Calcarenite Rock Research Articles

Evaluation of Calcarenite Degradation by X-ray Photoelectron Spectroscopy Analysis inside the Rupestrian Church of San Pietro Barisano (Matera, Southern Italy)

We report on the XPS analysis of degraded surfaces inside San Pietro Barisano, the rupestrian church carved into the calcarenite rock of ancient Matera, which has been a UNESCO World Heritage Site since 1993. As reported in previous works, the “Sassi” district and the park of rupestrian churches were available as open laboratories for the National Smart Cities SCN_00520 research project dedicated to the sustainable recovery of this remarkable architectural heritage. In that context, XPS functionality was shown to reside in the possibility of analyzing surfaces by feasible sampling, acquiring spectra without any preliminary sample treatment, and processing data using a well-established curve fitting procedure. The obtained results allowed us to identify the degradation products of the investigated surfaces, thus contributing to defining a diagnostic framework for subsequent actions. Accordingly, the samples here considered, collected from the internal wall surfaces of the church, were all analyzed in comparison with the reference calcarenite, and the XPS results were evaluated as a function of local environmental factors and the historical context of the church itself. The final aim was to provide, for each sample, the most representative indicator(s) of biotic and/or abiotic degradation for reliable use, in a multidisciplinary context, in planning care interventions for building heritage.

Morphological and mineralogical characterization of surficial weathering on calcarenite rocks in the rupestrian system of “San Michele delle Grotte” at Gravina in Puglia (Bari, Apulia)

San Michele delle Grotte is a rupestrian cave excavated into the “Calcarenite di Gravina” formation, resting over the Cretaceous formation of “Calcare di Altamura”. Both rock types show evident instability features and intense surficial rock weathering. A detailed mineralogical and morphologic characterization of Calcarenite di Gravina Fm. samples has been carried out by means of optical and petrographic microscope (OM and PM), scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). In thin section, bioclastic packstone to grainstone fabrics were observed. In the surficial portion of the rock it is possible to find biological colonizations and efflorescences: the first are dominated by algae covering the calcite substrate, whilst the efflorescences contain mainly sulfates such as syngenite, gypsum and arcanite, and other salts including niter and sylvine. A distinctive enhance of microporosity on the rock surface immediately at the contact with the biological colonizations and efflorescences was observed. A high abundance of biological colonizations was found where the hostrock is well exposed to light, whereas efflorescences prevail in the innermost parts of the cavity. Efflorescences may originate from both anthropogenic air pollution (wet and dry airborne deposition that provides sulfate and nitrate anions) and circulation of soil water whose composition can be modified, for instance, by fertilizers. Analysis of the weathering conditions of calcarenite rocks is a crucial factor in determining the likely possibility of failures and collapses in underground environments.

Fossil Marine Vertebrates from the Juana Lopez Member of the Upper Cretaceous Carlile Shale in Southeastern Colorado, USA

The Juana Lopez Member of the Carlile Shale is a calcarenite rock that became deposited within the Western Interior Seaway of North America during the Late Cretaceous approximately 90 million years ago (early late Turonian). In this study, rock samples collected from a Juana Lopez Member locality in southeastern Colorado, USA, were dissolved with a weak acid to examine the taxonomic composition of vertebrate fossils. Although almost all of the specimens are represented by isolated bones and teeth that are microscopic, the paleofauna was found to be taxonomically diverse. The vertebrate assemblage includes at least 14 chondrichthyans, 20 osteichthyans, and five tetrapods. Some noteworthy occurrences include teeth of Protolamna sp., a pliosaurid plesiosaur, and possible avians. Although teeth of Enchodus spp. are the most abundant vertebrate remains collected, our study clearly indicates the existence of a diverse vertebrate assemblage in a shallow marine environment in southeastern Colorado when the Juana Lopez Member was deposited.

Dynamic Behaviour of Abandoned Underground Mines: Insights from Numerical Simulations

The Apulian region (south-east of Italy) is characterized by the presence of old underground cavities used for the extraction of soft calcarenite rocks and then abandoned over time. The assessment of stability of these caves represents a challenging problem, especially for the areas of possible interaction of the caves with overlying structures and infrastructures. The role of environmental factors in triggering disruption processes in the cave has been extensively studied in the literature, but the instability effect related to dynamic loads is often underestimated. Consequently, the purpose of the present work is to propose some advancements in this field by evaluating the effects of dynamic loads, consistent with the regional seismicity, on the stability of calcarenite underground cavities. A large number of two-dimensional parametric finite element analyses has been carried out on ideal cases of single rectangular cavities. The study allowed to detect appreciable instability effects caused by the dynamic input, depending on the cavity width, the thickness of the roof, and the energy content of the dynamic input. The interaction between twin cavities under dynamic conditions has been also studied from a numerical point of view. The results show that plastic failure in the septum is reached earlier under dynamic conditions than static and it is again dependent on the cavity width and the roof thickness. Lastly, a numerical procedure to calculate factor of safety against either shear failure or tensile failure mechanisms has been proposed, which allows to quantify the change of the stability conditions from static to dynamic conditions.

Effect of Compaction Banding on the Hydraulic Properties of Porous Rock - Part II: Constitutive Description and Numerical Simulations

In this paper the performance of a constitutive model for the description of the hydro mechanical behaviour of soft rock is evaluated with respect to the experimentally observed behaviour of Maastricht Calcarenite under different stress states that is presented in the companion paper. The mechanical model is elasto-plastic and consists of an associated yield surface, internal variables for the description of the hardening and softening behaviour and a non-local extension for the simulation of strain localization in form of shear bands and compaction bands. The model is implemented in the software ABAQUS and the laboratory results from the tests under dry condition with Maastricht Calcarenite are used for the calibration. The good agreement of the numerical results with the laboratory results is shown and the suitability of the model is discussed. To describe the effect of compaction bands on the permeability of soft rocks a simple analytical model based on the Kozeny–Carman equation is proposed and calibrated with the experimental results from drained tests under different stress states for Maastricht Calcarenite rock material. As the results are in good accordance with the experimental results, the model is implemented in the software ABAQUS and the numerical results are presented and discussed. Finally the performance of the model is evaluated and possible improvements are suggested.

On the Stability of Underground Caves in Calcareous Rocks Due to Long-Term Weathering

This paper addresses the problem of the stability of structures on calcareous rocks due to long-term weathering processes. The case study consists of a building resting on a calcarenite rock formation where two abandoned man-made caves exist directly under the structure. The boundaries of the caves were exposed to a slightly acidic environment inducing time-dependent weathering. Analyses were performed following a semi-decoupled approach, where the weathering process, driven by a reactive transport mechanism, was first solved and its results were fed to the mechanical problem which hence accounted for the spatial and temporal evolution or rock damage. For the mechanical problem, a nonlocal constitutive model was employed for the objective simulation of localised deformations. Relevant outcomes are obtained regarding the evolution of the structure’s stability and about the importance of regularising the finite element solution in the presence of brittle materials.

Numerical Simulation of Deformation Band Occurrence and the Associated Stress Field during the Growth of a Fault-Propagation Fold

Knowledge of the paleo-stress distribution is crucial to understand the fracture set up and orientations during the tectonic evolution of a basin, and thus the corresponding fluid flow patterns in a reservoir. This study aims to predict the main stress orientations and evolution during the growth of a fold by using the limit analysis method. Fourteen different steps have been integrated as 2D cross sections from an early stage to an evolved stage of a schematic and balanced propagation fold. The stress evolution was followed during the time and burial of syn tectonic layers localized in front of the thrust. Numerical simulations were used to predict the occurrence and orientation of deformation bands, i.e., compaction and shear bands, by following the kinematic of a fault-propagation fold. The case study of the Sant-Corneli-Boixols anticline was selected, located in the South Central Pyrenees in the Tremp basin, to constrain the dimension of the starting models (or prototypes) used in our numerical simulations. The predictions of the numerical simulations were compared to field observations of an early occurrence of both pure compaction- and shear-enhanced compaction bands in the syn-tectonic Aren formation located in front of the fold, which are subjected to early layer parallel shortening during the burial history. Stress magnitude and stress ratio variations define the type of deformation band produced. Our results show that the band occurrence depends on the yield envelope of the host material and that a small yield envelope is required for these shallow depths, which can only be explained by the heterogeneity of the host rock facies. In our case, the heterogeneity can be explained by a significant contribution of carbonate bioclasts in the calcarenite rock, which change the mechanical behavior of the whole rock.

A study on the state of conservation of the Roman Necropolis of Carmona (Sevilla, Spain)

The Roman Necropolis of Carmona (Sevilla, Spain) has experienced a severe deterioration since the accidental discovery in 1868 and subsequent archaeological excavations starting in 1882. To this deterioration contributed the location in a soft calcarenite rock quarry, the adverse environmental conditions and the numerous and extensive wrong archaeological and managing interventions along more than a century. The cultural, artistic and religious importance of this Necropolis converts the protection and conservation of this archaeological site in a major issue. This work present the data obtained in a multidisciplinary research were geology, geomorphology, micro-environmental and climatic monitoring, rock petrophysical characterization, description of weathering forms and biological colonization were considered in order to propose corrective measures to minimize deterioration.

Elemental Chemical Analysis by X-ray Fluorescence of Calcarenite Stones Used in Historical Monuments Building of Rabat (Morocco)

A good knowledge of chemical properties, thermophysical and petrophysical parameters, makes it possible to understand the mechanisms of alteration of historical monuments, and to predict solutions limiting their evolution. The main objective of this work is chemical analysis by X-ray fluorescence spectrometry on calcarenite stones, often used as a building material for historical monuments of Rabat (Morocco), in order to identify the nature of the rock. The elemental chemical composition shows high concentrations of CaO and SiO2, which confirms that the main phases of the calcarenite rock studied are calcite and quartz. These are the characteristic minerals of calcareous rocks.

A three-dimensional back-analysis of the collapse of an underground cavity in soft rocks

The assessment of stability of man-made underground caves, excavated in the past and later on abandoned, represents a serious challenge for land and urban planning operations, especially for the areas of possible interaction of the caves with overlying structures and infrastructures. Several areas of Southern Italy are characterized by the presence of abandoned underground quarries for the extraction of soft calcarenite rocks, which now threatens the overlying environment due to the risk of collapse and the consequent generation of sinkholes. This work presents a back-analysis of a sinkhole occurred in 2011 in the town of Marsala, caused by the collapse of an underground quarry, as a representative case study of these phenomena. Based on the available geometrical and geological dataset as well as the field observations of the phenomenon, in this article the assumptions and the results about the genesis of the 2011 sinkhole, as derived from a three-dimensional finite element back-analysis aimed at reconstructing the stress-strain evolution that brought to the ground failure collapse, is discussed. In particular, the 3-D numerical analyses have been performed in order to identify the factors responsible of the genetic mechanism of the sinkhole. The finite element analysis has been carried out by accounting for the geotechnical characterization of the Marsala calcarenites derived from both specific laboratory tests performed on samples taken from the site and literature data available on the same rock material; the numerical results have been then validated by means of the comparison with field observations and also compared with those achieved through a 2-D model of the same case study.

Plasticity with generalized hardening: constitutive modeling and computational aspects

In this work, an extended theory of plasticity with generalized hardening is proposed to describe the response of geomaterials under both mechanical and environmental processes, which include as special cases several elastoplastic constitutive equations proposed in the literature to model such processes as desaturation or suction hardening, thermal softening, chemo-mechanical coupling effects in fine-grained soils, as well as weathering of soft rocks. In the formulation of the theory, the coupling between mechanical and environmental processes takes place at two levels: first, as an additional direct contribution to the constitutive stress changes, taking place in both elastic and elastoplastic processes; and second, as a result of the evolution of the internal state variables induced by changes in the environmental process variables. This last effect is incorporated through a set of generalized hardening rules. As an example of application, the general formulation is specialized to the particular case of weak calcarenite rocks undergoing degradation processes due to plastic deformations, changes in degree of saturation (short-term debonding) and chemical dissolution of the bond material and the solid grains (long-term debonding). The resulting model is implemented in a FE code by means of an implicit generalized backward Euler algorithm, suitably modified to incorporate the full formalism of plasticity with generalized hardening. Results of numerical simulations carried out at the element level show the accuracy and efficiency properties of the proposed stress-point algorithm. The simulation of a representative initial-boundary value problem demonstrates the practical relevance of environmental degradation effects in practical applications, over periods of time comparable with the life cycle of most geotechnical structures.

Measurement and analysis of thermal properties of rocks for the compilation of geothermal maps of Cyprus

Previous studies in Cyprus classified the island in the category of low enthalpy with high potentials in the usage of geothermal energy for space air-conditioning. Due to the little existing information about the underground thermal properties, an extended geological sampling has been carried out on the island. Measurements of thermal properties have been performed in the laboratory at room temperature for all the collected samples both in their dry and water-saturated state. The impact on thermal conductivity of water in samples, the mineralogical composition, and the geological age of samples have been the objectives of the current study.Laboratory results of each rock type in Cyprus are found within certain ranges for each thermo-physical property as follows. Thermal conductivity values for dry rock samples vary between 0.4 and 4.2 W m−1 K−1, thermal diffusivity values range between 0.3 and 1.9 × 10−6 m2 s−1 and specific heat capacity values range from 0.5 to 1.5 J K−1 kg−1. Results also show that thermal conductivity and thermal diffusivity under moisture conditions increase for most of the lythotypes. The notable exception is Gypsum (Kalavaso Formation), which exhibits higher thermal response under dry conditions.Measured thermal properties also present a difference between thermal properties of the lithologies of the Troodos Ophiolite and the Circum Troodos Sedimentary Succession in Cyprus. Mean values of thermal conductivity and thermal diffusivity for dry samples and water-saturated samples have higher values for the lithologies of the Troodos Ophiolite than measured values for the lithologies of the Circum Troodos Sedimentary Succession, mostly due to their mineralogical composition.Moreover, the geological age of a lithology has been shown to affect its thermal response. Thermal conductivity of reef limestone and calcarenite rocks increases with the geological age of the lithology.In order to understand and visualize all measured data the Thermal Conductivity and the Thermal Diffusivity Maps of Cyprus have been compiled with the use of a Geographic Information System (GIS) to be available to engineers as a powerful tool for use in the design of thermal engineering systems. From the obtained maps Troodos Ophiolite can be visualized as a separate part by having the highest values.

Prediction of Porosity and Density of Calcarenite Rocks from P-Wave Velocity Measurements

Petrophysical proprieties such as porosity, density, permeability and saturation have a marked impact on acoustic proprieties of rocks. Hence, there has been recently a strong incentive to use new geophysical techniques to invert such properties from seismic or sonic measurements for rocks characterization. The P-wave velocity, which is non-destructtive and easy method to apply in both field and laboratory conditions, has increasingly been conducted to determine the geotechnical properties of rock materials. The P-wave velocity of a rock is closely related to the intact rock properties, and been measuring the velocity in rock masses describes the rock structure and texture. The present work deals with the use of a simple and non-destructive technique, ultrasonic velocity, to predict the porosity and density of calcarenite rocks that are characteristic in historical monument. The ultrasonic test is based on measuring the propagation time of a P-wave in the longitudinal direction. Good correlations between P-wave velocity, porosity and density were found, which indicated them as an appropriate technique for estimating the porosity and density.

Practical estimates of field‐saturated hydraulic conductivity of bedrock outcrops using a modified bottomless bucket method

The bottomless bucket (BB) approach (Nimmo et al., 2009a) is a cost‐effective method for rapidly characterizing field‐saturated hydraulic conductivityKfsof soils and alluvial deposits. This practical approach is of particular value for quantifying infiltration rates in remote areas with limited accessibility. A similar approach for bedrock outcrops is also of great value for improving quantitative understanding of infiltration and recharge in rugged terrain. We develop a simple modification to the BB method for application to bedrock outcrops, which uses a nontoxic, quick‐drying silicone gel to seal the BB to the bedrock. These modifications to the field method require only minor changes to the analytical solution for calculatingKfs on soils. We investigate the reproducibility of the method with laboratory experiments on a previously studied calcarenite rock and conduct a sensitivity analysis to quantify uncertainty in our predictions. We apply the BB method on both bedrock and soil for sites on Pahute Mesa, which is located in a remote area of the Nevada National Security Site. The bedrock BB tests may require monitoring over several hours to days, depending on infiltration rates, which necessitates a cover to prevent evaporative losses. Our field and laboratory results compare well to Kfs values inferred from independent reports, which suggests the modified BB method can provide useful estimates and facilitate simple hypothesis testing. The ease with which the bedrock BB method can be deployed should facilitate more rapid in situ data collection than is possible with alternative methods for quantitative characterization of infiltration into bedrock.

Coastal Caves in Bahamian Eolian Calcarenites: Differentiating Between Sea Caves and Flank Margin Caves Using Quantitative Morphology

Coastal areas on carbonate islands commonly contain two types of caves: sea caves developed by wave erosion processes, and flank margin caves developed by dissolution at the edge of the fresh-water lens. Differentiating sea caves and flank margin caves in coastal settings is important, but can it be done reliably and quantitatively? Current methods use the degree of intricate wall-rock dissolution and the presence or absence of dense calcite speleothems to separate the two cave types. This study reports how analysis of cave maps creates three separate tools to differentiate coastal caves: area to perimeter ratio, entrance width to maximum width ratio, and rectangle short axis to long axis ratio. The study also presents some of the first sea cave data from eogenetic carbonate islands, specifically eolian calcarenites. The morphological and geometrical comparisons between Bahamian flank margin cave and sea cave maps using the three tools allows the two cave types to be statistically differentiated. The Bahamian sea cave data were also compared to sea cave data from California and Maine to demonstrate that Bahamian sea caves have a unique quantitative signature based on the youth and homogeneity of the host eolian calcarenite rock. The Bahamian sea cave data also indicate that sea cave formation may not be solely determined by differential rock weaknesses, as reported in the literature, but may also be a result of wave dynamics such as constructive interference.

Petrophysical and mechanical properties of soft and porous building rocks used in Apulian monuments (south Italy)

Abstract This paper brings a comprehensive review of the main petrophysical and mechanical properties of calcarenite rocks used from time immemorial in Apulia (south Italy), with load-bearing and decorative functions both in constructions of specific historic and architectonic interest and in more common buildings. These soft and porous rocks show a reduced ability to maintain their characteristics of strength, appearance and resistance to decay over a considerable period of time. Even more than other sedimentary rocks, calcarenites belonging to the same formation can change considerably in terms of physical properties and mechanical behaviour due to the complex spatial arrangement of facies strongly conditioned by depositional fabric and diagenetic processes. A number of calcarenite varieties belonging to the Calcarenite di Gravina Fm. and Pietra Leccese Fm. was selected from different parts of Apulia and characterized according to petrographical, physical and mechanical properties. These included porosity, pore size distribution, density, water absorption, degree of saturation, permeability, thermal properties as well as compressive strength and flexural strength. Particular attention was given to the relationships between rock fabric features and physico-mechanical behaviour of the calcarenites. In addition, a comparison of data for the examined varieties was also discussed. A classification of the Apulian calcarenites based on rock fabric features and uniaxial compressive strength was proposed. Critical observations regarding the durability of the Apulian calcarenites were made, taking into account other data from literature.

Model Footing Load Tests on Soft Rocks

Abstract This paper summarizes the results of model footing load tests on soft Calcarenite rock. To perform the experiments, a new testing device was specifically designed, and its conception and features are described in details. The centered loading tests exhibited the typical bilinear shape of the load-settlement curve since a marked change of stiffness occurs as a consequence of collapse of the lightly cemented sand structure. These tests reveal that the failure mechanism is punching shear, and it is bounded in a small region beneath the loaded area. Further tests investigated the influence of the displacement rate and footing size effect, together with tests that show a moisture-induced loss of strength. The eccentric loading tests point out the role played by the interacting external loads, and the coupling between vertical displacement and footing rotation. The overall tests allow the interaction diagram of the soil-foundation system to be derived.

The effects of wetting and drying, and marine salt crystallization on calcarenite rocks used as building material in historic monuments

Abstract The results of a study of the effect of marine salt crystallization on the physical and mechanical properties of Plio-Pleistocene calcarenites cropping out in southern Italy are presented here. Owing to their workability, aesthetic appeal and availability, the calcarenites have been widely used as building stones in many historic monuments. Samples of medium-grained packstones and fine-grained packstones-wackestones were prepared for the salt crystallization test defined by EN 12370, using sea water instead of a 14% solution of Na 2 SO 4 · 10H 2 O. To determine the effect of imbibition alone on the performance of the calcarenites, the same procedure was followed with distilled water without soluble salts. Microfabric analysis, evaluation of index parameters and grain-size distribution were carried out as well. Particular attention was given to pore-size distribution by mercury intrusion porosimetry (MIP), loss of weight and uniaxial compressive strength determined before and after the tests, and after every five cycles of complete immersion in sea water and distilled water. The results suggest that detailed information on fabric and pore network are indispensable to predicting the weatherability of rocks. Crystallization tests that involve the complete immersion of the samples in a saline solution are not effective for an understanding of the real importance of salt damage on soft and porous calcarenites owing to a significant incidence of imbibition in accelerating deterioration rates and in influencing patterns and intensity of weathering.

Speleogenesis in aeolian calcarenite: A case study in western Victoria

Most studies of karst landscapes and their processes have been concerned with consolidated, often well-jointed limestones. There are particular problems involved in the study of karst procesess in softer, less-compact limestones such as chalk, coral reefs, and aeolian calcarenite. Previous studies in aeolian calcarenite indicated these problems and a scheme was developed of speleogenesis in aeolian calcarenite. A study of karst processes in aeolian calcarenite at Bats Ridge in western Victoria has developed this scheme further. The karst features and processes at Bats Ridge are an integral part of the landscape of a mid-Pleistocene calcarenite dune system. The resolution of problems of the rapid subaerial speleogenesis in the area is achieved by the synthesis of the known karst features of the ridge and the geology and geomorphology of the area. Karst development on this aeolianite ridge depends on lithological conditions as well as the availability of aggressive water capable of solution. The diagenesis of the calcarenite is occurring now and must have been occurring by the mid-Pleistocene. This simultaneous lithification of the carbonate dunes into aeolian calcarenite rock and the development of solutional karst features in the dunes is the characteristic feature of the speleogenesis in this area. It is the formation of a hardened kankar layer (cap rock) in the dunes of sufficient compressive and tensile strength to support cavities, which is the result of these interrelated factors, that has strongly determined the formation of the karst features.

Principales características hidrogeoquímicas del acuífero de Balerma-Las Marinas (Almería)

The Balerma-Las Marinas aquifer, which features mainly Pliocene calcarenite rocks, is one of the three distinct hydrogeological units that have been identified in the Campo de Dalias area of Almeria. Its hydrogeochemistry has been established by analyzing one hundred and eight samples from different points along the aquifer. The high sodium chloride content of the water is put down to fairly recent relative changes in the sea and continent levels, which have left saline water trapped by a series of blocks that divide the aquifer into various separate compartments. This relative lack of hydraulic continuity between the aquifer and the sea, together with fact that its resources are not subject to overuse, make it very unlikely that marine intrusion is the cause of the high saline content of the water. The conclusion to be drawn is that these waters are not very suitable either for human consumption or for irrigation.