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1.
Interest in the preservation of rapidly decaying monuments, especially in urban areas, has increased appreciably over the last three decades. A stone preservative can be defined as a chemical treatment, which, when applied to stone, combats the harmful effects of time and environment, thereby prolonging the life of a stone by either restoring its physical integrity or by inhibiting its decay. Any preservative applied to stone must not change the natural appearance or architectural value of the stone to any appreciable extent. There are two principal means by which stone can be preserved. One involves the formation of an outer stabilized zone around the stone; the other alters the chemical composition of the stone.A number of examples of stone preservation carried out on ancient monuments in the United Kingdom are taken to illustrate stone preservation methods. Their relative success is evaluated, and some more recent developments in stone preservation referred to. 相似文献
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为了研究包裹碎石桩的承载机制,开展了室内模型试验,对不同套筒长度和刚度的包裹碎石桩承载力、端阻力、变形和破坏情况等进行了分析。试验中利用自制的桩体径向变形测量仪监测了桩体的径向变形情况。试验结果表明：当桩体支承在坚硬土层时,全长包裹碎石桩有效提高碎石桩的承载力和刚度,且采用弹性模量较大的土工材料套筒,包裹碎石桩的极限承载力和刚度也较大,部分包裹碎石桩（包裹长度为0.6倍桩长）相对于碎石桩优势不明显。这是因为部分包裹碎石桩和全长包裹的承载特性、变形特点和破坏模式均存在差异。全长包裹碎石桩传递至桩底端的荷载大于部分包裹碎石桩和碎石桩的。与部分包裹碎石桩和碎石桩比较,全长包裹碎石桩桩身变形分布较为均匀,同一应力作用下,桩身最大径向变形量较小。此外,全长包裹碎石桩刺入顶部褥垫层发生破坏,而部分包裹碎石桩发生鼓胀破坏。 相似文献
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With ports and other near shore structures expanding, and regions previously not considered prone to earthquakes being re-classified
after recent earthquake events, ground improvement by stone columns is increasingly considered to improve loose or soft in situ soils. The Dry Bottom Feed Stone Column construction technique can be used under water if a double-lock stone delivery system
is attached to the vibroprobe. The use of pneumatic stone transport from the barge into the vibroprobe receiver tank makes
it possible to reach large water and treatment depths. Digital recording of all relevant operation parameters provides a very
high level of quality assurance, including a diameter-over-depth profile for each stone column. An introduction to earthquake-resistant
design of stone columns and guidelines for specifying Marine Stone Columns are given. 相似文献
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N. Mehrannia J. Nazariafshar F. Kalantary 《Geotechnical and Geological Engineering》2018,36(1):209-222
Using stone columns is an efficient method to increase the bearing capacity of soft soils. This has led to an increased interest in further developing and improving the method. In addition, granular blankets are used to increase the bearing capacity of the stone columns. In this research, the bearing capacity of stone columns, granular blankets, and a combination of both methods in reinforced and unreinforced modes was examined using large-scale laboratory tests. A scale factor of 1–10 is used for the geometry of the models, and the stone columns are a floating type that are 60 mm in diameter and 350 mm in length. These columns are either reinforced with vertical encasement of a geotextile or they are unreinforced. The granular blankets are either reinforced by using a biaxial geogrid or they are unreinforced with 40 and 75 mm thicknesses. In general, 16 large experimental tests have been carried out. Results indicate that using all these variations (granular blankets, stone columns, and a combination of both) improves bearing capacity. Using geogrid as the reinforcement of granular blankets and geotextile as stone-column encasement increases the efficiency of granular blankets and stone columns significantly. The maximum bearing capacity was obtained when reinforced granular blankets and reinforced stone columns were combined. The stress-concentration ratio and bearing capacity increased as geotextile encasement was used in the stone columns. 相似文献
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Geotechnical Engineering has developed many methods for soil improvement so far. One of these methods is the stone column method. The structure of a stone column generally refers to partial change of suitable subsurface ground through a vertical column, poor stone layers which are completely pressed. In general terms, to improve bearing capacity of problematic soft and loose soil is implemented for the resolution of many problems such as consolidation and grounding problems, to ensure filling and splitting slope stability and liquefaction that results from a dynamic load such as earthquake. In this study, stone columns method is preferred as an improvement method, and especially load transfer mechanisms and bearing capacity of floating stone column are focused. The soil model, 32 m in width and 8 m in depth, used in this study is made through Plaxis 2D finite element program. The clay having 5° internal friction angle with different cohesion coefficients (c 10, c 15, c 20 kN/m2) are used in models. In addition, stone columns used for soil improvement are modeled at different internal friction angles (? 35°, ? 40°, ? 45°) and in different s/D ranges (s/D 2, s/D 3), stone column depths (B, 2B, 3B) and diameters (D 600 mm, D 800 mm, D 1000 mm). In the study, maximum acceleration (a max = 1.785 m/s2) was used in order to determine the seismic coefficient used. In these soil models, as maximum acceleration, maximum east–west directional acceleration value of Van Muradiye earthquake that took place in October 23, 2011 was used. As a result, it was determined that the stone column increased the bearing capacity of the soil. In addition, it is observed that the bearing capacity of soft clay soil which has been improved through stone column with both static and earthquake load effect increases as a result of increase in the diameter and depth of the stone column and decreases as a result of the increase in the ranges of stone column. In the conducted study, the bearing capacity of the soil models, which were improved with stone column without earthquake force effect, was calculated as 1.01–3.5 times more on the average, compared to the bearing capacity of the soil models without stone column. On the other hand, the bearing capacity of the soil models with stone columns, which are under the effect of earthquake force, was calculated as 1.02–3.7 times more compared to the bearing capacity of the soil models without stone column. 相似文献
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石器生产是一个动态的生产系统,而石料是石器生产和研究的前提。通过对大辛庄遗址周围考古与地质调查和对出土商代石器标本的细致分析表明,该遗址商代石器原料使用种类丰富,石料的利用率与遗址周围石质类型分布有着极为密切的关系。原料分布广泛,具有高含量、低质量的特点,明显影响着当地石器工业的面貌和开发与利用自然的策略。大辛庄石料应当来源于当地,主要有两种途径:一种是就地取材;另一种主要来源于南部山区和鲍山一带,主要通过水路运输,陆路运输条件具备。在利用与开发石料的战略上,大辛庄人充分认识到石料特性,尤其对沉积岩的认识与利用,重视选材,考虑石器功能和使用方式,并很好地实施到石器制作过程中,制定相应的应对策略。通过对大辛庄商代石料来源地和开发策略的考察,有利于认识当时人地关系和大辛庄人认识自然、开发自然的认知水平。 相似文献
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贵州思南石林目前正建设成为思南乌江喀斯特国家地质公园长坝石林景区。本文通过石林的形态特征对比研究及区域地质环境的调查,分析了石林的景观资源特征,并探讨了石林的形成条件和发育演化过程,结果表明:（1）思南石林属溶洼边坡型石林,石林形态多样、个体高大且象形景观众多,加之石林生态环境良好,风光秀美,具有较高的观赏、科研和科普及开发价值。（2）思南石林以质纯层厚的下二叠统深色泥晶灰岩为主,并处于南东-北西构造应力带上,利于较高大石林的形成和保存;地貌上,石林发育在喀斯特单面山与溶蚀洼地之间的斜坡上,不同地貌部位的水动力条件导致石林形态和分布的差异;气候上,思南地区自新第三纪以来以热带、亚热带温湿气候为主,为石林的形成提供了充足的外营力条件;此外,来自碎屑岩区的外源水侵蚀和下伏碎屑岩的隔水顶托作用为大面积石林的形成提供了很好的水环境条件。（3）石林形成过程可归纳为海侵沉积、抬升剥蚀、构造变形、土下溶蚀和地表塑造5个阶段;其中地表塑造阶段是石林的成景时期,依据有关侵蚀数据计算得出石林成景时代约为30.04~45.06 ka,即晚更新世中晚期。 相似文献
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Stone columns in soft soil improve bearing capacity because they are stiffer than the material which they replace, and compacted stone columns produce shearing resistances which provide vertical support for overlying structures or embankments. Also stone columns accelerate the consolidation in the native surrounding soil and improve the load settlement characteristics of foundation. In this paper, the finite element method is utilized as a tool for carrying out analyses of stone column–soil systems under different conditions. A trial is made to improve the behaviour of stone column by encasing the stone column with geogrid as reinforcement material. The program CRISP-2D is used in the analysis of problems. The program allows prediction to be made of soil deformations considering Mohr-Coulomb failure criterion for elastic–plastic soil behaviour. A parametric study is carried out to investigate the behaviour of standard and encased floating stone columns in different conditions. Different parameters were studied to show their effect on the bearing improvement and settlement reduction of the stone column. These include the length to diameter ratio (L/d), shear strength of the surrounding soil and, the area replacement ratio (as) and others. It was found that the maximum effective length to diameter (L/d) ratio is between (7–8) for Cu, between (20–40) kPa and between (10–11) for Cu?=?10?kPa for ordinary floating stone columns while the effective (L/d) ratio is between (7–8) for encased floating stone columns. The increase in the area replacement ratio increases the bearing improvement ratio for encased floating stone columns especially when the area replacement ratio is greater than (0.25). The geogrid encasement of stone column greatly decreases the lateral displacement compared with ordinary stone column. 相似文献
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V. Six H. Mroueh I. Shahrour M. Bouassida 《Geotechnical and Geological Engineering》2012,30(4):813-825
This paper deals with the influence of the earth pressure at rest coefficient K 0 on stone columns behavior. This parameter is related to the initial stresses caused by the compression of in situ soil and by the installation (expansion of column material). Numerical calculations based on finite element method are compared to analytical methods and conventional engineering methods addressed to the design of stone columns. The presented results led to a better comprehension of previous methods for the design of stone column and highlighted the importance of well defining the initial stress level due to stone columns installation. 相似文献
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以老挝石和寿山石的岩相学为基础,对其矿物学上的差异性进行了对比分析研究.重点用电子探针（EMPA）分析了老挝石和寿山石组成的化学元素种类及含量.用X射线粉晶衍射（XRD）分析了老挝石和寿山石的矿物组成.研究结果表明,老挝石和寿山石两者在矿物学上的差异主要体现在颜色、成分等方面,老挝石的颜色主要为红、白、粉,较少出现黄色,寿山石颜色丰富多彩,有红、白、粉、紫、黄、绿等,不同品种颜色差异较大.造成老挝石和寿山石颜色差异的主要原因为Fe元素含量的变化,Fe含量越高,颜色越深.老挝石和寿山石的主要矿物组成大致相同,主要由地开石、高岭石和珍珠陶石等组成,但两者在矿物组成含量及种类上略有差异.寿山石品种不同,矿物组成略有差异,如寿山虎口石中出现黄铁矿和叶蜡石,这在老挝石的研究中没有发现. 相似文献
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Irfan Celal Engin 《Arabian Journal of Geosciences》2013,6(12):5043-5054
The process of giving an antique look, a worn and “old” appearance, to natural stone surfaces, which can be observed by abrasion in natural ways through a long time, is called artificial aging. Natural stone processing facilities that involve mass production usually prefer vibration aging machines. This study examines the utilization of various rock aggregates and abrasive residuals instead of synthetic abrasives used in aging machines. Natural stone samples with different properties were aged in a vibration aging machine using andesite, granite, sandstone, pebble stone, abrasive stone residuals, and ceramic abrasives. At the end of the study, the aging performance of different rocks was determined; granite was found to be the most effective. Rock aggregates were ranked in terms of their abrasiveness (aging) performance, from the most effective to the least effective as: granite, ceramic abrasive, sandstone, andesite, pebble stone, and abrasive stone residuals. It was observed that rock aggregates can be used in the aging process instead of synthetic ceramic abrasives, with desired performance. 相似文献
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V. Cnudde P. Dubruel K. De Winne I. De Witte B. Masschaele P. Jacobs E. Schacht 《Engineering Geology》2009,103(3-4):84-92
To reduce the weathering rate of natural building stones, a wide variety of water repellents and consolidants are commercially available. Although a lot of research is performed on these products, it remains difficult to determine which product is appropriate to use for a certain type of building stone. Each type of building stone has its own petrographic characteristics (mineralogy, texture, …), leading to typical physical and technical properties which influence its rate of decay. The localisation of the products inside a stone type is not only depending on the properties of the products themselves, but also linked to the texture and structure of the stone. The impregnation depth of the products strongly influences their efficiency and is therefore a key issue in the determination if a product is functional for a certain type of stone. X-ray micro-CT has recently been introduced as a non-destructive material evaluation technique for engineering and geology purposes. The fact that micro-CT can provide information about the internal structure and properties of natural building stones, is a major advantage in the study of their conservation. Firmly linked with more classical research techniques, this non-destructive technique offers an extra dimension to the cultural heritage research.In this paper, non-destructive X-ray computed micro-tomography (micro-CT) turns out to be a powerful tool as it can visualise the presence of water repellents and consolidants inside the stone and can help to detect the influence that these treatments exert on porosity and pore-size distribution. For the visualization of the product its atomic number and density and the amount of product inside the natural building stone is crucial. Besides the contrast in attenuation, the resolution of the micro-CT also needs to be taken into account to obtain a good contrast between stone and product. By doping with 3-bromopropyltrimethoxysilane, more contrast occurs between the stone material and the conservation product. When the amount of product inside the samples is very low and the product is homogeneously spread inside the sample, the doped product is difficult to distinguish from the stone material due to the resolution of the micro-CT. When the amount of doped product inside the stone material reaches a certain threshold value, the dope will appear in the 2D cross-sections derived from micro-CT, creating a good visualization of the products inside the stone samples. 相似文献
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The Angera stone: a challenging conservation issue in the polluted environment of Milan (Italy) 总被引：1，自引：1，他引：0
D. Gulotta M. Bertoldi S. Bortolotto P. Fermo A. Piazzalunga L. Toniolo 《Environmental Earth Sciences》2013,69(4):1085-1094
The Angera stone is a sedimentary Triassic dolostone mainly composed of dolomite, which was widely employed in the Lombard architecture. In the present work, the study of the Angera stone of the ‘Cortile del Richini’, a masterpiece of the Lombard baroque, is discussed as an example of a particularly challenging conservation issue. The courtyard suffered from a particularly troubled conservative history and the highly polluted urban environment of Milan provided very favourable conditions for the decay of such a delicate stone type. The last extensive conservative intervention was performed during the nineties due to massive black crust formation and granular disintegration of the stone. Almost 20 years later, a thorough study of the stone has been aimed at the definition of a long-term maintenance project. The Angera stone has been investigated in order to define an updated version of its state of conservation, as well as to track any changes in the degradation mechanisms due to the environmental variations of the Milan city centre. In particular, the soluble salts’ content of the stone substrate has been evaluated as an indicator of the damage level. The results highlighted that the stone is currently in critical condition: An extensive sulphation process is taking place, leading to the chemical transformation of the dolomitic substrate into gypsum. Moreover, the powder deposits affecting the stone surfaces have a similar composition to those generally found in the black crusts growing in urban environment. Therefore, they can be considered as precursor of this particularly dangerous decay mechanism. 相似文献
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OLAV B. LIAN STEPHEN R. HICOCK ALEKSIS DREIMANIS 《Boreas: An International Journal of Quaternary Research》2003,32(1):102-113
With the aid of three case studies we summarize sedimentological and structural evidence in Wisconsinan subglacial till and its substrate that can be used to infer the presence of former fast-moving ice. We compare sedimentological characteristics of till with its stone fabric, stone surface erosional features and orientations of fractures, faults and folds in till and substrate, in order to interpret the processes that formed the till. In the cases we studied, stones in tills that experienced ductile deformation (inferred to be associated with fast-moving ice) show variable alignment of latest surface striae. Moreover, striae are inconsistent with the orientations of lee ends and chattermarks on the same stones, and with the dip directions of shallow shear planes and (or) steeper tension fractures in the till matrix. These observations indicate that stones were rotating in a flowing till matrix prior to their final emplacement. Ductile shear of fine-textured, water-saturated till and Jeffrey-like rotation of stones are invoked where most of the following occur together: (i) delicate striae follow the curvature of stone surfaces; (ii) a-axis fabrics are multimodal to girdle-like; (iii) stone a axis eigenvectors, striae orientation and stone lee end alignments fall between the modes of stone fabrics; (iv) stone pavements are uneven with vertically oriented and inverted bullet-shaped stones; (v) soft sediment clasts and (or) fragile fossils are preserved. 相似文献
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喀斯特石漠化小生境对大型土壤动物群落结构的影响 总被引：2，自引：0，他引：2
对花江流域喀斯特地区小生境(土面、石槽、石沟)的土壤动物进行了研究。结果表明:喀斯特石漠化地区小生境共捕获大型土壤动物平均为276.7只,分别隶属3门7纲24类。其中,优势类群蚂蚁占总数的56.75%。 土面生境土壤动物的多样性指数为1.199,石沟的为1.592,石槽的为1.962; 均匀性指数为0.616,石沟的为0.989,石槽的为1.095; 土面生境土壤动物的优势度为0.545,石沟的为0.353,石槽的为0.245。利用统计软件SPSS13.0进行相关分析,结果说明不同小生境和土层对土壤动物个体数量和类群数影响均不显著,组间的均方差（F值）分别为0.834和1.226,但小生境对土壤动物的生物量有显著的影响,F值为3.844。三种小生境中,石沟生境比较有利于土壤动物生存。 相似文献
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K. Lal Gauri 《Environmental Geology》1990,15(1):45-54
Stone objects decay in all environments, but the modes of decay vary from one region to another. In the modern industrial countries acid deposition has accelerated the decay of stone. Many objects that survived centuries of weathering without serious damage have, in the present century, decomposed beyond recognition. The black crusts seen on stone structures mostly contain gypsum formed by SO2 reactions with calcareous minerals. These crusts exfoliate, destroying the sculptural form. Because of the absence of proven technology to treat and restore these objects, the caryatids at the Acropolis had to be moved indoors to save them from further disfiguration.In arid climates, the salts in stone and the meteorologic conditions combine to disrupt stone structures. The Great Sphinx at Giza is a prominent example of this mode of stone decay. In humid, tropical regions, such as in southern India, hydrolysis disrupts the mineral structure, causing rapid damage even to such durable stone as granite.The human effort to save the deteriorating structures has often aggravated the problem. The sandstone at the Legislative Building in Olympia, Washington has, because of the protective acrylic coating, suffered greater damage than the similar but unprotected sandstone at a nearby school building.It appears that proper management can greatly help to reduce the decay of the stone. A scientifically designed cleaning can inhibit the formation of crusts and the accumulation of efflorescences. The absence of the crusts and efflorescence and application of appropriate impregnants, which consolidate yet maintain the "breathability" of stone, may prolong the life of historic structures. 相似文献