Abstract in English:

Abstract Shaft excavation is essential in modern cities, allowing for quick and direct access to the underground, where most transportation networks and utilities are being installed to reduce surface congestion. Selecting the appropriate construction methodology is critical to minimize ground movements, while ensuring structural stability and construction efficiency. This study assesses the performance of three typical construction methodologies – Excavation Before Support (EBS), Support Before Excavation (SBE) and Dual-Lined Shafts (DLS) – through a comprehensive numerical study. The validation of the adopted modelling approach for each methodology is performed by simulating three case studies in close proximity to each other. Several aspects of numerical modelling are discussed, such as the simulation of the hardening behavior of the sprayed concrete, the modelling the wall installation and their stiffness anisotropy. For each methodology, the influence of key variables is assessed through parametric studies, highlighting the importance of the excavation step height, the lining thickness and the embedded length of the wall. A final study, where all methodologies are compared for the same ground conditions, is carried out for two shaft diameters. Results indicate that SBE produces the smallest ground movements but induces the highest lining forces. In contrast, EBS originates higher ground movements due to significant soil decompression but smaller lining forces. DLS methodology exhibits an intermediate behavior, although more similar to that observed in EBS. These findings emphasize the importance of selecting an adequate shaft construction methodology and provide valuable information regarding the appropriate numerical simulation of each technique.

Abstract in English:

Abstract Ensuring dam safety requires continuous monitoring to detect structural anomalies such as cracks, displacements, and seepage. This study explores aerial surveys using Unmanned Aerial Vehicles combined with open-source software to enhance dam monitoring capabilities. The methodology enables efficient inspections in difficult-access areas and supports early identification of potential failure indicators. High-resolution aerial imagery was processed to generate detailed three-dimensional representations including point clouds, orthophotos, and textured models. A novel Ground Control Points Finder tool was developed to automate identification and georeferencing, significantly improving spatial accuracy and survey efficiency. The study systematically presents fourteen failure modes detectable through aerial mapping, including piping, hydraulic fracturing, foundation instability, and freeboard loss, with their characteristic surface manifestations. The approach was validated using Lapa Dam as a case study through two aerial surveys conducted ten months apart. Analysis using open-source software successfully identified surface deformations, settlements, and vegetation changes, demonstrating the methodology's effectiveness in detecting structural anomalies associated with potential failure modes. The results confirm that integrating aerial surveys with open-source processing tools offers a low-cost solution to complement dam safety assessments. The approach improves early detection of various failure modes, reduces inspector exposure to hazardous conditions, and supports informed decisions in monitoring embankment dams through accessible technology.

Abstract in English:

Abstract This article presents an investigation into the influence of swell on the behaviour of large-scale free-ended piles installed in an unsaturated expansive clay deposit when subjected to lateral loading. A ‘dry’ pile was founded in a profile kept at natural water content conditions, and a ‘wet’ pile was founded in a profile which was flooded for six months to allow swelling of the clay prior to testing. Load cycles under two different load magnitudes were applied to the piles, followed by monotonic loading to failure. The applied load, pile head displacement and bending strain distributions with depth (determined using fibre Bragg gratings) were recorded during these tests. The behaviour under 113 kN load cycles was similar for the two piles, with the ‘wet’ pile exhibiting marginally stiffer response. This was attributed to a swell-induced increase in lateral stress acting against the pile shaft. Under load cycles of 145 kN and during the monotonic test, the ‘wet’ pile exhibited a substantially softer response and significantly lower ultimate capacity than that of the ‘dry’ pile. This was attributed to the effects of swell-induced softening and the reduced yield stresses in the swelled clay. These phenomena were interpreted with reference to a site investigation programme including seismic continuous surface wave tests and standard penetration tests, as well as some laboratory testing. Effects of local yielding of the bonded material at fissure interfaces upon pile ratcheting during cyclic loading have also been discussed.

Abstract in English:

Abstract Significant quantities of site won fill material are generated from the High Speed Two (HS2) C23 main works civil engineering contract, during the excavation for the formation of cuttings and construction of tunnels. This study investigates the suitability of weathered structureless Chalk, stabilised with cement, for use as engineered embankment fill for high-speed rail earthworks. Given the dynamic loading conditions imposed by high-speed high frequency rail operations, the performance of stabilised chalk requires thorough evaluation. A strategic field trial embankment was constructed to assess the suitability of this material. The results demonstrate that the static stiffness modulus (EV2) of the stabilised chalk meets HS2’s minimum performance requirements, though it is found to be sensitive to cement curing time. Dynamic performance, evaluated through shear wave velocity (Vs) derived from Rayleigh wave characteristics, exceeded the minimum Vs assumed for engineered fill during detailed design, confirming compliance with HS2’s dynamic performance criteria. Construction control measures, including optimal chalk grade, binder mix, moisture content, and compaction control are recommended to ensure consistent performance. These findings validate the use of cement-stabilised chalk fill for high-speed rail earthworks, enabling the development of sustainable earthwork solutions through material optimisation, waste reduction, and enhanced environmental efficiency.

Abstract in English:

Abstract Most gravity dam failures occur due to sliding along the dam/foundation interface, rock mass discontinuities, or rock mass layers of lower strength. The possibility of sliding of a dam is usually evaluated based on simplified limit equilibrium techniques. In this study an explicit time-stepping small displacement algorithm, Parmac2D-Fflow, is used to assess the safety of gravity dams. This algorithm is based on a discrete representation of discontinuities, simulates the hydromechanical interaction, and considers softening constitutive laws that are closer to the actual behaviour of the dam/foundation interface. Seepage flow along the dam/foundation interface is only allowed to occur after contact failure, making it possible to model a coupled propagation failure along the dam/foundation interface due to a hypothetical dam overtopping scenario. For two gravity dams with different heights, the numerical results predicted with a coupled/fracture propagation model are compared with those obtained with a coupled/fully fractured model and with an uncoupled analysis. The results presented highlight the relevance of considering a coupled hydro-mechanical model for dam safety analysis and show that with a coupled-fracture propagation model slightly higher safety factors are predicted.

Abstract in English:

Abstract Clayey soil in its natural state usually has a low bearing capacity, high compressibility, and high sensitivity to changes in water content. These properties represent an obstacle to the use of this type of soil in construction industry projects, so it is necessary to stabilize it before its application for construction purposes. This paper presents the results of a comparative study of the effects of chemical stabilization of clayey soils on improving soil properties by considering a variety of chemical reagents. In addition to commonly used chemical reagents such as calcium carbonate (lime), alternative materials such as magnesium carbonate, sodium silicate, and potassium hydroxide were also considered. With an aim to determine the optimal content of reagent in a mixture with clayey soil, each of the selected chemical reagents was considered with three different percentage shares in the mixture. Given that the permanent improvement of soil properties is of utmost importance in geotechnical engineering, for this purpose, changes in the crucial physical and mechanical properties of the treated clayey soil (Atterberg limits, unconfined compressive strength, and shear strength) were also monitored over time after the chemical treatment. The research results revealed that the selected chemical reagents have different efficiencies on the considered physical and mechanical properties of clayey soil, whereby each of them contributed to the soil improvement. This opens up the possibility of applying the selected stabilizers within the framework of the chemical soil stabilization technique, primarily in the field of roadway construction.

Abstract in English:

Abstract The development of the construction sector in recent decades and the systematic reduction of natural aggregate (NA) resources have obliged the search for alternatives and substitutes for these essential construction materials. Using anthropogenic aggregates as replacements for natural aggregates provides an opportunity to reduce landfills by recycling waste materials from construction and demolition (CDW), for civil engineering applications. It may also involve risks that undoubtedly include estimating geotechnical parameters based on solutions developed to date for natural aggregates. A significant factor affecting these estimates is that anthropogenic aggregates could have different properties and chemical compositions. This study analyzed the possibility of estimating the coefficient of permeability for recycled concrete aggregate (RCA) using machine learning algorithms - AdaBoost and artificial neural networks. The AdaBoost model demonstrated higher accuracy (R2 was 0.959 for training data and 0.886 for test data), relative to neural networks (R2 was 0.682 and 0.640). Shapley Additive Explanations (SHAP) analysis, which increased the interpretability of the results, showed that AdaBoost better reflected the influence of hydraulic properties such as gradient or bulk density, while the neural networks were more sensitive to aggregate grain size. The results indicate the effectiveness of machine learning algorithms in evaluating the coefficient of permeability for recycled materials and represent a promising perspective for supporting the design of sustainable construction solutions.

Abstract in English:

Abstract To determine the influence of soil-structure interface behavior on the bearing capacity and deformations of geotechnical structures, suitable testing methods capable of simulating in situ conditions are required. This article introduces a novel test method for soil-structure interface tests. A hollow cylinder device is modified to conduct interface tests with four independent control variables. This enables investigations of the influence of different anisotropic stress states on the contact shear behavior of granular material. First test results on Karlsruhe fine sand are presented with a variation of the lateral normal stresses acting on the plane orthogonal to the shear (i.e., contact) plane. These tests are conducted in two modes: in mode A long samples (do=h) are used whereas in mode B short samples 2do−di=1/h are used. The results of the test series in mode A show that the failure occurs either in the soil (on the plane with the highest ratio of the shear and normal component of the stress vector τ/σN) or on the contact plane (where the shear strength is reduced). The failure in the test series with mode B is restricted to the horizontal plane due to sample geometry. The findings will be utilized in the future to test and develop various modeling methods for soil-structure interfaces.

Abstract in English:

Abstract Reliability and safety assessments require optimizing decision-making throughout the lifecycle of systems such as the “soil mass – underground structure” system. Changes in the engineering-geological environment cause various geohazards that must be identified and evaluated during the project development stage, taking into account both natural and anthropogenic factors related to subway construction and operation in dense urban environments. This article presents an analysis of shaft structures for the proposed Vienna metro line using numerical and probabilistic modeling, with particular emphasis on the quality of input data, their probabilistic variability, and their influence on the stress-strain state of the structures. Finite element modeling was performed using the PLAXIS software package, employing advanced elastoplastic Hardening Soil (HS) and Hardening Soil Small (HSS) ground models. By repeatedly varying initial soil parameters surrounding reinforced concrete tunnel structures, variation coefficients for key loads and deformations in both the structures and soil mass were obtained, which can inform the design of similar structures in the future. A methodology and algorithm for assessing the reliability of the “soil mass – underground structure” system were proposed, based on the Monte Carlo statistical method. The evaluation criterion is the probability of exceeding threshold values of additional vertical settlement after tunnel excavation in unfinished sections of the Vienna metro. This approach enables the prediction of additional deformations affecting the foundations of existing buildings impacted by tunneling. Finally, regression analysis was conducted to assess the influence of varying factors on stress-strain parameters derived from FEM calculations, using both linear and multivariate models.

Abstract in English:

Abstract Slope failures due to erosion effect are a well-established cause of civil engineering structure disasters. Streams passing at the toe of a slope are a severe threat to geotechnical safety, especially in urbanized areas. To increase global safety, a retaining wall is usually proposed to limit the risk of failure. However, such works could also bring the high danger of a landslide during the construction works if not managed properly. The paper aims at investigating the collapse cause of residential buildings located at the edge of the slope at northwest part of Vietnam, where engineering works were performed to prevent failure due to soil erosion at the toe of the slope. During the retaining wall construction works, the applied excavation method caused significant vibrations and additional dynamic loads that could have affected the bearing capacity of the building foundations. Another cause of failure is associated with heavy precipitation recorded at the site just before the excavation works down the slope. The paper consists of numerical analyses allowing simulation of possible scenarios, including the effect of changing groundwater conditions using the meteorological data collected from the nearby monitoring weather station. The computations were performed using geotechnical software to reflect the in-situ conditions, and the entire process of earthworks performed at the site was carefully analyzed. The numerical analyses involved computations performed for a reinforced slope where a retaining wall was proposed to assure geotechnical safety of the remaining infrastructure after the failure.

Abstract in English:

Abstract Two instrumented preliminary test piles have been installed and tested in Aylesbury, UK, using Osterberg Cell bi-directional load test method, for the purpose of verifying the construction methodology and load performance of the bored piled foundations designed for the 880m long HS2 Thame Valley Viaduct. The local ground conditions comprise stiff clay and mudstone of Ampthill Clay, West Walton and Oxford Clay Formations which constitute part of the Ancholme Group. The significant length of the asset allowed a comprehensive ground investigation package of site and laboratory testing to be undertaken in developing a refined detailed design in accordance with the recommendations of Eurocode 7. The field test results of the two test piles have been interpreted and back-analysed using 3D finite element analyses undertaken to simulate the bi-directional loading of the Osterberg Cell testing method and compared against the ultimate pile capacity estimated during detailed design of the viaduct. Subsequent simulation of the pile loaded from pile head level using the calibrated finite element model provided the required load-settlement characteristic necessary to verify the performance of the pile under serviceability limit state.

Abstract in English:

Abstract Drilling boreholes for geotechnical purposes such as sampling, in-situ tests and permeability testing are usually performed with the aid of drilling machines. These heavy duty machines generally use internal combustion motors to provide energy to hydraulic pumps feeding the different actuators needed to push, rotate and hammer the drill bit into the ground. This results in a relatively noisy and polluted environment for the workers and the surrounding area. With the popularization of electric vehicles, it’s time drilling machines also make the switch to electric power. This paper presents one such prototype machine developed by Fondasol company, with the initially proposed technical specifications and the realized equipment. Autonomy for up to one week has been observed on real sites, depending on the project’s drilling objective. The use of electric motors allows for a new type of measuring while drilling, as the measurement of electric current and voltage is much more reliable than hydraulic pressure and flow rates. With this electric-based design, additional external sensors are no longer necessary. A first insight into this new type of measurements and its physical meaning is also given and discussed within this paper.

Abstract in English:

Abstract The present era is defined by the advent of big data, where large volumes of data are generated and stored daily. However, the true challenge lies in transforming this data into meaningful and actionable information. To extract insights from these vast datasets, there is a growing dependence on data-driven methods, many of which build upon traditional statistical foundations. These techniques enable the creation of models that enhance our understanding of diverse subjects and facilitate informed decision-making. This study focuses on the establishment and exploration of a database derived from dynamic load tests on piles (DLT). In DLT on piles, impact hammers are employed, characterized by their potential energy or kinetic energy just before impact. Testing on high-capacity drilled deep foundations presents several challenges, including the need for sufficient energy to mobilize compressive static resistance of the pile. The investigation delves into understanding the correlation among various DLT test variables and uncovering potential relationships using statistical models, such as linear and non-linear regression. The findings from this exploration have unveiled crucial insights, such as the influence of diameter on pile compressive resistance and stiffness and also the existence of a non-linear relationship between resistance and the maximum energy transferred to the pile.

Abstract in English:

Abstract Liquefaction induced by earthquakes causes instability of buildings such as large average and/or relative settlements. Such occurrences can lead to damage to the building structures. Usually, when an earthquake occurs, saturated loose sandy ground is the most susceptible to liquefaction. Even for saturated silty ground with small SPT N-values, the possibility of liquefaction needs to be considered in the design process of the foundation. Tender Net Foundation (TNF) is a kind of shallow foundation with a combination of grid-shaped soil improvement to depths of 2 to 3 meters, concrete slab, and concrete single footings. In this paper, the dynamic analysis of an actual TNF on the silty ground subjected to three consecutive earthquakes was conducted. Measurements of the settlements of the TNF were initiated after the second earthquake. The silty ground was modeled by the UBC3D-PLM model. The ground accelerations recorded about 10 km away from the site area were used as the input accelerations in the dynamic analyses. The responses of the TNF as well as the ground during and after the earthquakes were analyzed. The numerical analyses simulated the measured settlements well. Furthermore, a comparison was conducted between the TNF and the conventional shallow foundation to demonstrate the advantages of the TNF in reducing the average and differential settlements.

Abstract in English:

Abstract Many flood protection levees in Europe were built more than 100 years ago. These levees often do not meet the current flood protection requirements due to increased level of safety requirements, higher damage potential in the valley plains and due to higher peak discharges or water levels expected with changing climatic conditions. A first series of centrifuge tests on two idealized cross-sections of the river Rhine flood protection levee have been carried out in the geotechnical centrifuge at Delft University of Technology in order to study the transient seepage behaviour of a horizontally layered levee consisting of layers with coarse and fine-grained material. Main features and design considerations of a specially manufactured flood simulator for the geotechnical centrifuge which allows replicating scaled flood events with predefined durations and intensities are presented. Furthermore, measured values of the pore pressure during the investigated flood event are reported and discussed in comparison to the results of finite element modelling of the levee. Finally, the potential impacts of the hydraulic boundary conditions on the seepage behaviour in the physical and numerical models of the levee are critically discussed.