Documents published in Scipedia

• Drainage Effects in a Dilatant Carbonate Silty Sand

  F. Farzaneganpour, F. Bransby*, C. O’Loughlin

  ISC2024.

  
  

  Abstract

  This paper presents and discusses results from a series of cone, vane and footing tests in a carbonate silty sand, conducted in a geotechnical centrifuge, that investigate how drainage effects scale with the diameter of the device/foundation. The tests involved different penetration and rotational velocities to quantify how velocity influences the drainage response, and in turn, the magnitude of the deduced soil strength. Cone and foundation resistance, and the shear stress measured in the vane tests, were seen to increase with increasing penetration/rotational velocity, consistent with a dilatant shearing response. The collective dataset is interpreted within the ‘drainage backbone curve’ framework, with an attempt made to understand how drainage path length varies for the different devices and is affected by stress level.

  Abstract
  This paper presents and discusses results from a series of cone, vane and footing tests in a carbonate silty sand, conducted in a geotechnical centrifuge, that investigate [...]

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• Site characterisation, data management and data integration for submarine cable landing Projects

  V. Terente, D. HIxman, H. Waterson, M. Wetton*

  ISC2024.

  
  

  Abstract

  There is an increased need for submarine cable infrastructure across the world to serve the offshore wind power industry and the expansion of the submarine interconnectors and telecommunication networks. Cable landfall projects are complex as land, intertidal, nearshore, and offshore environments all coverage, creating an array of dynamic processes, constraints, hazards, and engineering challenges that an asset may face over its lifespan. Robust site characterisation and ground modelling is key for the success of these projects, to allow for the effective, safe, and economical site selection, design, installation, and operation of an asset. In order to accomplish this, the integration of engineering and geoscientific datasets, obtained through several data sources and survey techniques is required; as well as collaboration and integration between multiple technical disciplines. This paper lists the key stages, techniques, and sources available for obtaining the required data. We then consider how the data can be managed and integrated to obtain a holistic ground model for use in the design, construction, and operation of the asset. We discuss the value these models can provide throughout the lifecycle of landfall projects.

  Abstract
  There is an increased need for submarine cable infrastructure across the world to serve the offshore wind power industry and the expansion of the submarine interconnectors [...]

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• Nanotechnology Applied for Soil Stabilization - a Survey

  B. de Córdova Caetani*, H. Nierwinski, B. Karasiak Meneguz

  ISC2024.

  
  

  Abstract

  The technical and constructive challenges inherent to the execution of engineering works on problematic soils require a continuous development or improvement of the techniques and methods used to investigate the soils’ behavior and to design and evaluate the performance of these works. Soil stabilization is one of the most used techniques to improve the mechanical behavior of the soil. In addition to classic soil stabilization methods, nanotechnology is increasingly being used for various purposes, such as introducing nanoparticles of different compounds into the soil mixture or in the field of geosynthetics for fiber treatment. Although they do not have cementing properties, nanoparticles improve mechanical properties, thermal stability, and physicochemical behavior. Studies carried out with different types of soil show that introducing nanoparticles into the soil-cement matrix reduces the space between particles and provides a more robust and rigid soil skeleton. Considering this, it improves the material's resistance properties and reduces cement consumption, contributing to sustainability. The literature review presents research that evaluates different nanoparticles applied to soil mixtures and their influence on the final product. This paper reviews the state of the art of several studies showing that nanotechnology is a successful solution that can be used in soil stabilization because of its capacity to improve, for example, shear strength, unconfined compression strength, and the elastic modulus of soil. The research gap and prospects for using nanotechnology for soil stabilization are also exposed.

  Abstract
  The technical and constructive challenges inherent to the execution of engineering works on problematic soils require a continuous development or improvement of the techniques [...]

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• Organic Soil Identification by CPTu

  C. Champagne*, E. Peuse, R. Hryciw, E. Garcia

  ISC2024.

  
  

  Abstract

  A soil behavior type (SBT) chart was developed to more reliably identify organic soil deposits at sites in the state of Michigan based on piezocone (CPTu) data. Organic soils are often highly compressible organic silts, clays, and peats. Many of these soils are fluvial with high void ratios and large compressibilities. These soils are typically removed prior to the construction of roadways and shallow bridge foundations due to the risk of excessive settlement. CPTu soundings were strategically performed alongside companion soil borings in which standard penetration testing (SPT) was performed and from which split-spoon and Shelby tube samples were recovered and tested. While many of the widely used SBT charts characterize the inorganic soils with reasonable agreement to the soil descriptions presented in the soil boring logs, the organic soils are often mischaracterized as inorganic clays. A hybrid SBT approach was therefore developed that yields more accurate characterization of the organic soils. The inorganic soils are reliably characterized by plotting the normalized tip resistance versus the normalized friction ratio. This SBT approach, however, ignores the valuable piezometric data provided by the CPTu. For organic soils, piezometric data helps to more reliably distinguish between inorganic clays and organic soils. As such, a screening tool was implemented to flag likely organic soils by plotting a parameter that accounts for both the tip resistance and pore pressure versus the normalized friction ratio before characterizing the likely-inorganic soils using existing approaches.

  Abstract
  A soil behavior type (SBT) chart was developed to more reliably identify organic soil deposits at sites in the state of Michigan based on piezocone (CPTu) data. Organic soils [...]

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• Challenges in Site Characterization and Work Verification of Compacted Crushable Sands

  P. Schober, J. Redgers, V. Bhushan*

  ISC2024.

  
  

  Abstract

  During reclamation projects huge amounts of sands are dredged and placed to create artificial land. To increase the density and therefore to mitigate the potential risk of liquefaction as well as to increase the stiffness and internal friction angle of the sand, it is often necessary to compact the reclaimed sand. The performance targets for compaction are frequently verified by means of achieving a particular relative density that is generally correlated from Cone Penetration Tests (CPT). For many reclamation projects, due to the non-availability of local quartz or silica sands, crushable, carbonate or calcareous sands are used. In these crushable sands, due to the very high stress concertation below the CPT cone, the particles tend to crush. The well-known published correlations between the relative density and cone resistance are established for non-crushable silica sands and are thus not applicable to these crushable sands and can result in over treatment costing time and money. Usually, the crushing effect is quantified in a calibration chamber test and a project specific correction factor is introduced. Alternatively, to avoid this costly and time-consuming procedure the use of measuring the shear wave velocity with seismic CPTs (SCPT) is possible. The Cyclic Stress Ratio (CSR) for liquefaction analysis and other soil parameters required for the design verification can be correlated without being influenced by the crushing of particles due to the non-invasive procedure. This paper gives an overview of the common practice for work verification in crushable sand and shows an approach to determine the required compaction parameters using seismic CPTs.

  Abstract
  During reclamation projects huge amounts of sands are dredged and placed to create artificial land. To increase the density and therefore to mitigate the potential risk of [...]

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• Experience of in situ geotechnical tests and their interpretation in organic soils and peat

  M. Long*, G. Tucker, C. Thrane Leth

  ISC2024.

  
  

  Abstract

  This paper reviews the use of piezocone (CPTU) testing to characterise and identify peats and organic soils. Examples of data for peat sites from several countries are given, including some experience of the use of T-bar and piezoball penetrometers in peat. These “full flow” devices show smoother resistance profiles than the equivalent from the CPTU and are perhaps representative of the peat mass with a reduced fibre effect. In CPTU tests, organic soils and peat are often characterised by low corrected cone resistance (qt) and high friction ratio (Rf). CPTU penetration in peat is often drained with data showing low pore water pressure coefficient (Bq) values. Rf broadly decreases with increasing degree of decomposition of the peat. However care needs to be taken in using Rf values in peat given the characteristically very low sleeve friction values (fs) encountered. It would seem that it is not always easy to distinguish between peat and underlying soft soils using CPTU alone. There may be some promise in inclusion of CPTU “add on” sensors particularly a seismic element to yield shear wave velocity (Vs). However there is some uncertainty in measuring Vs in peat both offshore and onshore so care is needed in this regard. Recently developed Soil Behaviour Type (SBT) charts from the Netherlands have also been trialled on several sites. This new formulation shows promise and warrants further study

  Abstract
  This paper reviews the use of piezocone (CPTU) testing to characterise and identify peats and organic soils. Examples of data for peat sites from several countries are given, [...]

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• CPT based classification with focus on organic soils

  A. Lengkeek*

  ISC2024.

  
  

  Abstract

  Most published research on CPT based SBT classification is on mineral soils. Consequently, these classifications do not accurately capture the classification of soft organic clays and peats. Organic soft soils are frequently present within the Holocene deposits in the Netherlands and in other deltaic areas worldwide. Organic soils can be identified by a specific combination of CPT parameters such as a high friction ratio, low cone resistance and low pore pressure response. In contrast to other soft soils, the strength is not necessarily low. This paper presents an updated CPT based classification with focus on organic soils, for the non-normalized SBT chart (Robertson, 2010, Lengkeek et al, 2022) as well as a new classification based on the stress normalized SBT chart (Robertson, 2016). In the new proposed classifications, additional boundaries are set based on the CPT pore pressure measurements, as this appears to be successful to separate organic soils from mineral soils. The performance of the classifications can be quantified by metrics such as the F1 score. The F1 score of the new proposed classifications all show significant improvement.

  Abstract
  Most published research on CPT based SBT classification is on mineral soils. Consequently, these classifications do not accurately capture the classification of soft organic [...]

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• Cone Penetration Response in Carbonate Sediments

  S. Sharma*, C. Colreavy, N. Boylan

  ISC2024.

  
  

  Abstract

  Cone penetration testing (CPT) is one of the most used site characterisation tools in geotechnical engineering. In offshore areas dominated by carbonate sediments, CPT is extensively used to characterise material types and assess their strength and flow characteristics. However, unlike for non-carbonate sediments where large number of empirical relationships are available correlating the CPT response with the corresponding soil behaviour and associated engineering parameters, there is still a lack of data correlating the CPT response with engineering behaviour of carbonate sediments. This paper presents CPT responses for different types of marine carbonate sediments. First, a brief background on carbonate sediments including key terminologies used and their characteristics in comparison to their non-carbonate counterparts are discussed. This is followed by examples of CPT data from major offshore project sites representing different type of materials ranging from uncemented fine grained (Muds and Silts) and coarse grained (Sand) sediments to variably cemented carbonate materials. The CPT results are then used, in combination with laboratory test data, to evaluate the suitability of standard soil behaviour type charts and indices available in the literature. Typical zone of results for carbonates sediments as a function of normalized cone parameters are also presented for reference purposes. Some challenges on the direct use CPT based methods to engineering analyses for carbonate sediments and the key areas of research from a practical engineering perspective are also briefly discussed.

  Abstract
  Cone penetration testing (CPT) is one of the most used site characterisation tools in geotechnical engineering. In offshore areas dominated by carbonate sediments, CPT is [...]

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• Case studies for temporal variability In site characterisation

  B. Look*

  ISC2024.

  
  

  Abstract

  While site investigation data is typically focused on the spatial variability for site characterisation, those properties may change with time. Temporal variability needs to be considered in the design and construction of roads and high-level foundations. Seasonal variation occurs in the active zone and long-term changes occur 2 to 5 years after construction using expansive clay materials in adverse climate conditions. The latter may occur below the zone of seasonal variation. A case study for seasonal changes in subgrade strength at an uncovered test site when tested at 5 different times of the year. Measurement accounted for 30% of the variation, while temporal and spatial variation accounted for an additional 30% variation over the 1-year period of testing. An appropriate probability distribution function (PDF) is required for characteristic values. Constructing embankments to the equilibrium moisture content (EMC) is more important than the optimum moisture content (OMC), which is a short-term construction expedient. Time Domain Reflectometry (TDR) probes were used to monitor embankment moisture changes over a 4-year period for a new road construction on expansive clays. This included 1) an existing 30-year-old embankment during the project planning phase, 2) a trial embankment during design, and 3) the new constructed roadway embankments. All demonstrated the importance of understanding the EMC when expansive clays are being used for embankment construction. Results in other climatic environments are compared. The results show subgrade CBR tested at OMC is meaningless for such soils and in those extreme climates.

  Abstract
  While site investigation data is typically focused on the spatial variability for site characterisation, those properties may change with time. Temporal variability needs [...]

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• Investigating crushing-induced particle shape change in granular material

  S. Allaev, M. Kikumoto

  ISC2024.

  
  

  Abstract

  High-pressure uniaxial compression tests were conducted under strain-controlled conditions using spherical glass beads. The study focused on investigating the compression behavior and particle fragmentation phenomena, particularly observing changes in particle size and shape resulting from fragmentation. The examination of particle shape, specifically sphericity and roundness, was emphasized. The samples comprised glass beads with uniform particle size and shape initially. It was observed that pressures exceeding 20MPa triggered particle fragmentation, leading to significant compression behavior. Notably, a softening phenomenon characterized by rapid fluctuations in compressive stress, despite a monotonic increase in strain, was observed during fragmentation. This phenomenon indicates the particles' catastrophic failure, unable to withstand the contact forces they previously sustained. Observations of particle shape revealed trends toward asymptotic distributions in cumulative curves for particle size, sphericity, and roundness. Moreover, changes in the cumulative curve of roundness were more pronounced compared to particle size and sphericity.

  Abstract
  High-pressure uniaxial compression tests were conducted under strain-controlled conditions using spherical glass beads. The study focused on investigating the compression [...]

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