Documents published in Scipedia

• Geotechnical Characterization of Dredged Material from Rio Grande’s Port, Brazil

  I. Soares Ribeiro*, H. Nierwinski, D. Freitas Fagundes, R. Pinheiro Maria

  ISC2024.

  
  

  Abstract

  Dredging works are essential to ensure navigability in Harbors and waterways. However, this crucial activity generates millions of tonnes of waste each year worldwide. Since the disposal of dredged material is responsible for several environmental impacts, entrepreneurs and engineers must find creative uses for it. Therefore, this study aims to characterize a local dredged material to assess its properties and suitability for geotechnical applications. With this knowledge, this paper presents a series of experimental tests on dredged material samples retrieved from Rio Grande's Port, Brazil. The experimental program includes determining Atterberg limits, sieve and sedimentation analysis, pH and SEM analysis, compaction curve, and unconfined compressive strength in a reconstituted state. The results showed that the material is sandy lean clay, with unfavourable strength characteristics for geotechnical work in a raw state. However, with the advent of chemical stabilization techniques, there is potential for enhancing its suitability for geotechnical applications. By exploring methods such as adding binders like lime or Portland cement, the material's strength and stability could be significantly improved, opening up possibilities for its utilization in various engineering projects. This study contributes valuable insights into the potential reclamation and beneficial reuse of dredged material, ultimately aiding in the sustainable management of harbor and waterway dredging operations

  Abstract
  Dredging works are essential to ensure navigability in Harbors and waterways. However, this crucial activity generates millions of tonnes of waste each year worldwide. Since [...]

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• When Did Geotechnical Data Become A Point Of View: A Case Of Numerical Analysis Vs Site Data

  B. Look*

  ISC2024.

  
  

  Abstract

  The construction of a permanent bridge required a temporary bridge parallel to the permanent bridge alignment. Preloading of the permanent bridge abutment occurred under a separate early earthworks contract. That fill was removed, and the temporary structure was constructed. The fill was then replaced behind the abutment. Movement of the southern abutment of the permanent bridge was identified but with a gap of several weeks in survey monitoring due to a XMAS break period. The abutment had moved towards the river and temporary bridge. Potential causes for movement were investigated by additional investigation adjacent to and far away from the temporary bridge piles. Post movement tests carried out included: Dilatometer Testing (DMT) to assess for shear zones (if any) for slope instability, Cone Penetration Testing (CPTu) to assess strength changes (if any) to proximity of piles and new inclinometer readings. INSAR data was also obtained. A 3-D finite element analysis (FEA) carried out by a consultant matched the measured lateral displacements at the adjacent bridge. Based on that correlation, it was concluded that the removal of the close-ended temporary piles was the main cause of the excessive movement, and this initiated a contractual claim. Correlation is not causation. This case study provides a background on the site data and numerical analysis. The FEA did not include much of the site observational and site data post movement. Given the FEA was given the same credence as the site data, this suggests that data is now considered a point of view.

  Abstract
  The construction of a permanent bridge required a temporary bridge parallel to the permanent bridge alignment. Preloading of the permanent bridge abutment occurred under a [...]

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• A CT-based approach to assess sample quality in soft soils

  J. Pineda*, N. Sau, K. Ouyang, M. Arroyo

  ISC2024.

  
  

  Abstract

  The paper discusses the performance of a novel tool based on computed tomography (CT) to evaluate sample quality in soft soils. This new technique is applied to the low-plasticity Mediterranean deltaic deposits found in the region of Castello d’Empuries at the Costa Brava, in Catalonia (Spain). Tube specimens of variable diameters retrieved using open samplers (Shelby) as well as Osterberg-type fixed-piston samplers were scanned in this study. Statistical analysis of the CT images allows to define a quantitative index of sample quality. Sample quality classification based on this new non-destructive CT-based measure compares well with quality classification based on the well-established recompression sample quality index, e/e0.

  Abstract
  The paper discusses the performance of a novel tool based on computed tomography (CT) to evaluate sample quality in soft soils. This new technique is applied to the low-plasticity [...]

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• Paired in situ tests for site characterization and geotechnical design optimization

  D. Berisavljević*, N. Božović, N. Stanić

  ISC2024.

  
  

  Abstract

  The paper shows recent experience in performing and interpreting the three most common in situ tests for site characterization: cone penetration test (CPT), seismic dilatometer test (SDMT) and Menard pressuremeter Test (MPT). It is shown that an adequate selection of in situ test methods for site characterization can be used to correctly predict the pile head load-settlement curve. Menard pressuremeter design rules, which were established in the 1st and a draft version of the 2nd generation of Eurocodes, can be applied to SDMT readings to obtain the pile bearing capacity. It was found that corrected lift-off pressure p0 obtained in the SDMT test is similar to the Menard limit pressure pl in clay, while pressure p1 (SDMT) is similar to pl in sand. All results used in the analysis are obtained on a large-scale project where investigations are strictly controlled and performed in accordance with Eurocode standards.

  Abstract
  The paper shows recent experience in performing and interpreting the three most common in situ tests for site characterization: cone penetration test (CPT), seismic dilatometer [...]

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• On the Effectiveness of MOSTAP Sampling in Tailings

  P. Oelofse*

  ISC2024.

  
  

  Abstract

  The MOSTAP sampling apparatus is a popular tool in geotechnical investigation, since MOSTAP sampling can be done efficiently and cost effectively with the same rig used for CPT testing. Although few publications exist discussing the nuances and application of the MOSTAP sampler in practice, it is generally found that the MOSTAP sampler provides lower quality undisturbed samples when compared to piston tube or block samples. This paper discusses the experiences and learnings from geotechnical investigations where the MOSTAP sampler was employed in platinum and discard sand tailings in Southern Africa. A comparison between different sampler diameters at the same site showed significant improvements in sample recovery with larger diameter samplers. Ancillary equipment such as a core catcher and nylon stockings have significant effects on sample recovery and quality. The soil type and degree of saturation of samples also have a significant effect on sample recovery and sample quality. Transportation and storage of samples were identified as major contributors in moisture loss and sample disturbance. Even with the potential challenges in obtaining a representative sample at depth, MOSTAP samples are shown to be greatly beneficial in evaluating a soil profile and density determination with high confidence, especially when paired with index tests. The opportunity is identified where diligent sample measurement and tracking can provide reliable and invaluable information about a relevant soil stratum. Advanced laboratory testing (e.g., triaxial and oedometer tests) is not recommended on undisturbed MOSTAP samples, these should rather be remolded for critical state line testing, if relevant.

  Abstract
  The MOSTAP sampling apparatus is a popular tool in geotechnical investigation, since MOSTAP sampling can be done efficiently and cost effectively with the same rig used for [...]

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• Combining penetration resistance and shear-wave velocity to quantify soil microstructure for liquefaction assessment

  R. Andrus*

  ISC2024.

  
  

  Abstract

  This paper discusses two ratios involving penetration resistance and shear-wave velocity (VS) that have been proposed for quantifying the influence of microstructure in aged and cemented soils for liquefaction assessment. The first ratio is the small-strain shear modulus (Gmax) divided by the cone penetration test tip resistance (qc). Because Gmax/qc is dimensionless, it can be expressed as a ratio of measured VS divided by a function of qc with velocity units. The second ratio is the measured VS divided by an estimated VS from penetration resistance-VS relationships for relatively young sand deposits (MEVR). The advantages and limitations of both ratios are discussed. The influence of various fines content (𝐹𝐹𝐹𝐹) corrections on 𝑉𝑉𝑆𝑆, penetration resistance-𝑉𝑉𝑆𝑆 relationships, and a relationship between MEVR and the liquefaction cyclic resistance ratio correction factor for microstructure (𝐾𝐾𝐷𝐷𝐷𝐷) is evaluated using two published datasets. The results show the 𝐹 𝐹𝐹𝐹 correction to 𝑉𝑉𝑆𝑆 is minimal in the range for which the correction was derived. The 𝐹𝐹𝐹𝐹 corrections to qc and standard penetration test blow count are significant for silty soils, having a net effect of lowering the penetration resistance-𝑉𝑉𝑆𝑆 relationships and increasing the slope of the 𝑀𝑀𝑀𝑀𝑉𝑉𝑀𝑀-𝐾𝐾𝐷𝐷𝐷𝐷 predictive relationship

  Abstract
  This paper discusses two ratios involving penetration resistance and shear-wave velocity (VS) that have been proposed for quantifying the influence of microstructure in aged [...]

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• Site characterization of large hydropower projects

  T. Trick*, K. Kontar, G. Klee, M. Stolz

  ISC2024.

  
  

  Abstract

  Hydropower plays an important role in the context of the energy transition contributing to the reduction of the CO2 emission through a permanent power production as run-of-river scheme as well as for energy storage as pump-storagescheme. Nowadays large hydropower plant designs comprise tunnel, cavern and shaft excavation work known as head race and pressure tunnel or pressure shaft. The powerhouse is often placed within a large underground cavern. The results of a ground investigation phase including the determination of in-situ parameters derived from tests in boreholes drilled from the surface are crucial for a preliminary design of the hydropower plant. Additional in-situ measurements are frequently carried out within an exploratory tunnel to confirm the first predictions and to characterize in detail the mechanical and hydraulic properties of the rock mass. Solexperts portfolio of in-situ well tests comprise the assessment of hydraulic properties vs. depth through hydraulic testing of isolated borehole sections along the borehole axes, the determination of geomechanical parameters like deformation- and Young’s modules through borehole dilatometer tests and rock stress measurements conducting hydraulic mini-frac tests. Plate load tests which use surficial loading are performed in small tunnels or test adits to measure the deformation characteristics of a rock mass on a larger scale.

  Abstract
  Hydropower plays an important role in the context of the energy transition contributing to the reduction of the CO2 emission through a permanent power production as run-of-river [...]

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• Ground Model Workflow with DAARWIN

  I. Jaqués, C. Cano, J. Llopart*, B. Solà, I. Aliguer

  ISC2024.

  
  

  Abstract

  Structural geological models are used to understand and visualize how geological materials are organized below the Earth surface. This technique is crucial in different fields of geomechanics such as mining to identify mineral deposits and to plan mining operations, environmental engineering to assess the contamination of soil and groundwater and to design remediation strategies, and civil engineering to design foundations, tunnels and other underground structures. In this sense, ground models allow the engineer to understand and to visualize the spatial organization of subsurface geological structures and, additionally, it is possible to evaluate the spatial distribution of material properties which is essential in any geomechanical study prior to any project. In this context, SAALG Geomechanics through DAARWIN web platform provides a suitable software tool for the geotechnical engineer to perform the complete ground model workflow. The process starts introducing borehole data from different sources and then, the engineer can visualize and interpret borehole logs, define geomechanical units and assign parameters from in-situ and laboratory tests, as well as assign units’ geometry from geological layers. Finally, the user can feed this information to the system to obtain a 2D cross-section, that can be exported to the commercial Finite Element software PLAXIS and use this PLAXIS model for geotechnical design and more advanced analyses such as Sensitivity analysis and Back-Analysis, which are also implemented in DAARWIN.

  Abstract
  Structural geological models are used to understand and visualize how geological materials are organized below the Earth surface. This technique is crucial in different fields [...]

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• Combined resistivity and seismic measurements along linearly extended earth structures - acquisition and interpretation approaches

  C. Comina*

  ISC2024.

  
  

  Abstract

  Geotechnical parameters of linearly extended earth structures, such as embankments and earth dams, are usually obtained from localized investigations through drilling or penetration tests, commonly time and cost consuming. Non-invasive geophysical investigations may be considered an alternative approach for the geotechnical characterization of these structures, given their surveying speed and their depth and length of investigation. Particularly, new acquisition approaches with the use of appropriate streamer cables could strongly reduce the acquisition times making geophysical surveys ideal for a preliminary screening of these structures. Specifically, resistivity and seismic methods can be adopted given that these two methodologies could offer complementary information with respect to the pore fluid properties (resistivity methods) and the solid skeleton characteristics (seismic methods). Also, through specific correlations, relevant geotechnical parameters for the evaluation of the stability of these structure and its efficiency (i.e. hydraulic conductivity, porosity and others) can be obtained. In this paper a review of the methodologies developed in recent years for data acquisition along linearly extended earth structures is reported with special focus on the use of combined electric and seismic streamer cables. Suggestions with respect to interpretation approaches and data elaboration are also analysed.

  Abstract
  Geotechnical parameters of linearly extended earth structures, such as embankments and earth dams, are usually obtained from localized investigations through drilling or penetration [...]

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• Long-Term ERT Monitoring Data Analysis to Set Slope Instability Attention Thresholds Based on Water Level Fluctuations

  R. Bianchi*, F. Brambilla, A. Hojat, G. Tresoldi, L. Zanzi

  ISC2024.

  
  

  Abstract

  In this paper, we discuss the results of long-term electrical resistivity tomography (ERT) monitoring of a critical slope located on an important high-speed railway gallery. Data were acquired by a customized ERT system from 24 March 2022 until 31 august 2023 and were analysed with the final objective of defining thresholds of attention for resistivity changes derived from water table fluctuations after heavy rainfalls. This helps the authorities in reducing the hydrogeological risk impacts related to potential slope instabilities triggered by extreme meteorological conditions. In order to continuously observe water level changes, five piezometers were also integrated with the ERT monitoring system which is also accompanied by a meteorological station. All datasets were inverted using a time-lapse algorithm that was optimized to minimize artifacts generated by the subsurface complex geology of the site. Due to the long period considered, seasonal temperature corrections on resistivity values were also explored by calibrating a seasonal model of soil temperature versus depth and evaluating the corresponding effects on the resistivity tomographic maps. Finally, the correlation between resistivity values and piezometric levels was studied by producing scatterplot graphs for a selected subzone of the ERT sections. Based on this analysis, a preliminary threshold of attention was defined.

  Abstract
  In this paper, we discuss the results of long-term electrical resistivity tomography (ERT) monitoring of a critical slope located on an important high-speed railway gallery. [...]

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