Simulation of Slightly Degraded Reinforced Concrete Shaft Lining in Thick Topsoil

This paper simulates the degradation of a 20 m-tall shaft lining in thick topsoil at the vertical depth of 500 m. The simulation was carried out under the similarity theory. Three reduced scale models were prepared from the original structure. The first model was subjected to circumferential load and then cured naturally, the second model was subjected to circumferential load and then soaked in corrosive solution, and the third model was subjected to circumferential and vertical loads and then soaked in corrosive solution. Without changing the circumferential load, vertical load was applied to the three models until they failed. The three models were found to have similar failure patterns: the uniform cracks first appeared at the top and bottom of the outer lining; the concrete of the inner lining cracked, and the upper part of the shaft lining was crushed, showing a diagonal shear failure. Model 1 had greater cracking load and ultimate load than model 2 and model 3. This is because the coupling between vertical and circumferential loads induces micro-cracks between the inner and outer linings, and thus accelerates the corrosion of the RC shaft lining in the corrosive solution

Study on Deterioration Mechanism and Prevention and Curing Techniques of an RC Bunker

In the coal mining industrial environment, the materials of RC bunkers suffer from serious aging problems. The cracking and deterioration of concrete and the corrosion of steel reinforcement lead to a degeneration of structural performance and a decline of structural reliability. In this paper, based on on-site detection and coal mining ground industrial environment, the deterioration characteristics of RC bunkers were tested. The investigation involved the apparent characteristics, carbonized depth, compression strength of concrete, reinforcement distribution and cover thickness, corrosion rate and mechanical properties of reinforcement, decline degree of bunkers, and so on. Then a design review check was done. Combined with the above information, the cause and mechanisms of cracking and damage of the structure were studied; finally, the problems of RC bunkers were targeted and improved. The work provides a reference method for repairing a deteriorated RC bunker in an aggressive service environment

Study on Deterioration Mechanism and Prevention and Curing Techniques of an RC Bunker

In the coal mining industrial environment, the materials of RC bunkers suffer from serious aging problems. The cracking and deterioration of concrete and the corrosion of steel reinforcement lead to a degeneration of structural performance and a decline of structural reliability. In this paper, based on on-site detection and coal mining ground industrial environment, the deterioration characteristics of RC bunkers were tested. The investigation involved the apparent characteristics, carbonized depth, compression strength of concrete, reinforcement distribution and cover thickness, corrosion rate and mechanical properties of reinforcement, decline degree of bunkers, and so on. Then a design review check was done. Combined with the above information, the cause and mechanisms of cracking and damage of the structure were studied; finally, the problems of RC bunkers were targeted and improved. The work provides a reference method for repairing a deteriorated RC bunker in an aggressive service environment

High-Level PM2.5/PM10 Exposure Is Associated With Alterations in the Human Pharyngeal Microbiota Composition

Previous studies showed that high concentration of particulate matter (PM) 2.5 and PM10 carried a large number of bacterial and archaeal species, including pathogens and opportunistic pathogens. In this study, pharyngeal swabs from 83 subjects working in an open air farmer’s market were sampled before and after exposure to smog with PM2.5 and PM10 levels up to 200 and 300 μg/m3, respectively. Their microbiota were investigated using high-throughput sequencing targeting the V3–V4 regions of the 16S rRNA gene. The genus level phylotypes was increased from 649 to 767 in the post-smog pharyngeal microbiota, of which 142 were new and detected only in the post-smog microbiota. The 142 new genera were traced to sources such as soil, marine, feces, sewage sludge, freshwater, hot springs, and saline lakes. The abundance of the genera Streptococcus, Haemophilus, Moraxella, and Staphylococcus increased in the post-smog pharyngeal microbiota. All six alpha diversity indices and principal component analysis showed that the taxonomic composition of the post-smog pharyngeal microbiota was significantly different to that of the pre-smog pharyngeal microbiota. Redundancy analysis showed that the influences of PM2.5/PM10 exposure and smoking on the taxonomic composition of the pharyngeal microbiota were statistically significant (p < 0.001). Two days of exposure to high concentrations of PM2.5/PM10 changed the pharyngeal microbiota profiles, which may lead to an increase in respiratory diseases. Wearing masks could reduce the effect of high-level PM2.5/PM10 exposure on the pharyngeal microbiota

Research on the Structural Characteristics and Evolutionary Process of China’s Tourism Investment Spatial Correlation Network

The paper uses the revised gravity model to measure the intensity of tourism investment spatial correlation, constructs the spatial correlation matrix of tourism investment, and uses the social network method to analyze the structural characteristics and evolutionary process of tourism investment spatial correlation network based on 31 provinces in China from 2000 to 2016. The findings revealed: (1) The spatial correlation quantity of interprovincial tourism investment continues to grow, with Beijing, Jiangsu, Zhejiang, Shanghai, Shandong, and Guangdong at the top of the list. (2) Overall network density and correlation are rising, and the spatial correlation of interprovincial tourism investment is increasingly close. Network hierarchy and network efficiency are decreasing, and network stability has been enhanced. (3) Degree centrality and closeness centrality of each province have shown a significant increase; Beijing, Shandong, Guangdong, Jiangsu, Zhejiang, and Shanghai are the top six and in the center of the network. Most provinces have improved betweenness centrality, Beijing, Guangdong, Shandong, Liaoning, Shaanxi, and Hunan have a strong betweenness centrality with strong intermediary capacity. (4) The core area mainly includes eastern and central provinces, and the periphery areas mainly include western and northeastern provinces. The network connection density of the core and periphery areas shows an increasing trend, while the network linkage density between the core and periphery areas shows a downward trend

Performance issues of barrier systems for landfills: A review

International audienc

Lead adsorption on loess under high ammonium environment

Lead (Pb) is one of the most toxic, hazardous pollutants available in landfill leachate. Loess-amended soil buffers are found suitable and effective in attenuating migration of Pb and the other trace metals. High concentration of ammonium (NH4+ > 1000 mg/l) is also reported in landfill leachate, and therefore, it is essential to investigate the transport of lead under such condition. In this study, the mechanisms and the capacity of loess to adsorb Pb under high NH4+ concentration were investigated. Adsorption isotherm test data were obtained for 25 °C, 35 °C and 45 °C. The maximum adsorption capacity is estimated to be 2101.97 mg/g at 25 °C and 4292.8 mg/g at 45 °C under 1000 mg/l NH4+. The binding sites of Pb on loess are positively related to each other at low temperatures (25–35 °C). The thermodynamic analysis indicates that adsorption process is endothermic and non-spontaneous and the system randomness increases with reaction time. The kinetic test data, fitted with a pseudo-second-order kinetic model and an intraparticle diffusion model, suggests that removal of Pb is driven by both membrane and intraparticle diffusions. The SEM, XRD and FTIR analyses indicate flocculation, precipitations as well as some ion exchange processes, which perhaps combinedly increases adsorption of both NH4+ and Pb in loess. The two kinds of precipitations are involved for the removal of Pb. The precipitations of PbCO3, Pb(OH)2 and PbCO3·2H2O are formed by the reactions between calcite and lead. The other precipitation of white basic salt (Pb2O(NO3)2) is formed by the reactions among Pb2+, NO3− and aqueous ammonia under alkaline environment of loess slurry