Hasil untuk "Hydraulic engineering"

GUO Li-jin, CHEN Jian-zheng

[Objective] The time series of reservoir water quality indices,especially dissolved oxygen content, exhibit strong nonlinearity,high complexity,and uncertainty,which lead to insufficient accuracy of single prediction models.This study aims to construct a high-precision hybrid prediction model that integrates time series decomposition,intelligent optimization,and residual correction,thereby significantly improving the prediction accuracy of dissolved oxygen (DO) content and providing reliable support for water environment management and pollution early warning. [Methods] The core procedures of the proposed hybrid prediction model are as follows. 1) Data decomposition and reconstruction. Singular spectrum analysis (SSA) was applied to decompose the dissolved oxygen time series, and the series was reconstructed into trend components, periodic components, and residual components to reduce sequence complexity and highlight features at different frequencies. 2) An improved dung beetle optimizer (IDBO) which integrates piecewise chaotic mapping and opposition-based learning strategies was designed to enhance population diversity and initialization quality. The improved IDBO was used to optimize key hyperparameters of the GRU network, including the number of hidden layer neurons and the initial learning rate. 3) Component prediction and residual correction. The GRU model optimized by IDBO was used to predict the trend component and periodic components separately. A residual series prediction difference correction method (DCM) was proposed. The residual component was first predicted using GRU, and the difference sequence between the predicted values and the observed values was calculated. Variational mode decomposition (VMD) was then applied to the difference sequence to fully extract high-frequency detail information. Each decomposed component was predicted using GRU and aggregated to obtain the predicted difference values. Finally, the predicted differences were compensated into the initial residual prediction to obtain the corrected residual prediction results. 4) Model integration and validation. The prediction results of the three components were aggregated to obtain the final DO prediction values. Measured dissolved oxygen data from Daheiting Reservoir in Tangshan, Hebei Province were used for experiments. The dataset contained 2352 records with a sampling interval of four hours. Root mean square error (RMSE), mean absolute error (MAE), mean relative error (MRE), and the coefficient of determination (R2) were used as evaluation metrics. The proposed model was compared with GRU, SSA-GRU, SSA-DBO-GRU, SSA-IDBO-GRU, and models reported in the literature such as LSTM and PSO-GRU. [Results] The proposed SSA-IDBO-GRU-DCM hybrid model achieved the best performance among all comparative models. The prediction errors were significantly reduced, with an RMSE of 0.580 2 mg/L, an MAE of 0.329 2 mg/L, an MRE of 0.0269, and an R2 of 0.918 8. Ablation experiments confirmed that the proposed IDBO improvement strategies effectively enhanced hyperparameter optimization accuracy. The residual difference correction method (DCM) significantly improved the prediction performance of the residual component and was the key factor contributing to the overall accuracy improvement. These results fully demonstrated the effectiveness and superiority of the “decomposition-optimization-correction” framework. [Conclusion] SSA effectively decouples the complex characteristics of water quality time series. IDBO efficiently and accurately optimizes GRU hyperparameters. The proposed VMD-GRU-based residual difference correction method (DCM) is the key innovation for improving overall prediction accuracy. The proposed model significantly improves the prediction accuracy of dissolved oxygen content and provides an efficient and reliable new approach for reservoir dissolved oxygen prediction. Future work can extend this framework to the prediction of other key water quality parameters such as ammonia nitrogen and total phosphorus, and further explore the integration of natural evolutionary strategies to improve computational efficiency and generalization ability.

Qingzhong ZHU, Wei XIONG, Dingwei WENG et al.

Currently, unconventional reservoirs are characterized by low single well-controlled reserves, high initial production but fast production decline. This paper sorts out the problems of energy dispersion and limited length and height of main hydraulic fractures induced in staged multi-cluster fracturing, and proposes an innovative concept of “energy-focused fracturing development”. The technical connotation, theoretical model, and core techniques of energy-focused fracturing development are systematically examined, and the implementation path of this technology is determined. The energy-focused fracturing development technology incorporates the techniques such as geology-engineering integrated design, perforation optimization design, fracturing process design, and drainage engineering control. It transforms the numerous, short and dense hydraulic fractures to limited, long and sparse fractures. It focuses on fracturing energy, and aims to improve the fracture length, height and lateral width, and the proppant long-distance transportation capacity, thus enhancing the single well-controlled reserves and development effect. The energy-focused fracturing development technology has been successfully applied in the carbonate reservoirs in buried hill, shallow coalbed methane reservoirs, and coal-rock gas reservoirs in China, demonstrating the technology’s promising application. It is concluded that the energy-focused fracturing development technology can significantly increase the single well production and estimated ultimate recovery (EUR), and will be helpful for efficiently developing low-permeability, unconventional and low-grade resources in China.

Aldo Antonio Castañeda-Villanueva

La principal fuente de abastecimiento de agua potable en la mayoría de las regiones administrativas del estado de Jalisco (México) son los acuíferos subterráneos, que en muchos casos son de origen hidrotermal, los cuales se caracterizan por la presencia de compuestos químicos potencialmente nocivos para la salud humana y animal. El área de estudio de este trabajo se ubica en el noreste del estado de Jalisco, que comprende 10 municipios en dos regiones administrativas. El presente estudio tiene como objetivo determinar la tendencia de la concentración de flúor en pozos profundos que abastecen de agua potable a los municipios del área de estudio, a partir de dos evaluaciones realizadas durante los años 2021 y 2022. En los resultados se puede observar una tendencia creciente en la concentración de flúor de la mayoría de los pozos analizados en los periodos estudiados; las mayores concentraciones se reportan en las localidades de Tepatitlán, Arandas, Mexticacán y San Miguel el Alto, así como en los municipios de Valle de Guadalupe y Cañadas de Obregón; el uso de estas fuentes como agua potable representa un mayor riesgo para la salud de la población local, lo que ratifica, asimismo, una tendencia creciente en la concentración de fluoruros en las aguas subterráneas extraíd del área de estudio; una posible causa es la continua disminución en el nivel dinámico de extracción que presentan la mayoría de los pozos evaluados. Es necesario implementar programas y estrategias para garantizar la sostenibilidad de este recurso vital en ésta y otras regiones del país.

Chen Zhuang, Hongbo Zhao, Yuli He et al.

High-precision positioning methods have drawn great attention in recent years due to the rapid development of smart vehicles as well as automatics driving technology. The Real-Time Kinematic (RTK) technique is a mature tool to achieve centimeter-level positioning accuracy in open-sky areas. However, the users who drive under dense urban conditions are always confronted with harsh global navigation satellite system (GNSS) environments. Skyscrapers and overpasses block the signals and reduce the number of visible satellites, making it difficult to achieve continuous and precise positioning. Considering that the road is relatively smooth in most urban areas, vehicles are expected to travel on the same plane when they are close to each other. The road plane information is a promising candidate to enhance the performance of the RTK method in constrained environments. In this paper, we propose a plane-constrained RTK (PCRTK) method using the positioning information from cooperative vehicles. In a vehicle-to-vehicle (V2V) network, the positions of cooperative vehicles are used to fit a road plane for the target vehicle. The parameters of the plane fitting are treated as new measurements to enhance the performance of the float estimator. The relationship between the plane parameters and the state of the estimator is derived in our study. To validate the performance of the proposed method, several experiments with a four-vehicle fleet were carried out in open-sky areas and dense urban areas in Beijing, China. Simulations and experimental results show that the proposed method can take advantage of the plane constraint and obtain more accurate positioning results compared to the traditional RTK method.

Andressa Adna Cavalcante Morais, Adelena Gonçalves Maia

ABSTRACT This study verified the suitability of using precipitation forecasts in defining operation rules for the Cruzeta reservoir in Rio Grande do Norte, Brazil. The operation rules were developed through reservoir operation simulation–optimization, using a genetic algorithm. The performance indicators were analyzed in five operation scenarios: standard operating policy (SOP), current reservoir rationing rule (C), rationing without forecast (R), rationing with forecast (RF), and rationing with perfect forecast (RPF). The SOP scenario better met the total demand but made the system very susceptible to supply collapse. The results of the RF and RPF scenarios showed better compliance with the priority demands and the total demand during the dry periods. Changing from RF to RPF scenario, there is a small improvement in the evaluation indexes. The use of rules integrating the seasonal weather forecast is thus recommended.

Xianzhou Lyu, Zeng-hui Zhao, XiaojieĀ Wang et al.

Fractured rocks are a type of complex media that widely exist in various projects including energy, hydraulic, and underground space engineering, whose permeability properties are a hotspot in current rock mechanics domain. Aiming at investigating the seepage characteristics of the fracture surfaces in different rock strata, uniaxial compressive test and permeability test were performed on single-fracture homogenous and heterogeneous rocks. Specifically, rock’s physical and mechanical parameters were measured in uniaxial tests while the initial width of the single fracture was determined through CT scanning. In combination with test results and the calculation model of the displacement of single-fracture heterogeneous rock under triaxial stress condition, the calculation formula of the permeability coefficient of single-fracture heterogeneous rock was derived. Results show that hydraulic pressure in the fracture can affect the permeability coefficient of the fractured rock. Hydraulic fracturing effect occurred with the increase of hydraulic pressure in the fracture, which then generates slight normal deformations of the rock masses on both two sides of the fracture surface, decreases the contact area in the fracture, and leads to the increases of both fracture width and permeability coefficient. For single-fracture rock, the lithological properties of the rock masses on both two sides of the fracture surface impose significant effects on the permeability coefficient. Under same hydraulic pressure and confining pressure, the permeability coefficient of single-fracture coarse sandstone is greatest, followed by that of single-fracture heterogeneous rock, and finally by single-fracture fine sandstone. Theoretical calculation results agree well with the test results, suggesting that the derived theoretical formula can adequately describe the variation tendencies of permeability coefficient with confining pressure and hydraulic pressure in the fracture.

H. V. Häfen, N. Goseberg, Jacob Stolle et al.

AbstractDam-break waves are commonly used throughout the field of hydraulic engineering. Given the availability of several well-developed analytical solutions, as well as the relative ease with whi...

W. Maherzi, M. Benzerzour, Y. Mamindy-Pajany et al.

Gui-Jing Zhang, Jie Liu, Yi Li et al.

A. M. A. D. Silva, M. Ebrahimi

Alpay Serafettin, Iphar Melih

Deciding on equipment from a set of feasible alternatives for excavation purpose in open pit mines is a critical task for the engineers and contractors since it considerably affects the project costs and productivity. Alternatives of rock excavation equipment, which are deemed suitable for the diggability of rock units in open pits, can have many technical specifications or factors that should be considered simultaneously. It can be successfully selected in a scientific way by employing multi-criteria decision making methods by means of taking the advantage of engineering knowledge, intuition and past experiences. In this study, we select the most convenient hydraulic excavator for a magnesite mine by fuzzy multi criteria decision making methods: fuzzy TOPSIS and fuzzy VIKOR. The fuzzy approach allows the experienced engineers to compare the multiple criteria (technical factors) and the possible alternatives of rock excavation machines by simply using linguistic expressions in their natural language.

Saeed Memari, Seyed Mostafa Siadatmousavi

Desalination plants have become invaluable solutions especially where freshwater resources are scarce. However, the byproduct of their operation is an outflow which is more saline and heated than the ambient water body. This heated plume adversely affects the ecosystem if it is not treated properly. In this study, 3D finite volume coastal and ocean model is employed to address this issue close to Qeshm Island. In addition to calibrating the model, two alternatives are simulated and discussed to mitigate the adverse effects of the heated plume. It is shown that the plume tends to move in the upper layer of the water column due to its lower density than the ambient water. By moving the outfall to deeper parts of the sea—10-meter-deep—the negative effects of the plume significantly decreases and fulfilled the Iran national guidelines. Moreover, due to the mechanism of the Qeshm desalination plant, the spread of salinity is of the least importance compared to the increase in temperature.

G. Hattori, J. Trevelyan, C. Augarde et al.

Extracting gas from shale rocks is one of the current engineering challenges but offers the prospect of cheap gas. Part of the development of an effective engineering solution for shale gas extraction in the future will be the availability of reliable and efficient methods of modelling the development of a fracture system, and the use of these models to guide operators in locating, drilling and pressurising wells. Numerous research papers have been dedicated to this problem, but the information is still incomplete, since a number of simplifications have been adopted such as the assumption of shale as an isotropic material. Recent works on shale characterisation have proved this assumption to be wrong. The anisotropy of shale depends significantly on the scale at which the problem is tackled (nano, micro or macroscale), suggesting that a multiscale model would be appropriate. Moreover, propagation of hydraulic fractures in such a complex medium can be difficult to model with current numerical discretisation methods. The crack propagation may not be unique, and crack branching can occur during the fracture extension. A number of natural fractures could exist in a shale deposit, so we are dealing with several cracks propagating at once over a considerable range of length scales. For all these reasons, the modelling of the fracking problem deserves considerable attention. The objective of this work is to present an overview of the hydraulic fracture of shale, introducing the most recent investigations concerning the anisotropy of shale rocks, then presenting some of the possible numerical methods that could be used to model the real fracking problem.

Sean Mulligan, John Casserly, R. Sherlock

B. Ghanbarian, A. Hunt, M. Sahimi et al.

郎喜白, 张胜华

Edith Gallagher, Heidi Wadman, Jesse McNinch et al.

Grain size on the surface of natural beaches has been observed to vary spatially and temporally with morphology and wave energy. The stratigraphy of the beach at Duck, North Carolina, USA was examined using 36 vibracores (~1–1.5 m long) collected along a cross-shore beach profile. Cores show that beach sediments are finer (~0.3 mm) and more uniform high up on the beach. Lower on the beach, with more swash and wave action, the sand is reworked, segregated by size, and deposited in layers and patches. At the deepest measurement sites in the swash (~−1.4 to −1.6 m NAVD88), which are constantly being reworked by the energetic shore break, there is a thick layer (60–80 cm) of very coarse sediment (~2 mm). Examination of two large trenches showed that continuous layers of coarse and fine sands comprise beach stratigraphy. Thicker coarse layers in the trenches (above mean sea level) are likely owing to storm erosion and storm surge elevating the shore break and swash, which act to sort the sediment. Those layers are buried as water level retreats, accretion occurs and the beach recovers from the storm. Thinner coarse layers likely represent similar processes acting on smaller temporal scales.

P. Bates, S. Lane, R. Ferguson

D. Savić, Z. Kapelan, P. Jonkergouw