for the treatment of historical buildings and archaeological sites made of limestone, without producing high colour increments. Additionally, we have demonstrated the suitability of Laser Induced Breakdown Spectroscopy for the detection of silver/TiO2 nanocomposites and for the generation of depth profiles.

River incision and migration deduced from 36Cl cosmic-ray exposure durations: The Clue de la Cerise gorge in southern French Alps

We estimate recent (20 ka) incision and lateral migration rate on a spectacular ~N-S striking gorge cross-cutting N-dipping limestones in a fold-and-thrust belt of the external Southern French Alps. Upstream of the gorge, the river makes a right angle turn and follows the limestone surface parallel to the bedding direction (~EW). Eighteen samples were gathered along two vertical river polished profiles and three others on the denuded north-dipping surface layer, in order to determine river incision and lateral migration timing and rates. Surface age exposures of polished river cliff and bedding surface have been obtained from 36Cl cosmogenic nuclide dating and allow us to constrain the rate of vertical incision and of surface denudation of the Jurassic limestone layer. Fifteen 36Cl exposure ages have been obtained and range from ~21 ka to ~3 ka. Samples clearly define two age/height linear trends, which slopes correspond to incision rates of 1 and 0.3 mm/yr, respectively. The transition from low to high incision rate occurs at about ~12 ka, i.e. during the Younger Dryas glacial phase. Data also indicate that the vertical incision of the N-S branch of the gorge is coeval with the lateral (northward) river migration of its E-W branch associated with the denudation of the limestones surface. Extrapolating incision rates deduced from 36Cl exposure ages through time suggests that the incision of the Clue and denudation of the Jurassic limestones started about 500–600 ka ago.

Rate Effects on Shear Deformation of Rough Limestone Discontinuities

The relationship between slip velocity, resistance to shear, and geometrical evolution of initially rough limestone surfaces is investigated in servo-controlled direct shear experiments. We focus on shear stress evolution throughout the deformation process, as function of the shear rates applied. Direct shear tests are performed on tensional fractures positioned in a perfectly mating configuration, using a hydraulic, closed-loop, servo-controlled system. The discontinuities are sheared to prescribed displacement target of 10 mm under a constant normal stress of 5 MPa while shear stress and dilation are recorded under controlled shear rates between 0.1 and 50 µ/s. Surface geometry is measured using laser profilometer before and after tests, and roughness evolution is statistically quantified. We find that, before peak shear stress is attained, the shear stiffness increases with slip velocity, manifesting asperity strain hardening during this largely elastic deformation stage. Peak shear stress and stress drop, however, are both inversely proportional to velocity, indicating velocity weakening coupled with rate-dependent healing of the interfaces. The final roughness of the sheared surfaces increases moderately with increasing slip velocity indicating enhanced fragmentation and brittle deformation with increasing shear rate.

Influence of electrical surface charges on thermodynamics of wettability during low salinity water flooding on limestone reservoirs

Wettability is an important factor in controlling the displacement efficiency and ultimate oil recovery in oil-wet naturally fractured reservoirs. The scope of this study extends from the experimental investigation to analytical approach based on the DLVO theory to thin film stability evaluation. The zeta potentials on limestone rock/brine and oil/brine interfaces, and also, the electrical double layer, the London–van der Waals, and the structural forces are measured to model the disjoining pressure isotherms with the brine solutions containing monovalent and divalent ions. Then, the stability of the wetting film on the limestone surface is compared with IFT measurements, contact angle and core flooding experiments. Based on results, strong negative charges at rock/brine and oil/brine interfaces were occurred during sea water injection and increase the repulsive forces at the rock/oil interface to release the oil film from the limestone surface. Also, the oil recovery in case of Na+ in the presence of SO42− is 50% higher than it for both cases of Na+/K+ and Cl−. From the disjoining pressure isotherms, a more stable water film observes from the low salinity brine containing the Mg2+ in the presence of Cl− compared to Mg2+ in the presence of SO42−.