NSG2021 2nd Conference on Geophysics for Infrastructure Planning, Monitoring and BIM

We present a case study of a runway construction assessment utilizing ground penetrating radar, heavy weight deflectometry and intrusive data for a proposed horizontal launch spaceport in the United Kingdom. The presentation will showcase an integrated approach of non-destructive and intrusive elements on an existing runway to assess planned use and potential requirements for upgrade the existing infrastructure for new purposes.

The occurrence of large landslides in the slopes of reservoirs may produce a reduction of the water storage capacity and generate water waves which could cause catastrophic flooding if the dam crest is overtopped or breached. The massive and catastrophic rockslide of Vajont reservoir that occurred in 1963 demonstrated the importance of performing detailed geological, geomorphological, hydrogeological and geotechnical investigations in rock masses and soil slopes. Electrical resistivity tomography (ERT) is a non-invasive technology, highly responsive to geological changes that has demonstrated useful to provide the detailed subsurface information required to improve the diagnosis of the slope stability and finding the most suitable zones to fail. The relationships between the electrical resistivity of the high and low-bearing capacity sediments identified in Canelles site highlight the potential of geoelectical methods over other more costly subsurface exploration techniques. The proposed approach show potential to be applied coupled to numerical models to define the boundary conditions up to 100 meters depth with a 5–10 meters resolution and could also help to optimize the required borehole research and monitoring campaign in the initial research stages of landslide characterization.

Maintenance of buried steel infrastructure is an important problem in civil engineering practice. Corrosion, for example, can lead to damage and excessive repair or replacement expenses. Soil corrosivity is one of the main physical factors that determines the corrosion rate of pipelines and other steel infrastructure. Methods that can reliably estimate soil corrosivity by non-invasive and inexpensive means would be of great benefit to the civil engineering community. Soil corrosivity is well-known to depend on multiple interacting physical factors such as moisture content, aeration, pH, organic matter content, microbial activity, etc. However, in most cases a dry and/or sand-dominated soil is electrically resistive and generally less corrosive in comparison with a wet and/or clay-dominated soil characterized by lower bulk resistivity. In this paper, with the objective of evaluating terrestrial CSEM as a potential tool for mapping possible corrosion of buried steel infrastructure, we examine synthetic responses from a terrestrial CSEM layout and report the magnitudes and characteristics of secondary signals that are caused by the presence of a zone of anomalous soil resistivity surrounding a uniform steel pipe. Further consideration of development of a practical slingram-type terrestrial CSEM system for steel infrastructure investigation is recommended.

A geophysical survey was carried out for the detection of anthropogenic constructions under the floor of an old silo of planes made in 1938 in the area of the Old Airport of Elliniko in the frame of its preservation works. GPR and FEM measurements gave GPR sections, 3D presentation of processed GPR data and in-phase component maps that detected various anthropogenic features and information for the foundation of the building.

Monitoring of historic quay walls is key for the early identification of damages that can lead to the failure and collapse of these structures. Currently used methodologies focus on the detection of deformations by high-resolution mapping of the surface of the constructions. Since the collapse of historic quay walls is usually a consequence of internal failure, we analyse the feasibility of utilising seismic methods for imaging the inner structure of quay walls to assess their current state. For this work, we propose to deploy seismic equipment in the water of the canal from a sailing boat to assess and monitor the construction in land. We perform numerical modelling to simulate data for possible scenarios with different acquisition configurations. Our results suggest that seismic methods are practical and viable for the assessment and monitoring of historical quay walls. We show that the overall structure can be imaged, and potential failure mechanism can be promptly identified. Information about the shallow soil structure can also be retrieved. We expect that this method can help the detection of failure mechanisms at an early stage.

Ground Penetrating Radar (GPR) has become one of the popular Non-Destructive Testing (NDT) methods in the field of Geophysics and civil engineering applications. In this context, for applications like concrete rebars assessments, utility networks surveys, the precise localization of embedded cylindrical pipes remains still challenging due to complex geometrical and dielectric characteristics of the stratified medium. In recent years, several hyperbola-centric machines learning based novel techniques have been introduced to accomplish localization of cylindrical objects from the GPR data.

In this paper, performance of Multi-layer perceptron (MLP) based Artificial Neural Networks (ANN) model combined with six statistical travel time features extracted from hyperbola were studied. The model is used to predict the velocity of the stratified medium, depth of cylindrical pipe and radius of the pipe. The approach is based on hyperbola traces emerging from a set of B-scans, whereas the shape of hyperbola highly varies with depth and radius of the pipe as well as the velocity of the medium. Hence, Finite-Difference Time-Domain (FDTD) based 2D numerical tool namely GprMax is used to simulate GPR data. A parametric comparison is also included in the performance analysis of the techniques in terms of relative error estimations against designed parameters.

In any project careful data management is one of the core issues, certainly in long on-going projects. In projects trying to understand the contamination situation the number of different datasets is often large and of many different data types. On a former gasworks facility in a railway yard, in Bräcke in Sweden, many different methods were used, aiming at understanding the spread of primarily tar and PAH contaminants. Some of the methods were geotechnical sounding and sampling, chemical laboratory tests and DCIP. From the start a BIM methodology was chosen to ensure good order of the data also in the longer perspective. The GeoBIM tool was used for data management and for visualization of both data and geomodels using only a web browser, allowing all involved stakeholders to get access to the same information. For allowing not only visual joint interpretation but also automated and advanced comparisons and analyses of the whole data set all data was classified in the CoClass system. CoClass is a hierarchical system allowing computers to sort and analyze data according to a standardized system. The BIM approach applying CoClass on the data managed by the GeoBIM concept clearly improved the ability of analyzing the data.

Case study investigation failure mechanism of a road in Derbyshire (UK). The road is located on a ridge, with steep slopes on either side as well as known historical mineworkings in close vicinity. A multi-disciplinary geophysical survey was executed to identify the potential failure mechanism after cracks in the road surface were observed. The combined interpretation of all techniques provided a detailed image of the subsurface allowing identification of the most likely failure mechanism, which will be used in design of a remediation strategy.

In the Smart Cities perspective, the digital archiving of all geological, geotechnical, geophysical and engineering data of cities should become a useful tool to plan strategies for seismic risk mitigation in terms of urban planning, seismic retrofitting, and management of post-earthquake crises. The CLARA WebGIS geodatabase, developed and released in the framework of CLARA project (CLoud plAtform and smart underground imaging for natural Risk Assessment) move toward this way; it contains 488 georeferenced and downloadable surveys (such as Downholes, Mechanical Surveys, Salcarenite Sampling Stations, MASW, HVNSR, Seismic Refraction Surveys), the geological and geomorphological maps and map of homogeneous microzones from a seismic response perspective and 215 new single-station seismic ambient noise measurements carried out on urban soils and buildings. CLARA WebGIS is the first publicly available database reporting for the whole urban area the spatial distribution of the soil resonance frequencies and the vibrational frequency of the overlying 4043 buildings, along with the probability of soil-building resonance occurrence. All data are accessible, visualizing, querying and downloadable at this link: https://smartcities-matera-clara.imaa.cnr.it/

Fast methods for site characterization and imaging of potentially problematic zones, such as voids and discontinuities, are valuable in geotechnical engineering, to manage risks and meet business objectives. We present a nearly real-time screening tool which uses seismic surface-wave attributes (phase velocity and energy) to produce quantitative indication of lithological variations and other shallow targets. We present the results from an engineering experiment and compare them with a priori information on the site.