Documents published in Scipedia

• Effect of the fines content on the seismic response of a liquefiable deposit based on dilatometer tests

  G. Tropeano, A. Chiaradonna, P. Monaco*

  ISC2024.

  
  

  Abstract

  In the simplified methods for estimating the cyclic resistance ratio (CRR) based on the flat dilatometer test (DMT), the liquefaction triggering curve is defined as a function of the horizontal stress index. A DMT-based calibration of a simplified pore water pressure model for effective stress analyses has been also recently proposed by Chiaradonna et al. (2023), even though limited to an ideal clean sand. This paper aims to explore the effects of the fines content on the seismic response of a liquefiable site where the cyclic strength of the soils is estimated by dilatometer tests. This evaluation is firstly performed on an ideal one-dimensional soil column, where the percentage of fines content is parametrically changed. Then, the study is verified on a real case, by considering a well-investigated site located in the Emilia-Romagna plain (Italy), where widespread liquefaction occurred in the 2012 seismic sequence. Indeed, a comprehensive site characterization from previous in-situ and laboratory tests carried out by various research groups is available for sand, silty sand, and sandy silt deposits encountered in that area. The nonlinear dynamic analyses accounting for the fines content effect are compared with that obtained by adopting the calibration procedure based on laboratory tests. Guidelines and limitations of the proposed approach obtained from this study are useful in providing awareness to practitioners about the calibration strategies for dynamic analysis based on DMT-tests.

  Abstract
  In the simplified methods for estimating the cyclic resistance ratio (CRR) based on the flat dilatometer test (DMT), the liquefaction triggering curve is defined as a function [...]

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• Combined use of cptu-sdmt and geophysical test to assess liquefaction: case studies in Emilia-Romagna (Italy)

  S. Amoroso*, C. Comina, L. Minarelli, K. Rollins, S. Bignardi, F. Vagnon, F. Di Buccio

  ISC2024.

  
  

  Abstract

  The presence of a non-liquefiable crust overlying a liquefiable layer plays a significant role in determining the occurrence of liquefaction damage, as originally formulated by Ishihara in 1985. Following the 2010-2011 Canterbury seismic sequence (New Zealand), almost no foundation deformation occurred in areas characterized by soils susceptible to liquefaction overlaid by at least 3 m-thick intact crust. In contrast, the 2012 Emilia-Romagna earthquake (Italy) provided evidence of liquefaction in silty-sandy layers below 3 to 9 m-thick crusts. Therefore, Ishihara’s approach and the variety of liquefaction severity indices need to be further tested to assess to what extent they can be considered reliable predictors of performance. This study aims at better understanding the role of non-liquefiable crusts in preventing damage to buildings and infrastructures. In this respect, in situ and laboratory tests were conducted at selected sites in EmiliaRomagna. The results of two case studies in Mirandola (Modena, Italy), which share similar soil profiles but exhibited different liquefaction evidences following the 2012 seismic sequence, are presented. Comprehensive geotechnical and geophysical surveys were performed at both the sites, by means of piezocone tests, seismic dilatometer tests, boreholes, laboratory tests, electrical resistivity tomography and multichannel analysis of surface waves. These surveys document the geotechnical and geophysical properties of the 5 m-thick non-liquefied (or potentially non-liquefiable) crust and of the liquefied (or potentially liquefiable) silty-sandy deposits. This effort is aimed at understanding how the surface layer properties contributed to the different behavior observed at the two sites during the earthquake events.

  Abstract
  The presence of a non-liquefiable crust overlying a liquefiable layer plays a significant role in determining the occurrence of liquefaction damage, as originally formulated [...]

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• Comparison of Pore Pressure Parameters from Piezocone and Dilatometer

  J. Benoît*, B. Souza

  ISC2024.

  
  

  Abstract

  The Piezocone (CPTU) and the Marchetti Flat Plate Dilatometer (DMT) provide a number of empirical correlations for the purpose of soil identification. Each tool has defined a pore pressure parameter. For the piezocone, the parameter Bq ‘is based on the penetration pore pressures, the corrected tip resistance, the total overburden stress, and the existing hydrostatic pore pressure. This index has been used to characterize soil behavior rather than the actual soil type. For the dilatometer, the parameter Ud is based on the corrected pressures p0 and p2, calculated using the A and C readings and the existing hydrostatic pore pressure. This index can be combined with the material index ID to help with soil identification. Results from several test sites provide a promising direct correlation between Bq and UD, which can be used to enhance the identification of soil types by simply using the C-reading when performing DMT tests. Although the C-reading has been grossly ignored by users of the DMT, this new development will encourage measurement of this reading which provides similar trends to the pore pressures measured by the CPTU. The latest DMT equipment allows for the automatic measurement of the C-reading, which will assist in developing and enhancing existing correlations. This paper will present results at test sites located on opposite coasts of the USA. The trends of the Bq and UD indices are shown to be remarkably similar in all types of soils.

  Abstract
  The Piezocone (CPTU) and the Marchetti Flat Plate Dilatometer (DMT) provide a number of empirical correlations for the purpose of soil identification. Each tool has defined [...]

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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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