Uniaxial compressive strength (UCS) is the most used parameter to measure rock strength. However, restrictions in sampling large volume of material, the need of very large set of results and onsite ...characterisation of UCS non-destructively are requirements in many scientific and engineering investigations. The estimation of UCS from a single non-destructive or minimally invasive technique (NDT) may result incomplete because each NDT is sensitive to different compositional and textural factors.
This paper combines open porosity, P-wave velocity, Leeb hardness and micro-drilling resistance force to estimate USC for a wide range of carbonate sedimentary rock types with different petrographic characteristics. Results reveal that mineralogical composition significatively affects micro-drilling resistance force profiles and P-wave velocity values, especially for quartz-bearing rocks. In addition, texture controls substantially the reproducibility of tests sensible to rock surface properties, such as Leeb hardness and micro-drilling resistance force.
Fifteen simple and multiple expressions for UCS are fitted. Linear expressions have shown better coefficients of determination (R2) than non-linear equations because of the linearity shown by individual parameters. Curve fitting improves as the number of petrophysical parameters increase in the multiple linear regression analysis. The best correlation is found when the equation incorporates all the mechanical parameters obtained non-destructively as well as open porosity (R2 = 0.910). Leeb hardness is always the most significant variable of the fitted regressions and its addition into multiple linear equations causes an increase of R2. Open porosity also improves R2 whereas drilling force and P-wave velocity have a lower statistical weight in the expressions. The UCS estimation from all NDT, without considering open porosity, shows a good correlation (R2 = 0.899), which presents the advantage that they can be obtained non-destructively with portable equipment and can provide a numerous set of results at relatively low cost.
•Compositional and textural factors affect differently to the mechanical parameters.•Leeb hardness is the most significant variable in the fitted regressions.•The best UCS estimation incorporates all NDT parameters as well as open porosity.•Portability is one of the main advantages of NDTs.
•The irreversible cracking stress was not reached for rock preheated to 200 °C and major damage was caused from cycle 10.•At 400 °C, the greatest damage was observed during the first five cycles.•The ...quenching behaviour of four granites was different depending on the initial weathering conditions.•The increase in connectivity was improved for sound granites while more weathered granites experienced increased microcracking with less connectivity.•The water-granite rock interaction showed the dissolution of K-feldspar, plagioclase, and the degradation of clays, leading to enrichment mainly in K, Na, and Ca.
In this study, the physicochemical properties of granitic rocks subjected to quenching cycles were studied experimentally. Four granites of similar mineralogy but with different degrees of initial weathering (porosity between 1 and 6%) were slowly preheated at two peak temperatures (200 and 400 °C) and then quenched 35 times.
To study the effect of thermal cycling on the physical properties, non-destructive tests were used such as water porosity, capillary water absorption tests, P- and S- wave propagation velocities, nuclear magnetic resonance relaxometry, and X-ray micro-tomography. Chemical analysis of the granites was performed using X-ray fluorescence, which provided information on the major and trace elements. Water-granite interactions were followed using inductive plasma mass spectrometry (ICP-MS).
The variation of all the measured parameters indicates the creation of cracks with thermal fatigue. The porosity, water uptake, size, and volume of cracks increased while P- and S- wave velocity and Young's modulus decreased. At 200 °C, the changes were progressive up to ten cycles, from which the stress threshold was reached and only small readjustments took place. At 400 °C, the greatest damage was observed during the first five cycles. These changes were a direct consequence of the propagation of the microcracks induced by the strong gradient during the quenching tests. For both temperatures, the changes depended on the initial weathering conditions of the granites. Initially, weathered granites showed crack development or crack closure during quenching, meanwhile the damage on the sound rocks was characterized by the creation of intragranular microcracks.
The analysis of the experimental fluids showed enrichment in K, Na and Ca in the solution as consequence of the dissolution of K-feldspar, plagioclase and the degradation of mica and clays, independently of the physical and mechanical modifications.
This investigation studies the physical and chemical effect of salt weathering on biocalcarenites and biocalcrudites in the Basilica of Our Lady of Succour (Aspe, Spain). Weathering patterns are the ...result of salty rising capillary water and water lixiviated from pigeon droppings. Surface modifications and features induced by material loss are observable in the monument. Formation of gypsum, hexahydrite, halite, aphthitalite and arcanite is associated with rising capillary water, and niter, hydroxyapatite, brushite, struvite, weddellite, oxammite and halite with pigeon droppings. Humberstonite is related to the interaction of both types of waters. Analysis of crystal shapes reveals different saturation degree conditions. Single salts show non-equilibrium shapes, implying higher crystallisation pressures. Single salts have undergone dissolution and/or dehydration processes enhancing the deterioration process, particularly in the presence of magnesium sulphate. Double salts (humberstonite) have crystals corresponding to near-equilibrium form, implying lower crystallisation pressures. This geochemical study suggests salts precipitate via incongruent reactions rather than congruent precipitation, where hexahydrite is the precursor and limiting reactant of humberstonite. Chemical dissolution of limestone is driven mainly by the presence of acidic water lixiviated from pigeon droppings and is a critical weathering process affecting the most valuable architectural elements present in the façades.
Fire is a major decay agent of rocks and can generate immediate catastrophic effects as well as directional and anisotropic damage that affect long-term weathering processes. Temperature increase is ...the most relevant factor, among other components in a fire, generating mineral transformations and bulk mechanical damage. Mineralogical changes at high temperatures are key to understanding the overall mechanical behaviour. However, most studies to date were carried out after rock specimens were heated to a target temperature and cooled down to room temperature. Therefore, these studies are missing the observation of the actual mineral processes during heating. This paper aims to compare mineralogical changes in crystalline rocks during heating by means of XPS and different XRD techniques. Samples of four different granitoids were heated to several temperatures up to 1000 °C to evaluate their chemical and structural changes. Results show how standardised thermal expansion coefficients are not a suitable indicator of the bulk effect of high temperatures on rocks. Results also show how thermal expansion estimations from XRD lattice measurements may be an alternative to bulk dilatometric tests, as they can be performed with limited sampling, which may be necessary in some studies. Nevertheless, XRD and XPS results need to be interpreted carefully in relation to the bulk effects of temperature increase in the rocks, as the structural behaviour may seemingly contradict the macroscopic effect.
Abstract
A data-driven approach insensitive to the initial conditions was developed to extract governing equations for the concentration of CO
2
in the Altamira cave (Spain) and its two main drivers: ...the outside temperature and the soil moisture. This model was then reformulated in order to use satellite observations and meteorological predictions, as a forcing. The concentration of CO
2
inside the cave was then investigated from 1950 to 2100 under various scenarios. It is found that extreme levels of CO
2
were reached during the period 1950–1972 due to the massive affluence of visitors. It is demonstrated that it is possible to monitor the CO
2
in the cave in real time using satellite information as an external forcing. For the future, it is shown that the maximum values of CO
2
will exceed the levels reached during the 1980s and the 1990s when the CO
2
introduced by the touristic visits, although intentionally reduced, still enhanced considerably the micro corrosion of walls and pigments.
Doctrinal texts on architectural heritage conservation emphasize the importance of fully understanding the structural and material characteristics and utilizing information systems. Photogrammetry ...allows for the generation of detailed, geo-referenced Digital Elevation Models of architectural elements at a low cost, while GIS software enables the addition of layers of material characteristic data to these models, creating different property maps that can be combined through map algebra. This paper presents the results of the mechanical characterization of materials and salt-related decay forms of the polygonal apse of the 13th-century monastery of Santa María de Bonaval (Guadalajara, Spain), which is primarily affected by salt crystallization. Rock strength is estimated using on-site nondestructive testing (ultrasound pulse velocity and Leeb hardness). They are mapped and combined through map algebra to derive a single mechanical soundness index (MSI) to determine whether the decay of the walls could be dependent on the orientation. The presented results show that salt decay in the building is anisotropic, with the south-facing side of the apse displaying an overall lower MSI than the others. The relative overheating of the south-facing side of the apse enhances the effect of salt crystallization, thereby promoting phase transitions between epsomite and hexahydrite.
The individual contribution of natural disturbances, localized stressors, and environmental regimes upon longer-term reef dynamics remains poorly resolved for many locales despite its significance ...for management. This study examined coral reefs in the Commonwealth of the Northern Mariana Islands across a 12-year period that included elevated Crown-of-Thorns Starfish densities (COTS) and tropical storms that were drivers of spatially-inconsistent disturbance and recovery patterns. At the island scale, disturbance impacts were highest on Saipan with reduced fish sizes, grazing urchins, and water quality, despite having a more favorable geological foundation for coral growth compared with Rota. However, individual drivers of reef dynamics were better quantified through site-level investigations that built upon island generalizations. While COTS densities were the strongest predictors of coral decline as expected, interactive terms that included wave exposure and size of the overall fish assemblages improved models (R2 and AIC values). Both wave exposure and fish size diminished disturbance impacts and had negative associations with COTS. However, contrasting findings emerged when examining net ecological change across the 12-year period. Wave exposure had a ubiquitous, positive influence upon the net change in favorable benthic substrates (i.e. corals and other heavily calcifying substrates, R2 = 0.17 for all reeftypes grouped), yet including interactive terms for herbivore size and grazing urchin densities, as well as stratifying by major reeftypes, substantially improved models (R2 = 0.21 to 0.89, lower AIC scores). Net changes in coral assemblages (i.e., coral ordination scores) were more sensitive to herbivore size or the water quality proxy acting independently (R2 = 0.28 to 0.44). We conclude that COTS densities were the strongest drivers of coral decline, however, net ecological change was most influenced by localized stressors, especially herbivore sizes and grazing urchin densities. Interestingly, fish size, rather than biomass, was consistently a better predictor, supporting allometric, size-and-function relationships of fish assemblages. Management implications are discussed.
This work presents five different methods for quantifying the segregation phenomenon in lightweight aggregate concretes (LWAC). The use of LWACs allows greater design flexibility and substantial cost ...savings, and has a positive impact on the energy consumption of a building. However, these materials are susceptible to aggregate segregation, which causes an irregular distribution of the lightweight aggregates in the mixture and may affect the concrete properties. To quantify this critical process, a new method based on image analysis is proposed and its results are compared to the well-established methods of density and ultrasonic pulse velocity measurement. The results show that the ultrasonic test method presents a lower accuracy than the other studied methods, although it is a nondestructive test, easy to perform, and does not need material characterization. The new methodology via image analysis has a strong correlation with the other methods, it considers information from the complete section of the samples, and it does not need the horizontal cut of the specimens or material characterization.
Despite evidence of damaging human impacts, cave paintings may again be threatened if visitors are allowed access.
In the last decade, considerable attention has been paid to the deterioration of the ...caves that house the world's most prominent Paleolithic rock art. This is exemplified by the caves of Lascaux (Dordogne, France) (
1
) and Altamira (Cantabria, Spain), both declared World Heritage Sites. The Altamira Cave has been closed to visitors since 2002. Since 2010, reopening the Altamira Cave has been under consideration. We argue that research indicates the need to preserve the cave by keeping it closed in the near future.
Radon in soil poses a significant health risk when it accumulates inside dwellings. The estimation of radon potential is a difficult task due to the complex dynamics of radon within soil and its ...relations with the weather. This research focuses on the variability of radon activity, driven by environmental changes, assessed in two loam soils (loamy sand–granite soil and silty clay loam-calcareous soil) with different radium contents. We conducted an experiment with teow soil columns in a semi-controlled outdoor laboratory, in a warm semi-arid climate. We also examined the consequences of abundant rainfall on radon activity through artificial soil water content (SWC) experiment conditions. Statistical analyses reveal that SWC is the most significant parameter influencing radon activity in these experiments. Radon is proportional to SWC and inversely proportional to temperature, evapotranspiration, and pressure in both soils, while wind is negatively related only in the loamy sand soil. Based on our findings, we modelled radon potential considering different soils and climatic contexts. SWC influences radon potential by changing radon emanation, activity, and permeability, depending on the local soil texture and radium concentration.
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