Coupled Hydromechanical Modelling of a Vertical Hydraulic Sealing System Based on the Sandwich Principle

For the shaft sealing of a repository for radioactive waste, a Sandwich sealing system was developed by KIT-CMM consisting of bentonite-based sealing segments (DS) and sand mixture-based equipotential segments (ES). To demonstrate the functionality of the Sandwich sealing system, various laboratory tests (MiniSandwich tests and semi-technical scale experiments) have been carried out before a large-scale experiment has been implemented in situ at the Mont Terri Rock Laboratory (CH). An important coupled process in the Sandwich system is the swelling deformation of the DS while aqueous fluid penetrates into the system. Consequently, the interparticle porosity (effective porosity) of the DS decreases by swelling strain, resulting in a reduction in the permeability of the DS. Pore space of the ES also decreases slightly due to swelling stress in the adjacent DS, which also leads to a reduction in the permeability of the ES. To understand the coupled hydromechanical processes of the Sandwich sealing system, a numerical model was developed to interpret the experimental observations from the MiniSandwich tests and to parameterize different components. A linear swelling model for DS and empirical functions for the swelling deformation-induced permeability change for both DS and ES segments were introduced into the coupled model with Richards’ flow and elastic model. Sensitivity analysis with parameter variations of the most important parameters reduces the uncertainty in the system behavior

Ecological attributes of a tropical river basin vulnerable to the impacts of clustered hydropower developments

The Vu Gia – Thu Bon River Basin in central Vietnam is subject to extensive hydropower development, with eight major and at least 34 minor hydropower installations planned for completion over the next 10 years. This intense clustering of hydropower developments has the potential to impact on aquatic fauna and ecosystems extensively. We sampled freshwater and estuarine fish across the river basin to evaluate the current status of the fish fauna, to determine the extent of zonal and habitat specialisation, to determine the prevalence of migration as a component of life-history strategies, to evaluate the likely magnitude of impacts, and to highlight areas where management intervention is needed and where more extensive study is most urgently required. Given the current high levels of exploitation, the fish fauna appeared surprisingly intact; however, a number of attributes of the fauna, such as the prevalence of migration as a life-history tactic, make this fauna particularly vulnerable to the impacts of hydropower development. Without extensive mitigation, the combinations of habitat alteration in dam and diversion areas and the imposition of a proliferation of barriers to migration will lead to severe population fragmentation, increasing the potential for local extinction, and severely compromise opportunities for recolonisation

Synopsis and taxonomic revision of three genera in the snake tribe Sonorini

Cox, Christian L., Davis Rabosky, Alison R., Holmes, Iris A., Reyes-Velasco, Jacobo, Roelke, Corey E., Smith, Eric N., Flores-Villela, Oscar, McGuire, Jimmy A., Campbell, Jonathan A. (2018): Synopsis and taxonomic revision of three genera in the snake tribe Sonorini. Journal of Natural History 52 (13-16): 945-988, DOI: 10.1080/00222933.2018.1449912, URL: http://dx.doi.org/10.1080/00222933.2018.144991