A conceptual geological model for offshore wind sites in palaeo ice stream settings: The Utsira Nord site, North Sea

Conceptual geological models of the shallow subsurface which integrate geological and geotechnical information are important for more strategic data acquisition and engineering at offshore wind sites. Utsira Nord is an offshore wind site in the Norwegian North Sea. It covers an area of 23 km x 43 km within the Norwegian Channel palaeo ice stream, with an average water depth of 267 m making the site a candidate for floating offshore wind. The goal of this study is to present a preliminary conceptual geological model for the site, which combines an overview of previous knowledge about the complex ice streaming history of the Norwegian Channel with key observations from high resolution bathymetric data, 2D acoustic data, and shallow cores. Despite limited data, four geotechnical provinces can be defined: 1) exposed glacimarine to marine sediments, 2) buried to exposed subglacial traction till, 3) buried lodgment till and 4) shallowly buried to exposed crystalline bedrock. The model serves as a basis for planning site surveys at Utsira Nord and as a reference for offshore wind sites on other formerly glaciated coasts where palaeo ice stream systems are common, such as the northern coastlines of the United States and the United Kingdom.

Construction of Web-GIS in San'in region for integrating geophysical survey data with geotechnical information

Constructing a database of information on geotechnical information, such as geophysical survey results and borehole data, and sharing it among researchers and practitioners will be useful for the development of subsurface research and the prevention of disasters such as earthquakes and landslides. In earthquake disaster prevention, geotechnical information is particularly important for strong ground motion prediction. The geotechnical information includes analysis results based on geophysical surveys and seismic observations, and borehole data. These databases can be displayed on a map using GIS, and the existing analysis results can be checked sequentially. This will allow us to consider new observation plans and to improve the efficiency and accuracy of the analysis of the subsurface structure model. In this study, a database of geotechnical information was constructed for the San-in region. The database of geotechnical information includes the results of microtremor and gravity survey, analysis of ground structure by seismic observation, and borehole data in Tottori and Shimane prefectures. In addition, we constructed a system to display the constructed database on a map in a web browser (Web-GIS). For the base system of the GIS, Leaflet, a Java Script library, was used to display the prepared database of geotechnical information using the GSI tiled map as the base map. The developed database and GIS system will be used to researchers and the public in the future.

3D Modelling of a Hydrothermal System in a Densely Populated Urban Area – the Alfama Springs Case-Study (Lisbon, Portugal)

In the XIX th century, the Alfama thermal and non-thermal springs were qualified as “mineral water” by the governmental authorities. But after a few years of legal usage in balneotherapy, all of them knew a constant and progressive definitive decay, and the last balneotherapic facility was abandoned and sealed more than 40 years ago. Despite their significant influence in Lisbon life along the History, their exact location is now only approximate. Nowadays, they are all buried below the city buildings, squares and streets. Since some of the Alfama springs reached temperatures up to 34 °C, groundwater from these springs can be used in a new modern spa or in district heating facilities in the heart of the city of Lisbon, if adequately recovered. But priorly, to carry out this task, a global understanding of the conceptual hydrogeological model is needed. However, the springs are located in a densely urbanized and touristic area, where geological outcrops are no longer visible and old springs’ location is unknown; therefore, a review of geological and hydrogeological data and geotechnical reports was carried out to plan further research works. Adding to this exhaustive bibliographic review and data integration, new seismic reflection data were acquired, and brought some new insights on the groundwater circulation system. All these data interpretations contributed significantly to achieve a better knowledge on the main and secondary faults that control the occurrence of Alfama springs and framed them into the complex regional tectonic framework. The entire set of historical hydrogeological data, geotechnical information, and newly acquired data lead to a reasonably accurate and data supported 3D geological and hydrogeological conceptual model of the deep groundwater flow circuit. This paper describes the research work that led to the conception of the local and complex 3D hydrogeological model of the Alfama springs system. With this 3D model, the best location for a dipped well can now be envisaged, keeping in mind the narrow local urban constraints, possible future users, and stakeholders.

Geotechnical Property Modeling and Construction Safety Zoning Based on GIS and BIM Integration

The increase in population and urbanization needs attention towards intense construction activities to meet the social and economic needs. Soil excavation is a primary step in every construction project that needs proper surface and subsurface information modeling since it is vulnerable to construction hazards. Geographic information system (GIS) provides significant information about the existing contextual surface information while building information modeling (BIM) gives information about the asset in a great detail that has been integrated into the construction industry for many applications. However, the integration of BIM and GIS for the subsurface geotechnical property modeling and classification into zones has been rarely explored. This paper presents the integration of BIM and GIS for modeling geotechnical properties and safe construction zones based on soil type. The use of open standard IFC classes such as IfcBorehole, IfcGeoslice, and IfcGeomodel enhances the collaboration and allows the exchange of geotechnical information among different stakeholders. The method has been applied to the in-situ and laboratory test dataset of the Peshawar, region, to validate the proof of concept. The results demonstrate that the proposed method successfully integrates BIM and GIS providing a three-dimensional surface and subsurface model. The 3D digital geotechnical model has excellent potential to provide information about soil type, properties, depth, and volume of each available soil layer that can be used by construction planners and managers to identify best construction practices and plan for safe construction.

Failure Mechanism and Kinematics of the Deadly September 28th 2016 Sucun Landslide, Suichang, Zhejiang, China

The formation and dynamic process analysis of the rockslide avalanche in mountainous areas are one of the consequences of the catastrophic accident. Such loose accumulation in upslope may saturate partially or completely when the stability of their accumulation dam is distributed or affected by rainfall. We present a case study with respect to the southern Wuyi Mountain located in eastern China, where the wet and rainy climate has led to dozens of similar rockslide hazards. The purpose of this paper was to analyse the mechanism and dynamic characteristics of the rockslide influenced by the same geological conditions and to predict the outburst susceptibility of similar landslides in the future. Detail field surveys, 3D laser scanning, and high-density electrical methods were used to collect the geotechnical information of the complex landslide, to identify the discontinuity between the landslide material and the bedrock, and to investigate the deformation characterization and dynamic process of the rockslide. Based on remote sensing interpretation and field investigation of the deformation process of a landslide in different times and different parts, the background, mechanism, and cause of the landslide were demonstrated. The landslide is controlled by the characteristics of the geological structure, including collapse, circular sliding, plane sliding, and debris flow. In addition, there are rock avalanches on the rear edge of the slope subjected to the combined action of rainfall and gravity. Moreover, there are some resistance anomaly areas of the aquifer and soil between 2 and 50 m where the resistivity is less than 120 ohm-m, and they were deduced to be full of water, confirming a “bathtub” type structure. The mechanism of the catastrophic landslide was a combination of the upper pushing deformation induced by rainfall line uplift and rotational; due to the ancient landslide reactivation in the transposition area, the velocity of the rockslide reached 40.11 m/s.