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1.
G.M.E. Kamh 《Environmental Geology》2005,47(4):482-492
Weathering processes and intensity vary according to the predominant environmental conditions as well as the rocks physical and geotechnical properties in a given area. Jedburgh Abbey Church has been taken as a representative historical building constructed from Carboniferous Old Red Sandstone at humid pre-glacial region. The research aims to examine weathering processes and intensity under the environmental conditions of high relative humidity and low temperature, and to determine the output of weathering through an examination of the rocks petrological and geotechnical properties.Thin section study, scanning electron microscope and X-ray fluorescence techniques have been used to examine the rocks petrography and mineralogy on one hand and to determine weathering products on a microscale on the other hand. It is noted that the Carboniferous Old Red Sandstone has a quartz arenite texture with iron oxide and dolomite within its texture, authigenic clays are also detected. Pitting of quartz grains, exfoliation of silica overgrowth and fragmentation of the rocks feldspar can be noted on a microscale resulting in recession of the rocks components cohesion.The geotechnical results indicated variation in the physical nature of the construction rock from inside to outside the church with recession from the former to the latter due to weathering. The great reduction in mortar and the rocks calcium oxide and high content of both sulphur and chlorine from inside to outside the church is a result of weathering and deposition of air pollutants on the stones surface on the outdoor surfaces. Chemical weathering, e.g. salt hydration and chemical alteration of the rocks carbonate content to sulphate and chloride salts is expected to dominate in the study area at such conditions of low temperature and high relative humidity accompanied with air pollutants. 相似文献
2.
G.M.E. Kamh 《Environmental Geology》2005,48(4-5):625-638
The weathering factors act on the recent and archaeological sites through different processes based on the dominant environmental
conditions. The net result of weathering is deformation of the original form of construction rock. In the current case study,
the main aim is to find out the mechanism of formation of two different weathering forms recorded on many old buildings taking
Chester City as a case study. The construction rock in the case study is arenitic sandstone with carbonate content ranging
from 0.0 to 15.6%. The sandstone blocks are cemented together by hydraulic lime mortar that can easily be altered chemically
to salts by acid rain that dominates at the study area. In case of mortar with worse geotechnical limits than the sandstone
blocks, the net result is convex “domal” shape blocks, but in case of mortar with better geotechnical limits than the construction
sandstone, the net result of weathering is tafoni “concave” weathering form. 相似文献
3.
I˙stanbul, the capital of the east Roman, Byzantine and Ottoman Empires embraces two continents, one arm reaching out to
Asia, the other to Europe. It is therefore, a rich city in terms of monuments and historical cites. Shell limestones of Upper
Miocene age are used as building stone in the majority of the monuments in I˙stanbul because of their attractiveness, availability
and workability. The durability characteristics of the limestones are examined, and those factors that are responsible for
atmospheric weathering are discussed, in a humid and marine environment with important problems of urban pollution, specifically
due to traffic. In the present study weathering of the building stones were first examined in situ by macroscopic observations.
The weathering that developed as a result of environmental effects since this limestone was first used in historical monuments
has been affected 0.1–1.5 cm deep from the surface. The weathered facing stone of Şehzade Mehmed Mosque in I˙stanbul is undergoing
a program of progressive replacement. During this study, samples were taken from this monument where the shell limestone was
used. The stone surface was principally examined by means of Scanning Electron Microscopy (SEM). Petrographical and mineralogical
analyses were made by using optical microscopy and X-ray diffraction method. The physico-chemical properties of these rocks
control their weathering behaviour and reactivity. Major and trace element analyses and the effect of deterioration on the
physical properties of the limestones (unit weight, porosity and water absorption) have also been investigated. Studies on
the samples implies that weathering on the stone surface caused important variations on the physical characteristics of the
rock.
Received: 11 February 1998 · Accepted: 18 August 1998 相似文献
4.
K. S. Sajinkumar S. Anbazhagan A. P. Pradeepkumar V. R. Rani 《Journal of the Geological Society of India》2011,78(3):249-257
The climatic condition of Western Ghats has influenced the process of weathering and landslides in this mountainous tract
along the southwest coast of India. During the monsoon period, landslides are a common in the Western Ghats, and its intensity
depends upon the thickness of the loose unconsolidated soil formed by the process of weathering. Debris landslides with a
combination of saprock, saprolite and soil, indicate the role of weathering in landslide occurrences. This paper reports on
how the weathering in the windward slope of Western Ghats influences the occurrence of landslides and the factors which accelerate
the weathering process. Rock and soil samples were collected from the weathering profile of hornblende gniess and granite
gneiss. The chemical analysis and the calculated Chemical Index of Alteration (CIA) indicate the significant weathering and
its possible influence on landslide occurrences in the study area. Mainly, the CIA value of lateritic soil and forest loam
indicated the extent of high chemical weathering in this region. Rainfall is the dominant parameter influencing the chemical
weathering process. In addition, deforestation, land use practices and soil erosion are some of the other important factors
accelerating the weathering process and landslide occurrences in the region. The locations of the previous landslides superimposed
on geology and soil show that most of the landslide occurrences are associated with the highly weathered zone, particularly
lateritic soil and the ‘severe’ (rock outcrop) erodability zone. 相似文献
5.
工程上常见的灰岩在不同风化程度下的抗剪强度特性鲜有研究,也没有快速评估灰岩抗剪强度的数学模型,不能满足大量灰岩工程灾害防治的需要。为探究风化程度对灰岩抗剪强度特性的影响规律,试验选取现场新鲜灰岩试样,通过开展室内风化模拟试验制备不同风化程度的岩样,进行室内岩石强度剪切试验,探究灰岩剪切应力-剪切位移关系曲线的变化规律和... 相似文献
6.
Precipitation of salts in confined spaces is the key mechanism for rock weathering and damage to building materials. To date there is no comprehensive study of the parameters influencing the reduction of pore space by salt crystals and the consequences for transport and damage by crystallization pressure. A novel method is presented to quantify pore clogging (i.e., the degree to which crystallization of salts interferes with transport of solution in porous materials). After drying capillary-saturated stone specimens containing salt solutions, the rate of capillary uptake of decane into the salt-contaminated specimens is measured. By treating the salt-contaminated material as a bilayer, the width of the crystallization front and the degree of pore filling can be determined. Two model materials with different pore size distributions (Indiana and Highmoor limestone) and three salts (sodium chloride, sodium sulfate and magnesium sulfate) are selected for this study. It is shown that pore clogging results from the interplay between pore size distribution and salt properties. Different scenarios are discussed to link pore clogging with salt damage. 相似文献
7.
Cairo City has a large number and different forms of Islamic archaeological sites, in particular, at El-Gammalia and El-Moez
streets, as well as Coptic archaeological sites, e.g. at Mari Gergis. Human interference and activities at these historical
areas resulted in flooding such sites’ foundations with domestic water, deteriorating its basal courses by salt weathering.
The 1992 earthquake is another natural environmental hazard severely affecting many of these sites. The aim of the current
study is to examine some factors (of bedrock and buildings) that are expected to control building susceptibility to damage
by earthquakes by taking 38 Islamic archaeological sites in the El-Gammalia area as a representative case study. Detailed
field recordings of site damage category before and after the quake and continued recording of damage features generated by
the 1992 quake over the last 14 years, measuring depth to sub-surface water, measuring buildings’ height before the quake
and bedrock sampling at these sites for geotechnical investigations were all considered for achieving this aim. The data has
been processed mathematically and graphically (using the Excel package) to examine the main factors responsible for building
susceptibility to damage by earthquakes. The selected archaeological sites give an excellent representation of the factors
controlling building susceptibility to damage by quakes; it is found that the sites with heights (before the quake) ranging
from 12 to 14 m are the most affected ones; the sites with the highest damage category before the quake were more susceptible
to more damage by the quake; the sites that had been built on alluvium soil were more affected than those built on the Eocene
limestone. The age of these sites has, to a small extent, indirect control on sites’ susceptibility to damage by the quake,
particularly in parts flooded with domestic water (i.e. affected by salt weathering). The depth to sub-surface water is an
effective parameter on sites’ basal courses (through salt weathering), which, indirectly, control a building’s susceptibility
to quakes, particularly where the depth of water ranges from 0.6 to 1.6 m in alluvium bedrock. The alluvium soil at the study
area has a liquid limit ranging from 62% to 82%, plastic limit from 37% to 86% and plasticity index from 26% to 46% and free
swelling from 27% to 81%. These geotechnical limits for such alluvium bedrock indicate that its clay minerals are mostly montmorrillonite. 相似文献
8.
Experimental Study of Temperature Effects on Physical and Mechanical Characteristics of Salt Rock 总被引：1，自引：2，他引：1
Summary. Because of its advantageous physical and mechanical characteristics, salt rock is considered an excellent host rock for nuclear
waste disposal. Nuclear wastes in a salt rock repository will continue to emit radiation and thermal energy for decades after
placement, resulting in a significant rise of the surrounding salt rock temperature. Consequently, study of the physical and
mechanical characteristics of salt rock under different temperature conditions is essential to ensure the integrity of the
salt rock repository and the safe isolation of nuclear wastes from the biosphere.
Through a series of physical and mechanical tests on thenardite salt rock at different temperatures (ranging from 20 °C to
240 °C), it is found that the mechanical parameters have different reactions to a changing temperature. Tests show that the
ultrasonic velocity of samples decreases with temperature increase and both the uniaxial compressive strength and axial strain
increase with temperature, whereas the tangent modulus Et goes in an opposite direction. Meanwhile, the plastic strain increases gradually and strain-softening behavior of the samples
becomes increasingly evident. In the pre-set angle shear tests, both the cohesion and internal friction angle increase with
temperature. Results obtained in direct shear illustrate that both the peak shear strength and the ultimate shear strength
increase with temperature.
We conclude that the behavior of thenardite salt rock at high temperatures is still advantageous to the integrity of salt
rock repository, assuring the safe isolation of nuclear wastes from the biosphere. 相似文献
9.
Salt and ice crystallisation in porous sandstones 总被引：1，自引：0，他引：1
Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect
of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing
scientific research done during the past century has shown that there are numerous parameters that have an influence on the
weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its
material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally,
laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done
to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation,
and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed
detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings
can help to understand the damaging mechanisms. 相似文献
10.
Three geo-archaeological sites at the North Coast and Alexandria, namely, the Alexandria wall (El Shalalat Park site), Abu Soir temple, and Marina excavations, were investigated to determine the negative impact of a salty environmental condition. The monuments suffer from rock decay of different rates. The geo-archaeological sites were built mainly from oolitic limestone blocks (i.e., the Alexandria wall at the El Shalalat Park site and Abu Soir temple) or excavated on them (i.e., Marina excavations). Field inspection and a lab analysis were carried out to understand the weathering mechanism. Salt weathering criteria such as disintegration, pitting, scaling, exfoliation, and honeycomb are observed on the Alexandria wall and upper parts of the Abu Soir temple, while dangerous cracks are detected on the Marina excavation tombs. The petrographic study of the oolitic limestone samples shows that they consist mainly of oolities and drusy sparite as a cement (oolitic grainstone). Some oolities have quartz grains as nuclei. Hydrochemical analysis shows that the total dissolved salts of extracted solutions of the North Coast quarry samples range from 539 to 686 ppm and dramatically increase (i.e., ten times) for extracted solutions from monument samples, ranging from 5395 to 6880 ppm. The dominant cation is sodium while the dominant anion is chlorine. Acid insoluble residue analysis shows that the carbonate content ranges from 89.2% to 96.4% for fresh samples from quarries and from 9.2% to 94.8% for weathered monument samples. The weight loss of the quarry oolitic limestone samples range from 30.7% to 32.7% and its physical and mechanical properties become worse after being subjected to 15 cycles of a durability simulation soundness test (using a sodium sulphate solution). Our main recommendations are to use suitable grouting for binding the cracks, high durability reconstruction rocks, and suitable cleaning methods to remove salts from the monuments. 相似文献
11.
Salt exposures and weathering residuum on several salt diapirs in different geographic/climatic settings were studied. Anhydrite,
gypsum, hematite, calcite, dolomite, quartz, and clay minerals are the main constituents of the weathering residuum covering
the salt diapirs in various thicknesses. Erosion rates of residuum as well as of rock salt exposures were measured at selected
sites for a period of 5 years by plastic pegs as benchmarks. Recorded data were standardized to a horizontal surface and to
long-term mean precipitation. For the rock salt exposures the following long-term denudation rates were determined of 30–40 mm a−1 for coastal diapirs and up to 120 mm a−1 for mountain salt diapirs. Long-term mean superficial denudation rate measured on weathering residuum of low thickness reached
3.5 mm a−1 on coastal diapirs. The total denudation rate estimated for the thin residuum is close to 4–7 mm a−1 based on apparent correlation with the uplift rate on Hormoz and Namakdan diapirs. Denudation of rock salt exposures is much
faster compared to parts of diapirs covered by weathering residuum. The extent of salt exposures is an important factor in
the morphological evolution of salt diapirs as it can inhibit further expansion of the diapir. Salt exposures produce huge
amounts of dissolved and clastic load, thus affecting the surrounding of the diapir. 相似文献
12.
针对传统的岩体强度参数估算方法考虑风化程度的研究成果较少的不足,引入弹性波速比λ,提出了岩体强度参数的估算方法。以贵州省二叠系两种典型岩体(灰岩和泥岩)为例,讨论了参数λ和正应力σn对岩体强度参数的影响。主要研究成果为:基于弹性波速比与Hoek-Brown强度准则,探讨了不同风化程度岩体抗剪强度参数折减系数的确定方法;研究了正应力与弹性波速比对不同风化程度灰岩与泥岩岩体瞬时抗剪强度参数的影响,结果表明,岩体所处的环境与风化程度是影响岩体剪切强度参数的主要因素;通过多项式拟合,建立了灰岩与泥岩扰动与未扰动情况下不同风化程度强度折减系数的计算公式,从理论上探讨了两种主要岩体不同风化程度对强度参数的影响。 相似文献
13.
发育完整的灰岩风化壳及其矿物学和地球化学特征 总被引：25，自引：5，他引：20
对于碳酸盐岩土覆土壤成因、尽管碳酸盐岩风化残积成土说被多数学者认同,但由于碳酸盐岩中酸不溶物含量极低,在风化成土过程中会伴随着巨大的体积缩小变化,原岩结构和半风化带无法保留,从而缺失了探索上覆土壤物质来源的重要中间环节,使得这种观点缺乏野外宏观证据的支持。最近,我们在贵州、湖南等地发现了数个以泥质灰岩和泥质白云岩为基岩的碳酸盐岩风化壳剖面,尚保留有较好的原岩结构,具有明显的风化壳分带和过渡现象。这些风化壳剖面的发现为深入研究碳酸盐岩风化成土过程提供了良好的研究场所。本文选取了较为典型的吉首泥灰岩风化壳剖面,从矿物学地球化学的角度来探讨碳酸盐岩风化壳的形成过程和发育特征,结果表明该风化壳既遵循非碳酸盐岩（主要是结晶岩类）风化壳的发育特征,也具有自己独特的地球化学演化规律。风化壳总体特点受碳酸盐中的酸不溶物矿物组合及化学成分的影响甚至控制,风化非碳酸盐风壳相似的发育特征。吉首泥灰岩风化壳剖面的发育特征和作者早先提出 的碳酸盐岩风化成土的两阶段模式是一致的,即以碳酸盐矿物大量淋失、酸不溶物逐渐堆积或残积为特征的早期阶段和残积物进一步风化成土的阶段,后一阶段的演化类似非碳酸盐岩类的风化过程。 相似文献
14.
岩性不均一的灰岩风化壳发育特征——贵阳花溪剖面粒度分布特征的指示 总被引：3，自引：2，他引：1
通过贵阳花溪夹泥质薄层的灰岩风化壳剖面的粒度分布特征的研究,结合矿物成分分析,揭示出岩性不均一的灰岩风化壳的发育特征: 灰岩作为剖面主体的成土母岩,风化早期,其以碳酸盐矿物的大量溶蚀及酸不溶物的残余积累为特征,同时方解石的溶解也延缓了酸不溶物的风化; 后期,随着易溶盐类消失殆尽,酸不溶物作为风化主体,开始了类似其它岩类的风化过程。而灰岩中的泥质薄层夹层,作为风化壳的次要组分,在灰岩风化过程中,由于存在巨大的体积缩小变化,泥质薄层被错断并被灰岩的风化产物所包裹,延缓了其风化发育进程。于是,各端元组分由于所处的微环境的差异,受风化溶液的影响程度不同,按照各自的风化方向和演化方式进行。随着风化程度不断增强,泥质薄片的包裹体分解,端元组分逐渐混合、趋同,风化壳趋于均质化,以统一的风化成土作用向表生稳定的矿物转变。 相似文献
15.
可溶盐富集是造成山西大同云冈石窟砂岩表面风化、结构破坏及强度降低的重要地质病害之一。采取云冈石窟造像层砂岩,使用芒硝对该砂岩进行了劣化模拟试验。在可溶盐反复结晶过程中,对样品进行实时变形监测,并对循环过程中质量衰减、强度变化、孔隙分布等进行测试与分析。结果表明,可溶盐的发育是导致石窟表面粉化脱落的重要因素,严重降低了石窟文物本体的价值;可溶盐结晶导致岩石颗粒间胶结作用破坏,增大岩石孔隙率,岩石内部结构劣化严重影响岩石的刚度与强度等力学参数;对比无水芒硝与10水芒硝两种劣化试验,云冈石窟在相对干燥季节下,可溶盐晶体发育对岩石破坏更为显著。为了预测砂岩长期劣化过程,在试验数据基础上,初步建立起孔隙增长的对数模型和强度衰减的指数模型。 相似文献
16.
Analysis of support requirements for a shallow diversion tunnel at Guledar dam site, Turkey 总被引：2，自引：0，他引：2
Engineering geological properties and support design of a planned diversion tunnel at Guledar dam site, which was located at the North of Ankara, Turkey were studied in this article. The main purpose of the construction of the planned tunnel is to regulate, drainage and to provide water for irrigation purposes. The diversion tunnel runs mainly through formations of limestone, sandstone and diabase. Rock masses at the site were characterized using Rock Mass Rating (RMR), Rock Mass Quality (Q), Rock Mass Index (RMi) and Geological Strength Index (GSI). RMR, Q, RMi and GSI were determined by using field data and mechanical properties of intact rock samples, measured in the laboratory. Support requirements for the planned diversion tunnel were determined accordingly in terms of the rock mass classification systems. Recommended support systems by empirical methods were also analyzed using 2D Finite Element method. Calculated parameters based on empirical methods were used as input parameters in the finite element models. The results from both methods were compared with each other. This comparison suggests that more reliable support design could be achieved by using the finite element method together with the empirical methods. 相似文献
17.
Reginaldo Bertolo Christine Bourotte Leonardo Marcolan Sonia Oliveira Ricardo Hirata 《Journal of South American Earth Sciences》2011,31(1):69-80
Anomalous and natural concentrations of Cr6+, occasionally exceeding the permitted limit for human consumption (0.05 mg/L), have been detected in groundwater in the northwestern region of the state of São Paulo. As part of a water-rock interaction investigation, this article describes the chemical and mineralogical characterization of rock samples taken from boreholes in the municipality of Urânia, with the objective of identifying Cr-bearing minerals and determining how chromium is associated with these minerals. Rock sample analysis were performed using X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, electron microprobe and sequential extraction techniques. Chemical analyses indicated that the quartzose sandstones show a geochemical anomaly of chromium, with an average content of 221 ppm, which is higher than the reported chromium content of generic sandstones (35 ppm). Diopside was identified as the primary Cr-bearing mineral potentially subject to weathering processes, with a chromium content of up to 1.2% as Cr2O3. Many of the diopside grains showed dissolution features, confirming the occurrence of weathering. Sequential extraction experiments indicated that 99.3% of the chromium in samples is tightly bonded to minerals, whereas 0.24% is weakly bonded via adsorption. Assuming hypothetically that all adsorbed chromium is released via desorption, the theoretical Cr concentration in water would be one order of magnitude higher than the concentrations of Cr6+ detected in groundwater. 相似文献
18.
Alicia Kirschbaum Estela Martínez Gisela Pettinari Silvana Herrero 《Journal of South American Earth Sciences》2005,19(4):479-493
Two weathering profiles evolved on peneplain-related granites in Sierra Norte, Córdoba province, were examined. Several weathering levels, of no more than 2 m thickness, were studied in these profiles. They had developed from similar parent rock, which had been exposed to hydrothermal processes of varying intensity. Fracturing is the most notable feature produced by weathering; iron oxides and silica subsequently filled these fractures, conferring a breccia-like character to the rock. The clay minerals are predominantly illitic, reflecting the mineral composition of the protolith. Smaller amounts of interstratified I/S RO type are also present, as well as scarce caolinite+chlorite that originated from the weathering of feldspar and biotite, respectively. The geochemical parameters define the weathering as incipient, in contrast to the geomorphological characteristics of Sierra Norte, which point to a long weathering history. This apparent incompatibility could be due to the probable erosion of the more weathered levels of the ancient peneplains, of which only a few relicts remain. Similar processes have been described at different sites in the Sierras Pampeanas. Reconstruction and dating of the paleosurfaces will make it possible to set time boundaries on the weathering processes studied and adjust the paleographic and paleoclimatic interpretations of this great South American region. 相似文献
19.
20.
地表风化产生的表面覆盖层、风吹送的尘埃、胶结物或附着物在岩矿表面形成的外壳是影响地表高光谱遥感识别和反演的重要和关键因素。本研究区位于干旱缺水的新疆西准噶尔包古图地区,对岩矿表面的风化面、胶结物形成的荒漠漆、附着于岩面的地衣和原岩的新鲜面进行了波谱测定分析、X射线荧光元素分析和光薄片镜下观察。结果表明：该地区的大部分岩石表面有风化层覆盖,主要为物理风化,少部分岩石表面发生了化学风化;荒漠漆波谱在可见光波段改变原岩本身的波谱形态,但在短波红外波段,保持原岩波谱特征只改变了反射率大小,并不影响对原岩矿物质的高光谱探测;地衣附着于岩表的波谱特征不仅改变了波谱反射率,还完全改变了原岩的波谱形态,对原岩表面波谱有混淆干扰作用。岩矿表面的研究是波谱测量从实验室走向野外实际应用的基础,也是利用高光谱遥感技术直接进行矿物识别、相似矿物的区分以及提取矿物含量和化学成分研究的最初和关键一步。 相似文献