Based on the laboratory tests on cemented soil under ionic erosion,the factors that influences mechanical properties of cemented soil were analyzed.The results show that erosion caused by ions has evident effects on cemented soil.The higher erosion-resistance of cemented soil corresponds to an optimal proportion of cements.Particular amounts of Na_2SO_4 can improve the strength of cemented soil.The conclusion obtained through the tests can be referred in both design and application of soil-cement in ionic environments.
Based on the safety and durability in the cement soil engineering about the pits anti-seepage and embankment impermeable walls, the experiments on the mechanical properties about the cement soil after infiltrated for some time have been carried out and the influential laws of infiltration time on the cement soil shearing strength, compressive strength and permeability coefficient have been obtained. The test results show that the infiltration time may have influences on mechanical behaviors of cement soil at different levels, and the infiltration time effects on mechanical behaviors of cement soil in the engineering applications and the designs such as impermeable walls should be taken into account; and the shearing strength and compressive strength of cement soil will decrease with the increase of infiltration time so that the curve regression equation about the shearing strength and compressive strength varying with the infiltration time has been established. And the permeability coefficient of cement soil will increase with the increase of infiltration time so that the curve regression equation about the permeability coefficient of cement soil varying with infiltration time has been established, too. The study result is significant and valuable to the safety and the durability of cement soil anti-seepage engineering.
With the development of technology and industry, the problem of global air pollution has become difficult to ignore. We investigated the association between air pollutant concentrations and daily all-cause mortality and stratified the analysis by sex, age, and season. Data for six air pollutants [fine particulate matter (PM 2.5 ), inhalable particles (PM 10 ), nitric dioxide (NO 2 ), sulfur dioxide (SO 2 ), ozone (O 3 ), and carbon monoxide (CO)] and daily mortality rates were collected from 2015 to 2019 in Guangzhou, China. A time-series study using a quasi-Poisson generalized additive model was used to examine the relationships between environmental pollutant concentrations and mortality. Mortality data for 296,939 individuals were included in the analysis. The results showed that an increase of 10 μg/m 3 in the concentrations of PM 2.5 , PM 10 , SO 2 , O 3 , NO 2 , and CO corresponded to 0.84% [95% confidence interval (CI): 0.47, 1.21%], 0.70% (0.44, 0.96%), 3.59% (1.77, 5.43%), 0.21% (0.05, 0.36%), 1.06% (0.70, 1.41%), and 0.05% (0.02, 0.09%), respectively. The effects of the six air pollutants were more significant for male individuals than female individuals, the cool season than the warm season, and people 75 years or older than those younger than 75 years. PM 2.5 , PM 10 , SO 2 , and NO 2 were all associated with neoplasms and circulatory and respiratory diseases. The two-pollutant models found that PM 2.5 , PM 10 , and NO 2 may independently affect the risk of mortality. The results showed that exposure to PM 2.5 , PM 10 and NO 2 may increase the risk of daily all-cause excessive mortality in Guangzhou.
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