Environmental impact on construction limestone at humid regions with an emphasis on salt weathering,Al-hambra islamic archaeological site,Granada City,Spain: case study

Al-hambra is an immense and valuable archaeological site in Spain built on Sabika hill with red brick and natural sandy limestone. It exhibits weathering features indicating salt weathering process. The main aim of this study is to examine weathering processes and intensity acting on Al-hambra. Rock petrography and mineralogical composition have been examined using thin sections, scanning electron microscope, X-ray diffraction and X-ray fluorescence; limits of rock’s physical parameters using ultrasonic waves and mercury porosimeter; rock salt content through hydrochemical analysis. Salts attacking this structure are mainly from wet deposition of air pollutants on the long term chemical alteration of rock’s carbonate content to its equivalent salts. The salts’ concentration limit within the examined rock samples is considerably low but it is effective on the long run through hydration of sulphate salts and/or crystallization of chloride salts. Rock texture type and its silica as well as clay content reduces its resistance to internal stresses by salts as well as wetting and drying cycles at such humid area. The recession in limits of physical parameters examined for deep seated and weathered limestone samples quantitatively reflects weathering intensity on Al-hambra.     

High cadmium concentrations in Jurassic limestone as the cause for elevated cadmium levels in deriving soils: a case study in Lower Burgundy,France

Cadmium (Cd) is a highly toxic element and its presence in the environment needs to be closely monitored. Recent systematic surveys in French soils have revealed the existence of areas in eastern and central France, which show systematically high cadmium concentrations. It has been suggested that at least part of these anomalous levels are of natural origin. For the Lower Burgundy area in particular, a direct heritage from the Jurassic limestone bedrock is highly suspected. This potential relationship has been studied in several localities around Avallon and this study reports new evidence for a direct link between anomalously elevated cadmium contents of Bajocian and Oxfordian limestone and high cadmium concentrations in deriving soils. Soils in this area show cadmium concentrations generally above the average national population values, with contents frequently higher than the ‘upper whisker’ value of 0.8 μg g⁻¹ determined by statistical evaluation. In parallel, limestone rocks studied in the same area exhibit cadmium concentrations frequently exceeding the mean value of 0.030–0.065 μg g⁻¹ previously given for similar rocks by one order of magnitude, with a maximum of 2.6 μg g⁻¹. Mean ratios between the cadmium concentrations of limestone bedrock and deriving soils (Cd_soil/Cd_rock), calculated for different areas, range from 4.6 to 5.7. Calculations based on the analyses of both soils from a restricted area and fragments of bedrock sampled in the immediate vicinity of high-concentration soils are around 5.5–5.7. Cd_soil/Cd_rock is useful in determining the potential of soils in Lower Burgundy to reflect and exacerbate the high concentrations of cadmium present in parent bedrocks.     

Exchange of marine sodium for calcium during chemical weathering in the Isle aux Morts River basin,Newfoundland

Seasalt corrections applied to major-ion data for the Isle aux Morts River, Newfoundland, using Cl^? as the seawater indicator species, produce numerous negative values of Na⁺ that occur chiefly in the winter, when the seasalt concentrations are high. The negative values of Na⁺ are accompanied by slightly higher than usual concentrations of Ca⁺⁺, suggesting an exchange reaction of the form: $\text{Ca}\text{silicate}\text{+ 2 Na}{}^{\mathrm{+}}\text{= Na}{}_2\text{silicate}\text{+ Ca}{}^{\mathrm{++}}$, that is driven by seasalt.That the river receives seasalt inputs of normal major-ion seawater composition is indicated by analysis of precipitation chemistry data for nearby coastal stations.     

Geology as a control on landslides on the Isle of Wight: an overview

The Cretaceous and Palaeogene sedimentary rocks that crop out on the Isle of Wight are highly prone to landsliding and the island offers an important field laboratory wherein to investigate a number of the different types of failure. Many of these landslides represent a significant engineering hazard, with several urban areas requiring remedial work and planning constraints (e.g. The Undercliff and Seagrove Bay) to aid development. Previous studies have thoroughly investigated the major landslides in the Undercliff area around Ventnor and presented a mechanism for that massive failure. This overview of the landslides throughout the Isle of Wight by the British Geological Survey was completed as part of the multidisciplinary survey of the surface geology, structure, geophysical response and offshore interpretations of the island between 2007 and 2010. The survey has collected new observational data on the extensive coastal landslides, as well as the distribution, nature and mechanism of failure of the lesser-studied inland examples.     

Ornamental stone potential areas for land use planning: a case study in a limestone massif from Portugal

Nowadays, the difficulties of the mining sector in accessing the territory are mostly related to inadequate land use plans. Mineral potential maps have become quite relevant for the land use planning authorities as a decision support tool. This work’s goal is to present a methodology based on geological criteria, for the delimitation of potential areas for ornamental stones production in a limestone area of Portugal known as Maciço Calcário Estremenho. This is one of the world’s most important regions producing limestone blocks for ornamental purposes. The methodology, applied at a scale similar to the commonly used in land use planning, considers two main geological-based criteria for the definition of potential areas, namely the homogeneity criterion, related to the textural and chromatic homogeneity of the potentially productive lithologic units, and the dimension criterion, which refers to the thickness of the productive unit, to the volume of the deposit and to its spatial layout. Based on the criteria, two main types of potential areas for ornamental stones’ production were delimited: specific areas, where the lithostratigraphic units demonstrate ornamental suitability at a very local scale due to highly appreciated particular features, and areas corresponding to the entire outcrop area of some of the lithostratigraphic units, which due to the resource volume are the most relevant potential areas.     

Morphology and mineralogy of weathering crusts on highly porous oolitic limestones, a case study from Budapest

Black crusts are very common on limestones in polluted urban environments, but white crusts are less frequently developed. On the soft, porous and inherently weak oolitic limestone of Budapest both crusts are frequent, and indeed white ones are more common on the stone walls of the studied fortress. In this paper, black and white crusts and the host rock have been described using morphological criteria, mineralogical analyses (XRD, DTA), elements analyses (microprobe) and micro-morphological (SEM) tests. The analyses have shown that on white crusts the surface dissolution is combined with the precipitation of gypsum and calcite in the pores and accumulation of gypsum on the underside of the crust. Thin white crusts are removed by a combination of salt crystallisation (gypsum) and frost action while very thick stone layers scale off due to freeze-thaw cycles. Black crusts are enriched in gypsum relative to white crusts. Gypsum accumulates on the crust surface and signs of dissolution have not been observed. Airborne particulates (flyash, silt-sized quartz, and organic debris) adhere to the crust surface of sheltered black crusts. These particles are later incorporated into the expanding gypsum crystals, that are visible on the underside of the crust. The host rock also contains gypsum, but it is washed off the surface when the crust is removed. Further exposure of the host rock may lead to the dissolution of calcite crystals as it is observed by SEM. The micro-environment influences the crust formation and adherence of the crusts. On frequently wet and dry surfaces crust removal is more common. The crust serves as a protective layer on the stone surface, but this protection is temporary since trigger mechanisms such as salt crystallisation or frost action can cause rapid surface loss.Special Issue: Stone decay hazards     

Mineralogy, geochemistry, and reserve estimation of the Euphrates limestone for Portland cement industry at Al-Najaf area, South Iraq

This study deals with the mineralogical and geochemistry of the Euphrates Formation (Lower Miocene) in Bahr Al-Najaf area in order to assess the lithofacies of the Euphrates Formation for Portland cement manufacturing. Petrographic and mineralogical studies were carried out on 210 core samples, collected from 21 boreholes, and showed that calcite is the dominant mineral with few amounts of quartz, gypsum, feldspar, and a rare amount of dolomite. Clay mineral suites (palygorskite, kaolinite, montmorillonite, and illite) formed about 5% from the total mineral composition. Palygorskite precipitated directly in alkali shallow water rich with Si and Mg ions. Chemical weathering of feldspar under acidic conditions participated in formation of Kaolinite. Geochemistry showed that there is no high variation in chemical constituents with depth, and the average of CaO (51.5), MgO (0.83), SO₃ (0.54), SiO₂ (4.3), Fe₂O₃ (0.45), Al₂O₃ (0.93), L.O.I (40.7), Na₂O₃ (0.08), K₂O (0.14), and Cl^- (0.1) qualified the lithofacies of Euphrates Formation to be raw materials suitable for manufacturing the Portland cement. Triangle Block method is applied to estimate the reserve on square area (2?×?2 km²) which is computed to be 63 million tons of medium-tough limestone as potential probable reserve.     

Very low temperature,natural deformation of fine grained limestone: a case study from the Lucania region,southern Apennines,Italy

The deformation behavior of fine grained limestones from the Monte Sirino area (Lucania region) of the southern Apennines has been analysed by constraining microstructural observations and crystallographic fabrics with data on the metamorphic conditions of deformation. X-ray and infrared analysis of clay minerals, together with illite ‘crystallinity’ data, suggest that the studied rocks underwent very low grade metamorphism in the deep diagenetic zone. The limestones consist of very fine grained (<10 μm) aggregates of micrite. Elliptically-shaped radiolarians, preserved as moulds with coarser (>20 μm) crystalline fillings, provide common strain markers. Optical microstructures and strain analysis indicate heterogeneous intracrystalline strain in the coarser (>50 μm) calcite. On the other hand, SEM and TEM observations, and crystallographic fabrics determined by X-ray texture goniometry, indicate a deformation involving not only intracrystalline slip, but also an important component of grain boundary sliding in the fine grained matrix. The inferred microscopic deformation mechanisms are compared with constitutive flow laws derived from experimental studies. For the maximum inferred temperature of deformation of 250 °C and geologic strain rates of 10^–13–10^–15 s^–1, deformation mechanism maps for calcite suggest twinning and other glide mechanisms to be active in grains larger than about 5–10 μm. Smaller grains would be mostly deformed by grain size sensitive creep mechanisms, which include both diffusion mass transfer processes and grain boundary sliding. Deformation features observed in the study limestones are compatible with the prediction of such temperature-dependent mechanism maps.     

Very low temperature,natural deformation of fine grained limestone: a case study from the Lucania region,southern Apennines,Italy

Abstract

The deformation behavior of fine grained limestones from the Monte Sirino area (Lucania region) of the southern Apennines has been analysed by constraining microstructural observations and crystallographic fabrics with data on the metamorphic conditions of deformation. X-ray and infrared analysis of clay minerals, together with illite ‘crystallinity’ data, suggest that the studied rocks underwent very low grade metamorphism in the deep diagenetic zone. The limestones consist of very fine grained (<10 μm) aggregates of micrite. Elliptically-shaped radiolarians, preserved as moulds with coarser (>20 μm) crystalline fillings, provide common strain markers. Optical microstructures and strain analysis indicate heterogeneous intracrystalline strain in the coarser (>50 μm) calcite. On the other hand, SEM and TEM observations, and crystallographic fabrics determined by X-ray texture goniometry, indicate a deformation involving not only intracrystalline slip, but also an important component of grain boundary sliding in the fine grained matrix. The inferred microscopic deformation mechanisms are compared with constitutive flow laws derived from experimental studies. For the maximum inferred temperature of deformation of 250 °C and geologic strain rates of 10^?13?10^?15 s^?1, deformation mechanism maps for calcite suggest twinning and other glide mechanisms to be active in grains larger than about 5?10 μm. Smaller grains would be mostly deformed by grain size sensitive creep mechanisms, which include both diffusion mass transfer processes and grain boundary sliding. Deformation features observed in the study limestones are compatible with the prediction of such temperature-dependent mechanism maps. © 2001 Éditions scientifiques et médicales Elsevier SAS     

A case study on the behaviour of a deep excavation in sand

A complete case record of an excavation in sand is explored in this study. Numerical analyses were conducted to evaluate the influences of soil elasticity, creep and soil–wall interface. Back-analyses indicate small strain parameters should be used if an elastic–perfect plastic model is selected. In addition, excavation-induced seepage has only a limited effect on vertical displacements. Delayed installation of 3rd level struts and base slab construction caused significant time-dependent (creep) movements during the excavation. Back-analyses show that the dynamic viscosity (D_v) used in the visco-elastic model for creep simulation is in the range of 1.5 × 10¹⁵–2.0 × 10¹⁵ Pa, but there are still inconsistencies in movements both near to and far from the excavation. Interpreting from observation data, the creep rate of wall movement caused in the non-supported stage of the excavation varies between 0.14 and 0.38 mm/day. Finally, parametric studies of interface elements indicate that the most sensitive parameters are the normal (K_n) and shear stiffness (K_s) of the interface. Back-analyses using an elastic–perfect plastic model indicate that using 3 × 10⁶ Pa for K_n and K_s produces more acceptable results.     

矿山地质环境治理工程设计思路探讨——以广西凤山县石灰岩矿山为例

我国许多废弃和老矿山未实施地质环境治理和土地恢复工程,矿区内环境恶劣.为了解决废弃矿山遗留的环境问题,国家提供了专门的政策和资金进行治理,但亟需从技术层面上提出一套适合国情的设计理论.在总结废弃矿山地质环境治理工程特点的基础上,提出了矿山地质环境治理工程设计的原则、指标和流程,并将设计理论用于广西凤山石灰岩矿山的治理工程设计.结果表明:(1)矿山地质环境问题复杂多样,治理工程涉及环境地质、生态地质、岩土工程、环境工程和景观工程等多学科交叉.治理工程设计需要综合考虑地质环境问题、可行性、效益和社会需求四个主要指标.(2)凤山石灰岩矿山的地质环境问题包括松动危岩、潜在崩塌体、土地和植被资源占用与破坏、地形地貌景观破坏.采取截水、锚固、落石平台和岩石雕刻将采石掌子面改造为公园的景点,并通过岩壁雕刻宣传当地的民俗文化.(3)治理工程消除了废弃采石矿山的地质灾害安全隐患,同时,建设成世界级的雕刻景点,从环境、经济和社会三方面体现了治理工程的效益.     

Interaction between groundwater, the hyporheic zone and a Chalk stream: a case study from the River Lambourn, UK

Understanding the processes controlling groundwater/surface-water interaction is essential for effective resource management and for protecting sensitive ecosystems. Through intensive monitoring of Chalk groundwater, shallow gravel groundwater and surface water in the River Lambourn, UK, using a combination of hydrochemical and hydrophysical techniques, a complex pattern of interactions has been elucidated. The river is broadly in hydraulic contact with the streambed sediments and adjacent gravels and sands, but these deposits are mainly hydraulically separate from the underlying Chalk at the site. The hydraulic relationship between the river and underlying alluvium is variable, involving components of groundwater flow both parallel and transverse to the river and with both effluent and influent behaviour seen. While the gravel aquifer is significant in controlling groundwater/surface-water interaction, its importance as a route for flow down the catchment is likely to be modest compared with river discharge. The hydrological complexity revealed in a geological setting typical of lowland UK Chalk streams has implications both for investigation methods and for management such as in the setting of environmental objectives in the European Water Framework Directive.     

Late Devensian and Holocene relative sea‐level changes on the Isle of Skye,Scotland, UK

Detailed litho‐ and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the Isle of Skye, Scotland, UK, reveal evidence for several changes in relative sea level during the Late Devensian and Holocene. At the start of the record, relative sea level in the area was high at ca. 12 500 ¹⁴C (ca. 14 800 cal.) yr BP but then fell, reaching a low point during the Younger Dryas, at ca. 11 000–10 000 ¹⁴C (ca. 13 000–11 600 cal.) yr BP, when a rock platform, correlated with the Main Rock Platform, was formed. In the early–middle Holocene, relative sea level was rising by ca. 8000 ¹⁴C (ca. 8800 cal.) yr BP and in northeast Skye a lagoonal surface, correlated with the Main Postglacial Shoreline, was formed at ca. 6600 ¹⁴C (ca. 7500 cal.) yr BP. By the late Holocene, relative sea level was again falling, but a rise, registered at at least two sites, began probably before ca. 4000 ¹⁴C (ca. 4500 cal.) yr BP, and a second lagoonal surface in northeast Skye, correlated with the Blairdrummond Shoreline, was formed, although by ca. 3000 ¹⁴C (ca. 3200 cal.) yr BP relative sea level in the area had resumed its downward trend. The pattern of relative sea‐level changes disclosed is compared with evidence elsewhere in Scotland. Copyright © 2006 John Wiley & Sons, Ltd.     

关于饰面用灰岩勘查开发工业指标问题探讨——以广西为例

文章根据我国地质勘查规范中有关饰面用灰岩工业指标与广西饰面用灰岩勘查与开发利用的不匹配案例,分析了广西饰面用灰岩勘查与开发利用的实际情况,认为有必要结合开发现状和市场需求,对饰面用灰岩矿产工业指标具体内容进行调整和灵活运用。     

Changing climate, changing process: implications for salt transportation and weathering within building sandstones in the UK

Salt weathering is a crucial process that brings about a change in stone, from the scale of landscapes to stone outcrops and natural building stone façades. It is acknowledged that salt weathering is controlled by fluctuations in temperature and moisture, where repeated oscillations in these parameters can cause re-crystallisation, hydration/de-hydration of salts, bringing about stone surface loss in the form of, for example, granular disaggregation, scaling, and multiple flaking. However, this ‘traditional’ view of how salt weathering proceeds may need to be re-evaluated in the light of current and future climatic trends. Indeed, there is considerable scope for the investigation of consequences of climate change on geomorphological processes in general. Building on contemporary research on the ‘deep wetting’ of natural building stones, it is proposed that (as stone may be wetter for longer), ion diffusion may become a more prominent mechanism for the mixing of molecular constituents, and a shift in focus from physical damage to chemical change is suggested. Data from ion diffusion cell experiments are presented for three different sandstone types, demonstrating that salts may diffuse through porous stone relatively rapidly (in comparison to, for example, dense concrete). Pore water from stones undergoing diffusion experiments was extracted and analysed. Factors controlling ion diffusion relating to ‘time of wetness’ within stones are discussed, (continued saturation, connectivity of pores, mineralogy, behaviour of salts, sedimentary structure), and potential changes in system dynamics as a result of climate change are addressed. System inputs may change in terms of increased moisture input, translating into a greater depth of wetting front. Salts are likely to be ‘stored’ differently in stones, with salt being in solution for longer periods (during prolonged winter wetness). This has myriad implications in terms of the movement of ions by diffusion and the potential for chemical change in the stone (especially in more mobile constituents), leading to a weakening of the stone matrix/grain boundary cementing. The ‘output’ may be mobilisation and precipitation of elements leading to, for example, uneven cementing in the stone. This reduced strength of the stone, or compromised ability of the stone to absorb stress, is likely to make crystallisation a more efficacious mechanism of decay when it does occur. Thus, a delay in the onset of crystallisation while stonework is wet does not preclude exaggerated or accelerated material loss when it finally happens.