Abstract:Cite Space software was used to analyze the research hotspots and frontier technologies of carbon neutrality technologies in water conservancy industry from 2011 to 2021, summarize the history and development trend of low carbon technologies in water conservancy industry, clarify the key role of the application of low carbon technologies in water conservancy industry to promote the transformation and upgrading of national energy structure, and study the development of low carbon technologies in water conservancy industry for the advantages of reducing carbon sources and increasing carbon sinks. It is pointed out that the common supporting technology, integration technology and utilization technology for carbon neutrality in the water conservancy industry are the three major research hotspots in the future. This study also analyzes the frontier technology of water conservancy industry in the process of achieving the “3060” goal, and foresees the future development direction of low-carbon frontier technology in the water conservancy industry and the urgent problems that need to be solved.

Abstract:To further understand the hydrogen and oxygen stable isotope composition differences between fog water and precipitation in different terrestrial systems and major influencing factors, the global-scale δ 2H and δ 18O research data for fog water and precipitation were collected and the significance of their differences was statistically analyzed. Combing the calculation of fog water’s lc-excess values, the isotopic difference rules between fog water and precipitation were classified, and corresponding causes and relations to fog types were further discussed and revealed. Results suggest that generally the fog water is significantly more enriched in heavier isotopes than the precipitation, with δ 2H and δ 18O differences of 10‰ to 60‰ and 1.2‰ to 5.5‰, respectively. The differences between fog and precipitation isotopic composition can be classified into three categories based on lc-excess values of fog water: the lc-excess value is approximately 0 and the fog water is within the 95% confidence interval of LMWL; the lc-excess value is greater than 0 and the fog water is distributed above the LMWL; the lc-excess value is less than 0 and the fog water is distributed below the LMWL. The water vapor source, condensation temperature and environmental temperature are three major factors that influence the isotopic difference between fog water and precipitation, with different categories correspondingly dominated by different factors. Orographic fog, radiation fog, and advection fog have different water vapor conditions and condensation processes, leading to different patterns of isotopic differ ences in fog and precipitation. There is no significant difference in the isotopic composition between terrain fog and precipitation, while there is a significant difference in the isotopic composition between radiation fog and precipitation, with significant enrichment of heavy isotopes in fog water. The overlap area of isotopic composition between advection fog and precipitation is small, and heavy isotopes in fog water are obviously more enriched.

Abstract:Aiming at the issues of over-fitting and limited generalization ability of classical U-Net model in extracting the flood retention area in the eastern foot of Helan Mountain, a new convolutional neural network model (WEU-Net) for the water body information extraction was proposed based on images of Sentinel-1 synthetic aperture radar(SAR) satellite and Sentinel-2 multispectral instrument(MSI) satellite.This model simplifies the network structure by reducing the number of convolutional kernels and the skip connection levels between encoder and decoder, and introduces residual blocks to enhance the feature extraction ability, which makes up the loss of image features due to the simplified model.In terms of data set, the Sentinel-1 water index was constructed by stepwise regression method combined with modified normalized difference water index (MNDWI), and the feature richness of data set from Sentinel-1 satellite was optimized.The main conclusions are as follows: the overall accuracy of the WEU-Net is 98.19% and the F1 score is 0.946 9, which are 0.357 7% and 0.948 8% higher than the classical U-Net model, respectively, and the training time is shortened by 49.30%; after fusing the sentinel-1 water index, the overall accuracy and F1 score were improved by 0.51% and 3.16%, respectively.

Abstract:To improve the accuracy of real-time flood forecasting in small and medium-sized basin in mountainous areas, a KNN real-time correction method based on the historical flood learning (KNN-H) was proposed and applied to two small basins in mountainous area in the Loess Plateau of Northern Shaanxi Province to test its performance. The proposed method was compared with the traditional KNN and AR methods. The results show that the correction accuracy of the KNN and KNN-H method is higher than that of the AR method and the traditional KNN and AR method cannot effectively reduce the peak time error of the forecasts, while the KNN-H method can reduce the peak time error. The correction accuracy of KNN is not high due to insufficient data in preheating period, while the KNN-H method effectively solves this problem by learning the historical flood forecast error. When the forecasted flood process is in the flood rising or falling stage, the KNN-H can locate the same stage of historical flood quickly and correct the current forecast value after analyzing the historical forecast error. In general, the correction accuracy of the KNN-H method is higher than that of the traditional KNN method.

Abstract:In this study, a two-dimensional numerical wave tank (NWT) was developed by solving the Navier-Stokes equations with the open-source CFD library OpenFOAM. The volume of fluid (VOF) method was adopted for the free surface capture and the k-ω SST model was used for the closure of governing equations. While the velocity profile method and the piston type wavemaker were tested separately for the wave generation, the artificial damping condition, Sommerfeld radiation condition and relaxation zone method were tested respectively to absorb the wave in the simulations of Stokes 2nd waves with different wave steepness ( i =0.01~0.06). According the comparisons between the numerical results and the analytical solutions, the performance of the model settings with different wave generation and absorption methods were analyzed. For the numerical simulations of 2nd order regular waves, the optimal setting is velocity profile method and relaxation zone method for cases with small wave steepness ( i =0.01~0.03), and the piston type wavemaker and the artificial damping condition with squared damping function for cases with large wave steepness ( i =0.04~0.06).

Abstract:To explore the effect of particle shape on the ultimate particle size distribution of carbonate sands under the condition of large shear strain, a series of ring shear tests and particle shape analyses were carried out on carbonate sands taken from the South China Sea using the ring shear apparatus and the Morphologi G3. The results show that an ultimate grading, as a result of the particle breakage, is reached after large shear strains in the ring shear apparatus. However, due to the more irregularity of the intact sands than the crushed sand, a significant breakage is induced when recreating a sample by mixing intact soil required for the ultimate size grading. As a result, the fractal dimension of the sample replaced with a different particle shape is bigger than that of the sample with the particle remolded.

Abstract:Aiming at the serious lack of rainfall-flood regime and safety monitoring, and the difficulty of hydrological forecast and risk assessment of reservoir safety in Guizhou Province, a supervision system is developed for the reservoir operation and safety monitoring of the whole province. Based on a Browser/Server architecture, the system used the WebGIS, GNSS and other technologies, and possesses both the functions of rainfall-flood forecasting and dam safety monitoring; with the collected history information and real-time data, the mining technology is pursued for further information identification and risk management. By providing the display modules of the overall function and typical projects, the system shows a strong performance for the dam safety monitoring and rainfall-flood forecasting ability, can facilitate the capability of flood forecast and disaster defense in Guizhou province, and thus provides technical support for the safe operation and intelligent management of reservoirs.

Abstract:In order to study the structure types and deformation characteristics of prefabricated invert arch structure in highway tunnels, firstly, by collecting application cases of different prefabricated tunnel structures at home and abroad. Then, the precast inverted arch structure of the drilling-blasting highway tunnel is optimized and its stress characteristics are studied. According to the section characteristics of the drilling-blasting highway tunnel, taking a highway tunnel project in Gansu Province as an example, the prefabricated invert type of arc-shape and box-shape was designed from the aspects of construction difficulty, construction speed, anti-drainage ability and cost. The influence of the number of invert arch blocks, invert arch thickness and width on the maximum displacement, concrete damage and reinforcement stress of prefabricated box invert structures are analyzed. The results show that the box-type precast invert is a more suitable structure. The box prefabricated invert structure with 7 blocks, upper thickness of 20.cm, lower thickness of 40.cm and width of 1.2 m is the most suitable. The assembled invert structure and the secondary lining structure adjust and improve the tunnel load, and play a significant role in ensuring the stability of the overall supporting structure.

Abstract:In order to solve the problem of reusing a large amount of rock slag when the slurry shield passes through the weathered rock stratum, relying on the Nanjing Heyan road crossing-river project, the rock slag is used to replace part of commercial sand to prepare the synchronous grouting slurry. The fluidity, consistency, setting time, bleeding rate and strength of the slurry are tested through laboratory tests, and the performance and micro morphology of shield synchronous grouting slurry made of weathered rock slag are analyzed. The results show that: with the increase of the proportion of rock slag replacing commercial sand (denote as the replacing ratio), the fluidity, consistency and bleeding rate of the slurry decrease, while the setting time shows a decreasing trend, and the compressive strength gradually increases after 1 day. When the replacing ratio is 50% to 85%, all properties of the slurry can meet the requirements of engineering construction; when the replacing ratio of rock slag is 85%, the fluidity and consistency of the slurry are close to those of the on-site slurry, the setting time is shortened from 10.6.h to 7.3.h, and the 1-day compressive strength is nearly doubled. Kaolinite phase minerals contained in the rock slag will electrolyze Al3+ in water, which promotes the formation of C-S-H gel in the slurry, and is the fundamental reason for shortening the setting time of the slurry and increasing the compressive strength of the slurry.

Abstract:To study the nonlinear correlation between strata parameters, shield tunneling parameters and ground settlement, an ABC-BP neural network model that can predict the ground settlement was established by using the artificial bee colony (ABC) algorithm and BP neural network based on the shield interval of Nanjing Metro Line 6. This model was validated through three consecutive sections of the shield. The results show that the prediction accuracy and prediction stability of ABC-BP model are better than BP model, and the predicted value is consistent with the real value. The model can accurately reflect the evolution law of ground deformation during the shield machine approaching the monitoring section and achieve the purpose of final ground deformation control. This study proposes the on-site application concept of ABC-BP neural network, constructs the relationship between strata parameters, excavation parameters and settlement, and can directly control shield tunneling parameters and ground deformation through strata parameters.

Abstract:In order to promote the application of the reverse self-balanced pile test method in the practice engineering, the numerical simulation analysis of the reversed self-balanced pile test method is carried out by using the finite element analysis method. Taking the pipe pile as an example, the numerical model of reverse self-balanced test pile method is established by the ABAQUS software. The displacement control method and load control method are used to simulate the loading of pile body and pile top, and the ultimate compressive bearing capacity of the foundation pile is obtained, from which the pile axial force and the pile lateral friction resistance can be analyzed. The established numerical model is modeled by the static load test with the displacement control method and compared with the ultimate bearing capacity simulated by the reverse self-balance test method. The simulation results show that the ultimate bearing capacity of foundation pile determined by the reverse self-balance test method is relatively close to the result of the static load test method, and the conversion of positive and negative friction resistance is not necessary, but there is also the problem of determining the position of the balance point.

Abstract:To understand the influence of the excess pore pressure around the pile and at the pile end in layered cohesive soils after pile sinking on the soil compaction effect of pile driving, by using in-situ tests and numerical simulation methods, the spatiotemporal distribution characteristic of the excess pore pressure at the pile-soil interface and the variation law of the overlying vertical effective stress with time were analyzed. On the basis of the hydraulic fracturing theory and the cavity expansion theory, the modified Cam-clay model was introduced to derive the modified formula for calculating the overlying vertical effective stress and excess pore pressure at the pile-soil interface during the consolidation of soil around the pile. The results show that from the point of view of time, the excess pore pressure dissipates with time and the overlying vertical effective stress increases gradually under the external load of the pile top; After 30 days of pile formation, the excess pore pressure has basically dissipated, the overlying vertical effective stress no longer increases, and the foundation soil is in a resting period. From the point of view of space, the excess pore pressure increases with the increase of pile burial depth, and it increases faster in the clay layer with poor permeability; Under different load conditions, the smaller the horizontal distance from the pile center and the vertical distance from the pile end, the greater the excess pore pressure; The maximum excess pore pressure near the pile end and pile center is negatively related to the pile top load.

Abstract:In order to study the hydrodynamic response characteristics and anti-rocking measures of large floating bodies in the waters of Maldives, a numerical model of hydrodynamic response of floating tanks is established based on the three-dimensional potential flow theory and the rigid-body motion equation, the hydrodynamic response characteristics of floating tanks with different aspect ratios are analyzed, the influence of anti-shake plate layout and type on the anti-rocking effect of floating tanks is discussed, and a better layout scheme of anti-shake plates is given on this basis. The results show that the rectangular floating box with an aspect ratio of 2∶1 has a relatively stable motion response in each wave. The width of the anti-shake plate has an obvious control effect on the floating box, and when the anti-shake plate is installed at the same time on the floating box and the back wave surface, the anti-rocking effect is significantly affected by the installation height. For the double-layer open-hole anti-rocking plate on the facing side, when the opening of the upper anti-shake plate is 40%, the control over the rocking of the floating box is better, and the rollover of the floating box can be reduced by 16.9% under the limit sea state. This study recommends the single-sided double-layer anti-rocking plate layout form with the opening of the upper layer. The installation of the anti-shake plate has little effect on the strength of the floating structure under the action of waves, and attention should be paid to the connection strength of the anti-shake plate and the shell.

Abstract:To study the joint distribution of annual extreme wave height and annual extreme period of waves in the central Yellow Sea, five univariate distributions were fitted to the annual extreme wave height and annual extreme period based on SWAN hindcast wave data from 1999 to 2018 at three locations in the Yellow Sea, and the optimal marginal distributions of annual extreme wave height and annual extreme period at each location were obtained through the evaluation of the goodness of fit. The joint distribution function of annual extreme wave height and annual extreme period was established using the Copula function theory, and compared with the univariate distribution of wave height and period design values. The results show that there may be regional characteristics in the joint wave height and period distribution in the central Yellow Sea; the design values of wave height and period obtained from the joint wave height and period distribution are higher than the design values of univariate distribution at the same design frequency; under the same design frequency, the univariate return period is the largest, the conditional return period is the second and the joint return period is the smallest.

Abstract:Based on the automatic dynamic analysis of mechanical systems (ADAMS), a virtual prototype of a multi-body collaborative operation system for the twin-ship joint lifting in specific scenarios is constructed to predict and evaluate the roll stability of the blocks to be removed during the new integrated dismantling operation of twin-ship joint lifting. The topological model of the system is constructed, and geometric parameters are used to describe the rolling motion characteristics of the topside in the system. Through the virtual prototype simulation, the most dangerous instability state of topside under different coupling motions of two vessels is explored, and the influence law of the ratio of vertical distance and horizontal distance from the center of gravity of topside to the connection point on the rolling angle is given. The results show that the test data-driven virtual prototype technology can effectively evaluate the motion characteristics of the topside in the complex multi-body system, which is consistent with the theoretical formula of the rolling instability angle of the topside obtained from the geometric topology model. The coupling motion of the two vessels at the same phase rolling and anti-phase heave has the greatest influence on the rolling stability of the topside. The ultimate aspect ratio of the topside obtained by the virtual prototype simulation can be used as the rolling stability evaluation parameters of the multi-body system, and provide a reference for the selection of engineering schemes.

Abstract:In order to improve the recognition accuracy of the underwater riprap, the physical model and resistivity tomography model of the riprap with internal cavities are established. The performance of resistivity tomography technology in the detection of internal cavities inside the underwater riprap is studied and compared with the traditional Kriging interpolation. The results show that the resistivity tomography can effectively identify the internal cavity in the underwater riprap and the inversion accuracy reaches a higher value when the number of stimulation points increases to 6. The identification ability of the resistivity tomography on the longitudinal section of channel is much higher than that of the traditional Kriging method. Meanwhile, if the region with conductivity greater than 300.μS/cm in inversion results is regarded as a cavity region, the overall inversion results are slightly larger than the real situation, and the deviations in the three directions of x、y、z are 2.73, 1.75, and 6.95.cm, respectively. Based on the inversion results, the forward calculation of the resistivity tomography model is carried out. It can be found that the fitting degree between the forward modeling and the measured data was 0.95, which proved the accuracy of the resistivity tomography inversion.