Institute of Hydroengineering

Abstract The paper presents the behaviour of samples made of self-manufactured polydimethylsiloxane (PDMS) grains in a photo-elastic confined uniaxial compression test. PDMS particles were produced using the water-based method, resulting in grain shapes that are close to spherical, with diameters ranging from 2.0 to 16.0 mm. The samples tested were of the same size; however, they consisted of grains of different fractions, diameter spans, and aspect ratios relative to the dimensions of the test box. They were subjected to a load-unload cycle according to several scenarios, first to determine the load that induces a measurable photo-elastic effect. To study the potential relationship between the uniaxial strain calculated based on the change in a sample’s height and the corresponding optical parameters, a parallel analysis was conducted using the average image brightness. It led to the proposal of standardised strain and brightness parameters, which reduced the influence of loading scenarios and camera settings on the test results, allowing for the study of the other factors. On this basis, a unique relationship has been found between normalised uniaxial strain and normalised relative average image brightness, encompassing both loading and unloading regimes. In contrast, two calibration curves are required to calculate stress from brightness. The most interesting finding is that, despite the different force network structures observed in the uniaxial compression test, they do not appear to affect the behaviour of the granular samples on a macro-scale. Graphical abstract

Nonlinear surface waves interacting with rippled seabed can significantly influence sediment transport processes, particularly in coastal environments where the shoreline is covered with bedforms. In such conditions, the transport dynamics of plastic debris become complex, leading to distinctive displacement patterns that are crucial for understanding coastal morphodynamics and environmental impacts. The interaction between waves and bottom ripples increases turbulence, promotes the saltation or suspension of plastic particles and generates ripple vortices, which influence the flow structure within a layer exceeding twice the height of the bottom ripples. In this study, a broad range of regular surface wave cases was analyzed through new experiments conducted in a wave flume with fixed rough beds. The presence of nonlinear surface waves was identified through spectral analysis. Some cases revealed a significant second harmonic in the wave signal, whose intensity was amplified in some tests when passing over the rippled seabed. This nonlinear behavior indicates strong interactions between surface waves and the seabed, which enhance sediment transport mechanisms and, under certain tested wave conditions, lead to a reversal in sediment transport direction. The analysis of nonlinear waves – whose components can significantly influence sediment transport dynamics by modifying orbital velocities near the seabed – helps explain the observed patterns of plastic debris transport during the experimental campaign. Furthermore, spectral analysis suggests that in cases where the transport direction reverses, there is a strong presence of nonlinear surface waves. In some instances, higher harmonic amplitudes are enhanced, resulting in a second harmonic that surpasses the fundamental frequency. • Denser pellets move offshore in velocity-skewed, onshore in accel-skewed waves • Second harmonic in L/h > 10.9 waves linked to onshore transport of pellets • Pellet transport reverses direction when L/h goes above 10.9 • Rippled beds reduce velocity skewness but increase acceleration asymmetry • Full time series Sk and As better describe wave nonlinearity

Safety and location suitability is a vital issue for offshore wind farms and their transmission infrastructure, including cable landing stations. Geomorphological and geological features are one of the key determinants of durability and operational reliability of energy infrastructure. We analyse the dynamics of the coastal zone at the two locations (Ustka and Lubiatowo) planned for the landfall of marine transmission infrastructure on the Polish southern Baltic coast. Average centennial coastal changes were determined by comparing the shoreline from 1875 (1:25,000 topographic map) and 2022 (LIDAR). Statistical rates of change were calculated using DSAS software by analysing changes in shoreline position (1:10,000 topographic maps and LIDAR) over 7 to 8 time intervals between 1985 (1986) and 2022. Over a period of one and a half centuries, in the Lubiatowo landfall area, there was slight local erosion (max. ~80 m; ~0.5 m/yr) and accretion (max. ~90 m; ~0.6 m/yr). In the Ustka area, the situation was similar, but the extent of the changes was greater - the shoreline retreated locally by ~270 m (~1.8 m/yr) and local accretion amounted to ~270 m. Analysis of changes in the position of the shoreline on a timescale of three decades (1985–2022) showed a slight expansion of the erosion areas and a shift of the erosion and accretion centres to the east, as well as higher rates, of both erosion and accretion, compared to the period 1875–2022. Locally, the average erosion rate in the Lubiatowo area was 1.7 m/yr and the average accretion rate locally reached 1.5 m/yr. Similar trends and magnitudes of changes occurred in the Ustka area, where the average erosion rate was 1.6 m/yr and the accretion rate 1.2 m/yr. These examples of erosion-accretion systems show that data on the position of erosion and accretion centres as well as on the rate of change of the shoreline position are strongly dependent on the time intervals analysed. Therefore, it is necessary to analyse not only the current litho- and morphodynamic processes on the coast, but also the trends of change at different time scales, when determining the landfall sites of power cables and as the design of their protection.

ABSTRACTAccurate modeling of soil behavior under seismic conditions is critical for understanding and mitigating earthquake‐induced hazards. In this study, the Dyna–Simhypo model, an enhanced hypoplastic framework incorporating the intergranular strain tensor, is integrated with smoothed particle hydrodynamics (SPH) method for the first time to simulate co‐seismic large deformation processes of slopes. The model's performance is validated through cyclic triaxial tests, seismic wave propagation analysis, and large‐scale seismic slope simulations. Compared to the original Simhypo model, it eliminates ratcheting and reliably captures shear modulus reduction, damping buildup, and progressive soil degradation under cyclic loading. These advancements enable precise site response evaluations and accurate slope instability predictions, offering a robust tool for seismic hazard assessment.

Groundwater resources constitute one of the primary sources of freshwater in semi-arid and arid climates. Monitoring the groundwater quality is an essential component of environmental management. In this study, a comprehensive comparison was conducted to analyze the performance of nine ensembles and regular machine learning (ML) methods in predicting two water quality parameters including total dissolved solids (TDS) and pH, in an area with semi-arid climate conditions. The study area under consideration is an aquifer located in the Sirjan plain, Kerman, Iran. The developed models include standard multilayer perceptron neural network (MLPNN), classification and regression trees (CART), Chi-square automatic interaction detection (CHAID), and their ensemble versions in bagging (BG) and boosting (BT) ensemble structures. The analysis revealed that standard MLs yield comparable results in predicting TDS. The MLPNN, exhibiting a standard root mean square error (SRMSE) of 0.085, demonstrated superior accuracy in predicting TDS when contrasted with CART and CHAID models. Predicting pH poses a greater challenge for the models. Ensemble techniques significantly enhanced the accuracy of regular models. On average, the bagging and boosting techniques resulted in a 22.68% improvement in the accuracy of regular models, which represents a statistically significant enhancement. The boosting method, with an average SRMSE of 0.0602, is more accurate than bagging. Based on the results, the CHAID-BT with SRMSE of 0.0790 and CHAID-BG with SRMSE of 0.0330 are ranked the most accurate models for predicting TDS and pH, respectively. The performance of ensemble techniques in predicting TDS is more remarkable. In practical implementation, ensemble techniques can be considered an alternative method with high accuracy for sustainable water resources management in semi-arid regions, helping to address water shortages, climate change, water pollution, etc.

This paper explores complex mechanisms of force network transformation in granular materials, focusing on micro- and mesoscale levels. DEM simulations reproduce the force chain network observed in a simple photo-elastic experiment to calibrate the numerical model by the sensitivity analysis to different material constants. A best-fit parameter set is determined and applied to simulate the force network evolution, which is difficult to trace in the physical photo-elastic test. The two well-known micro-scale mechanisms, the development and collapse of large pores and activation of micro-shear bands (micro-slips), and their influence on transforming the local force chain network, are confirmed. A third mechanism, not directly described in the literature, called ’switching force chains’ is presented as an original contribution. The evolution of the granular sample’s mechanical state is studied to support the micro-scale analysis.

Abstract The paper is devoted to the long-term project concerning monitoring and stability analysis of a 40 m high phosphogypsum heap located at Wiślinka, Poland. The research presented in the paper focused on collecting and processing rainfall data, which subsequently allows us to perform numerical simulation of rainfall impact on heap’s behaviour. Such analysis requires time history of rainfall intensity, that is recorded by an automatic precipitation station. Since this is not common monitoring equipment, the characteristics of the station installed in the immediate vicinity of the heap are presented, and the data obtained in two experiments conducted in the laboratory are discussed. The analysis revealed that di erences between introduced and measured total rain are as large as 10% for very heavy rains. Moreover, the recorded maximum rainfall intensity often includes errors. The data processing procedure to obtain time history of rainfall intensity is presented on the basis of data collected in the first half of the hydrological year 2023 (the first period of the station’s operation). The total precipitation registered was 107 mm, and the maximum daily rain was only 26 mm. However, first single and multi-stage rainfall models for the Wiślinka region that would be applied into numerical simulations are presented.

Abstract This study aims to determine the geology of granite and evaluate the engineering properties of the samples to make recommendations for the construction industry. The study area is situated in the Nagar Parker complex in Pakistan, which is located in the extreme south-east of the Thar District and the desert of the Sindh Province, near the Run of Kutch (240° 15′–35 30′ N, 70° 40′–58 07′ E), and it covers ca. 500–1,000 km2. In this region, several Quaternary deposits, subordinate and dispersed Jurassic–Tertiary sandstones and clays are overlying the Nagar Igneous Complex basement. According to international standards, there are various possible aggregate sources. However, only a few of them have been reviewed for suitability reasons. Six quarries in Nagar Parker, Pakistan, were selected for evaluation as coarse aggregate in concrete construction and civil engineering works in this research. Although the aggregates from the six quarries are specified and already widely used in the Sindh Province, there is a lack of studies on their geological properties. The results of the presented research revealed that samples from Dhedvero, Karai, Nagarparkar, Mokrio, Dinsi and Wadlai meet all of the international standard requirements for aggregates. Geotechnical, petrographic and geochemistry laboratory tests were conducted in this research and included bulk density, water absorption, specific gravity test, index of flakiness and elongation, soundness aggregate test, crushing value aggregate, impact value aggregate and abrasion value of Los Angeles. Furthermore, chemical alkali-silica reaction potential test and petrographic examination were tested. As a result, we evaluated the properties of granite, which is a crystalline igneous rock with a visibly crystalline structure and texture, made up of feldspar, i.e., potash feldspar and oligoclase. The evaluated minerals are compatible with the standards of civil engineering works and can be used as a concrete aggregate. The evaluated three types of minerals included Dhedvero simple intrusion, Nagar pink granite and grey granite.