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• The JELLYFISh Project: Medusa SDMT testing at the NGTS Geo-Test sites, Norway

  P. Monaco*, A. Chiaradonna, D. Marchetti, S. Amoroso, J. L’Heureux, T. Le

  ISC2024.

  
  

  Abstract

  This paper presents an overview of the experimental activity and the main results obtained as part of the Transnational Access project – JELLYFISh funded by H2020-GEOLAB. The project is based on an extensive in-situ testing campaign with the Medusa SDMT, the newest fully automated version of the seismic dilatometer (SDMT). The campaign was carried out in June 2022 in different soil types at four well-known benchmark test sites in Norway: Halden (silt), Onsøy (soft clay), Tiller-Flotten (quick clay), and Øysand (sand). These benchmark sites, largely documented in previous research, are part of the Geo-Test Sites (NGTS) research infrastructure managed by the Norwegian Geotechnical Institute. The paper includes: (i) highlights of the JELLYFISh project, (ii) a brief description of the Medusa SDMT main features, (iii) a summary of the field testing program at the four sites, (iv) a comparison of the results provided by Medusa SDMT using alternative test procedures and by traditional (pneumatic) SDMT and (v) conclusions. The results of the project highlight that, due to improved accuracy of pressure measurements and controlled pressurization rate, the Medusa SDMT has the potential for providing significant advancement in soil characterization compared to the traditional SDMT technology. These capabilities are particularly useful when investigating soft clays (e.g., Onsøy) in which the measured pressures are typically very small, intermediate soils (e.g., Halden) in which non-standard test procedures using variable penetration/pressurization rates may be easily implemented, or sensitive clays (e.g., Tiller-Flotten) in which alternative test procedures may provide guidance for distinguishing quick and non-quick clays.

  Abstract
  This paper presents an overview of the experimental activity and the main results obtained as part of the Transnational Access project – JELLYFISh funded by H2020-GEOLAB. [...]

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• Soil Behavior and Shear Strength Parameters of an Organic Alluvium Soil Using the CPTu and DMT

  G. Pinto*, M. Junior, B. Hoch

  ISC2024.

  
  

  Abstract

  The evaluation of in-situ behaviour, strength and compressibility of a soil profile is routinely performed by geotechnical engineers through field tests, such as the seismic piezocone penetration test (SCPTu), the flat dilatometer test (DMT) and the field vane shear test (FVT). This paper aims to compare the results of a CPTu, DMT and FVT to evaluate an organic alluvium soil in terms of: i) in-situ soil behaviour classification, ii) undrained shear strength and iii) stress history. To compare and complement the in-situ results, laboratory tests were carried out to determine the grain-size distribution, the Atterberg Limits, the pre-consolidation pressure, the organic content and the undrained shear strength under isotropic consolidation triaxial test (CIUC). The results showed that the soil evaluated herein exhibited a clay-like behaviour based on the classification system of both tests (DMT and SCPTu), which agrees with the laboratory characterization. Furthermore, the OCR (overconsolidation ratio) calculated from the SCPTu and DMT also shows a convergence with the values determined from laboratory tests. The SCPTu performed in this soil was predominantly undrained and enabled the calculation of undrained shear strength. Based on this, the methodologies based on Nkt and N∆u (from SCPTu) were compared with the undrained shear strength from the FVT and that obtained from DMT, based on the KD parameter. Finally, a comparison is presented to discuss the influence of shear mode in the undrained shear strength and the applicability of the methodologies used to evaluate the soil behaviour and the stress history.

  Abstract
  The evaluation of in-situ behaviour, strength and compressibility of a soil profile is routinely performed by geotechnical engineers through field tests, such as the seismic [...]

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• Experimental Study of DMT Blade in Sand Using Particle Image Velocimetry

  J. Fumeron*, F. Villalobos, R. Moffat, F. Acuña

  ISC2024.

  
  

  Abstract

  In the study of geotechnical problems, numerical methods such as finite and discrete elements are progressively more used, sometimes overlooking experimental studies. Therefore, this work emphasizes the importance of physical experimentation, applying a digital image correlation (DIC) methodology. For this research, particle image velocimetry (PIV) was chosen using the GeoPIV-RG software. A model replicating the geometry of a full-scale DMT blade was used to evaluate its impact. An experimental setup was designed and built to recreate the driving of this geometry in dry and loose Bío-Bío sand, recording the process through photographs for analysis by PIV. Results show cumulative displacements, displacement patterns according to depth, and analysis of incremental shear deformation. A displacement direction analysis was carried out. It is concluded that the displacement pattern generated by its driving corresponds to an angle much smaller than what is reported for the CPT, and the incremental shear strain does not exceed 2% during the driving process.

  Abstract
  In the study of geotechnical problems, numerical methods such as finite and discrete elements are progressively more used, sometimes overlooking experimental studies. Therefore, [...]

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• The use of SDMT Data for Local Seismic Response Studies in the Catania Area

  A. Cavallaro, S. Grasso, M. Sammito*, A. Scotto di Santolo

  ISC2024.

  
  

  Abstract

  Soil stiffness at small strain is a key parameter to solve many geotechnical problems, such as the design of the foundation and the knowledge of the seismic behaviour. There are many methods to perform in-situ soil shear wave velocity measurements: Down Hole test (D-H), Cross Hole test (C-H), Spectral Analysis of Surface Waves (SASW), Multichannel Analysis of Surface Waves (MAWS), etc. Among these methods, the use of Seismic Dilatometer Marchetti Tests (SDMT) to measure the shear wave velocity profile was developed and used in Italy. This test shows good repeatability of the measurements and the possibility to know, at the same time, the mechanical soil characteristics in the static field. In order to evaluate the soil profile of shear wave velocity (Vs), deep site investigations have been undertaken in some Italian sites, prone to high seismic risk. C-H and D-H tests, SDMT and Noise Analysis Surface Waves (NASW) have been carried out. In this paper, the relevance of using the Seismic Dilatometer Marchetti Tests (SDMT) as a basic tool for a comprehensive soil site characterization to carry out a local seismic response study was analyzed.

  Abstract
  Soil stiffness at small strain is a key parameter to solve many geotechnical problems, such as the design of the foundation and the knowledge of the seismic behaviour. There [...]

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• Analysis of DMT Results and Comparison with Other In Situ Tests in a Sensitive Clay of Eastern Canada

  V. Silvestri*, C. Tabib

  ISC2024.

  
  

  Abstract

  This paper presents a re-evaluation of test results obtained from an extensive series of in-situ tests carried out in a lightly overconsolidated sensitive clay of eastern Canada. The geotechnical investigation involved self-boring pressuremeter tests (SBPMTs), flat dilatometer tests (DMTs), hydraulic fracture tests (HFTs), and vane shear tests (VSTs). The first surprising result is that the in-situ coefficient of lateral pressure at rest, K0, deduced from DMTs, SBPMTs, and HFTs is much higher than expected. Second, the values of the overconsolidation ratio, OCR, computed from DMT data are also much higher than oedometer-deduced values. Third, undrained shear strengths obtained from SBPMT expansion curves are higher than both DMT- and VST- deduced values, with the latter tests yielding very similar results.

  Abstract
  This paper presents a re-evaluation of test results obtained from an extensive series of in-situ tests carried out in a lightly overconsolidated sensitive clay of eastern [...]

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• Comparative Assessment of DMT-Based and CPT-Based Transformation Models for the Estimation of Shear Wave Velocity: a Case Study in Central Italy

  M. Uzielli*, D. Marchetti, S. Amoroso

  ISC2024.

  
  

  Abstract

  The definition of the shear wave velocity profile is a fundamental step for the seismic characterization of a site in the context of Eurocode 8 and for the conduction of earthquake geotechnical engineering efforts such as site response analysis. Shear wave velocity profiles can be obtained: (1) directly from seismic geophysical and seismic geotechnical tests; or (2) indirectly, from “static” in-situ geotechnical tests such as dilatometer tests (DMT) and cone penetration tests (CPT). In the latter approach, shear wave velocity is estimated by using transformation models which are typically derived from data collected at other sites. This paper illustrates the procedures and main results of the comparative assessment of the performance of existing DMT-based and CPT-based transformation models to estimate shear wave velocity at two adjacent spatial locations in a rural site in the region of Tuscany in central Italy. Model-predicted shear wave velocity profiles were compared with direct measurements obtained by geophysical seismic dilatometer (SDMT) testing. The comparative assessment involved the definition, calculation, and assessment of quantitative performance statistics. The paper provides a critical analysis and a discussion of the outcomes with respect to soil type.

  Abstract
  The definition of the shear wave velocity profile is a fundamental step for the seismic characterization of a site in the context of Eurocode 8 and for the conduction of earthquake [...]

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• DMT-based liquefaction assessment accounting for the fines content effect: a case study Emilia-Romagna italy

  R. Cecchi, A. Chiaradonna, P. Monaco*

  ISC2024.

  
  

  Abstract

  Simplified methods for seismic liquefaction assessment based on the flat dilatometer test (DMT), in which the liquefaction triggering curve is defined based on the horizontal stress index (KD), have been proposed over the years. One major drawback of the existing methods, valid for clean sand, is the lack of a correction factor for the fines content. An updating of the empirical relationship CRR-KD proposed by Chiaradonna and Monaco (2022) to incorporate the effects of the fines content is currently under development and validation. This paper illustrates the results obtained from application of the new method at the site of San Carlo – Terre del Reno (Ferrara) located in the Emilia-Romagna plain (Italy), where widespread liquefaction occurred in the 2012 seismic sequence. A comprehensive site characterization from previous insitu and laboratory tests carried out by various research groups is available for the sand, silty sand and sandy silt deposits in the San Carlo area. The performance of the new CRR-KD curve accounting for the fines content effect is compared with that obtained by adopting the “clean sand” curves proposed by Chiaradonna and Monaco (2022), as well as with that obtained by using the CPT-based method by Boulanger and Idriss (2014). Even though verified only for specific Italian soils in this area and requiring further field validation, the proposed approach appears as promising to improve the DMTbased liquefaction assessment in silty sands.

  Abstract
  Simplified methods for seismic liquefaction assessment based on the flat dilatometer test (DMT), in which the liquefaction triggering curve is defined based on the horizontal [...]

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• Deformability Parameters in the Offshore In-Situ-Test Survey for the New Breakwater Project in Genova Italy

  M. Sacchetto*, D. Marchetti

  ISC2024.

  
  

  Abstract

  The harbour of Genova is currently protected by a breakwater barrier that is 4 km long. One of the ongoing PNRR projects in Italy consists in dismissing the current breakwater and rebuilding it farther away from shore. The new breakwater will extend to a length of over 6.2 km and allow large cargo and container ships with over 400 m length to access the harbour. The new breakwater will lie in the currently open and unprotected water of the Genova Bay, with water depths up to 50 m. An extensive in situ test campaign of CPT and DMT tests was carried out for soil characterization, to provide stratigraphy, deformability and strength parameters required for the design of the new breakwater foundations. The Manta seafloor penetrometer designed by Geomil was deployed with a crane, operating from a floating pontoon anchored in turn on each of the test locations. The fully automated version of the flat dilatometer (Medusa DMT) and a CPTU tip were alternatively pushed by the Manta, with penetration depths up to over 27 m from seabed. This paper presents results of the moduli obtained from DMT tests employing the standard Marchetti’ formulas and compares them with the interpretation from the CPT using different correlation factors. Additionally, the correlations between Bq (obtained from CPTU) and Ud (obtained from DMT) are analysed.

  Abstract
  The harbour of Genova is currently protected by a breakwater barrier that is 4 km long. One of the ongoing PNRR projects in Italy consists in dismissing the current breakwater [...]

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• (S)DMT Tests in Structured Soils. Lessons Learned from Portuguese Granitic Massifs Characterization

  N. Cruz*, C. Rodrigues

  ISC2024.

  
  

  Abstract

  Characterization of structured soils by in-situ tests cannot be interpreted with success by applying the methodologies dedicated to sedimentary soils, due to the presence of cemented structures that deeply influences its mechanical behaviour, deviating from Classical Soil Mechanics concepts. From the shear strength point of view, structured soils are represented by two parameters that must be derived simultaneously (cohesion intercept and angle of shearing resistance), which is only possible to achieve in tests that measure more than one parameter, such as DMT, CPTu or PMT tests. In its turn, deformability of structured soils is characterized by 2 yield points, one related with beginning of weak bonds yield (first yield) and another one related with the complete breakage of the bond structure (bond yield or gross yield), which are not present in de-structured soils. As consequence, moduli decay curves are more pronounced than those typically displayed in sedimentary soils. The research based in Portuguese granitic environs tested by (S)DMT has shown its usefulness in the characterization of these structured materials. The whole research frame included the characterization of several sites by means of CPTu and DMT tests, laboratorial testing, a calibration apparatus where DMTs were performed in artificially cemented soils closely controlled by triaxial and other laboratorial tests and several sets of SDMT, PMT, CPTu and triaxial tests performed in a high-quality experimental site (IPG). The accumulated experience arising from these experimental frames will be summarized and discussed in the present paper.

  Abstract
  Characterization of structured soils by in-situ tests cannot be interpreted with success by applying the methodologies dedicated to sedimentary soils, due to the presence [...]

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• Using Dilatometer to Predict Stress Increase Component of Foundation Settlement

  R. Failmezger*

  ISC2024.

  
  

  Abstract

  Because soil resists applied stresses in the x, y, and z directions, the ratio of horizontal to vertical stresses, ko, determines the soil stress distribution. The dilatometer test predicts the unit weight of the soil and the horizontal stress ratio at rest, ko, providing the necessary input to determine the stress increase applied to the soil. The Boussinesq stress distribution assumes the soil has a linear elastic stress-strain relationship. This distribution has no input from the soil’s material properties. Harr (1977) proposed using the normal probability distribution with ko input to more accurately compute stress distribution. The authors show the Harr stress distribution for different values of ko and compares them with the Boussinesq stress and Westergaard stress distributions. The authors also present some case studies of stress distribution measurements and proposes modern instrumentation needed for additional research to determine the best prediction method.

  Abstract
  Because soil resists applied stresses in the x, y, and z directions, the ratio of horizontal to vertical stresses, ko, determines the soil stress distribution. The dilatometer [...]

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