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1.
The effect of weathering on pore geometry and compressive strength of selected rock types from Turkey 总被引：7，自引：0，他引：7
Atiye Tu
rul 《Engineering Geology》2004,75(3-4):215-227
Weathering processes cause important changes in rock porosity. Besides porosity, distribution of pore sizes is significant for the identification of changes due to rock weathering and its effects on fabric. The formation of secondary porosity in different types of rock taken from different parts of Turkey was examined and the results are presented in this paper. The aim of this study was to observe changes in porosity due to weathering. Effective porosity, mercury intrusion porosimetry, and optical and scanning electron microscopy were used to evaluate the changes in pore geometry of the rocks. Additionally, the dry density, water absorption and uniaxial compressive strength of the rocks at different weathering stages were determined. Analysis of experimental data showed that microstructure of the rocks in relation to weathering is the main feature, which controls their physical and mechanical properties. The study revealed that fabric characteristics, particularly the pore and fracture geometry are very important characteristics for assessment of the behaviour of weathered rock. 相似文献
2.
Salt crystallization is the most significant factor in the degradation of the natural stones used in cultural and historical structures. Stones decay partially or fully as a result of this exposure. This study is the investigation of the degradation of historical monuments (underground cities and semi-underground settlements) carved in pyroclastic rocks in Cappadocian Region which takes part in World Cultural Heritage List. Samples of pyroclastic rocks were collected from six different quarries in Cappadocia, Turkey. To understand the contribution of salt crystallization to this weathering, dry weight loss (DWL) tests were performed on these samples. To investigate the correlations between salt crystallization and other rock properties, porosity, water absorption, ultrasonic velocity, uniaxial compressive strength, Brazilian tensile strength, and point load index were also measured. During the SC process of weathering, the results showed that porosity and water absorption increased for all the samples whereas ultrasonic velocity, uniaxial compressive strength, tensile strength, and point load index values decreased. Evaluation of the data obtained from these tests showed very high logarithmic correlations between the dry weight loss values and the mechanical properties. 相似文献
3.
The influence of petrophysical properties on the salt weathering of porous building rocks 总被引：1，自引：0，他引：1
D. Benavente N. Cueto J. Martínez-Martínez M. A. García del Cura J. C. Cañaveras 《Environmental Geology》2007,52(2):215-224
The influence of pore structure, water transport properties and rock strength on salt weathering is evaluated by means of
a thorough rock characterisation and a statistical analysis. The pore structure was described in terms of its porosity, pore
size distribution (quantified by mean pore radius) and specific surface area, density and water transport was characterised
by means of water permeability (saturated flow) and capillary imbibition (unsaturated flow); whilst the rock strength test
was carried out using uniaxial compressive strength, compressional and shear wave velocities, dynamic elastic constants and
waveform energy and attenuation were obtained from the digital analysis of the transmitted signal. A principal component analysis
and a stepwise multiple regression model was carried out in order to examine the direct relationships between salt weathering
and petrophysical properties. From the principal component analysis, two main components were obtained and assigned a petrophysical
meaning. The first component is mostly linked to mechanical properties, porosity and density whereas the second component
is associated with the water transport and pore structure. Salt weathering, quantified by the percentage of weight loss after
salt crystallisation, was included in both principal components, showing its dependence on their petrophysical properties.
The stepwise multiple regression analysis found that rock strength has a predominant statistical weight in the prediction
of salt weathering, with a minor contribution of water transport and pore structure parameters. 相似文献
4.
The aim of the present article is to identify the influence of the pore morphology on the physical behaviour and durability
of natural stone. Fifteen sedimentary rocks commonly used in the cultural and architectural heritage of Aragon (Spain) were
characterized. The petrography, porous structure, fluid transport properties and durability of these rocks were analysed.
They were classified into two different groups according to the results of the different tests. For each of these groups the
physical behaviour was established. A principal components analysis was used in order to examine the correlation between pore
structure, hydric properties and durability. The results show that the percentage of pore throats <0.1 μm control the fluid
transport properties, have an important influence on stone durability, and can be used to predict resistance to salt decay
while the average pore size does not. Stones with a high percentage of pore throats <0.1 μm are less susceptible to salt decay
than stones with higher pore size if their pore network is characterized by high tortuosity and low connectivity. 相似文献
5.
D. Benavente J. Martinez-Martinez N. Cueto S. Ordoñez M. A. Garcia-del-Cura 《Environmental Earth Sciences》2018,77(4):147
This study aims to understand the effect of salt and frost crystallisation on the petrophysical and durability properties of representative types of travertine and carbonate tufas. Results demonstrate that the studied travertines and tufas exhibit a very high durability against salt and ice crystallisation cycles, compared to carbonates rocks with similar porosity values. The variation of the loss of mass, effective porosity, capillary absorption coefficient, ultrasonic wave velocity and attenuation, and compressive strength was scarce during weathering tests. The evolution of petrophysical properties was slightly more intense after 30 cycles of salt crystallisation than 100 cycles of freeze–thaw. Petrophysical and durability properties of the travertines and carbonate tufas depend on porosity fraction and on the manner in which the vuggy porosity is connected. In the travertine facies, vuggy macropores show little connection and can be considered as separate-vug porosity. Their addition to interparticle porosity increases effective porosity and reduces their mechanical strength but does not significantly increase capillary transport and the effectiveness of salt and ice action over the stone. On the contrary, in the carbonate tufas, vugs act as touching-vug pores, as capillary imbibition coefficients reveal. However, scanning electron microscopy displays that they underwent microcracking processes related mainly to both thermal stresses and/or ice and salt pressures. These microcracks present little connection, and they do not enhance noticeably the water flow or decrease the mechanical properties. These results are finally discussed in terms of a nonlinear decay pattern, which with long periods of apparent stability might be followed by rapid and catastrophic decay. 相似文献
6.
In the present work, the relationship between intrinsic factors, mechanical properties and durability of Miocene sandstones used in the architectural heritage of Tunisia, specifically in the Roman aqueduct of Oued Miliane and Uthina site, are studied. The petrographic study and the characterisation of porous network have been carried out using optical microscopy, mercury intrusion porosimetry and laser scanner confocal microscopy (LSCM). The hygric behaviour has also been determined from water absorption under vacuum, drying, capillary water absorption and water vapour permeability. The mechanical properties have been assessed from compressive strength and abrasion tests. Rock durability has been evaluated from salt crystallization (sodium sulphate) accelerated aging tests. The results show good hygric behaviour characterised by a high evaporation rate and almost no retention of water; due to the macroporous character of the rock and the good connectivity of the pore network. Because of the poor lithification, the stone has a very low mechanical strength which makes it very vulnerable to the salt crystallization effects. The absence of chemically unstable minerals preserves the rock from chemical alteration. The durability of the building stone is mainly conditioned by salt loading of the monument. 相似文献
7.
Geologic features considered to influence durability of the limestone at the sphinx are depositional history, evolution of porosity, and development of joints. These strata have two orthogonal groups of vertical joints. Where these joints intersect, wedge-shaped blocks are separating, causing loss of material from the core. Major reduction of the sphinx, however, is occurring due to salt crystallization aided by the ink-bottle pore systems prevailing in these rocks.The weathering profile exhibits alternating layers, less and more highly weathered. The less weathered rock is a biomicritic grainstone with smaller quantities of halite and gypsum and a larger large-pore-to-throat ratio than the indented, predominantly micritic, layers with larger concentration of salts and a smaller large-pore-to-throat ratio. Based upon poresize distributions, pressures generated in the pores have been calculated using thermodynamic principles, and an equation has been derived that provides a quantitative measure of durability of these rocks. 相似文献
8.
The paper principally focuses on the durability assessment of various stratigraphic levels of Ahlat ignimbrites collected from the eastern region of Turkey. A total of four different ignimbrite types with dissimilar color, texture and particularly welding degree were tested in laboratory. The laboratory tests performed on the ignimbrite specimens indicate that the welding degree as well as the lithic material content mainly controls the strength and capillarity properties of the ignimbrites. In addition, the durability of highly porous ignimbrites strongly depends upon the degree of welding. The effect of several weathering agents on the ignimbrites was evaluated on the basis of decay constant parameter. Accordingly, salt and ice crystallization pressures are a couple of major destructive agents acting within the micropores of the ignimbrites. Conversely, the investigated specimens are relatively durable against cyclic wetting–drying. Statistical evaluations reveal that the pore diameter is the major controlling factor on the deterioration rate of the ignimbrites after specifically recurrent freeze–thaw cycles. Moreover, the dry unit weight of the ignimbrites is more significant than the uniaxial compressive strength considering the deterioration rates during wetting–drying and salt crystallization. A less significant relationship was obtained between pore diameter and salt crystallization decay constant. 相似文献
9.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(7):633-637
The study of the pore structure of rocks is very important for the interpretation of their behaviour when subjected to weathering. In the case of rocks used in historic buildings or in objects of art where other techniques can not be applied, the Non-Destructive Testing method (NDT) for determining porosity, such as X-ray computed tomography (X-ray CT), becomes a very interesting alternative. In this paper this technique has been used for imaging textural features and the internal pore structure of a dolomitic rock used as building material in Oviedo Cathedral, Spain. The reconstructed 3D image shows a non uniform distribution of porosity. The rock has been subjected to freeze-thaw cycles to evaluate its durability. The evolution of the void structure has also been studied by X-ray CT and the images obtained allow one to follow the progressive decay and to assess the internal depth of the damage. Because of the low resistance to weathering of the rock, damage, mainly in the form of fissures, was observed even in the initial tests (third cycle in some of the specimens). Breakdown of the rock appeared as early as cycle 12 in some specimens. 相似文献
10.
Two of the most popular weathering tests used for dimension stone are EN 12371 freeze–thaw (FT) and EN 12370 Salt Crystallization (SC). These tests are used to assign a durability value to the rocks. Both tests are based on the cyclical growth of crystals in the porous system of the rock, which causes structural stress on the rock matrix that may affect its integrity. The weathering mechanism is the same in both tests although the rate of volume increase is higher for the salt crystals. Due to this similarity, the two tests provide complementary information. The EN (European Norms) recommend evaluating the results together, but do not establish correlations between the results of these two tests for different types of rocks. Knowing these relationships would improve the understanding of the results and the response to weathering of the rock once placed in a building. In this work, several ornamental rocks (sandstones, limestones, dolostones, and a travertine) from the Iberian Peninsula were submitted to FT and SC tests. Rocks were mineralogically and petrographically characterized, and their porous systems were defined by a combination of techniques (scanning electronic microscopy, digital images analysis, and mercury porosimetry). The results of the tests were quantified numerically to compare them. The velocity of propagation of ultrasonic waves was measured before and after the tests. After the statistical analysis, significant correlations were found between the FT and SC tests, and between the connected porosity and the durability index of the rocks. 相似文献
11.
针对鄂尔多斯盆地大牛地气田马五段低孔低渗岩溶白云岩储层发育特征,展开对致密岩溶白云岩储层孔隙成因进行研究。通过岩心、薄片观察,结合扫描电镜、CT扫描分析,明确了白云岩储层岩石学类型、孔隙类型及成因。结合测井及地球化学分析,认为表生期孔隙主要为膏溶孔、溶孔及地开石晶间孔隙;白云石含量及结构控制了白云岩晶间孔隙;残留有机质保护了藻云岩残余晶间孔隙。通过岩溶白云岩孔隙成因分析,最后认为:(1)白云石化作用及成因模式是造成岩溶白云岩储层低孔低渗的主要原因,准同生期-浅埋藏期形成的白云石晶粒普遍较为细小,晶粒结构以半自形-它形为主,晶间孔隙为微孔,造成孔隙喉道较窄;泥微晶白云岩与粉-细晶白云岩(储集岩)分布在纵向上具有不均匀性,造成白云岩整体上孔渗较低;(2)岩溶作用增加了白云岩储层的非均质性,裂缝、溶洞及较大扩溶孔被泥质、方解石充填,很大程度上降低了岩溶白云岩储层的孔渗性能,正因为膏质泥微晶白云岩和粉-细晶白云岩为低孔低渗特征,使得地表水携带的泥质不易充填孔隙。 相似文献
12.
Most studies dealing with material properties of sandstones are based on a small data set. The present study utilizes petrographical and petrophysical data from 22 selected sandstones and ~300 sandstones from the literature to estimate/predict the material and weathering behaviour of characteristic sandstones. Composition and fabric properties were determined from detailed thin section analyses. Statistical methods applied consist of data distributions with whisker plots and linear regression with confidence regions for the petrophysical and weathering properties. To identify similarities between individual sandstones and to define groups of specific sandstone types, principal component and cluster analyses were applied. The results confirm an interaction between the composition, depositional environment, stratigraphic association and diagenesis, which leads to a particular material behaviour of sandstones. Three different types of pore radii distributions are observed, whereby each is derived from different pore space modifications during diagenesis and is associated with specific sandstone types: (1) bimodal with a maximum in capillary and micropores, (2) unimodal unequal with a maximum in smaller capillary pores and (3) unimodal equable with a maximum in larger capillary pores. Each distribution shows specific dependencies to water absorption, salt loading and hygric dilatation. The strength–porosity relationship shows dependence on the content of unstable lithic fragments, grain contact and type of pore radii distribution, cementation and degree of alteration. Sandstones showing a maximum of capillary pores and micropores (bimodal) exhibit a distinct hygric dilatation and low salt resistance. These sandstones are highly immature sublitharenites–litharenites, characterized by altered unstable rock fragments, which show pointed-elongated grain contacts, and some pseudomatrix. Quartz arenites and sublitharenites–litharenites which are strongly compacted and cemented, show unimodal unequal pore radii distributions, low porosity, high strength and a high salt resistance. The presence of swellable clay minerals in sublitharenites–litharenites leads to a medium to high hygric dilatation, whereas quartz arenites show little hygric dilatation. Sandstones with unimodal equal pore radii distribution mostly belong to weakly compacted and cemented mature quartz arenites. These are characterized by high water absorption and high porosity, low to medium strength and a low salt resistance. The data compiled in this study are used to create a sandstone quality catalogue. Since material properties are dependent on many different parameters of influence, the transition between different lithotypes is fluent. 相似文献
13.
伊拉克艾哈代布油田中-下白垩统碳酸盐岩储层孔隙结构类型划分及其差异性的受控因素和成因的认识是制约该类储层分类评价的一个关键问题。本文综合运用了常规薄片、铸体薄片、扫描电镜、电子探针、常规物性、压汞分析、阴极发光、稳定同位素分析等手段及统计分析方法对储层的主要孔隙类型、喉道类型、喉道分布类型进行了研究,并在此基础上确定了高孔中渗细喉型、中高孔低渗细喉型、中高孔特低渗微喉型、低孔特低渗极微喉型四种孔隙结构类型及其划分依据和方案,同时指出了在该类储层中好的孔隙结构具有网络状、偏细型、分选较差的孔喉特征。通过分析明确了孔隙结构差异性的主要控制因素为岩石组构和溶蚀作用,认为该套储层的孔喉空间及结构是以沉积形成的原生孔隙受同生期或准同生期的溶蚀改造为基础,并在后期表生岩溶作用下的改造而成;而先期受岩石组构控制下的溶蚀作用控制了储层孔隙结构的差异性。通过本文研究将对中东地区该类储层的形成及分类评价研究具有较好的指导意义。 相似文献
14.
大庆兴城南部火山岩储层发育控制因素 总被引：5，自引：1，他引：4
大庆兴城气田主力储层为营城组火山岩。地球化学和岩石学研究表明,该区营城组以中酸性火山岩为主。利用岩心、薄片分析资料,对兴城南部火山岩储层进行了研究。熔岩中储集空间以气孔和脱玻化孔为主,火山碎屑岩中则主要以粒内、粒间孔和溶孔为主。火山岩储层物性差异显著,储层发育状况受火山岩岩性和火山岩相、成岩作用及构造作用影响。火山岩岩石类型与火山岩相决定了储层原生孔隙的发育状况;成岩作用对原生孔隙进行了改造;构造作用产生构造裂缝,对储层起到有效的疏导作用。综合分析认为,近火山口相带火山岩储层物性好,是天然气勘探开发的有利区域。 相似文献
15.
Ahmad Zalooli David Martín Freire-Lista Mashalah Khamehchiyan Mohammad Reza Nikudel Rafael Fort Shahram Ghasemi 《Environmental Earth Sciences》2018,77(8):315
Durability of building stones is an important issue in sustainable development. Crystallization of soluble salts is recognized as one of the most destructive weathering agents of building stones. For this reason, durability of Ghaleh-khargushi rhyodacite and Gorid andesite from Iran was investigated against sodium sulfate crystallization aging test. Petrographic and physico-mechanical properties and pore size distribution of these stones were examined before and after the aging test. The characteristics of the microcracks were quantified with fluorescence-impregnated thin sections. Durability and physico-mechanical characteristics of Ghaleh-khargushi rhyodacite are mainly influenced by preferentially oriented preexisting microcracks. Stress induced by salt crystallization led to the widening of preexisting microcracks in Ghaleh-khargushi rhyodacite, as confirmed by the pore size distributions before and after the aging test. The preexisting microcracks of Gorid andesite were attributed to the mechanical stress induced by contraction of lava during cooling. The number of transcrystalline microcracks was significantly increased after the aging test. The degree of plagioclase microcracking was proportional to its size. Durability of the studied stones depends on initial physico-mechanical properties, pore size distribution, and orientation of microcracks. Initial effective porosity is found to be a good indicator of the stones’ durability. Salt crystallization resulted in an increase in the effective porosity with a parallel decrease in the wave velocities. Surface microroughness parameters increased with the development of salt crystallization-induced microcracking. Gorid andesite showed higher quality and durability than Ghaleh-khargushi rhyodacite. 相似文献
16.
页岩基质孔隙主要包含有机孔隙和无机孔隙,页岩油气在有机孔隙和无机孔隙中的渗流机理不同,对页岩中有机孔隙和无机孔隙的微观结构进行定量表征具有重要意义.首先通过扫描电子显微镜(scanning electron microscope,简称SEM)实验分别获取具有代表性的页岩无机孔隙和有机孔隙扫描电镜图像,其中,无机孔隙相对较大,其图像的分辨率较低,有机孔隙相对较小,其图像的分辨率较高;然后,通过图像处理和马尔可夫链蒙特卡洛(Markov chain Monte Carlo,简称MCMC)法重构出相应的无机孔隙数字岩心和有机孔隙数字岩心,并提出局部叠加法构建同时包含无机孔隙和有机孔隙的页岩基质孔隙数字岩心;最后对无机孔隙数字岩心、有机孔隙数字岩心和基质孔隙数字岩心的结构特征进行了对比分析.结果表明,局部叠加法构建的页岩基质孔隙数字岩心能够同时描述页岩中的无机孔隙和有机孔隙结构特征,无机孔隙本身连通性较差,有机孔隙本身连通性较好,有机孔隙的局部孔隙度和局部渗透率较高,对页岩中的流体渗流有着重要作用.该方法为页岩中不同的孔隙结构特征描述和油气在纳米尺度孔隙中的传输模拟提供了一个可靠的研究平台. 相似文献
17.
滨里海盆地东缘北特鲁瓦地区白云岩特征及其储层发育机制 总被引：1，自引：1，他引：0
白云岩是滨里海盆地盐下石炭系碳酸盐岩的重要储层类型。在岩芯、薄片、物性与地球化学等资料分析的基础上,对研究区KT-Ⅰ油组的白云岩类型与储集性能进行了分析,并探讨了其储层发育的控制因素与模式。结果表明,白云岩类型与其储集物性具有较明显的相关性,以生屑铸模孔及溶蚀扩大孔为主的残余生屑白云岩物性与含油气性最好,以晶间（溶）孔为主的粉细晶白云岩和以生屑铸模孔及晶间孔为主的泥粉晶白云岩次之,而以晶间微孔为主的泥晶白云岩最差,难以成为有效储层。原生孔隙发育的相对高能生屑滩环境是该区优质白云岩储层发育的相带基础。晚石炭世准同生期大气淡水溶蚀作用与以渗透回流白云化（白云石有序度分布于0.32～0.67,δ13C介于-0.22‰～5.94‰,δ18O介于-1.09‰～2.45‰）为主的早期白云化作用为白云岩储层早期孔隙的发育与保存奠定了坚实的基础;早二叠世以来埋藏期各类裂缝的发育及酸性流体的溶蚀作用则对储层的晚期扩孔改造至关重要。 相似文献
18.
以沾化凹陷渤南洼陷罗63井和义21井沙一段取心段为例,依据研究样品的热解、全岩与黏土矿物X射线衍射、有机岩石学、孔隙度、氩离子抛光+扫描电镜以及微孔隙结构等分析结果,开展了沙一段湖相富有机质烃源岩岩石学与孔隙结构特征研究,结果表明：罗63井和义21井沙一段取心段富有机质烃源岩主要由碳酸盐矿物、黏土矿物和石英组成,另含少量长石、黄铁矿和石膏,其中黏土矿物主要由伊/蒙混层、伊利石组成,由取心段顶部至底部,碳酸盐矿物质量分数明显增高,而黏土矿物和石英则显著降低,呈现由钙质或灰质泥岩至演变为泥质灰岩的特征,岩石构造类型包括层状、纹层状和块状3类;罗63井和义21井沙一段取心段富有机质烃源岩平均孔隙度分别为2.09%和4.43%,具纹层状构造的烃源岩具有相对高的孔隙度;主要发育矿物基质孔隙（即粒间孔隙和粒内孔隙）和裂缝型孔隙两大类,而有机质孔隙不发育,孔隙半径从十几微米至几纳米的孔隙均有分布,以发育孔径50 nm以上的宏孔为主。 相似文献
19.
塔河油田奥陶系储层研究 总被引：13，自引：0，他引：13
通过钻井岩心和铸体薄片观察，根据下奥陶统灰岩基质的孔渗特征和孔隙结构特征，并与基质作为储层的下限对照裂隙、洞穴和溶蚀孔洞不发育的灰岩基质，发现尽管有微孔隙的发育，但其孔隙度、渗透率、最大孔喉半径、饱和度、中值喉道半径等参数值远低于储层下限值，基本不具备储集和生产油的意义。而下奥陶统灰岩段储集和生产油气的有效储渗空间按成因、形态及大小可划分为溶蚀孔隙、溶蚀孔洞、大型洞穴、风化裂隙、构造裂隙等5类，构成5种性质有别的储层，即洞穴型储层、风化裂隙型储层、构造裂隙型储层、台缘滩相颗粒灰岩溶蚀孔隙型储层和地表残积物裂隙-孔隙（洞）型储层。从而使塔河油田奥陶系储层有了一个比较系统、完善的划分标准。研究和搞清这些有效储层的成因及分布规律，对塔河田区奥陶系的油气勘探开发至关重要。 相似文献
20.
息烽磷矿是贵州地区震旦纪陡山沱期磷矿的重要组成部分,以矿层厚、品位高、断裂构造发育、叠层石丰富而独具特色。通过对矿床地质特征及矿床地球化学特征综合研究认为,从陡山沱组底到顶气候经历温湿—干热—湿热变化,海平面对应经历了海进—海退—海进,其内的磷块岩和磷质岩是在热水沉积作用、生物作用和正常海水沉积作用等共同作用下形成于前滨—临滨环境。综合以上,反演息烽陡山沱期成矿过程,发现矿床经历了“海进—海退—海进”三阶段成矿,在陡山沱早期海进阶段形成下矿层,随后的海退阶段和海进阶段形成上矿层。空间上,2矿层之间夹白云岩,且交于靠黔中古陆一侧,当第2次海进越过第1次海进的前滨—临滨位置后,只形成上矿层,是开阳、息烽磷矿床1层矿体形成的对应部位。瓮福磷矿床有2层矿体,对应处于经历了“三阶段成矿”的前滨—临滨部位,且瓮福磷矿成矿时的位置高程明显低于息烽磷矿、息烽磷矿略低于开阳磷矿,通过岩性特征对比,与实际基本吻合。因此,在对陡山沱期的磷矿进行成矿预测和找矿勘查中,与息烽磷矿床相似的黔中及附近区域的动态前滨—临滨环境,均为磷矿床的找矿靶区,利用“三阶段成矿”形成相交的2矿层特点,可高效对已知矿床、矿化点和前滨—临滨带周围进行成矿预测。 相似文献