Documents published in Scipedia

• Bedrock Depth and Shear Wave Velocity Profile Estimation through HVSR Measurements in the Paraguayan Oriental Region

  T. Stanichevsky*, M. Stanichevsky

  ISC2024.

  
  

  Abstract

  The horizontal to vertical spectral ratio (HVSR) passive seismic method consists in processing measurements of ambient noise performed in three perpendicular directions. The objective is to define the primary resonant frequency of the site and estimate its amplification characteristics, which can be deduced from visible peaks or troughs in the HVSR curves. The shape of HVSR curves depend on the interaction of waves with the interface between sediments and the formation bedrock and, hence, can be related to the bedrock depth through derived relationships. This work presents 4 study cases in the Paraguayan oriental region where HVSR of microtremors were obtained. Furthermore, the obtained HVSR curves are inverted to get approximate shear wave velocity profiles under the assumption of sub-vertically propagating P and S body waves. HVSR curves were calculated through Geopsy (Wathelet et al. 2020) and the inversion process was made through OpenHVSR (Bignardi et al. 2016), both open-source tools for ambient vibration processing. In general, the method proves to give sufficient accurate estimates of sediment thickness and stratigraphy in typical Paraguayan formations of the oriental region and presents the advantage of being an economical and fast survey option, especially for early stages in a geotechnical campaign

  Abstract
  The horizontal to vertical spectral ratio (HVSR) passive seismic method consists in processing measurements of ambient noise performed in three perpendicular directions. The [...]

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• Estimating the fundamental frequency of a sand tailings dam using the H/V spectral ratio method

  C. Pasten*

  ISC2024.

  
  

  Abstract

  This study estimates the fundamental frequency of an 85 m height sand tailings dam in Central Chile using the singlestation Horizontal-to-Vertical H/V Spectral Ratio Method (HVSR), calculated from seismic ambient noise and earthquake records. The dam was constructed by compacting hydraulically deposited sands classified from integral copper tailings, following the downstream construction method. A proper estimate of the dam fundamental frequency is critical for evaluating its seismic response and secure the safe tailings containment when subjected to intense ground motions generated by interface and intraslab earthquakes. Results from the HVSR method are compared with those of the Standard Spectral Ratio method (SSR) calculated as the ratio of the response of the dam crest and that recorded at the dam toe. The fundamental frequency of the dam is about 0.9 Hz in the dam central part away from the abutments, but differences in the vibration frequency are identified along the downstream slope and along the crest axis from the north to south abutment. An analytical relationship between the dam fundamental frequency, the dam height, and the shear wave velocity (Vs) profile is validated.

  Abstract
  This study estimates the fundamental frequency of an 85 m height sand tailings dam in Central Chile using the singlestation Horizontal-to-Vertical H/V Spectral Ratio Method [...]

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• Standardization of Microtremor and Surface Wave Explorations

  C. Konishi*, S. Tsuno, S. Senna, H. Yamanaka

  ISC2024.

  
  

  Abstract

  In recent decades, microtremor and surface wave explorations have been widely applied for geotechnical investigations to estimate the S-wave velocity profile. The estimated S-wave velocity profile provides essential information for site characterization. Since we need to solve an inverse problem with the observed phase velocity of the surface waves to estimate the S-wave velocity profile, acquiring high-quality data is the most critical part. To ensure the data quality and the corresponding results, ISO 24057:2022, array measurement of microtremors to estimate shear wave velocity profile, was developed in 2022. The document specifies appropriate equipment, procedures, data analysis, and reporting for the array measurement of microtremors as a passive geotechnical survey. Since we cannot control the frequency contents in ambient noises, the frequency range with the high power may be limited in the microtremor explorations. In this situation, surface wave exploration can supplement this shortcoming. An example of combining the two results shows that it gives us a dispersion curve in a wide frequency range to estimate the S-wave velocity profile from shallow to deep subsurface structure. Developing a new ISO standard for surface wave explorations by following the microtremor exploration enhances the quality of the estimated S-wave velocity profile. Accordingly, we expect non-destructive and cost-effective investigations to be widely accepted worldwide.

  Abstract
  In recent decades, microtremor and surface wave explorations have been widely applied for geotechnical investigations to estimate the S-wave velocity profile. The estimated [...]

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• Comprehensive Geophysical Assessment of Complex Geological Terrain in Kadapa Basin, India

  S. Laxman, A. Kumar, A. Panjamani*

  ISC2024.

  
  

  Abstract

  Traditional geotechnical investigation consisting of drilling many of boreholes, soil sampling and lab testing becomes uneconomical and time consuming for large and geologically intricate areas. In such cases, non-destructive geophysical surveys offer a time-efficient and economical solution, simultaneously providing an extensive areal coverage of subsurface profiling of geotechnical and geophysical properties. For the estimation of subsurface properties, three geophysical methods were employed in this study, which consisted of Ground Penetration Radar (GPR), Electrical Resistivity Tomography (ERT), and Multi-Channel Analysis of Surface Waves (MASW). Thus, the sub surface’s shear wave velocity profiles and apparent resistivity profiles were obtained. In the shallow depths, discontinuities and fractures were studied using electromagnetic radargrams from GPR. These tests were complemented with borehole exploration at the site. Results obtained from surface-based methods were validated against bore log data and visual observation of surface terrain. Subsequently, bore logs were integrated with the geophysical survey results to construct an integrated subsurface profile. The integrated subsurface profiles presented a three-layer subsurface structure consisting of dense gravelly sand in the top 1m, followed by strong rock formations and, ultimately, very strong fractured rocks. The extent of fracture in the rocks was studied using samples obtained from boreholes and available trenches at the test location. These findings helped compare the three methods and their applicability in delineating different subsurface layers in this study. GPR proves to be effective at shallow depths, while ERT and MASW help investigate deeper layers better. Further, this study offers critical insights for site characterization and engineering decisions in complex geological environments, improving the knowledge base of efficient and reliable subsurface evaluation techniques.

  Abstract
  Traditional geotechnical investigation consisting of drilling many of boreholes, soil sampling and lab testing becomes uneconomical and time consuming for large and geologically [...]

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• Passive Seismics Monitoring Applied to Rock Block Stability in the Montserrat Massif

  M. Janeras*, A. Macau, J. Andrés, F. Parera

  ISC2024.

  
  

  Abstract

  The Montserrat Massif (Catalonia, NE of Spain) is a natural and cultural heritage where rockfall risk arises. Therefore, a risk mitigation plan is underway, including rockfall monitoring at different scales using different techniques. Particularly, the rock block A3-6, menacing the rack railway leading to the monastery, has been monitored since 2010 by extensometers that show the cyclic movement due to the annual thermal cycle, which is mainly recoverable, but small residual plastic derivations have been detected in a varying amount, along years. At the end of 2021, stabilization work has been carried out. The block has been monitored with passive seismic techniques before, during, and after these works in order to detect signs or evidence of evolving stability similar to previous experiences in the Alps. Two main results have been found. On the one hand, a slight difference in the recorded ambient noise between the potentially unstable block and the rear massif was detected, for both the H/V spectral ratio and the polar spectrogram. A characteristic resonance frequency of the block is observed around 20 Hz in the direction of the toppling instability mechanism. On the other hand, during the drilling works of the anchor bolts, it was possible to clearly detect when the drilling hammer crossed the rear joint of the block. This allows confirming the assumed geometry of the block and the required anchor length, as well as a qualitative assessment of the persistence of the joint and its mechanical contact.

  Abstract
  The Montserrat Massif (Catalonia, NE of Spain) is a natural and cultural heritage where rockfall risk arises. Therefore, a risk mitigation plan is underway, including rockfall [...]

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• A Review of Laboratory Cone Penetration Test (CPT) in Unsaturated Soil

  R. Li*, A. Leung, A. Yerro, C. Yu, Z. Jiang

  ISC2024.

  
  

  Abstract

  Cone penetration testing (CPT) is a common site investigation method used to determine soil profiles and characterize in-situ soil properties. However, most of the existing interpretations of CPT data are established for dry or saturated soil. In recent years, studies have shown that ignoring the matric suction effect in unsaturated conditions during data interpretation could lead to biased soil characterization and soil property estimates. Still, due to the lack of fundamental understanding of the mechanics during cone penetration in unsaturated soils, accounting for the matric suction effect on the CPT data-soil properties/characterization is not clearly defined, and more laboratory testing in controlled environments is required to fill this gap in knowledge. Existing studies are different in terms of penetrometer diameters (dcpt), chamber dimensions, penetration rate, sample preparation, and suction control techniques. This paper first presents a review of the existing literature on CPTs performed in unsaturated soils in a controlled laboratory environment and discusses the effects of the aforementioned factors on the measured tip resistance. In addition, new results from centrifuge CPTs performed with controlled water levels in a rigid chamber are presented. For the purpose of such experiments, a 12.7 mm diameter miniature cone penetrometer was designed and fabricated to measure tip resistance values. Unsaturated CPT data show that the presence of matric suction in the soil tends to increase the tip resistance measurement during the cone penetration process. More tests are planned in the future to quantify this increase in CPT response with respect to other soil properties.

  Abstract
  Cone penetration testing (CPT) is a common site investigation method used to determine soil profiles and characterize in-situ soil properties. However, most of the existing [...]

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• Interpretation of CPTu in Sensitive Fine-Grained Soils and Prediction of Residual Excess Pore Pressures in Consolidating Soils

  P. Rahardjo*

  ISC2024.

  
  

  Abstract

  Robertson (1986) soil classification on Sensitive Fine Grained Soils using CPTu is of interest since the variation of these soils include those of Consolidating Soils. However, the classification does not include into detail such as the influence of the existence of excess pore pressure prior to penetration testing or what is the contribution of the excess pore pressure to the total penetration resistance. Rahardjo et al (2008) studied this phenomena by extrapolation of the dissipation test data to determine the residual excess pore pressure which play an important role in CPTu testing. Further, Rahardjo et al (2016) continued investigation of the CPTu in Consolidating Soils using Bq, Bq* and Effective Stress Concept (Rahardjo et al. 2017). These findings have been very useful when using CPTu in very soft soils and ultrasoft soils where the undrained shear strength of the soils is very low. This paper is the results of several studies of CPTu testing in marine clays, lacustrine, ultrasoft soils or even peats. The author found that there is significant value of Bq and Bq*, hence are parameters of importance when dealing with soft soils and discussed in more detail. Recent applications are in very soft soils and peats in Sumatera and East Java mud eruption which are are also included.

  Abstract
  Robertson (1986) soil classification on Sensitive Fine Grained Soils using CPTu is of interest since the variation of these soils include those of Consolidating Soils. However, [...]

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• Effective Friction Angle of Intermediate Grain Size Soils from Variable Rate Piezocone Penetration Test

  Y. Liu, Z. Ouyang*

  ISC2024.

  
  

  Abstract

  The effective friction angle (') is one of the most sought soil properties in geotechnical analysis and design that controls the fundamental soil strength behaviour. In this paper, A recently compiled database on intermediate grain size soils that were tested by variable rate piezocone penetration tests (VRCPTU) is used to examine an effective stress limit plasticity solution using piezocone data developed by NTH (Norwegian Institute of Technology) towards prediction of the geomaterials’ effective stress friction angle. It is shown that penetration rate during probe advancement influences the CPTU measured data and the drainage conditions can be indicated by corresponding normalized cone resistance and normalized porewater pressure measurement. Further analysis revealed that an input parameter termed the angle of plastification (β) from the CPTU solution correlates with soil contraction and dilation tendency and can be used to evaluate the 'of investigated soils, together with other normalized CPTU measurements. The tentative suggested formula of β for intermediate soils undergone VRCPTU testing is given based on the investigated database. A comprehensive testing program on the Yellow River Delta (YRD) silts in China and a silty geomaterial from northern Italy in Europe including benchmark laboratory triaxial tests on high quality samples, field and calibration chamber variable rate CPTU are showcased to demonstrate the verification of the NTH solution for evaluating 'of intermediate grain size soils.

  Abstract
  The effective friction angle (') is one of the most sought soil properties in geotechnical analysis and design that controls the fundamental soil strength behaviour. In [...]

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• Effect on the Local Seismic Response Produced by the Construction of Rafted Piles Foundation

  A. Trevisan, M. Lago*, F. Veronese

  ISC2024.

  
  

  Abstract

  The seismic forces must be properly defined as required by European geotechnical design Codes. They are dependent from the morphological and stratigraphic characteristics that determine the local seismic response. The local seismic response can be evaluated using a simplified approach which is based on the classification of the subsoil according to the values of the shear wave propagation speed Vs. In the present case study, to complete the quay of the Rovigo Interporto (facing the River Canal Bianco), where a not negligible load is planned to be applied (50 kPa), has been designed a foundation with a large slab founded with not pre-casted reinforced concrete piles diameter 350 mm, drilled without removing soil, with vibrating casing, for settlement reduction (rafted piles as settlement reducers), on an area of approximately 6000 m2. The subsoil in this area, from geological and geotechnical point of view, is very variable and with layers of soft clay and loose sand or silt, with no presence of a dense and uniform sand layer where to transfer loads to. Moreover, the geotechnical model was complicated because of the presence of an old diaphragm wall with anchors (whose projection in plant covers around half of area) and was designed a large underground basin for hydraulic invariance. For this reason, an extensive campaign of CPTU and DMT tests, together with boreholes, sampling and laboratory tests was carried out in this area, which allowed a detailed characterization of the subsoil. Through direct measurement of seismic micro-tremors, carried out before and after the installation of the piles, has been evaluated the modification of the resonance frequency of the site, and modification of the propagation speed of the shear waves Vs induced by the slab over rafted piles over the entire area.

  Abstract
  The seismic forces must be properly defined as required by European geotechnical design Codes. They are dependent from the morphological and stratigraphic characteristics [...]

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• Application of two analytical CPTU solutions to sensitive clay in Québec

  P. Mayne, J. Greig, E. Cargill

  ISC2024.

  
  

  Abstract

  A recent series of CPTU soundings in sensitive clay at the Louiseville Quebec test site has been published, allowing for the application of two closed-form analytical solutions based on: (1) effective stress limit plasticity and (2) hybrid cavity expansion-critical state methods. These are used for geoparameter interpretations including: effective stress friction angle, undrained shear strength, yield stress ratio, undrained rigidity index, and the coefficient of consolidation. Profiles of these soil parameters are compared with the benchmark values obtained from available series of previous and present laboratory testing programs at this site, including index testing, triaxial compression, and one-dimensional consolidation. Piezocone dissipation tests are used to assess the coefficient of consolidation which are validated by pressuremeter holding tests and lab oedometer tests. An empirical CPTU screening method identifies the Louiseville site as underlain by sensitive clay, versus a regular insensitive clay deposit, whereas soil behavior type charts using Q-F-Bq indicate the soils are either silt (zone 4) or regular clay (zone 3). The alternate screening method is verified by field vane and laboratory fall cone that show the clay is in fact sensitive (average St ≈ 22).

  Abstract
  A recent series of CPTU soundings in sensitive clay at the Louiseville Quebec test site has been published, allowing for the application of two closed-form analytical solutions [...]

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