Kizilkaya ignimbrite, characterized by a blocky structure in the Ihlara Valley (Cappadocia, Turkey), poses many hazards to visitors and the human-made churches and dwellings carved in the valley ...slopes. The instability mechanism in the valley should be carefully investigated to determine and implement a suitable prevention method. For this purpose, the finite element method (FEM) models were developed in RS2 software to illustrate the problem of progressive failure in the valley's cliffs. A simple geometry represented the rock strata and its surroundings. The effect of columnar structure on the cliff stability was mimicked as a jointed medium in two-dimensional numerical models. The results of FEM models revealed that as the stage of failure progresses in the slope, the strength reduction factor decreased subsequently from 2.05 to 0.45. These models correctly captured the prevailing failure mechanisms observed in the valley slopes. Depending on the size of the rock blocks described in the FEM analysis, an effective support system was proposed to remedy the slope failure. It was found that fully bonded rock bolts with a length of at least 2.5 times the width of a typical block should be implemented with a certain grid pattern. The study clearly showed that it was promising to realize a numerical solution to secondary toppling failure in a jointed rock mass using the FEM.
Rockfalls are one of the most dangerous natural events in hilly terrains, and they substantially threaten residential areas and transport corridors in these environments. This study is aimed to ...analyze the risk of rockfall from a slope to nearby houses in a historical settlement with past rockfall histories. It contains numerous applications to study rockfall danger from different points of view (e.g., kinematics, numerical stability analysis, risk assessment, 2D trajectory). The rockfall kinematics revealed the statistics for different structurally controlled failure modes among the surveyed slope discontinuities, especially wedge type and block toppling were the most significant ones. Finite element analysis showed that the slope was stable under the natural condition with a safety factor of 2.19. The rockfall risk rating system calculated a medium risk for the houses downstream. Based on the field measurements, a possible rockfall profile was determined and located as an input in the 2D rockfall trajectory program. The rigid-body impact model runs utilized various shapes and sizes of blocks to simulate the rockfall events realistically. According to the 2D trajectory model results, there was no rockfall danger for the investigated downslope houses. The study showed the importance of using different analysis techniques to solve rockfall risk in protected areas based on scientific and rational approaches.
Engineering design in soft rocks and its stability analysis exerts many challenges to rock engineers. Many engineering works in Turkey’s Cappadocia region must face and tackle the existing sites ...covered by the soft rocks. This study is aimed to examine the stability condition of a typical underground storage cavern (USC) excavated in a soft rock in this region. For this purpose, two- and three-dimensional stability analyses of the USCs were performed using the finite element method (FEM). Because of the inherent difficulty in characterizing soft/weak rock masses in the region using traditional classification systems, the stability of a typical USC was evaluated by representing the rock mass condition with two distinct scenarios in FEM analysis. While these structures were unstable according to the 2D analysis conducted in RS2 software in the worst-case scenario, they were stable in the 3D analysis using RS3 software in both scenarios. Besides, feasible cover depths were examined to assess their possible effects on the factor of safety and deformation measurements. It was found that 15 m seems to be an optimal depth for excavating a typical USC in the soft rocks exposed in the region. The 3D FEM results provide valuable information to optimize the future planning and preliminary design of USCs.
Representative elementary volume (REV) is defined as the usual size of a rock mass structure beyond which its mechanical properties are homogenous and isotropic, and its behavior can be modeled using ...the equivalent continuum approach. Determination of REV is a complex problem in rock engineering due to its definition ambiguity and application area. This study is one of the first attempts to define a REV for jointed rock masses using the equivalent continuum approach. It is aimed to numerically search a ratio between the characteristic size of an engineering structure and pre-existing joint spacing, which are the two most important contributing elements in assessing REV. For this purpose, four hypothetical engineering cases were investigated using the RS2 (Phase2 v. 9.0) finite element (FE) analysis program. An underground circular opening with a constant diameter, an open-pit mine with varying bench heights, a single bench with a constant height, and an underground powerhouse cavern with a known dimension were executed for possible changes in the safety factor and total displacement measurements under several joint spacing values. Different cut-off REVs were calculated for FE models depending on the type of excavation and measurement method. An average REV size of 19.0, ranging between a minimum of 2 for tunnels and a maximum of 48 for slopes, was found in numerical analysis. The calculated sizes of REV were significantly larger than the range of values (5 to 10) commonly reported in the relevant geotechnical literature.
The analysis of stability of slopes is a classical problem for geotechnical engineers. In practice, many methods are available for the desired purpose, from basic kinematic analysis to two- and ...three-dimensional limit equilibrium analyses and numerical modeling with various user-friendly softwares. However, additional techniques are also required to provide knowledge necessary for decision-making. In this research, a reliable dataset provided by Sah et al. (
1994
) was used to analyze the stability evaluation of rock slopes subjected to circular failures. For this purpose, using Slide 2018 program, 44 separate limit equilibrium slope models were built for each case given in the original work. The provided material properties and slope geometries in heavily fractured and/or very weak or highly weathered rock masses were considered during the model building stage. It was found that Slide 2018 program generated dissimilar safety factors compared to those given by Sah et al. (
1994
) for the investigated slope cases. Binary logistic and multiple linear regression techniques were implemented in the study to promote alternative approaches for the prediction of the stability condition and safety factor (SF) of slopes excavated in heavily fractured/highly weathered rock masses. The condition of slopes (stable or failed) was predicted by binary logistic regression model with 90.9% accuracy. The SF of the slopes was estimated by a multiple linear regression model with 95.6% accuracy. It was concluded that both statistical techniques could be sufficiently used as alternative approaches to predict the stability condition and SF of rock slopes prone to circular (rotational) failures.
In this study, the concentration of ambient persistent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides ...(OCPs) were measured for 12 months in urban and semi-urban areas using a passive air sampler. During the sampling period, a total of 14 PAH (∑
14
PAH) concentrations measured in urban and semi-urban areas were found to be 54.4 ± 22.6 ng/m
3
and 51.7 ± 34.3 ng/m
3
, respectively. Molecular diagnostic ratios (MDRs) were used to determine PAH sources. According to the MDR values, combustion sources were the most important PAH sources in both sampling areas. However, since the urban area is close to the industrial zone, the combustion sources occurred at high temperatures (> 800 °C), while the sources in the semi-urban area generally consisted of petrogenic fuel combustion. ∑
50
PCB concentrations measured in the urban and semi-urban areas were found to be 522.5 ± 196.9 pg/m
3
and 439.5 ± 166.6 pg/m
3
, respectively. Homologous group distributions were used to determine the source of PCBs. According to the homologous group distributions, tri-, tetra-, and penta-chlorinated PCBs were dominant in both sampling areas. ∑
10
OCP concentrations measured in urban and semi-urban areas were found as 242.5 ± 104.6 pg/m
3
and 275.9 ± 130.9 pg/m
3
, respectively. Also, α-HCH/γ-HCH and β-/(α + γ)-HCH ratios were used to determine the source of OCPs. Lindane was the predominant OCP in both sampling areas.
Pine trees are used as biomonitoring agents to evaluate atmospheric polycyclic aromatic hydrocarbons (PAHs). Due to industrialization, urban construction, and rapid population growth, the city of ...Bursa is experiencing air pollution. In this study, PAHs were measured in pine tree branches and needles at a wastewater treatment plant site, an industrial site, and semirural site in Bursa for 12 months. The concentrations fluctuated depending on the characteristics of the areas. The lowest concentration value was measured in the semirural site while the highest value was determined in the wastewater treatment plant site. The PAH concentrations in pine needles ranged from 24 to 2565 ng/g dry weight (DW) and in pine branches from 163 to 2871 ng/g DW for 16 PAHs. Naphthalene, phenanthrene, fluorene, and fluoranthene were determined as dominant species in both tree components. Diagnostic ratios, ring profile, principal component analysis, the coefficient of divergence, and the Pearson correlation coefficient methods were used in the definition of sources of PAHs in the sampling sites, although all source identification methods have advantages and disadvantages. According to the results, the PAHs mainly originated from biomass and coal burning, traffic, and mixed sources. It also was concluded that three sampling sites showed higher PAH concentrations during winter, and the main PAH sources were similar.
In recent years, honeybees and bee products such as pollen and honey have been used as bioindicators for monitoring environmental pollution. Unfortunately, there are few studies about polychlorinated ...biphenyl (PCB) concentrations in honeybees and bee products from Turkey. Honeybee and pollen samples were taken between May and September 2017, and honey samples were taken between July and September 2017 at urban and semi-urban areas in Bursa (Turkey). PCB concentrations measured by gas chromatography-microelectron capture detector (GC-μECD) were found to be 135.46 ± 6.53, 81.47 ± 23.52, and 106.35 ± 21.60 ng g
−1
dry weight (dw) for honeybee, pollen, and honey samples in the urban area, respectively; and 126.35 ± 26.54, 67.57 ± 27.34, and 118.88 ± 55.28 ng g
−1
dw for honeybee, pollen, and honey samples in the semi-urban area, respectively. Pearson correlation was made between meteorological parameters and pollutant concentrations. According to the correlation results, a significant relationship was found between the pollen and honey results and the total cloudiness and temperature in the semi-urban area. The coefficient of divergence (COD) and Pearson correlation coefficient (PCC) methods were applied to determine the similarities and differences between the pollutant concentrations and sources of the two areas and the temporal variation. According to these two methods, PCB concentrations and emission sources in honeybee and pollen samples in urban and semi-urban areas were generally different in May and June, and similar in August and September.
Undoubtedly, as a result of the large-scale accidents that occurred in the near past in the underground coal mining industry, the issue of the necessary safety precautions and measures to be taken in ...coal mines has re-emerged. Within the purpose of this study, a risk-based classification of the coal mine basins (CBs) in Turkey’s hierarchy was created and the effects of basin-specific conditions on the risk management process were evaluated. In total, 39 licensed underground coal mines individually visited and 191 experts (senior executives, mining engineers, production engineers, permanent supervisors, and occupational health and safety (OHS) experts, etc.) were consulted for their opinions about their working coal mines’ OHS conditions through surveys. The hierarchy consisted of 6 alternatives and 26 sub-criteria, and the under coal seam properties, rock mechanic properties, demographic and geographic features, business management and economic parameters, and technology features and level were the main criteria. The CBs were enterprises using mostly underground coal production methods with elevated production in Turkey as alternatives in the hierarchy were classified from very risky to less risky by calculating risk scores for the main criteria and sub-criteria using the analytic hierarchy process (AHP). According to the results, the Zonguldak CB (0.256) has the highest risk score, followed by the Soma CB (0.193), the Ermenek CB (0.172), the Beypazari CB (0.168), the Trakya CB (0.107), and then the Kutahya CB (0.104). The underground water sub-criterion (0.490) has the highest risk score for the whole hierarchy. Additionally, the highest sub-criteria risk scores were computed for all CBs. The priority risks of experts in each CB varied depending on the specific conditions of each basin, so the calculated risk scores differed within themselves. While the productivity criterion (0.455) has the highest risk score for the Zonguldak CB, for the Soma CB, it was education level of miners (0.383), and for the Ermenek CB, it was enterprise type (0.481). By evaluating the effects of basin-specific conditions on the risk management process, the OHS measures to be taken were determined for effectively eliminating or mitigating the risks of the basins.
To determine whether international normalized ratio (INR), bilirubin, and creatinine predict bleeding risk following percutaneous liver biopsy.
A total of 870 consecutive patients (age 53 ± 14 years; ...53% (459/870) male) undergoing non-targeted, ultrasound-guided, percutaneous liver biopsy at a single tertiary center from 01/2016 to 12/2019 were retrospectively reviewed. Results were analyzed using descriptive statistics and logistic regression models to evaluate the relationship between individual and combined laboratory values, and post-biopsy bleeding risk. Receiver operating characteristic (ROC) curves and area under ROC (AUC) curves were constructed to evaluate predictive ability.
Post-biopsy bleeding occurred in 2.0% (17/870) of patients, with 0.8% (7/870) requiring intervention. The highest INR within 3 months preceding biopsy demonstrated the best predictive ability for post-biopsy bleeding and was superior to the most recent INR (AUC = 0.79 vs 0.61, p = 0.003). Total bilirubin is an independent predictor of bleeding (AUC = 0.73) and better than the most recent INR (0.61). Multivariate regression analysis of the highest INR and total bilirubin together yielded no improvement in predictive performance compared to INR alone (0.80 vs 0.79). The MELD score calculated using the highest INR (AUC = 0.79) and most recent INR (AUC = 0.74) were similar in their predictive performance. Creatinine is a poor predictor of bleeding (AUC = 0.61). Threshold analyses demonstrate an INR of > 1.8 to have the highest predictive accuracy for bleeding.
The highest INR in 3 months preceding ultrasound-guided percutaneous liver biopsy is associated with, and a better predictor for, post-procedural bleeding than the most recent INR and should be considered in patient risk stratification.
Despite correction of coagulopathic indices, the highest international normalized ratio within the 3 months preceding percutaneous liver biopsy is associated with, and a better predictor for, bleeding and should considered in clinical decision-making and determining biopsy approach.
• Bleeding occurred in 2% of patients following ultrasound-guided liver biopsy, and was non-trivial in 41% of those patients who needed additional intervention and had an associated 23% 30-day mortality rate. • The highest INR within 3 months preceding biopsy (AUC = 0.79) is a better predictor of bleeding than the most recent INR (AUC = 0.61). • The MELD score is associated with post-procedural bleeding, but with variable predictive performance largely driven by its individual laboratory components.
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