A representative example of the problems associated with the excavation and support of tunnels in karst ground is presented. It is a peculiar case in terms of heterogeneity and spatial distribution of zones of poor geotechnical quality, requiring the need to define, preferably in the study phases, adequate site investigation, suitable design procedures, efficient construction techniques and appropriate ground treatment. The difficulties associated with the instability of the karstified ground, and the presence of cavities, wholly or partially filled with soils of low cohesion, are discussed via retrospective analysis. The solutions adopted to solve the problems encountered during the tunnel construction enabled a systematic approach, useful for new construction projects in limestone terrains of medium to high karstification.
Floods are one of the natural hazards that could be most affected by climate change, causing great economic damage and casualties in the world. On December 2019 in Reinosa (Cantabria, Spain), took place one of the worst floods in memory. Implementation of DIRECTIVE 2007/60/EC for the assessment and management of flood risks in Spain enabled the detection of this river basin with a potential significant flood risk via a preliminary flood risk assessment, and flood hazard and flood risk maps were developed. The main objective of this paper is to present a methodology to estimate climate change’s effects on flood hazard and flood risk, with Reinosa as the case study. This river basin is affected by the snow phenomenon, even more sensitive to climate change. Using different climate models, regarding a scenario of comparatively high greenhouse gas emissions (RCP8.5), with daily temperature and precipitation data from years 2007–2070, and comparing results in relative terms, flow rate and flood risk variation due to climate change are estimated. In the specific case of Reinosa, the MRI-CGCM3 model shows that climate change will cause a significant increase of potential affected inhabitants and economic damage due to flood risk. This evaluation enables us to define mitigation actions in terms of cost–benefit analysis and prioritize the ones that should be included in flood risk management plans.
Abstract. This paper proposes a method of valuing the stock of residential buildings in Spain as the first step in assessing possible damage caused to them by natural hazards. For the purposes of the study we had access to the SIOSE (the Spanish Land Use and Cover Information System), a highresolution land-use model, as well as to a report on the financial valuations of this type of building throughout Spain. Using dasymetric disaggregation processes and GIS techniques we developed a geolocalized method of obtaining this information, which was the exposure variable in the general risk assessment formula. Then, with the application over a hazard map, the risk value can be easily obtained. An example of its application is given in a case study that assesses the risk of a landslide in the entire 23 200 km 2 of the Valencia Autonomous Community (NUT2), the results of which are analysed by municipal areas (LAU2) for the years 2005 and 2009.
Flysch materials are one of the most challenging geological materials and often give rise to slope 15 instability problems. Due to its natural heterogeneity, geomechanical characterization of Flysch 16 materials is somewhat difficult. The Spanish Basque Arc Alpine region is a very well-known 17 location for flysch materials. In this paper, an area of approximately 100 km 2 in the region is 18 intensively studied and their flysch materials geomechanically characterized. A total of 33 locations 19 are investigated by a broad geological-geotechnical investigation, involving petrographic analyses, 20 geomechanical stations, boreholes and mechanical laboratory tests. In addition, a slope inventory 21 was carried out to assess the situation in the existing slopes in the area. Characterization of 22 materials is carried out in terms of RQD, RMR and GSI as well as using the Hoek-Brown failure 23 criterion. Different correlations are assessed, establishing their appropriateness for estimating the 24 mechanical parameters of a flysch material rock mass.
Soil nailing is a technique commonly used as temporary or permanent earth retention system in soft soils.Habitually the design of a soil nailing focuses on its performance at failure, computing a safety factor, and thus neglecting ground deformations. In this paper, an analysis and comparison of the convenience of the use of the limit equilibrium method and the finite element method for designing a soil nailing is conducted. The assessment considers both the suitability of an easy and fast design process, and the necessity to take into account issues such as ground deformations to avoid problematic consequences that can arise during their execution phase and service life. For performing the analyses a numerical study of the "Amherst wall", a full-scale soil nailed wall built to be an experimental test in last years of the twentieth century, is carried out.A two-step process for designing soil nailed walls is proposed. The first step involves the use of limit equilibrium methods to define the main parameters. The second step deals with the development of a finite element model to consider ground deformations as well as to determine nail forces. An approach based on the use the Mohr-Coulomb model for simulating materials more similar to granular soils and the Hardening Soil model for simulating materials more similar to cohesive soils is also presented in the paper as an answer to numerically model soil-nailed walls in ground situations where the soil is neither pure cohesive nor pure granular.
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