Dolomitic Rocks Research Articles

Evidence for origin and alteration in the dolomites of salt diapirs, Larestan, Southern Iran

Dolomites are well-known minerals; belonging to the Infra-Cambrian Hormuz Series lies within the salt domes of southern Iran. In this paper, the origin and alteration of dolomitic rocks of Paskhand and Deh-kuyeh salt diapirs in the area of Larestan (southern Iran) are investigated. Based on petrographic (size and fabric) studies, we recognize four dolomite types that consist of very fine-to-fine crystalline dolomite (D1), neomorphic dolomite (D2), fine-to-medium crystalline euhedral-to-subhedral dolomite (D3), and pore- and fracture-filling dolomite (D4). The dolomite samples with up to 26% iron can be called ferruginous dolomites. Some igneous rock patches to gehter with hydrothermal iron veins are observable in the salt domes of Larestan. Oxygen and carbon isotope values of black and white, and altered red dolomite of Paskhand and Deh-kuyeh salt domes, are equal to − 12.35 to − 18.78 for δ18OPDB and − 5.48 to − 8.49 for δ13CPDB; values enriched δ180 with low-temperature (~ 70 °C) conditions are related to D1 dolomites and values depleted δ180 with higher temperatures (~ 270 °C) are related to D3 and D4 dolomites. The most important source for secondary dolomites is deeper hydrothermal and catchment sources, which ascended through faults during the intrusion. Meteoric waters can be mentioned as less important sources for these types of dolomites. We reported sassolite B(OH)3 mineral in Deh-kuyeh salt diapir for the first time in this paper. This mineral is only observed in the areas which have famous riftings Fumarol. Therefore, in this paper, the existence of sassolite in the studied area could be considered one of the most important the origin of the composing elements of Hormuz rocks from fumarols which are formed in an extensional regime.

Complex resistivity spectra for estimating permeability in dolomites from the Mississippian Madison Formation, Wyoming

Dolomite rocks constitute many important reservoirs due to the porosity-preserving and connectivity-enhancing effects of dolomitization. This study explores the correlation between resistivity and pore structure in dolomite rocks from the Mississippian Madison Formation in Wyoming and proposes a novel approach for predicting permeability from complex resistivity spectra (CRS).Digital image analysis (DIA) on thin-sections is used to quantify the pore structure of 54 sucrosic dolomite samples. Pore-structure parameters derived from DIA are correlated to resistivity values of each plug and show that larger and simpler pore networks result in higher cementation factors.Analyses of CRS are performed on brine-saturated core plugs in a log sweep from 0.1– 100,000 Hz with a four-electrode setup at varying confining pressures. Results show that the frequency dispersion of CRS between 10 and 100 kHz is directly related to the porosity in these dolomites. The phase shift of CRS shows high variance in both low and high porosity samples with characteristic slopes βPhase and βAmplitude for frequencies between 10 and 100 kHz. Modifying an empirical model of Tong & Tao (2008) to include porosity and both βPhase and βAmplitude can predict permeability with a correlation coefficient of R2 = 0.84.

Occurrence of Laminated Dolomitic Exhalative Rocks in Continental Rift Basins of Northwest China

Occurrence of Laminated Dolomitic Exhalative Rocks in Continental Rift Basins of Northwest China

The Jettencave, Southern Harz Mountains, Germany: Geophysical observations and a structural model of a shallow cave in gypsum/anhydrite-bearing rocks

Gypsum and anhydrite are soluble rocks, where fissures and bedding partings can be enlarged with time by the dissolution of the mineral species through water. The selective enlargement results in sub-surface voids acting as preferential flow path for the drainage of the rock. With time, larger cavities develop, and a network of cave passages can evolve. If the enlarged cave voids are not too deep under the surface, geophysical measurements can be used to detect, identify and trace these structures. We have used gravity measurements (GRAV), electrical resistivity imaging (ERI), self-potential measurements (SP), electrical conductivity measurements (EC), and ground-penetrating radar (GPR) above the cave Jettenhöhle, a cave located in the southern Harz Mountains in Germany. The Jettencave is developed in the Hauptanhydrit formation of the Permian Zechstein sequence, characterised by large breakdown rooms and an exposed water table. The overburden of the cave is only around 10–15m, and dolomitic rocks are located in close vicinity. We present results from our geophysical surveys in vicinity of the cave. We are able to identify the cave geometry from GRAV, ERI, and GPR measurements, which distinguish the local lithology of the Permian Zechstein rocks in the area. From the ERI and EC measurements, we derive information on the void volume in the soluble rocks. We finally present a three-dimensional structural model of the Jettencave and its surroundings, based on our geophysical results and the hydrological interpretation.

Micro-CT and FIB–SEM imaging and pore structure characterization of dolomite rock at multiple scales

With improvements of imaging techniques and computational power, Digital Rock Physics (DRP) has been increasingly used to determine transport and elastic properties of reservoir core plugs. Since numerical computations highly rely on accurate 3D representations of the porous microstructure of the rocks, the imaging technique and the scale at which the imaging is performed is a critical parameter. In this paper, we introduce a multiscale imaging workflow that uses both micro-X-ray tomography (micro-XCT) and focused ion beam combined with scanning electron microscope (FIB–SEM) to characterize a dolomite rock from the microscale to the nanoscale. This allows for the accurate capture of the different heterogeneities that exist in the carbonate (texture, mineralogy, pore size). The reconstructed microporous structures were then used to successfully predict elastic and permeability properties of selected carbonate.

Microfractures in bed-parallel veins (beef) as predictors of vertical macrofractures in shale: Vaca Muerta Formation, Agrio Fold-and-Thrust Belt, Argentina

Shales of the Upper Jurassic-Lower Cretaceous Vaca Muerta Formation are the main source rock for petroleum in the Neuquén Basin, Argentina and an important unconventional exploration target. Folded Vaca Muerta Formation is well exposed in the Agrio Fold-and-Thrust belt where an arid climate and rapid erosion reveal relatively unweathered shale strata accessible along creek beds at Arroyo Mulichinco and in 10+ m-tall cliffs at Puesto. Widespread within these organic-rich shales are several cm-thick, prominent bed-parallel veins (BPVs) of fibrous calcite (beef) that are cut by multiple sets of vertical calcite lined or filled fractures having apertures unaffected by near-surface stress release. Similar, and probably contemporaneous fractures are present within horizons of interbedded dolomitic rock. Evidence that vertical fractures in BPVs and dolomitic horizons continue into shale beds suggests that in-depth analysis of vertical fractures within BPVs and dolomitic horizons allows fracture set and orientation identification and size population measurements—primarily aperture distributions—that circumvent some of the limitations of shale outcrops. At Arroyo Mulichinco, four main fracture sets are present separable by orientation and crosscutting relations. An E-W set is oldest, followed by successively younger NE-SW, NW-SE, and N-S sets. At Puesto, the E-W and N-S sets are the most prominent and show opposite cross-cutting relationships (E-W set is youngest) indicating a possible episode of younger E-W fractures. The E-W set shows the highest micro-and macrofracture intensity at both localities. The intensity of N-S micro- and macrofractures is similar at both outcrops away from faults, but macrofracture intensity increases closer to faults. While macrofracture abundance is similar in BPVs and in shale, microfractures having apertures smaller than ∼0.1 mm are mostly absent in shale and dolomitic layers but are abundant cutting BPVs. Thus, microfractures are BPV-bounded and only fractures wider than ∼0.05 mm are tall enough to cut into shale. Nevertheless, using size distributions of microfractures in BPVs that are absent in shale accurately predicts the abundance of macrofractures in nearby shale, either because microfractures in organic shale have annealed, or because of only small differences in fracture strain for fractures of different sizes across different rocks types. Microfractures in readily sampled BPVs may be a practical way to diagnose or predict attributes of macrofractures in adjacent shale.

Lithological classification and chemical component estimation based on the visual features of crushed rock samples

Lithological classification and monitoring of ore quality are challenging issues in mine operation, especially to maintain desired feed for processing minerals plants. Quantification of visual features is an innovative method to analyze rock components. In this paper, an analysis of vision-based rock type and classification algorithm is proposed for fast, inexpensive, and reliable identification process compared with common chemical analysis. To evaluate the proposed algorithm, samples were collected from the Novin limestone mine in Iran. Based on chemical and thin-section studies, the samples were classified into three different groups as calcium carbonate, dolomite, and dolomitic limestone. The limestone samples were crushed, sieved, and, respectively, divided into three size fractions as 2.5–7, 1.5–2.5, and 0.1–1.5 cm. A set of 58 images as large and medium size samples and 78 images as fine size samples were taken in the laboratory environment. Features were extracted from the captured images and reduced by applying principal component analysis (PCA). The support vector machine (SVM) and Bayesian techniques were used for classification. The best classification accuracy was about 80 and 90% in limestone and dolomite rock samples, respectively. Then, a multi-layer perceptron (MLP) neural network was employed to predict chemical compositions percentages. The determination coefficient within the range of 0.76 to 0.85 was observed and predicted values confirmed good performance of the grade estimation. The outputs illustrated that the proposed intelligent and automated technique can be successfully applied to monitor ore grade and classify lithology in different stages of mining projects.

The Uitkomst intrusion and Nkomati Ni-Cu-Cr-PGE deposit, South Africa: trace element geochemistry, Nd isotopes and high-precision geochronology

The Uitkomst intrusion is a tubular mafic-ultramafic layered body that hosts one of South Africa’s largest Ni-Cu-Cr-PGE deposits, Nkomati. The sulphide ore occurs in the form of massive lenses in the immediate quartzitic footwall and as disseminations within peridotite. The chromite ore forms an up to ∼10-m-thick layer in the lower portion of the intrusion. Uitkomst has generally been interpreted as a magma conduit, possibly related to the Bushveld event. Here, we present a new high-precision U-Pb zircon date of 2057.64 ± 0.69 Ma that overlaps with the age of the Merensky Reef of the Bushveld Complex and thus demonstrates a coeval relationship between the intrusions. Based on incompatible trace elements as well as O- and Nd isotope data (εNd −4.5 to −6.2), we show that the Uitkomst parent magmas were contaminated with up to 20% Archean upper crust prior to emplacement, and with up to 15% dolomitic country rock during emplacement. Ore formation at Nkomati was critically aided by substantial devolatisation and removal of dolomitic floor rocks leading to hydrodynamic concentration of sulphide and chromite during slumping of crystal mushes into the trough-like centre of the subsiding intrusion and its footwall.

Applications of aluminium oxide and zirconium oxide nanoparticles in altering dolomite rock wettability using different dispersing medium

Application of nanotechnology in oil and gas industry has received great attention from many researchers. This is due to two features of nanoparticles that make them unique which are their size and the ability to adjust their behaviour. Nanoparticles are very active and energetic materials with a high tendency to form nano textured surfaces in combination with surfactants, and causing a major change in the system’s interfacial properties. Surface energy of surfactants can be significantly increased by the interaction of nanoparticle and surfactant and more adsorption on the rock surface occurs with higher surface energy. The objective of this study is to investigate the effectiveness of Al2O3 and ZrO2 nanoparticles to alter oil-wet dolomite rock to more water wet condition. In this study, nanoparticle was dispersed in three different surfactants namely cetyltrimethylammonium bromide, CTAB (cationic), sodium dodecyl sulphate, SDS (anionic) and TX-100 (non- ionic). Critical micelle concentration of the surfactant was determined by measuring its surface tension (SF). The CMC value of the surfactant was established at the inflection point of the curve. The IFT was determined after the addition of nanoparticles. The results revealed that there is significant reduction of IFT after addition of nanoparticles. Reduction of IFT indicates the ability of the solution to decrease capillary forces and increase mobility of the oil in pore throat. Initial wettability of the dolomite substrate was determined and then was submerged in different nanofluids at different concentration. Contact angle of the rock surface was measured as quantitative method to determine the wettability of the system. The experiment was further investigated by evaluating adsorption of the surfactant on the rock surface. Isotherm adsorption of the surfactant was studied and the result revealed that ionic surfactant has higher adsorption capacity. This is mainly because the charged group on solid surface strongly influences the adsorption of surfactant at solid-liquid interface.

Középső-triász dolomitok képződésének története és töréses deformációja a Szegedi-medence területén

A Pannon-medence aljzatának egyik részmedencéje a Szegedi-medence, mely szénhidrogén-földtani szempontból hazánk egyik kiemelt fontosságú területe. A prekainozoos aljzat legelterjedtebb mezozoos képződményei a középső-triász dolomitok, melyek fontos szerepet töltenek be a terület szénhidrogén-rendszerének felépítésében. Jelen tanulmány célja, hogy az évtizedek óta nem vizsgált képződmények képződéséről és deformációtörténetéről új, korszerű leírást nyújtson. Értelmezésünket általános petrográfiai leírásra, fluoreszcens és katódlumineszcens vizsgálati módszerekre, valamint a területről szóló szakirodalomra alapozzuk.A vizsgált anisusi képződmények változatos partszegélyi, sekélytengeri környezetben ülepedtek le. Ezek a leülepedést követő süllyedés következtében, a sekély és közepes betemetődés után, a kora-krétára juthattak a mély betemetődési diagenezis zónájába. Ezen zónákban a képződmények feltehetően többfázisú, részben szövetmegőrző, részben szövet -romboló dolomitosodási folyamatokon mentek keresztül. A petrográfiai alapon elkülönített dolomit típusok közülközepes vagy mély betemetődési környezetet jeleznek a porfirotópos és cukorszövetű dolomitok, valamint a póruskitöltő nyeregdolomit, de ezek szerepe alárendelt a korábbi dolomitosodási folyamatokhoz viszonyítva. A középső-miocént megelőzően a kőzeteket többször is töréses deformáció érte, melynek hatására breccsa, ezt követően pedig üreg- és repedéskitöltő nyeregdolomit képződött. A nyeregdolomit kristályai több esetben kőolajtartalmú fluidumzárványokat csapdáztak. A dolomittestek felszínközeli helyzetét középső-miocén, abráziósparti kör -nyezetben leülepedett fedőkőzetek jelzik, továbbá dedolomitosodás is kapcsolódhat ehhez a szakaszhoz. A Pannon-medence kialakulásával párhuzamos süllyedés és eltemetődés hatására a képződmények ismét nagy mélységbe kerültek, mely során újabb töréses deformáció és cementáció folyt. A legfiatalabb repedéskitöltő ásványegyüttest fluoreszcens tulajdonságú dolomit, valamint pirit és szilárd bitumen alkotja.A vizsgált dolomitok többfázisú diagenezis- és deformációtörténetéhez többfázisú szénhidrogén-migrációs események kapcsolhatóak, melyek pontosabb megismerése és elhelyezése a medence fejlődéstörténetében kulcsfontosságú. Az erősen átalakult nyeregdolomit tartalmú minták további vizsgálata rezervoárgeológiai szempontból a jövőben szintén fontos feladat.

<b>Influence of coarse aggregate on concrete’s elasticity modulus

The modulus of elasticity of concrete is an important property because it is crucial for the control of deformation. The impossibility of obtaining concrete with higher elasticity modulus rates may cause economic liabilities due to the need for larger structural elements. Current paper evaluates three compressive strength classes (20, 30 and 40MPa) of concrete produced with two types of coarse aggregate, basalt and dolomite rock from the Triângulo Mineiro region, Brazil. Further, 459 cylindrical test specimens were cast for the experimental study. The experimental results of the elasticity modulus rates were compared and with formulations prescribed by four standards: ABNT NBR 6118, ACI 318, Eurocode 2 and FIB Model Code. Comparisons demonstrated that the effect of coarse aggregate on the elasticity modulus was negligible when compared to the concrete’s resistance class.

Geological characteristics and main controlling factors of Permian lacustrine tight oil in the eastern part of the Junggar Basin

The Junggar basin is rich in oil and gas resources, and recently, unconventional oil and gas reservoirs have become important targets. Significant amounts of oil and gas are located in Permian formations in the Shazhang–Dajing area, however, fewer studies have focused on unconventional oil and gas reservoirs, particularly on the factors controlling the distribution of unconventional reservoirs. In this study, a sequence stratigraphic framework of the study area was developed based on cores, well logs and seismic data. Source rock samples were analyzed, including tests of kerogen, vitrinite reflectance, chloroform bitumen, organic carbon and group composition. The physical properties and pore characteristics of reservoir samples were also analyzed using scanning electron microscope and high resolution electron microscope. The Permian Pingdiquan Formation comprises three thirdorder sequences in which individual sequence can be divided into a low-stand system tract (LST), a transgression system tract (TST), an early high-stand system tract (E-HST), and a late high-stand system tract (L-HST). Several source rock lithologies have high total organic carbon (TOC), and are matured, having excellent hydrocarbon generation potential. Clastic and dolomitic rocks are the main reservoirs, and nanometer-scale pores are the main reservoir space in the tight reservoirs. The distribution of tight oil is controlled by the sequence stratigraphy, palaeogeomorphic units, and sedimentary facies. The fine sediments, which were generally deposited near the initial flooding surface (FFS) and the maximum flooding surface (MFS), are favorable zones for tight oil. The distributions of the hydrocarbon source rocks are controlled by the depositional environment, depending on the palaeogeomorphic units; the deep depression in the Huoshaoshan area and the moderately-deep depression in the Shishugou area are two distinct hydrocarbon generating centers. The distribution of tight oil is clearly controlled by the sedimentary facies; the tight oil is mainly located in the fan delta front and lacustrine depositional environments. The distribution of tight oil in this area is summarized, and favorable areas of tight oil are proposed.

Attenuation of pollution arising from acid mine drainage by a natural wetland on the Witwatersrand


 
 
 Wetlands are well known to be efficient at sequestering pollutants from contaminated water. We investigated metal accumulation in the peats of the Klip River, a natural wetland that has received contaminated water from gold mining operations in Johannesburg for over 130 years. Previous work conducted in the downstream portion identified the wetland as an important system for sequestering metals. We focused on the upstream section of the wetland, more proximal to the source of acid mine drainage, to provide a better understanding of the pollutant sources and the role of the wetland in pollutant attenuation. Geochemical and mineralogical analyses of peat cores revealed considerable metal enrichments in the peat ash, particularly in Co, Ni, Zn, Pb, Cu and U. Metal concentrations are typically between 4 to 8 times higher than those previously reported for the downstream, more distal portion of the wetland. The distribution of metal accumulation within the peat profiles suggests that contamination arises from a combination of sources and processes. Elevated concentrations in the shallow peat are attributed to the input of contaminated surface water via tributaries that drain the Central Rand Goldfield, whereas enrichments in the deeper peat suggest significant sub-surface inflow of contaminated water through the underlying dolomitic rocks. Metal immobilisation occurs through a combination of mechanisms, which include the precipitation of gypsum, metal sulfides, Fe-Mn oxyhydroxides and phosphates. Our study highlights the environmental and economic importance of natural wetland systems which have the ability to accumulate large quantities of metals and thus remediate polluted waters.
 
 
 
 
 Significance: 
 
 
 
 Considerable levels of metal accumulation are observed within the Klip River wetland peats.
 The wetland is effective in remediating highly polluted water emanating from the Witwatersrand Basin.
 The Klip River system is important for the region’s future water supply.
 
 
 

Ubicazione delle cave di pietra da calce utilizzata come materia prima degli intonaci romani nella Lombardia occidentale

[it] La calce come materiale da costruzione ebbe larga diffusione nell’architettura romana della Lombardia occidentale. La presenza di carbonato di magnesio è stata per lo più riscontrata negli intonaci dipinti provenienti dai siti romani di Milano. Il carbonato di magnesio testimonia l’impiego di dolomia per la preparazione della calce e rocce di questa composizione affiorano per esteso nelle Prealpi lombarde: dolomie e calcari dolomitici grigio chiari (Dolomia del Salvatore, Ladinico-Anisico), dolomie grigie, talvolta con ciclotemi (Dolomia principale, Norico). Non sono conservate evidenze di cave o di forni romani in quest’area prealpina: i Romani sfruttarono gli stessi affioramenti dolomitici, situati lungo la sponda orientale del lago Maggiore, affioramenti da cui si produsse calce a partire dal Medio Evo in avanti. 
 I depositi fluvio-glaciali del medio corso del fiume Adda tra Brivio e Trezzo (massi, ciottoli di calcari marnosi, calcari e dolomie che affiorano nel bacino fluviale) furono un’altra fonte medievale e moderna di materia prima, soprattutto per produrre una calce debolmente idraulica (chiamata “calce forte”), ma questo tipo di calce è assente negli intonaci romani.

Hydrothermal Dissolution of Deeply Buried Cambrian Dolomite Rocks and Porosity Generation: Integrated with Geological Studies and Reactive Transport Modeling in the Tarim Basin, China

The burial dissolution of carbonate rocks has long been an interesting topic of reservoir geologists. Integrated with geological studies and reactive transport modeling, this study investigated the Cambrian dolomites that were buried at depths up to 8408 m and still preserved a large amount of unfilled dissolution vugs from the borehole TS1 in the northern Tarim Basin. Studies indicate that these vugs were formed in association with fault-channeled hydrothermal fluids from greater depth through “retrograde dissolution” as the fluid temperature dropped during upward migration. The reactive transport modeling results suggest an important control of the vertical permeability of wall-rock on fluid and temperature patterns which, in turn, would control the spatial distribution of dissolving-originated porosity. The hydrothermal dissolution mainly occurred in dolomite wall-rocks with higher vertical permeability (extensive development of tensional fractures and connected pore spaces), producing additional dissolved porosity there during deep burial. This study implicates the importance of multidisciplinary approaches for understanding the burial/hydrothermal dissolution of dolomite rocks and predicting favourable deep/ultradeep carbonate reservoirs.

Deformation of the rock pillar caused by bed operation using the room and pillar system

The copper ore deposit of the Legnica-Glogow Copper Mining District a one-deck bed formed from the contact of weak sandstone rocks, and solid, durable dolomite rocks, separated by a layer of copper slate. The bed operation is carried out using the room and pillar system. The course of deformation in such bed operation systems is determined by the mutual interaction of particular elements of the geo-mechanical system which include: the roof slab, the pillars and the excavation bed. Due to the possibility of human intervention, structural pillars – whose strength properties can be determined by the appropriate selection of their dimensions and shape – play a particular role in this system. The optimization of the properties of these pillars is mainly based on the results of laboratory tests of rock samples in the strength test machine and on the basis of visual observations of their behavior in situ. The article presents the experimental results carried out under pit conditions in order to determine the rock pillar reaction. Suitable observations were made using the so-called volumetric method. The obtained results were discussed in relation to the results of strength tests on rock samples, indicating the limited similarity to the deformation characteristics.

Rediscovery and Redescription of the Enigmatic Radula visianica (Porellales, Marchantiophyta)

Abstract: Kockinger, H. 2016. Rediscovery and redescription of the enigmatic Radula visianica (Porellales, Marchantiophyta). — Herzogia 29: 625–634. The supposedly extinct liverwort Radula visianica was rediscovered in the southern and north-eastern Austrian Alps. It was found in five localities, growing on cold, moist, north-facing dolomite rocks in the upper montane and subalpine belts. The new material proved highly variable and only a minority of it comes close to the type material, which is perhaps unsurprising since that originated from a much warmer area at the southern rim of the Italian Alps. An emended description of the species is presented. R. visianica is characterized by its small size, a Lejeunea cavifolia-like habit, the usual absence of gemmae, spreading lobes and in particular an enormous variability in lobule shape which ranges from strongly saccate and shortly orbicular in cold and exposed sites to sickle-shaped and extended to a fine apex in warmer, moister and protected sites. It is ...

Geochemical characterization of the Bormio hydrothermal system (central Italian Alps)

The geothermal springs of Bormio (central Italian Alps) discharge from dolomite rock masses located close to a regional alpine thrust, called Zebru Line. This particular geological setting allows the water to be heated in deep circulation systems and then to upsurge at a temperature of about 40°C at a vigorous flow rate. This paper aims to investigate deep-groundwater circulation of the Bormio hydrothermal system, based on the hydrochemical characterization of discharging groundwater. Water samples were collected during four campaigns in different seasons (June 2012, October 2012, May 2013 and September 2013) and analysed for major ions and stable isotopes. These tracers show that thermal groundwater flows through a deep system crossing both sedimentary and metamorphic lithotypes, and exploiting a fracture network associated to the thrusts between the Ortles Nappe and the overlaying Campo Nappe. The seasonal variations in temperature, electric conductivity and discharge were also compared. The results provide new insights into the hydrogeochemical characterization of large mountain areas where high variability of geochemical properties even at the local spatial scale represent an important challenge.

Microstructural controls on physical and mechanical properties of dolomite rocks

The laboratory characterization of dolostones, cropping out in northeastern Sicily, was carried out with the aim of comparing rocks from two different sampling sites, close to each other but characterized by a different tectonic setting. The main physical and mechanical parameters were estimated and statistically analyzed for a mutual correlation, aimed at achieving the best knowledge on the behavior of such rocks under stress condition. Results show some differences between the two sampling locations, along with wide ranges of values. The presence of fractures within the rock is likely to be the main responsible of the great variability of estimated parameters. This is directly linked to the local complex geological history, which determined the poor characteristics of tested rocks, as well as the critical slope stability issues affecting the studied outcrops.

Nonlinear Ultrasonic Damage Characterization of Limestone

ABSTRACTCharacterization of dolomitic limestone rock samples with increasing levels of damage is presented using a nonlinear ultrasonic approach. Limestone test samples with increasing levels of damage were created artificially by exposing virgin samples to increasing temperature levels of 100, 200, 300, 400, 500, 600, and 700°C for a ninety minute period of time. These samples were first characterized using ultrasonic dilatational and shear phase velocity measurements and corresponding attenuations. Then, a nonlinear approach based upon noncollinear wave mixing of two dilatational waves was used. Criteria were used to assure that the detected scattered wave originated via wave interaction in the limestone and not from nonlinearities in the testing equipment. It was observed that both the dilatational velocity and the noncollinear wave mixing approach are able to characterize the level of damage in limestone rock. However, the nonlinear approach is more sensitive to damage accumulation by about two orders of magnitude.