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11.
Quantification of weathering depths in slightly weathered tuffs 总被引：5，自引：0，他引：5
Tamer Topal 《Environmental Geology》2002,42(6):632-641
Slightly weathered white and pink tuffs of Midas monument have deterioration problems. In this study, depths of the weathering zones developed in the tuffs are investigated through optical microscopy, XRD, chemical analyses, SEM and some index parameters. By examining quantitative weathering indices and comparing them with thin section studies, it is found that thin section analyses of the phenocrysts, LoI and WPI are good indicators to quantify the depth of weathering for the tuffs. However, thin section studies have limited value for fine-grained tuffaceous matrix. The chemical weathering of the tuffs produces weathered zones that are 4.5 cm thick within the white tuff and 2.5 cm thick within the pink tuff. Physical weathering causes fracturing of feldspars along their cleavage planes. Variations of the index properties of the tuffs caused by weathering are not significant enough to quantify the weathering depths in the tuffs. 相似文献
12.
Cut slopes are prone to fail due to the disturbance on original geometry and strength. In addition, because of these disturbances and stress relief, natural apertures which increase the weathering effects widen in engineering time. Owing to these reasons, slope stability assessment has a prominent role on these road cuts. Generally, slope stabilities are assessed by deterministic approaches with a significant engineering judgment. Because of this reason the reputation of probabilistic approaches is increasing. In this study, 20 road cuts located in North West Black Sea region of Turkey were evaluated using slope stability probability classification (SSPC). Considering this probabilistic approach, rock strength parameters and failure mechanisms were determined. Furthermore, slope mass rating (SMR) classification was applied for each road cut in order to compare with the results obtained from SSPC. These overall results were then evaluated with the field observations considering rockslope deterioration assessment (RDA) and Falling Rock Hazard Index (FRHI) for the disturbed/weathered zones, and failure mechanisms. According to these, SSPC is found to be more accurate for surficial degradations (raveling and fall) using samples taken from the disturbed/weathered zones rather than using relatively fresh samples beyond the disturbed zone. Moreover, despite strength differences between weathered and relatively fresh zones, SMR classification is identified to reveal the same stable probabilities. It is found that SSPC shows more detailed probabilistic results than SMR. Lastly, rockfall and raveling mechanisms determined by RDA and rockfall risk by FRHI were found to be coherent with SSPC and field observations. 相似文献
13.
Natural Hazards - The eastern shore of Lake Van was shaken by a powerful earthquake (M w 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the... 相似文献
14.
Black Sea coast line is a hazardous region especially in winter due to the dominant wave action. Therefore, rubble mound breakwaters protected with armourstone used as ship shelters are vital structures especially for the fishermen. The deterioration of the armourstone with time in the form of abrasion and disintegration may result in the failure of the breakwater. In this study, the properties of the armourstone taken from an andesite quarry and used in the Hisarönü rubble mound breakwater were studied both in field and laboratory in order to assess their qualities and long-term durabilities. Based on the in situ observations and laboratory tests, the andesite is found to be generally marginal rock. CIRIA/CUR, RDIs, RERS and Wet-Dry strength ratio classifications are in good agreement with the in situ observations and the results of the laboratory tests. However, RDId, Average Pore Diameter and Saturation Coefficient classifications cannot correctly predict long-term durability of the armourstone. Field studies reveal that block size of the andesite in the quarry increases with depth due to the increase in spacing of the cooling joints of the rock. 相似文献
15.
The Kastamonu Castle located on a sandstone hill with Eocene age is one of the most historical and touristic places in Kastamonu city center. The settlement of the city expanded towards the hill of the Kastamonu Castle and adversely affected by rockfalls in the past. The rockfall problems around the castle could be related to jointing, weathering, freezing-thawing and earthquake effects or a combination. In this study, the rockfall hazard at the castle is evaluated by two-dimensional rockfall analyses along 17 profiles selected in different orientations. Different size of rock blocks and various types of movements are taken into consideration in the analyses. Fall-out distance, bounce height, kinetic energy and velocity of the sandstone blocks are separately evaluated. The obtained data are used to define the possible rockfall hazard zones. Finally, the areas having potential rockfall risks are distinguished. Based on the evaluation of the data, rock bolting after removing of unstable blocks and supporting the area with the protective fences are suggested. 相似文献
16.
A methodology to model seismic microzonation maps is required in the hazard mitigation decision plans of the earthquake prone areas. The stage of disaster preparedness for new residential places is of great importance for detailed seismic microzonation models. The effects of local geological and geotechnical site conditions were considered in order to establish site characterization as the initial stage of the models in this study. Dynamic soil properties based on the empirical correlations between shear wave velocity (V s) and standard penetration test blow counts were taken into account in order to define representative soil profiles extending down to the engineering bedrock. One-dimensional site response analyses were performed to analyze earthquake characteristics on the ground surface. The layers for soil classification, geology, depth to groundwater level, amplification, distance to fault, slope and aspect, and liquefaction-induced ground deformation potential of the study area were prepared in seismic microzonation models. The study area, Erbaa, is placed along the seismically active North Anatolian Fault Zone. Final seismic microzonation map of the study area was evaluated applying different GIS-based Multi-Criteria Decision Analysis (MCDA) techniques. Two of the MCDA techniques, simple additive weighting and analytical hierarchical process (AHP), are considered during the evaluation step of the final seismic microzonation map. The comparison is made in order to distinguish two different maps based on these MCDA techniques. Eventually, AHP-based seismic microzonation map is more preferable for the seismic design purposes in this study. 相似文献
17.
Oktay Erten Mehmet Siddik Kizil Erkan Topal Lachlan McAndrew 《Natural Resources Research》2013,22(3):207-227
Tropical laterite-type bauxite deposits often pose a unique challenge for resource modelling and mine planning due to the extreme lateral variability at the base of the bauxite ore unit within the regolith profile. An economically viable drilling grid is often rather sparse for traditional prediction techniques to precisely account for the lateral variability in the lower contact of a bauxite ore unit. However, ground-penetrating radar (GPR) offers an inexpensive and rapid method for delineating laterite profiles by acquiring fine-scale data from the ground. These numerous data (secondary variable) can be merged with sparsely spaced borehole data (primary variable) through various statistical and geostatistical techniques, provided that there is a linear relation between the primary and secondary variables. Four prediction techniques, including standard linear regression, simple kriging with varying local means, co-located cokriging and kriging with an external drift, were used in this study to incorporate exhaustive GPR data in predictive estimation the base of a bauxite ore unit within a lateritic bauxite deposit in Australia. Cross-validation was used to assess the performance of each technique. The most robust estimates are produced using ordinary co-located cokriging in accordance with the cross-validation analysis. Comparison of the estimates against the actual mine floor indicates that the inclusion of ancillary GPR data substantially improves the quality of the estimates representing the bauxite base surface. 相似文献
18.
A new natural gas pipeline with a 0.90-m diameter is under construction to provide a gas connection between Turkey and Greece
as well as to create a gas ring for southern Europe. The new pipeline route lies next to an existing small diameter gas pipeline
broken by a landslide that occurred in February 2006 near Karacabey (Bursa). Although the existing pipeline has been temporarily
repaired, either the pipeline route should be relocated or the landslide should be stabilized. The geological survey conducted
in the study area reveals that relocation is not feasible due to the existence of other landslides in close vicinity to the
site. In order to investigate the causes of the landslide and to suggest possible remedial measures, geotechnical investigations
including surface geological mapping, trial pitting, drilling with field tests, inclinometer measurements, laboratory testing,
and limit equilibrium analyses were conducted. The investigation revealed that the unconsolidated clayey soil slid on claystone
along a non-circular failure surface. Based on the gathered data, possible remedial measures including partial removal of
landslide material and construction of toe buttresses, slope flattening, lowering the pipeline, and surface drainage systems
were evaluated. These are suggested to prevent the reactivation of the landslide, and thus to establish a safe route for both
the existing and the new pipelines. 相似文献
19.
Cappadocian monuments that are within tuff have serious deterioration problems. Understanding the effects of lichens on the tuffs is of utmost importance. In this paper, interactions between lichen-coated surfaces of Cappadocian monuments and the rock substratum have been studied. Thin sections and freshly cut sections were investigated by light and scanning electron microscopy. The presence of clay minerals and zeolites as weathering by-products produced by alteration and hydrolysis of glass and feldspars was assessed by XRD patterns. Furthermore, some physical properties of the tuff coated by and free of lichens were measured and compared. Analysis of mineralogical data has shown that the main weathering mechanism can be identified as hydrolysis of some of the rock-forming minerals. The lichenic coat reduces the presence of water inside the rock, thus protecting the rock material from physical decay and disintegration. 相似文献
20.
Deterioration mechanisms of tuffs in Midas monument 总被引：3，自引：0，他引：3
Slightly weathered white and pink tuffs of the Midas monument have deterioration problems. In this study, depths and characteristics of the weathering zones developed within the tuffs are investigated through optical microscopy, X-ray diffractometry (XRD), chemical analyses, scanning electron microscopy (SEM) and some index parameters. Accelerated weathering tests including wetting–drying, freezing–thawing and salt crystallization are performed, and durability assessment methods are used to predict the durabilities of the tuffs. The findings are compared with field observations. By examining quantitative weathering indices and comparing them with thin section studies, it is found that thin section analyses of the crystals, LoI, and WPI are good indicators to quantify the depth of weathering for the tuffs. However, thin section studies have limited value for fine-grained tuffaceous matrix. The chemical weathering of the tuffs produces weathered zones that are 4.5-cm thick within the white tuff and 2.5-cm thick within the pink tuff. Physical weathering causes scaling of outer layers of the tuffs and fracturing of feldspars along their cleavage planes. However, variations of the index properties of the tuffs due to weathering are not so significant to quantify the weathering depths in the tuffs. Among the accelerated weathering tests, salt crystallization is found to be the most destructive environmental condition. Pigeon droppings rich in NO31− are found to be the main source of soluble salt at the Midas monument. The salt transported up by capillary rise due to surface water causes spalling of the tuffs in the capillary zone. Surface water and salt of any kind in the close vicinity of the monument should be totally eliminated for the purpose of conservation. Field observations and the durability equations reveal that the white tuff is less durable than the pink tuff. Wet-to-dry strength ratio yields a better stone durability assessment among various durability methods used in this study. 相似文献