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1.
Studies of many years—combining in situ investigation and laboratory analysis—have provided comprehensive information on weathering damage on the rock-cut monuments in the ancient city of Petra in Jordan. These rock-cut monuments represent outstanding world heritage. Many hundred monuments were carved by the Nabataeans from bedrock about 2000 years ago. The awareness of increasing weathering damage on the monuments has resulted in international efforts towards their preservation. The damage diagnosis has addressed the complex mutual relationships between stone types, stone properties, monument exposure regimes, environmental influences, weathering phenomena, development and extent of weathering damage and weathering progression. The rocks were classified lithostratigraphically and petrographically. Results on weathering forms, weathering profiles and weathering products obtained from monument mapping, in situ measurements and laboratory studies revealed a complex diversity of weathering phemomena with respect to type and intensity. Damage categories and damage indices were used to create a reproducible quantitative rating of weathering damage. Detailed results on weathering forms allowed the characterization and quantification of weathering progression including weathering prognoses. Stone properties and states of weathering damage were jointly considered for the rating of the rocks’ susceptibility to weathering. The systematic evaluation of weathering damage and monument exposure regimes can enhance the assessment of weathering factors and processes.  相似文献   

2.
Re-colonization of freshly cleaned surfaces by aeroterrestrial microbial communities is up to now poorly understood. Here, we present a comparative study addressing the composition of algal and fungal communities on a marble sculpture, based upon the analysis of 18S rRNA gene clone libraries from environmental samples. The samples were taken from a blackish and greenish biofilm cover before surface cleaning and 1 year after cleaning treatment, when traces of re-colonization became visible to the naked eye. The composition of the fungal community indicated clear differences between the old grown biofilm and the treated surface. While the former was dominated by the ascomycetes Rhinocladiella, Glyphium and Capnodiales, the black yeast Sarcinomyces was clearly dominant 1 year after cleaning, but could not be retrieved from the old grown black biofilm. The green algal community was dominated by different phylotypes of the lichen algae Trebouxia, as well as the cosmopolitan green algae Apatococcus and Stichococcus. No essential differences in the green algal community before and after cleaning could be observed.  相似文献   

3.
A number of researchers have used tombstones to study the deterioration of stone. The tombstones can provide a large number of samples for statistical analyses. Measurements have included index of legibility, microrelief of resistant inclusions, and loss of thickness. Lack of information about past exposure conditions makes it difficult to derive quantitative relationships. The most useful results involve ranking of stone durability, and identification of time periods or geographic regions with high rates of stone deterioration.  相似文献   

4.
One of the properties that makes marble such an excellent construction and ornamental material is its low porosity. It is very difficult for water or decay agents to penetrate the internal structure of materials with no or few pores, so enhancing the durability of these materials. However, environmental temperature fluctuations bring about significant physical changes in marbles that result in an increase in porosity, due to the appearance of new microcracks and the expansion of existing ones. These cracks offer new paths into the marble which make it easier for solutions containing pollutants to penetrate the material. Thermal expansion tests were performed on three different types of marble known as White, Tranco, and Yellow Macael (Almeria, Spain), after which an increase in porosity (from 17 to 73% depending on marble type) was observed, mainly due to crack formation. The structural changes occurring during thermal expansion tests were more significant in the case of White Macael samples, a fact that is not only related to its mineralogical composition but also to the morphology of the grains, grain boundaries and crystal size. Our research suggests that thermally weathered White Macael marble could be more susceptible to decay by other contaminant agents than Tranco or Yellow Macael. The use of hot-stage environmental scanning electron microscopy is proposed as a valid tool for observing, both in situ and at high magnification, changes in the fracture system of building stones induced by thermal stress.  相似文献   

5.
In the natural environment, temperature and moisture are very important parameters in stone degradation. Therefore, on 28 samples from different lithologies (magmatic, metamorphic and sedimentary rocks) thermal and hygric expansion measurements were performed in order to constrain their behaviour related to environmental changes. It was shown that marbles, even those that are dolomitic, are sensitive to temperature impacts. For rocks with clay minerals the effect of temperature may be responsible for shrinking. Finally the amount of residual strain, i.e. the formation of microcracks due to temperature action controls the rate of stone degradation. For most sedimentary rocks no residual strain after heating was observed. In contrast to most magmatic and metamorphic low-porosity rocks, sedimentary rocks contain swelling minerals (like smectite and even phyllosilicates), which are very sensitive to hygric attacks. The cycles of wetting and drying, i.e. the natural environmental effects, may significantly control the deterioration velocity caused by hygric expansion.  相似文献   

6.
This work analyzes the stone superficial deterioration of some monuments in Rabat city. The rock is a calcarenite with porous texture, rich in calcium carbonates and fossils. The techniques used to study the surfaces altered by blackening or black crusts, are the SEM equipped with EDX microprobe, the X-ray diffraction, and the analysis of the soluble salts by ionic chromatography for anions and flame spectrometer for cations. They reveal significant contents of calcium sulphates, mainly gypsum, often associated with sodium chlorides. These salts known to have a destructive effect on the calcareous stones seem to be originated from the contamination by atmospheric pollutants, particularly sulfur dioxide, and by the marine sprays.  相似文献   

7.
Geotechnical and geological properties of limestone samples from the Mokattam Quarry in Cairo, Egypt, were determined in order to provide prior information for the selection of suitable methods for the conservation of stone monuments around Cairo. A commercial chemical consolidant (Wacker OH 100) was applied to fill the pore spaces and to strengthen the weathered rock. Filling of pore spaces was confirmed by the decrease of both porosity and permeability of rock samples after the application of the consolidant. Analysis by mercury porosimeter showed most effective consolidation results for pore spaces from 0.75 to 1.0 µm in diameter, which were those mainly observed in the samples. Ultrasonic velocity did not show any significant evidence but an increase in strength, observed as an increase in the point load index after the consolidation process was completed, confirmed that the filling and consolidation process worked effectively. Point load testing can thus be used in preference when the number of samples available for laboratory testing is limited. From the color analysis, it was shown that there was no noticeable color change after the application of consolidant Wacker OH 100. The combinations of laboratory tests adopted in this study can be applicable to the planning of conservation of other stone monuments.  相似文献   

8.
The paper presents numerical simulations investigating the settlement reduction caused by stone columns in a natural soft clay. The focus is on the influence of the soft soil alteration caused by column installation. A uniform mesh of end-bearing columns under a distributed load was considered. Therefore, the columns were modelled using the “unit cell” concept, i.e. only one column and the corresponding surrounding soil in axial symmetry. The properties of the soft clay correspond to Bothkennar clay, which is modelled using S-CLAY1 and S-CLAY1S, which are Cam clay type models that account for anisotropy and destructuration. The Modified Cam clay model is also used for comparison. Column installation was modelled independently to avoid mesh distortions, and soft soil alteration was directly considered in the initial input values. The results show that the changes in the stress field, such as the increase of radial stresses and mean stresses and the loss of overconsolidation, are beneficial for high loads and closely spaced columns but, on the contrary, may be negative for low loads, widely spaced columns and overconsolidated soils. Moreover, whilst the rotation of the soil fabric reduces the settlement, in contrast the soil destructuration during column installation reduces the improvement.  相似文献   

9.
The results of the geological characterization of an old stone building in southern Italy, are presented here. The Mondragone marble is a slightly metamorphosed carbonate rock, which was widely employed as monumental stone in the 18th century Royal Palaces of Naples and Caserta. In this paper, for the first time, this rock has been investigated with a thorough laboratory testing program, aimed at defining its mineralogical, physical and mechanical parameters. The two most important varieties of Mondragone marble were separately tested: the yellow and grey marbles (hereafter, YM and GM, respectively). The results obtained from physical tests (open porosity, dry density, specific gravity, water absorption coefficients, ultrasonic velocity) did not show marked differences between the two materials; in contrast, the mechanical strength tests (uniaxial compressive strength, point load strength, flexural strength) showed better behaviour of YM than for GM. After a tentative comparison with other well known carbonate rocks from Italy, some considerations on the response of Mondragone marble to local weathering were conducted. In particular, the weathering typologies were related to the particular texture of the brecciated marble and the different strength resistances displayed by the various constituents of the rock.  相似文献   

10.
An archaeometric study of the stone materials employed in the Late Baroque historical monuments of the ancient city centre of Catania was carried out. Lithological maps of a selection of monuments, transferred to a digital format, revealed that the stone materials are both magmatic and sedimentary rocks, the colours of which are matched in a peculiar type of bichromy. Particular attention focused on sedimentary rocks, which consist of various types of limestone quarried near the city of Syracuse (Hyblean Plateau, south-eastern Sicily). Carbonate rocks were characterised in terms of mineralogy, petrography and geochemistry, by studying rock samples from both monuments and historical extraction sites. Results showed that, although only one name was historically attributed to the above lithotypes (i.e. “Pietra di Siracusa‘’), they were quarried from many locations and, as they belong to various geological formations, they therefore exhibit great variety. In order to examine the durability of Hyblean limestones employed in works of cultural heritage interest, salt crystallisation tests were carried out according to standard procedure norms (UNI EN 12370 (1999) Determination of resistance to crystallisation of salts, 6p). Results are consistent with the forms of deterioration observed in the monuments, and highlight the close relationship between textural characteristics and damage. Our purpose is to provide a basic tool, which may be useful both for conserving monuments of cultural heritage and for their restoration.  相似文献   

11.
《Engineering Geology》2002,63(1-2):83-91
This study deals with a weathering problem of historic arch stone bridges built of welded tuff about 150 years ago in Kagoshima, Japan. Based on a detailed comprehensive weathering evaluation we previously carried out, the way in which the weathering affects the structural stability of the bridges is quantitatively evaluated herein by using a distinct element method (DEM).The suitability of this method of analysis was confirmed through a comparison of the numerical analysis results with the in situ load testing data. The analysis results show that when considering the stability of a stone bridge, the slide safety factor and eccentric safety factor are more important than the compressive safety factor. That is, the types of possible failure include sliding and openings between arch blocks. In 150 years of weathering, the shear stress in the arch ring generally increased about 20%. The eccentric safety factor decreased about 9%, from 4.35 to 3.97, and the slide safety factor decreased about 20%, from 8.02 to 6.46. Deflections at the arch crown increased about two times, from 0.60 to 1.28 mm. Despite these changes, the stone bridges are considered to be still in a good condition after 150 years of weathering.  相似文献   

12.
Interaction of rock and atmosphere: patinas on Mediterranean monuments   总被引:2,自引:0,他引:2  
 This paper analyzes – chemically, mineralogically, and petrolographically – the patinas developed on several Mediterranean monuments made with different stones (siliceous and carbonatic) in order to establish their origin and their evolution under the present environmental conditions, and to evaluate the environmental parameters controling their development. Most of the patinas show a common sequence of layers, which, from the outer to the inner zone, are: (1) present bioactivity and/or biological remains, (2) gypsum-rich patina, and (3) calcitic brown to orange patina. Each one may exhibit different fabrics (from micritic to stromatolitic) and may be more or less continuous and homogeneous. The main mineral components are calcite and gypsum, but Ca-oxalates and Ca-phosphates have also been found associated to biological structures, as well as quartz and clays. The different fabrics and textures have been interpreted as consequence of changes in the environmental conditions which seem to be related to the biological activity, facilitating the growth of different organisms and leading to the development of a deposit with distinct characteristics (fabric, texture, porosity, etc.). The gypsum-rich patina has been interpreted as a sulphation of the underlying calcitic layer by the action of atmospheric pollutants or as dry or wet deposition from the atmospheric dust. The mineralogy and texture of the patina is independent of the nature of the underlying rock and only in few cases a micritization process has been observed as interaction between patina and rock. Recently, the penetration of endolithic microflora produced drillings and the development of a fissuration system parallel to the surface, and thus the detachment of the crust from the rock and even flackening of the rock itself has been observed. Consequently, under the present climatic conditions in the Mediterranean basin, erosion is a more active process than deposition, and the crusts and patinas show a tendency to disappear from the surface of the monuments. Received: 3 November 1996 · Accepted: 10 September 1997  相似文献   

13.
Art F. White   《Chemical Geology》2002,190(1-4):69-89
Chemical weathering gradients are defined by the changes in the measured elemental concentrations in solids and pore waters with depth in soils and regoliths. An increase in the mineral weathering rate increases the change in these concentrations with depth while increases in the weathering velocity decrease the change. The solid-state weathering velocity is the rate at which the weathering front propagates through the regolith and the solute weathering velocity is equivalent to the rate of pore water infiltration. These relationships provide a unifying approach to calculating both solid and solute weathering rates from the respective ratios of the weathering velocities and gradients. Contemporary weathering rates based on solute residence times can be directly compared to long-term past weathering based on changes in regolith composition. Both rates incorporate identical parameters describing mineral abundance, stoichiometry, and surface area.

Weathering gradients were used to calculate biotite weathering rates in saprolitic regoliths in the Piedmont of Northern Georgia, USA and in Luquillo Mountains of Puerto Rico. Solid-state weathering gradients for Mg and K at Panola produced reaction rates of 3 to 6×10−17 mol m−2 s−1 for biotite. Faster weathering rates of 1.8 to 3.6×10−16 mol m−2 s−1 are calculated based on Mg and K pore water gradients in the Rio Icacos regolith. The relative rates are in agreement with a warmer and wetter tropical climate in Puerto Rico. Both natural rates are three to six orders of magnitude slower than reported experimental rates of biotite weathering.  相似文献   


14.
The expansion of the Neyriz marble mine into deeper levels caused an unexpected failure particularly in the toes of lower benches. This phenomenon can impact the overall stability of the quarry and results in undesirable environmental and technical consequences. To understand the failure mechanism, a comprehensive study including—laboratory testing, in situ field testing and theoretical analyses are carried out. The theory of the brittle failure which was mainly developed based on the experiences gained during excavation in granite rocks is adopted and augmented in this study to explain the governing mechanism of failure. Mechanical properties of the marble are determined using conventional rock mechanics tests, and the in situ stress field was evaluated using a modified under coring test. Analyzing the laboratory and field data with the available empirical criteria for brittle failure shows that the level of stress in the lower bench is high enough to initiate the brittle failure. Finally, constitutive models developed for this failure mode are adopted in conjunction with numerical modeling to investigate the observed failure in the quarry. Two modeling strategies, based on elastic and elastic–plastic analyses, are considered. Comparing the predicted failure surface with the observed failure profile, it can be concluded that the brittle failure criteria can very well capture the failure mechanism in this marble quarry. This shows that the criteria proposed to describe spalling failure around underground excavation in granite can be effectively employed for assessing the brittle failure in deep open cast and quarry mines in good quality rocks such as marble.  相似文献   

15.
In the presented case study, ascomycete fungi and green algae on a marble monument were identified by comparisons of the 18S rRNA gene sequences, which were obtained from DNA either from environmental samples or from enrichment cultures. The organisms were found to be responsible for either black or green surface coverings on different areas of the monument surface. Most fungi were related to plant-inhabiting genera, corresponding to a heavy soiling of the marble surface with honeydew. Whereas green algae of the genera Stichococcus, Chloroidium and Apatococcus were found to be dominant in all samples, isolates of two additional genera were recovered only from enrichment cultures. A reference strain of Apatococcus lobatus and an isolate of Prasiolopsis sp. were investigated with respect to putative surface adhesive structures of the cell envelope. The Prasiolopsis cell walls were covered with a thin adhesive exopolysaccharide layer involved in biofilm formation.  相似文献   

16.
Microstructure‐based finite-element analysis with a microcracking algorithm was used to simulate an actual degradation phenomenon of marble structures, i.e., microcracking. Both microcrack initiation and crack propagation were characterized, as were their dependence on lattice preferred orientation (LPO), grain shape preferred orientation (SPO), grain size, marble composition (calcite and dolomite) and grain‐boundary fracture toughness. Two LPOs were analyzed: a random orientation distribution function and an orientation distribution function with strong directional crystalline texture generated from a March–Dollase distribution. Three SPOs were considered: equiaxed grains; elongated grains and a mixture of equiaxed and elongated grains. Three different grain sizes were considered: fine grains of order 200 μm (only calcitic marble); medium size grains of order 1 mm (calcitic and dolomitic marbles); and large grains of order 2 mm (only dolomitic marble). The fracture surface energy for the grain boundaries, γig, was chosen to be 20 and 40 % of the fracture surface energy of a grain, γxtal, so that both intergranular and transgranular fracture were possible. Studies were performed on these idealized marble microstructures to elucidate the range of microcracking responses. Simulations were performed for both heating and cooling by 50 °C in steps of 1 °C. Microcracking results were correlated with the thermoelastic responses, which are indicators related to degradation. The results indicate that certain combinations of LPO, SPO, grain size, grain‐boundary fracture toughness and marble composition have a significant influence on the thermal-elastic response of marble. Microstructure with the smallest grain size and the highest degree of SPO and LPO had less of a tendency to microcrack. Additionally, with increasing SPO and LPO microcracking becomes more spatially anisotropic. A significant observation for all microstructures was an asymmetry in microcracking upon heating and cooling: more microcracking was observed upon cooling than upon heating. Given an identical microstructure and crystallographic texture, calcite showed larger thermal stresses than dolomite, had an earlier onset of microcracking upon heating and cooling, and a greater microcracked area at a given temperature differential. Thermal expansion coefficients with and without microcracking were also determined.  相似文献   

17.
The strontium isotope ratio in sea water has varied through geologic time owing to the input of strontium from rock weathering. To evaluate the possibility that Sr87Sr86 ratios might be altered during weathering, seven weathering profiles developed on Mesozoic arkoses located along the length of New Zealand were investigated. The rubidium-strontium-strontium isotope relations in these profiles give ‘isochron’ ages less than the ages of deposition of the arkoses. These ages appear to result from the weathering of a homogeneous source rock. The age calculated from the rubidium-strontium system (t′) is related to the original age (t) by the equation t′/t = (n ? 1)/n, where n is the ratio of the amounts of common and radiogenic strontium leached from the rock. Shales formed by the accumulation of these residual solids may inherit misleading isochron relationships which may not be erased during deposition or early diagenesis. The strontium which goes into solution and is transported to the sea is slightly less radiogenic than the strontium in the unweathered rock, while the residual clays may be much more radiogenic.  相似文献   

18.
成都金堂李家梁子M23号墓出土的汉朝石棺存在表面粉化、剥落等病害现象,急需保护修复。现场调查表明,该石质文物风化病害主要表现为裂隙状风化、页片状风化、粒状风化、粉末状风化等。本文借助X射线衍射(XRD)、偏光显微镜、扫描电镜等对金堂石质文物进行了微观成分及结构分析。结果表明,文物材质为红色砂岩,其碎屑物主要为石英、钠长石、岩屑和少量云母,胶结物以钙质为主,含少量的炭质及泥质。该砂岩产生风化病害的主要原因是钙质胶结物的溶解流失及泥质胶结物遇水的崩解,同时还受岩屑、长石类碎屑风化蚀变的影响。该研究可为石棺的后期保护修复工作提供基础科学数据。  相似文献   

19.
Folding experiments have been carried out on single-layers of Carrara marble and Solnhofen limestone at a confining pressure of 275 bars, temperature of 400°C, and strain rates of 5.5×10−7 to 8.2×10−7. The marble and limestone layers were embedded in a rock-salt matrix and in a matrix of a mixture of 60% fine-grained halite and 40% fine-grained calcite, respectively, and deformed to different percentages of bulk shortening. Aspect ratios of the layers varied between 11.25 and 15. The stress-strain relationship reveals that strain increased with a very small increment in compressive stresses, once folding was initiated.With progressive deformation the bulk strain is compensated by folding along one fold hinge. The resulting folds are concentric and a combination of class 1a, 1b and 3 type. The changes in the arc length, layer thickness, limb dip and wavelength with progressive folding in marble layers, are discussed.The microstructure and texture of the folded marble and limestone layers have been investigated optically and by means of an X-ray texture goniometer. The inner fold arc exhibits a strong preferred orientation, whereas in the outer fold are the preferred orientation is poorly developed. Differences in the fabric in medium-grained marble and fine-grained limestone layers have been attributed to the difference in mechanism of deformation.  相似文献   

20.
A record of mortar and salt analyses from the last 20 years on various monuments in Saxony demonstrates the close relation between the occurrence of magnesium sulphate salts and the use of dolomitic lime mortars in a regional frame. The regional distribution scheme of dolomitic lime in historic mortars depends on the geological setting of the territory, i.e. the natural occurrence of dolomite deposits. Sulphation of these mortars with the formation of magnesium sulphate and gypsum is mainly due to environmental pollution, as can be shown by sulphur stable isotope analyses. Exposure of the sulphated mortar surfaces to rain leads to the preferential dissolution and advective transport of the novel formed magnesium sulphate salts, which effloresce or subfloresce on the mortar surface or can be accumulated in the structure of adjoining porous building materials like natural stones. These processes may cause severe damages in mortars by the weakening of the binder and in porous stones by salt crystallisation of phases like epsomite and hexahydrite.  相似文献   

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