Despite the emergence of recent advancements, machine learning (ML) based methods for estimating the fragility curves of structures through probabilistic ground motion selection techniques pose a challenge due to the computational cost associated with data preparation. The primary aim of this research is to reduce the data preparation time involved in estimating the fragility curves of structures using a ground motion selection approach that considers earthquake magnitude, distance from the seismic source, and shear wave velocity of soil as essential parameters. To achieve this objective, ML algorithms are employed to calculate the fragility curves of various reinforced concrete moment resisting (RC/MR) frames with different periods, utilizing codebased and generalized conditional intensity measure (GCIM) ground motion selection methods. The SMOTE-ENN technique, a data resampling method, is used to balance the training data for the ML algorithms to address potential bias resulting from imbalanced training data. To validate the fragility curves obtained through ML, analytical fragility curves are derived for a specific structure at three damage levels and compared with the ML curves. The results demonstrate that the percentage of the enclosed area between the analytical and ML curves, relative to the area under the analytical curve, is below 10 % and 5 % for the GCIM and code-based methods, respectively. Fragility curves were generated for various structures, including regular and irregular buildings, to investigate the generalizability. Results indicate that, for the specific structures analyzed in this study, excluding torsional ones, the structure's period is a sufficient structural feature for generating fragility curves.
Most natural soils exhibit a certain degree of soil structure which, in general, leads to increased strength and stiffness properties. However, the mechanical characterization of these soils based on conventional laboratory testing proves difficult in many cases due to sample disturbance. The present work aims to characterize the microstructure of a postglacial, normally consolidated, fine-grained deposit in Seekirchen, Austria, adopting in situ testing, laboratory testing on high-quality samples, and numerical analysis. The latter involves recalculating in situ piezocone penetration tests (CPTu) using an advanced constitutive model for structured soil. In contrast to existing in situ interpretation methods, the results of the numerical study, the mineralogical and hydrochemical testing, as well as the oedometer and bender element testing on undisturbed and reconstituted samples suggest that the soil is characterized by a significant amount of structure. It is demonstrated that the difference in shear wave velocity measured in situ and through bender element testing on reconstituted samples can be used as an indicator for soil structure. Ignoring the effects of structure may lead to inaccurate parameter determination for advanced constitutive models, which are subsequently employed to solve complex boundary value problems in geotechnical practice. As a consequence, the prediction of expected displacement may not be reliable.
For offshore platforms installed in seismically active regions, maintaining the safety of operations is an important concern. Therefore, the reliability of these structures, under earthquake ground motions, should be evaluated accurately. In this study, reliability methods are applied to determine the probability of failure of jacket platforms against extreme level earthquake (ELE), considering uncertainties in ground motions and the properties of the structure and soil. They are verified by two variance reduction Monte Carlo sampling methods to find the most efficient method in terms of both accuracy and calculation time. During the ELE event, also called strength level earthquake, structural members and foundation components are permitted to sustain localised and limited nonlinear behaviour, so a force-based criterion is utilized for the limit-state function. The results indicate that all reliability methods, except for FOSM, provide a good approximation of the probability of failure. Also, Point-fitting SORM is the most efficient method.
The European earwig F. auricularia L. is an omnivore that has only recently been identified as a direct, fruit-feeding pest of citrus. Here, we start to build the basic tools needed for integrated pest management for this species. We introduce a time-efficient sampling method based on small wooden boards placed on the ground, and we use them in a 2-yr survey of 93 commercial citrus blocks in California's San Joaquin Valley. Insecticides were not applied targeting F. auricularia in any of these citrus blocks. We find that F. auricularia populations are very low or undetectable in most blocks, with higher densities occurring only sporadically. To know when control measures should be implemented, we used video-monitoring of citrus tree trunks to characterize the timing of F. auricularia movement from their soil nests into the tree canopy. Movement of earwigs along the tree trunks was observed throughout our sampling period (22 March to 18 June), suggesting that control measures (sticky bands placed on trunks, or insecticides applied to trunks and surrounding soil surface) should be applied early, well before petal fall when fruit are susceptible to F. auricularia herbivory. Sticky barriers effectively reduced the vertical movement of 2 crawling arthropods, F. auricularia and the Fuller rose beetle Napactus godmanni, along citrus trunks. We failed to find any relationship between estimated F. auricularia densities and damage to maturing or harvested fruit. This highlights a set of important and still unresolved questions about the biology of this species, underscoring the need for additional research.
It is acknowledged that various sources of uncertainties play a vital role in the seismic vulnerability of slope systems, while many studies ignore these sources in seismic assessments. This is because seismic performance and fragility evaluation of large soil-structure systems is challenging and computationally intensive by conventional nonlinear dynamic analysis methods, especially when the modeling uncertainties are considered. To address this challenge, this paper proposes a new framework for addressing uncertainties in the seismic evaluation of earth slopes using the Endurance Time Analysis (ETA) method. The ETA method is a dynamic pushover procedure in which the slope is subjected to a limited number of artificial intensifying records, and seismic responses are obtained over a continuous range of seismic intensities. For the purpose of this study, probabilistic two-dimensional numerical simulations of earth slopes are created using the FLAC software by considering the soil parameters uncertainty. Latine Hypercube Sampling is employed to generate random simulations. The models are then subjected to the intensifying prefabricated excitations based on the ETA method, and the fragility curves of the slope are obtained in three damage states by considering and not considering uncertainties. The results indicate that as the endurance time, which is a kind of intensity measure, increases, the uncertainties of seismic responses also increase. This shows that the effects of uncertainties become more significant when the slope is subjected to strong ground motions. Additionally, the influence of modeling uncertainty is negligible in the slight damage state, but significant in the extensive damage state. The proposed framework provides an effective and rapid way for performing the fragility and associated risk analysis of earth slopes considering uncertainties.
Article delved into the environmental impact of artillery fire, proposing an innovative sampling method for assessing its effects. With a focus on minimizing ecological harm from military operations, particularly in light of the ongoing war in Ukraine, it explained a new approach to defining environmental damage based on the detection of the harmfulness of a specific type of ammunition. The proposed approach offers a more accurate determination of environmental impacts than traditional sampling methods that do not identify the specific agent. The article outlined the first step in addressing artillery environmental impacts by introducing a new crater soil sampling methodology, refined through experimental artillery fires. This method ensures enough samples are collected for valid chemical analysis and identification of soil pollution caused by specific types of ammunition. In addition to the sampling methodology, the article explained the nature of the execution of experimental artillery fire and the necessary considerations in relation to the shape of the crater and defining of its center, which is a necessary step to the layout of the sampling scheme. Applying the method will precisely define the environmental impacts of each projectile type, enabling accurate determination of post-war restoration requirements for artillery-affected areas.
Relevance. Engineering-geological surveys are an integral part of mining operations for various purposes. The quality of soil core sampling has an important impact on the results of engineering geological surveys. At the same time, obtaining a frozen rock core is complicated by an increase in the bottomhole zone temperature, which arises as a result of drilling. As the temperature rises, the physical and mechanical properties of frozen soils change, which leads to a transformation of the mechanism of their destruction and an increase in the likelihood of drilling emergencies. A core obtained under conditions of rising temperature does not allow for a reliably accurate assessment of the properties and structure of soils in their natural conditions. Therefore, there is a need to develop technological and technical means that help maintain the temperature regime of a rock mass under mechanical effect on it. The analysis of the conditions of core drilling in frozen rocks showed that, along with technological reasons, the design of the rock-cutting tool affects the increase in bottom-hole temperature. The article reveals the dependence of the temperature change at well bottom when drilling on the design features of the core rock-cutting tool. Aim. To study the impact of the design features of a drilling core tool on the nature of destruction of frozen soils, represented by loose sedimentary rocks as the most susceptible to changes in physical and mechanical properties with increasing temperature. The study was based on frozen soils that make up the of Yakutia, a large industrial region that requires frequent geotechnical surveys for its development. Objects. Core drilling tool design, mechanism of frozen rocks destruction, conditions for core sampling in frozen soils. Methods. Analytical method, experimental method, production test method. Results. The authors have determined the main directions for the development of core tools for high-quality core sampling in frozen soils. They derived the dependence of the magnitude of the temperature increase at well bottom on the orientation and size of the cutters reinforcing the rock-cutting tool.
As terrestrial resources and energy become increasingly scarce and advancements in deep space exploration technology progress, numerous countries have initiated plans for deep space missions targeting celestial bodies such as the Moon, Mars, and asteroids. Securing a leading position in deep space exploration technology is critical, and ensuring the successful completion of these missions is of paramount importance. This paper reviews the timelines, objectives, and associated geotechnical and engineering challenges of recent deep space exploration missions from various countries. Extraterrestrial geotechnical materials exist in unique environments characterized by special gravity, temperature, radiation, and atmospheric conditions, and are subject to disturbances such as meteoroid impacts. These factors contribute to significant differences from terrestrial geotechnical materials. Based on a thorough literature review, this paper investigates the transformation of geomechanical properties of extraterrestrial geological materials due to the distinctive environmental conditions, referred to as the four unique characteristics and one disturbance, and their distinct formation processes. Considering current deep space mission plans, the paper summarizes the geotechnical challenges and research advancements addressing specific mission requirements. These include unmanned exploration and in-situ mechanical testing, construction of extreme environment test platforms, the mechanical properties of geotechnical materials under extreme conditions, the interaction between engineering equipment and geotechnical materials, and the in-situ utilization of extraterrestrial geotechnical resources. The goal is to support the successful execution of China's deep space exploration missions and to promote the development of geomechanics towards extraterrestrial geomechanics.
The increasing global demand for sustainable agriculture requires accurate and efficient soil analysis methods. Conventional laboratory techniques are often time-consuming, costly and environmentally damaging. To address this challenge, we developed and validated locally calibrated mid-infrared (MIR) spectroscopy models for predicting key soil properties pH, phosphorus (P) and exchangeable cations in soil samples from South Africa's Western Highveld region, using a dataset of 979 soil samples and machine learning algorithms Cubist, partial least squares regression (PLSR) and random forest (RF). A subset of spectra was also submitted to the newly developed Open Soil Spectral Library's (OSSL) prediction models to determine whether global prediction models could be used for local soil property prediction. Accurate predictions for pH, calcium (Ca) and magnesium (Mg), with coefficient of determination (R-2) values exceeding 0.76 were obtained with the local calibration algorithms. The predictions for P, potassium (K) and sodium (Na) did not meet the requirements for reliability. Soil spectroscopic prediction models calibrated with local soils outperformed the corresponding global prediction models considered. The OSSL prediction results were inaccurate, with a RPIQ <1, and consistently underpredicted all soil properties. Furthermore, the OSSL collection of prediction models does not include a pH (KCl) model, the routinely used pH measurement method in South Africa. These findings highlight the importance of local calibration for accurate soil property prediction and underscore the need for regional representation in global spectral libraries. This research serves as the first local calibration of MIR spectroscopy models for the Western Highveld region of South Africa and provides a foundation for future local soil property inference model development. It also serves as a potential starting point for a comprehensive South African soil spectral library that can be contributed to global spectral libraries.
The improper disposal of antibiotics in water bodies and using contaminated wastewater in irrigation severely damage the environment. Despite efforts to monitor these contaminants, effective detection methods are limited. Here, we design and develop a novel microfluidic electrochemical (EC) sensor for on-site detection of trimethoprim (TMP) using a selenite-enriched lanthanum hydroxide (La(OH)(3):SeOx) working electrode and a polyimide (PI)-filter integrated microfluidic channel (MFC), thus termed a mu TMP-chip. For the first time, we introduced a new two-pronged strategy for enhancing TMP detection: i) incorporating selenite into the La(OH)(3) lattice to improve charge transfer properties and ii) using a laser-processed PI filter in the MFC to trap and isolate complex biomasses. Material characterizations confirmed that incorporating selenite into the La(OH)(3) lattice initiated La-O-Se bond formation and enhanced hybridization between the La 4f and O 2p orbitals. This process created holes in the O 2p valence band and improved the charge transfer properties, thus enhancing both sensitivity and selectivity. EC studies confirmed that when the PI filter is not used in the MFC, the mu TMP-chip experiences a 15-45 % drop in efficiency. The scalable mu TMP-chip offers cost-effective, highly reproducible TMP detection in soil and water.