Search

To tackle the issue of relying solely on one research approach and the inadequate examination of the elements influencing the soil plug effect during the penetration of pipe piles, this study combines experimental modeling with numerical simulations. Through these approaches, we explore the formation and progression of the soil plug, delving into its underlying mechanisms from both macro and micro viewpoints. The findings indicate that as wall thickness decreases, tube diameter increases, inner wall roughness diminishes, and relative density of sand and soil rises, along with an uptick in pile sinking rates, the soil plug's height within the pile increases. Conversely, the level of soil plug blockage decreases, leading to a weakened soil plug effect. Notably, soil layers characterized by higher hardness on top and lower softness beneath are more susceptible to soil plug occlusion. In contrast, configurations with softer upper layers and harder bases tend to provoke soil plug sliding. Furthermore, the static pressure pile sinking method typically results in a lower soil plug height relative to the hammering technique, making complete occlusion more likely to occur. Overall, the soil plug height is reduced with the static method, exhibiting a more pronounced effect compared to hammering, which is also more likely to lead to complete occlusion. [ABSTRACT FROM AUTHOR]

Vertical plate anchors are an effective technique to enhance the stability of various structures, such as retaining walls and sheet piles. More research has been devoted to their bearing capacity and macroscopically affecting parameters, while less research can be found on their microscopic bearing behavior. In this paper, the microscopic bearing behavior of vertical plate anchors subjected to a horizontal pullout load in sandy soil was investigated with the particle flow code (PFC) based on the model test results. Results show that the larger-sized anchor plates withstand greater soil pressure and affect a broader range of soil during the pullout process. The soil not behind the anchor plate is pressed, and the pressure in front of the anchor plate increases with increasing size. The soil close to the plate anchor suffers larger pressure while the soil far away from the plate anchor is less affected, and the soil is redistributed to a more stable state during the pullout process of the plate anchor. The particles with a long axis distributed in the horizontal direction are the most stable, while those with a long axis distributed in the vertical direction are the most unstable. [ABSTRACT FROM AUTHOR]

To study the contact mechanical characteristics and breakage mechanism of single particle, the particle contact experiment is simulated using the discrete element method. In this paper, to solve the problem that the envelope of the shear strength of the classical model is linear, a nonlinear discrete surface bonded model is introduced by applying nonlinear tangential strength criterion. The new model is compared with the classical model to verify its validity. Then, based on the new model, the particle contact experiment is numerically simulated, and the ball-plane contact breakage mechanism is analysed and discussed from the mesoscopic perspective. The results reveal that the nonlinear discrete interface bonded model can provide shear properties similar to those of actual materials. The numerical result reflects the shear failure of the edge of the conical region and the tensile failure of the whole specimen. Combined with the analysis of the results of stress distribution, velocity field, and force chain distribution, the formation mechanism of the cone core can be obtained. [ABSTRACT FROM AUTHOR]

In the treatment of goafs in traffic engineering, technical problems such as those related to large-volume grouting and the precise control of material properties are often encountered. To address these issues, we developed a new composite material comprising cement-fly ash-modified sodium silicate (C-FA-MS). The setting time, fluidity, unconfined compressive strength, and microstructure were varied for different proportions of cement-sodium silicate (C-S) slurry, cement-fly ash-sodium silicate (C-FA-S) slurry, and C-FA-MS slurry, and their performances were compared and analysed. The experimental results showed that the initial setting time of the slurry was the shortest when both the original sodium silicate volume ratio ( V S ) and modified sodium silicate volume ratio ( V MS ) were 0.2. The final setting time of the C-S and C-FA-S slurries tended to decrease but then increased with decrease in V S , while that of the C-FA-MS slurry increased with lower V MS . The fluidity of the C-FA-S and C-FA-MS slurries decreased with decrease in V S or V MS at different fly ash admixture ratios. The consolidation compressive strength of C-S increased with decreasing V S , while that of C-FA-S showed a considerable increase only when V S decreased from 0.4 to 0.2. Meanwhile, the compressive strength of the C-FA-MS concretions first increased and then decreased with decrease in V MS . Microstructural analysis revealed that there were more cracks in the C-S agglomerate, the fly ash in the C-FA-S agglomerate reduced the relative density of the skeletal structure, and the stronger cross-linking in the C-FA-MS agglomerate improved the strength of the agglomerate. Under the condition of unit grouting volume, the cost of the C-FA-MS slurry was approximately 44.7% and 31.3% lower than that of the C-S and C-FA-S slurries, respectively. The new C-FA-MS material was applied for the treatment of the goaf in the Wu Sizhuang coal mine. Core drilling detection and audiofrequency magnetotelluric survey revealed that the goaf was sufficiently filled. [ABSTRACT FROM AUTHOR]

As the aging continues, China has become the country with the largest older population. In order to ensure the well-being of older adults in their later years, the whole society is increasingly concerned about the mental health of older adults. In 2019, we conduct a questionnaire survey in Shaanxi Province. Stratified random sampling is used to select three representative cities, and 677 samples are selected from the survey results for research. By using the structural equation model, we aim to reveal the mechanism of leisure activities' influence on mental health of the older adults and verify whether social support and perceived stress play a mediating role. The study finds that the older adults' leisure activities have no significant direct impact on mental health. Social support has a significant mediating effect between leisure activities and mental health of the older adults. Leisure activities indirectly affect the mental health of the older adults through social support, and participation in leisure activities can improve the social support of the older adults, thus improving the mental health level of the older adults. Perceived stress plays a significant mediating role between leisure activities and mental health of the older adults. By participating in leisure activities, the perceived stress of the older adults will be reduced, thus improving their mental health. Social support and perceived stress play a sufficient mediating role in the influence of leisure activities on mental health. [ABSTRACT FROM AUTHOR]

Abstract: A p‐n heterojunction photocatalyst BiOI/Bi5O7I has been synthesized via a mixed solvent method at room temperature. The physical and chemical properties of as‐prepared composites were characterized by XRD, SEM, TEM, XPS, UV‐vis DRS, BET and PL. The photocatalytic performance of BiOI/Bi5O7I composite was evaluated by the photocatalytic decomposition of 17α‐ethinylestradiol (EE2) under visible light irradiation. The results revealed that the BiOI/Bi5O7I composite showed enhanced photocatalytic activity compared to pure BiOI and pure Bi5O7I. The mass ratio of BiOI/Bi5O7I and effect of pH value for photocatalytic activity of BiOI/Bi5O7I composite were investigated. Moreover, the photocatalytic mechanism of the degradation process was thoroughly elucidated. The enhanced photocatalytic performance of the BiOI/Bi5O7I composite should be attributed to fabrication of BiOI/Bi5O7I p‐n heterojunction, which was responsible for efficient separation and transfer of electron‐hole pairs. [ABSTRACT FROM AUTHOR]