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Objective At present, a relatively systematic, mature and rapid excavation construction method for the connection passage construction in hard rock stratum has not been formed yet. Due to the small cross-section and limited operating space in the connection passage, construction with the conventional construction method is less efficient with significant construction risks. Therefore, it is necessary to conduct in-depth study on the technology of controlled blasting in the connection passage of metro shield section in hard rock stratum. Method Taking the connection passage in a shield section of Fuzhou Metro Line 4 as a case study, the controlled blasting technology suitable for this project is proposed. According to the engineering characteristics of the project, the calculating parameters required by the maximum single blast charge for a single-section are set up. In addition, based on the distance between the designed connection passage and the objects to be protected, three levels of maximum single-section charges are calculated, and the schemes for blasting hole design, charge structure design and charge blockage are proposed. Six ground settlement measuring points are selected on the ground above the connection passage, and the settlement curves of the six points during construction are obtained to analyze the influence of blasting on ground settlement. Result & Conclusion The measures of reserving protection layers, treating rock masses as rock walls, shallow hole differential blasting, and digital micro-difference initiation being taken in the process of construction, effectively reduce the explosion impact and blasting vibration, achieving the preset goal of safe blasting and rapid excavation.

Walleye (Sander vitreus) is a popular sportfish threatened by overexploitation, habitat destruction, and loss of genetic integrity due to non-native walleye stocking. Previous studies have identified a genetically distinct lineage of walleye in the Mobile River Basin, but further work is needed to assess population structure and introgression among this southern lineage and northern populations. Here we generated 2782 genome-wide single nucleotide polymorphisms (SNPs) to characterize the genetic uniqueness of southern walleye. We also found strong evidence for a historical declining population trend with reduced genetic diversity and effective population size in a southern walleye population of conservation importance. A 68-SNP panel was developed for rapid identification of genetic integrity and hybrid classification among northern and southern walleye, enabling us to identify an anthropogenic hybrid zone resulting from the previous introduction of northern walleye into the Black Warrior River drainage, Alabama. Our results highlight the need for conservation management of southern walleye in the Mobile River Basin, with our 68-SNP assay already being implemented in ongoing stream survey and captive breeding programs. Le dore jaune (Sander vitreus), un poisson prise des pecheurs sportifs, est menace par la surexploitation, la destruction d'habitats et la perte d'integrite genetique causee par l'ensemencement de dores non indigenes. Des etudes anterieures ont cerne la presence d'une lignee de dores distincte sur le plan genetique dans le bassin du fleuve Mobile, mais d'autres travaux sont necessaires pour evaluer la structure des populations et l'introgression entre cette lignee meridionale et les populations septentrionales. Nous avons genere 2782 polymorphismes mononucleotidiques (SNPs) pangenomiques dans le but de caracteriser l'unicite genetique des dores du sud. Nous avons aussi releve des preuves solides d'une tendance demographique passee a la baisse accompagnee de reductions de la diversite genetique et de la taille effective de la population dans une population de dores meridionaux d'importance pour la conservation. Un panneau de 68 SNP a ete mis au point pour la determination rapide de l'integrite genetique et la classification d'hybrides au sein des dores du nord et du sud, nous permettant de cerner une region d'hybrides d'origine anthropique resultant de l'introduction passee de dores septentrionaux dans le bassin versant de la riviere Black Warrior (Alabama). Nos resultats soulignent la necessite de la gestion de la conservation des dores meridionaux dans le bassin du fleuve Mobile, notre epreuve de 68 SNP etant deja deployee dans des programmes en cours de releves dans les cours d'eau et d'elevage en captivite. [Traduit par la Redaction], Introduction Freshwater ecosystems are severely threatened by anthropogenic activities such as overexploitation, water pollution, destruction of habitats, and species invasion (Dudgeon et al. 2006). For exploited freshwater fishes of economic [...]

During the excavation of tunnels, the principal stress orientation changes, with a significant impact on the stress distribution, mechanical properties, and plastic zone evolution of rocks surrounding tunnels, causing severe deformation control, and monitoring problems in the stability of tunnels. Currently, biaxial compression tests were conducted to explore the influence of principal stress orientation on mechanical properties of rocks surrounding tunnels. The analytical solution of stress and the model of plastic zone of rocks considering the principal stress orientation and the distance from the excavation boundary were established to reveal the failure mechanism of surrounding rock under different principal stress orientations. With an increase in the angle between the principal stress orientation and the long axis of tunnel, the maximum tangential stress around the tunnel gradually changed to the minimum horizontal principal stress direction, and its value gradually increased, leading to quicker failure of surrounding rocks, and reducing the strength enhancement effect of the same section size of the tunnel. However, the increase in the angle reduced the damage range and the range of the plastic zone around the tunnel and caused the plastic zone to gradually approach the bottom and roof. The maximum depth of the plastic zone remained parallel to or nearly parallel to the minimum horizontal principal stress direction. When the principal stress orientation was kept constant, the maximum depth of the plastic zone shifted to the minimum horizontal principal stress direction with an increase in the vertical principal stress. [ABSTRACT FROM AUTHOR]