Documents published in Scipedia

• Stress History and Effective Shear Strength Parameters Evaluation of a Dilative Stiff Clay

  G. Pinto*, M. Araujo, A. Faria, J. Carneiro, M. Junior

  ISC2024.

  
  

  Abstract

  The Cone Penetration Test (CPTu) can be used to evaluate the soil behaviour and properties through correlations (empirical and/or analytical), and the results must be compared to laboratory tests to be validated. This paper presents the evaluation of the effective friction angle (φ’) of a stiff over-consolidated Brazilian clay based on CPTu data and laboratory tests characterization, such as index properties, and the comparison of the effective shear strength parameters obtained by triaxial tests. Based on CPTu data, the soil was classified using the Soil-Behaviour Type Classification System (SBTn) proposed by Robertson (2016), and properties such as over-consolidation ratio (OCR) and the effective friction angle were determined using well-known correlations such as Chen & Mayne (1996) and Ouyang & Mayne (2019). The shear response defined by CPTu was compared to the results of isotropic consolidated triaxial compression tests (CIUC). The results showed mainly a clay-like behaviour based on the CPTu data, in agreement with the laboratory characterization, which indicated high plasticity. Regarding the shear response, both the triaxial test and the CPTu data indicated dilative behaviour under shear. Furthermore, the effective friction angle obtained from the triaxial test and the CPTu data were similar depending on the OCR used in the equation, demonstrating the applicability of the adopted methodologies for the Brazilian stiff over-consolidated clay. Finally, based on CPTu data it is proposed a complement of the SBTn developed by Robertson (2016) with OCR isolines.

  Abstract
  The Cone Penetration Test (CPTu) can be used to evaluate the soil behaviour and properties through correlations (empirical and/or analytical), and the results must be compared [...]

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• Numerical and experimental assessment of steering forces during horizontal penetration in sand – a validation of a bio-inspired optimal tip shape

  F. Patino-Ramírez*, J. Salomon, Y. Yang, A. Holmes, C. O’Sullivan

  ISC2024.

  
  

  Abstract

  The exploration, characterisation, and monitoring of the subsurface is relevant to a wide range of applications, from environmental monitoring and in-situ characterisation to infrastructure construction (e.g., directional drilling and tunnelling) and resource withdrawal. Bio-inspiration offers promising solutions to overcome two of the most important challenges in the development of autonomous subsurface exploration probes: exploration range (related to drag forces) and steerability (i.e., ability to control direction of movement). The work uses a previously proposed bio-inspired intruder shape to study the relationship between tip orientation and the resulting forces (lateral and vertical); and explores the idea that these forces can be used to steer the probe, i.e., control the direction of motion of the probe as it advances. Numerical results with the discrete element method and experimental results with a large-scale test bed show a direct relation between tip orientation and the steering (lift and lateral) forces – supporting the case for steering systems based on intruder tip rotation. In the results, lateral and vertical forces also show a strong relation with tip orientation, however, for the tip shape tested, the vertical forces are limited to the neutral to upwards range (i.e., towards the free surface). Experimental results evidence the significant effect of intruder deformation (bending) and/or path deviation in the penetration forces acting on the intruder.

  Abstract
  The exploration, characterisation, and monitoring of the subsurface is relevant to a wide range of applications, from environmental monitoring and in-situ characterisation [...]

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• Particle Crushing and Liquefaction Resistance of Crushable Aragonite Sands

  M. Saqib*, A. Das, N. Ranjan, P. Patra

  ISC2024.

  
  

  Abstract

  The influence of soil crushability on the strength parameters of aragonite sand under cyclic undrained conditions is investigated in this study. The investigation used aragonite sand, which is known for being susceptible to crushing under normal loading conditions. A series of cyclic simple shear tests were carried out at different normal loads of 100kPa, 150kPa, 200kPa, and 250kPa under a constant confining pressure. To maintain consistency in particle crushing, sieving tests were used to assess the level of particle breaking, with testing stopping after a predetermined number of cycles. The results show that particle crushing increased the fines content of the soil, even when the effective stress was low during the undrained shear phase. The liquefaction resistance of aragonite sands increased as normal load increased. These findings show the major influence of soil crushability on the engineering behavior of aragonite sand, implying that conventional assumptions about the link between normal load and liquefaction resistance may not be true for crushable soils.

  Abstract
  The influence of soil crushability on the strength parameters of aragonite sand under cyclic undrained conditions is investigated in this study. The investigation used aragonite [...]

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• Hydraulic Profiling Tool for Groundwater Vulnerability Assessment at an MSW Landfill

  P. Singh*, D. Haritwal, G. Ramana, M. Datta

  ISC2024.

  
  

  Abstract

  Characterization of the unsaturated zone below an MSW landfill is critical to evaluate the groundwater pollution vulnerability assessment. The permeability of the soil in the unsaturated zone, the depth of the water table, and the quality of pore water in the soil can provide a reliable site-specific estimate of pollution vulnerability. To evaluate these factors, an attempt was made to use the hydraulic profiling tool (HPT) in the unsaturated zone below a non-engineered MSW landfill in Delhi. HPT was equipped with an injection logger capable of qualitatively measuring permeability at the cm scale and an electrical conductivity (EC) dipole that measures the bulk soil conductivity. HPT findings were compared with piezocone penetration tests (CPTu) and the electrical conductivity of extracted pore water from the soil cores. The results indicate that pressure from the injection logger works effectively for medium/fine sand and silt and has greater sensitivity to permeability changes for these soils than CPTu. Pore-water EC was found to have a good correlation with volumetric water content and EC from HPT. A groundwater vulnerability matrix was conceptualized using factors based on the time of leachate travel and maximum pore-water EC observed, both derived from HPT, and risk scores were assigned from 1-5, corresponding to the 9 zones of the matrix. The locations surveyed at the dumpsite received scores of 4 and 5, which depicts high vulnerability. The results indicate that HPT can be used for rapid site-specific groundwater vulnerability assessments.

  Abstract
  Characterization of the unsaturated zone below an MSW landfill is critical to evaluate the groundwater pollution vulnerability assessment. The permeability of the soil in [...]

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• Comparison Between Eggshell Lime and Commercial Lime as a Soil Stabilizing Agent

  B. Meneguz, H. Nierwinski, B. Caetani*

  ISC2024.

  
  

  Abstract

  Reducing the extraction of natural resources is a current demand in the construction industry. Studies show that eggshells are rich in calcium carbonate and have the potential to replace limestone in lime production. In this context, the objective of this article is to use an eggshell lime produced in the laboratory to stabilize a residual clayey soil and compare the unconfined strength of the admixtures with others using commercial dolomitic lime. Different lime contents and porosities were evaluated and the porosity/lime ratio was studied to understand the unconfined strength behavior of admixtures. In addition to the soil and limes characterization tests, X-ray diffraction tests were carried out to analyze the chemical and mineralogical composition of the materials. The results showed that increasing lime content and decreasing porosity increased unconfined strength. Also, the unconfined strength achieved with the eggshell lime was greater than that achieved with dolomitic lime for the same lime content. The X-ray diffraction tests showed that the eggshell lime is composed almost entirely of calcium hydroxide, and microscopic images demonstrated much stronger bonds in the final product obtained from eggshell lime. The porosity/lime ratio was a good parameter for evaluating unconfined strength. A unique relationship was achieved linking unconfined compressive strength with the porosity/lime ratio for both the eggshell and the dolomitic lime mixtures.

  Abstract
  Reducing the extraction of natural resources is a current demand in the construction industry. Studies show that eggshells are rich in calcium carbonate and have the potential [...]

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• Considerations on the site characterization of tropical soils by in situ tests

  B. Rocha, R. Rodrigues, H. Giacheti*

  ISC2024.

  
  

  Abstract

  The fundamentals for predicting the mechanical behavior of soils by in situ tests have been developed for conventional soils (either clay or sand) based on the stress history. The behavior of unusual geomaterials, such as the tropical soils, is characterized by bonding and structure, anisotropy as well as by the unsaturated condition. The behavior of tropical soils cannot be correctly predicted by models and correlations developed by the Classical Soil Mechanics. This paper presents the fundamentals of the behavioral classifications used to interpret CPT and SDMT and discusses their applicability to tropical soils, especially those of pedogenetic evolution of sandstone. Laboratory and in situ tests (CPTu and SDMT) were carried out at two research sites in São Paulo state, Brazil, at different periods of the year to better understand the soil behavior and the seasonal effects. Classifications and correlations to estimate soil parameters from CPTu and SDMT are assessed. Interrelationships between elastic parameters of small (G0) and large to medium strain parameters (qc, ED, MDMT) determined by in situ tests are presented to identify the presence of microstructure and unusual soil behavior. Classification criteria based on these relationships to identify collapsible soils also is presented

  Abstract
  The fundamentals for predicting the mechanical behavior of soils by in situ tests have been developed for conventional soils (either clay or sand) based on the stress history. [...]

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• 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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