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Deterioration law of intermittent jointed sandstone mechanical properties under water-rock interaction

100%

Chen G. , Li Y. , Li T. , Zhang G.

Acta Geophysica

2022

tom Vol. 70, no 4

1923--1935

In water-rich mines, water conservancy, and hydropower projects, the rock mass is immersed in water for a long time, which leads to changes in its mechanical properties and affects the safety and stability of the engineering rock mass. Based on the long-term immersion of rock mass with intermittent joints by water, uniaxial compression tests were carried out on prefabricated intermittent jointed sandstone with five inclinations (0°, 30°, 45°, 60°, 90°) and three connectivity ratios (0.25, 0.50, 0.75) under different immersion times to study sandstone with intermittent joints’ mechanical response and deterioration mechanism. The research shows that: (1) With the increase of the joint inclination, the compressive strength and elastic modulus of the sandstone with intermittent joints first decreased and then increased, showing a U-shaped distribution. The compressive strength and elasticity of the sample with an inclination of 60° reach the minimum value; at the initial stage of immersion, the deterioration effect of the sample is more significant, and the deterioration effect decreases gradually with the increase in immersion time; in the initial stage of water immersion, the deterioration effect of the sample is more significant, and with the increase of the immersion time, the deterioration effect gradually weakens. (2) Immersion time and joint inclination have a great influence on the included angle, number, and mode of failure cracks. With the increase in immersion time, the plastic characteristics of the sample increase obviously, showing the characteristics of loose and weak; with the increase in joint inclination, the failure mode of the sample gradually changes from tension failure to tension shear failure, and tension failure. The influence degree of joints on failure is weak-induction-control-induction. (3) Under the water–rock action, the cement between mineral particles of the sample is gradually dissolved, the cementation of mineral particles is weakened, and the mineral particles develop into layered and fake structure, which gradually evolves from dense structure to porous loose structure. (4) The deterioration mechanism of the mechanical properties of the sandstone with intermittent joints under the water–rock action was analyzed from the perspectives of physics, chemistry, and mechanics. The deterioration of the mechanical properties of the sample is a process of gradual accumulation of damage.

Texture Representation and Application of Colored Spun Fabric Using Uniform Three-Structure Descriptor

88%

Li Y. , Muli L. , Liu J. , Yang Y. , Gong X.

tom Vol. 22, no. 4

477--487

The local binary pattern (LBP) and its variants have shown their effectiveness in texture images representation. However, most of these LBP methods only focus on the histogram of LBP patterns, ignoring the spatial contextual information among them. In this paper, a uniform three-structure descriptor method was proposed by using three different encoding methods so as to obtain the local spatial contextual information for characterizing the nonuniform texture on the surface of colored spun fabrics. The testing results of 180 samples with 18 different color schemes indicate that the established texture representation model can accurately express the nonuniform texture structure of colored spun fabrics. In addition, the overall correlation index between texture features and sample parameters is 0.027 and 0.024, respectively. When compared with the LBP and its variants, the proposed method obtains a higher representational ability, and simultaneously owns a shorter time complexity. At the same time, the algorithm proposed in this paper enjoys ideal effectiveness and universality for fabric image retrieval. The mean Average Precision (mAP) of the first group of samples is 86.2%; in the second group of samples, the mAP of the sample with low twist coefficient is 89.6%, while the mAP of the sample with high twist coefficient is 88.5%.

Characteristics and metal leachability of natural contaminated soil under acid rain scenarios

63%

Tan W. , Li Y. , Ding L. , Wang Y. , Li J. , Deng Q. , Guo F. , Xiao X.

tom Vol. 45, no. 2

91--98

Contamination of soil with heavy metals has become a worldwide environmental problem, and receives great attention. In this study, we aim to investigate soil pollution level affected by an industrial district nearby. The total amount of typical heavy metals in the soils (Hengyang Songmu Industrial Park, Hunan Province, China) was analyzed. In addition, the fraction analysis and laboratory simulation leaching via different pH rainwater was carried out to study the migration and transformation of heavy metals. The main results show that the contents of Cu, Zn, Pb, Cr and Cd in the samples were higher than the soil background values in Hunan Province. The heavy metals forms, analyzed by sequential extraction method, show that the proportion of the unstable form of Cd, Zn and Pb was more than 50%. Igeo values indicate that the heavy metal pollution degree of soil sample #5 at the investigated area is recorded in the order of Cd(6.42), Zn(2.28), Cu(1.82), Pb(1.63), and Cr(0.37). Cu, Zn, Pb, Cr and Cd in this area could pose a potential leaching risk to the environment which may affect the food chain and constitute a threat to human health. It would be necessary to take steps to stabilize and monitor the heavy metals in soil.