Documents published in Scipedia

• Site characterization of large hydropower projects

  T. Trick*, K. Kontar, G. Klee, M. Stolz

  ISC2024.

  
  

  Abstract

  Hydropower plays an important role in the context of the energy transition contributing to the reduction of the CO2 emission through a permanent power production as run-of-river scheme as well as for energy storage as pump-storagescheme. Nowadays large hydropower plant designs comprise tunnel, cavern and shaft excavation work known as head race and pressure tunnel or pressure shaft. The powerhouse is often placed within a large underground cavern. The results of a ground investigation phase including the determination of in-situ parameters derived from tests in boreholes drilled from the surface are crucial for a preliminary design of the hydropower plant. Additional in-situ measurements are frequently carried out within an exploratory tunnel to confirm the first predictions and to characterize in detail the mechanical and hydraulic properties of the rock mass. Solexperts portfolio of in-situ well tests comprise the assessment of hydraulic properties vs. depth through hydraulic testing of isolated borehole sections along the borehole axes, the determination of geomechanical parameters like deformation- and Young’s modules through borehole dilatometer tests and rock stress measurements conducting hydraulic mini-frac tests. Plate load tests which use surficial loading are performed in small tunnels or test adits to measure the deformation characteristics of a rock mass on a larger scale.

  Abstract
  Hydropower plays an important role in the context of the energy transition contributing to the reduction of the CO2 emission through a permanent power production as run-of-river [...]

  • 0
  •  read

• Ground Model Workflow with DAARWIN

  I. Jaqués, C. Cano, J. Llopart*, B. Solà, I. Aliguer

  ISC2024.

  
  

  Abstract

  Structural geological models are used to understand and visualize how geological materials are organized below the Earth surface. This technique is crucial in different fields of geomechanics such as mining to identify mineral deposits and to plan mining operations, environmental engineering to assess the contamination of soil and groundwater and to design remediation strategies, and civil engineering to design foundations, tunnels and other underground structures. In this sense, ground models allow the engineer to understand and to visualize the spatial organization of subsurface geological structures and, additionally, it is possible to evaluate the spatial distribution of material properties which is essential in any geomechanical study prior to any project. In this context, SAALG Geomechanics through DAARWIN web platform provides a suitable software tool for the geotechnical engineer to perform the complete ground model workflow. The process starts introducing borehole data from different sources and then, the engineer can visualize and interpret borehole logs, define geomechanical units and assign parameters from in-situ and laboratory tests, as well as assign units’ geometry from geological layers. Finally, the user can feed this information to the system to obtain a 2D cross-section, that can be exported to the commercial Finite Element software PLAXIS and use this PLAXIS model for geotechnical design and more advanced analyses such as Sensitivity analysis and Back-Analysis, which are also implemented in DAARWIN.

  Abstract
  Structural geological models are used to understand and visualize how geological materials are organized below the Earth surface. This technique is crucial in different fields [...]

  • 0
  •  read

• Combined resistivity and seismic measurements along linearly extended earth structures - acquisition and interpretation approaches

  C. Comina*

  ISC2024.

  
  

  Abstract

  Geotechnical parameters of linearly extended earth structures, such as embankments and earth dams, are usually obtained from localized investigations through drilling or penetration tests, commonly time and cost consuming. Non-invasive geophysical investigations may be considered an alternative approach for the geotechnical characterization of these structures, given their surveying speed and their depth and length of investigation. Particularly, new acquisition approaches with the use of appropriate streamer cables could strongly reduce the acquisition times making geophysical surveys ideal for a preliminary screening of these structures. Specifically, resistivity and seismic methods can be adopted given that these two methodologies could offer complementary information with respect to the pore fluid properties (resistivity methods) and the solid skeleton characteristics (seismic methods). Also, through specific correlations, relevant geotechnical parameters for the evaluation of the stability of these structure and its efficiency (i.e. hydraulic conductivity, porosity and others) can be obtained. In this paper a review of the methodologies developed in recent years for data acquisition along linearly extended earth structures is reported with special focus on the use of combined electric and seismic streamer cables. Suggestions with respect to interpretation approaches and data elaboration are also analysed.

  Abstract
  Geotechnical parameters of linearly extended earth structures, such as embankments and earth dams, are usually obtained from localized investigations through drilling or penetration [...]

  • 0
  •  read

• Long-Term ERT Monitoring Data Analysis to Set Slope Instability Attention Thresholds Based on Water Level Fluctuations

  R. Bianchi*, F. Brambilla, A. Hojat, G. Tresoldi, L. Zanzi

  ISC2024.

  
  

  Abstract

  In this paper, we discuss the results of long-term electrical resistivity tomography (ERT) monitoring of a critical slope located on an important high-speed railway gallery. Data were acquired by a customized ERT system from 24 March 2022 until 31 august 2023 and were analysed with the final objective of defining thresholds of attention for resistivity changes derived from water table fluctuations after heavy rainfalls. This helps the authorities in reducing the hydrogeological risk impacts related to potential slope instabilities triggered by extreme meteorological conditions. In order to continuously observe water level changes, five piezometers were also integrated with the ERT monitoring system which is also accompanied by a meteorological station. All datasets were inverted using a time-lapse algorithm that was optimized to minimize artifacts generated by the subsurface complex geology of the site. Due to the long period considered, seasonal temperature corrections on resistivity values were also explored by calibrating a seasonal model of soil temperature versus depth and evaluating the corresponding effects on the resistivity tomographic maps. Finally, the correlation between resistivity values and piezometric levels was studied by producing scatterplot graphs for a selected subzone of the ERT sections. Based on this analysis, a preliminary threshold of attention was defined.

  Abstract
  In this paper, we discuss the results of long-term electrical resistivity tomography (ERT) monitoring of a critical slope located on an important high-speed railway gallery. [...]

  • 0
  •  read

• Early Screening for Improved Management of Geo-risks

  R. Eddies*, R. Wood, M. Staring

  ISC2024.

  
  

  Abstract

  Across several sectors including medicine and agriculture and the extractive industries, availability of early information from screening delivers disproportionate downstream benefit to key stakeholders. With the aim of reducing uncertainty to manage geo-risks in the subsurface, site characterisation for geotechnical engineering is mainly executed following a project owner’s final investment decision (FID) and continues to rely predominantly on conventional investigation techniques that inform both the geotechnical design and construction phases of infrastructure development. However, historical project performance of capital works developments tells us that geo-risks continue to play a role in unwanted engineering business outcomes in the form of schedule and cost overrun associated with earlier cost underestimation. Fundamentally, we recognise that the construction sector would benefit from earlier, faster, and better representation of the subsurface in the top 50 m to 100 m using techniques with a light footprint and low permitting requirements at the earliest stages of project development. We describe an example early-phase screening solution based on adapted ambient noise tomography. Screening at feasibility and planning phases can help to mitigate the impact of human bias arising from epistemic uncertainty in the subsurface and can improve early decision-making where the opportunity to influence project outcome is greatest and at lowest cost. Screening coupled with an optimised conventional intrusive investigation during the execution phase can complete the information set for full project design at considerably reduced levels of subsurface uncertainty leading to improved engineering business outcomes. The industry is encouraged to promptly incorporate the screening philosophy into feasibility and planning activities and into design codes for geotechnical design and construction.

  Abstract
  Across several sectors including medicine and agriculture and the extractive industries, availability of early information from screening delivers disproportionate downstream [...]

  • 0
  •  read

• Interpretation of geotechnical data from an upstream dam for preparation of the site response analysis

  W. Durval Soares de Carvalho, T. Andrade, R. Viola, J. Ccotohuanca, M. Neto, D. Eloi*

  ISC2024.

  
  

  Abstract

  Despite seismic studies in Brazil not being common in the engineering practice as Brazil is a tectonically stable continental region, recent Brazilian regulations require seismic evaluation as supporting studies for decommission and decharacterization projects. Although there exist some critical issues such as limited laboratory data because of sampler processes related to the upstream raised tailings dams, standard tailings and soil foundation characterization, in addition to the field investigation including piezocone (CPTu), seismic piezocone (S-CPTu) and geophysical surveys are the main sources for supporting the characterization of the dynamic properties of the geostructures. This paper presents a brief discussion about the main aspects concerning to the site response analysis carried out for an upstream raised tailings dam (case study), located in Minas Gerais, Brazil. Frequency domain 1-D amplification analyses were conducted by relating local-like representative seismic records and dynamic natural characteristics of the soil profiles to evaluate the seismic response of the case study. Results showed that the maximum accelerations along the profiles are greatly influenced by the presence of the soft foundation tailings layers, and the level of amplification or attenuation is strongly influenced by the tailings layer thickness as well as the frequency content of the applied ground motions. The study pointed out that the site-specific response can support the definition of the appropriate seismic parameters to be used in engineering projects in Brazil.

  Abstract
  Despite seismic studies in Brazil not being common in the engineering practice as Brazil is a tectonically stable continental region, recent Brazilian regulations require [...]

  • 0
  •  read

• New processing methodology of televiewer data for the definition of geotechnical and structural domains

  M. Heredia Bilbao*, R. Sánchez Marín, R. Cano Martín, A. Deu Lozano, P. Martínez Diaz

  ISC2024.

  
  

  Abstract

  Six structural domains were defined using data from acoustic televiewers and oriented boreholes as part of the reopening of the old Aznalcóllar mining site in Sevilla, southern Spain, by Minera Los Frailes (MLF). Additionally, geotechnical subdomains were defined within each structural domain, classifying the subdomains based on geotechnical parameters obtained from the geotechnical logging of boreholes and through correlations. The methodology used to define the domains allows mine design and planning to be done with enough accuracy to determine the underground excavation needs and the systematic methodology. The main source of this new structural information was acoustic borehole image televiewers (ABI) and, on a much minor scale and as a complement for ABI data, oriented boreholes. This paper describes the methodology used for this definition, some of the challenges encountered during the investigation, the main results obtained and the utility of these defined structural domains in the development of the MLF mining site reopening. Additionally, a preliminary approach to an updated methodology in the definition of structural domains with the combination of televiewer data, both acoustic and optical, with data obtained from other downhole probes is also included.

  Abstract
  Six structural domains were defined using data from acoustic televiewers and oriented boreholes as part of the reopening of the old Aznalcóllar mining site in Sevilla, southern [...]

  • 0
  •  read

• Multi-Method Geophysical Assessment of a Shallow Complex Landslide

  M. Rahimi, C. Wood*, S. Rahimi

  ISC2024.

  
  

  Abstract

  This study demonstrates the value of combining multiple non-invasive geophysical methods through a case study at a landslide along Highway 7 near Jasper, Arkansas, USA. Geophysical testing was conducted using Multichannel Analysis of Surface Waves (MASW), Horizontal to Vertical Spectral Ratio (HVSR), and Electrical Resistivity Tomography (ERT) along with select borings. Geophysical testing was aimed to provide a high-resolution and almost continuous image of subsurface conditions (including bedrock depth) for the slide area and to locate the groundwater table/highly saturated zones within the slide area which contribute to the slope movement. MASW revealed a highly variable depth to the weathered bedrock along the observed zone of displacement becoming shallower downslope. ERT detected saturated zones associated with observed seeps and springs in the area which were feeding water into the unstable zone. A low resistivity zone on the north side correlated to wet spots, while south of the highway saturation occurred near the deeper bedrock interface. Additionally, using a grid pattern HVSR approach, a high-resolution image of the shallow and complex bedrock topography was generated across the slide area providing valuable information for the repair design. Overall, the results of the combined geophysical approach provide a high-resolution image of landslide subsurface conditions which is critical for stability analyses and slope repair design. This integrated geophysical approach offers a more sustainable, rapid, and cost-effective solution for comprehensive landslide characterization and slope stability assessment when combined with conventional methods.

  Abstract
  This study demonstrates the value of combining multiple non-invasive geophysical methods through a case study at a landslide along Highway 7 near Jasper, Arkansas, USA. Geophysical [...]

  • 0
  •  read

• Use of Macroseismic Intensity Data to Validate the Ground Motion Prediction Model in Albania

  A. Xhahysa*, M. Ceyhan, N. Kuka, E. Dushi, D. Koxhaj, K. Qoshi

  ISC2024.

  
  

  Abstract

  Macroseismic observations are a valuable tool, that can be used for the verification of site response and attenuation. Hence, in the framework of a bilateral project supported by Central European Investment Fund and with the extensive support of Global Earthquake Model Foundation to update the national seismic hazard model of Albania, intensity maps that contained more than 6000 macroseismic observations for 168 shallow (h

  Abstract
  Macroseismic observations are a valuable tool, that can be used for the verification of site response and attenuation. Hence, in the framework of a bilateral project supported [...]

  • 0
  •  read

• In-Situ Cyclic Direct Shear Tests on Volcanic Soil in the Site of Landslide Due to Earthquake

  A. Sato*, H. Hashimoto, R. Kuwano

  ISC2024.

  
  

  Abstract

  Volcanic pumice soils are widely distributed in many countries. Mechanical properties of those need to be characterized since seismic ground motions can cause serious hazards such as large-scale slope failures and long-distance debris flows. Since volcanic pumice generally retains extremely high porosity and has a sensitive structure, the natural soil structure is easily broken during sampling or transportation. Therefore, it is preferable to conduct in-situ tests without disturbing the original structure of the soil. In this study, an in-situ direct shear test device was developed, and in-situ cyclic direct shear tests were performed on volcanic pumice (Ta-d). This pumice soil is considered to be the main cause of slope failure in Atsuma, Hokkaido, Japan, due to Easten Iburi earthquake in 2018. Laboratory direct shear tests were also conducted using undisturbed sample taken from the site. The results revealed that soil structure significantly affects shear strength. To evaluate the mechanical behavior of such sensitive soils, it is crucial to use specimens with as less disturbed specimens as possible. The newly developed in-situ direct shear test device was used to determine the cyclic shear strength of sensitive volcanic pumice soils.

  Abstract
  Volcanic pumice soils are widely distributed in many countries. Mechanical properties of those need to be characterized since seismic ground motions can cause serious hazards [...]

  • 0
  •  read