Documents published in Scipedia

• Evaluation of the challenges present in the obtaining, processing and interpreting useful data from offshore seismic cone penetration testing

  T. Masters, I. Cazarez*, N. Tejani, G. Verbeek

  ISC2024.

  
  

  Abstract

  The Seismic Cone Penetration Test (SCPT) is an essential tool for establishing in-situ shear wave velocity (𝑣𝑠), which is then used to establish profiles of Small Strain Shear Modulus (𝐺𝑚𝑎𝑥), a direct input parameter to the design of offshore wind turbine foundations. Performance of SCPT offshore presents greater challenges than on land and each offshore site investigation contractor uses their own different non-standard equipment to try to address these challenges. This contributes to the multiple areas of uncertainty in the assessment of wave arrival time and distance, which can result in less reliable data sets. Additionally, a variety of data processing and interpretation methods are used across the industry, the benefits and limitations of which must be understood if one is to specify, plan or undertake such testing. The authors provide a review of methods of acquiring data, the equipment required and the different processing and interpretation methods available, specifically comparing true interval straight ray analyses with pseudo interval true ray path analyses and the different processing steps which can be taken to increase reliability in datasets.

  Abstract
  The Seismic Cone Penetration Test (SCPT) is an essential tool for establishing in-situ shear wave velocity (𝑣𝑠), which is then used to establish profiles of [...]

  • 0
  •  read

• Development of a 3D Ground Model for an Offshore Wind Farm with Complex Interlayering of Silty Soils

  X. Peng*, Y. Gao, Y. Du, D. Wang, P. Li, X. Li, Y. Zhang

  ISC2024.

  
  

  Abstract

  Three-dimensional (3D) ground models enable the visualization of complex subsurface conditions in offshore wind farms, which aid engineers in understanding the spatial morphologies and interrelations of different soil layers. Due to the large areas of offshore wind farms, 3D ground models established solely based on limited geotechnical data (e.g., boreholes and cone penetration tests) might lack the required accuracy. Geophysical data, particularly seismic profile data, is capable of revealing stratigraphic information and can be obtained at a relatively low cost. This study presents a case study in which a 3D ground model for an offshore wind farm located off the Southern China coast is developed through the integration of geotechnical and geophysical data. The wind farm features complex interlayering of silty materials below the soft Holocene marine deposits due to repeated sea level changes during the Quaternary period. This created significant challenges for developing a reliable ground model. In this paper, the challenges that were faced and solutions that were applied in this project are presented and discussed.

  Abstract
  Three-dimensional (3D) ground models enable the visualization of complex subsurface conditions in offshore wind farms, which aid engineers in understanding the spatial morphologies [...]

  • 0
  •  read

• Exploration for Wave Propagation Around Ground Loosening Using Discrete Element Method

  K. Kuwashiro*, M. Otsubo, R. Kuwano

  ISC2024.

  
  

  Abstract

  Ground loosening and subsurface cavities potentially cause ground cave-ins, even if they are deep in the ground. Loosened soil and cavities, for example, formed by shield tunnel excavation or breakage of underground pipes occur frequently. Recently, ground-penetrating radar method has been utilized to detect subsurface cavities, and studies such as dynamic wave surveys have been considered. However, these methods assume that cavities several meters deep can be detected by surface-based surveys, and do not target loosened soil directly above a deep tunnel. This contribution is a fundamental study aimed at detecting loosening depth in the ground, with the goal of measuring dynamic waves from the inside of a tunnel. To understand wave propagation and particle-scale response around loosened sandy soil, this study adopts the discrete element method (DEM) using cohesionless spherical particles. A series of DEM simulations are performed to understand how dynamic waves propagate or reflect around loosened sandy soil in comparison with dense ground without loosening.

  Abstract
  Ground loosening and subsurface cavities potentially cause ground cave-ins, even if they are deep in the ground. Loosened soil and cavities, for example, formed by shield [...]

  • 0
  •  read

• Statistical analysis between intensity measures at the bedrock and the seismic response of the site

  A. Avellaneda, Y. Vargas-Alzate*, J. Vaunat, A. Di Mariano, A. Zapata-Franco

  ISC2024.

  
  

  Abstract

  This research work focuses on the seismic response of sites considering uncertainties. There are two main objectives. The first consists on assessing the effectiveness of intensity measures to predict properties of the expected wave motion at the surface. According to recent studies, special attention has been paid to predicting velocity-related ground motion parameters, which are highly correlated to the nonlinear dynamic response of civil infrastructures. The second objective is to analyse the evolution of the dynamic properties of the soil because of seismic waves. The main database of acceleration records in Colombia has been analysed, as well as three soil profiles that correspond to real building projects designed and built in the same country. From this information, a series of site seismic response analyses have been carried out using the equivalent linear method. Then, using statistical regression techniques, the correlation between input variables (parameters of the seismic records) and output results (intensity measures at the surface, maximum soil deformations, damping and shear wave velocity variations) have been evaluated. The paper shows that a series of highly correlated variables can be used to incorporate, in a simplified manner, site effects in the analysis of seismic risk at a regional scale.

  Abstract
  This research work focuses on the seismic response of sites considering uncertainties. There are two main objectives. The first consists on assessing the effectiveness of [...]

  • 0
  •  read

• Field Site Characterization of a Coastal Aeolian Sandy Subgrade for a Proposed Tank Farm Site in Peru

  J. Zamora*, M. Pando

  ISC2024.

  
  

  Abstract

  Analysis of shallow foundations, pavements, and slabs-on-grade requires adequate site characterization of the nearsurface soils. Key properties required for the above are the soil stiffness and its nonlinearity. In this paper, we present the results of field site characterization at a coastal aeolian sand site located in Villa El Salvador, Peru, where large storage tanks are being proposed to be supported on concrete slabs-on-grade and shallow ring foundations. The site characterization included standard penetration tests (SPT), dynamic cone penetrometer (DCP) tests, lightweight deflectometer (LWD) testing, and geophysical tests such as multichannel analysis of surface waves (MASW), seismic refraction, and electrical resistivity. The paper focuses on estimating elastic soil stiffness (Es) values on the main bearing layer of the tanks. The observed large variability of Es estimates was associated with inherent soil variability at the site, the in-situ test method, and the use of empirical correlations between Es and different in-situ tests. Good elastic soil stiffness estimates for the bearing layer (Upper SP sand) were required to make reliable estimates of absolute and differential settlements for the tanks. Due to soil nonlinearity, the elastic stiffness values from the different methods decreased with increasing levels of shear strains associated with each test. Accordingly, the highest elastic stiffness values were from the MASW, followed by the LWD, and the lowest from SPT-based correlations. The soil stiffness estimates using SPT-based correlations yielded the highest variability due to the high uncertainty and low confidence of the empirical correlations between Es and SPT field values.

  Abstract
  Analysis of shallow foundations, pavements, and slabs-on-grade requires adequate site characterization of the nearsurface soils. Key properties required for the above are [...]

  • 0
  •  read

• Dynamic characterization of alluvial deposits through geophysical anda specialized test in Floridablanca santander

  C. Buenahora Ballesteros*, D. Galvis Ballesteros, N. Amaya Perez, A. Martínez, L. Ortiz, M. Silva

  ISC2024.

  
  

  Abstract

  The Metropolitan Area of Bucaramanga is located within one of the three seismic nests in the world and therefore presents a high seismic and geotechnical threat (INGEOMINAS, 2001), therefore certain zones, especially those with alluvial and colluvial deposits, have limitations for the development of infrastructure projects, unless a threat assessment is carried out that indicates otherwise or, in its absence, it is reduced to low levels with stabilization works. The thicknesses of these deposits vary from a few meters to two hundred meters and their definition and dynamic behavior (damping coefficient and terrain degradation curves), would allow analysis with special non-linear constitutive models to better understand their response to a possible earthquake and to ensure the stability of the structures and even an optimization based on a possible lower spectrum. A new two-tower housing project of up to 36 stories high is a perfect scenario to carry out a local seismic response study and perhaps transform the way future projects are designed. It should be noted that, given the acceptable stiffness and granular composition of the soils, it is difficult to take unaltered samples and the Colombian NSR-10 standard does not require local behavior studies and therefore its study has not been properly established. It is sought through geophysical tests and laboratory tests such as triaxial, resonant column and bender element to perform such characterization and to perform soil modeling that allows the calculation engineer to have the appropriate inputs for their analysis.

  Abstract
  The Metropolitan Area of Bucaramanga is located within one of the three seismic nests in the world and therefore presents a high seismic and geotechnical threat (INGEOMINAS, [...]

  • 0
  •  read

• Calculation of heights for local datum points of tide gauges in Albania referred to the average sea level and albageo program

  B. Sina*, G. Hasko, E. Blloshmi

  ISC2024.

  
  

  Abstract

  The accurate measurement and monitoring of sea levels are of paramount importance, especially for coastal regions like Albania, where sea level changes can have significant impacts on various aspects of life, including coastal infrastructure, ecosystems, and human settlements. This abstract provides an in-depth overview of a study focused on the calculation of heights of local datum points at tide gauges in Albania with reference to the average sea level, using the ALBAGEO3 program. Tide gauges play a crucial role in understanding the dynamic nature of sea levels. These instruments measure the height of the sea surface relative to a reference point, which is typically known as the local datum. The calculation of heights of local datum points is crucial for several reasons. Firstly, it provides insights into the relative sea level changes at different locations in Albania. It allows for the identification of areas that may be more vulnerable to such events, enabling betterinformed decision-making in terms of coastal management and disaster preparedness. Furthermore, accurate knowledge of local datum heights is essential for navigation and maritime activities. It ensures that nautical charts are up to date and that ships can safely navigate Albanian waters without the risk of running aground or encountering obstacles related to sea level changes. In summary, the study on the calculation of heights of local datum points at tide gauges in Albania, utilizing the ALBAGEO3 program, plays a pivotal role in advancing our understanding of sea level variations in this coastal nation. The accurate and reliable data generated through this research benefits not only the scientific community but also provides actionable insights for policymakers, urban planners, and other stakeholders involved in the sustainable development and protection of Albania's coastal areas.

  Abstract
  The accurate measurement and monitoring of sea levels are of paramount importance, especially for coastal regions like Albania, where sea level changes can have significant [...]

  • 0
  •  read

• Spatio-Temporal Prediction Surface Displacement in Urban Underground Excavation: A Case Study in Seville"

  M. Bahri*, E. Mascort-Albea, R. Romero, C. Soriano Cuesta, A. Jaramillo Morilla

  ISC2024.

  
  

  Abstract

  One of the primary challenges in excavating underground in urban areas is controlling and mitigating ground surface displacement caused by Earth Pressure Balance (EPB) tunneling. It is crucial to avoid damaging historical monuments and buildings in these areas. This paper presents a new method for predicting the surface displacement caused by EPB in Seville. A spatiotemporal dataset was generated for this study using numerical simulation in FLAC3D. The simulation replicates the excavation process of the Seville metro line in real-time, and records the surface displacements at selected points in the dataset. The last 20-time steps of excavation are predicted, and the first 80-time steps are chosen for training and tuning hyperparameters, as the dataset is spatiotemporal. A recurrent neural network (RNN) is used to detect and predict patterns between surface displacement and input features at different time steps and locations of the excavation. After fine-tuning the RNN, the model achieved an accuracy of 0.91 for the evaluated R-squared (R2), indicating its practicality for real-time prediction of surface displacement in underground excavations in Seville. The model's performance can be further improved with a larger data range. By deploying it as a hazard detector, the model can issue a warning if the ground displacement exceeds the limit, thereby preventing potential hazards. This approach can help control and mitigate potential hazards in underground excavations in historical cities.

  Abstract
  One of the primary challenges in excavating underground in urban areas is controlling and mitigating ground surface displacement caused by Earth Pressure Balance (EPB) tunneling. [...]

  • 0
  •  read

• Geotechnical monitoring at the speed of light: New insights from distributed acoustic sensing

  S. Ouellet*, J. Dettmer, M. Lato, R. Crickmore, B. Dashwood, J. Chambers, A. Chavarria

  ISC2024.

  
  

  Abstract

  Recent advances in distributed fibre optic sensing enable new opportunities in geotechnical monitoring and characterization. Distributed acoustic sensing (DAS) is a distributed fibre optic sensing technology relying on Rayleigh backscattering of light to detect and locate disturbances in near real-time along tens of kilometres of fibre optic cable. The dynamic strain sensing capabilities of DAS have prompted numerous research initiatives from the seismology community over the past decade. Although research on DAS for seismic applications is well established, studies on DAS for geotechnical monitoring applications are less common. Here, we present a summary of two recent case studies involving DAS for geotechnical monitoring. The first study considers a slow-moving landslide where DAS data were acquired over a three-day period of rainfall. The DAS aseismic strain and strain-rate data support the interpretation of the triggering and retrogression failure mechanism of the landslide. The second study considers an active mine site in northern Canada. Data were acquired from a cable installed ~1m below a tailings dam crest. Passive seismic interferometry was applied to DAS data to infer changes in seismic velocities in the uppermost several meters of the subsurface. These findings represent a first step towards advancing continuous monitoring techniques with fiber optic sensing technologies. However, further research is needed to improve our understanding of DAS performance for geotechnical monitoring applications over longer-term periods.

  Abstract
  Recent advances in distributed fibre optic sensing enable new opportunities in geotechnical monitoring and characterization. Distributed acoustic sensing (DAS) is a distributed [...]

  • 0
  •  read

• Effects of storage time on sample quality in Ballina clay

  K. Ouyang, J. Pineda*

  ISC2024.

  
  

  Abstract

  This paper explores the effects of the storage time on the engineering properties of Ballina clay, an estuarine silty clay that represents the soft soil deposits encountered along the eastern and southern Australian coastlines, which serves as foundation material for most of the country’s transport and energy infrastructure. An experimental program was carried out to evaluate the variation in soil compressibility and soil shear strength for tube specimens retrieved with an open sampler (Shelby tube) as well as an Osterberg fixed-piston sampler. Mechanical parameters obtained from tests performed immediately after sampling are compared against those measured over a period of 1 year, to assess the influence of the storage time. Results indicate that long-term storage has small influence on the quality of Ballina clay specimens in comparison with the mechanical disturbance caused during tube penetration and extraction, which is controlled by the sampler type.

  Abstract
  This paper explores the effects of the storage time on the engineering properties of Ballina clay, an estuarine silty clay that represents the soft soil deposits encountered [...]

  • 0
  •  read