Documents published in Scipedia

• Development of liquefiable zone mapping using semi-empirical methods

  B. Berkat*, A. Akhssas

  ISC2024.

  
  

  Abstract

  One of the most significant processes in soil dynamics is liquefaction. It is a loss of strength coupled by a quick increase in pore pressure, causing soil particles to break apart for a brief period. There have been several approaches published for calculating the residual or liquefied shear strength of cohesionless soils. This article gives cone penetration test relationships for assessing vulnerability to loss of strength and liquefied shear strength in a variety of soils. Then, based on the results of our studies, we were able to map the liquefiable zones of the Mnasra region, located in the Gharb basin and extending over an area of 4000 km2, which is characterized by two main facies: (i) a predominantly gravelly and/or conglomeratic facies, separated by silt-clay levels (east of the nappe), (ii) a predominantly sandy, sandstone and calcareous facies, separated by silt-clay levels (coastal zone and southern sector on the Maâmora side). IPL calculations predict a spatial-temporal variation in liquefaction at depths ranging from a low probability of liquefaction to a certainty

  Abstract
  One of the most significant processes in soil dynamics is liquefaction. It is a loss of strength coupled by a quick increase in pore pressure, causing soil particles to break [...]

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• A Numerical Study on Effect of Site Conditions on Connection Load in Geosynthetics-Reinforced Soil Wall

  A. Kumar*, A. Prashant

  ISC2024.

  
  

  Abstract

  Geosynthetics-reinforced soil (GRS) walls have gained immense popularity among other reinforced soil walls. In recent times, case studies have highlighted several GRS walls facing problems such as cracking on the facia, breakage of connection pins in the segmental block, breakage of connection between facia and reinforcement, and relative settlement between facia and backfill, all leading to the serviceability issues or failure of the wall. The existing design methods estimate connection loads using laboratory pull-out tests, which do not incorporate the effect of on-site conditions, such as differential settlement, compaction-induced stresses, and facia geometry, and the stress mobilization in the connection system. This study examines the stress distribution in the facia connection system of segmental reinforced soil walls subjected to site conditions such as inadequate backfill compaction and differential settlement between facia and backfill. A finite element (FE) approach has been adopted to predict the stresses in the reinforcement for the connection loads in the reinforcement-facia connection system subjected to the above-mentioned conditions. The modular block facia, along with geogrid reinforcement connections, was studied, incorporating appropriate geometrical and interface properties (viz. geosynthetics-block interfaces). Based on the study, the obtained variation in the von Mises stresses in the geogrid, embedded in the modular block, due to connection load at the service state was analysed. A comparative analysis of the performance of three different segmental block facia-reinforcement connections was also performed to understand their suitability in a particular site condition

  Abstract
  Geosynthetics-reinforced soil (GRS) walls have gained immense popularity among other reinforced soil walls. In recent times, case studies have highlighted several GRS walls [...]

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• Shear Wave Velocity Derived from Cone Penetration Tests In Clayey Soil Layers

  W. Li*, X. Ma, L. Luo, Z. Ouyang

  ISC2024.

  
  

  Abstract

  Based on Cone penetration tests (CPT) data, a number of soil’s physical and mechanical parameters can be interpretated, like shear wave velocity, etc. Even though various studies have been conducted and methods are proposed, uncertainties still exist and the applicability of each method needs be further clarified. A case study on the interpretation of CPT results is performed which based on the measured data from an offshore site close to East Sea, China. This paper focus on clayey soil layers and presents an assessment of CPT data interpretation methods for the derivation of clayey soil’s shear wave velocity. It shows that Long’s method proposed in 2010 (C1) and Cai’s method proposed in 2014 (C2) provide better predictions of shear wave velocity. Additionally, values of soil unit weight used in the shear wave velocity derivation can also be interpretated from CPT data since it shows ignorable effect on the interpretated velocity profile.

  Abstract
  Based on Cone penetration tests (CPT) data, a number of soil’s physical and mechanical parameters can be interpretated, like shear wave velocity, etc. Even though various [...]

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• Numerical study of viscous effects during CPTu

  L. Hauser*, D. Durán, L. Monforte, M. Arroyo, A. Gens

  ISC2024.

  
  

  Abstract

  Variable penetration rates during CPTu may impact cone readings through partial consolidation during penetration but also through viscous soil skeleton behaviour. The latter phenomenon is characteristic of dynamic penetrometers during fast penetration in fine-grained materials where tip resistance increases when the penetration rate increases. In this work, the effect of viscosity on piezocone penetration is investigated based on the numerical simulation of CPTu and triaxial tests using the application G-PFEM and a viscoplastic version of the Clay and Sand Model (CASM). The study highlights that the CPTu results are sensitive to the material parameters controlling viscosity, thus requiring careful calibration in order to obtain realistic CPTu simulations.

  Abstract
  Variable penetration rates during CPTu may impact cone readings through partial consolidation during penetration but also through viscous soil skeleton behaviour. The latter [...]

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• Prediction of Land Surface Subsidence in the U2 Metro Tunnel in Vienna

  O. Kichaieva*, D. Adam

  ISC2024.

  
  

  Abstract

  This paper discusses the numerical and probabilistic modelling of the tunnel construction concerning some not yet completed sections of the Vienna U2 metro line. It presents the algorithm and results analysis of numerical simulation for the step-by-step tunnel construction using the New Austrian Tunnel Method (NATM) in a dense urban environment. The nature and magnitude of subsidence of the earth surface depending on a number of factors involved in the calculation scheme are determined, and all parameters of the stress-strain state of the system "tunnel - ground mass" are obtained. A methodology is proposed for determining reliability by the criterion of additional vertical subsidence of the ground surface which accompanies underground construction. By comparing the results of numerical modelling, empirical calculation and geotechnical monitoring of the metro construction site, it is shown that they correlate well enough with each other. The results of this study can be used to predict the level of the ground settlement during tunnelling works in areas of dense urban development.

  Abstract
  This paper discusses the numerical and probabilistic modelling of the tunnel construction concerning some not yet completed sections of the Vienna U2 metro line. It presents [...]

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• Availability of artificial neural network for Estimation of Consolidation Properties of Holocene Clays in Osaka Bay

  K. Oda*, S. Yamamoto, M. Kondo, T. Inui

  ISC2024.

  
  

  Abstract

  In this study, artificial neural network, a popular machine learning technique, was used to estimate the consolidation properties of points where no soil investigations have been conducted. The Holocene clay layer at the construction site of Kobe Airport, a large-scale man-made island in Osaka Bay, was targeted to estimate the consolidation properties. The performance of an estimation model built with artificial neural network depends on the datasets used during the training phase. Therefore, the average of multiple estimation results can be used. Numerical simulations using the estimated consolidation properties can accurately reproduce the settlement behavior owing to reclamation during the construction of Kobe Airport. Artificial neural network can easily and objectively estimate the consolidation characteristics of any point based on the existing soil investigation results.

  Abstract
  In this study, artificial neural network, a popular machine learning technique, was used to estimate the consolidation properties of points where no soil investigations have [...]

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• A Case Study on Quantile and Percentile Regression to Select Design Lines for Complex, Real Work Profiles

  J. Valderrama*, M. O'Neill, F. Bransby, P. Watson

  ISC2024.

  
  

  Abstract

  Site characterisation necessarily relies on engineering judgement, usually combined with some level of statistics to define characteristic values for design purposes. A suitable method for this task is quantile regression, which allows for the definition of lower, upper, and best-estimate characteristic values. The application of quantile regression to homogeneous profiles is relatively straightforward. Although such sites are common in some areas, there is need for a more comprehensive approach to quantile regression that covers the more general scenario of heterogeneous stratified profiles. This paper takes piezocone penetrometer data from a relatively complex seabed site and demonstrates the streamlined application of quantile regression, highlighting and analysing some of the assumptions and choices behind the approach. The work shows the nuances of the method and suggests workarounds for potential scenarios where its application may be challenging.

  Abstract
  Site characterisation necessarily relies on engineering judgement, usually combined with some level of statistics to define characteristic values for design purposes. A suitable [...]

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• Effect of clay activity and interface surface material on residual undrained interface strength: implications on pipeline-seabed interaction analysis

  R. Das*, Z. Westgate, A. Sephoori, S. Garmon

  ISC2024.

  
  

  Abstract

  Characterization of the geomechanical behavior of the seabed along a high-pressure high-temperature (HPHT) pipeline route is important for understanding risks from geohazards and thermally induced displacements such as axial walking. Axial resistance to pipeline displacement, from the friction between seabed and the contact surface of the pipe, can be estimated through laboratory tests using interface shear box (ISB) and tilt table. Tests performed by NGI in several developements in Gulf of Mexico, South America, and West Africa revealed significant variation in shear resistance, potentially associated with the type of interface material and surface roughness characteristics. This paper illustrates the effect of clay activity and interface surface material on the residual undrained interface strength estimated from interface shear box tests. Two cohesive soil batch samples with varying activity were tested using two different interface plates (steel and silicon carbide sandpaper) of comparable surface roughness. Each soil batch-interface combination was tested under three different initial effective normal stresses and two different over consolidation ratios (OCRs). Undrained residual interface strength envelopes were developed for each soil batch-interface combination. The results from tests performed on steel interface showed an increase in residual undrained interface strength with plasticy and clay activity whereas a reverse trend was observed in the results of the tests performed using the sandpaper interface. This reinforces the importance of the choice of interface plate material (in addition to surface roughness) for PSI testing program to accurately capture the resistances offered by the seabed to pipe displacement.

  Abstract
  Characterization of the geomechanical behavior of the seabed along a high-pressure high-temperature (HPHT) pipeline route is important for understanding risks from geohazards [...]

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• Uncertainty Estimation on Active Surface-Waves Based Tests

  E. Saez*, F. Hernandez, R. Vega, J. Tiznado, R. Gallardo, F. Leyton, G. Montalva, C. Pasten

  ISC2024.

  
  

  Abstract

  Geophysical methods based on surface waves have become very popular in recent decades due to their versatility and reduced cost of execution compared to other invasive techniques. Due to space constraints in urban environments, measurements with linear arrays using active and passive techniques are usually combined to reach the exploration depth required by seismic site classification regulations. Although several good practice guidelines have been developed for performing this type of geophysical explorations, one of the remaining major challenges is to relate the results of these explorations to uncertainty metrics. In the case of active tests, there are effects associated with the filtering method used to eliminate the near and far-field effects, as well as other difficulties related to higher Rayleigh-modes or heterogeneities of the site. In this paper, we study the effect of body waves unavoidably induced in active tests on the proper determination of the dispersion curve of a site. For this purpose, active tests are carried out using triaxial geophones to extract from the records the motion effectively corresponding to Rayleigh waves by means of the Normalized Inner Product (NIP) technique. The results show that the effects of body waves are negligible for frequencies above about 8 Hz, but below this value, in the transition zone with ESPAC passive tests, the differences can be more significant. These results are used to introduce uncertainty indicators in this type of explorations

  Abstract
  Geophysical methods based on surface waves have become very popular in recent decades due to their versatility and reduced cost of execution compared to other invasive techniques. [...]

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• Record of long-term field observation of large-scale cutting slope

  S. Hijikata*, R. Kuwano, H. Nakamura

  ISC2024.

  
  

  Abstract

  This paper describes the interpretation of landslide behavior and verification of the effectiveness of countermeasure works based on the results of long-term field observations at a large-scale cutting site. The site has been subjected to various deformations since its construction due to its unique geological conditions, and has been monitored extensively by GPS surface displacement gauges, borehole inclinometers, anchor load cells, and water level gauges as an important monitoring site even after it was put into service. In the sixth year after the site was opened to public use, we assumed underground slip surfaces based on an interpretation of the observed data, constructed additional countermeasures, and verified the effectiveness of the countermeasures through continuous field observation of intermittent landslide behavior observed in several areas of the slope. As a result, it was confirmed that the displacement had not been settled even five years after the construction of the additional countermeasures and that a new slip surface had emerged, indicating the necessity of improving field observation techniques and data interpretation as well as continuous monitoring of this site

  Abstract
  This paper describes the interpretation of landslide behavior and verification of the effectiveness of countermeasure works based on the results of long-term field observations [...]

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